NeissreriaGram negative diplococcic bean or kidney shape and attach each other it is non motile ,non sporing and it is capsulated it is strict oxdiase positive.*species: (a)The main species of medical importance are:(1) Neisseria meningitidis.(2) Neisseria gonorrhoeae.(b) non pathogenic: (1) Neisseria catarrhalis(2) Neisseria*Normal habitat-The N.meningitidis can be found as commensal in the nasopharynx up 2-10% of healthy people .-N.gonorrhoeae can be found as commensal in urogential tract-Neisseria catarrhalis be found as commensal in mucus membrane of throat and nasopharynx. Neisseria meningitidis(meningococcal)(meningococci)Meningitis caused by gram negative meningococci it is causal pyogenic (Purulent) meningitis.*morphology : Gram negative diplococci bean or kidney shape measuring about eighteen micrometer in diameter its non motile non sporing and its capsulated it having ten capsule polysaccharide antigen A ,B ,C, D ,X ,Y ,Z ,29E ,W135 the most pathogenic one its A,B. these antigens it will be demonstrated by quellung reaction.

*Pathogenicity of this microbe: #The N.meningitidis it cause meningitis.

Symptoms of meningitis (1)High fever (2)Rigid neck.#Pyogenic (purulent) Bacteraemia .#Endocarditis.#Arthritis. *Laboratory diagnosis: (1)Specimen : Cerebrospinal fluid CSF ,blood for culture pus from an infected joint or aspirate from skin lesions. -Glucose is low -protein is high.-WBCS 200X106 /L .(2)stained smear Gram stained smear from the sediment of centrifugeCSF or any other specimen shows typical gram negative intracellular and extracellular diplococcic.(3) Culture The organism grows best on enriched medium e.g chocolate agar and in moist carbon dioxide enriched atmosphere(5-10% co2 ). The optimum temperature for growth36C with a ranfe of 25-42C.N.meningitidis is very fragile and will die readily outside the body temperature it should therefore be cultured without delay.CSF*culture on serum +glucose medium (primary) The colony of neisseria on blood agar its small circular smooth low convex translucent gray in colour non haemolytic.On the chocolate the same appearances.(4)Gram stain.(5)Biochemical tests *Oxidase test (+Ve).*Carbohydrate utilization test: N.meningitidis attacks carbohydrates oxidatively. It utilizes glucose and maltose with no action on lactose or sucrose.Neisseria gonorrhoeaeIts caused gonorrhoeae , it is sexually transmitted disease, Gram negative diplococcic bean or kidney shape .-In men infects the urethra causing dysuria and acute urethritis with a purulent discharge. The organism may spread to the prostate ,bladder and epididymes causing inflammation and swelling. Epididymitis may lead to sterility. -women infects the cervix ,urethra ,vulva and rectum. Infection may lead to ectopic pregnancy or sterility.

-Young female: Vulvovaginitis .-New born infant :ophthalmia neonatorum.*Laboratory diagnosis: (1)Specimen : uretheral and cervical exudates and if indicated rectal swabs foe microscopy and culture .from infants an eye swabs is required.(2)Culture: selective media 1-Modified new York city (MNYC) medium.2.Modified Thayer-martin(MTM) medium.(3)Biochemical reactions *Oxidase test (+Ve)*carbohydrate fermentation :ferment glucose only without gas .(4) Antibiotic sensitivity N.gonorrhoeae like other neisseriae is nprmally sensitive to penicillin ,ampicillin , tetracycline and many strains producing b lactamase so penicillin is no longer the antibiotic of choice.Mycobacteria Mycobacteria are slender straight or slightly curved non motile rods are aerobic non capsulated and non sporing. They do not stain easily bit once stained they resist decolourisation with dilute mineral acids they are there fore referred to as acid fast bacilli(AFB).The acid fastness of mycobacteria is due to their thick cell wall which is composed of waxes and lipids that have a high content of mycolic fatty acids. This complex cell wall is also the reason why it is difficult to stain mycobacteria by techniques other than the Ziehl-Neelsen. For example mycobacteria in gram stained smears stain poorly(Gram positive)or not at all.*Type species M.tuberculosis(tubercle bacilli)More than forty species of mycobacterium are recogbised.M.tuberculosis complex is the term used to describe M.tuberculosis ,M.africanum and M.bovis collectively.*Atypical mycobacteria saprophytic mycobactria which are non-tubercle bacilli and isolated from a number of environmental sources are loosely grouped under the term atypical or anonymous mycobacteria. Most of these organisms have now been speciated and the term atypical or anonymous is no longer used instead they are referred to as environmental mycibacteria.