Pyogenic cocci Neisseriae

Pyogenic cocci






Neisseriae





By: Dr. Salma
Neisseriae Characters :- Gram-negative diplococci, individual cocci are kidney-shaped, non motile non hemolytic and non pigmented, Colonies are opaque or transparent. There are two pathogenic species for humans : 1. Neisseria gonorrhoeae (Gonococci) GC, the causative agent of gonorrhea, neonatal conjunctivitis (ophthalmia neonatorum) and pelvic inflammatory disease (PID). 2. Neisseria meningitidis (Meningococci) MC, the causative agent of meningitis and meningococcemia.
all N. Spp. Are oxidase-positive (ie. Produce oxidase enzyme ).
The oxidase is a key test for identifying them. When bacteria are spotted on a filter paper soaked with tetramethylpara phenylenediamine (oxidase reagent), The Neisseriae rapidly run dark purple. The growth of both organisms(GC and MC) is inhibited by toxic trace metals and fatty acids found in certain culture media e. g., blood agar plate, they are therefore culture on chocolat agar containing blood heated to 80°c. The organisms are rapidly killed by drying, sunlight, moist heat and many disinfectants. (they are fastidious).
Non pathogenic e. g. Moraxella catarrhalis was previously named Branhamella catarrhalis (Neisseria catarrhalis).
Neisseria gonorrhoeae (Gonococci) GC.
Classification :- On the basis of morphology and their colonial mutation, there are four biotypes : (T1, T2) virulent small brown colonies (pilitated gonococci) posses pili which are adherence factors. (T3, T4) a virulent large non pigmented colonies (no pilitated gonococci). Virulence factors (antigenic structure) :- 1. pili acts as adhesions. 2. porprotien. 3. opaproteins. 4. Rmp(protein111).
5. Iipopolysaccharide(in gonococei is called a lipooligosaccharide, LOS, as endotoxin). 6. IGA1 protease.