CNS Microbiology PDF 2024 Past Notes

‫مكتب الدقة‬ ‫للخدمات المكتبية واالعمال االدارية‬ ‫‪CNS Microbiology‬‬ ‫السعر ‪ 1‬د‬ ‫التاري خ ‪4242 / 24 /42‬‬ ‫طبق – كلية الطب ر‬ ‫البشي‬ ‫ج امعة ر‬ ‫ميكرو بيولوج للسنة ثالثة موديول الدفعة ‪11‬‬ ‫ر‬...

‫مكتب الدقة‬ ‫للخدمات المكتبية واالعمال االدارية‬ ‫‪CNS Microbiology‬‬ ‫السعر ‪ 1‬د‬ ‫التاري خ ‪4242 / 24 /42‬‬ ‫طبق – كلية الطب ر‬ ‫البشي‬ ‫ج امعة ر‬ ‫ميكرو بيولوج للسنة ثالثة موديول الدفعة ‪11‬‬ ‫ر‬ ‫المحاضة االول (بلوك ‪)CNS‬‬ ‫للدكتور ‪ :‬فارس الكريمي‬ ‫العنوان ‪ :‬ح الحرية مقابل كلية الطب ر‬ ‫البشي‬ ‫ي‬ ‫‪EDITION 2024‬‬ CNS Microbiology Dr. Fares Elkarimi 1445 ،‫ شعبان‬16 25/02/2024 Dr. Fares Elkarimi Haemophilus This is a group of small, gram-negative, pleomorphic bacteria that require enriched media, usually containing blood or its derivatives, for isolation. Haemophilus influenzae type b is an important human pathogen; Haemophilus ducreyi, sexually transmitted pathogen, causes chancroid; other Haemophilus species are among the normal microbiota of mucous membranes and only occasionally cause disease. Haemophilus Influenzae Non-capsulated Haemophilus influenzae is found on the mucous membranes of the upper respiratory tract in humans. Capsulated is an important cause of meningitis in children and causes upper and lower respiratory tract infections in children and adults. Morphology: The organism is gram negative, short coccoid bacilli, non-motile, sometimes occurring in pairs or short chains. Some types are capsulated. Pleomorphic forms are common in cultures. Culture & Growth Characteristics: Facultative anaerobe. On chocolate agar, flat, grayish brown colonies, present after 24 hours of incubation. 1 25/02/2024 Dr. Fares Elkarimi H influenzae does not grow on sheep blood agar except around colonies of staphylococci (“satellite phenomenon”). H. influenzae requires hemin (factor X) and nicotinamide adenine dinucleotide ''NAD'' (factor V) for growth. Other Haemophilus species require only NAD and therefore grow on blood agar. Biochemical reactions: catalase and oxidase are positive. Antigenic Structure: The capsule is the major virulence factor. capsulated H influenzae contains capsular polysaccharides of one of six types (a–f). H influenzae type b (Hib) is the most pathogenic. Pathogenesis: The organism enters through the URT. It produces an IgA protease, which degrades secretory IgA, thus facilitating attachment to the respiratory mucosa, resulting in colonization or infection, e.g. otitis media, sinusitis or pneumonia. It may spread via the blood stream causing meningitis. Capsulated strains mainly Hib causes meningitis, epiglottitis, septic arthritis in children below 5 years. Diagnosis: - Specimens are pus, sputum and CSF. - Smears are stained with gram, short coccoid bacilli. - Antigen detection in CSF by latex agglutination test. - PCR. Treatment: Essentially all strains are susceptible to the third generation cephalosporins. Cefotaxime or Ceftriaxone are given excellent results. Prophylaxis: - Hib vaccine prevents serious infections caused by H influenzae type b. Hib vaccination is recommended for all children younger than 5 years old Hib vaccination is recommended for all children younger than 5 years old (2,4,6,12-15 months). - Meningitis can be prevented by giving rifampicin to children in close contact with patients. 2 25/02/2024 Dr. Fares Elkarimi Before the introduction of the vaccine in 1992, around one in every 600 children developed some form of invasive Hib disease before their fifth birthday. In 1991, the year before the vaccine was introduced, there were 759 reported cases of invasive Hib in children under five in England. In 2014, there were only 2 confirmed cases in this age group. http://vk.ovg.ox.ac.uk/hib-disease 3 25/02/2024 Dr. Fares Elkarimi Rabies virus Rabies is an acute infection of central nervous system, which is usually fatal. Mortality rate from rabies every year worldwide reaches up to 45.000. The highest mortality rate is in India (35.000), China (6.000) and Bangladesh (2.000). Properties of rabies Virus It is the type species of the Lyssavirus genus in the family rhabdoviridae. It is ssRNA virus, bullet-shape, about 180nm in length, enveloped and has a helical symmetry. The surface glycoprotein spikes binds specifically to receptors of the affected cells. Pathogenesis Rabies transmitted to man through the bite of an infected animal, usually a dog. The virus particles introduced in saliva of the rabid animal and replicate locally at the site of the bite, then travel via peripheral nerves to reach the brain where they multiply and cause the damage (encephalitis). The inclusion bodies appear in the cytoplasm of the affected cells called “Negri bodies”. The viruses then travel down in the peripheral nerves to the salivary glands. 4 25/02/2024 Dr. Fares Elkarimi Clinical features The incubation period is long, usually from 2 to 24 weeks but sometimes can be shorter or much longer depending on the distance of bite to the brain, severity of the wound and the amount of virus introduced. Prodrome stage: symptoms include; headache, malaise, irritability and personality changes. Excitement stage: symptoms are nervousness, over-activity, increased lacrimation, salivation and hydrophobia due to severe spasm of throat muscles on swallowing. Finally, infected patient develops convulsion, paralysis, coma and death due to cardiac or respiratory arrest. There is no viremia. 5 25/02/2024 Dr. Fares Elkarimi Diagnosis A smear obtained from brain or parotid gland of suspected animal, stained with fluorescin-labelled anti-rabies immunoglobulin and examined for Negri bodies. Specific antibodies to rabies can be detected by ELISA or immunofluorescence assays. Tests performed on serum or cerebrospinal fluid. PCR. A, Negri body (arrow) in the cytoplasm of a Purkinje cell in the cerebellar cortex. Management of rabies: 1- The wound is immediately cleaned with soap and water and irrigated by virucidal agent. 2- Antibiotics to control bacterial infections. 3- Post-exposure prophylaxis by vaccination and passive immunization with rabies immunoglobulin. Types of vaccine: 1- Diploid cell vaccine (HDCV) (inactivated). 2- Primary chick-embryo cell vaccine (PCECV) (inactivated). 3- Primary Vero cell vaccine (PVRV). Pre-exposure prophylaxis A dose of HDCV is given, one ml intramuscularly or 0.1 ml intradermally on days 0, 7 and 28 booster doses. The same dose given every 2 years if continued protection is needed. 6