LAB - Neisseria, Moraxella Flashcards
Opportunistic Neisseria pathogens
N. lactamica, cinerea, etc.
Neisseria sp. characteristics
- gram-neg cocci, in prs w/ flattened adjacent edges (diplococci)
- majority are part of normal human flora except gonorrhoea
- non-motile
- oxidase, catalase pos
- nitrate neg
Gonorrhea
acute pyogenic infection occurring primarily in the urethra, endocervix, anal canal, pharynx, conjunctiva
- men = acute purulent urethritis, prostatitis, proctitis, epididymitis
- women = cervicitis -> pelvic inflammatory disease, endometritis, tuboo-ovarian abscesses ; most remain asymptomatic
Ophthalmia neonatorum
acute eye infection in neonates by N. gonorrhoeae which may be spread to conjunctiva as infant moves through birth canal
Appropriate GC specimens
Gonococci
- endocervical,
- urethral,
- anorectal
- pharyngeal
- blood & fluid samples
- swabs should be made of DACRON or RAYON (cotton and calcium alginate swabs may be inhibitory)
specimen transport for GC
- very fragile! susceptible to: drying, extreme temp changes, pH, toxic fatty acids)
- specimens for gonococci must be taken before initiation of antimicrobial therapy
- commonly used transport systems may be divided into two general groups based on the use of nutritive holding media:
> non-nutritive transport media
> nutritive (growth) transport systems
non-nutritive transport media
- GC
- for protection from O2, toxic fatty acids, and drying
- GC survive well for up to 12 hrs at RT
- Stuart’s, Amies
nutritive (growth) transport system
- commercial systems that provide culture medium (such as Thayer-Martin or NYC agar) that can sustain growth of GC + method for increasing CO2 concentration
- effective for recovering GC from specimens where there are delays in transit
- transgrow, JEMBEC, Gono-pack
direct examination of GC specimens
- PMNs, g-dc from symptomatic male with discharge = correlation rate 95% with culture = presumptive evidence of GC infection
- women = have vaginal flora that look like GC so correlation of direct smear is only 50-70% of cases with culture, so culture is necessary for confirmation
- NOT RECOMMENDED for pharyngeal specimens which saprophytic Neisseria are normal colonizers
primary isolation of GC
- CO2
- CHOC bc nutritionally fastidious
- media with rich source of iron, serum/albumen/starch to neutralize toxic fatty acids
- strain variation = requirement for AAs, purines, pyrimidines, vitamins = added to culture media as Isovitalex
examples of selective-enriched GC media are:
- Thayer-Martin Agar (TM or MTM)
- NYC
- Martin-Lewis (ML)
- GC-Lect (GCL) media
- incubated at 35C in CO2 atmosphere
ID of GC
- look at culture 24, 48, 72 hrs
- smooth, gray, shiny colonies
- oxidase = POS
- gram
- confirmatory tests = carbohydrate degradation in a cystine trypticase agar base containing 1/2% carb, superoxol test, DNAse, antigenic analysis (direct immunofluorescence, co-agglutination, ELISA, DNA probe molecular test)
superoxol test
- spot test
- 30% hydrogen peroxide (contrast to 3% used in catalase test)
- immediate and vigorous bubbling from GC
- other Neisseria sp. = negative or weak, delayed rxn
Gonococci are resistant to high concentrations of this
penicillin
- through the production of beta-lactamase (cleave B-lactam bind of penicillin to form inactive penicilloic acid)
methods to detect B-lactamase production
- chromogenic cephalosporin nitrocefin (Thornsberry method)
- Cefinase disks impregnated with nitrocefin
- when beta-lactam ring of cephalosporin substrate in the disk is hydrolyzed by bacteria, a deep pink colour is produced within ten mins
- pos = B-lactam agents like penicillin will be ineffective against organism
