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Clinical Microbiology

Clinical Microbiology. (MLCM- 201) Prof. Dr. Ebtisam. F. El Ghazzawi . Medical Research Institute (MRI) Alexandria University. Intended Learning Outcomes. By the end of this lecture the student should be able to

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Clinical Microbiology

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  1. Clinical Microbiology (MLCM- 201) Prof. Dr. Ebtisam. F. El Ghazzawi. Medical Research Institute (MRI) Alexandria University

  2. Intended Learning Outcomes By the end of this lecture the student should be able to Understand all about Pathogens outside the enteric tract, Types, pathogens, and there Laboratory Diagnostic tests.

  3. Pathogens outside the Enteric Tract F10

  4. I. Klebsiella – Enterobacter – Serratia group: These organisms are usually opportunistic pathogens that cause nosocomial infections, especially pneumonia and urinary that infections. Klebsiella pneumonia is an important respiratory tract pathogen outside hospital as well. Klebsiella species exhibit mucoid growth, large polysaccharide capsules and lack of motility.

  5. Although Klebsiella is a primary pathogen, patients with Klebseillapneumonia infections frequently have predisposing conditions such as advanced age, chronic respiratory disease, diabetes or alcoholism. The organism is carried in the respiratory tract of about 10% of healthy people, who are prone to pneumonia if host defences are lowered.

  6. Enterobacter and serratia infections are clearly related to hospitalization, especially to invasive procedures such as intravenous catheterization, respiratory intubation and urinary that manipulations. Laboratory diagnosis: Culture on Mac-Conkey’s agar  red colonies lactose-fermenting.

  7. II. Proteus – Providencia – Morganella group: These organisms primarily cause urinary tract infections both community and hospital acquired. Proteus species move very actively by means of peritrichous flagella resulting in swarming on solid media unless the swarming is inhibited by chemicals. Proteus species Swarming motility on blood agar

  8. Laboratory diagnosis: Culture on blood agar will produce swarming. Culture on Mac Conkey’s agar  colourless non-lactose fermenting colonies.

  9. III. Pseudomonas aeruginosa: It is motile, rod shaped, gram-negative bacteria. It is widely distributed in nature and is commonly present in moist environment in hospitals. It can colonize normal humans, in whom it is a saprophyte. It causes disease in humans with abnormal host defenses; patients with extensive burns and in those with chronic respiratory disease.

  10. Ps. aeruginosa causes infections e.g. sepsis, pneumonia, and urinary tract infections. Severe external otitis and other skin lesions occur in users of swimming pools and hot tubs in which the chlorination is inadequate. The organisms are strict aerobic and are oxidase positive. They have a remarkable ability to withstand disinfectants; this accounts in part for their role in hospital-acquired infections.

  11. Ps. aesuginasa produces two pigmens useful in clinical and laboratory diagnosis: • Pyocyanin which can colour the pus in a wound blue. • Pyoverdin (fluorescein), a yellow green pigment that fluoresces under ultraviolet light, a property that can be used in the early detection of skin infection in burn patients. In the laboratory, these pigments, diffuse into the agar giving a blue green colour that is useful in identification.

  12. Pseudomonas aeruginosa Blue green pigment (pyocyanin) produced and diffuses into the agar

  13. Laboratory diagnosis: • Specimen from skin lesions, pus, urine, blood, spinal fluid, sputum and other material should be obtained as indicated by the type of infection. • Gram stain shows Gram-negative nods, that are oxidase positive. • Culture on Mac-conkey’s or EMB agar  show colourless non-lactose-fermenting colonies. On nutrient media or blood agar a blue green colour pigment with fruity aroma is produced.

  14. IV. Bacteroides: Bacteroides are the most common cause of serious anaerobic infections, e.g. sepsis peritonitis and abscesses. Bacteroides are Gram-negative bacilli and may appear as slender rods or coccobacilli. They are normal inhabitants of the bowel. Normal stools contain 1011Bacteroides per gram.

  15. Laboratory diagnosis: By culturing anaerobically on blood agar plates containing kanamycin or vancomycin to inhibit unwanted organisms, where characteristic coloured colonies are grown.

  16. Assignment Klebsiella.

  17. Study Questions State the Laboratory Diagnosis for all kinds of pathogens outside the enteric tract.

  18. Recommended Textbooks Manual of Clinical Microbiology, Vols. 1 and 2: Eighth Edition Patrick R. Murray

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