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
N. meningitidis can be found in the ______ and ______ of 30% of asymptomatic individuals
nasopharynx and oropharynx
- spread through airborne droplets, enter blood stream = meningitis, meningococcemia with petechiae, pneumonia
- children and young adults
Waterhouse-Friedrichsen sybndrome
- severe form of meningococcemia
- resulting often in organ failure
appropriate specimens for N. meningitidis
- CF = STAT
- blood = at least two should be drawn at separate intervals when patient is experiencing chills or fever
- skin lesions = can be isolated from petechiae
- URT specimens = throat or nasopharynx of asymptomatic carriers who form the reservoir of infection
this is diagnostic for meningitis
- CSF = PMN and g-dc
- BUT meningococci cannot be differentiated from other g-dc from URT smears
- so latex and co-agglutination tests for detecting meningococcal polysaccharide antigens available for CSF, urine, serum specimen as a preliminary test along with direct smear examination
primary isolation and identification of N. meningitidis
- not as nutritionally fastidious as gonococci
> will grow on BAP or CHOC - increased CO2 needed
- oxidase testing
- gram stain
- carbohydrate degradation tests
- automated tests like Vitek-MS, MALDI-TOF
- lactose test will differentiate this from N. lactamica
-serogrouping for capsular polysaccharides may be performed for epidemiology
Neisseria sp. that is normal flora of the nasopharynx, particularly in children
N. lactamica
- can cause respiratory tract infections in RARE cases, as well as bacteremia, and meningitis
- distinguished fqrom meningococci by its growth on simple nutrient agar and by degradation of lactose with production of acid
- lactamica utilizes lactose by producing enzyme beta-galactosidase
Moraxella catarrhalis
- normal flora of URT
- wide variety of infection ranging from infection of middle ear (otitis media), bronchitis, pneumococcal conjunctivitis, and sinusitis
- aerobic, non-motile, g-dc
- ox and catalase pos
- asaccharolytic
- positive DNAse rxn (not like Neisseria)
- positive hydrolysis of tributyrin
- nitrate reduction pos
- beta-lactamase so resistant to penicillin
growth of M. catarrhalis
- readily grows on BAP and CHOC with no additional atmospheric requirements
- only worked up when predominant growth on plate of a respiratory specimen otherwise normal flora
T or F. Neisseria gonorrhoeae infects only humans
T
CTA sugar test
- contains 1% carbohydrate
- phenol red as indicator so is yellow in acid
- rxn = oxidative sugar breakdown
- tubes are incubated overnight with loose cap in O2 as CO2 may give an acidic pH in the media = false colour change
- CTA base has no sugar; ensures organism will grow and that media won’t go acid without sugar
G = growth
+ = yellow - = pink
the key test for M. catarrhalis
tributyrin hydrolysis
- enzyme butyrate esterase is produced which decreases pH and causes a colour change
