Lecture%20# 1 Microbiology 6th.ppt
- 2. GPC Staphylococcus Streptococcus Enterococcus 2
- 3. Staphylococcus (GPCs in clusters) Staphylococcus aureus S. epidermidis S. saprophyticus Streptococcus (GPCs in chains) Streptococcus pyogenes (Group A ) Streptococcus agalactiae (Group B) Streptococcus pneumoniae (Pneumococcus) Streptococcus viridans Enterococcus (Group D) 3
- 4. 1. In clusters (grapes like) or short chains 2. Catalase + ve 3. Facultative anaerobes 4. Grows on ordinary medium 5. Major components of normal flora – skin, nose & mucosa 6. Produces localized infections 7. Resistant to drying, Penicillin 1. In chains or in pairs 2. Catalase -ve 3. Obligate & facultative anaerobes, grows in 5-10% CO2 4. Fastidious – requires enriched medium like BA 5. Normal flora in throat, colon, female genital tract 6. Infections tend to spread 7. Delicate organism, sensitive to penicillin 4
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- 6. 6 Clinically Important Species Many species are medically important 1. S. aureus – Coagulase + ve Most virulent species Most common cause of bacterial infections, food poisoning & toxic shock syndrome 2. Coagulase –ve Staphylococci S. epidermidis – important cause of prosthetic implant infections S. saprophyticus – Urinary Tract Infection in young women
- 7. 7 Staphylococcus aureus – General features Coagulase positive Beta hemolytic colonies on BA Produces golden yellow pigment Highly resistant bacteria Can grow in the presence of 10 – 15% NaCl
- 8. 8 Virulence Factors 1. Toxins – cytolytic & superantigen exotoxins 2. Enzymes & 3. Cell associated polymers and surface proteins
- 9. Haemolysins - Cytolytic, lyse RBCs of various animal species Leucocidins - Kills leucocytes Enterotoxin A to E - Food poisoning Toxic shock syndrome toxin (TSST/ Enterotoxin F) – Toxic Shock Syndrome: rash, desquamation, multi organ failure Epidermolytic ( Exfoliative ) toxin A & B – SSSS: Staphylococcal scalded skin syndrome (epidermal splitting & exfoliation) 9
- 10. Catalase – enhance their survival in phagocytes by inactivating toxic H2O2 & free radicals released after the ingestion of staphylococci. Coagulase - Clots plasma, responsible for ‘tube coagulase test’, confirmatory test for S.aureus Hyaluronidase - Breaks down hyaluronic acid (connective tissue): initiation & spread of infection Fibrinolysin (Staphylokinase) - Lyses fibrin clots: spread of infection Nuclease - hydrolyses DNA Lipase – Lipolytic: infection of skin & subcutaneous tissue 10
- 11. Protein A - Antiphagocytic Clumping factor - bound coagulase, responsible for ‘slide coagulase test’, screening test for S.aureus 11
- 13. Cutaneous infections – Folliculitis (boils), furuncle, burns and wounds Deep infections – Osteomyelitis, abscesses, pneumonia, endocarditis, septicemia Toxin mediated infections – Staphylococcal scalded skin syndrome (SSSS), Toxic Shock Syndrome (TSS), Food poisoning (in 1-8hr, vomiting ,diarrhea, nausea, self limited ) 13
- 14. 14 Abscess Folliculitis Toxic shock syndrome SSSS
- 15. Specimens: wound swab, pus, blood, feces Microscopy: Gram stain - GPC in clusters Culture BA : beta hemolysis NA : golden yellow pigment Catalase positive Coagulase positive 15
- 17. 17 Major component of skin flora Nosocomial infections: device/ implant associated infections - shunts, catheters, artificial heart valves / joints, pacemaker Identification BA: Non - hemolytic Coagulase negative Prosthetic valve endocarditis
- 18. First developed resistance against Penicillin Resistance to penicillin is mainly attributed to the production of enzyme, penicillinase (beta- lactamase) To combat resistance due to penicillinase, Methicillin was developed & now methicillin resistant strains have evolved – MRSA 18
- 19. Important cause of Nosocomial infections post surgical wound infections blood stream infections ventilator associated pneumonia Patients with open wounds, invasive devices and weakened immune systems are at greater risk for infection Person to person spread – mainly from carriers (hospital staff, visitors), 25-30% carry in their nose. By contact with 1. colonized or infected patients 2. colonized or infected body sites of the personnel themselves, 3. devices, items, or environmental surfaces contaminated with body fluids containing MRSA. 19
- 20. Difficult to treat Prevention and infection-control strategies Screening of staphylococcal carriers among hospital staff Treatment of carriers with mupirocin, hexachlorophene Proper sanitary procedures – surface sanitation, hand washing (alcohol gels), personal protective measures Isolation of patients with open staphylococcal lesions * However carrier status prevents complete control Treatment of MRSA infection - Glycopeptides Vancomycin teicoplanin 20
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- 22. 22 Classification Based on O2 Aerobes Anaerobes Peptostreptococci Growth on BA α hemolysis β hemolysis γ hemolysis Incomplete hemolysis (green color) Complete hemolysis α / β / no hemolysis Strep. viridans Strep. pneumoniae Enterococcus fecalis Lancefield grouping specific C carbohydrate on cell wall Group A – U (21 groups) Griffith typing of Group A on proteins
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- 24. 24 Streptococcus pyogenes – virulence factors Antigenic – produce ASLO Streptolysin S (SLS) Exotoxins Oxygen stable , non-antigenic Damage cardiac cells Streptolysin O (SLO) Oxygen labile Streptococcal Pyrogenic Exotoxin (SPEs) Manifestation of scarlet fever Exoenzymes Streptokinase (fibrinolysin) / Streptodornase (DNAase) / Hyalarunidase
- 25. Respiratory infections – pharyngitis (sore throat), tonsillitis otitis media, sinusitis Skin & subcutaneous infections – pyoderma, cellulitis necrotising fasciitis (flesh eating bacteria) Non suppurative complications – Acute rheumatic fever – usually follows streptococcal pharyngitis Acute glomerulonephritis – usually follows pyoderma 25
- 26. Specimens: throat swab, pus, blood Microscopy :Gram stain - GPC in chains Culture: BA - beta hemolytic colonies Identification tests - Catalase Negative Bacitracin sensitive Penicillin sensitive ASO titre / DNAase B test 26 B B
- 27. Normal flora in lower GIT, female genital tract Pathogenicity Neonatal meningitis Puerperal sepsis Pneumonia 1
- 28. Specimens: CSF, blood, vaginal smears, urine Microscopy :Gram stain - GPC in chains Culture: BA - beta hemolytic colonies Identification tests Catalase negative Bacitracin resistance CAMP Test + Penicillin sensitive P B
- 29. 29 Group D Streptococcus Normal flora in GIT, lower genital tract Nosocomial / opportunistic pathogen Enterococcus – 2 imp. species E. fecalis E. faecium UTI, wound infection, endocarditis Resistance to cephalosporins, even vancomycin 1
- 30. 30 Lab diagnosis - Enterococcus Culture: BA - alpha / beta / no hemolysis Identification tests - Catalase Negative Specimens: urine, pus, blood Growth in 6.5% Nacl Penicillin resistance Microscopy: Gram stain - GPC in pairs or short chains Bile esculin positive
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- 32. Virulence factor – capsule Pathogenicity Otitis media, sinusitis - commonest Pneumonia Meningitis Other suppurative lesions - Pericarditis, conjunctivitis, arthritis, peritonitis Vaccine available for prevention – polyvalent polysaccharide vaccine 32
- 33. Specimen: CSF, blood, sputum, pus, swabs Microscopy: Gram stain – GPC in pairs, capsulated, lanceolate shaped Culture BA– alpha hemolytic colonies Identification tests Catalase –ve Optochin sensitive Bile solubility 33
- 34. Normally present on teeth, throat, colon & female genital tract Pathogenicity – Endocarditis & Dental caries 34 Alpha hemolytic streptococci Streptococcus viridans 1
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- 36. 36 Overview of the Medically Important Gram Positive Cocci Family, Genus, species Characteristics Clinical manifestations Staphylococcaceae Cocci in cluster; catalase-positive Staphylococcus aureus Coagulase +ve, yellow-pigmented colonies Pyogenic infections, toxicoses S. epidermidis Coagulase -ve, whitish colonies, normal flora Foreign body infections Streptococcaceae Cocci in chains and in pairs, catalase- negative Streptococcus pyogenes Cocci in chains, Lancefield group A, β - hemolysis Tonsillitis, scarlet fever, skin infections S. pneumoniae Diplococci, α-hemolysis Pneumonia, otitis media, Sinusitis S. agalactiae Chain-forming cocci, group antigen B, β- hemolysis Meningitis/sepsis in Neonates S. viridans Cocci in chains, α-hemolysis Endocarditis, dental caries Enterococcaceae In chains & pairs, α, β, or γ-hemolysis, group antigen D, catalase -ve Flora of intestines of humans and animals Enterococcus faecalis Enterococcus faecium Aesculin-positive, growth in 6.5% NaCl, pH 9.6 Opportunistic infections