Misc
D Test: The D Test is a classic microbiology test and one everyone should be familiar with. The purpose of the test is to determine if the drug erythromycin has altered Staph aureus so it is now resistant to the drug clindamycin. See the picture below for how the discs look on an agar plate. 
Erythromycin and clindamycin are antimicrobial drugs that are structured differently at the molecular level but both act on the 50S ribosomal subunits of bacteria. In some cases, erythromycin can cause the ribosomal target site to become altered making clindamycin ineffective as well. Why is this important? When reporting results to doctors, it is important to report the correct resistance or susceptibility so the patient can get the correct treatment. A positive D Test will mean the laboratory scientist will report resistance to erythromycin as well as clindamycin.
Non fermentative G- bacilli (NFB):
P. aeruginosa, Acinetobacter, stenotrophomonas
P. aeruginosa, grape smell, growth at 42C, lung infection – cystic fibrosis, burn wounds
Pseudomonas (Burkholderia) pseudomallei – melioidosis
Nerdy Note:
P. pseudomallei can survive inside of macrophages. That takes camouflage to the next level!
Specimen Collection and Transport:
Blood cultures specimen collection, 80-95% alcohol then 2% iodine for 1 minute
CSF, if it cannot be plated right away, store at 35-37C or at room temp for no longer than 30 mins.
Curved G- bacilli:
Hektoen, Mac, Campy, and CNA agars for recovery of fecal pathogens
Vibrio – yellow colonies on TCBS media, string test positive
V. parahemolyticus – associated with explosive diarrhea, can be acquired through eating raw shellfish. Be careful with those aphrodisiacs!
Campylobacter jejuni – S-shaped rod, hippurate +, 42C
Campylobacter – microaerophilic – 5% O2, 10% CO2, 85% N2
Helicobacter – urease +, associated with ulcers
Plesiomonas – oxidase +
Simmons citrate – blue
Lysine Iron agar and Kilger Iron agar in relation to TSI sugar tests
Bordetella urease:
B. bronchiseptica – rapid urease
B. parapertussis – pos at 18 hours
B. pertussis = negative
Acinetobacter – oxidase negative
Pasteurella – cat scratch, indole +
Bordetella – Bordet-Gengou agar, whooping cough
Francisella tularensis – needs Cysteine for growth
Legionella pneumophila - Buffered charcoal yeast extract, motile, doesn’t gram stain well, infections acquired from environment, found in respiratory sample
B. anthracis susceptible to penicillin while other Bacillus spp are not
Gardnerella vaginalis – squamous epithelial cells with Gram variable stain, 10%KOH test = whiff test
Nocardia – partially acid fast, growth above 37C
Borrelia burgdorferi – lyme disease, deer tick of Ixodes genus
Mycoplasma pneumonia – atypical pneumonia
Mycoplasma hominis – fried egg appearance
Corynebacterium – Chinese letters appearance
C. jeikeium – immunocompromised, antibiotic resistance
Aeromonas hydrophilia
Listeria monocytogenes – motile, G+, small translucent beta hemolytic colonies on SBA
Shewanella putrefaciens – commonly misidentified as an enteric pathogen to the large amount of H2S it produces
Brucella spp – class 3 pathogen, usually labs send isolates to reference labs, found in blood culture
Zinc test – nitrates:
Some organisms will reduce nitrate to nitrite which will give the red color from alpha-naphthylamine. Some organisms will reduce nitrate to nitrogenous compounds other than nitrite. To confirm a true negative nitrate reduction, the zinc test can be used. For samples with no red color, if nitrates are present, zinc will reduce residual nitrates to nitrite causing the red color change. If nitrates are not present, no color change can occur and the organism does have the ability to reduce nitrate, just no to nitrite.
Vogues Proskauer Test:
The VP test detects glucose fermentation via the glucose end product acetoin.
Oxidation-fermentation (OF) tubes:
Used to distinguish Micrococcus from Staphylococcus usually by glucose fermentation