Comp 1 - Microbiology Identification Methods

blood agar

growing non-fastidious bacteria (can grow without special nutritional supplements/conditions)

alpha-hemolysis - Streptococcus pneumoniae

beta-hemolysis (complete hemoylsis) - Streptococcus pyogene and Staphylococcus aureus

chocolate agar

fastidious bacteria

esp. haemophilus influenzae and gonococcus

macconkey agar

gram negative, enteric rods (gut bacteria), lactose-fermenters (E. coli and Klebsiella) vs. non-fermenters

macconKEE agar = Klebsiella, E. coli, Enterobacter

Lowenstein/Jensen agar

mycobacteria (TB bacillus)

Sabourad dextrose agar

fungi

SAB is a fun guy

buffered charcoal yeast extract

Legionella, Francisella tularensis

Bordet Gengou agar

Bordetella pertussis

acid fast stain

Mycobacteria species (like tuberculosis) and Cryptosporidium (protozoan parasite) - appear red/maroon

auramine-rhodamine flurochrome staining

modified acid fast stain

Nocardia bacteria - red/maroon

capsule stain (India ink)

CSF sample

Cryptococcus neoformans; Bacillus anthracis

Giemsa stain

protozoan parasites esp. Plasmodia (malaria) and some bacteria like chlamydia, rickettsia, anaplasma, erchlichia, borrelia

catalase test

Staph. spp. of bacteria - catalase+ (bubbles appear when bacteria put in H2O2)

Strept. family - catalase-

most bacteria except Streptococci (and Enterococcus) are positive

coagulase test

Staph. aureus coagulase+

other Staph. spp., such as S. epidermidis and S. saprophyticus are coagulase-negative

beta-hemolysis

Group A and B Strep; Staph aureus; Clostridia; E. coli.

usually clear zones of hemolysis appear on areas of the blood agar where the organisms are growing

alpha-hemolysis

greenish or greenish-brown zones of hemolysis appear on areas of blood agar where the organisms are growing

alpha-hemolytic streptococci known as the viridans strept. (Ex. strept. pneumonae)

P-disc sensitivity (optichin sensitivity)

Strept. pneumoniae DO NOT GROW in presence of P-disc (optochin is selective inhibitor)

other alpha-hemolytic Strept. are resistant to P-disc

A-disc sensitivity

(+) Group A Streptococci (S. pyogenes) DO NOT grow in presence of A-disc (bacitracin antibiotic)

(-) other beta-hemolytic Strept. resistant

lactose fermentation

E. coli and Klebsiella are lactose-fermenters (agar turns red or purple)

most other gram-negative rods like Salmonella and Shigella are not

sorbitol fermentation

non-EHEC strains of E. coli (positive)

E. coli 0157, also known as enterohemorrhagic E. coli (EHEC) or Shiga-toxin producing E. coli (STEC) CANNOT ferment sorbitol (negative)

oxidase activity

Pseudomonas, Campylobacter, Helicobacter, the Vibrios, Neisseria and Pasteurella (mixture w/ substrate turns purple)

superoxide dismutase

organisms use this to combat ROS

seen in facultative anaerobes and obligate aerobes