Microbiology (Notes From Uworld)

Microbiology (Notes from Uworld) -

Host cell receptor vs virion/virion protein: CD4 and HIV gp120; CD21 and EBV gp350; erythrocye P antigen and parvo B19

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Thayer-Martin selective media – chocolate agar contains vancomycin to inhibit G (+)ve organism, colistin (polymyxin) and trimethoprim to inhibit G(-)ve organisms other than Neisseria, and nystatin to inhibit growth of fungi

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Changes in host range are most commonly caused by a mutation in the viral encoded surface glycoprotein that mediates virion attachment to target host cell plasmalemma receptors

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***Protein M is the major virulence factor fro S. pyogenes. It inhibits phagocytosis and complement activation, mediates bacterial adherence, and is the target of typespecific humoral immunity to S. pyogenes

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G(-)ve sepsis is caused by the release of LPS from bacterial cells during division or by bacteriolysis. Lipid A is the toxic component of LPS

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***Genetic reassortment

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Etiology of viral croup ranked by commonality o Parainfluenza virus o RSV o Influenza virus o Adenovirus

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Etiology of viral URTI o Rhinovirus 30-40% o Influenza virus 25-30% o Coronavirus 10-15% o Adenovirus 5-10% o Parainfluenza virus 5% o RSV 5%

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Spleen – serve as site of antibody synthesis and as a reservoir of phagocytic cells capable removing circulating pathogen

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***Cirulent mycobacteria will grow as ‘serpentine’ cords on enriched media dut to the presence of cord factor. Cord factor establishes virulence through neutrophil inhibition, mitochondrial destruction and induced release of TNF

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***N. meningitidis gain access to the CNS by first colonizing the nasopharynx and subsequently invading the mucosal epithelium and gaining access to the bloodstream. Through bold, it spreads to the choroid plexus and gain access to the CNS through BBB

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Congenital toxoplasmosis classic triad – hydrocephalus, intracranial calcification and chorioretinitis

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***Meningococcal lipooligosaccharide is responsible for many of the toxic effects observed in meningitis and meningococcemia

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***S. pneumonia is able to undergo transformation which is the uptake and expression of chromosome fragment from the environment made available when another bacterial cell dies and undergoes lysis

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Candida albican is a normal inhabitat of the GI tract (including the oral cavity) in up to 40% of the population. It is a common contaminant of sputum culture. The presence of Candida in sputum does not indicate disease

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Blastomyces dermatitides can cause pulmonary disease in immunocompetant host

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C. neoforman capsule appears red on mucicarmine stain and as clear unstained zone with India ink

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Pts with CGD are at increased risk for o S. aureus o Pseudomonas cepacia (Burkholderia cepacia) o Serratia marcescens o Nocardis species o

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Aspergillus species