HARR-MISC AND FASTI GRAM NEG RODS

Flashcards covering miscellaneous and fastidious gram-negative rods, including identification methods and key characteristics.

TCBS agar

Selective medium for recovery and identification of V. cholerae, differentiating based on sucrose fermentation (yellow colonies).

Vibrio parahaemolyticus

V. parahaemolyticus appears as green colonies on TCBS agar; V. cholerae appears as yellow colonies on TCBS. V. cholerae is the only Vibrio species that causes a positive string test result.

Atmospheric condition for Campylobacter spp.

Microaerophilic atmosphere (reduced O2) is needed to recover Campylobacter spp.

Campylobacter jejuni

Growth at 42°C, hippurate hydrolysis, and susceptibility to nalidixic acid can identify this bacterium.

Helicobacter pylori vs C. jejuni

Urease, nitrate, and hippurate hydrolysis test best differentiates Helicobacter pylori from C. jejuni.

Aeromonas spp. Differentiation

Aeromonas spp. are differentiated from Enterobacteriaceae by being oxidase positive.

Plesiomonas shigelloides vs. Shigella

P. shigelloides vs. Shigella spp. can be quickly differentiated using the oxidase test.

Aeromonas hydrophilia Identification

A. hydrophilia vs. P. shigelloides is differentiated by DNase and Voges-Proskauer test results.

Aggregatibacter spp.

Aggregatibacter spp. are associated with animals; may cause endocarditis, bacteremia, wound and dental infections in humans.

Cardiobacterium hominis vs. Aggregatibacter

Cardiobacterium hominis is differentiated from Aggregatibacter spp. by indole test.

Eikenella corrodens

Eikenella corrodens causes pits in the agar, where colonies are located. The smell of bleach may be apparent when the plates are uncovered for examination.

Kingella kingae

Narrow zone of β-hemolysis on sheep blood agar is characterstic of Kingella kingae.

Capnocytophaga spp.

Capnocytophaga spp. is associated with infections resulting from dog or cat bites and scratches.

Pasteurella spp.

Pasteurella multocida is part of the normal flora of cats and dogs and is frequently recovered from wounds inflicted by them. It produces large amounts of indole and therefore an odor resembling that of colonies of E. coli.

Bordetella pertussis

B. pertussis appears as small, round colonies resembling droplets of mercury on Bordet-Gengou media with sheep blood agar.

Brucella spp. Recovery

Castenada bottles with Brucella broth are the medium of choice for recovery of Brucella spp.

Brucella species differentiation

Basic fuchsin and thionin can differentiate between B. melitensis and Brucella abortus.

Francisella tularensis

Cysteine and cystine are required for growth of Francisella tularensis.

Legionella pneumophila

Buffered charcoal–yeast extract (CYE) agar is best for recovery of Legionella pneumophila from clinical specimens.

Haemophilus species identification

H. aegyptius vs H. influenzae (biotype II) is differentiated by indole and xylose tests.

Haemophilus V factor

Haemophilus species that require the V factor (NAD) are easily recovered on chocolate agar.

Satellite Growth

NAD and hemin allow for satellite growth of Haemophilus spp. around Staphylococcus colonies on sheep blood agar.

H. haemolyticus and H. parahaemolyticus identification

Horse blood agar is used to identify H. haemolyticus and H. parahaemolyticus.

H. influenzae infections

H. influenzae infections are usually caused by capsular serotype b (Hib).

Aggregatibacter (Haemophilus) aphrophilus

Aggregatibacter (Haemophilus) aphrophilus is generally associated with subacute bacterial endocarditis.

Haemophilus ducreyi

Haemophilus ducreyi is difficult to isolate and recover from genital ulcers and swollen lymph nodes.

Ampicillin resistant H. influenzae

Production of β-lactamase enzymes is characteristic of strains of H. influenzae that are resistant to ampicillin.

Haemophilus influenzae Meningitis

Haemophilus influenzae is the main cause of meningitis in young, unvaccinated children.

ALA test

X factor requirement for growth is inaccurate when identifying Haemophilus spp.

Bartonella spp.

Bartonella spp. are biochemically inert—that is, they are negative for oxidase, catalase, indole, and urease tests.

Bordetella pertussis Identification

Direct identification by DFA using polyclonal antibody is the quickest method for B. pertussis compared with PCR.

Francisella tularensis Identification

Francisella tularensis requires cysteine and cystine to grow.

Elizabethkingia meningosepticum

Elizabethkingia (formerly Chryseobacterium) meningosepticum can cause septicemia and meningitis in neonates and immunocompromised adults.

Capnocytophaga canimorsus

Capnocytophaga canimorsus are part of the oral flora of dogs and require at least 5% CO2 for growth.

AACEK organisms

AACEK group is known for causing subacute bacterial endocarditis.

Legionella spp. containment

Specimens suspected of containing Legionella spp. should be handled in a Class II biological safety cabinet.

H. pylori identification

Urea broth test and polymerase chain reaction can presumptively identify H. pylori.

AACEK Definition

AACEK is an acronym for slow-growing gram-negative bacilli causing subacute bacterial endocarditis.

Haemophilus ducreyi

Haemophilus ducreyi is a presumptive identification, taking up to 7 days to grow in specialized media.

Campylobacter jejuni subspecies

Cephalothin and nalidixic acid antibiotic disks differentiate C. jejuni subsp. doylei from C. jejuni subsp. jejuni.

Bordetella pertussis Identification

ELISA using paired samples is the most reliable serologic identification for B. pertussis.