Lecture 5: Yersinia Bordetella Gram - coccobacilli

Gram (-) coccobacilli

1.Yersinia  Y. pestis - black plague

2.Bordetella  B. pertussis - whooping cough

Genus Yersinia

Part of Enterobacteriaceae family - cocco/bacilli, safety pin

Genus Yersinia Characteristics

Non motile, psychrophilic, facultative intracellular anaerobes

Genus Yersinia Species

18 species mostly animal pathogen but 3 are pathogenic to human

Y. entercolitica + Y. pseudotuberculosis - diarrheal GI diseases

Y. pestis - Causative agent of black plague

Yersinia Pestis

Highly virulent pathogen that lives in small rodents and causes plague (black death) which is a life threatening bacterial infection

Black death Plague

Life threatening bacterial infection historically responsible for widespread pandemics with high mortality (>250 million deaths)

Y. Pestis Natural Reservoir and Biological vector

Rodents, in their blood stream and then flea is vector carrying the pathogen to mammals

Y. pestis biolfilms

Blocks the flea’s intestine and then the flea brings the pathogen up to their mouth when they bite the next host

Y. Pestis Transmission

Humans are accidental host transmitted by:

Bite from an infected flea (primary route)

Direct contact of handling dead infected mammals

Eating infected rodent meat

Y. pestis diseases depends

On route of infection

Bubonic plague, Septicemic plague, and Pneumonic plague 

Bubonic plague

Y. pestis inoculated into body site of flea bite, it travels thru the lymphatic system and replicates in the lymph, may progress to septicemic plague if untreated

Most common plague

Septicemia plague

Occurs when the infection spreads thru the bloodstream, advanced stages of bubonic plague, and death occurs from gram - septic shock

Pneumonic plague

Most virulent and least common form of plague, caused by spread to lungs from advanced bubonic plague (septicemic)

Only form spread person to person through respiratory droplets

Y. pestis Pathogenesis

Molecular pathogenesis complex due to insect (ambient) and mammalian (35-37°C) environments b/c optimal growth is at 20-28C

Examples of factors induced at shift to 37°C:

a) F1 protein capsule – antiphagocytic

b) Adhesins - Allow attachment to human cells

c) Type III secretion systems - Injection of proteins into host cells; cause cellular death

d) Yops (Yersinia outer proteins) – cytotoxic & down-regulate

Y. pestis Treatment

Rapid diagnosis and initiation treatment with an efficacious antibiotic within 24 hours of symptom onset is critical

– plague is a potentially fatal disease

Y. pestis prevention 

Keep free of rodents and fleas, antibiotics, sanitation and hygiene, and insect repellent

Bordetella Pertussis characteristics

Slow growing, aerobic, motile, encapsulated, fastidious coccobacillus, and a strict obligate human respiratory pathogen 

Pertussis

Highly contagious respiratory disease (whooping cough) caused by B. pertussis - severe, spasmodic coughing

Bordetella pertussis – Epidemiology

Highly contagious, infecting more than 90% of exposed susceptible persons 

  -Today >90% of the cases are in developing nations; most deaths are among infants

Bordetella Pertussis transmission

Human to human only by inhalation of infected airborne droplets is the primary mechanism of transmission

Bordetella Pertussis Virulence factors and pathogenesis

Bacteria bind ciliated respiratory epithelium of the upper airway (throat) and lungs, then attachment is mediate by adhesin, pertactin, and FHA, and then exotoxins are produces

Bordetella Pertussis Virulence factors Exotoxins

damage cells, impair cilia, trigger inflammation, increase mucus, immune evasion

• Pertussis toxin (PT) • Tracheal cytotoxin (TCT) • Adenylate cyclase toxin (AC)

Bordetella Pertussis Virulence factors Ciliated cells

Ciliated cells are destroyed causing a denuded mucosa w/o protective and functioning cilia

Leads body to resort severe coughing

Bordetella pertussis – Clinical Disease

Pertussis follows a prolonged course consisting of 3 overlapping stages:

1.Catarrhal, 2.paroxysmal, and 3.convalescent

1.Catarrhal

Non-specific cold-like symptoms develop ~1 week after infection

2.paroxysmal

Peak coughing; worsen symptoms due to progressively thickened mucus and damaged respiratory epithelium; inspiratory “whoop’

3.convalescent

pertussis symptoms gradually fade; secondary pneumonia possible

100 Day cough

Bordetella pertussis – Diagnosis

A. Pertussis symptoms usually diagnostic § Coughing paroxysms, inspiratory "whoop," or post-paroxysm vomiting

B. Isolation of B. pertussis from clinical specimen (Catarrhal stage)

C. Positive NAAT (polymerase chain reaction (PCR)) for B. pertussis

D. Contact with a laboratory-confirmed case of pertussis

Bordetella pertussis Treatment

A. Early antibiotic treatment critical (decreased complications, decreased spread)

B. Supportive care (humidifier, hydration, etc.)

C. Hospitalization may be required (esp. for infants/young children, compromised, elderly)

Bordetella pertussis – Prevention

Vaccination and hygiene

1.Yersinia overview

Focus on yersinia pestis → cause of plague (pestilence) and treated with antibiotics

2.Bordetella overview

Focus in bordetella pertussis → cause of pertussis (whooping cough) and treated with antibiotics or prevented by vaccine