bacterial pharyngitis - microbiology
corynebacterium diptheriae is categorized as
-type of actinomycetes which is a gr+ non endospore forming bacilli
symptoms of gonococcal pharyngitis
-usually asymptomatic, possible sore throat
acute pharyngitis
-viruses most common cause (90%) so antibiotics not needed most of the time -GAS most common bacterial cause
viral pharyngitis presentation
-conjunctivitis -coryza -cough -diahhrea -hoarseness -discrete ulcerative stomatitis -viral exanthema
diagnosis of goconoccal pharyngitis
-culture -PCR -gram stain pharyngeal swab NOT used because commensal Neisseria spp. in oropharynx
diagnosig pharyngitis - center criteria
-tonsillar exudates -tender anterior cervical adenopathy -fever by history -absence of cough ***likelihood of GAS increases with number of criteria
s. pyogenes cytotoxins
-B hemolysis causes by either of 2 hemolysins -streptolysin S (aerobic - nonimmunogenic) -streptolysin O (anaerobically - antigenic: ASO serologic test)
corynebacterium diptheriae
-Gr+ club shaped -not normal microbiota (5% carriers where endemic) -nonacid fast, nonmotile, unencapsulated -nonendospore forming -aerobe to facultative anaerobe -catalase positive
s. pyogenes
-Gr+ cocci chains -fastidious blood agar + CO2 -hyaluronic capsule -catalase negative -Beta hemolysis -bacitiracin sensitive vs. bacitracin resistant S. agalactiae (GBS)
Neisseria
-Gr- diplococci -human reservoir 'nonmotile' -Neisseria meningitidis has capsule -aerobes to facultative anaerobes -differ in carb. utilization -oxidase + -many catalase +
gonococcal virulence factors
-IgA1 protease -facultative intracellular in epithelial cells, PMNs -antigenic and phase variation in opa's, pili, LOS -LOS bind to host sialic acid -outer membrane blebbing
s. pyogenes adhesins
-M protein in cell wall is antiphagocytic with over 100 serotypes -adhesion binds to fibronectin, keratinocytes -body eventually develops antibody
treatment of diphtheria
-antitoxin (immediately!) + erythromycin or penicillin + airway support -diphtheria antitoxin available in U.S. only through CDC patient isolation -after recovery→ toxoid immunization
growth of C. diptheriae
-blood agar -loeffler medium: differential to enhance metachromatic granule formation and to look for proteolysis -tinsdale agar: differential and selective to distinguish from commensal corynebacteria
diagnosis of diphtheria
-clinical, history -definitive= culture membrane + positive toxin assay (PCR)
virulence factor of cornyebacterium dyptheria
-dipheria toxcin -AB exotoxin encoded by lysogenic B-phage -ADP ribosylates elongation factor 2 (EF-2) to inhibit protein synthesis -toxin production repressed under high iron concentrations -heart and neural has abundant receptor
transmission/pathogenesis of GAS pharyngitis
-direct contact (usually hands) -attaches to mucosal epithelium (M protein, F protein) -protection from phagocytosis (capsule, SpyCEP, C5a peptidase, SpeB) -invasion mucosa
growth of N gonorrhoeae
-fastidious -Thayer martin (chocolate agar + antibiotics) used if taking from pharynx where normal microbiota is present -chocolate if from a sterile site
s. pyogenes immune evasion
-hyaluronic acid capsule -ScpCEP (cell envelope proteinase) cleaves IL-8 and prevents neutrophil recruitment -C5a peptidase blocks phagocyte chemotaxis
diagnosing pharyngitis
-if have <3 then = no diagnostic testing or antibiotic -if have ≥3 then =diagnostic testing with sample of posterior pharynx, tonsils to perform rapid antigen detection test (RADT) or culture
if RADT negative in children, adolescents
-if negative back up with throat culture
rapid antigen detection tests (RADT)
-immunoassay for group A antigen - around 15 min, in office -less sensitive than culture -negatives confirmed by culture in children, adolescents
microcopy of C. diptheriae
-metachromatic granules (stored polyphosphates)
pathogenesis C. diptheriae
-multiply locally to secrete diphtheria toxin causing local damage (necrosis and inflammation) -pseudomembrane= (bacteria + WBCs + RBCs + dead cell debris + fibrin) adheres firmly -if severe disease, absorption and circulation of diphtheria toxin -myocarditis, neurotoxicity ***toxin can circulate anywhere but prefers cardiac and neural because more receptors there
streptococcus pygoenes disease manifestations
-necrotizing fasciitis -pharyngitis -pneumonia -lymphangitis -scarlet fever -cellulitis
throat culture for GAS
-on blood agar with bacitracin disk -gold standard -24-48 hours
gonococcal pharyngitis pathogenesis/transmission
-oral sex -attachment (pili, opa) -invasion (facultative intracellular in PNM's, epithelial) -evasion of immune (facultative intra, IgA1 protease, blebbing) -possible dissemination (DGI) leading to septic arthritis and petechial skin lesion
Neisseria gonorrhoeae
-port of entry: genital tract (also oral anal sexual contact) -type of infection: pyogenic -no polysaccharide capsule -maltose oxidation negative -no available vaccine
accurate diagnosis and antimicrobial therapy important for GAS pharyngitis to
-prevent acute rhematic fever -prevent suppurative complications (peritonsillar abscess) -reduce transmission
s. pyogenes - superantigens
-pyrogenic exotoxins SpeB -exotoxin B degrades immune proteins -non specific activation of T cells resulting in polyclonal T cell activation and massive cytokine release leading to inflammation and shock
transmission C. diptheriae
-respiratory droplets -skin contact
Neisseria gonorrhoeae
-small Gr- diplococcus -obligate human pathogen -fragile: rapidly killed by drying, sunlight, moist heat, many disinfectants -facultative intracellular -lipooligosaccharide (LOS) -aerobe to facultative anaerobe -oxidase + -catalase + -oxidizes glucose
symptoms of respiratory diphtheria
-sore throat, low-grade fever -pseudomembrane of tonsils, pharynx, or nose - marked cervical lymphadenopathy= 'bull neck'
s. pyogenes extracellular spreading factors
-streptokinase: lysis of clots -hyaluronidase: facilitate spread -DNases A-D: depolymerize free DNA in pus
bacterial pharyngitis presentation
-sudden onset of sore throat -age 5 to 15 years -fever -headache -nausea, vomiting, abdominal pain -tonsillopharyngeal inflammation -patchy tonsillopharyngeal exudates -palatal petechial -tender nodes (anterior cervical adentitis) -winter and early spring presentation -scarlatiniform rash
tinsdale agar
-tellurite inhibits growth most URT bact. and Gr- rods -C. diphtheriae reduces potassium tellurite to metallic tellurite → gray to black color
bacterial pharyngitis due to mainly
1. S. pyogenes (normal in small percent microbiota) 2. N. gonnherrea (not normal microbiota) 3. conebacterium (not normal microbiota except in some endemic places)
prevention of diphtheria
DTaP less than 7 Tdap bigger than 7
most common cause of bacterial pharyngitis
GAS
major complications with respiratory diphtheria
airway obstruction myocarditis (causes most mortality) polyneuritis
lives in underdeveloped country
corynbebacterium diptheriae
unimmunized
corynbebacterium diptheriae
clue of oral sesxual activity
most likely Neisseria gonorrhoeae
if RADT negative in adult
no throat culture unless patient at higher risk for severe infection