8L-Pseudomonas-Haemophilus-Bordetella -Legionella pneumophila PDF

‫بسم هللا الرحمن الرحيم‬ Other Gram Negative Rods Dr. Mohamed Elmutasim Pseudomonas Dr. M. Elmutasim  Pseudomonas aeruginosa Diseases Wound infection UTI Pneumonia Sepsis. Nosocomial infections, especially in burn patients. Causes endocarditis in...

‫بسم هللا الرحمن الرحيم‬ Other Gram Negative Rods Dr. Mohamed Elmutasim Pseudomonas Dr. M. Elmutasim  Pseudomonas aeruginosa Diseases Wound infection UTI Pneumonia Sepsis. Nosocomial infections, especially in burn patients. Causes endocarditis in intravenous drug users.  Pseudomonas aeruginosa Characteristics Aerobic gram-negative rods. Non–lactose-fermenting. Pyocyanin (blue-green) pigment production. Oxidase-positive Habitat and Transmission Habitat is environmental water sources. Inhabits the skin, upper respiratory tract & colon. Transmission is via water aerosols, aspiration & fecal contamination.  Pseudomonas aeruginosa Pathogenesis Endotoxin is responsible for fever and shock associated with sepsis. Produces exotoxin A inactivates EF-2. Pili and capsule mediate attachment and inhibit phagocytosis, respectively. Glycocalyx-producing strains predominate in chronic infections in cystic fibrosis patients. Severe burns & neutropenia are predisposing factors  Pseudomonas aeruginosa Prevention Disinfection of water-related equipment in the hospital Handwashing, Prompt removal of urinary and intravenous catheters. There is no vaccine.  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. http://1.bp.blogspot.com/_Uf5f7SzC8gE/TRQWaMaybJI/AAAAAAAABZc/vTyTeOEg2jg/s1600/hi.jpg  Haemophilus influenzae Characteristics 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 and Transmission Habitat is the upper respiratory tract. Transmission is via respiratory droplets.  Haemophilus influenzae Pathogenesis 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.  Haemophilus influenzae Treatment Ceftriaxone is the treatment of choice for meningitis. Approximately 25% of strains produce β -lactamase. Prevention 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.  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.  Bordetella pertussis Pathogenesis 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 prevents lymphocytes from entering tissue, resulting in large numbers being retained in blood.  Bordetella pertussis Pathogenesis Tracheal cytotoxin damages ciliated epithelium of respiratory tract. Whooping cough 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.  Bordetella pertussis 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.  Bordetella pertussis Treatment Erythromycin. Prevention Acellular vaccine containing pertussis toxoid (recommended). Killed vaccine: contains whole organisms. Given to children in combination with diphtheria & tetanus toxoids (DTaP).  Legionella pneumophila Diseases Legionnaires' disease ("atypical" pneumonia). Clinical picture vary from mild influenzalike illness to severe pneumonia accompanied by mental confusion, nonbloody diarrhea & 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.  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.  Legionella pneumophila Pathogenesis 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. Legionella pneumophila  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) Legionella pneumophila growing on GVPC agar Charcoal yeast extract agar