Download Lecture Exam 3

Final Exam Study Guide – Chapters 21-26
Your final will be a take-home exam consisting of multiple choice and case study questions. Major microbes to review have been
summarized in the sections of the following overviews. Concerning conditions/diseases discussed in class, make sure that you are
familiar with the following: etiology, diagnostic methodologies, means of transmission, and treatment. The expectation is that the
exam is to be completed individually using textbook and notes (including this study guide); evidence of collaboration and/or
plagiarism will result in a zero.
Introduction to Skin & Soft Tissue Infections (Chapter 21)
The resistance of skin to infection is due to the integrity of the keratinized skin, the presence of inhibitory fatty acids produced by
sebaceous glands, the dryness of the skin, and the inhibitory effect of the resident normal skin flora. Skin and soft tissue infections
can be caused by either direct penetration of a pathogen through the skin or hematogenous spread of the pathogen to the site. Normal
skin flora includes organisms that, in the setting of a disruption in the integrity of the skin (such as the presence of a surgical suture or
an insect bite), may cause infection. In the setting of severe damage to the skin, as occurs with burns, even normally innocuous
organisms, including endogenous bacteria, can cause severe disease. Similarly, when the skin is no longer dry, as may occur in moist
intertriginous spaces or when occlusive dressings are present, the patient is at increased risk of infection.
Cutaneous manifestations of systemic disease are common. Rocky Mountain spotted fever, meningococcemia, enteroviral infection,
and toxic shock syndrome can all present with fever and a diffuse erythematous macular rash. Other systemic infections that can
present with a diffuse rash include scarlet fever, measles, and German measles. The characteristic rash of Lyme disease, erythema
migrans, is specific enough to establish the diagnosis. The nature of the lesion (macular, papular, vesicular, pustular, or bullous) may
help to narrow the differential diagnosis. For example, varicella-zoster virus infection typically results in vesicular skin lesions. The
rash of secondary syphilis, on the other hand, may present clinically as macular, papular, maculopapular, or pustular skin lesions but
does not present as a vesicular rash.
Skin and soft tissue infections can be classified on the basis of the anatomic level at which infection occurs. The more superficial
infections, such as folliculitis caused by Staphylococcus aureus or cellulitis caused by Streptococcus pyogenes, are important to treat
at an early stage. Delay in treatment may result in invasion of the deeper structures, as in necrotizing fasciitis, which has a high
mortality rate.
Damage to the skin and soft tissues, as occurs in traumatic injuries, may allow the entry into the wound of soil organisms such as
Clostridium perfringens, an anaerobic gram-positive rod. Under favorable conditions, potentially fatal soft tissue infections (myositis,
gas gangrene) may occur.
Skin & Soft Tissue Pathogens
Organism
Bacteria
Bartonella henselae
General Characteristics
Infection Source
Disease Manifestation
Fastidious gram-negative
bacillus
Cat scratch disease, bacillary angiomatosis (in immunocompromised
individuals)
Borrelia burgdorferi
Clostridium perfringens
Spirochete
Anaerobic gram-positive
bacillus
Clostridium tetani
Anaerobic gram-positive
bacillus
Exogenous; cats
appear to be
primary host
Tick bome
Exogenous
(wounds),
endogenous
(bowel flora)
Exogenous
(wounds)
Corynebacterium diphtheriae
Aerobic gram-positive
bacillus
Exogenous
Diphtheria (pharyngeal) and wound Diphtheria
Group A streptococci
(Streptococcus pyogenes)
Group B streptococci
(Streptococcus agalactiae)
Neisseria gonorrhoeae
Catalase-negative, grampositive cocci
Oxidase-positive, gramnegative diplpcoccus
Oxidase-positive, gramnegative diplococcus
Endogenous
Endogenous
Cellulitis, bacteremia, scarlet fever, necrotizing fasciitis, pharyngitis,
pneumonia, poststreptococcal glomerulonephritis and rheumatic fever
Cellulitis, sepsis, meningitis
Sexually
transmitted
Genital tract involvement, pharyngeal infection, ocular infection,
bacteremia, arthritis with dermatitis
Lyme disease; rash, arthritis, nervous system and cardiac manifestations
Gas gangrene, emphysematous cholecystitis, bacteremia, food
poisoning
Tetanus
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Organism
Neisseria meningitidis
Pasteurella multocida
Pseudomonas aeruginosa
Staphylococcus aureus
Treponema pallidum
Fungi
Blastomyces dermatitidis
Candida albicans
Candida spp., non-albicans
Cryptococcus neoformans
Epidermophyton floccosum
Microsporum spp.
General Characteristics
Oxidase-positive, gramnegative diplococcus
Oxidase-positive, gramnegative bacillus
Infection Source
Endogenous (from
colonization)
Zoonosis (often
animal bite or
scratch)
Exogenous
Disease Manifestation
Meningitis, bacteremia
Endogenous
Cellulitis, bacteremia, endocarditis, septic arthritis, abscesses
Direct sexual
contact, vertical
(mother to child)
Primary (painless chancre), secondary (diffuse rash), latent, and late
syphilis; can affect any organ
Dimorphic mold
Yeast, often germ tube
positive
Yeasts, germ tube negative
Exogenous
Endogenous
Encapsulated yeast
KOH-positive skin lesions;
clubshaped macroconidia,
absent microconidia
KOH-positive skin lesions;
fluoresces yellow-green
under Wood's light
Exogenous
Anthropophilic
Cutaneous infection, pneumonia, meningitis, bone infection
Thrush, vaginal yeast infection, diaper rash, esophagitis, nosocomial
UTI, nosocomial bloodstream infection
Thrush, vaginal yeast infection, nosocomial UTI, nosocomial
bloodstream infection
Meningitis, pneumonia, bloodstream
infection, cellulites
Dermatophyte infection of keratinized tissue (rarely nails)
Lactose-nonfermenting,
oxidase positive, gramnegative bacillus
Catalase-positive,
coagulase positive, grampositive coccus
Spirochete (does not Gram
stain)
Trichophyton spp.
KOH-positive skin lesions
Parasites
Ancylostoma brazi/iense
Ancylostoma caninum
Leishmania tropica
Pediculus spp.
Hookworm of dog
Hookworm of dog
Protozoan
Ectoparasite
Phthirus pubis
Sarcoptes scabei
Viruses
Erythrovirus B19
Herpes simplex virus
Ectoparasite
Ectoparasite
Human herpesvirus type 6
Human immunodefi.
ciency virus (HIV)
Enveloped, dsDNA
Enveloped RNA retrovirus
Rubella virus (German
measles)
Rubeola virus (measles)
Enveloped, ssRNA
Papillomavirus
Varicella-zoster virus
Nonenveloped, dsDNA
Enveloped, dsDNA
Nonenveloped, ssDNA
Enveloped, dsDNA
Enveloped, ssRNA
Endogenous
Cellulitis, bacteremia, osteomyelitis, meningitis
Skin infections in burn patients, community and nosocomial UTl’s,
nosocomial pneumonia, nosocomial bacteremia, ecthyma gangrenosum
May be zoophilic
(e.g., M. canis),
geophilic (e.g., M.
gypseum), or
anthropophilic
(e.g., M. audouinil)
May be zoophilic
(e.g., T.
mentagrophytes) or
anthropophilic
(e.g., T. schoenleinil)
Dermatophyte infection of keratinized tissue (rarely nails)
Exogenous
Exogenous
Exogenous
Exogenous (sand
fly)
Exogenous
Exogenous
Cutaneous larva migrans
Cutaneous larva migrans
Ulcerative skin lesions
Body lice
Person to person
Person to person;
reactivation of
latent infection;
during passage of
the neonate
through the birth
canal
Person to person
Bloodborne and
sexual
transmission
Vertical, mother
to child
Respiratory
spread
Person to person
Respiratory
spread
Erythema infectiousum; anemia
Genital ulcers; oral, ocular infections; encephalitis; neonatal infection;
esophagitis (immunocompromised individuals)
Dermatophyte infection of keratinized tissue including nails
Crab louse
Scabies infestation
Exanthem subitum (roseola)
AIDS, mononucleosis-like syndrome with rash in primary infection
Inapparent or subclinical infection in
adults; birth defects in
infants
Measles; pneumonia, encephalomyelitis, subacute sclerosing
panencephalitis
Warts
Chicken pox; zoster (may disseminate)
Introduction to Central Nervous System Infections (Chapter 22)
Infections of the central nervous system (CNS) are infrequent compared to the other infections discussed for other organ systems of
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the human body, but they are very important because of the high mortality rates and the serious sequelae associated with them,
including learning, speech, and motor skills disorders, seizures, and hearing and sight loss. The most frequent CNS infections are
meningitis, encephalitis, and abscess. Intoxication with tetanus and botulinum toxins can affect the CNS, causing spastic or flaccid
paralysis, but these diseases are quite rare in the developed world.
There are two major forms of meningitis, septic and aseptic. Septic meningitis is typically caused by bacteria. The cerebrospinal fluid
(CSF) is usually cloudy, with over 1,000 white blood cells per L with neutrophils predominating; increased protein levels due to
inflammation; and decreased glucose due in part to metabolism by white blood cells. Aseptic meningitis can be caused by viruses,
fungi, or Mycobacterium tuberculosis. In aseptic meningitis, the CSF is "clear" due to a cell count typically in the 100-500/l range.
Except very early in the disease course, the predominant cell type is mononuclear, with lymphocytes predominating. CSF glucose
levels are frequently normal, but they may be decreased in over half of patients with fungal or mycobacterial infections. CSF protein
levels are frequently normal except with M. tuberculosis, where they are typically elevated.
Bacterial meningitis is most common in the very young, the very old, and the immunocompromised; of these, it is seen most
commonly in children 2 months to 5 years of age. Group B streptococci are the most common cause of neonatal meningitis (newborns
to 2 months). Listeria monocytogenes is another organism that causes neonatal disease. It also is an important agent of meningitis in
the immunosuppressed. Gram-negative enteric bacilli, including Escherichia coli, Klebsiella pneumoniae, and Citrobacter diversus,
may also cause neonatal meningitis. Congenital syphilis, which may manifest itself during the neonatal period, frequently will have a
CNS component, neurosyphilis. Until recently, Haemophilus influenzae type b was the most common cause of bacterial meningitis in
children 2 months to 5 years of age, but the widespread use of conjugated H. influenzae type b vaccine has resulted in a dramatic
decline in the incidence of this disease. Streptococcus pneumoniae and Neisseria meningitidis are now the leading causes of
meningitis in this age group and the elderly.
Individuals with head trauma are also at risk for developing bacterial meningitis. The organisms most frequently associated with this
type of bacterial meningitis are coagulase-negative staphylococci (especially in patients with CNS shunts or who have undergone
neurosurgical procedures), Staphylococcus aureus, and Pseudomonas aeruginosa. M. tuberculosis meningitis is seen primarily in
children and the immunosuppressed.
Viral meningitis is typically caused by enteroviruses other than poliovirus. It is seen primarily in the summer months in infants and
young children. Herpes simplex virus can cause a typically benign meningitis associated with primary genital tract infections. This is
not to be confused with herpes simplex encephalitis, as discussed below.
Encephalitis is due primarily to viruses. Herpes simplex virus causes probably the most common form of viral encephalitis
encountered in the developed world. It can occur in neonates and during reactivation of latent infection in adults. This form of herpes
infection can produce necrotic lesions in the brain, resulting in long-term sequelae or death. Insect-borne viruses such as Eastern
equine, Western equine, St. Louis, and La Crosse encephalitis viruses are encountered in the United States. In many states in the
eastern United States, an epidemic of rabies in animals is occurring. It is only a matter of time before human cases are reported.
Fungal meningitis is seen primarily but not exclusively in the immunocompromised. It is of particular importance in AIDS patients,
with Cryptococcus neoformans being far and away the most important cause of CNS infection in this patient population.
Parasites may also cause CNS infection. The most frequently encountered parasite causing CNS infections in the developed world is
Toxoplasma gondii. These infections occur primarily in AIDS patients and represent reactivation of latent infections. In the
developing world, one of the most common causes of a clinical presentation of meningitis/encephalitis is cerebral malaria. A major
cause of adult onset of seizures in certain areas of the developing world where pork is a source of protein in the diet is cysticercosis.
This disease occurs when eggs of the pork tapeworm Taenia solium are ingested. The parasite is unable to complete its life cycle, and
cyst-like lesions occur throughout the body including the brain. An amoeba, Naegleria fowleri, causes a rare, fatal form of
meningoencephalitis. It is found in individuals living in temperate regions who swim in warm fresh water during the summer months.
Brain abscesses occur either through direct extension from a contiguous site, following trauma, or by hematogenous spread from
another infected site. Typically, patients with abscesses due to hematogenous spread have either endocarditis or a lung abscess. Septic
emboli, which are small blood clots containing infectious agents, are released from the primary infection site and enter the
bloodstream. The embolus lodges in a capillary in the brain, causing a localized hemorrhage and producing a site for the initiation of
infection which evolves into a brain abscess. The organisms most frequently causing abscesses in immunocompetent individuals are
either S. aureus or organisms usually found in the oropharynx including the viridans group streptococci, Actinomyces spp., and
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anaerobic bacteria. In immunocompromised individuals, Aspergillus, Mucor, Rhizopus, and Nocardia spp. can cause brain abscess. In
trauma patients, S. aureus and gram-negative rods are frequently seen. In diabetic patients, rhinocerebral mucormycosis can extend
from the sinuses into the brain, causing extensive necrosis.
Nervous System Pathogens
Organism
Bacteria
Actinomyces spp.
Citrobacter diversus
Clostridium
botulinum
Clostridium tetani
Coagulase-negative
staphylococci
Escherichia coli
Group B
streptococci
(Streptococcus
agalactiae)
Haemophilus
influenzae type b
Listeria
monocytogenes
Mycobacterium
tuberculosis
Neisseria meningitidis
Nocardia spp.
Oral streptococci
(5. sanguis, S. mutans,
etc.)
Prevotella sp.,
Porphyromonas sp.
Pseudomonas
aeruginosa
Staphylococcus aureus
Streptococcus
pneumoniae
Fungi
Aspergillus spp.
Cryptococcus
neoformans
Mucor sp., Rhizopus
sp.
Parasites.
General characteristics
Patient population
Disease manifestation
Individuals with aspiration pneumonia
Brain abscess
Neonates
Meningoencephalitis with abscess
Infants, adults who ingest botulinum
toxin
Botulism, flaccid paralysis
Any, often associated with deep tissue
wound
Tetanus, spastic paralysis
Individuals with foreign bodies, e.g.,
shunts or bolts
Meningitis
Neonates
Meningitis
Neonates, immunocompromised adults
Meningitis
Unvaccinated children
Meningitis
Neonates, immunocompromised adults
Meningitis
Acid-fast bacillus
Children; patients with AIDS
Tuberculous Meningitis
Oxidase-positive, gramnegative diplococcus
Aerobic, partially acidfast branching bacilli
All ages; outbreaks in college students
& military
Meningitis
Individuals with pulmonary nocardiosis
Brain abscess
Individuals with aspiration pneumonia
Brain abscess
Individuals with aspiration pneumonia
Brain abscess
Branching, gram-positive
bacilli, usually anaerobic
Enteric gram-negative
bacillus
Toxin-producing,
anaerobic, gram-positive
bacillus
Toxin-producing,
anaerobic, gram-positive
bacillus
Catalase-positive, grampositive cocci
Lactose-fermenting,
gram-negative bacillus
Catalase-negative, grampositive cocci
Gram-negative,
pleiomorphic bacillus
Catalase-positive, grampositive coccobacillus
Alpha-hemolytic, grampositive cocci
Anaerobic, gram-negative
bacilli
Oxidase-positive, gramnegative bacillus
Catalase-positive, grampositive cocci
Catalase-negative, grampositive cocci
Acute-angle, septate
hyphae in tissue
Encapsulated, round
yeast
Ribbon-like, aseptate
hyphae in tissue
Acanthamoeba sp
Amoeba
Naegleria fowleri
Amoeba
Individuals with head trauma or foreign
bodies
Individuals with head trauma or foreign
bodies
Meningitis
Meningitis
Primarily young children and elderly
Meningitis
Immunocompromised with invasive
aspergillosis
Brain abscess
Immunocompromised, especially AIDS
Meningitis
Diabetics, immunocompromised
individuals
Necrotizing encephalitis,
rhinocerebral mucormycosis
Immunocompromised or
immunocompetent
Individuals with exposure to warm,
fresh water
Granulomatous amebic encephalitis
or keratitis
Fatal amebic meningoencephalitis
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Organism
Plasmodium
falciparum
General characteristics
Delicate, ring forms in
blood
Patient population
Individuals who visit malaria-endemic
areas
Taenia solium
larval cyst
Individuals who ingest T. solium eggs
Seizures, calcified lesions in brain or
muscle
Toxoplasma gondii
large cysts in tissue
Immunocompromised, especially AIDS
patients
Encephalitis, abscess
Viruses
Echovirus/
coxsackievirus
Encephalitis
viruses
Nonenveloped ssRNA
Both enveloped and non
enveloped ssRNA
Herpes simplex
virus
Enveloped dsDNA
Human
immunodeficiency
virus (HIV)
Enveloped retrovirus
Poliovirus
Nonenveloped ssRNA
Rabies virus
Enveloped ssRNA
Children and adults during summer
months
Children and adults bitten by viral
arthropod vector
Neonates, individuals with primary
genital herpes, individuals with primary
or recurrent herpes infections
AIDS
Nonvaccinated individuals; live, attenuated vaccine, especially in the
immunocompromised
Individuals bitten or scratched by
nonvaccinated, rabid dog, cat, or other
mammal
Disease manifestation
Cerebral malaria
Aseptic meningitis
Encephalitis, frequently fatal
Necrotizing encephalitis; benign,
aseptic meningitis; necrotizing
hemorrhagic encephalitis
AIDS-associated dementia;
predisposes to other CNS'
infections
Polio paralysis
Rabies
Introduction to Respiratory Diseases (Chapter 24)
Respiratory tract infections are a major reason why children and the elderly seek medical care. These infections are more common in
cold-weather months in locales with temperate climates. Respiratory tract infections are primarily spread by inhalation of aerosolized
respiratory secretions from infected hosts. Some respiratory tract pathogens such as rhinoviruses can also be spread by direct contact
with mucous membranes, but this mode of transmission is much less common than inhalation. For the purpose of our discussion, we
will divide these types of infection into two groups, upper tract and lower tract infection.
The most common form of upper respiratory tract infection is pharyngitis. Pharyngitis is seen most frequently in children from 2 years
of age through adolescence. The most common etiologic agents of pharyngitis are viruses, particularly adenoviruses, and group A
streptococci. Pharyngitis due to group A streptococci predisposes individuals to the development of the poststreptococcal sequela
rheumatic fever. Because this sequela can be prevented by penicillin treatment, aggressive diagnosis and treatment of group A
streptococcal pharyngitis is needed.
Otitis media is a common infectious problem in infants and young children. The most frequently encountered agents of this infection
are bacterial, with Streptococcus pneumoniae, non-typeable Haemophilus influenzae, and Moraxella catarrhalis being most common.
These organisms, along with certain viruses and anaerobic bacteria from the oral cavity, are the most important pathogens in sinusitis.
S. pneumoniae, H. influenzae, Moraxella catarrhalis, and adenoviruses, as well as Chlamydia trachomtis in neonates, are the common
etiologic agents of conjunctivitis. External otitis, a common problem in swimmers, is more common in warm weather months.
Staphylococcus aureus and Pseudomonas aeruginosa are the most common agents of this relatively benign condition. Malignant
external otitis is a serious medical condition seen primarily in diabetics, the elderly, and the immunocompromised. The infection can
spread from the ear to the temporal bone, resulting in osteomyelitis and meningitis. The most common etiology of malignant otitis
externa is P. aeruginosa.
Two other life-threatening infections of the upper respiratory tract are rhinocerebral mucormycosis and bacterial epiglottitis.
Rhinocerebral mucormycosis is most common in diabetics. In this infection of the sinuses, the fungi Mucor and Rhizopus spp. invade
blood vessels, resulting in necrosis of bone and thrombosis of the cavernous sinus and internal carotid artery. Treatment of this
infection requires aggressive surgical debridement of the infected tissue. Epiglottitis is almost always caused by H. influenzae type b.
In this disease, the airway may become compromised due to swelling of the epiglottis, with death due to respiratory arrest. With the
widespread use of H. influenzae type b vaccine, this rare disease should essentially disappear.
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Organism
General
Characteristics
Patient Population
Disease Manifestation
Bacteria
Two childhood infections common in the early part of the 20th century, diphtheria and whooping cough, are now rare diseases in the
developed world. This is thanks to the development and use of vaccines that are effective in children against the etiologic agents of
these diseases, Cornyebacterium diphtheriae and Bordetella pertussis.
Viruses play an important role in upper respiratory tract infections. The common syndrome of cough and "runny" nose is due to
rhinoviruses. More severe upper respiratory infections such as the "croup" are due to respiratory syncytial virus and influenza and
parainfluenza viruses. These viruses can also cause lower tract infection and are an important cause of morbidity and mortality in the
very young and very old.
When discussing lower respiratory tract infections, it is important to look at four different groups of patients: patients with
community-acquired infections; patients with nosocomial infections; patients with underlying lung disease; and immunocompromised
individuals, especially those with AIDS.
Common agents of community-acquired lower respiratory tract infections include pneumoniae, especially in the elderly; Klebsiella
pneumoniae, especially in alcoholics; Mycoplasma pneumoniae, especially in school-age students through young adulthood;
Mycobacterium tuberculosis; respiratory syncytial virus in infants and young children; and influenza virus. Histoplasma capsulatum
and Coccidioides immtis in patients residing in specific geographic locales may cause mild, self-limited diseases. S. pneumoniae, H.
influenzae, S. aureus, and Moraxella catarrhalis may specifically cause bronchitis and/or pneumonia secondary to viral pneumonia in
adults. Aspiration, resulting from either a seizure disorder or a semiconscious state resulting from excessive consumption of alcohol or
other drugs, may lead to lung abscesses caused by organisms typically residing in the oral cavity.
Nosocomial infections due to the organisms listed above certainly occur. Particular emphasis should be placed on preventing the
spread of Mycobacterium tuberculosis in all patient populations and of respiratory syncytial virus in pediatric patients. Nosocomial
pneumonia due to methicillin-resistant S. aureus and multi-drug-resistant gram-negative bacilli such as P. aeruginosa is a common
problem in intubated patients. The potential for outbreaks of pneumonia due to Legionella spp. is a constant threat because of this
bacterium's ability to survive within hospital water and air conditioning systems.
Patients with chronic obstructive pulmonary disease brought on by smoking frequently develop bronchitis. S. pneumoniae, Moraxella
catarrhalis, H. influenzae, and P. aeruginosa are frequent causes of this type of infection. Chronic airway infections are primarily
responsible for the premature death of patients with cystic fibrosis. S. aureus and mucoid P. aeruginosa are the most important agents
of such chronic airway disease. Both of these patient populations have an increased risk for developing allergic bronchopulmonary
aspergillosis. Patients with cavitary lung disease, frequently due to prior Mycobacterium tuberculosis infection, are at increased risk
for another type of infection, an aspergilloma or fungus ball caused by Aspergillus spp. This fungus grows in the form of a "ball" in
the preformed lung cavity.
The diagnosis of the etiology of lung infection in immunocompromised patients one of the most daunting in clinical microbiology and
infectious disease. It has been greatly facilitated by the development of the flexible bronchoscope, which provides a relatively
noninvasive means to sample the airways and alveoli. Immunocompromised patients are typically at risk for essentially all recognized
respiratory tract pathogens. Certain pathogens are seen with increasing frequency in selected immunocompromised populations. In
AIDS patients, Pneumocystis carinii, 5. pneumoniae, and multi-drug-resistant Mycobacterium tuberculosis are all seen more
frequently than in other patient populations. Profoundly neutropenic patients have a very high risk for invasive aspergillosis and
mucormycosis. Transplant patients have greatly increased risk for pneumonia with cytomegalovirus, herpes simplex virus, Legionella
spp., Pneumocystis carinii, and the invasive fungi. These patients are frequently given prophylactic drugs to prevent pulmonary
infection with Pneumocystis. Prophylactic therapies are not as widely used for other agents for a variety of reasons, including expense,
questionable efficacy of the prophylactic measures, or the rarity with which the organism is encountered.
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Neisseria meningitidis
Nocardia spp.
Nontuberculous
mycobacteria (many species)
Prevotella sp.; Porphyromonas
spp
Pseudomonas aeruginosa
Oxidase-positive,
gram-negative
diplococcus
Partially acid-fast,
aerobic, branching,
gram-positive bacilli
Acid-fast bacilli
Anaerobic gramnegative bacilli
Glucosenonfermenting, gramnegative bacillus
Adults
Pneumonia
Adults, especially with
immunosuppression
Pneumonia with abscess
Adults with chronic lung
disease; CF patients
Adults with aspiration
Granulomatous lung disease
Adults and children; diabetic
adults; nosocomial; CF patients
Lung abscess
Catalase-positive,
gram-positive cocci in
clusters
Glucosenonfermenting, gramnegative bacillus
Catalase-negative,
gram-positive
diplococcus
Acid-fast bacillus
Nosocomial
External otitis (swimmer's ear), malignant
external otitis, ventilator-associated
pneumonia, chronic bronchitis with mucoid
strains
Pneumonia, pneumonia superinfections
Nosocomial
Ventilator-associated pneumonia
Children and adults
Otitis media, conjunctivitis, pneumonia
Children and adults, especially
HIV-infected
Tuberculosis
Acute-anglebranching, septate
hyphae in tissue; mold
Children and adults with chronic
lung disease; adults with
cavitary lung lesions;
immunocompromised individuals
Adults
Allergic bronchopulmonary aspergillosis;
aspergilloma (fungus ball); invasive pneumonia
Children and adults, especially in
desert southwest of US and
northern Mexico
Immunocompromised adults,
especially with AIDS
Adults, primarily with AIDS,
spread through bat/bird
droppings
Immunocompromised individuals,
especially with AIDS
Flu-like illness with pneumonia
Diabetics, immunocompromised
individuals
Rhinocerebral mucormycosis, invasive
pneumonia
Larvae
Larvae
Rhabditiform larvae
Children and adults
Children and adults
Immunocompromised individuals
Usually asymptomatic, incidental finding
Usually asymptomatic, incidental finding
Wheezing, cough, pneumonia
Enveloped, dsDNA
Children and adults
Cytomegalovirus
Hantavirus
Herpes simplex virus
Influenza virus
Enveloped, dsDNA
Enveloped, ssRNA
Enveloped, dsDNA
Enveloped, ssRNA
Parainfluenza virus types I,
II, III
Enveloped, ssRNA
Immunocompromised individuals
Children and adults
Immunocompromised individuals
Children and adults, particularly
elderly
Infants and young children
Pharyngitis, bronchiolitis, pneumonia,
conjunctivitis
Pneumonia
"Shock" lung, pneumonia
Pneumonia
Influenza, pneumonia
Staphylococcus aureus
Stenotrophomonas
maltophilia
Streptococcus pneumoniae
Mycobacterium tuberculosis
Fungi
Aspergillus spp.
Blastomyces dermatitidis
Coccidioides immitis
Cryptococcus neoformans
Histoplasma capsulatum
Pneumocystis carinii
Rhizopus sp., Mucor sp.
Parasites
Ascaris lumbricoides
Hookworm
Strongyloides stercoralis
Viruses
Adenovirus
Broad-based budding
yeast; dimorphic
Spherules in tissue;
mold with
arthroconidia at 30.C
Encapsulated, round
yeast
Very small,
intracellular yeast;
dimorphic
Clusters of 4-6-l1m
cysts in tissue and
secretions
Ribbon-like,
nonseptate hyphae in
tissue; rapidly growing
mold
Pneumonia
Pneumonia, often asymptomatic preceding
meningitis
Pneumonia
Pneumonia
Croup, bronchiolitis, pneumonia
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Respiratory syncytial virus
Rhinovirus
Varicella-zoster virus
Enveloped, ssRNA
Nonenveloped, ssRNA
Enveloped, dsDNA
Infants and young children
Children and adults
Immunocompromised individuals,
pregnant women
Cough, wheezing, bronchiolitis, pneumonia
Common cold
Pneumonia
Introduction to Cardiovascular & Systemic Diseases (Chapter 23)
Systemic infections can be caused by many different infectious agents: bacterial, fungal, viral, and parasitic. One common finding for
all systemic infections is the need for a portal of entry. The portal of entry can be via the parenteral route (as in mosquito-borne
diseases such as malaria), via the oral route (as in typhoid fever), via sexual contact (as in HIV infection), as a bloodborne pathogen
(as in hepatitis B virus infection), via the respiratory tract (as in measles), and by horizontal transmission via transplacental infection
(as in congenital cytomegalovirus infection). In many cases of systemic infection, colonization occurs prior to the dissemination of
the infectious agent throughout the body. In some diseases (e.g., tetanus and diphtheria) the infection itself is caused by a noninvasive
organism and the systemic symptoms are caused by the dissemination of a toxin that is responsible for the disease. In most cases,
however, the etiologic agent is disseminated via the hematogenous route.
Patients may have certain risk factors or defects in host defenses that predispose them to specific types of infections. Examples of
defects in host defenses that predispose to certain specific types of infections include breaches in the integrity of the skin (patients
with burns, patients with invasive medical devices), defects in cell-mediated immunity (AIDS, corticosteroids), defects in humoral
immunity (hypogammaglobulinemia), decreased splenic function (splenectomy, sickle cell disease), quantitative defects in neutrophils
(neutropenia following chemotherapy), qualitative defects in neutrophils (chronic granulomatous disease, Chediak-Higashi syndrome),
and deficiencies in the complement system. It is important to be able to recognize these risk factors when they are present and to know
to what the defect predisposes the patient. Conversely, it is important to be able to suspect a specific defect in host defenses when a
patient presents with a systemic infection.
Protection of the host from a systemic infection can occur as a result of a prior infection with the specific agent of infection (e.g.,
measles) or due to a vaccination to that agent. Unfortunately, efficacious vaccines are not available for the majority of infectious
agents, and in many diseases, infection does not lead to protective immunity.
Important agents of systemic infection are listed below. Please note that virtually all bacteria can potentially be isolated from the blood
under circumstances of specific host defects, such as the presence of an intravenous catheter. Many of the etiologic agents listed have
a particular organ tropism (such as the liver for hepatitis viruses) but may cause systemic illness.
Cardiovascular & systemic Pathogens
Organism
Bacteria
Acinetobacter spp.
Bartonella henselae
Borrelia burgdorferi
Brucella spp.
Clostridium botulinum
Clostridium perfringens
Clostridium tetan
Coagulase-negative
staphylococci
Corynebacterium
diphtheriae
Enterobacter spp.
General Characteristics
Lactose-nonfermenting,
gram-negative bacilli
Fastidious, gram-negative
bacillus
Spirochete
Oxidase-positive, gramnegative bacilli
Anaerobic gram-positjve
bacillus
Anaerobic gram-positive
bacillus
Anaerobic gram-positive
bacillus
Catalase-positive,
coagulase-negative, grampositive cocci
Aerobic gram-positive
bacillus
Lactose-fermenting,
gram-negative bacilli
Source of Infection
Exogenous
Exogenous; cats appear to be
primary host
Tick borne
Zoonosis
Disease Manifestation
Nosocomial UTl, nosocomial pneumonia,
nosocomial and line-related bacteremia
Cat scratch disease; bacillary angiomatosis
(in immunocompromised)
Lyme disease; rash, arthritis, nervous
system and cardiac manifestations
Lymphadenopathy, hepatosplenomegaly;
genitourinary, bone, and CNS infection
Exogenous
Botulism
Exogenous
Gas gangrene, emphysematous
cholecystitis, bacteremia, food poisoning
Exogenous
Tetanus
Endogenous
Nosocomial bacteremia
Exogenous
Diphtheria
Endogenous
Community and nosocomial UTI,
bacteremia, intra-abdominal infections
8
Organism
General Characteristics
Catalase-negative, grampositive cocci
Lactose-fermenting,
gram-negative bacillus
Source of Infection
Francisella tularensis
Gram-negative bacillus
Zoonosis
Group A streptococci
(Streptococcus
pyogenes)
Catalase-negative, grampositive cocci
Endogenous
Group B streptococci
(Streptococcus
agalactiae)
Catalase-negative, grampositive cocci
Endogenous
Sepsis, meningitis, cellulitis
Klebsiella pneumoniae
Lactose-fermenting,
gram-negative bacillus
Endogenous
Community and nosocomial UTI,
bacteremia, intra-abdominal infections
Mycobacterium avium
complex
Acid-fast bacilli
Exogenous
Disseminated disease
Mycobacterium
tuberculosis
Acid-fast bacillus
Respiratory, may be exogenous
(primary) or endogenous
(reactivation)
Pneumonia, extrapulmonary tuberculosis,
miliary tuberculosis
Endogenous (from colonization)
Meningitis, bacteremia
Zoonosis (often animal bite or
scratch)
Cellulitis, bacteremia, osteomyelitis,
meningitis
Community and nosocomial UTI,
bacteremia
Enterococcus spp.
Escherichia coli
Neisseria meningitidis
Pasteurella multocida
Proteus mirabilis
Pseudomonas
aeruginosa
Oxidase-positive, gramnegative diplococcus
Oxidase-positive, gramnegative bacillus
Lactose-nonfermenting,
gram-negative bacillus
Lactose-nonfermenting,
Oxidase-positive, gramnegative bacillus
Endogenous
Endogenous
Endogenous
Exogenous
Rickettsia prowazekii
Rickettsial organism
Exogenous, lice to human
Rickettsia rickettsii
Exogenous, tick to human
Viridans group
streptococci
Rickettsial organism
Lactose-nonfermenting,
gram-negative bacillus
Catalase-positive,
coagulase-positive, grampositive coccus
Catalase-negative, grampositive coccus
Spirochete (does not
Gram stain)
Catalase-negative, grampositive cocci
Yersinia pestis
Gram-negative bacillus
Salmonella typhi
Staphylococcus aureus
Streptococcus
pneumoniae
Treponema pallidum
Exogenous, human to human
Endogenous
Disease Manifestation
Wound infections, nosocomial UTI,
bacteremia, endocarditis
Community and nosocomial UTI,
bacteremia, intra-abdominal infections
Ocular, lymphadenopathy, pulmonary,
bacteremia
Pharyngitis, cellulitis, bacteremia, scarlet
fever, necrotizing fasciitis, pneumonia,
poststreptococcal glomerulonephritis and
rheumatic fever
Community and nosocomial UTI, nosocomial
pneumonia, nosocomial bacteremia
Epidemic typhus causes fever and
disseminated intravascular coagulation.
Rocky Mountain spotted fever
Typhoid fever, bacteremia, intestinal
disease
Skin infections, bacteremia, endocarditis,
septic arthritis, abscesses
Direct sexual contact, vertical
(mother to child)
Community-acquired pneumonia, sinusitis,
meningitis, bacteremia, endocarditis
Primary, secondary, latent, and late
syphilis; can affect any organ
Endogenous
Endocarditis
Zoonosis; person to person in
pneumonic form
Lymphadenopathy (bubonic), pneumonia,
bacteremia
Endogenous
9
Viruses
Dengue Virus
Filoviruses
Parasites
Babesia microti
Leishmania donovani
Plasmodium spp.
Strongyloides
stercoralis
Taenia solium
Toxoplasma gondii
Enveloped polyhedral
capsid with singlestranded RNA
Enveloped helical capsid
with single-stranded RNA
Exogenous (Aedes aegypti
mosquito)
Can be seen on peripheral
blood smear
Amastigotes in tissue
touch preparation
Can be seen on peripheral
blood smear
Nematode
Exogenous (ticks)
Babesiosis
Exogenous (Phlebotomus fly)
Kalaazar
Exogenous (Anopheles mosquito)
Malaria
Exogenous; endogenous
(autoinfection and hyperinfection)
Exogenous
Gastrointestinal, pulmonary (pneumonia,
wheezing), disseminated in hyperinfection
Gastrointestinal infection, cysticercosis
(brain, muscles, other organs)
Central nervous system, ocular, hepatic,
pulmonary
Tapeworm
Protozoan
Exogenous: unknown possible animal
reservoir
Exogenous; endogenous
(reactivation)
Dengue Fever; joint pain, fever, headache,
rash, muscle pain, hemorrhagic
fever/shock
Hemorrhagic fever with high mortality.
Fungi
Aspergillus spp.
Molds with septate hyphae Exogenous
Blastomyces dermatitidis Dimorphic mold
Candida albicans
Yeast, often germ tube
positive
Exogenous
Endogenous
Candida spp., non- albicans Yeasts, germ tube negative Endogenous
Coccidioides immitis
Dimorphic mold
Exogenous
Cryptococcus neoformans Encapsulated yeast
Exogenous
Histoplasma capsulatum
Dimorphic mold
Exogenous
Zygomycetes
Molds with aseptate hyphae Exogenous
Pneumonia, sinusitis, external otitis, allergic
processes, disseminated infection
Pneumonia, meningitis, bone infection
Thrush, vaginal yeast infection, diaper rash,
esophagitis, nosocomial UTI, nosocomial
bloodstream infection
Thrush, vaginal yeast infection, nosocomial
UTI, nosocomial bloodstream infection
Pneumonia, meningitis, bone infection
Meningitis, pneumonia, bloodstream infection
Pneumonia, disseminated infection
Pneumonia, sinusitis, invasive infection
Introduction to Digestive Tract Diseases (Chapter 25)
The major clinical manifestation of infections affecting the gastrointestinal tract is diarrhea. Diarrheal pathogens have two basic
mechanisms by which they produce diarrhea. One is the production of toxins called enterotoxins, which cause physiologic changes in
the intestinal epithelium that result in fluid and electrolyte secretion. Vibrio cholerae, which produces an enterotoxin called cholera
toxin, is a classic example of a diarrheal pathogen which produces a secretory diarrhea due to the action of an enterotoxin.
Microscopically, the intestinal epithelium appears normal in patients with enterotoxin-induced diarrhea.
The other major mechanism of diarrheal disease is direct damage to the intestinal epithelium caused by cytotoxin or organism
invasion. The protozoan Entamoeba histolytica produces such a cytotoxin. This cytotoxin is responsible for the characteristic
ulcerative lesions which can be seen in individuals with amebic dysentery. A number of gastrointestinal pathogens including
Salmonella spp., Shigella spp., Campylobacter spp., and Yersinia enterocolitiae are capable of invading the intestinal epithelium.
Inflammation frequently occurs in response to these pathogens. Patients with diarrhea due to organisms that damage the epithelium
frequently will have white blood cells visible in their feces. However, these cells may also be present in feces of patients with
noninfectious inflammatory bowel disease, so results of examination of feces for white blood cells should be interpreted cautiously.
Diarrheal diseases are almost always spread by the fecal-oral route. This means that individuals who become infected with diarrheal
pathogens ingest either food or water which has been contaminated with human or animal feces containing the pathogens. Improper
handling or preparation of food and contamination of water due to poor sanitation are major means by which diarrheal pathogens are
spread. In the industrialized world, the spread of diarrheal disease is particularly problematic in day care centers for children. In
addition to spread by contaminated food and water, infected children can pass the organisms directly, by placing contaminated hands
in the mouths of other children, or indirectly, by using contaminated hands to handle toys which are then mouthed by other children.
The infectious dose of diarrheal pathogens varies greatly, with the infectious doses of Salmonella spp. and V. cholerae in the
10
hundreds of thousands to millions, while that for Shigella spp. is less than 100 organisms.
Because the major pathophysiologic effect of diarrhea is dehydration due to fluid and electrolyte loss, the most important treatment is
rehydration. In recent years, simple solutions of glucose, salts, and water given orally have been developed which are proven to be
highly effective in treating patients with even the most severe forms of diarrhea. The widespread use of oral rehydration in the past
two decades, especially in the developing world, has been credited with saving literally millions of lives, primarily young children in
whom diarrheal disease takes the greatest toll.
In addition to diarrheal disease, hepatitis is an important infection in the gastrointestinal system. The epidemiology of hepatitis A
virus is the same as that of diarrheal pathogens. The virus is usually obtained by ingestion of raw shellfish taken from water
contaminated by human sewage or of food handled by an infected food handler who has poor personal hygiene, i.e., individuals who
fail to wash their hands after a bowel movement. Hepatitis Band C viruses are spread by contaminated blood. Contracting hepatitis
used to be a major concern in individuals receiving blood transfusions. With the recognition of these agents and the development of
screening tests for them, the epidemiology of hepatitis due to these two viruses has changed. Hepatitis Band C virus infections (and
also human immunodeficiency virus [HIV] infections) are frequent in individuals who share needles while using illicit intravenous
drugs. Hepatitis B virus is also spread sexually, especially in populations which practice anal intercourse. The frequency of spread of
hepatitis C virus sexually is not well understood. Unlike hepatitis A virus, which causes a relatively mild self-limited disease,
hepatitis B virus can cause fulminant, sometimes fatal disease. Hepatitis Band C viruses can also cause a chronic infection
culminating in liver failure. Vaccines are available for hepatitis A and B but not C virus.
Other important types of gastrointestinal infection are ones in which the resident intestinal microflora or pathogens escape from the
bowel and enter "sterile" tissues. One example is Entamoeba histolytica trophozoites, which enter the liver and cause an amebic
abscess. Another is when there is penetrating trauma to the intestines, as might occur with a gunshot wound to the abdomen or during
bowel surgery. In either situation, microbes can escape from the intestines into the peritoneum, where they can cause peritonitis or
form an abscess. The organisms causing these infections are typically a mixture of both facultative and anaerobic bacteria that reside
in the colon.
Digestive Tract Pathogens
Organism
Bacteria
Baeteroides (ragilis
Campylobaeter spp.
General characteristics
Usual source of infection
Disease manifestation
Anaerobic, gram-negative bacillus
Microaerophilic, curved, gramnegative bacilli
Anaerobic, toxin-producing, grampositive bacillus
Anaerobic, gram-positive bacillus
Endogenous
Poultry
Sorbitol-nonfermenting, gramnegative bacillus
Lactose-fermenting, gramnegative bacillus
Lactose-nonfermenting, gramnegative bacilli
Lactose-nonfermenting, gramnegative bacilli
Catalase-positive, gram-positive
coccus
Oxidase-positive, gram-negative
bacilli
Lactose-nonfermenting, gramnegative bacillus
Improperly cooked ground beef;
apple juice/cider
Fresh fruit and vegetables
Abdominal abscess
Invasive diarrhea, sepsis in AIDS
patients
Antibiotic-associated diarrhea,
pseudomembranous colitis
Gangrenous lesions of bowel or
gall bladder; food poisoning
Enterohemorrhagic colitis,
hemolytic-uremic syndrome
Traveler's diarrhea, watery
diarrhea
Invasive diarrhea, typhoid fever
Parasites
Ascaris lumbricoides
Clostridium difficile
Clostridium perfringens
Enterohemorrhagic
Escherichia coli
Enterotoxigenic
Escherichia coli
Salmonella spp.
Shigella spp.
Staphylococcus aureus
Endogenous; nosocomial
Endogenous; high-protein foods
Animal products; typhoid (human
to human)
Human to human; day care centers
Invasive diarrhea, dysentery
High-protein foods
Food poisoning
Raw fish and shellfish
Large-volume watery diarrhea
Meat and dairy products
Watery or invasive diarrhea
Roundworm
Food, soil
Cryptosporidium parvum
Coccidian parasite
Cyclospora spp.
Coccidian parasite
Fecally contaminated water; day
care centers
Water,
fresh
fruits
and
vegetables
Diarrhea, abdominal discomfort,
intestinal obstruction
Malabsorptive diarrhea (chronic in
AIDS)
Malabsorptive diarrhea
Vibrio spp.
Yersinia enterocolitica
11
Organism
Echinococcus spp.
General characteristics
Dog tapeworm
Disease manifestation
Hydatid cyst of liver
Hookworm
Usual source of infection
Ingestion of tapeworm eggs from
infected dog
Water, fresh fruits and
vegetables
Fecally contaminated water, day
care centers
Skin contact with larvae in soil
Entamoeba histolytica
Amoeba
Giardia lamblia
Flagellated trophozoite
Necator americanus,
Ancylostoma duodenale,
Viruses
Enterovirus
Nonenveloped RNA virus
Fecal-oral
Hepatitis A virus
Hepatitis B virus
Nonenveloped RNA virus
Enveloped DNA virus
Shellfish, infected food handlers
Blood, direct sexual contact
Hepatitis C virus
RNA virus
Blood
Norwalk agent (calicivirus)
Nonenveloped RNA virus
Rotavirus
Wheel-like, nonenveloped RNA
virus
Shellfish, common-source food
outbreaks
Human to human (day care center)
Diarrhea, respiratory disease,
aseptic meningitis, exanthems
Acute, self-limited hepatitis
Acute and chronic hepatitis,
fulminant hepatitis, hepatic
carcinoma
Acute and chronic hepatitis,
fulminant hepatitis, hepatic
carcinoma
"24-hour flu," vomiting, diarrhea
Diarrhea, amebic dysentery, liver
abscess
Malabsorptive diarrhea (acute;
chronic)
Anemia, gastrointestinal
discomfort
Diarrhea, vomiting
Introduction to Genitourinary Diseases (Chapter 26)
We begin this text with a discussion of infections of the genitourinary tract for two reasons. First, the number of microorganisms
which frequently cause infection in these organs is somewhat limited. Second, urinary tract infections (UTls) and sexually transmitted
diseases (STDs) are two of the most common reasons why young adults, particularly women, consult a physician. UTls are examples
of endogenous infections, i.e., infections which arise from the patient's own microflora. In the case of UTls, the microbes generally
originate in the gastrointestinal tract and colonize the periurethral region before ascending the urethra to the bladder. STDs are
exogenous infections; i.e., the infectious agent is obtained from a source outside the body. In the case of STDs, these agents are
obtained by sexual contact.
UTls are much more common in women than men for a number of reasons. The urethra is shorter in women than in men, making it
easier for microbes to ascend to the bladder. Prostatic secretions are antibacterial, which further protects the male. The periurethral
epithelium in women, especially women with recurrent UTls, is more frequently colonized with microorganisms which cause UTls. It
should also be noted that the incidence of UTls is higher in sexually active women, as coitus can "force" organisms colonizing the
periurethral region into the urethra. The incidence of nosocomial UTls, however, is similar in women and men. In these infections,
catheterization is the major predisposing factor.
The incidence of STDs is similar in both heterosexual men and women; however, the morbidity associated with these infections tends
to be much greater in women. In particular, irreversible damage to reproductive organs, caused by both Chlamydia trachomatis and
Neisseria gonorrhoeae, is all too common. Whereas infections with these two organisms are almost always symptomatic in males, a
significant number of women may be infected asymptomatically at first. They may manifest signs and symptoms of infection only
when they develop pelvic inflammatory disease, which can result in sterility. Fetal loss or severe perinatal infection may be caused by
two other STD agents, herpes simplex virus and Treponema pallidum, the etiologic agent of syphilis.
Important agents of genitourinary tract infections are listed in the table below. Only organisms in this table should be considered in
your differential diagnosis for the cases you have been provided. You should note that not all organisms that can be spread sexually,
such as hepatitis B virus and Entamoeba histolytica, are listed. This is because these infections do not have genitourinary tract
manifestations.
Genitourinary Tract Pathogens
Organism
Bacteria
Actinomyces spp.
Bacteroides fragilis
Chlamydia
trachomatis
General characteristics
Source of infection
Disease manifestation°
Anaerobic, gram-positive bacilli
Anaerobic, gram-negative bacillus
Obligate intracellular pathogen (does
not Gram stain)
Endogenous
Endogenous
Direct sexual
contact
PID associated with intrauterine device usage
Pelvic abscess
Urethritis, cervicitis, PID
12
Enterobacter spp.
Lactose-fermenting gram-negative
bacilli
Catalase-negative, gram-positive cocci
Lactose-fermenting gram-negative
bacilli
Fastidious pleiomorphic gram negative
bacillus
Lactose-fermenting gram-negative
bacilli
Lactose non-fermenting gram-negative
bacillus
Endogenous
Community or nosocomial UTI
Endogenous
Nosocomial UTI
Endogenous
Community or Nosocomial UTI
Direct sexual
contact
Chancroid (painful genital ulcer)
Endogenous
Community or nosocomial UTI
Endogenous
Community or nosocomial UTI
Direct sexual
contact
Urethritis, cervicitis, PID
Endogenous
Community or nosocomial UTI
catheterization
Nosocomial UTI
Catheterization,
endogenous
Nosocomial UTI, Community-acquired UTI,
biofilm agent
Catalase-positive, gram-positive coccus
Endogenous
Community-acquired UTI
Treponema pallidum
Spirochete (does not Gram stain)
Direct sexual
contact; vertical,
from mother to child
Chancre (painless genital ulcer); primary,
secondary, tertiary syphilis; neonatal syphilis
Fungi
Candida sp.
Parasites
Yeast with pseudohyphae
Endogenous
Vaginitis, nosocomial UTI
Phthirus pubis
Crab lice
Enterococcus spp.
Escherichia coli
Haemophilus ducreyi
Klebsiella
pneumoniae
Morganella morganii
Neisseria
gonorrhoeae
Proteus mirabilis
Pseudomonas
aeruginosa
Staphyloccus
epidermidis
Staphylococcus
saprophyticus
Trichomonas
vaginalis
Viruses
Gram-negative intracellular diplococcus
Lactose non-fermenting, swarming
gram-negative bacillus
Lactose non-fermenting gram-negative
bacillus
Coagulase-negative, gram-positive
coccus
Protozoan
Herpes simplex virus
Enveloped DNA virus
Human
immunodeficiency
virus (HIV)
Retrovirus
Human papillomavirus
Nonenveloped DNA virus
Direct sexual
contact
Direct sexual
contact
Direct sexual
contact; vertical,
from mother to child
Direct sexual
contact, blood;
vertical, from
mother to child
Direct sexual
contact
Pubic hair infestation
Vaginitis
Recurrent genital ulcers, fetal/neonatal
infections, encephalitis
AIDS, neonatal infection, dementia
Genital warts, cervical carcinoma
13