Streptococcus Microbiology PDF

# Streptococcus ### Juli pravikant Microbiology department ## Gram-Positive Bacteria - Bacilli - Cocci - Aerobic - *Listeria* - *Bacillus* - *Corynebacterium* - Anaerobic - *Clostridium* - Aerobic - Catalase - *Streptococcus* - Optochin...

# Streptococcus ### Juli pravikant Microbiology department ## Gram-Positive Bacteria - Bacilli - Cocci - Aerobic - *Listeria* - *Bacillus* - *Corynebacterium* - Anaerobic - *Clostridium* - Aerobic - Catalase - *Streptococcus* - Optochin sensitivity - *Viridans strep* - *S. pneumoniae* (encapsulated) - *S. agalactiae* (group B) - *S. pyogenes* (group A) - *Staphylococcus* - Coagulase - *S. aureus* - Coagulase - *S. epidermidis* - Anaerobic - *Actinomyces* (not acid fast) - Branching filaments - *Nocardia* (weakly acid fast) ### Family: Streptococacceae ### Genus: *Streptococcus* "coiled berry" refers to bacteria characteristic grouping in chains. ### General Characteristics: - Gram positive cocci - Chains or pairs - Non motile - non spore forming - Some are capsulated - Facultative anaerobes - Fastidious - Catalase negative ## Classification of streptococci: ### 1. Classification based on hemolysis on blood agar(brown classification): - **Beta hemolytic streptococci**: colonies are surrounded by a zone of complete hemolysis of red blood cells with decolorization of Hb mainly cause by streptolysin produced by bacteria, beta hemolysis is more marked when the plate has been incubated an aerobically (pyogen, aglactiae). - **Alpha hemolytic streptococci**: colonies are surrounded by an area of partial hemolysis and green brown color due to oxidation of Hb to methemoglobin (pneumoniae, viridance). - **Gamma "non" hemolytic**: colonies show no haemolysis (Enterococcus and group D) ## 2.Classification based on Lancefield grouping of streptococci: - *Streptococci* produce specific carbohydrate (C carbohydrate), antigen in the cell wall that can be identified by using specific antisera. - *Streptococci* are divided into 21 group from A-H "and "K-V" (without I&J) these are known Lancefield groups. - Group (A,B,C,D &G )most common found associated with human infection. ### 3. Based on biochemical test. ### 4. Based on molecular genetics. ## Beta hemolytic streptococci(S.pyogen, S.aglactiae ### Streptococcus pyogen (A) ### General characteristic: - Gram positive cocci in chain. - Non-motile, non-spore forming, some strain are capsulated. - Aerobic and facultative anaerobic. - Temperature range from 22-42C, with optimum temperature 35-37C. - Fastidious. - Catalase negative ### Normal habitat: - *Streptococci* can found in water, dust, vegetation, milk and milk product. - *S.pyogenes* found as a part of URT normal flora. ### Virulence factor: - Factors that mediate adherence (colonization) - Extracellular toxins - Extracellular enzymes ### Factors that mediate adherence (colonization): - **M protein**: It is the most important virulence factor. - It is a surface protein which enables the bacteria to colonize skin and to escape phagocytosis. - It is immunogenic and divides *S. pyogenes* into about 80 M serotypes. - **Lipoteichoic acids**: - Facilitates adherence to pharyngeal epithelial cells - **F-protein**: - Function: Help in attachment ### Extracellular toxins: - **Streptolysins (toxins that haemolyze red cells):** - Streptolysin O (oxygen labile) is a highly immunogenic protein and induce specific antibody formation (anti- streptol - Streptolysin S (oxygen stable) is non immunogenic - **Erythrogenic toxin** - Responsible for the rash seen in scarlet fever ### Extracellular enzymes: - **Streptokinase**: Digests f brin clots - **Hyaluronidase**: Facilitates spread in the tissues by destroying hyaluronic acid. - **DNase**: hydrolyzes DNA ## Pathogenicity ### 1. Pharyngitis (score throat tonsillitis) - It is the commonest infection caused by *S. pyogsnes* - It is characterized by pain, redness and swelling of po pharynx, accompanied by greyish white tonsillar exud and fever. - The organism is usually transmitted via respiratory dro ### Scarlet fever - Mainly affect the children between 5-15 years old. - caused by erythrogenic toxin. - characterize by: pharyngitis, bright red rash on skin having sand paper like texture - Strawberry tongue. ### Puerperal fever: - This is a life threatening infection of the endometrium and surrounding structures complicating delivery or abortion. - Septicemia and toxic shock may occur ### Acute endocarditis: - This fatal condition can occur in individuals with normal or damaged heart valves. ## Post streptococcal disease - These are non-suppurative inflammatory conditions which occur as a result of immunologic response to streptococcal antigens. - They occur weeks following a local infection with *S.pyogenes* - and affect an organ that was not infected by the streptococci. - Rheumatic fever - Acute glomerulonephritis ### Rheumatic fever: - It is due to autoimmune reaction formation of antibodies to Streptococcal M protein, which cross react with antigens joints, heart and brain tissue. - It results in damage to heart muscle and valves. following subclinical pharyngitis in children. ### Acute glomerulonephritis: - It occurs due to deposition of antigen-antibody complexes on the glomerular basement membrane, provoking an inflammatory response that damages the kidney ## Streptococcus agalactiae (group B) - About 10-30% of pregnant women are colonized wi *S.agalactiae* in the genital tract. - Can be transferred to infant during delivery and sev infection Cause life threating infection to the newborri mants. - Most prevalent cause of neonatal sepsis which manifest as septicemia pneumonia and neonatal meningitis. ### General characteristic: - Gram positive cocci in chain. - Non-motile, non-spore forming, some strain are capsulated. - Aerobic and facultative anaerobic. - Temperature range from 22-42C, with optimum temperature 35-37C. - Non-Fastidious. ## Laboratory diagnosis ### Specimen collection: - Depend on the site of infection - *S.pyogenes* throat swab, pus and blood for C\S . Blood also required to estimation of ASO. - *S.agalactiae*: high vaginal swab, blood and CSF. ## Culture: ### *S.pyogenes*: - **Culture characteristic**: - Aerobic and facultative anaerobic Temperature range from 22-42C, with optimum temperature 35-37C. - Fastidious, grow on blood agar - **Special & selsective culture media**: - Crystal violet blood agar: - Selective agent: crystal violet dye (1%) - Use when isolation of *s.pyogenes* from throat or impetigo where the *s.aureus* are found. - PNF media: add polymxin B, neomycin and fucidic acid to blood agar. ### *S.agalactiae*: - **Culture characteristic**: - Aerobic and facultative anaerobic Temperature range from 22-42C, with optimum temperature 35-37C. - Non Fastidious, grow on blood agar, nutrient agar and some strain grow on MacConkey. - **Special culture media**: - Kanamycin blood agar: use to isolate group B from urogenital specimens. - Serum starch agar: use to detect the orange pigment of group B. ## Colonial morphology: - The 2 species produce beta-hemolysis on blood agar ## Indirect gram staining technique: - Gram positive cocci in chain. ## Biochemical test: ### 1. Catcalase test: - Negative (no active air bubble) ### 2. Bacitracin sensitivity test: - It used to distinguish between the ẞ-nemolytic streptococci *S.agalactiae* (bacitracin resistant)and *S.pyogenes* (bacitracin sensitive). - In blood agar inoculate the tested organism and then add disc contain 0.4 ug of bacitracin antibiotic, incubate for 24hr,observe inhibition zone around the antibiotic disc. - **Result**: - Zone of inhibition(sensitive)---- *s.pyogen* - No zone (resistant)----*s.aglactiae*. ### 3. Lancefield grouping: - Serological test used for classification of streptococci into 20 group designed by letter based on presence of specific antigen. - Using commercial latex agglutination kits, which allow rapid detection of streptococci. - Culture the organism in Todd Hewitt broth. - add drop from broth in card or slid& drop from commercial latex if agglutination reaction appear in A that mean La----- ### 4. Pyrrolidonyl Arylmidase (PYR) test: - To detect pyrrplidonyl aminopepidase enzyme which produce by group A streptococci & enterococcus. - **Principle**: Pyrrolidonyl amino peptidase enzyme hydrolysis L pyrrolidonyl-beta-naphthalmine, the beta- naphthalamine detect by use N-amino cinamaldehyde, which produce red color ### 5. Hippurate hydrolysis test: - Differentiates Group B streptococc (*S.agalactiae*) other ẞ hemolytic streptococci. - the hippuricase enzyme hydrolysis Na hippurate into glycine and benzoic acid, the reaction detect by add 0.2 ml of 3.5% nine hydrine That give purple color. ### 6. CAMP test (Christie, Atkine, Munch, Peterson): - the CAMP factor is an extracellular diffusible protein produce by *s.agalactiae*, that protein interact with staphylococcus aureus hemolysin to form complex which enhance the action of group beta haemolysin, form arrow head of haemolysis ## Antistreptolysin o test tube method - Is the antibody made against streptolysin O, an immunogenic, oxygen-labile hemolytic toxin produced by most strains of group A. - Measurement of ASO antibody titer is important in the investigation of post streptococcal diseases. - **Principle**: - If Ab (ASO) is present in patient serum, it will bind to SO thus not free to react with indicator RBC's, the result appears as no hemolysis. - If Ab is absent, Streptolysin O is free to react with RBC's resulting in hemolysis. - **Method**: - Take 5tube labled (1,2,3,4,5), add in each tube 500 microliter from normal saline. - Add 500 microliter from patient serum in tube no 1 mix & take from same tube 500 into second tube, take from2d tube 500 into 3d tube. - Add drop from (ASO) antigen, drop from Rbcs as indicator. - **Result**: neutralizing of antigen & antibody resulting show no haemolysis. ## Antimicrobial sensitivity - *S.pyogenes* sensitive to penicillin, erythromycin. - Resistance to polymyxin and nalidixic acid. ## No microbiology............ - I can't see any hope in the future.