Chapter 18 – Nonfermenting G- Rods & Miscellaneous G- Rods MLAB 2434 – Clinical Microbiology Cecile Sanders & Keri Brophy-Martinez

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” or “nonoxidizers”

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

Nonfermenter Clinical Infections Nonfermenters make up 15% of all isolates of g- rods Some common disease manifestations and risk factors for nonfermenters Disease manifestations Septicemia Meningitis Osteomyelitis Wound infections following surgery or trauma

Nonfermenter Clinical Infections (cont’d) Risk factors for nonfermenter infection Immunosuppression Foreign body implantation Traumatic break in a host barrier

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

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

Nonfermenter Organization Nonfermenters are grouped according to three characteristics Growth on MacConkey Oxidase reaction OF test

Commonly Encountered Nonfermentative Organisms Pseudomonas characteristics 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

Commonly Encountered Nonfermentative Organisms (cont’d) Pseudomonas aeruginosa Most common nonfermenter isolated from clinical specimens Not common as normal flora Types of infections Bacteremia with ecthyma gangrenosum of skin Wound infections Pulmonary disease (esp. in Cystic Fibrosis)

Commonly Encountered Nonfermentative Organisms (cont’d) Types of Infections for P. aeruginosa (cont’d) Nosocomial UTI Endocarditis Meningitis Otitis externa (“swimmer’s ear”) “Hot tub” syndrome Virulence factors for P. aeruginosa Endotoxins, hemolysins, proteases, slime, etc.

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

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

Commonly Encountered Nonfermentative Organisms (cont’d) Pseudomonas fluorescens & Pseudomonas putida Produces pyverdin but not pyocyanin Rarely causes clinical disease Stenotrophomonas maltophilia Third most common nonfermenter cultured Common in the hospital environment

Other Nonfermenters Acinetobacter – found in hospital environments; can cause opportunistic infection Pseudomonas stutzeri – wrinkled, leathery colonies that may be light yellow or brown Burkholderia cepacia – most often associated with pneumonia in Cystic Fibrosis Burkholderia pseudomallei – causes melioidosis Alcalingenes – found in water and resistant to disinfectants