Pathogens That Involve The Respiratory Tract

PATHOGENS THAT INVOLVE THE RESPIRATORY TRACT

I. BACTERIA A. STREPTOCOCCUS PYOGENES Characteristics: - Group A Beta hemolytic - Gram (+) cocci in chains -facultative anaerobes - Toxins and Enzymes: 1. Streptokinase 3. Erythrogenic toxin 2. Hyaluronidase 4. Streptolysin O

Disease: Streptococcal Pharyngitis (“Strep Throat”) > Clinical manifestations: - Acute bacterial infection - Sore throat, chills, fever, headache - beefy red throat - white patches of pus on pharyngeal epithelium - enlarged tonsils - enlarged and tender cervical lymph nodes - other manifestations: impetigo, scarlet fever

Complications: 1. Rheumatic fever -- fever, migratory polyarthritis, carditis -- 1-4 weeks after infection (usually after pharyngitis) 2. Glomerulonephritis – hypertension, edema of face and ankles, hematuria -- 2-3 weeks after infection (skin infection)

Reservoir: Humans Incubation Period: 1 to 3 days - Period of Communicability: 10 to 21 days (if untreated) - <24 hours (if with antibiotic) Transmission: human to human by direct contact - aerosol droplets and secretions - fomites Diagnosis: Clinical s/sx, throat culture (gold standard) - ASO titer (antistreptolysin O) Treatment: Penicillin G Amoxicillin Clindamycin Erythromycin Cephalosphorin Prevention and Control: personal hygiene and cleanliness - Standard precaution - prompt treatment of streptococcal infections

B. STREPTOCOCCUS PNEUMONIAE CHARACTERISTICS: - Gram (+) cocci in pairs or short chains - alpha hemolytic streptococci - virulence factors RESERVOIR: Humans TRANSMISSION: Colonization of nasopharynx - extensive close contact DISEASE: Pneumonia and meningitis - common cause in >5 yrs old and adults. - Bacteremia and URTI (otitis, sinusitis) DIAGNOSIS: Gram stain and culture, serologic testantigen identification TREATMENT: Penicillin, Erythromycin PREVENTION AND CONTROL: Vaccine

C. NEISSERIA MENINGITIDIS Characteristics: Gram (-) diplococci, capnophilic, facultative anaerobe --Virulence Factors: a. Capsule b. Endotoxin: Lipopolysaccharide (LPS) c. IgA1 Protease - cleaves IgA in half d. Can extract iron from transferring via a non-energy mechanism e. Pili adherence Reservoir: Humans Transmission: Nasopharyngeal carriers (10%) Droplet respiratory secretions Diseases: 1. Meningitis -- 6 months to 2 yrs. old -- fever, stiff neck (nuchal rigidity), vomiting, lethargy, altered mental status -- petecchial rash

2. Septicemia (Meningococcemia) -- fever, petecchial rash, hypotension -- fulminant meningococcemia -- death occurs within 6-8 hrs. Diagnosis: Gram stain of blood or CSF -- Culture: Thayer-Martin media (TM) -- Latex Agglutination Test (LAT) Treatment: Cephalosporin, Pen G, Chloramphenicol Prevention and Control: Respiratory isolation Chemoprophylaxis: Rifampicin and Ciprofloxacin Polysaccharide Vaccine

D. HAEMOPHILUS INFLUENZA TYPE B Characteristics: Gram (-) coccobacilli - non-motile, non-spore forming - facultative anaerobe - “blood loving” - Requires: 1. X factor (Hematin)—heat stable 2. V factor (NAD)– heat labile --Nicotinamide adenine dinucleotide (NAD) - Types: a, b, c, d, e, f (most invasive type: b) Diseases: 1. Meningitis - main cause in 6 mos - 3 y/o 2. Pneumonia - 2nd most common cause of CAP 3. Epiglottis 5. Sepsis 4. Septic arthritis 6. Cellulitis 7. Otitis media

Reservoir: Humans Transmission: airborne, droplets spread - direct contact with secretions, fomites Diagnosis: Culture - Agglutination assays - immunoelectrophoresis - ELISA (Enzyme-Linked Immunosorbent Assay) Treatment: - Ampicillin -Amoxicillin - Cephalosphorin Prevention and Control: Rifampicin - to decrease respiratory carriage - HiB vaccine - between 2-15 months old - avoid crowding - handwashing, standard precaution

E. BORDETELLA PERTUSSIS

Characteristics: --Gram (-) coccobacilli --non motile, obligate aerobes --Virulence factors: 1. Pertussis toxin 2. Extracytoplasmic adenylate cyclase 3. Filamentous hemagglutinin (FHA) - facilitates adherence to cilia of respiratory system 4. Tracheal cytotoxin - destroys cilia  impaired clearance of bacteria & mucus.

Reservoir: humans Transmission: Airborne via droplets produced by coughing Incubation Period: 6-20 days Disease: Pertussis (Whooping Cough) Stages: 1. Catarrhal stage - 1-2 weeks duration - similar to upper respiratory tract infection - low grade fever, runny nose, mild cough - Most contagious Stage 2. Paroxysmal stage - 2-10 weeks  severe, uncontrollable coughing - cough ends in a high-pitched indrawn breath (whoop) 3. Recovery or Convalescent Stage - within 4 weeks - patient no longer contagious

Diagnosis: Nasopharyngeal swab - culture: Bordet-Gengou agar or ReganLowe agar - Nucleic acid and immunodiagnostic procedures Treatment: -Erythromycin -Doxycycline -Azithromycin Prevention and Control: -Inactivated (heat-killed) pertussis vaccine - Droplet Precautions

F. CORYNEBACTERIUM DIPHTHERIAE Characteristics: - Gram (+) bacilli, facultative anaerobe - non-spore forming, non-motile - produce exotoxin (by bacteriophage) - A subunit - blocks protein synthesis by inactivating elongation factor (EF2) - B subunit – provides entry into cardiac and neural tissue Reservoir: Humans Incubation Period: 1-4 days to one week Disease: DIPHTHERIA - mild sore throat with fever - swollen cervical lymph nodes (“bull neck”) - Pseudomembrane forms on pharynx - Myocarditis (10%) , neural involvement

Diagnosis: - Nasopharyngeal and throat swab for culture - Loeffler’s medium - Cystine-tellurite medium (Tinsdale medium) - Schick test - test for susceptible individuals Treatment: - Antitoxin - Penicillin or Erythromycin Prevention and Control: - Diphtheria toxoid - Patient isolation and disinfection of fomites - Contact and droplet precautions

G. MYCOBACTERIUM TUBERCULOSIS Characteristics: - acid fast, weakly gram (+) - non motile, obligate anaerobe -virulence factors: 1. Cord factor 2. Complex lipids (e.g. mycolic acid, wax D, phosphatides) Diseases: 1. Pulmonary TB (Primary Complex) - often seen in children - localized to the middle and lower lung zones - GHON lesion/complex  small calcified nodules 2. Post-primary disease - adult type or reactivation or secondary tuberculosis - endogenous reactivation of latent infection

- localized to apical and posterior segment or upper lobes and superior segment of lower lobes - fever, night sweats, malaise, weight loss, cough, hemoptysis 3. Extrapulmonary TB a. TB lymphadenitis - >2.5 % of cases b. Pleural involvement (pleural effusion) c. Genitourinary TB – 15% of cases d. Skeletal TB (Pott’s disease) – 10% e. TB meningitis -- 5% f. GI TB g. Pericardial TB h. Miliary TB (disseminated TB) Reservoir: Humans Transmission: airborne, droplets - prolonged direct contact with infected persons - Bovine TB: infected cattle or ingestion of contaminated milk

Incubation Period: 4 to 12 weeks Diagnosis: demonstration of AFB in sputum specimen - culture: Lowenstein- Jensen Media - 3-6 weeks - DNA PCR (Polymerase Chain Reaction) - PPD (Purified Protein Derivative) or Mantoux test Treatment: Isoniazid (INH) Rifampicin (RIF) Directly Observed Therapy (DOT) Pyrazinamide (PZA) Ethambutol (EMB) Streptomycin (STREP) Prevention and Control: - Isolation and treatment of infected individuals - airborne precautions - BCG vaccine (70-80% effective)

H. MYCOPLASMA PNEUMONIAE Characteristics: Gram (-) motile, facultative anaerobe - no cell wall - pleiomorphic bacteria Reservoir: Humans Incubation Period: 6 to 32 days Transmission: droplet inhalation - direct contact with infected person - fomites Disease: primary atypical pneumonia - Clinical manifestations: headache, sore throat - cough ( dry  productive) - paucity of findings on chest examination is in marked contrast to prominence of CXR infiltrates

Diagnosis: test for antibodies - cold agglutinin - complement fixation test - sputum culture ---- “fried egg” colonies Treatment: most cases are mild (10-14 days) - Erythromycin - Clarithromycin -Azithromycin - Tetracycline Prevention and Control: - avoidance of crowded living and sleeping quarters - proper disposal of tissues and soiled articles - handwashing - - - droplet precautions

II. VIRUSES

A. COMMON COLD, ACUTE VIRAL RHINITIS, ACUTE CORYZA Pathogen: - Rhinovirus - Adenovirus - Coronavirus (also cause SARS) - Respiratory Syncytial Virus (RSV) - Influenza and Parainfluenza virus Reservoir: Humans Transmission: - Respiratory secretions by way of hands and fomites - Direct contact with or inhalation of airborne

Incubation Period: - 12 hours to 5 days (usually 48 hours) - communicable period: 24 hours before onset up to 5 days after onset Disease: - produces coryza (profuse discharge from nostrils) - runny eyes, sore throat, chilliness, malaise Treatment: Supportive Prevention and Control: - Handwashing - Sanitary disposal of oral and nasal discharges - Avoid crowding and contact with infected individuals - Disinfect eating and drinking utensils

B. INFLUENZA VIRUS Characteristics: - Orthomyxovirus - RNA virus - Influenza virus type A, B and C - Type A --- severe symptoms associated with epidemics and pandemics - Type B --- less severe, localized outbreak - Type C --- does not cause significant disease - Envelope contains: hemagglutinin (H) and neuraminidase (N) Reservoir: - Primary: Humans - Others: Pigs, ducks (avian)

Transmission: - airborne spread - direct contact with secretions Incubation Period: 1-3 days Disease: fever, chills, headache, myalgia, sore throat, cough, nasal discharge Diagnosis: Isolation of virus from pharyngeal or nasal secretions - Immunodiagnostic procedures Treatment: - supportive - Amantadine Prevention and Control: - Yearly vaccination - Good personal hygiene - Avoid crowded areas during epidemics - - - droplet precautions

C. MUMPS VIRUS Characteristics: - Paramyxovirus - RNA virus Reservoir: Humans Transmission: - droplet spread, saliva and fomites - direct contact with saliva of infected person Incubation Period: 14- 18 days - Communicable: 1-2 days before onset of parotitis to 5 days - no longer contagious after 9 days Disease: - Parotitis ( 30-40 %) - Unilateral or bilateral (2/3 bilateral) - can occur singly or with other salivary glands affected

Complications: - CNS involvement - aseptic meningitis – 50-60% of patients - encephalitis --- < 0.002% - Orchitis (testicular inflammation) - 50% of post pubertal males - sterility is rare - Oophoritis (ovarian inflammation) - 5% of post pubertal females - Deafness (1 per 20,000 cases) Diagnosis: isolation of virus from saliva, throat swab, CSF, urine - ELISA Treatment: Supportive Prevention and Control: live, attenuated mumps vaccine

III. FUNGI A. CRYPTOCOCCUS NEOFORMANS Characteristics: not dimorphic ( yeast form only) Disease: Cryptococcosis - Meningitis - Pneumonia - Skin lesions Reservoir: pigeon droppings Transmission: inhalation Diagnosis: Biopsy and culture Serology, skin tests Treatment: Amphotericin B Fluconazole

B. OTHERS Pathogens: Histoplasma capsulatum Blastomyces dermatitidis Coccidioides immitis - Dimorphic ( yeast and mycelial forms) Reservoir: bat droppings Transmission: inhalation Disease: Pneumonia Treatment: Itraconazole Amphotericin B