Gram-Negative Cocci :Neisseria & Vibrio

Transcription

1 Sulaimani University College of Pharmacy Microbiology Lec. 7 Gram-Negative Cocci :Neisseria & Vibrio Dr. Abdullah Ahmed Hama PhD. Microbiology/Molecular Parasitology abdullah.hama@spu.edu.iq 1

2 Neisseria pp. Neisseria are anaerobic Gram-negative, coffee-bean-shaped cocci that are usually paired (diplococci) Gonococci can be grown on moist culture mediums enriched with protein (blood). The 5 10% CO2. atmosphere for primary culturing must contain They are non-motile. non spore-forming. oxidase-positive. All Neisseria species possess pili and outer membrane proteins (OMPs).

3 Neisseria spp. The genus Neisseria contains two important human pathogens: 1. Neisseria meningitidis. 2. Neisseria gonorrhoeae. N. meningitidis (meningococcus): Morphology and culture: Meningococci are Gram-negative, coffeebeanshaped,cocci that are frequently pleomorphic and have a diameter of 1 um. They are nonmotile and feature a polysaccharide capsule. Growing meningococci in cultures requires mediums containing blood. A concentration of 5 10% CO2 encourages proliferation. Antigen structure. Serogroups A, B, C, D, etc, are differentiated based on the capsule chemical structure and. Epidemics are caused mainly by strains of serogroup A, sometimes by B strains as well and, has a prominent polysaccharide capsule that enhances virulence by its antiphagocytic action.transmission occurs by inhalation of respiratory droplets.

4 N. meningitidis (meningococcus) Pathogenesis: Meningococci are parasites of the nasopharynx. These microorganisms are carried by 5 10% of the population. Pathogen can invade the mucosa by means of parasite directed endocytosis. pathogens can also infect the lungs, the endocardium, or major joints. Onset of the meningitis is usually sudden, after an incubation period of two to three days, with severe headache, fever, neck stiffness, and severe malaise. Severe hemorrhagic sepsis sometimes develops (Waterhouse- Friedrichsen syndrome).

5 N. meningitidis (meningococcus) virulence factors 1. A polysaccharide capsule 2. Endotoxin (LPS) 3. Immunoglobulin A (IgA) protease Clinical Findings: The two most important manifestations of disease are meningococcal meningitis: is most common infection. Meningococcemia sometimes occurs,the most severe form of meningococcemia is the life-threatening Waterhouse- Friderichsen syndrome.

6 Laboratory Diagnosis: The diagnosis requires detection of the pathogen in cerebrospinal fluid or blood by means of microscopy and culturing techniques. For success in culturing, the sample must be used to inoculate blood agar without delay. Identification of the pathogen is based on identification of metabolic properties. The slide agglutination test is used to determine the serogroup. Latex agglutination or coagglutination can be used for direct antigen detection in cerebrospinal fluid.

7 Treatment: Penicillin has long been the treatment of choice for meningococcal infections because of its high antimeningococcal activity and good CSF penetration. Prevention Chemoprophylaxis and immunization. There are two forms of the meningococcal vaccine, both of which contain the capsular polysaccharide immunogens: (Menactra) (Menomune)

8 Neisseria gonorrhoeae.(gonococci) N. gonorrhoeae grows well only on chocolate agar and on specialized medium enriched to ensure its growth. It requires carbon dioxide supplementation. Gonococci possess numerous pili that extend through and beyond the outer membrane. Gonococci have no capsules Route of transmission: The organism is usually transmitted sexually. Newborns can be infected during birth Gonorrhea is usually symptomatic in men but often asymptomatic in women.

9 Neisseria gonorrhoeae (Gonococci) virulence factors: In the cell wall are LPS and LOS (a modified form of endotoxin), and The outer membrane proteins(iga protease ). Diseases : Gonococci cause both localized infections, usually in the genital tract, and disseminated infections with seeding of various organs Clinical Findings: 1. Genital Gonorrhea 2. Pelvic Inflammatory Disease (PID) 3. Disseminated Gonococcal Infection (DGI) 4. Gonococcal bacteremia

10 Pathogenesis and infection Gonorrhea is a sexually transmitted disease. The pathogens penetrate into the urogenital mucosa, causing a local purulent infection. In men, the prostate and epididymis can also become infected. In women, the gonococci can also cause salpingitis, oophoritis, or even peritonitis. Gonococci reaching the conjunctival membrane may cause a purulent conjunctivitis, seen mainly in newborn children. Gonococci can also infect the rectal or pharyngeal mucosa, may also cause arthritis or even endocarditis. 10

11 Immune defenses: against granulocytes are based on the outer membrane porin Portein that prevents the phagosome from fusing with lysosomes, resulting in the survival and proliferation of phagocytosed gonococci in granulocytes. The lipo- oligosaccharide (LOS) in the outer membrane is responsible for resistance to complement (serum resistance) as well as for the inflammatory tissue reaction in a manner analogous to the more complexly structured LPS of enterobacteria. Gonococci can capture iron from the siderophilic proteins lactoferrin and transferrin, accumulating it inside the bacterial cells to facilitate their rapid proliferation. An IgA1 protease produced by the gonococci hydrolyzes secretor antibodies in the mucosal secretions.

12 1. gram smear 2. Culture: Diagnosis: The method of choice is detection of the pathogens by means of methylene blue and gram staining and culturing. Gonococci are sensitive in cultures and the material must be used immediately after they are obtained to inoculate on Thayer-Martin blood agar with antibiotics added to eliminate accompanying flora. Urethra and cervix are preferred culture sites. The organism grows on chocolate agar. The selective medium (eg, Thayer - Martin agar) is an enriched selective chocolate agar with antibiotics.

13 Neisseria gonorrhoeae (Gonococci) Treatment The treatment of gonorrhea, as with other sexually transmitted diseases, includes individual patient issues as well as public health concerns. Ceftriaxone is the treatment of choice in uncomplicated gonococcal infections. Prevention The prevention of gonorrhea involves the use of condoms and the prompt treatment of symptomatic patients and their contacts. No vaccine is available.

14 Vibrio Vibrios are curved, comma shaped, Gram-negative rods commonly found in saltwater. They are highly motile with a single polar flagellum. oxidase-positive. they can grow under aerobic or anaerobic conditions. Vibrio cholerae is the major pathogen in this genus, is the cause of cholera (water-loss diarrhea). Vibrio parahaemolyticus causes diarrhea associated with eating raw or improperly cooked seafood.

15 Vibrio cholerae Virulence factor:cholera Toxin.

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17 Vibrio cholerae Route of transmission: Epidemic cholera is spread primarily by fecal oral route. The dominant strain of the 20th century was the El Tor biotype. Disease: V. cholera is the cause of cholera (rice-water stools) Diagnosis: Typical clinical features. A bacteriologic diagnosis is accomplished by isolation of V. cholerae from the stool. its isolation is enhanced by a selective medium (thiosulfate-citrate-bile salt-sucrose agar).

18 Treatment: Vibrio cholerae Treatment consists of prompt, adequate replacement of water and electrolytes, either orally or intravenously. Antimicrobial therapy can reduce duration and severity of diarrhea eg: Doxycycline. Prevention Water sanitation and clean food supply. Secondary local measures such as boiling and chlorination of water during epidemics are required. The use of tetracycline for prevention is effective in close contacts