1 Streptococcus pneumoniae Staphylococci (Gram positive cocci) Lecture 38 Faculty: Dr. Alvin Fox

2 S. pneumoniaeS. pneumoniae −diplococci −Pneumococcus −autolysin −bile solubility test −optochin susceptibility −capsule −Quellung reaction −Polyvalent vaccine Staphylococcus aureusStaphylococcus aureus - coagulase (+) - MRSA (methicillin resistant S. aureus) - opportunistic diseases - food poisoning/enterotoxins - toxic shock syndrome/toxic shock toxin - exfoliative toxin/scalded skin syndrome cytotoxins - α, β, γ and δ cytotoxins - leucocidin - lipase - hyaluronidase - protein A - coagulase (–) - Staphylococcus epidermidis - Staphylococcus saprophyticus KEYWORDS

3 S. pneumoniae

4 leading cause of pneumonialeading cause of pneumonia –particularly young and old –member normal flora, nasopharynx –replication and spread after damage to upper respiratory tract (e.g. after the flu) bacteremiabacteremia meningitismeningitis middle ear infections (otitis media) - childrenmiddle ear infections (otitis media) - children

5 S. pneumoniae hemolyticα hemolytic pneumolysinpneumolysin –degrades red blood cells under aerobic conditions grows well on sheep blood agar grows well on sheep blood agar no group antigenno group antigen

6 Diagnosis - spinal fluid Diagnosis - spinal fluid direct Gram stainingdirect Gram staining detection of capsular antigendetection of capsular antigen

7 Autolysis – identification after growth Bile peptidoglycan lipoteichoic acid teichoic acid -choline autolysin autolysin Cell membrane

8 C polysaccharide Teichoic acid (C polysaccharide) –precipitates in serum –binds C-reactive protein

9 optochin resistant optochin sensitiveIdentification

10 Capsule prominentprominent –virulent strains anti-phagocyticanti-phagocytic carbohydrate antigenscarbohydrate antigens –highly variable among strains –numerous serotypes

11 Capsular vaccine ImmunityImmunity –serotype specific –to eradicate the organism in normal flora VaccineVaccine –a few major serotypes (polyvalent) Vaccination or the susceptible populationVaccination or the susceptible population –young children –elderly ImmunizationImmunization –major serotypes susceptible to change –population monitoring essential

12 Quellung reaction using antiserausing antisera capsule "fixed" capsule "fixed" visible microscopically visible microscopically

13 Pathogenesis Teichoic acidTeichoic acid –complement activation –large numbers of inflammatory cells at infection site

14 Therapy S. pneumoniaeS. pneumoniae – most strains susceptible to penicillin – resistance is common

15 STAPHYLOCOCCI Gram positiveGram positive Facultative anaerobesFacultative anaerobes Grape like-clustersGrape like-clusters Catalase positiveCatalase positive Major componentsMajor components of normal flora of normal flora -skin -nares

16 Staphylococcus aureus

17 One of commonest opportunistic infections, both hospital and community acquired infections, both hospital and community acquired: pneumonia osteomyelitis septic arthritis bacteremia endocarditis abscesses/boils other skin infections

18 Antibiotic therapy Resistance to penicillinResistance to penicillin –penicillinase Resistance to methicillinResistance to methicillin ‾modified penicillin binding protein ‾methicillin resistant S. aureus (MRSA) Vancomycin current drug of choicecurrent drug of choice resistance observed but uncommon at this timeresistance observed but uncommon at this time

19 Hospital infection control MRSA now such a problemMRSA now such a problem –monitoring by PCR of nasal swabs –eradication antibioticsantibiotics whole body antisepsiswhole body antisepsis

20 Food poisoning not an infectionnot an infection food contaminated by humans food contaminated by humans – growth of bacteria – production of enterotoxin onset and recovery both occur within few hoursonset and recovery both occur within few hours

21 Food poisoning VomitingVomiting nauseanausea diarrheadiarrhea abdominal painabdominal pain

22 Toxic shock syndrome.

23 Toxic shock syndrome feverfever rash rash desquamationdesquamation vomitingvomiting diarrhea diarrhea

24 Toxic shock syndrome Toxic shock toxinToxic shock toxin -Dissemination OrganismOrganism – no dissemination

25 S. aureus babiesbabies –scalded skin syndrome exfoliatinexfoliatin

26 Lytic exotoxins: toxinα toxin toxin (sphingomyelinase C)β toxin (sphingomyelinase C) toxin γ toxin toxinsδ toxins –detergent-like leucocidinsleucocidins

27 Protein A inhibits phagocytosis Protein A immunoglobulin Fc receptor BACTERIUM PHAGOCYTE

28 Spread tissue-degrading enzymestissue-degrading enzymes –lipase –hyaluronidase

29 Identification Sheep blood agar Sheep blood agar β hemolytic – β hemolytic – yellow pigmented(aureus) – yellow pigmented (aureus) fermentation mannitol fermentation coagulase-positive coagulase-positive phage-typing, rarely performed phage-typing, rarely performed

30 Staphylococcus epidermidis major member, skin flora opportunistic infection opportunistic infection - less common than S.aureus - less common than S.aureus nosomial infections nosomial infections - shunts, catheters artificial heart valves/joints artificial heart valves/joints

31 Identification Sheep blood agar – non-hemolytic – Non-pigmented Does not ferment mannitol Does not ferment mannitol Coagulase negative Coagulase negative

32 Several other coagulase negative staphylococcal species common on human skin some species cause opportunistic infection some species cause opportunistic infection

33 Staphylococcus saprophyticus urinary tract infections coagulase-negative species (and others) this coagulase-negative species (and others) – not usually differentiated from S. epidermidis

34 GRAM POSITIVE COCCI S. aureus Beta hemolytic mannitol yellow + - Staphylococcus (Clusters) Streptococcus (pairs & chains) Catalase BETA:BacitracinS. pyogenes (group A) CAMP/HippurateS.agalactiae (group B) Coagulase S.epidermidis Non-hemolytic mannitol white ALPHA:Optochin/Bile Solubility S. pneumoniae GAMMA OR ALPHA: BileEsculin 6.5%NaClGroup D Enterococcus BileEsculin6.5%NaClGroup D Non-Enterococcus Note: S. viridans is ALPHA hemolytic and negative for all the tests below Summary Figure (Identification Scheme) Hemolysis/Test