1 Streptococcus pneumoniae Streptococcus pneumoniae Staphylococci Staphylococci (Gram positive cocci) (Gram positive cocci) Lecture 38 Lecture 38 Faculty: Dr. Alvin Fox
Dec 22, 2015
1
Streptococcus pneumoniaeStreptococcus pneumoniae StaphylococciStaphylococci
(Gram positive cocci)(Gram positive cocci)Lecture 38Lecture 38
Faculty: Dr. Alvin Fox
2
• S. pneumoniaeS. pneumoniae
− diplococcidiplococci
− PneumococcusPneumococcus
− autolysinautolysin
− bile solubility testbile solubility test
− optochin susceptibilityoptochin susceptibility
− capsulecapsule
− Quellung reactionQuellung reaction
− Polyvalent vaccine Polyvalent vaccine
• Staphylococcus aureusStaphylococcus aureus- coagulase (+)- coagulase (+)- MRSA (methicillin resistant - MRSA (methicillin resistant S. aureusS. aureus))- opportunistic diseases- opportunistic diseases- food poisoning/enterotoxins- food poisoning/enterotoxins- toxic shock syndrome/toxic shock toxin- toxic shock syndrome/toxic shock toxin- exfoliative toxin/scalded skin syndrome- exfoliative toxin/scalded skin syndrome- α, β, γ and δ cytotoxinscytotoxins- leucocidin- leucocidin- lipase- lipase- hyaluronidase- hyaluronidase- protein A- protein A- coagulase (–)- coagulase (–)- Staphylococcus epidermidis- Staphylococcus epidermidis- Staphylococcus saprophyticus- Staphylococcus saprophyticus
KEYWORDS
3
S. pneumoniaeS. pneumoniae
4
S. pneumoniae • leading cause of pneumonialeading cause of pneumonia
– particularly young and oldparticularly young and old
– member normal flora, nasopharynxmember normal flora, nasopharynx
– replication and spread after damage to upper replication and spread after damage to upper respiratory tract (e.g. after the flu) respiratory tract (e.g. after the flu)
• bacteremiabacteremia• meningitismeningitis• middle ear infections (otitis media) - childrenmiddle ear infections (otitis media) - children
5
S. pneumoniae
• α hemolytic hemolytic• pneumolysin pneumolysin
– degrades red blood cells under aerobic conditions degrades red blood cells under aerobic conditions
• grows well on sheep blood agargrows well on sheep blood agar• no group antigen no group antigen
6
Diagnosis - spinal fluidDiagnosis - spinal fluid
• direct Gram stainingdirect Gram staining• detection of capsular antigendetection of capsular antigen
7
Autolysis – identification after Autolysis – identification after growthgrowth
BileBile
peptidoglycanpeptidoglycan
lipoteichoic acidlipoteichoic acid
teichoic acidteichoic acid-choline-choline
autolysinautolysin
autolysinautolysin
Cell membraneCell membrane
8
C polysaccharide
• Teichoic acid (C polysaccharide)– precipitates in serum– binds C-reactive protein
9
optochin resistant
optochin sensitive
IdentificationIdentification
10
CapsuleCapsule
• prominent prominent – virulent strains virulent strains
• anti-phagocyticanti-phagocytic• carbohydrate antigens carbohydrate antigens
– highly variable among strainshighly variable among strains
– numerous serotypesnumerous serotypes
11
Capsular vaccineCapsular vaccine• ImmunityImmunity
– serotype specificserotype specific
– to eradicate the organism in normal flora to eradicate the organism in normal flora
• VaccineVaccine– a few major serotypes (polyvalent)a few major serotypes (polyvalent)
• Vaccination or the susceptible populationVaccination or the susceptible population– young children young children
– elderlyelderly
• ImmunizationImmunization– major serotypes susceptible to change major serotypes susceptible to change
– population monitoring essentialpopulation monitoring essential
12
Quellung reactionQuellung reaction
• using antisera using antisera
• capsule "fixed" capsule "fixed"
• visible microscopicallyvisible microscopically
13
PathogenesisPathogenesis
• Teichoic acidTeichoic acid– complement activation complement activation – large numbers of inflammatory cells at large numbers of inflammatory cells at
infection siteinfection site
14
TherapyTherapy
• S. pneumoniaeS. pneumoniae – most strains susceptible to penicillin most strains susceptible to penicillin
– resistance is commonresistance is common
15
STAPHYLOCOCCISTAPHYLOCOCCI
• Gram positiveGram positive• Facultative anaerobesFacultative anaerobes• Grape like-clustersGrape like-clusters• Catalase positiveCatalase positive• Major components Major components
of normal flora of normal flora - skinskin
- nares nares
16
Staphylococcus aureusStaphylococcus aureus
17
One of commonest opportunistic One of commonest opportunistic infections, both hospital and community infections, both hospital and community
acquiredacquired:• pneumonia
• osteomyelitis
• septic arthritis
• bacteremia
• endocarditis
• abscesses/boils
• other skin infections
18
Antibiotic therapyAntibiotic therapy• Resistance to penicillinResistance to penicillin
– penicillinasepenicillinase
• Resistance to methicillin Resistance to methicillin
‾ modified penicillin binding proteinmodified penicillin binding protein
‾ methicillin resistant S. aureus (MRSA) methicillin resistant S. aureus (MRSA)
• Vancomycin Vancomycin
• current drug of choicecurrent drug of choice
• resistance observed but uncommon at this time resistance observed but uncommon at this time
19
Hospital infection controlHospital infection control
• MRSA now such a problem MRSA now such a problem – monitoring by PCR of nasal swabsmonitoring by PCR of nasal swabs– eradication eradication
• antibiotics antibiotics
• whole body antisepsiswhole body antisepsis
20
Food poisoningFood poisoning
• not an infectionnot an infection
• food contaminated by humans food contaminated by humans – growth of bacteriagrowth of bacteria
– production of enterotoxinproduction of enterotoxin
• onset and recovery both occur onset and recovery both occur within few hourswithin few hours
21
Food poisoningFood poisoning
• VomitingVomiting
• nauseanausea
• diarrheadiarrhea
• abdominal painabdominal pain
22
Toxic shock syndrome.
23
Toxic shock syndromeToxic shock syndrome
• feverfever
• rashrash
• desquamationdesquamation
• vomitingvomiting
• diarrheadiarrhea
24
Toxic shock syndrome
• Toxic shock toxin Toxic shock toxin
- DisseminationDissemination
• OrganismOrganism
– no dissemination no dissemination
25
S. aureusS. aureus
• babiesbabies– scalded skin syndromescalded skin syndrome
• exfoliatinexfoliatin
26
Lytic exotoxins:Lytic exotoxins:
• α toxintoxin• β toxin (sphingomyelinase C)toxin (sphingomyelinase C)• γ toxintoxin• δ toxinstoxins
– detergent-likedetergent-like
• leucocidinsleucocidins
27
Protein A inhibits phagocytosisProtein A inhibits phagocytosis
Protein AProtein Aimmunoglobulinimmunoglobulin
Fc receptorFc receptor
BACTERIUM BACTERIUM
PHAGOCYTEPHAGOCYTE
28
SpreadSpread
• tissue-degrading enzymestissue-degrading enzymes
– lipase lipase
– hyaluronidasehyaluronidase
29
IdentificationIdentification• Sheep blood agarSheep blood agar– β hemolyticβ hemolytic – yellow pigmentedyellow pigmented (aureus)(aureus)
• mannitol fermentationfermentation• coagulase-positivecoagulase-positive
• phage-typing, rarely performed phage-typing, rarely performed
30
Staphylococcus epidermidisStaphylococcus epidermidis
• major member, skin floramajor member, skin flora
• opportunistic infectionopportunistic infection - less common than - less common than S.aureusS.aureus
• nosomial infections nosomial infections - shunts, cathetersshunts, catheters
• artificial heart valves/joints artificial heart valves/joints
31
IdentificationIdentification• Sheep blood agarSheep blood agar
– non-hemolyticnon-hemolytic– Non-pigmentedNon-pigmented
• Does not ferment mannitolDoes not ferment mannitol• Coagulase negativeCoagulase negative
32
Several other coagulase Several other coagulase negative staphylococcal species negative staphylococcal species
• common on human skincommon on human skin
• some species cause opportunistic infectionsome species cause opportunistic infection
33
Staphylococcus saprophyticusStaphylococcus saprophyticus
• urinary tract infectionsurinary tract infections
• this coagulase-negative species (and others) coagulase-negative species (and others) – not usually differentiated from not usually differentiated from S. epidermidisS. epidermidis
34
GRAM POSITIVE COCCI
S. aureus Beta hemolytic
mannitol yellow
+ -Staphylococcus (Clusters) Streptococcus (pairs & chains)
Catalase
BETA: Bacitracin S. pyogenes (group A)
CAMP/ Hippurate S. agalactiae (group B)
Coagulase
S. epidermidisNon-hemolyticmannitol white
ALPHA: Optochin /Bile Solubility S. pneumoniae
GAMMA OR ALPHA: Bile Esculin 6.5% NaCl Group D Enterococcus
Bile Esculin 6.5% NaCl Group D Non-Enterococcus
Note: S. viridans is ALPHA hemolytic and negative for all the tests below
+
++
++
+
+
-
-
Summary Figure (Identification Scheme)
Hemolysis/TestHemolysis/Test