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Chapter 22 Nonfermenting G- Rods Miscellaneous G- Rods

General Characteristics of Nonfermenters. Nonfermentative organisms that break down carbohydrates oxidatively (aerobically) are also called

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Chapter 22 Nonfermenting G- Rods Miscellaneous G- Rods

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    1. Chapter 22 – Nonfermenting G- Rods & Miscellaneous G- Rods MLAB 2434 – Clinical Microbiology Keri Brophy-Martinez

    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. Nonfermenter Clinical Infections Nonfermenters make up 15% of all isolates of g- rods Achromobacter Acidovorax Acinetobacter Agrobacterium Alcaligenes Burkholderia Stenotrophomonas Chryseobacterium Chryseomonas Comamonas Flavimonas Flavobacterium Methylobacterium Moraxella Weeksekka Ochrobactrum Oligella Pseudomonas Psychrobacter Roseomonas Shewanella Sphingobacterium

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

    6. Nonfermenter Clinical Infections (cont’d) Risk factors for nonfermenter infection Immunosuppression Foreign body implantation Traumatic break in a host barrier Antibiotic therapy Underlying disease

    7. Nonfermenter Clinical Infections (cont’d) Pseudomonas infection of skin and nail

    8. Biochemical Characteristics of Nonfermenters Nonfermenters vary in biochemical and morphologic characteristics All are nonreactors on TSI slants Oxidative vs. fermentative properties can be demonstrated with use of OF (oxidative/fermentative) medium

    9. Initial Clues to Nonfermenters Long, thin g- rods or cb Oxidase positive (not ALL nonfermenters) 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)

    10. 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

    11. Commonly Encountered Nonfermentative Organisms Pseudomonas characteristics Associated with water and moist environments Strict aerobe G- rods or cb Usually motile with polar or polar tufts of flagella Oxidase and catalase positive Usually grows on MacConkey agar Usually oxidizes carbohydrates

    12. Commonly Encountered Nonfermentative Organisms (cont’d) Pseudomonas aeruginosa Most common nonfermenter isolated from clinical specimens Not common as normal flora

    13. Pseudomonas aeruginosa 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

    14. Commonly Encountered Nonfermentative Organisms (cont’d) Virulence factors for P. aeruginosa Endotoxins, hemolysins, proteases, slime, pili etc

    15. Commonly Encountered Nonfermentative Organisms (cont’d) P. aeruginosa identifying characteristics Beta-hemolytic on blood agar Green metallic sheen due to production of pigment pyocanin (bluish-green) Most strains also produce pigment pyoverdin (yellowish-green fluorescence) Odor described as “grape-like” or “Frito-like”

    16. Commonly Encountered Nonfermentative Organisms (cont’d) P. aeruginosa P. aeruginosa on MacConkey producing pyoverdin

    17. Commonly Encountered Nonfermentative Organisms (cont’d) Pseudomonas fluorescens & Pseudomonas putida Produces pyverdin but not pyocyanin Rarely causes clinical disease Found in water and soil, usually environmental contaminants

    18. Commonly Encountered Nonfermentative Organisms (cont’d) Stenotrophomonas maltophilia Third most common nonfermenter cultured, ubiquitous in nature Common in the hospital environment Implicated in infections of wounds, RT, UT and blood

    19. 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 Pseudomonas stutzeri – wrinkled, leathery colonies that may be light yellow or brown, non- fluorescent Burkholderia cepacia – most often associated with pneumonia in Cystic Fibrosis Burkholderia pseudomallei – causes melioidosis Alcalingenes – found in water and resistant to disinfectants

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