Streptococci Student Notes PDF

DAVAO DOCTORS COLLEGE MEDICAL LABORATORY SCIENCE DEPARTMENT STUDENT NOTES: MICRO 1 STREPTOCOCCI GENERAL CHARACTERISTICS: ✓ Streptococcus & Ent...

DAVAO DOCTORS COLLEGE MEDICAL LABORATORY SCIENCE DEPARTMENT STUDENT NOTES: MICRO 1 STREPTOCOCCI GENERAL CHARACTERISTICS: ✓ Streptococcus & Enterococcus spp. belong to the family SMITH AND BROWN CLASSIFICATION Streptococcaceae ✓ members of both genera are CATALASE (-), GRAM (+) Alpha partial S. pneumoniae COCCI hemolytic hemolysis of S. viridans ✓ smear: usually arranged in PAIRS or CHAINS, cocci in RBC pairs (lancet shaped) greenish ✓ BAP: grayish, pinpoint with mucoid colonies discoloration ✓ Are facultatively anaerobes EXCEPT peptostreptococci, surrounding (obligate anaerobe) bacterial colony ✓ Carbohydrates are metabolized fermentatively with lactic acid as the major end product; gas is not produced. Beta complete S. pyogenes; ✓ Some species are capnophilic, requiring increased hemolytic hemolysis of S. agalactiae concentration of carbon dioxide, whereas the growth of RBC other species is stimulated by increased CO2, but CO2 is clear zone of not required. hemolysis surrounding CLASSIFICATION OF STREPTOCOCCI & ENTEROCOCCI: bacterial colony Smith & Brown Classification - based on hemolytic reaction in BAP Gamma non-hemolytic S. faecalis Bergey’s/ Academic Classification hemolytic no hemolysis of - based on its thermal/ temperature requirement RBC Lancefield’s Classification - based on the presence of serologically active carbohydrate C- polysaccharide (cell wall CHO) SPECIES SMITH & BROWN’S LANCEFIELD CLASSIFICATION GROUP BERGEY’S ACADEMIC CLASSIFICATION CLASSIFICATION Streptococcus NONE CLASSIFICATION THERMAL EXAMPLES pneumoniae REQUIREMENT ΑLPHA- HEMOLYSIS Viridans group NONE VIRIDANS Grows at 45°C and S. salivarius, S. 37°C mutans, S. sanguis Enterococcus D spp. LACTIC Grows at 10°C and S. cremoris, S. lactis Streptococcus A 37°C pyogenes ENTEROCOCCI Grows at 37°C, 45°C, S. faecalis Streptococcus ΒETA- HEMOLYSIS B and 10°C agalactiae PYOGENIC Grows at 37°C S. pyogenes Streptococcus C Majority of pathogenic dysagalactiae Streptococci Enterococcus D spp. Enterococcus GAMMA- D spp. HEMOLYSIS DDC Medical Laboratory Science Program | 2020-2021 Prepared by: Rachel Ann O. Eromon, RMT Group A STREPTOCOCCI  Streptococcus pyogenes Fever, rash, shock, bacteremia, respiratory failure (30% death -the most virulent species of Streptococcus for humans rate) -obligate human parasite -person to person; spread by respiratory secretions Post-streptococcal Diseases: - causes strep throat, rheumatic fever, post-streptococcal Acute rheumatic fever glomerulonephritis, scarlet fever Acute glomerulonephritis - beta hemolytic -Preceeded by skin or respiratory infections -Represents a hypersensitivity response -Immune-mediated MAJOR VIRULENCE FACTORS: 1. Capsule: anti-phagocytic DIAGNOSTIC LABORATORY TESTS 2. M protein: (surface fuzz on cell wall) A. MICROSCOPIC: gram (+) cocci in pairs or chains -precipitates fibrinogen B. CULTURE: 18-24 hrs. @ 37C -clumps platelets & WBCs, inhibits migration of WBCs ▪ BAP: -hemolytic, discoid, matte or glossy -inhibits activation of complement colonies -Anti-phagocytic ▪ Grows in 10% CO2 3. IgG & IgA-binding proteins: C. BIOCHEMICAL : -Binds to Fc region of IgG or IgA ▪ Catalase (-) 4. C5a protease: -cleaves C5a component of complement Diagnostic Laboratory Tests: -inhibits neutrophil chemotaxis in vitro 1. Taxo A/ Bacitracin Disk test 5. Lipoteichoic acid: (major cons. of G+ cell wall) Principle: The antibiotic bacitracin inhibits the synthesis of bacterial -Attachment of organism to epithelial cells cell walls. A disk (TaxoA) impregnated with a small amount of 6. Group-specific cell wall antigen: bacitracin (0.04 units) is placed on an agar plate, allowing the -basis of serologic grouping antibiotic to diffuse into the medium and inhibit the growth of TOXINS & ENZYMES: susceptible organisms. After incubation, the inoculated plates are Streptokinase: plasminogen to plasmin examined for zones of inhibition surrounding the disks. Streptodornase: DNAse; depolymerizes DNA Results: Hyaluronidase (spreading factor) (+) = any ZOI >10 mm (susceptible) Pyrogenic Exotoxins: erythrogenic toxins (-) = no ZOI (resistant) -A, B, C -Associated with strep TSS & scarlet fever 2. PYR Test: Diphosphopyridine Nucleotidase Principle: L-pyrrolidonyl arylamidase hydrolyzes the L-pyrrolidonyl- -Associated with the organism’s ability to destroy WBCs β-naphthylamide substrate to produce a β-naphthylamine. The β- Hemolyins naphthylamine can be detected in the presence of N,N- Streptolysin O (SLO) methylaminocinnamaldehyde reagent by the production of a bright Oxygen labile red precipitate. responsible for subsurface hemolysis (BAP) Results: destroys WBC & RBC (hemolysis) (+) = bright cherry red color highly antigenic / immunogenic (-) = no color change/ light orange Streptolysin S (SLS) Oxygen stable responsible for surface hemolysis (BAP) SCARLET FEVER SUSCEPTIBILITY TESTS Elaborated by serum 1. Dick’s Test: Non-antigenic/ non- immunogenic ✓ 0.1ml toxin (test arm) & 0.1ml toxoid (control arm) ✓ Observe for 24 hrs. Pyogenic Diseases: ✓ (+) redness in test arm Impetigo Erysipelas skin infections 2. Schultz-Charlton Test Cellulitis ✓ Inject anti-toxin into test arm Streptococcal Pharyngitis ✓ (+) fading of rashes ✓ Neutralization of erythrogenic toxin Toxigenic Diseases: Necrotizing fasciitis Group B STREPTOCOCCI Scarlet Fever Streptococcus agalactiae Streptococcal Toxic Shock Syndrome: has polysaccharide capsule (w/ sialic acid) Anti-phagocytic S. pyogenes grows in infected wound inhibits complement activation  able to mimic host molecules, enhancing pathogenicity. Bacteria enter bloodstream & produce exotoxin A Beta hemolytic (SLS-like) DDC Medical Laboratory Science Program | 2020-2021 Prepared by: Rachel Ann O. Eromon, RMT  Colonize: URT, GIT, vagina UTI, bacteremia, endocarditis, abscesses, wound infection bovine mastitis neonatal meningitis & septicemia Diagnostic Laboratory Tests: Adults: GBS is part of the normal vaginal and/or GIT flora 1. Bile Esculin Test in 20-30% of adults. Principle: Gram-positive bacteria other than some streptococci and Children: more susceptible than adults enterococci are inhibited by the bile salts in this medium. Organisms Infants/ Neonates: capable of growth in the presence of 4% bile and able to hydrolyze -Organisms ascends from the vagina and infects the esculin to esculetin. Esculetin reacts with Fe3+ and forms a dark amniotic fluid through the placental membranes. brown to black precipitate. -passage through the birth canal Results: (+) = Growth and blackening of the agar slant Diagnostic Laboratory Tests: (-) = Growth and no blackening of medium/ No growth 1. CAMP Test (Christie-Atkins-Munch-Peterson) in BAP Principle: Certain organisms (including group B streptococci) 2. 6.5% NaCl Test/ Salt Tolerance Test produce a diffusible extracellular hemolytic protein (CAMP factor) Principle: that acts synergistically with the beta-lysin of Staphylococcus aureus The salt tolerance test is a selective and differential medium. to cause enhanced lysis of red blood cells. The group B streptococci Enterococci are resistant to high salt concentration. A heart infusion are streaked perpendicular to a streak of S. aureus on sheep blood broth containing 6.5% NaCl is used as the test medium. This broth agar. also contains a small amount of glucose and bromcresol purple as Results: the indicator for acid production. (+) = arrowhead hemolysis Results: (-) = no enhancement of hemolysis (+) = turbidity (-) = no turbidity 2. Na Hippurate Hydrolysis Principle: The end products of hydrolysis of hippuric acid 2 Classifications: by hippuricase include glycine and benzoic acid. Glycine is Species 6.5% Penicillin PYR deaminated by the oxidizing agent ninhydrin, which is reduced during NaCl resistance the process. Enterococcal S. faecalis, With R (+) Procedure: group S. durans, growth S. faecium, S. avium Non S. bovis, No S (-) enterococcal S. equinus growth group BEM SALT TOLERANCE Results: + + Enterococci (+) = Deep purple color - - Non-enterococci (-) = Colorless or slightly yellow pink color - - Non-Group D Streptococci Group C & G STREPTOCOCCI Streptococcus pneumoniae - B-hemolytic except S. dysgalactiae a.k.a. DIPLOCOCCUS or PNEUMOCOCCUS - May cause severe pharyngitis followed by bacteremia and formerly Diplococcus pneumoniae metastatic infection BAP: α hemolytic & mucoid colonies young colonies: “DOME-SHAPED” or lancet-shaped S. equisimilis: produces streptokinase & SLO old colonies: DIMPLE-SHAPED or DONUT SHAPED S. equi colonies may closely resemble colonies of VIRIDANS S. zooepidemicus: associated w/ post strep GMN acquired after STREPTOCOCCI drinking MILK Encapsulated, non-motile, non-spore forming, facultative S. dysgalactiae anaerobe Capnophilic; fastidious Group D STREPTOCOCCI Enterococcus VIRULENCE FACTORS: Normal GIT and fecal flora a. POLYSACCHARIDE CAPSULE E. faecalis and E. faecium - principal virulence factor for its pathogenesis Grows on bile esculin media b. ENZYMES γ-hemolytic or α-hemolytic Neuraminidase: degrades surface structure of host May be weakly catalase (+) DDC Medical Laboratory Science Program | 2020-2021 Prepared by: Rachel Ann O. Eromon, RMT  Proteases: facilitate bacterial colonization on mucosal TEST Pneumococci Viridans surfaces by eliminating immunoglobulins (IgA, IgG and IgM) c. AUTOLYSIN Mouse Virulence Test S (dies) R (within 16-48 hrs.) - facilitates the release of pneumolysin O & other toxic proteins or inflammatory substances from cells Inulin Fermentation Fermenter Non-fermenter d. PNEUMOLYSIN O Test - O2 sensitive toxin & cytolytic for cells A. facilitates host adherence (colonization) Bile Solubility Test Soluble (broth Insoluble (turbid) B. damages host cells (invasion) clearing) C. interferes with the host immune response (infection) Optochin Test S (≥ 14mm) R Epidemiology, Pathogenesis & Clinical Manifestations Neufeld- Quellung + (swollen) - ✓ Present in the nasopharynx: Reaction (Capsular o 10% of healthy adults Swelling) o 40% of asymptomatic children ✓ RT  sinuses & middle ear  sinusitis & otitis media Quinidine S R ✓ community-acquired bacterial pneumonia; most common in U.S. (rusty sputum) Viridans streptococci ✓ 2nd most common cause of bacterial meningitis (Heterogenous Group of Streptococcus: No Lancefield antigen classification) S. pneumoniae vs. Viridans: S. salivarius Diagnostic Laboratory Tests: S. sanguis S. mitis 1. Mouse Virulence Test S. intermedius 2. Inulin Fermentation Test S. mutans 3. Bile Solubility Test S. constellatus Principle: Bile or a solution of bile salt (e.g. sodium desoxycholate) rapidly -BAP: α-hemolytic w/ greenish discoloration lyses pneumococcal colonies. -Normal URT biota Results: -seen in nasopharynx & gingival crevices; female genital tract; GI (+): Broth clearing tract (-): Turbid 4. Optochin Test 3 Main Types of Infection: Principle: Dental Infections: Optochin is an antibiotic that interferes with the ATPase and production of adenosine triphosphate (ATP) in microorganisms. The -bind to teeth & ferment sugar = acid → dental caries Optochin-impregnated disk (TaxoP) is placed on a lawn of organism Endocarditis: on a sheep blood agar plate, allowing the antibiotic to diffuse into the -implanted on endocardial surfaces of the heart (damaged medium. The antibiotic inhibits the growth of a susceptible organism, heart valves) → cling to valves = sub-acute bacterial creating a clearing, or zone of inhibition, around the disk. endocarditis Results: Abscesses (+) = susceptible -S. intermedius, S. constellatus, S.anguinosus (-) = resistant -form abscess in brain or abdominal organs Equivocal = any zone of inhibition