Typical oral/respiratory tract pathogens and commensals.
The upper respiratory tract host a large number of commensals and pathogenic bacterias forming a complex microbial community.
1) STAPHYLOCOCCUS AUREUS (S.pyogenes)
a) Shows purple/blue coloration on gram staining (Gram +ve).
b) Typically occurs in grape-like clusters.
c) During laboratory diagnosis shows positive coagulase test. Coagulase test is done by two methods-tube and slide coagulase test. The tube coagulas test detects free coagulase and the slide coagulase test detects bound coagulase.
d) Useful screening procedure for differentiating s.aureus from s.epidermidis in mixed cultures is phosphatase reaction. S.aureus colonies assumes a bright pink colour.
e) On nutrient agar slope,the confluent growth presents a characteristic oil-paint appearance.
2) STREPTOCOCCUS PNEUMONIA (Pnemococcus,Diplococcus pnemoniae)
a) Slightly elongated cocci,and occurs in pairs.
b) With one broad end and other pointed end,they have a flame shaped or lanceolate appearance.
c) Grow only in enriched media.
d) Grows best in 5% carbon dioxide.
e) On blood agar,they are alpha haemolytic and on long incubation colonies show draughtsman or carom coin appearance. Under anaerobic conditions produce beta haemolysis.
f) Bile solubility is of diagnostic importance.
g) The sensitivity of pnemococci to optochin is useful in differentiation of them from streptococci.
h) Pnemococci possess a specific polysaccharide capsule that is responsibleof "Quellung "reaction.
i) Readily undergo autolysis in culture due to presence of autolytic amidase.
3) STREPTOCOCCUS PYOGENES
a) Can form chain as divide in one plane
b) Produce a sharply defined clear,colourless zone of hemolysis.
c) Growth occurs only in media containing fermentable carbohydrates.
d) Growth and haemolysis are promoted by 10% carbon dioxide.
e) Hydrolysis of pyrroidonyl napthylglamide (PYR test) and failure to ferment ribose are useful in differentiating S.pyogenes from other streptococci.
f) Sensitivity to bacitracin is employed as a convenient method for differentiating S.pyogenes from other hemolytic streptococci.
g) DICK TEST: pyrogenic/scarlantinal toxin when injected produces erythemous toxin. This test is uesd to identify children susceptible to scarlet fever.
h) Blanching of this erythemous rash on local injection of convalescent serum is used as a diagnostic test for scarlet fever(SCHULTZ CHARLTON reaction).
4) STREPTOCOCCUS VIRIDANS
a) Produce a greenish discoloration with partial hamolysis around colonies. The zone of lysis is small.
b) Grow only in enriched media.
c) Grows best in 5% carbon dioxide.
5) YERSINIA PESTIS
a) Nonmotile,nonsporing microaerophilic,biochemically unreactive,pleomorphic bacilli.
b) Characteristic bipolar(safety pin) appearance,with Wayson's stain/giemsa/methylene blue.
c) Optimum growth occurs at 27 C and pH7.2.
d) Shows STALACTITE growth in ghee broth.
e) Based on fermentation of glycerol and reduction of nitrate,it is divided into 3 groups.
f) Catalase and aesculin positive,urease and oxidase negative.
6) HAEMOPHILUS INFLUENZA
a) Capsulated coccobacilli showing pleomorphism.
b) Stained by LOEFFLER's methylene blue or dilute carbol fuschin.
c) Flides agar is best for primary isolation.
d) On LEVINTHAL's medium-capsulated strain shows distinct iridescence.
e) Require both X factor(heat stable hemin) and V factor (heat labile coenzyme present in RBCs)so heating or boiling in blood agar(chocolate agar) is superior to plain agar.
f) Shows "SATELLITISM"(dependance on V factor) when S.aureus is streaked across blood agar.
g) The V factor is NAD or NADP.
7) BACILLUS ANTHRACIS
a) The first bacillus to be isolated in pure culture and shown to possess spores; the first bacterium used for preparation of attenuated vaccine.
b) The end of bacilli are truncated or often concave and swollen so that a chain of bacilli presents a "bamboo stick" appearance.
c) Sporulation of anthrax bacili is inhibited by calcium chloride.
d) M'Fadyean's reaction due to capsule is employed for presumptive diagnosis of anthrax in animals.
e) "MEDUSA head " appearance and "INVENTED FIR TREE" appearance are cultural characteristics .
f) The "String of pearls reaction" and the susceptibility of anthracis to gamma phage helps to differentiate from B.cereus and other aerobic spore bearers.
g) "DUCKERING" is the destruction of the spores in animal products imported into non-endemic countries,in which formaldehyde is used for disinfection of wools animal hair and bristles.
h) Ascolis thermoprecipitation test is a ring precipitation test used for demonstration of anthrax antigen in tiissue extracts.
i) Cut-glass appearance in transmitted light.
8) KLEBSIELLA PNEUMONIA
a) Non motile capsulated organism
b) Gram negative rod shaped
c) Aerobic or facultative ananerobes,non sporing and non acid fast
d) Grows well on Macconkey medium
e) Urease positive, Oxidase negative
f) Glucose fermenter.
9) BORDETELLA PERTUSIS
a) Gram negative,stictly aerobic coccobacilli which grows ionly in complex media.
b) Pleomorphic,nonmotile,nonsporing,capsulated,fimbriated coccobacilli which shows metachromatic granules on staining with toluidine blue.
c) Grows on enriched media like Regan Towe or Bordet Gengou glycerine blood agar resembling ‘bisected pearls ‘ or ‘mercury drops'.
d) In cultures it forms a ‘aluminium paint' or ‘thumb print' appearance.
e) Charcoal containing media is preferred.
f) Blood is required to neutralize the inhibitory materials formed during bacterial gowth.
10) MYCOBACTERIUM TUBERCULOSIS
a) Acid fastness is due to presence of mycolic acid in the cell wall.
b) The ‘catalase-peroxidase' test help in differentiating tubercle bacilli from atypical mycobacteria and provide an indication of sensitivity of the strain to isoniazid.
c) Mamilian tubercle is stained by ZIEHL- STENSON METHOD or by floroscent dyes.
d) Generation time-14-15 hours.
e) Colonies appear in about 2 weeks.
f) Grows luxurily in culture(eugonic) and addition of 0.5% glycerol and carbon dioxide improves its growth.
g) Solid medium most widely employed is LOWENSTEIN-JENSEN medium without starch.
h) Virulent strain form long serpentine rods in liquid media while avirulent strain grows in dispersed manner.
i) Catalase and peroxidase activities are lost when the bacilli beomes INH resistant.
j) Positve urease test.
k) Diagnosis includes microscopy and concentration methods. The specimen(sputum) is best collected in the morning before any meal. AFB microscopy and fluoroscent microscopy(stained with auramine phenol dye under UV illumination) are the microscopic techniques.
l) PETROFF's method is simple and most widely used concentration method.
m) PCR and ligase chain reaction are use as diagnostic techniques.
n) RFLP and15 fingerprinting are used for epidemological typing of strain.
11. CHLAYMDIA PNEUMONIA
a)Stained with Geimsa or casteneda stains.
b) Immunoflorescence is done using monoclonal antibody.More sensitive and specific method.
c) Cell culture is done by inoculation into embroynated eggs or experimental animals,
d) grows better in HL and HEp-2 cells.
12. Pseudomonas Aeroginosa :
a) Gram negative bacilli.
b) Motile with polar flagella
c) Obligate aerobe
d) oxidizes Indophenol and unable to ferment lactose , differentiates it from from other enteric bacilli
e) Grows well at 37-42C on ordinary media
f) Growth at 42C differentiates it from other pseudomonas species.
g) Selective media is cetrimide agar.
13. Mycoplasma pneumonia
a) Smallest living bacteria
b) Lacks cell wall, pleomorphic in shape.
C )Gram negative organisms. Geimsa stain is better used.
d) Can be grown on cell free media that contains lipoprotein and sterols.
e)Biphasic colony with fried egg appearance best studied after staining with Dienes method.
f) Grows best at 35-37C .Media enriched with 20% horse or human serum and yeast extract.Peniciilin and thalium extract added as selective agents.