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Nonfermenting GN Rods & Miscellaneous GN Rods

Nonfermenting GN Rods & Miscellaneous GN Rods

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Nonfermenting GN Rods & Miscellaneous GN Rods

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  1. Nonfermenting GN Rods & Miscellaneous GN Rods MLAB 2434 – Microbiology Keri Brophy-Martinez

  2. General Characteristics of Nonfermenters • Nonfermentative organisms that break down carbohydrates oxidatively (aerobically) are also called “oxidizers” or “saccharolytic” • Organisms that are NOT able to break down carbohydrates fermentatively or oxidatively are called “biochemically inert,” “nonoxidizers”or nonsaccharolytic

  3. General Characteristics of Nonfermenters (cont’d) • Nonfermenters are ubiquitous in the environment • Predominantly opportunistic • Also isolated in hospitals from nebulizers, dialysate fluids, saline, and catheter devices • Somewhat resistant to disinfectants & antibiotics

  4. Achromobacter Acidovorax Acinetobacter Agrobacterium Alcaligenes Burkholderia Stenotrophomonas Chryseobacterium Chryseomonas Comamonas Flavimonas Flavobacterium Methylobacterium Moraxella Weeksekka Ochrobactrum Oligella Pseudomonas Psychrobacter Roseomonas Shewanella Sphingobacterium The Nonfermenters

  5. Clinical Infections • Septicemia • Meningitis • Osteomyelitis • Wound infections following surgery or trauma • Nosocomial Infections

  6. Clinical Infections • Risk factors • Immunosuppression • Foreign body implantation • Traumatic break in a host barrier • Antibiotic therapy • Underlying disease

  7. Initial Clues to Nonfermenters • Long, thin gn rods or cb • Oxidase positive (not ALL nonfermenters) • No or slow growth of MacConkey agar • Nonreactive in 24 hours on commercial kit systems • TSI nonreactive • Resistant to antibiotics ( penicillin, ampicillin & cephalosporins) • Treat with aminoglycosides, quinolones and anti-pseudomonal penicillins ( ticarcillin, piperacillin)

  8. Nonfermenter Organization • Nonfermenters are grouped according to three characteristics • Growth on MacConkey • Not all nonfermenters grow on MAC • All nonfermenters that grow on MAC are lactose negative • Oxidase reaction • OF test

  9. Commonly Encountered Nonfermentative Organisms • Pseudomonas characteristics • Associated with water and moist environments • Not common as normal flora • Strict aerobe • GN rods or cb • Usually motile with polar or polar tufts of flagella • Oxidase and catalase positive • Usually grows on MacConkey agar • Usually oxidizes carbohydrates

  10. Pseudomonas aeruginosa:Clinical Infections • Types of infections • Bacteremia with ecthyma gangrenosum of skin • Wound infections • Pulmonary disease (esp. in Cystic Fibrosis) • Nosocomial UTI • Endocarditis • Meningitis • Otitis externa (“swimmer’s ear”) • “Hot tub” syndrome (skin rash)

  11. Pseudomonas aeruginosa:Virulence Factors • Endotoxins • Hemolysins • Cytotoxins • Proteases • Slime • Pili

  12. P. aeruginosa:Laboratory identification • Beta-hemolytic on blood agar • Green metallic sheen due to production of pigment pyocyanin (bluish-green) • Most strains also produce pigment pyoverdin (yellowish-green fluorescence) • Odor described as “grape-like” or “Frito-like”

  13. Honorable mentions… • Pseudomonas fluorescens & Pseudomonas putida • Produces pyoverdin but not pyocyanin • Rarely causes clinical disease • Found in water and soil, usually environmental contaminants • Pseudomonas stutzeri • Wrinkled, leathery colonies that may be light yellow or brown, non- fluorescent

  14. Stenotrophomonas maltophilia • Third most common nonfermenter cultured, ubiquitous in nature • Common in the hospital environment • Implicated in infections of wounds, RT, UT and blood • Frequent isolate of Cystic Fibrosis patients

  15. Other Nonfermenters • Acinetobacter – found in hospital environments; can cause opportunistic infection, skin/vaginal normal flora. On BAP transluscent-opaque, MAC colorless. On gram stain, short plump gncb • Burkholderia cepacia – most often associated with pneumonia in Cystic Fibrosis • Burkholderia pseudomallei – causes melioidosis( an aggressive pulmonary disease causing pneumonia, abscesses and septicemia) • Alcalingenes – found in water and resistant to disinfectants

  16. References • Engelkirk, P. G., & Duben-Engelkirk, J. (2008). Laboratory Diagnosis of Infectious Diseases: Essentials of Diagnostic Microbiology . Baltimore, MD: Lippincott Williams & Willkins. • Kiser, K. M., Payne, W. C., & Taff, T. (2011). Clinical Laboratory Microbiology: A Practical Approach . Upper Saddle River, NJ: Pearson Education, Inc. • Mahon, C. R., Lehman, D. C., & Manuselis, G. (2011). Textbook of Diagnostic Microbiology (4th ed.). Maryland Heights, MO: Saunders. • http://www.microbelibrary.org/library/laboratory-test/2862-blood-agar-plates-and-hemolysis-non-fermenting-gram-negative-rods-including-pseudomonas-aeruginosa