Small Gram Negative Coccobacillus Bordetella and Haemophilus

Bordetella pertissis

• minute, encapsulated coccobacillus, strictly aerobic

• causes pertussis or whooping cough, a communicable childhood affliction

• acute respiratory syndrome

• often severe, life-threatening complications in babies

• reservoir - apparently healthy carriers

• transmission by direct contact or inhalation of aerosols

• virulence factors

  • receptors that recognize and bind to ciliated respiratory epithelial cells- pertactin, filamentous hemagglutinin, fimbria

  • loss of ciliary mechanism leads to buildup of mucus and blockage of the airway - tracheal cytotoxin

  • localized tissue destruction: dermonecrotic toxin

  • toxins that destroy and dislpdge ciliated cells

  • systemic toxicity: pertussis toxin - inactivates adenylate cyclase- increase in cAMP - increase in respiratory secretions and mucous production, swelling in airways (whopping sound)

  • adenylate cyclate toxin: blocks phagocytes from migrating to infection site

• vaccine - DTaP - acellular vaccine contains toxoid and other Ags

Whooping Cough

• incubation period: 7-10 dats

• 3 stages of the disease: catarrhal stage (resembles the common cold; lasts for 2 weeks), progressing to the paraxysmal stage (repetitive coughs followed by inspiratory whoops - pertussis toxin; lasts 1-6 weeks), then the convalescence stage (diminishing paroxysms and secondary complication (pneumonia, seizures and encephalopathy; lasts 2-3 weeks)

Diagnosis

• culture swab taken from nasopharynx

• identification of bacteria by polymerase chain reaction

• direct fluorescent antibody

• serology: antibody response

Vaccine

• DTAP vaccine: diphtheria, tetanusm pertussis

• > 90% effective

• needs boosters in elderly

Haemophilus: General Characteristics

• small gram negative coccobacilli

• facultative anaerobic

• 3 species of medical importance:

  • H. influenza

  • H. ducreyi

  • H. aegyptius

Haemophilus influenzae

• small gram negatuve coccobacillus

• facultative anaerobic

• lives in mucous membranes of humans

  • nonencapsulated (40-80% children and adults); capsulated (3-5 children)

• a fastidious organism, H.influenzae will only grow on media with available factor X (hemin) and factor V (vitamin-NAD), like chocolate agar

• satellite testing for H. influenzae: grows in the hemolysis zone with S. aureus

Virulence Factors

• capsulated strains: six serotypes - type B causes 95% of infections

  • polysaccharide capsule: antiphagocytic

  • attach to epithelial cells in airways

  • pili and adhesion proteins (HMW1 and HMW2)

  • lipooligosacchardies (LOS) in outer membrane: inhibits the self cleaning mechanism- mucociliary clearance

  • IgA protease

  • causes invasive infections

• vaccine for b serotype

• unencapsulated strains - untypeable

  • attach to epithelial cells in airways

  • lipooligosaccharides (LOS) in outer membrane: each time they infect a cell

  • phase variation

  • IgA protease

  • biofilms

  • cause infection of mucosal surfaces by direct extension

    • otitis media

    • sinusitis

    • bronchitis

H. influenzae: infection

• risk factors for Type B:

  • children

  • splenectomy

  • malignancies

  • deficiency in complement proteins

  • acute viral infection: influenza virus

• risk factors for nontypable:

  • children

  • immunocompromised

  • acute viral infection: influenza virus

  • underlying lung condition

Haemophilus influenzae

• epiglotitis

  • fever

  • sorethroat

  • difficulty speaking

• meningitis

  • occurs mostly in children (6 months to 4 years)

  • fever, lethargy

  • vomiting

  • soreneck

  • altered mental status

Haemophilus influenzae Pneumonia

• nontypable stain major concern

• symptoms: fever, chills. chest pain. cough, shortness of breath

• diagnosis: isolation; special media for nutritional requirements

• treatment: cephalosporins - growing beta lactam resistance

Haemophilus influenzae Vaccine

• the Hib conjugate vaccien is an inactivated vaccine

• it is made by chemically bonding to a polysacchardie (sugar) to diphtheria toxoid

• this long chain of sugar molecules makes up the surface capsule of the bacterium.

• since the vaccine, cases of this type of meningitis have been decreasing

  

Chancroid

• caused by gram0negative coccobacillus

  • Haemophilus ducreyi

• obligate human pathogen

• soft chancres on the genitals or other areas associated with sexual contact

• painful, open sores that may bleed or produce fluid that is highly contagious

• sexually transmitted

• antibiotic treatment

Bacterial Conjuctivitis: H. aegyptius