Micro lab notes Dana alsulaibi
Respiratory system Microbiology laboratory section
Gram Positive Coccus These are the most common microorganisms to appear on a throat swab Staphylococcus Spp. Streptococcus Spp.
clusters) (makes تشبه عناقيد العنب Also, staph are bigger than strep المسبحة تشبه
A- staphylococcus.albus B- staphylococcus.aureus Only staph.aureas gives a golden yellow colour while other staphylococcus species like (staph.albus, staph.epidirmidus, staph.saprophyticus give a white colour Other staph species Blood agar Staph.auereas
CLED media Lactose fermentation ( +ve ) staphylococcus spp.
This is a Differential media Staph.aureus a lactose fermenter so it will change the colour of media. All staph species are lactose fermenters so it isnt possible to differentiate them in this test However,aureas gives a little darker yellow colour than the others
Test for differentiation of Staphylococcus species These 3 tests are used to differentiate staph.aureas from streptococcus: 1) Catalase test 2) Mannitol salt agar test 3) Coagulase test
Catalase test Only staph species are able to hydrolyze H202 to oxygen molecule and water. Apperance of air bubbles indicates the presence if staph species
It is a selective media for staph species to differ between them: Only stap.auereas can hydrolyze mannitol and turn it to yellow. albus and sapriphiticus cant hydrolyze manitol,so no change in colour(pink) MSA expensive Mannitol salt agar media
Colonies are added to plasma and incubwted for 4 hours or overnight. If the plasma is still liquid, this might be staph.albus,saprophyticus or others if clotted.then this us staph aureas(turns fibrinogen to fibrin) c S.aureus S.albus
1. Appearance of zone of inhibition around the antibiotic disk(optochin here) means the bacteria is sensitive >>>>strep.pneumonia 2. No zone of inhibition,it is resistant >>>>strep.viridans
Streptococcus pneumoniae Lancet shaped, each 2 togather كلثوم ام نظارات
Streptococcus viridans When grown on agar, strep is rearranged and gives this apperance
Antibiotic used for differentation btween pyogenes and agalctiae is Bactiracin
Diphtheroids Gram Positive Cocco-bacilli Present on normal flora of healthy infividuals and may cause disease in immuno compromised Arrangement as Chinese letter
Candida Species Larger than bacteria and requires different media. 80% of fungal infections are due to candida species which. It causes thrush around the mouth C.albicans C.Krusei Candida Spp. C.tropicalis C.glabrata
Candida Spp Larger than Bacteria Budding
sabouraud dextrose agar Enriched media. Fungi grown at 25 in a dark place Smells like bread and yeast
To Differentiate between C.albican and other Species Albicans is the most spread and dangerous species. In this test, we can see that candida albicans is the only one that has pseudohyphea Germ tube [ Serum + candida ] All candida species show budding
2. Chrom agar C.glabrata : violet (dark pink) glistering C.albicans : Green
Chrom agar C.Krusei : rough dry pale pink C.Tropicalis Blue
Aspergillus Niger sabouraud dextrose agar Most incidences of respiratory infections are because of aspergillus nagar
Penicillium Spp. As asperigillus and pencillum take 1 to 2 weeks or even a month to grow on culture. The modern world now uses PCR for fast results within 25 hours or less for both bacteria and fungi المكنسة تشبه
Lowenstein Jensen Medium Contain malachite green and egg albumin Media color : green Cell show : Almost no longer usedbecause of long incubation time. PCR used instead Rough Tough Buff Media colour changes from green to brown
Incubation Period = 4 weeks Put the media in covered tubes to avoid drying of media
ziehl neelsen Acid fast stain Mycobacterium Tuberculosis cell wall are waxed for that reason do heating while staining. Stain made of : Evaporation of bacteria while heating is carcinogenic and masks should be worn when handling it Carbol fuchsin Hydrochloric acid alcohol ( 3% HCL ) Methylen blue
When heated the bacterium takes the pink stain(carbolfuchsin).it is left to cool so the wax forms and the stain is kept on bacteria. Then acid alcohol is added to decolorize everything except TB bacteria and a counterstain is added to stain the surrounding tissue blue
T.B Acid fast stain Structures in pink are the mycobacterium tuberculosis