Previous year question answers, Study notes of Microbiology

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STREP TO^ COLLI

Gram the cocci

arranged in (^) chains or pairs · (^) most imp # which cause & with^ a^ characteristic strep . pyogenes pyogenic^

infection

tendency to spread Responsible For - non suphirrative

lesions which occur in

acute rheumatic fever^

Y sequare^

to

infection

glomerulonephritis CLASSIFICATION ① Based^ on (^) oxygen requirement-facultative ancrobes obligate ancrobes ② (^) Based (^) on (^) hemolysis on blood agar -> Alpha (^) (2)-hemolytic

• produce (^) greenish discolouration with partial hemolysis^ (1-^ mm (^) wide) eg
• (^) Vividans

Pneumocaus

Betar (^) (B) - hemolytic

• sharply defined^ clear^ , colourless^ zone of complete^ hemolysis^ (2-4 mm^ wide) Non (^) hemolytic ~ do (^) not produce hemolysis include-fecal (^) streptococci-enterococcus ③ Based^ on^ carbohydrate (^) antigen (C)^ on^ the^ cell^ wall

serologically grouped^

hemolytic -^ Lancefield's^ T

A-

[with 1953

Streptococci (^) groups k- y STREPTOCOLCUS (^) PYOGENS

Morphology · gram tre (^) coci arranged

in

pair or chains · oval or spherical in shape

· non motile

, non sporing · capsulated

Pathogenicity

streptococcal infections can^ be-localised

invasive (^) (diffuse

may

manifest (^) a (^) sequele

It can (^) be due to^ - > hupersensitivity to (^) streptococcal component

element of autoimmunity may be^ involved

antigenic cross^ run^

have been demonstrated blu

Streptococci 2 Heart^ tissue

2. Post^ streptococcal glomerulonephritis · nephritis is^ caused^ by only few^ types of^ nephritogenic (^) types

It's

pathogenesis may^ be (^) due to antigenic cross-reaction (^) blu glomerular membrane of (^) antigen and cell (^) membrane of nephrotic streptococci

* LAB^ DIAGNOSIS

Specimen

• (^) Swabs or (^) Aspirate from^ affected^ site Scrum is collected for^ serology inrheumatic fewer^ & (^) glomerulonephriti

2. (^) Transport

pike's transport medium^

is used

Microscopy

• (^) Gram stained films from

pus which^

show gram the cocci (^) indicate streptococcal inf

however smear are

of

no value in^ int of throat or

genetalia as strepto (^) may form^ part

of resident flora

4. culture^ -^3 %^ sheep blood^ agar incubated at 37 % ancobically or^ under^ 3-10 %^ (O

colonies on blood

agar after

24 has show-small

circulat semitransparent colonic with clear^ hemolysis around them

virulent strains -^ Matt^ colonies

Avirulent

• glossy colonies

* can be stored in Robertson's cooked meat media

selective media^

• i) (^) crystal violet^ +^ natidixic^ acid^ +^ colistin^ sulphate added^ to do blood

agar

inhibit

gram-re?^ ii)^ PNF (^) medium - polymyxin Staphylococcus nalidixic (^) acid

Fusidic acid

5. Biochemical^ reactions strepto-catalase +ve Y (^) imptodiffe staph

• (^) catalase-ve strepto not^ soluble^ in^10 %^ bile (^) unlike (^) S. pneumonial

· ferments

sugar producing acid but^ no (^) gas

PYR test 2 failure to ferment ribose

helps

to diff blu other^

streptococci

* Treatment

· drug of (^) choice -> penicillin those who (^) are (^) allergic - crythromycin or cephalexin Antimicrobial drugs have (^) no action (^) on (^) glomerulonephritis &

rheumatic ferch

Prophylaxis · long term^ administration^

of

penicillin in (^) children who have shown early symptoms

of rheumatic fever

· This prevents streptococal^ reinfectiona further damage to heart. Antibiotics prophylaxis- (^) glomerulonephritis -^ as this^ complication not useful for^ follows a (^) single infno re infection occurs