THE GENUS Neisseria - LF

THE GENUS Neisseria - LF


Neisseriae are gramnegative cocciarranged in pairs, so they are diplococci This genus includes two species pathogenic forhumans:– N. gonorrhoeae (s.c. gonococci)– N. meningitidis (s.c. meningococci) Other species (N. lactamica, N. sicca, N. subflava,N. flavescens) are normal inhabitants of the humanupper respiratory tract (oropharyngeal area) ascommensals. They are of importance for thedifferential diagnosis.

General characteristics ofNeisseria spp.AerobicGram-negative cocci often arranged inpairs (diplococci) with adjacent sidesflattened (like coffe beans)Oxidase positiveMost catalase positiveNonmotile

Diseases associated withNeisseria meningitidisFollowing dissemination of virulentmicroorganisms from the nasopharynx: Meningitis Septicemia (meningococcemia) with orwithout meningitis Meningoencephalitis Pneumonia Arthritis Urethritis

The N. meningitidis growth on solid media (agar)

Neisseria meningitidispathogenity The meningococci are exclusively humanpathogens. They can either exist as an apperantlyharmless member of normal microflora or cancause acute disease.

Meningococci can cause: Inflammations of nasopharyngeal mucousmembranes (from nasopharyngitis to purulentrhinitis). Septicemia without meningitis (meningococcipenetrate into the blood stream in a relatively smallnumber of patients). Meningococcal pneumonia, myocarditis, arthritis. Meningitis.

Neisseria meningitidisepidemiology Source:– only a human (healthy or sick) Spreading:– transmission of meningococci is facilitated by respiratorydroplets and requires closed and prolonged contact withcarriers Site of entrance:– upper respiratory tract– the frequency of meningococcal carriership in healthypopulation is varying about 10% during nonepidemicperiod Meningococcal meningitis is a worldwide problem.

Neisseria meningitidis– clinical symptomsdiagnosis– examination of liquor after lumbar punctionor examination of other specimens(Gram staining, cultivation)– serological examination (e.g. latexagglutination)

Neisseria meningitidistreatment penicillin G is the drug of choice300 000 IU/kg/day q4h, usually 4x4-5 mil IU 3 rd generation cephalosporins:– ceftriaxone 100 mg/kg/day in 1-2 doses– cefotaxime 200-300 mg/kg/day in 3 doses– ceftazidime 150 mg/kg/day in 3 doses

N. gonorrhoeae is exlusively a humanpathogen.It is never found as a normal commensalalthough a proportion of those infected,particularly women, may remainasymptomatic. These individuals, maydevelop systemic or ascending infectionat a lated stage.

The commonest clinical presentation of thedisease is acute urethritis a few days afterunprotected vaginal or anal sexual intercourse. Asymptomatic infection is rare in the activeman. In women with vaginal infection, only halfmay have symptoms of discharge and dysuria.Asymptomatic carriage in women is common,especially in the endocervical canal.

Neisseria gonorrhoeaediagnosisclinical symtomsGram stainingcultivation and biochemical tests

Neisseria gonorrhoeaetreatment tetracyclines (doxycycline) fluoroquinolones (ciprofloxacin, ofloxacin,levofloxacin) spectinomycin 3 rd generation cephalosporins– e.g. ceftriaxone, cefotaxime others