Pharm D Program (2023/2024) Medical Microbiology Lecture Notes PDF

Pharm D Program (2023/2024) 22 July 2024 www.su.edu.eg 1  Pharm PharmDDProgram Program (2023/2024) (2023/2024)...

Pharm D Program (2023/2024) 22 July 2024 www.su.edu.eg 1  Pharm PharmDDProgram Program (2023/2024) (2023/2024) (PM 704) Lecture No. (8) Gram Negative Bacteria (2) Acid Fast Bacteria By Professor Yasser El Mohammadi 22 July 2024 www.su.edu.eg 2  Pharm PharmDDProgram Program (2023/2024) (2023/2024) Lecture’s Aim To help the student to get a detailed knowledge about the most dangerous and prevalent types of pathogenic gram negative bacteria as well as acid fast bacteria and their corresponding diseases. 22 July 2024 www.su.edu.eg 3  Pharm PharmDDProgram Program (2023/2024) (2023/2024) Lecture’s Competencies To enable the student to 1- Discover the most important Gram negative bacteria as well as acid fast bacteria and to describe their main characteristics. 2- Know the most dangerous & prevalent corresponding diseases and how to treat or prevent these diseases. 22 July 2024 www.su.edu.eg 4  Pharm PharmDDProgram Program (2023/2024) (2023/2024) Lecture’s Contents Gram Negative Bacilli (continue) 6) Vibrio cholerae 7) Helicobacter pylori 8) Pseudomonas 9) Haemophilus influenza 10) Bordetella pertussis 11) Yersinia pestis Acid Fast Bacteria Mycobacterium tuberculosis 22 July 2024 www.su.edu.eg 5  6) Vibrio cholerae Cholera ‫الكوليرا‬ Vibrio cholerae is a comma-shaped G-ve rod, motile with single polar flagellum. Cholera is the prototype of a diarrhoeal disease. Epidemiology: Transmitted by contaminated water. Grows best in alkaline pH (pH 8-8.6).  Pathogenesis A- Virulence factors Exotoxin (Cholera toxin): Causes the secretion of chloride & secondary loss of sodium and water. B- Infection The M.O. adheres to the intestinal mucosa without invading it or invading the blood.  Characteristic symptoms - Profound watery diarrhea, with rapid depletion of water and electrolytes leading to rice like water diarrhea. - Loss of up to 20 liters of stool per day, a total of 100 liters during the 4-7 days course of the illness. - If water and electrolyte replacement is inadequate, circulatory collapse, shock, altered consciousness & renal failure occur leading to death. Laboratory diagnosis Specimen: Rectal swab or the watery stool. Microscopical characters: (Tutorial 5). Culture characteristics: (Tutorial 5).  Treatment Depends mainly on rapid rehydration for replacement of the lost water and electrolytes. Oral administration of doxycycline or ciprofloxacin significantly shortens the duration of diarrhea.  7) Helicobacter pylori ‫االنتفاخ و قرحة االثنى عشر‬ H. pylori is a highly fastidious bacterium that is very hard to grow on culture media. Pathogenesis Etiological agent of gastritis, dyspepsia, peptic ulcer & duodenal ulcer. The bacteria colonize the mucous layer overlying the gastric epithelium.  H. pylori has high urease activity that catalyzes urea hydrolysis to carbon dioxide & ammonia allowing it to survive in the stomach ?? This may depend upon local neutralization of the lethal effect of gastric acid by ammonia. H. pylori invades the mucosal layer (inner lining) of stomach so that they can be protected from immune system. The m.o. then causes inflammation, mucosal degradation, & cell death leading to ulceration & perforation of mucosal layer due to production of cytotoxins. This effect is enhanced by gastric acidity. It is a risk factor for gastric carcinoma. Spirillum  Characteristic symptoms: Recurrent pain in the upper abdomen, frequently accompanied by bleeding into GIT with no bacteremia or disseminated infection. Laboratory diagnosis Specimen: Isolation of the organism from gastric mucosa biopsy specimens. Microscopical characters: Gram-negative curved (comma-shaped) or spiral rod. Treatment Triple therapy including amoxicillin, clarithromycin or metronidazole + antiacid: proton pump inhibitor ( omeprazole) + antihistaminic (ranitidine) orally for 4 -8 weeks.  Pseudomonas Pseudomonas aeruginosa is the most human opportunistic pathogen in this group. Most strains produce diffusible pigments consisting of pyocyanin (blue green) & fluorescein (green fluorescence) when observed under UV light. Pathogenesis A- Virulence factors 1- Slime layer (Biofilm): Antiphagocytic. 2- Pili: Mediate adherence to respiratory epithelia. 3- Exotoxin A: Inhibits protein synthesis. 4- Phospholipase C & Protease: Breaks down lipids, lecithin & proteins facilitating tissue destruction. 5- Elastase: Destroys elastic fibers & blood vessel walls. Pseudomonas aeruginosa Scanning electron micrograph B- Infections May be associated with a variety of infections including: Urinary tract infection due to prolonged catheterization. Wound & burn infection with blue green pus. Pulmonary infection. Ear infection (external ear or otitis media). Eye infection (keratitis that may lead to blindness). Bacteremia & endocarditis. Keratitis Laboratory diagnosis Specimen: Urine, pus, sputum, blood, ……etc. Microscopical characters: (Practical). Culture characteristics: (Practical). Biochemical reactions: (Practical). Treatment Highly resistant to antibiotics and antiseptics. However, imipenem, carbenicillin, gentamycin & polymyxin could be used for treatment.  Haemophilus influenzae Haemophilus is a Gram-negative small coccobacilli, capsulated fastidious m.o. Epidemiology Pathogenesis Capsule is the main virulence factor. Encapsulated strains especially type B cause epiglotitis, pediatric meningitis, otitis media, & pneumonia. Epiglottitis  Acute epiglottitis is a dangerous illness, which may cause death by asphyxia specially in children 2-4 years old. H. egypticus Cause acute conjunctivitis (red eye). Laboratory diagnosis Specimen: Swab, sputum or CSF. Microscopical characters: Gram-negative small coccobacilli, capsulated.  Culture characteristics: H. influenzae and H. egypticus require blood agar or chocolate agar as they require X factor (hematin) & V factor (NAD) that are found in blood. Capsule swelling test Prevention & Control: H. influenzae type b capsular vaccine could be given at the age between 3 and 12 months. Rifampin is given to individuals in contact with patients. Treatment Ampicillin or rifampin. Endotracheal intubation in case of epiglottitis.  Bordetella pertussis Whooping cough ‫السعال الديكى‬ Epidemiology Childhood disease. Transmitted by droplets. The M.O. attaches to respiratory tract epithelial cells. Characteristic symptoms: Paroxysmal stage: The main stage among 3 stages; characterized by whooping cough paroxysms (series of repetitive coughs followed by an inspiratory whoop). This is accompanied by exhaustion & vomiting. Prevention & Control: Killed vaccine usually in combination with diphtheria and tetanus vaccine (DPT).  Yersinia pestis Plague (black death) ‫الطاعون‬ A very old zoonotic infection (Rodents are the natural reservoir). The M.O. is transmitted to man by the rat-flea. The disease occurs in epidemics or even pandemics. Fatal disease where Y. pestis passes from the flea bite to the local and central lymphatics and then blood (bacteraemia). Pneumonic plague: The most fatal form of plague. Transmitted by infected droplets. May be used as biological weapon. Characterized by cough, dyspnea, bloody sputum & respiratory failure leading to death. Acid Fast Bacteria Mycobacteria Characteristics of Mycobacteria 1- Mycobacteria are classified as acid-fast bacteria due to the high lipid content (~60%). 2- All Mycobacterium species share a characteristic cell wall, thicker than in many other bacteria, which is hydrophobic, waxy, and rich in mycolic acids. Species of medical importance: 1- M. tuberculosis complex which causes tuberculosis: M. tuberculosis, M. bovis & other mycobacteria. 2. M. leprae which causes leprosy.  Mycobacterium tuberculosis Epidemiology A fatal infection caused mainly by M. tuberculosis & rarely other mycobacteria species such as M. bovis, which infects a large number of animal species. About 90% of those infected with M. tuberculosis have asymptomatic latent TB infection, with only a 10% lifetime chance that a latent infection will progress to TB disease.  Most cases of tuberculosis are associated with reactivation due to elderly & malnutrition. Transmitted by aerosols (droplets) created by coughing or sneezing. Pathogenesis The organism is invasive, and the chronic symptoms of the disease are due to delayed hypersensitivity or host tissue reaction response that results in tissue damage. A- Virulence factors 1- Lipid fraction: Long-chain fatty acids called mycolic acids, which contribute to the organism's acid fastness, slow growing & resistance to phagocytosis, antibiotics, acids and alkali. 2- Lipoid fraction or cord factor: A trehalose dimycolate found only in virulent strains, which grows in a characteristic (serpentine) cord-like pattern. It protects T.B. from killing by macrophages. B- Infections Tuberculosis most commonly attacks the lungs (pulmonary TB). TB infection begins when the mycobacteria reach the pulmonary alveoli, where they invade and replicate within a phagosome in alveolar macrophages. Bacteria produce a protein that prevents the fusion of phagosome with lysosome, allowing the organism to escape the degradative enzymes in the lysosome. This primary site of infection (exudative lesion) in the lungs is called the Ghon focus. Bacterium resisting phagocytosis by blocking the fusion of a lysosome and a phagosome  T.B. then spreads through the bloodstream to more distant organs where secondary TB lesions can develop in peripheral lymph nodes, kidneys, brain, & bones, ….. and set up many foci of infection all appearing as tiny white tubercles in the tissues, called milliary tuberculosis. Cell mediated immunity helps to limit the primary infection by the formation of granulomatous lesions (a tubercle is a granuloma surrounded by fibrous tissu that has undergone central necrosis). Bacteria are not always eliminated within the granulomas, but can become dormant, resulting in a latent infection. Ghon focus Ghon focus Milliary Tuberculosis - Lung  Characteristic symptoms Unexplained weight loss, loss of appetite, night sweats, fever and fatigue. If TB disease is in the lungs (pulmonary): Persistent cough, hemoptysis (coughing up blood) and chest pain. Prevention & Control: - BCG (Bacille Calmette Guerin) vaccine. - Given to children in the first month and to adult exposed to infection after negative tuberculin test. BCG consists of a live attenuated strain derived from Mycobacterium bovis.  Treatment For active tuberculosis: Isoniazid, rifampicin, & pyrazinamide for two months, followed by isoniazid and rifampicin for four months. For latent tuberculosis: administration of isoniazid for 6 months reduces the risk of reactivation of tuberculosis in immunocompromized people. The period of treatment is long, since mycobacteria only divide slowly and are often not metabolically active. The necessity to use combined therapy is to prevent the emergence of resistance.  Pharm PharmDDProgram Program (2023/2024) (2023/2024) Lecture’s References Review of Medical Microbiology and Immunology. By Warren Levinson - 10th Edition (2008). Publisher: McGraw Hill - Lange. 22 July 2024 www.su.edu.eg 51