Batterjee Medical College

Haemophilus influenzae Diseases Sinusitis, otitis media & pneumonia are common. Epiglottitis is uncommon. H. influenzae used to be a leading cause of meningitis, but vaccine has greatly reduced number of cases.

Batterjee Medical College Haemophilus influenzae Characteristics Habitat and Transmission Small gram-negative (coccobacillary) rods. Requires factors X (hemin) & V (NAD) for growth. Of six capsular polysaccharide types, type b causes 95% of invasive disease. Type b capsule is polyribitol phosphate. Habitat is the upper respiratory tract. Transmission is via respiratory droplets.

Batterjee Medical College Pathogenesis Haemophilus influenzae Polysaccharide capsule is the most important determinant of virulence. Unencapsulated ("untypeable") strains cause mucosal infections but not invasive infections. IgA protease is produced. Most cases of meningitis occur in children younger than 2 years of age, because maternal antibody has waned & immune response of child to capsular polysaccharides can be inadequate.

Batterjee Medical College Laboratory Diagnosis Haemophilus influenzae Gram-stained smear plus culture on chocolate agar. Growth requires both factors X & V. Determine serotype by using antiserum in various tests, e.g., latex agglutination. Capsular antigen can be detected in serum or cerebrospinal fluid.

Batterjee Medical College Treatment Haemophilus influenzae Ceftriaxone is the treatment of choice for meningitis. Approximately 25% of strains produce β -lactamase. Vaccine containing type b capsular polysaccharide conjugated to diphtheria toxoid or other protein is given between 2 & 18 months of age. Rifampin can prevent meningitis in close contacts. Prevention

Batterjee Medical College Bordetella pertussis Diseases Whooping cough (pertussis). Characteristics Small gram-negative rods. Habitat and Transmission Habitat is the human respiratory tract. Transmission is via respiratory droplets.

Batterjee Medical College Pathogenesis Bordetella pertussis Pertussis toxin stimulates adenylate cyclase by adding ADP-ribose onto inhibitory G protein. Toxin has two components: - Subunit A: has ADP-ribosylating activity - Subunit B:binds toxin to cell surface receptors. Pertussis toxin causes lymphocytosis in blood by inhibiting chemokine receptors prevents lymphocytes from entering tissue, resulting in large numbers being retained in blood.

Batterjee Medical College Pathogenesis Bordetella pertussis Inhibition of chemokine receptors occurs because pertussis toxin ADP-ribosylates inhibitory G protein prevents signal transduction within cell Extracellular adenylate cyclase is produced inhibit killing by phagocytes. Tracheal cytotoxin damages ciliated epithelium of respiratory tract.

Batterjee Medical College Bordetella pertussis Whooping cough is acute tracheobronchitis that begins with mild upper respiratory tract symptoms followed by severe paroxysmal cough, which lasts from 1 to 4 weeks. Paroxysmal pattern is characterized by series of hacking coughs, accompanied by production of copious amounts of mucus, that end with inspiratory "whoop" as air rushes past narrowed glottis. In adults, B. pertussis infection often manifests as paroxysmal cough of varying severity lasting weeks. The characteristic whoop is often absent. Adults with a cough lasting several weeks (often called the 100- day cough) should be evaluated for infection with B. pertussis.

Batterjee Medical College Laboratory Diagnosis Bordetella pertussis Gram-stained smear plus culture on Bordet- Gengou agar. Identified by biochemical reactions & slide agglutination with known antisera. PCR tests are both sensitive & specific. Colonies of Bordetella pertussis growing on Bordet-Gengou agar This fastidious bacterium grows as small colonies with a pearl-like sheen on this medium.

Batterjee Medical College Treatment Bordetella pertussis Erythromycin. Prevention Acellular vaccine containing pertussis toxoid & four purified proteins (recommended). Killed vaccine: contains whole organisms. Given to children in combination with diphtheria & tetanus toxoids (DTaP).

Batterjee Medical College Legionella pneumophila Diseases Legionnaires' disease ("atypical" pneumonia). Clinical picture vary from mild influenzalike illness to severe pneumonia accompanied by mental confusion, nonbloody diarrhea, proteinuria & microscopic hematuria. Cough with scanty & nonpurulent sputum. Most cases resolve spontaneously in 7 to 10 days, but in older or immunocompromised patients, infection can be fatal. Pontiac fever is mild, flulike form of Legionella infection that does not result in pneumonia.

Batterjee Medical College Legionella pneumophila Characteristics Gram-negative rods (stain poorly with standard Gram stain) Require iron & cysteine for growth in culture. Habitat and Transmission Habitat is environmental water sources. Transmission is via aerosol from the water source. Person-to-person transmission does not occur.

Batterjee Medical College Legionella pneumophila It has endotoxin. Predisposing factors include: - Older than 55 years of age - Smoking damages alveolar macrophages - High alcohol intake. -Immunosuppressed patients (renal transplant recipients) Organism replicates intracellularly, so cell- mediated immunity is important host defense. Pathogenesis

Batterjee Medical College Legionella pneumophila

Batterjee Medical College Legionella pneumophila Microscopy with silver impregnation stain or fluorescent antibody. Culture on charcoal yeast extract agar containing increased amounts of iron & cysteine. Urinary antigen provides rapid diagnosis. Serologically by detecting rise in antibody titer in patient's serum. Hyponatremia (serum sodium ≤ 130 mEq/L) is important laboratory finding that occurs more often in Legionella pneumonia than in pneumonia caused by other bacteria. Laboratory Diagnosis

Batterjee Medical College Legionella pneumophila growing on GVPC agar Charcoal yeast extract agar Legionella pneumophila H & E stained lung sections of patient from whom legionella pneumophila was isolated stained with CDC's modification of Dieterle silver impregnation procedure. small, blunt pleomorphic intracellular & extracellular bacilli which stain brown to black against a pale yellow background (500X)

Batterjee Medical College Legionella pneumophila Treatment Azithromycin or erythromycin. Rifampin can be added in severe cases. No vaccine or prophylactic drug is available. Prevention