Download Low G + C Gram-Positive Bacteria

CHAPTER
11 and 19 –
24
Characterizing
and
Classifying
Prokaryotes
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Survey of Bacteria
• Low G + C Gram-Positive Bacteria
• G + C content below 50%
• Have similar 16S rRNA sequences
• Classified in phylum Firmicutes
• Rod-shaped, obligate anaerobes
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Survey of Bacteria
• Low G + C Gram-Positive Bacteria
• Clostridia
• Rod-shaped, obligate anaerobes
• Important in medicine and industry
• Produce toxins that cause diseases in humans
• Endospores survive harsh conditions
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Bacterial Diseases of the Digestive System
• Bacterial Gastroenteritis: C. diff.
(Antimicrobial-Associated) Diarrhea
• Signs and symptoms
• Pseudomembranous colitis occurs in severe cases
• Pathogen and virulence factors
• Caused by Clostridium difficile
• Antimicrobial use facilitates overgrowth of C. difficile
• C. difficile produces two toxins
• Pathogenesis
• Toxins mediate inflammation and pseudomembrane
formation
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Figure 23.7 Pseudomembranous colitis.
Lesions
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Bacterial Diseases of the Digestive System
• Bacterial Gastroenteritis: C. diff.
(Antimicrobial-Associated) Diarrhea
• Epidemiology
• By-product of modern medicine
• Any antimicrobial can trigger the disease
• Diagnosis, treatment, and prevention
• Diagnosis is based on presence of bacterial toxin in stool
• Treated with antimicrobials
• Avoid unnecessary use of antimicrobials
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Bacterial Diseases of the Skin and Wounds
• Gas Gangrene
• Signs and symptoms
• Blackening of infected muscle and skin
• Presence of gas bubbles
• Pathogens and virulence factors
• Caused by several Clostridium species
• Gram-positive endospore-forming
bacilli
• C. perfringens is most often isolated
• Bacterial endospores survive harsh
conditions
• Vegetative cells secrete 11 toxins
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Bacterial Diseases of the Skin and Wounds
• Gas Gangrene
• Pathogenesis and epidemiology
• Traumatic event must introduce endospores into dead tissue
• Mortality rate exceeds 40%
• Diagnosis, treatment, and prevention
• Appearance is usually diagnostic
• Rapid treatment is crucial
• Surgical removal of dead tissue
• Administration of antitoxin and antimicrobials
• Prevented with proper cleaning of wounds
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Survey of Bacteria
• Low G + C Gram-Positive Bacteria
• Bacillus, common in soil - Bacillus anthracis causes
anthrax
• Listeria - contaminates milk and meat products
• Capable of reproducing under refrigeration
• Survives inside phagocytic white blood cells
• Rarely causes disease in adults
• In pregnant women, can kill the fetus if crosses the
placenta
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Bacterial Diseases of the Skin and Wounds
• Cutaneous Anthrax
• Caused by Bacillus anthracis
• Characterized by an eschar
• Black, painless ulcer
• Treated with antimicrobial drugs
• Prevention requires control of the disease in animals
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Survey of Bacteria
• Low G + C Gram-Positive Bacteria
• Other low G + C bacilli and cocci
• Lactobacillus - Grows in the human mouth, stomach,
intestinal tract, and vagina
• Rarely causes disease
• Streptococcus and Enterococcus
• Cause numerous diseases
• Various strains of multi-drug-resistant streptococci
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Survey of Bacteria
• Low G + C Gram-Positive Bacteria
• Staphylococcus
• One of the most common inhabitants of humans
• Produces toxins and enzymes that contribute to
disease
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Bacterial Diseases of the Skin and Wounds
• Staphylococcal Scalded Skin Syndrome
• Pathogen and virulence factors
• Some Staphylococcus aureus strains
• One or two different exfoliative toxins cause SSSS
• Pathogenesis
• No scarring because dermis is unaffected
• Death is rare but may be due to secondary infections
• Epidemiology
• Disease occurs primarily in infants
• Transmitted by person-to-person spread of bacteria
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Figure 19.3 Staphylococcal scalded skin syndrome.
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Bacterial Diseases of the Skin and Wounds
• Staphylococcal Scalded Skin Syndrome
• Diagnosis, treatment, and prevention
• Diagnosed by characteristic sloughing of skin
• Treated by administration of antimicrobial drugs
• Widespread presence of S. aureus makes prevention
difficult
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Bacterial Diseases of the Skin and Wounds
• Impetigo (Pyoderma) and Erysipelas
• Signs and symptoms
• Impetigo: red patches form on the face and limbs
• Erysipelas: infection spreads to the lymph nodes
• Pathogens and virulence factors
• Most cases are caused by S. aureus
• Some cases caused by Streptococcus pyogenes
• Gram-positive coccus, arranged in chains
• Virulence factors contribute to impetigo
• M protein
• Hyaluronic acid
• Pyrogenic toxins
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Figure 19.4 Impetigo.
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Figure 19.5 Erysipelas.
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Bacterial Diseases of the Skin and Wounds
• Impetigo (Pyoderma) and Erysipelas
• Pathogenesis
• The bacteria invade where the skin is compromised
• Acute glomerulonephritis can result if infection spreads to
the kidneys
• Epidemiology
• Transmitted by person-to-person contact or via fomites
• Impetigo occurs most in children
• Erysipelas can also occur in the elderly
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Bacterial Diseases of the Skin and Wounds
• Impetigo (Pyoderma) and Erysipelas
• Diagnosis, treatment, and prevention
• The presence of vesicles is diagnostic for impetigo
• Impetigo is treated with oral and topical antimicrobials and
careful cleaning of infected areas
• Erysipelas is treated with penicillin
• Prevent with proper hygiene and cleanliness
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Survey of Bacteria
• High G + C Gram-Positive Bacteria
• Mycobacterium
• Aerobic rods that sometimes form filaments
• Slow growth, partly due to mycolic acid in its cell walls
• Mycobacterium tuberculosis - tuberculosis
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Survey of Bacteria
• Gram-Negative Proteobacteria
• Largest and most diverse group of bacteria
• Five classes of proteobacteria
• Alphaproteobacteria
• Betaproteobacteria
• Gammaproteobacteria
• Deltaproteobacteria
• Epsilonproteobacteria
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Survey of Bacteria
• Gram-Negative Proteobacteria
• Alphaproteobacteria
• Often capable of growing at low nutrient levels
• Some species have extensions called prosthecae
• Used for attachment and nutrient absorption
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Survey of Bacteria
• Gram-Negative Proteobacteria
• Alphaproteobacteria
• Pathogenic alphaproteobacteria
• Rickettsia
• Transmitted through bite of an arthropod
• Causes several human diseases
• Brucella
• Causes brucellosis
• Survives phagocytosis by white blood cells
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Bacterial Diseases of the Skin and Wounds
• Spotted Fever Rickettsiosis
• Signs and symptoms
• Nonitchy spotted rash on trunk and
appendages
• Organ failure can occur in severe cases
• Pathogen and virulence factors
• Caused by Rickettsia rickettsii
• Gram-negative intracellular parasite
• Rickettsias do not use glucose as a
nutrient
• Pathogen avoids digestion in phagosome
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Bacterial Diseases of the Skin and Wounds
• Rocky Mountain Spotted Fever
• Pathogenesis
• R. rickettsii does not secrete any toxins
• Disease occurs from damage to blood
vessels
• Epidemiology
• Transmitted via bite of infected tick
• Diagnosis, treatment, and prevention
• Diagnosed with serological testing
• Treated with various antimicrobials
• Prevented with the use of tick repellents and
avoidance of tick-infested areas
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Figure 19.9 Number of cases of Rocky Mountain spotted fever in the United States, 2002–2012.
23
76
29
4
87
46
47
15
34
28
219
71
41
10
72
95
22
48
36
739
105
24
198
71
348
119
223
562 195
756
48
174
46
2666
101 1456
4470
2398
609 1951
433
144 697 658
85
453
341
8
10
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Key:
0–400
401–800
801–1200
1201–1600
1601–2000
>2000
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Survey of Bacteria
• Gram-Negative Proteobacteria
• Betaproteobacteria
• Pathogenic betaproteobacteria
• Neisseria
• Bordetella
• Burkholderia
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Bacterial STDs
• Gonorrhea
• Signs and symptoms
• Men experience painful urination
and a purulent discharge
• Women are often asymptomatic
• Pelvic inflammatory disease may develop
• Pathogen and virulence factors
• Caused by Neisseria gonorrhoeae
• Virulence factors include fimbriae, capsule, and
endotoxin
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Bacterial STDs
• Gonorrhea
• Pathogenesis
• Bacteria attach to epithelial cells of the mucous
membranes
• Epidemiology
• Gonorrhea occurs only in humans
• Risk increases with frequency of sexual encounters
• Diagnosis, treatment, and prevention
• Genetic probes are used to diagnose asymptomatic
infection
• Treated with broad-spectrum cephalosporin
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Figure 24.5 The incidence of civilian gonorrhea in the United States.
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Bacterial Diseases of the Lower Respiratory
System
• Pertussis (Whooping Cough)
• Signs and symptoms
• Initially coldlike, then characteristic cough develops
• Pathogen and virulence factors
• Bordetella pertussis is the causative agent
• Produces numerous virulence factors
• Includes adhesins and several toxins
• Pathogenesis
• Pertussis progresses through four phases
• Incubation, catarrhal, paroxysmal, and convalescent
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Bacterial Diseases of the Lower Respiratory
System
• Pertussis (Whooping Cough)
• Epidemiology
• Highly contagious
• Bacteria spread through airborne droplets in air
• Bacteria does not survive long outside the body
• Diagnosis, treatment, and prevention
• Symptoms are usually diagnostic
• Treatment is primarily supportive
• Prevention is with the DTaP vaccine. Adult boosters!!!!
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Emerging Disease Chapter 11 and Chap. 22
• Increasing number of cases of pertussis since
1980s
• Adults are not very symptomatic
• Infants under 12 months have more serious
disease.
• Diagnosis?
• Treatment?
• Prevention?
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Survey of Bacteria
• Gram-Negative Proteobacteria
• Gammaproteobacteria
• Largest and most diverse class of proteobacteria
• Divided into subgroups
• Intracellular pathogens – survive in WBC
• Legionella
• Glycolytic facultative anaerobes - Enterobacteriaceae
• Pseudomonads
• Pseudomonas
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Bacterial Diseases of the Skin and Wounds
• Pseudomonas Infection
• Pathogen and virulence factors
• Pseudomonas aeruginosa is the causative agent
• Gram-negative bacillus
• Found in soil, decaying matter, moist environments
• Numerous virulence factors
• Fimbriae, adhesins, capsule, toxins, enzymes
• Rarely causes disease despite virulence factors
• Pathogenesis
• Infection can occur in burn victims
• Bacteria grow under the surface of the burn
• The bacteria kills cells, destroys tissue, and triggers shock
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Figure 19.8 Pseudomonas aeruginosa infection.
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Survey of Bacteria
• Gram-Negative Proteobacteria
• Epsilonproteobacteria
• Campylobacter
• Causes blood poisoning and intestinal inflammation
• Helicobacter
• Causes ulcers
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Survey of Bacteria
• Other Gram-Negative Bacteria
• Chlamydias
• Grow intracellularly in mammals, birds, and some
invertebrates
• Chlamydia - Most common sexually transmitted
bacteria in the United States
• Spirochetes
• Motile bacteria that move in a corkscrew motion
• Treponema and Borrelia both cause disease in
humans
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Bacterial STDs
• Syphilis
• Signs and symptoms
• Four phases of syphilis
• Primary syphilis
• Secondary syphilis
• Latent syphilis
• Tertiary syphilis
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Figure 24.6 The lesions of syphilis.
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Bacterial STDs
• Syphilis
• Pathogen and virulence factors
• Treponema pallidum causes syphilis
• Lives only in humans
• Virulence factors have been difficult to identify
• Pathogenesis
• Transmitted mostly via sexual contact
• Sometimes transmitted from mother to child
• Most individuals do not develop tertiary syphilis
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Bacterial STDs
• Syphilis
• Epidemiology
• Syphilis occurs worldwide
• Endemic among sex workers, men who have sex with
men, and users of illegal drugs
• Diagnosis, treatment, and prevention
• Antibody test is used to diagnose primary, secondary, and
congenital syphilis
• Tertiary syphilis is difficult to diagnose
• Penicillin G is used to treat all but tertiary syphilis
• Prevented with safe sex practices
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Figure 24.7 The incidence of syphilis in the United States.
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Bacterial Cardiovascular and Systemic
Diseases
• Lyme Disease
• Signs and symptoms
• Three phases in untreated patients
• Bull's-eye rash at infection site
• Neurological symptoms
• Severe arthritis
• Pathogen and virulence factors
• Caused by the spirochete Borrelia burgdorferi
• Use of manganese instead of iron circumvents host
defense
• Avoids immune detection by altering membrane proteins
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Figure 21.9 The life cycle of the deer tick Ixodes and its role as the vector of Lyme disease.
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Bacterial Cardiovascular and Systemic
Diseases
• Lyme Disease
• Diagnosis, treatment, and prevention
• Diagnosis is based on the signs and symptoms of the
disease
• Bacterium is rarely detected in the blood
• Antimicrobial drugs are used in the early phases
• Treatment of later phases is difficult
• Symptoms often caused by the immune system
• Prevented with repellents containing DEET and with
protective clothing
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Bacterial Cardiovascular
and Systemic Diseases
• Lyme Disease
• Epidemiology
• One of the most reported
vector-borne diseases in United States
• Three events contributed to an increase in Lyme disease
• Movement of human populations into woodland areas
• Protection of the deer population
• Coyotes have displaced the foxes that help control the
mouse population
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Figure 21.10 The occurrence of Lyme disease in the United States.
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Bacterial Diseases of the Nervous System
• Bacteria Cause Disease in Two Ways
• Infect cells of the nervous system
• Meningitis
• Leprosy
• Bacteria growing elsewhere release toxins that affect
neurons
• Botulism
• Tetanus
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Bacterial Diseases of the Nervous System
• Bacterial Meningitis
• Signs and symptoms
• Sudden high fever, severe meningeal inflammation, and
increased white blood cells in the CSF
• Inflammation causes most signs and symptoms
• Infection of the brain causes encephalitis
• Can result in behavioral changes, coma, and death
• Can develop rapidly
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Bacterial Diseases of the Nervous System
• Bacterial Meningitis
• Pathogens and virulence factors
• Five species cause 90% of bacterial meningitis cases
• Neisseria meningitidis
• Streptococcus pneumoniae
• Haemophilus influenzae
• Listeria monocytogenes
• Streptococcus agalactiae
• Opportunistic members of the normal microbiota can also
cause meningitis
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Figure 20.2 Artist's rendition of diplococci of Neisseria meningitidis.
Polysaccharide
capsule
Lipooligosaccharide (LOS)
in outer
membrane
Fimbria
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Figure 20.3 Cells of Streptococcus pneumoniae are typically arranged in pairs.
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Figure 20.4 The pleomorphic bacilli of Haemophilus influenzae in a Gram-stained smear.
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Disease In Depth 20.1.1 (3 of 4)
ONE WAY LISTERIA AVOIDS HOST’S IMMUNE
SYSTEM WHILE INFECTING NEW CELLS
1 Listeria enters the body,
usually through contaminated
drink or food.
2 Listeria is
phagocytizedby
a host cell,
typically in
thegall bladder.
Listeria
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4 The bacterium reproduces within
the phagocyte. Some Listeria mRNA
activate at 37˚C,so the bacterium
reproducesmost rapidly inside human
cells.
5 The bacterium
polymerizes the host cell’s
actin filaments into a “tail.”
3 The intracellular bacterium escapes
the phagosome.
INFECTED HOST CELL
Actin “tail”
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Disease In Depth 20.1.2 (3 of 6)
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Bacterial Diseases of the Nervous System
• Bacterial Meningitis
• Pathogenesis
• S. agalactiae is acquired during birth
• Listeria is transmitted via contaminated food
• Other species are transmitted via respiratory droplets
• Bacteria usually spread via the blood to the meninges
• Head or neck trauma may allow entry of bacteria into the
meninges
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Bacterial Diseases of the Nervous System
• Bacterial Meningitis
• Diagnosis, treatment, and prevention
• Diagnosis is based on symptoms and culturing of bacteria
from CSF
• Treated with intravenous antimicrobial drugs
• Vaccines available for S. pneumoniae, H. influenzae type
b, and N. meningitidis
• Administration of penicillin at birth reduces neonatal
meningitis due to S. agalactiae
• Individuals at risk for listeriosis should avoid high-risk
foods
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Bacterial Diseases of the Nervous System
• Bacterial Meningitis
• Epidemiology
• H. influenzae was leading cause of bacterial meningitis
prior to vaccination
• S. pneumoniae and N.meningitidis are now most
prevalent
• S. agalactiae is leading cause of meningitis in newborns
• Not spread by casual contact
• Meningococcal meningitis can become epidemic
• Spreads among individuals in barracks and dorms
• Listeria is not transmitted among humans except from
mother to fetus
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Bacterial Diseases of the Nervous System
Case Study - Under pressure and Under the
weather
• What about the patient?
• Diagnosis – gram stain? of what?
• How did Lin contract N. meningitides
• Why is treating Lin’s meningitis a challenge?
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