Gram positive cocci Flashcards
Staph aureus properties
Catalase (+) coagulase (+) Mannitol fermentation (+) Phosphatase (+) Heat stable nuclease (+) Gram (+) Cocci facultative anaerobes Of test (++)
Toxins of staph aureus -
Protein A. complement inhibitor protein Staphylokinase Capsule Bound coagulase (clumping factor) Hemolysin Panton Valentine Leucocidin Enterotoxin Exfoliative or epidermolytic toxin
Culture of staph aureus
Blood agar Hot cold phenomenon (toxin induced @ 37°c but clear on cooling @2to 8°c) Selective media Ludlam media Milk salt agar Nutrient agar With glycerol monoacetate(pigment (+) d/t Beta carotene /golden yellow) Slope(oil paint colony)
Staph aureus resistance
Penicillinase
PBP Altered(MRSA)
Vancomycin
Strains of staph aureus
Phage 2 ET A (Chro, heat stable) ET B(plasmid,heat labile)
Phage 1 enterotoxin F(TSS 1)
Protein A (Cowan 1 strain)
Enzymes of staph aureus
Hyaluronidase coagulase Thermonuclease Lipase Serine protease. Function:bacterial survival and spread
Methods of strain identification
Staph aureus
Pulse field gel electrophoresis(genotyping- best method) Phage typing(epi strain 80/81)
Genes of staph aureus
Penicillinase- Blaz gene
MRSA-mec a gene
VRSA-dose dependant
Phage typing staph
80/81
Nutrient agar with susceptible strain
Phage added
Lysis of bacteria
Culture for resistant strain staph
MRSA
Mannitol salt agar with cefoxitin disk(yellow)
HA Vs CA
D test- lawn culture of MRSA strain in erythromycin (inducer) and clindamycin
VRSA
mic testing
Hosp acquired and Comm acquired staph
HA
Resistant
Less virulent
D Test positive
CA
Less resistant
More virulent
D test negative
MSCRAMM
Microscopic surface component recognising adhesive matrix molecules Function: adhesion Gene:agr(accessory gene regulator) Eg:clumping factor Lectins
SCC
Staph cassette chromosome Gene encoding for virulence Ass with insertion sequence HA. 1,2,3 CA 4,5,6 10,11 zoonotic staph(intermedia,hypoxia)
Regulation of virulent gene expression staph
AGR
Sar
Pathogenesis of staph aureus
Adhesion
Colonisation
Invasion & evasion
Infection(local,metastatic)
Panton Valentine leucocidin
Synergohymenotrophic property
F &S
Cytolysis (PMN,macrophage,monocytes)
Invasive pathoogenesis
VRSA mic testing
VRSA >16micro gm/ml
VISA 4-8 micro gm/ml
VAN Sensitive <2microgram/ml
Adhesion
MSCRAMM
Invasion
Enzymes
Toxins(PVL)
Cell wall components(NAG,alpha toxin)-inflammatory response
Evasion
Microcapsule
Protein A
Chips
Function: antiphagocytic
Micrococcus
Gram (+) Catalase positive Mannitol of test (-) Tetrad aerobic
Streptococcus classification
Alpha (viridans)
Beta(lancefield group A to V except I&J)
Gamma(enterococcus)
Grouping of streptococci
Lancefield
A to J
Based on carbohydrates C
Griffith typing
Subgrouping of A
Based on m protein
Emm typing
Based on m gene
(genotype)
Streptococcus proteins
Structural proteins
Capsule(polysaccharide with hyaluronic acid)
Lipoteichoic acid
M protein
Toxins & enzymes Hyaluronidase (antigenic) Streptodornase (antigenic) Streptokinase Erythrogenic toxin(super antigen) Streptolysin O(antigenic) Streptolysin S Serine protease(inhibit IL - 8)
Diseases of streptococci
Scarlet fever Pharyngitis Pasties lines Sandpaper rash Strawberry tongue
PSGN RHD Cellulitis(Peu de orange) Erysipelas Necrotising fasciitis Guttate psoriasis Impetigo contagiosa
Impetigo contagiosa
Honeycomb rash
Necrotising fasciitis
Flesh eating bacteria
M1 M3
PSGN
M1-4 M12
M47 M49 M57 M59 M53-55 M61
scarlet fever
M28
RHD
M5 M6 M1 M19
Culture of streptococcus
Pike(transfer media) (sodium azide,crystal violet ,blood agar)
Crystal violet, neomycin,blood agar
Polymyxin/colistin,fusidic acid, blood agar
Investigation of streptococcus
Aso titre >200(RHD)
Antistreptodornase (PSGN)
Strawberry tongue
Kawasaki disease VIT B12 deficiency Scarlet fever Food and drug allergy TSS
Strep c
Upper respiratory tract infection
S.equisimilis
Diff from gpA strep:ferment ribose not trehalose
Use:streptokinase for thrombolytic therapy
Gp B
Strep agalactiae
Source female genital tract
Cause early(<1week),late(2-12 weeks)
Virulence polysaccharide capsule(10 types)
Screening @35-37weeks by swab culture of vagina and anorectum
Strep F
Alpha haemolytic
Minute strep
Use:heterophile antigen for atypical pneumonia (primary)
capnophilic
Group D
S bovis
Species gallilyticus infantarius
Subspecies gallilyticus,pasteurian,infantarius,coli
Ass:colon Ca ,polyp,bowel lesions
Alpha haemolytic
Viridans streptococcus Salivarius Sanguis Mutants Mites Normal flora of mouth Induce: endocarditis (transient) by eating,toothbrushing,flossing,minor trauma,adherence to biological surfaces
Strep pneumonia
Enterococcus
Commensal flora of normal bowel(<1%) Faecalis(M/C) Faecium(Most resistant) Growth in 40%bile,9.6pH,6.5%NaCl Temp 46 to 60 deg el &10deg cel Test PYR positive Spectacle eye appearance
Virulence factors of enterococcus
Proteins Secreted Hemolysin Gelatinise Serine protease Cocolysin (inhibit endothelium) Lipoteichoic acid(increase Tnf alpha) Pheromones(conjugation without fimbriae)
Surface(structural)
Adhesin of both org recognise MSCRAMM
(To host collagen fibronectin fibrinogen)
Stress protein of E.feacalis(Gls 24) resistance to bile salts
Diseases of enterococcus
UTI Bacteremia Endocarditis Meningitis Intraabd pelvic and soft tissue infections
Resistance of enterococcus
Van A(transposon) Vancomycin and teicoplanin Van B (transposon) vancomycin Van C(chromosome) vancomycin and teicoplanin
Mechanism of resistance to penicillins
Enterococcus
PBP5
Mutation in gene encoding it
Hyper production of it
Vancomycin resistance mechanism
Enterococcus
Replacement of the last peptidoglycan residue from D ALA to D LACTATE(high resistance) or D SERINE( low resistance)
Production of enzymes to destroy D ALA so that binding sites for vancomycin is not available
High level aminoglycoside resistance
Enterococcus
Gentamycin >500 micro gram/L Streptomycin >2000micro gram/L Linezolid. Mutation in 23rRNA genes rRNA methylase Daptomycin Change in membrane homeostasis
Investigations of enterococcus
PYR TEST positive
Bile esculin hydrolysis test black colour
Culture of enterococcus
Blood agar gamma hemolysin, pin point colonies
Telluride agar black colonies
Motile cocci
E gallinarum
E casseliflavus
Van C Resistance
Virulence factors of pneumococci
Structural
Polysaccharide capsule(98 serotypes)
Can diffuse into tissue
Special soluble substance
Toxins
Techoeic acid
Peptidoglycan
Stimulates inflammatory response
IL6 IL1 TNF alpha
Pneumococcal H inhibitor
Inhibition complement system
Choline binding protein(CBPA)
Pneumococcal surface protein(pspc)
Neuraminidase(Nan A)
Pneumococcal surface adhesion(psa A)
Autolysin
Release the toxins
Pneumococcus
Gram positive Alpha haemolytic Lanceolate/flame shaped Capnophilic Bile soluble Optochin sensitive
Confirmatory test for pneumococcus
Bile solubility test
Diseases caused by pneumococci
VAP
Exception >5-6 days and mdr pseudomonas
meningitis in adults fulminant
Otitis media* <5 yrs
Tests for pneumococci (includes culture)
Inulin fermentation positive
Culture Blood agar Initially heaped up followed by alpha hemolysis Draughtsman colony Carrom coin colony
Optochinnsensitive
Zone of inhibition of alpha hemolysis
Bile solubility test
Lysed by bile
Capnophilic bacteria
Gram positive cocci
Strep f
Beta haemolytic
Step pneumoniae
Alpha haemolytic
Vaccines
PPV
23 serotypes
High risk for vaccine to be avoided Chronic lung kidney heart liver d/s Immunocompromised ,DM Cochlear implantation * Splenectomy
PCV
Polyvalent conjugate vaccine
Serotypes 13 7 10/?13 serotypes
High risk
Ages<2m to 2 years
Premature infants
PPSV/PPV
PCV
Polyvalent polysaccharide vaccine
Polyvalent conjugate vaccine
Pneumococcal resistance
Alteration of PBP
Pneumococcal treatment
Ceftriaxone
Vancomycin
Above drugs initially given
Followed by penicillins