Week 4 Flashcards
GENERAL CHARACTERISTICS OF NEISSERIA
- Gram-negative cocci usually in pairs with adjacent sides flattened, giving them coffee or kidney bean shape
- Non-motile, do not form spores
- Aerobic but can grow anaerobically in presence of nitrites (alternative electron acceptor)
- Oxidase positive, catalase positive
NATURAL HABITAT Neisseria
Most Neisseria spp.
* Non-pathogenic inhabitants of oro- and naso-pharyngeal mucous membranes of humans
* On rare occasions non-pathogenic species may be considered opportunistic
Neisseria gonorrhoeae
* Generally always considered pathogenic
* May infect exposed anogenital and oropharyngeal mucous membranes
Neisseria meningitidis
* may colonise oro- and nasopharynx as non-pathogen (in “carrier” state for many months)
* may colonise exposed anogenital mucosal membranes
* some strains may cause epidemic and acute meningitis
Moraxella catarrhalis (formerly called Neisseria catarrhalis)
* rarely isolated from oropharynx of healthy adults
* may be carried more frequently in children and the elderly
VIRULENCE FACTORS - NEISSERIA
GONORRHOEAE
- pili− mediate attachment of organisms to mucosal surfaces−inhibit ingestion and destruction by neutrophils
- outer membrane lipooligosaccharide (LOS) and opacity (Opa) proteins − promote adherence and resistance to bactericidal effect of human serum
- outer membrane proteins (OMPs) and peptidoglycan
−elicit immune response − have intrinsic toxicity for human fallopian tube mucosa - IgA1 protease −cleaves heavy chain of IgA1 neutralising its antiinfective effect and reducing mucosal resistance to
infection - ability to grow anaerobically in presence of nitrite −allows organism to proliferate in endocervix, rectum,
genital tract, pelvis
VIRULENCE FACTORS - NEISSERIA
MENINGITIDIS
- capsular polysaccharides −13 capsular polysaccharide serogroups:
A, B, C, D, H, I, K, L, X, Y, Z, W, 29E
−inhibit phagocytosis - LOS endotoxin
−causes vascular necrosis −induces inflammatory response - pili
- OMPs
- IgA1 protease
- utilisation of transferrin-bound iron as a sole iron source− Colonisation of mucosal surfaces requires iron
- formation of antigen-antibody complexes − May relate to late manifestations of infection such as arthritis
VIRULENCE FACTORS - MORAXELLA
CATARRHALIS
- pili
- LOS
- OMPs
- haemagglutinins −contribute to adherence
CLINICAL SIGNIFICANCE - NEISSERIA
GONORRHOEAE
- causative agent of gonorrhoea
- most areas of world affected
- estimated that only ½ of cases are reported
- since 1980 slow decline in incidence
- incidence highest in high-density urban areas among persons under 24 years of age who have multiple sex partners and unprotected sexual intercourse
- transmitted by direct, close, usually sexual contact
- transmission to neonates usually occurs during birth
UNCOMPLICATED GONORRHOEA Neisseria in men
Disease in Men
* incubation period 1 to 10 days with average being about 5 days* acute urethritis with symptoms including clear to copious
purulent discharge, urinary burning and frequency
* systemic signs generally lacking
* asymptomatic infections in 1% to 5% of infected men* if untreated, men may develop epididymitis, prostatitis, urethral stricture, sterility
UNCOMPLICATED GONORRHOEA Neisseria in women
Disease in Women
* primary site of infection endocervix with symptoms including vaginal discharge, dysuria, erythematous friable cervical
opening, abdominal pain
* in prepubertal girls, gonococcal infection may present as
vulvovaginitis
* asymptomatic infections in 20% to 80% of infected women
* ascending infection may result in salpingitis, tubo-ovarian
abscesses, pelvic peritonitis, ectopic pregnancies, sterility
OTHER INFECTIONS Neisseria gonorrhoea
Oropharingeal and anorectal infections
* in persons practising receptive oral and anal intercourse
Conjunctivitis - Ophtalmia neonatorum
* symptoms include tearing, oedema, purulent exudate* primarily seen in neonates
* may also be seen in adults who become inoculated with infected genital secretions
* laboratory personnel (accidentally infected)
* if not treated, scarring or perforation of cornea may occur
Disseminated gonococcal infection (DGI)
* occurs in 1% to 3% of persons with gonorrhoea* symptoms include fever, chills, skin lesions, diffuse
arthralgias
* few patients may develop endocarditis or meningitis* must be differentiated from meningococcaemia
CLINICAL SIGNIFICANCE - NEISSERIA
MENINGITIDIS
- causative agent of meningococcaemia and / or meningitis* meningococcal disease world-wide in distribution
- varies from sporadic cases to epidemics
- adult nasopharyngeal carrier important in transmission, provides reservoir of infection
- transmission by direct contact with contaminated respiratory secretions or airborne droplets
- crowded living conditions facilitate spread
- sexual transmission may cause lower genital tract infections
MENINGITIS
* Neisseria meningitidis causes 20% of meningitis* groups A and C cause epidemic disease in
undeveloped countries
* group B causes endemic, sporadic disease in
developed countries
* New Zealand was in the grip of a meningococcal B
epidemic for more than decade
* incubation period 2 to 10 days
* symptoms include sudden onset with fever, intense
headache, nausea, vomiting, painful stiffness of neck, retraction of head, spinal rigidity, petechial rash
* highest incidence: between 3 months and 5 years of
age, and among young adults
* if not treated, may cause deafness, optic neuritis,
polyarthritis, hydrocephalus, death
* microscopic and biochemical changes in CSF
MENINGOCOCCAEMIA
* acute or chronic bloodstream infection without meningitis
OTHER INFECTIONS
* arthritis (frequent complication of meningococcaemia)
* conjunctivitis
* sinusitis
* endocarditis
* primary pneumonia
CLINICAL SIGNIFICANCE -
OTHER NEISSERIA SPP.
- rarely cause significant infections including osteomyelitis,
pleuropulmonary infections, conjunctivitis, pericarditis, urethritis * usually in immunocompromised hosts
CLINICAL SIGNIFICANCE -
MORAXELLA CATARRHALIS
- causative agent of otitis media, sinusitis, bronchitis, pneumonia in children and the elderly
- important cause of exacerbations in COPD (chronic obstructive pulmonary disease)
- causative agent of bacteraemia, endocarditis, meningitis,
conjunctivitis, urogenital tract infections, wound infections in
immunocompromised persons
COLLECTION, TRANSPORT, AND STORAGE OF SPECIMENS - NEISSERIA GONORRHOEAE
- Stuart’s transport medium
- Transgrow medium
- JEMBEC and Gono-Pak
COLLECTION, TRANSPORT, AND STORAGE OF SPECIMENS - NEISSERIA MENINGITIDIS
- CSF specimens should be hand-carried to laboratory
after collection, must not be refrigerated
CULTURE MEDIA Neisseria and Moraxella Catarrhalis
Selective media
* Modified Thayer-Martin (MTM) and Martin-Lewis (ML) media contain:−chocolate agar based medium
−vancomycin (to inhibit gram-positive bacteria) −colistin (to inhibit gram-negative bacteria, including commensal Neisseria spp.) −trimethoprim lactate (to inhibit swarming Proteus spp.) − nystatin or anisomycin (to inhibit fungi)
* New York City (NYC) medium
* GC-Lect medium
Non-selective media
* 5% sheep blood agar medium
* Chocolate agar medium
