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Nosocomial infections

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Nosocomial infections

  1. 1. NOSOCOMIAL INFECTIONS ETIOLOGY & DIAGNOSIS
  2. 2. ETIOLOGY The causative agents of nosocomial infections incude • Bacteria • Viruses • Fungi
  3. 3. BACTERIA • Gram-negative bacteria (Pseudomonas aeruginosa, Aeromonas hydrophilia, Burkholderia cepacia, Stenotrophomonas maltophilia, Serratia marcescens, Flavobacterium meningosepticum, Acinetobacter calcoaceticus, and Legionella pneumophila) • Mycobacteria (Mycobacterium xenopi, Mycobacterium chelonae, or Mycobacterium avium-intracellularae)
  4. 4. • Gram positive cocci • Salmonella species • Staphylococcus aureus • Clostridium perfringens • Clostridium botulinum • Bacilluscereus • Escherichia coli • Campylobacter jejuni
  5. 5. • Yersinia enterocolitica • Vibrio parahaemolyticus • Vibrio cholerae • Aeromonas hydrophilia • Streptococcus species • Listeria monocytogenes
  6. 6. VIRUSES • Varicella zoster (chickenpox) • Influenza • Molluscum contagiosum • Human papillomavirus • Noroviruses • RotavirusCaliciviruses
  7. 7. FUNGI • Aspergillus • Exophiala jeanselmei
  8. 8. DIAGNOSIS
  9. 9. • UTI • Bacteremia • Pneumonia • Surgical wounds
  10. 10. BACTEREMIA SPECIMEN COLLECTION • Venipuncture • The skin is cleaned with 80% to 90% ethanol followed by an iodine based compound scrubbed in a concentric fashion qround the venipuncture site
  11. 11. BLOOD CULTURE METHODS • Aerobic culture bottle • It contains a soybean casein digest broth, trypticase soy broth,brain heart infusion ,brucella agar, or columbia broth base • Anaerobic broth media contain same contents but 0.5% cysteine may be added
  12. 12. ANTICOAGULANTS AND OTHER ADDITIVES: • Sodium polyanetholsulfonaye • Sodium amylosulfate • Sodium citrate • EDTA
  13. 13. NEWER BLOOD CULTURE SYSTEMS BIPHASIC BROTH-SLIDE SYSTEM: consists of a slide paddle containing chocolate, macconkey, and malt extract agars in a standard broth bottle. Bacterial growth appears as small discrete colonies or confluent growth on he paddle
  14. 14. CONTINUOS MONITORING BLOOD CULTURE SYSTEMS: • BACTEC system involves measuring the amount of 14CO2 released from the bacterial colonies and calculating the growth index
  15. 15. PNEUMONIA SPECIMEN COLLECTION: • Patients should be instructed to rinse out their mouth and collect a deep sputum specimen • The purpose is to collect lung secretions and not saliva or drainage from nasopharynx • Bronchoscope may also be used
  16. 16. DIRECT MICROSCOPIC EXAMINATION: • Direct gram stained smear • Samples with greater than 25 neutrophils and fewer than 10 epithelial cells are positive • The morphology of the organisms present also helps CULTURE: • Sheeps blood agar, macconkey, and chocolate agar plates are used for culture
  17. 17. CHRONIC PNEUMONIA DIRECT MICROSCOPY: • Acid fast stains such as Kinyoun, Ziehl Neelson are used for mycobacterium • Potassium hydroxide and coflour white are commonly used to detect yeast cells and hyphal elements • Culture and rapid diagnostic tests such as Nucleic amplification test are also used
  18. 18. SURGICAL INFECTIONS • Specimen is collected by wound swabs , drainage collection and tissue sample • Culture methods are used for culturing the tissue sample • Examination is done by histopathologic or radiographic examination
  19. 19. UTI SPECIMEN COLLECTION: Cntamination by vaginal, anal and urethral flora should be prevented MIDSTREAM SPECIMEN COLLECTION: • The first portion of the voided urine is discarded and the midstream urine is collected • This is done to prevent the contamination by normal flora
  20. 20. CATHETERISED SPECIMEN COLLECTION: • Invasive technique reduces the risk of contamination by normal flora • Unclean catheter may lead to infection and contamination SUPRAPUBIC ASPIRATION: • With the bladder full, the urine is collected with a needle and syringe followed by skin antisepsis • Done usually in infants
  21. 21. SCREENS PRINCIPLE THRESHOLD OF DETECTION Manual Microscopy Direct,uncentrifuge d or centrifuged Recognition of organism morphotypes and gram stain >1 organism per OIF = >105 Chemical Enzymatic dipstick Nitrate reductase WBC esterase Chemstrip LN Enzyme tube Uriscreen Calorimetric particle filtration Gram –ve bacteria reduce nitrates Presence of WBC enzymes Measures catalase Membrane filtration and detection >105 5 WBC per field >10 to 10 >104 to 105 >104
  22. 22. AUTOMATED PRINCIPLE THRESHOLD Bioluminescence UTI screen Detected bacterial ATP >104 to 105 Photometry If a significant amount are present in the specimen, they will grow in the medium > 104 to 105 Calorimetric particle filtration Membrane filtration and detection by safranin O dye > 104 to 105

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