Microbiology Facts from Previous Papers

·         INSPISSATION: Egg containing media

LJ Medium, Loeffler’s, Dorsett, Petroff’s Medium

·         TYNDALLISATION:

Sugar or Gelatin Containing media

·         To enhance pigment production of S.aureus: 5% Milk addition, Glycerol acetate + NA

·         Generally GP forms SPORE:

GPB- Bacillus, Clostridium

GPC- Sporosarcina

But GNB- Coxiella Burnetti

·         Exceptions to KOCH’s POSTULATES:

Gonococcus: 3^rd not followed

Lepra Bacilli: 2^nd not followed

·         CONCOMINANT IMMUNITY:

Schistosomes creating barrier against continuous reinfection aks NATURAL ZOOPROPHYLAXIS

·         PARATETIC HOST: host in which parasite merily remains viable without further development.

Aka TRANSPORT or MECHANICAL HOST.

Eg: fly

·         NIH Swab: T.saginata, E.vermicularis

·         AUTOINFECTION occurs in: T.solium, S.stercoralis, E.vermicularis SET

·         Human infection dead end in: T.spiralis, E.granulosus

·         Lecithinase produced by: B.cereus, Clostriddium, Vibrio

·         VMA ELISA is for detection of: Shigella, EIEC

·         Heaviest Egg: unfertilized egg of A.lumbricoides

Largest Egg: fasciolepsis buski

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·         Mycobacteria should be stained for acid-fast organisms, using either Ziehl-Neelsen stain or other like Kinyoun stain.

·         Calcofluor white binds to cellulose and chitin in the cell walls of fungi and fluoresces under long-wave length ultraviolet light. It may demonstrate morphology that is diagnostic of the species (eg, spherules with endospores in Coccidioides immitis infection).

Pneumocystis jiroveci cysts are identified morphologically in silver-stained specimens.

PAS is used to stain tissue sections when fungal infection is suspected.

After primary isolation of fungi, stains such as lactophenol cotton blue are used to distinguish fungal growth and to identify organisms by their morphology.

·         Coenorhabditis elegans (a nematode) was the FIRST MULTICELLULAR ORGANISM FOR WHICH THE ENTIRE GENOME WAS SEQUENCED.  ( First bacteria was H.influenzae.)

·         Robert Koch

Father of Medical Microbiology

Discoveries – Anthrax bacilli, tubercle bacilli, vibrio cholera

The result of Koch investigations into a bubonic plague epidemic in Calcutta in 1897 showed that rats were vectors of the disease. He also demonstrated that sleeping sickness is transmitted by the tsetse fly.

Other studies by Koch included leprosy, surra, rinderpest, Texas fever and malaria. Koch formulated systematic method for biological research (Koch's Postulates) which are still observed to this day.

In 1905 Koch won the Nobel Prize for Physiology or Medicine "For his investigation and

discoveries in relation to tuberculosis".

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• Detection of HIV RNA by nucleic acid amplification of the viral load is the best predictor of “progression to AIDS.” (Virology)

• HIV RNA PCR and sequencing of the amplified products may be used to monitor resistance to anti-HIV drugs. HIV patients with total CD4 lymphocyte counts of less than 200 CD4 cells/μL are susceptible to opportunistic infections such as those caused by Cryptococcus, Mycobacterium, and Pneumocystis. (Virology)

• Cyclospora is an ooidian parasite similar to Cryptosporidium. It causes food-borne diarrheal illness and has been associated with contaminated berries. (Parasitology)

• Giardia, a large flagellate with both cyst and trophozoite forms, is the most common parasitic disease in the United States. The disease is characterized by diarrhea, cramping, and fever. (Parasitology)

• Enterohemorrhagic E. coli causes bloody diarrhea and hemolytic uremic syndrome. The mode of action is production of Shiga-like toxin by E.coli. (Bacteriology)

• Vancomycin-resistant enterococci, methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-indeterminate S. aureus (VISA) are among the most feared nosocomial pathogens. A recently introduced antibiotic, quinapristin-delfapristin, effectively treats vancomycin resistant enterococci or the few vancomycin-indeterminate MRSAs that have occurred. (Bacteriology)

• Following an upsurge of tuberculosis in the early 1990s, cases of Mycobacterium tuberculosis infection have remained static. M. tuberculosis causes initial primary pulmonary infection as well as a chronic disease characterized by hemoptysis, loss of weight, and fever. (Bacteriology)

• Penicillin-resistant pneumococci (Streptococcus pneumoniae) may account for up to 40% of isolates of S. pneumoniae. Third- or fourth-generation cephalosporins may be used as alternative treatment as well as vancomycin and rifampin. (Bacteriology)

·         Ehrlichia, a recently emerging tick-borne pathogen, is transmitted by Ixodes scapularis, the same tick that transmits the Lyme disease bacterium.

Ehrlichia is also transmitted by the Lone Star tick, Amblyomma americanum. (Chlamydia, Rickettsia)

• Eastern equine encephalitis may be transmitted to humans by the bite of a mosquito, particularly in the northeastern United States. (Virology)

• Transfusion-associated babesiosis is a growing problem, particularly in the immunosuppressed or patients without a spleen. Tick-borne babesiosis caused by the same tick that transmits Lyme disease is an emerging infection. (Parasitology)

• Dengue fever, a viral illness transmitted by the Aedes mosquito, is prevalent in epidemic proportions in both the Caribbean and Southeast Asia. (Virology)

• There are five major classes of immunoglobulin: IgG, IgM, IgA, IgD, and IgE. These immunoglobulins are distinguished by differences in the C regions of each individual H chain. These differences are function-related.

• Peptidoglycans are unique to prokaryotic organisms. They consist of a glycan backbone of muramic acid and glucosamine as well as crosslinked peptides. The enzymes responsible for cross-linking (transpeptidases) are the targets for β-lactam antibiotics. (Physiology)

• Genetic exchange in microorganisms occurs by several mechanisms, including transformation, transduction, conjugation, and transposition.

These processes are the basis for gene cloning in microorganisms. (Physiology)

• Virulence factors in bacteria include adherence factors, invasins, capsules, endotoxin, and exotoxin. Such factors enable microorganisms to invade the host, cause disease, and resist host defense mechanisms.(Physiology)

• Sites of action of antimicrobial agents include cell-wall synthesis, cell membrane integrity, DNA replication, protein synthesis, DNA dependent RNA polymerase, and folic acid metabolism. (Physiology)

• Staphylococcus aureus expresses two types of superantigens: enterotoxin (responsible for staphylococcal food poisoning) and toxic shock toxin.

• Free radicals of oxygen (superoxides) kill anaerobic bacteria exposed to air. Superoxide dismutase is a potent bacterial antioxidant. The presence of peroxidases in bacteria is protective. (Physiology)

• Campylobacter and Helicobacter are both helical-shaped bacteria. Helicobacter is known to play a role in the pathogenesis of peptic ulcer disease, while Campylobacter causes a food-borne gastrointestinal illness, most commonly from undercooked meat. Both bacteria are susceptible to antibiotics such as tetracycline. Helicobacter may be treated with Pepto-Bismol, metronidazole, and amoxicillin. (Bacteriology)

• The agents of bovine spongiform encephalopathy (Mad Cow Disease), scrapies, and new-variant Creutzfeldt-Jakob disease in humans are prions or amyloid fibrils. Also included are prions that cause chronic wasting disease (CWD) in elk and deer, although these agents of CWD have not been shown to be transmissable to either cattle or humans. These self replicating proteins are resistant to heat and chemical agents. (Virology)

• Prior to 1999, West Nile virus, an arbovirus with serological crossreactivity to St. Louis encephalitis virus was not seen in the United States. However, during 1999 and 2000, a large number of birds were infected with West Nile virus, as well as a few humans, some of whom died. (Virology)

• The genotype of hepatitis C is important in predicting the response of this virus to therapy with interferon and ribavirin as well as the required length of treatment. (Virology.

·         Vascular invasion is characteristic of: mucormycosis, aspergillus

2) Inhalation of spores of which fungus is commonest: aspergillus

3) Only pathogenic yeast in man: C. neoformans

4) Sclerotic bodies with septate hyphae characteristic of: blastomycosis

5) Asteroid bodies are a characteristic feature of: sporothrix

6) Fungal infection is characterised by its capability to disseminate via lymphatics: sporothrix

7) Sporulation occurs in which phase: phase of decline

8) Prominent feature of paracoccidiomycosis: ulcerative granuloma of buccal and nasal mucosa

9) Characteristic feature of coccidiomycosis: spherule formation

10) Fungal infection which causes arthralgia / valley fever / desert rheumatism:
Coccidiomycosis

11) Thick walled barrelled shaped spores: arthrospores characteristic of coccidiodes immitis

12) Fungus which is urease positive: C. neoformans

13) Copper pennies appearance in tissue: paracoccidiodes

14) Most characteristic clinical feature of all cases of paracoccidiodomycosis: lymph node enlargement