Gram Negative Cocci

Gram Negative Cocci Moraxella Neisseriae N. meningitidis N. gonorrhoeae The genus Neisseria consists of gram-ve areobic cocci 2 Neisseria species are pathogenic for humans N.gonorrhoeae & N.meningitidis Cause PID Commonly known as meningococcus. Cause meningitis. Commonly known as gonococcus Cause gonorrhea, Ophthalmia neonatorum

Neisseria gonorrhoeae. Found inside (intracellular) and outside (extracellular) of pus cells. Non spore forming. Non motile. Has no capsule. Can’t grow in ordinary media, need chocolate agar and 5 % CO2. Not part of the normal flora.

Culturing of Neisseria gonorrhoeae It needs 48h incubation & 5-10 CO2 Culturing of Neisseria gonorrhoeae Capnophlic organism Produce tan, moist, glistening colonies on chocolate agar. Dose not grow on Blood agar

Neisseria gonorrhoeae It is very sensitive to environment, specimen should be transported to the lab as soon as possible. Never refrigerate specimen. A transport media should be used.

This is done through many surface structures. Pathogenic Neisseria have an extraordinary capability to vary their surface structures. This is done to: Protect the organism form the host immune response. It affects the function of factors that interact with host cells (interaction with epith cells, phagocytic cells, adherence to cells and cell invasion.) This is done through many surface structures.

Structure of N.gonorrhoeae Pili Lipoligosaccharide (LOS) Porin proteins. Opacity proteins (Opa)

Structure of N. gonorrhoeae 1) Pili: Hair like projection made of repeating peptide subunits called pilin. The organism can produce antigenically different pilin molecules at high frequency.

Structure of N. gonorrhoeae. Pili The pilin genes are resent in the chromosome of every strain, they undergo recombination exchange. Some are silent (pilS) and some are complete and able to express pilin (pilE). When recombination between expression and silent loci results in the donation of new sequences to an expression locus. The result can be expression of a pilin with changes in its amino acid composition and thus its antigenicity. This process known as antigenic variation by gene conversion

Structure of N. gonorrhoeae 2) Lipooligosaccharide (LOS): Lipopolysaccharides (LPS) constitute a family of toxic glycolipids which are integral in the outer membranes of gram-negative organisms. These molecules are critical for the integrity and functioning of the outer membrane. They are also important surface antigens and are highly immunostimulatory. Systemic distribution of LPS can lead to toxic shock. N.gonorrheae have lipooligosaccharide which is more branched and is also capable of high-frequency antigenic varation. The gonococcus variably expresses some of the genes encoding the glycosyl transfersases needed for LOS biosynthesis, and this results in rapid and reversible alterations in the oligosaccharide structure.

Structure of N. gonorrhoeae 3) Porin Proteins (Por): It is an important factor in gonococcal invasion of epithelial mucosa cells. Porin proteins are not subject to high frequency antigenic variation like other outer membrane Ag.

Structure of N. gonorrhoeae 4) Opacity proteins (Opa): Gonococus have multiple Opa proteins. Each encoded by separate gene. Those Opa proteins help also in adherance. Different Opa proteins bind to distinct receptors on host cells, therefore shifting expression from one Opa protein to another results in change sin host cell relationship. Various combinations of these genes may be either “on” or “of” at any one time.

If the host has antibodies against one or more of these proteins they would be removed and the infecting population would shift to cells expressing pili or Opas to which there is no immunologic experience.

Immune responses to gonococcus after natural infection ordinarily result in little immunity to re-infection, due to antigenic variation of the gonococcus, and redirection or suppression of immune responses.

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Pathogenesis of N. gonorrhoeae. Pili & Opa proteins  facilitate adhesion. Produce IgA protease  cleaves IgA1. The organism need Iron for growth and survival  the organism express a specific transport system that remove iron from transferrin and hemoglobin.

Clinical significance of N. gonorrhoeae. Gonorrhea(e.g urethritis, cervicitis) Rectal infections. Pharyngitis. Ophthalmia neonaturom. Disseminated infection.

Treatment & Prevention of N. gonorrhoeae The organism shows resistant to penicillin and tetracycline (PPNG penicillinase producing N.gonorrhoeae). Usually treatment is by third generation cephalosporin's (eg. ceftriaxone). Many patient with gonorrhea have coexisting chlamydial infections.

Ophthalmia neonatorum Contamination of infants eye during labor through the birth canal of mother Conjunctivitis with mucopurulent discharge May cause blindness if not treated

Ophthalmia neonatorum Treatment: Prophylactic treatment: After cleansing of face and lid of baby apply 1% silver nitrate solution, or other antibiotic ointment. Monitor the baby’s eye in the first week. If the mother is known to be colonized systemic antibiotic may be given to the new born baby.

Ophthalmia neonatorum Treatment: Curative treatment: Frequent washing with normal saline. Applying antibiotic to the eye every hour (due to general resistance to penicillin and tetracycline) Systemic treatment with antibiotic is needed (e.g. ceftriaxone or cephotaxime; either IV or IM) No vaccine is available Applying antibiotic to the eye every hour (due to general resistance to penicillin , topical tetracycline , gentamicin, bacitracin & fluoroquinolone is recommended).

Neisseria meningitidis One of the most frequent causes of meningitis. Symptoms have rapid onset and great intensity (high fever , headache, & rash). Outbreaks most common in winter and early spring. Favored by close contact between individuals. It tend to strike young, previously well individuals and can progress over a matter of hours to death.

N. meningitidis It looks like N. gonorrhoeae. Also have pili help it to attaches to nasopharyngeal mucosa. It has a polysaccharide capsule which is the most important virulence factor since it inhibit phagocytosis.

Structure of N. meningitidis. There is around 13 different capsular polysaccharide type called (serogroups). Most infections are caused by serogroups A, B, C, W-135 and Y. MCV4 is a tetravalent vaccine that is used nowadays. It is sensitive to penicillin.

Serogroup Classification Comment A Usually responsible for massive epidemics in developing countries. B Dose not evoke an effective immune response. B, C Responsible for most endemic meningitis in the united states. A, C, W-135, Y Effective capsular vaccine is available.

N. Meningitidis VS N. gonorrhoeae Species Portal of Entry Maltose fermentation B-lactamase production Available vaccine N. Meningitidis Respiratory tract + None N. gonorrhoeae Genital tract - Yes Polysaccharide capsule N.meningitides + N.gono -

N. Meningitidis VS N. gonorrhoeae Polysaccharide capsule N.meningitides + N.gono - N. gonorrhea utilizes glucose, change color from red to yellow, and N. meningitidies utilizes gulcose and maltose

Moraxella Gram negative cocobacilli Arranged in pairs. Aerobic. Oxidase positive (like Neisseria spp.). Fastidious organism. Dose not ferment carbohydrate. Positive Oxidase test

Moraxella It is a normal flora in the upper respiratory tract. Infection is usually caused by the patient’s endogenous strains. Person-to person transmission may also be possible. They can grow on blood agar plate .

Moraxella The most important species is M. catarrhalis. It can cause infections of the respiratory system , middle ear, eye or CNS and joints. Can cause angular conjunctivitis: History of collection of dirty-white foamy discharge at the angles.