Download Diphtheria (Corynebacterium diphtheriae)

Bacterial infections
Diphtheria, Pertussis and Enteric fever
Dr Mubarak Abdelrahman
Assistant Professor Jazan University
Gram negative:
Diplococci
Bacilli
Coccobacilli
Gram Positive:
Diplococci
Chains
Clusters
Rods & cocobacilli
Diphtheria
(Corynebacterium diphtheriae)
•An acute toxic infection caused by
•Corynebacterium diphtheriae
•A gram-positive bacilli.
Epidemiology
C. diphtheriae :
• An exclusive inhabitant of human mucous
membranes and skin.
• Spread by airborne respiratory droplets and
direct contact.
• Can remain viable in dust for 6 months.
Pathogenesis
The exotoxin:
• Inhibits protein synthesis and causes local tissue
necrosis.
• In respiratory tract leads to pseudo-membrane.
• Absorption can lead to systemic manifestations:
e.g. kidney tubule necrosis, thrombocytopenia,
cardiomyopathy, demyelination of nerves, ..
Clinical Manifestations
The manifestations are influenced by:
• The anatomic site of infection.
• The immune status of the host.
• The production and distribution of the toxin.
Respiratory Tract Diphtheria
• Incubation period of 2-4 days (<7).
• Local signs and symptoms of inflammation.
• Soft tissue edema + enlarged lymph nodes
causes a bull-neck appearance.
A
B
A: Bull neck
B: pseudo membrane
C: Skin diphtheria
C
Diagnosis
• Differential diagnoses:
- Epiglottitis.
- Exudative pharyngitis caused by Streptococcus
pyogenes or Epstein-Barr virus.
• Diagnosis:
- Helped by the characteristic adherent
membrane and relative lack of fever.
- Specimens for culture from nose, throat and any
other mucocutaneous lesion.
Complications
• Respiratory tract obstruction .
• Toxic cardiomyopathy
In 10-25% of patients with respiratory diphtheria
and is responsible for 50-60% of deaths.
• Toxic Neuropathy acutely or 2-3 weeks after
onset of oropharyngeal inflammation:
- Local paralysis: soft palate, pharynx, larynx, ..
- Cranial neuropathies: oculomotor paralysis.
- Symmetric polyneuropathy.
Treatment
• Specific antitoxin:
Should be administered on the basis of clinical diagnosis.
• The antibiotics (Erythromycin or penicillin)
- Stop toxin production.
- Treat localized infection.
- Prevent transmission of the organism to contacts.
• Supportive Care:
- Bed rest is essential for ≥2 weeks
(the period of risk for symptomatic cardiac damage).
Prevention
• Protection by immunization with toxoid.
• All contacts are:
- Closely monitored through the incubation
period.
- Given Antimicrobial prophylaxis regardless of
immunization status.
• Asymptomatic carriers also treated.
Pertussis (Bordetella pertussis
and Bordetella parapertussis)
Pertussis meaning intense cough. Also known as
whooping cough.
Etiology: by Bordetella organisms:
- Gram-negative coccobacilli.
- Colonize only ciliated epithelium.
Epidemiology
• Pertussis is extremely contagious.
• B. pertussis does not survive for prolonged
periods in the environment.
• Chronic carriage by humans is not documented.
• Subclinical infection is around 80% .
• Neither natural disease nor vaccination provides
complete or lifelong immunity.
Pathogenesis
• The exact mechanism of disease remains unknown.
• B. pertussis expresses pertussis toxin (PT) and
other biologically active substances may be
responsible for the local epithelial damage that
produces respiratory symptoms and this facilitates
absorption of PT.
Clinical Manifestations
• Incubation period 3-12 days.
• Classically divided into 3 stages:
1. The catarrhal stage (1-2 weeks) congestion,
rhinorrhea, low-grade fever, sneezing, lacrimation, ..
2. The paroxysmal stage (2-6 weeks) the cough begins
as dry, intermittent, irritative, paroxysmal followed by a
loud whoop ± Post-tussive vomiting.
3. The convalescent stage (≥2 weeks) the number,
severity and duration of episodes diminish.
Clinical Manifestations cont.
• Infants <3 months:
- No classic stages.
- Apnea may be the only symptom.
- Cyanosis is common.
- Sudden infant death.
• In non immunized infants:
- Cough and whooping louder and more classic.
• Adolescents and previously immunized children:
- Mild illness.
On physical examination:
• No signs of lower
respiratory tract disease.
• Can be complicated by
secondary pneumonia.
• Conjunctival hemorrhage.
• Petechiae on the upper
body are common.
Diagnosis
• A clinical case definition of cough of ≥14 days’
duration with at least 1 associated symptom of
paroxysms, whoop, or post-tussive vomiting.
• Absolute lymphocytosis is characteristic in the
catarrhal stage.
• Diagnosis confirmed by:
1. Isolation of B. pertussis in nasopharyngeal
swab culture (main).
2. Serologic tests: detection of antibodies to B.
pertussis.
Complications
1. Apnea.
2. Secondary infections (otitis media, pneumonia, ..).
3. Physical sequelae of forceful coughing e.g:
- conjunctival hemorrhages.
- epistaxis.
- hemorrhage in the central nervous system.
- pneumothorax.
- umbilical and inguinal hernias.
4. Bronchiectasis has been reported.
Treatment
• Infants <3 months of age with suspected pertussis
are always admitted to hospital.
• Antibiotics are always given when pertussis is
suspected or confirmed.
• Macrolides are the preferred agents
(erythromycin, Azithromycin)
• Isolation of patients and prophylaxis antibiotics
to all contacts regardless of age or immunization.
Prevention
• Immunization with pertussis vaccine, beginning
in infancy with periodic reinforcing doses through
adolescence and adulthood.
Enteric Fever (Typhoid Fever)
Etiology:
Typhoid fever is caused by Salmonella Typhi and S.
Paratyph, a gram-negative bacilli.
Epidemiology
• In developed countries: <15 cases/100,000.
• In the developing world, estimated rates bet.
100 to 1,000 cases/100,000 population.
• The highest incidence, complications and
hospitalization in children <5 years of age.
• Direct or indirect contact with an infected person
(sick or chronic carrier) is a prerequisite for
infection.
Pathogenesis
• After ingestion, S. typhi invade through the gut
mucosa to mesenteric lymphoid system then into
the bloodstream causing bacteremia.
• The incubation period 7-14 days; (3-30)days.
Clinical Features
• Mild illness (low-grade fever, malaise, dry cough).
• Severe (high-grade fever, generalized myalgia, abdominal pain,
hepatosplenomegaly, anorexia, ..).
• The classic stepladder rise of fever is relatively rare.
In children, diarrhea may be followed by constipation.
• Rose spots:
- Macular/maculopapular rash.
- appear around the 7-10th day of the illness.
- on the lower chest and abdomen.
- last 2-3 days.
Complications
• Hepatitis and cholecystitis.
• Intestinal hemorrhage and perforation.
• Toxic myocarditis.
• Neurologic complications (delirium, psychosis,
Guillain-Barre syndrome..).
• Others:
DIC, hemolytic-uremic syndrome, nephrotic syndrome,
meningitis and suppurative lymphadenitis.
Differential Diagnosis
• Acute gastroenteritis, bronchitis, and
bronchopneumonia.
• Malaria and sepsis with other bacterial pathogens.
• Tuberculosis, brucellosis, Dengue fever, acute
hepatitis, infectious mononucleosis.
• Others (malignancies, rheumatological, …)
Diagnosis
• The mainstay is by a positive culture .
- Blood cultures early.
- Stool and urine culture after the 1st wk.
• Leukocyte counts frequently low in relation to fever and
toxicity.
• Thrombocytopenia: severe illness (may accompany DIC).
• Liver function test.
• Widal test but many false-positive and false-negative results.
• Other diagnostic tests: PCR and monoclonal antibodies.
• In the developing world the mainstay of diagnosis is clinical.
Treatment
• Supportive: adequate rest, hydration, correct fluid
and electrolyte.
• Antipyretic therapy.
• A soft, easily digestible diet if no abdominal
distention or ileus.
• Antibiotic therapy (chloramphenicol or amoxicillin
quinolones or third-generation cephalosporin)
Prevention
• Good sanitation services and central chlorination of water.
• Avoid consumption of street foods!
• Hand washing.
Vaccination: (two vaccines)
1. An oral, live-attenuated preparation of S. Typhi, from 6
years of age.
2. The Vi capsular polysaccharide for ≥2 years of age.
Intramuscular with a booster every 2 years.