Session 4 Bact (G+ve Rods Non Spore) PDF

Bact: G+ve rods. (Non spore) Micro 3: 4th Year Gram positive rods Non-spore forming Spore forming...

Bact: G+ve rods. (Non spore) Micro 3: 4th Year Gram positive rods Non-spore forming Spore forming Aerobic Aerobic Anaerobic Corynebacterium diphtheriae  Bacillus anthracis “Clostridium”  Listeria monocytogenes  Bacillus cereus  C. tetani C. perfringens Anaerobic  C. botulinum C. difficile Propionibacterium species Aerobic-non-spore forming: Corynebacterium diphtheriae: Gram-positive rod, non-motile Properties (Chinese letters): Club shaped rods with beaded appearance consist of highly polymerized rich polyphosphateStained bluish with methylene blue (metachromatic). [IMP] Transmission by Respiratory droplets Epidemiology: disease of childhood  Toxigenic strains family of Corynebacteriophages carry gene for diphtheria exotoxin. Diphteria exotoxin: Consists of 2 fragments Fragment A: catalytic inhibits elongation factor 2inhibit protein synthesis in eukaryotic cells Virulence Fragment B: binds to cell surface R  facilitates the delivery of fragment A to the cytosol Factors: Based on two primary determinants: [IMP] 1- ability to colonize in the nasopharyngeal (encoded by the bacteria) 2- ability to produce diphteria exotoxin (encoded by the corynebacteriophage) Non-toxigenic strains rarely associated with clinical disease. Infection starts in the nose a purulent nasal discharge. Spreads to involve the pharynx covered by pseudo-membranemade up of bacteria, epithelial cells, leucocytes, fibrin and bloodDifficulty in respiration Pathogenesis Life-threatening systemic complications: Distant effects on the heart and the nervous system. [IMP] The action of diphtheria toxin on peripheral motor neurons and the myocardium cause: loss of motor function (e.g. difficulty in swallowing) Congestive heart failure session 4 1 Micro 3: 4th Year ❖ “Diphtheria”: a highly contagious diseaseaffect Upper RT ❖ The incubation period is 2-6 days. ❖ Asymptomatic carriersimportant source of infection ❖ Two types of diphteria: nasopharyngeal and cutaneous: due to local inflammation effect in the upper respiratory tract and skin Clinical symptoms: 1-in nasopharyngeal diphteria: Low-grade fever Cervical lymph nodes: Enlargement is common and the surrounding edema of the Disease subcutaneous tissues may cause a “Bull neck” appearance. Rarely, in cases of pharyngeal diphtheria, necrosis  cause perforation. 2-in cutaneous diphteria: The skin lesions covered by gray brown pseudomembrane. Throat swab: Stain: Gram-positive rods Culture: on Loffler’s serum or McLeod’s medium (tellurite blood agar medium) Lab Diagnosis Test for toxigenicity: [IMP] 1- Elek’s test (in vitro): differentiate between toxigenic & non-toxigenic diphteria. 2- Guinea pig inoculation (in vivo): The M.O. is injected into both guinea pigs. The nonprotected one dies while the protected one remains alive. Must proceed rapidly. 1- Antitoxin (20,000-100,000 units) intravenously 2- Penicillin or erythromycin 3- Tracheotomy may be required In laryngeal diphtheria. Treatment session 4 2 Micro 3: 4th Year a) Active immunization: Vaccine is mixed with pertussis and tetanus (DPT) b) Passive immunization with diphtheria antitoxin : [IMP]Schick’s test: Method for determining susceptibility to diphtheria. 0.1 ml diphtheria Positive reaction False Positive reaction toxin is injected into Redness at the site of injection after 3 days the skin of the (Absence of circulating antibody) (Hypersensitivity to the toxin). forearm: use of a control injection of the same Positive reaction False Positive reaction amount of heated No Redness Redness toxin (toxoid) into the other forearm Interpretation of test: 1. Positive: when the test results in a wheal (raised mark on skin) of 5-10 mm diameter. reaching its peak in 4-7 days. Prevention The control arm shows no reaction. lacks antibodies against the toxin susceptible to the disease. 2. Pseudo-positive: - only a red colored inflammation (erythema)and it disappears within 4 days. - happens on both the arms hypersensitive to the toxin. 3. Negative reaction: Indicates that the person is immune. 4. Combined reaction: the erythema fades off after 4 days only in the control arm. - It progresses on the test arm to a typical positive. - The subject is interpreted to be both susceptible and hypersensitive. session 4 3 Micro 3: 4th Year Listeria monocytogenes facultative intracellular: Can move from cell to cell without exposed to antibodies. General characters catalase positive - beta-hemolytic Epidemiology - Immunocompromised adults & pregnancy transmission: via the fecal-oral route Important food borne pathogen: can grow at refrigerator temperatures. produce Biofilms ability to survive harsh environments. binds host cells via host protein cadherin (epithelial attachment Surface proteins protein that is found in the BBB & placenta & GIT) allowing entry "internalins" into the cell. (A and B) (the bacteria can infect neonates and cause meningitis) pore-forming cytotoxic protein Cytotoxic Phagocytized L. monocytogenes can lyse the internalized protein: vacuole "Listeriolysin O” LLO: responsible for the beta-hemolysis on blood agar. - L. monocytogenes replicates rapidly in the host cytosol and Virulence the bacterial densely covers its surface with the bacterial protein ActA factors[IMP] protein ActA. - induces host actin polymerization allows L. monocytogenes to move rapidly between cellsavoid antibody detection. Two types of Listeria monocytogenes movement[IMP] session 4 4 Micro 3: 4th Year Adult listeriosis Pregnant women[IMP] in immunocompromised adults especially Infected mothers are asymptomatic or has with renal transplantation an influenza-like illness, in fetus severe. a) Early onset syndrome: include: meningitis, septicemia, pyogenic granulomas in multiple organs endocarditis. b) Late onset syndrome: meningitis in the young (neonates), meningitis 1-4 weeks after delivery & suffer Pathogenesis: elderly, and immunocompromised from physical retardation (neurological Healthy individuals infected with L. damage) monocytogenes typically have a self- limiting gastrointestinal infection with fever and diarrhea. Febrile gastroenteritis: characterized by watery diarrhea, fever, and no vomiting. 1. Specimen: blood sample, cerebrospinal fluid (CSF). 2. Gram stain: small gram +ve rods Diagnosis 3. Test for motility: Tumbling movement ( at 30 C or less) 4. Cultivation on blood agar: grey, ß-hemolytic colonies. Treatment: by a combined therapy of ampicillin and gentamicin. Anaerobic non-spore forming: Gram positive bacilli Propionibacterium species - Members of the normal flora of skin. - Propionibacterium acnes (opportunistic pathogen) causes Acne vulgaris - Produce lipases that split free fatty acids off from skin lipidstissue inflammation acne formation. session 4 5