Gram-negative Rods: Glucose nonfermenting

Microbiology

Gram-negative Rods:Glucose nonfermenting

Karen Honeycutt, M.Ed., MT(ASCP)SM

MT 418 Clinical Microbiology

Student Laboratory Session

Microbiology

General Information• Predominantly opportunistic

• Debilitated host

• Nomenclature changes rapidly (usually known by 2 names for 5-10 years)

• Will grow on BAP, 22-35°C, 24-72 hours

• Categories based upon: glucose, oxidase & ability to grow on MAC

GNR: Glucose nonfermenters

Microbiology

General Information• Gram stain morphology taken from non-

inhibitory agar

• Can be difficult to treat, can rapidly develop antibiotic resistance to drugs used for treatment

• Many genera

• Commercial system reliability?

GNR: Glucose nonfermenters

Microbiology

Glucose “O”, oxidase +, MAC +• Pseudomonas sp.

– Pseudomonas aeruginosa most commonly isolated nonfermenting GNR

• Grows in moist environments (soap)

• Aerobic • Motile w/polar flagella

GNR: Glucose nonfermenters

Microbiology

Pseudomonas aeruginosa• Nosocomial infections• Usually not part of normal flora• Colonization can occur (upper respiratory

tract, skin, GI tract)

GNR: Glucose “O”, Oxidase +, MAC +

Microbiology

P. aeruginosa - Pigments

• Usually produces– Pyoverdin (fluorescein) – yellow/green;

visualize with UV light; Other Pseudomonas sp. can also produce

– Pyocyanin – blue-green pigment; only produced by P. aeruginosa

• May produce– Pyorubrin – pink to red/maroon

pigment; only produced by P. aeruginosa

GNR: Glucose “O”, Oxidase +, MAC +

Microbiology

Pseudomonas aeruginosa Id

Glucose OF = “O”

OxidaseBAP

MAC

GNR: Glucose “O”, Oxidase +, MAC +

Microbiology

Pseudomonas aeruginosa Id

Moeller base decarboxylase/dehydrogenaseArginine +Ornithine (-)Lysine (-)

Glucose “O”Green pigment

GNR: Glucose “O”, Oxidase +, MAC +

Microbiology

Pseudomonas aeruginosa Rapid Id

OxidaseBAP

Rough & beta-hemolytic on BAPPigmentGrape-like smell

GNR: Glucose “O”, Oxidase +, MAC +

Microbiology

Pseudomonas aeruginosa infections• Cystic fibrosis patients – serious lung

infections• Immunosuppressed • Burn wounds• Osteomyelitis• UTI, septicemia, • Corneal ulcers (blindness)• Swimmer’s ear, folliculitis

GNR: Glucose “O”, Oxidase +, MAC +

Microbiology

Pseudomonas aeruginosa infections

• Corneal ulcers (blindness)

GNR: Glucose “O”, Oxidase +, MAC +

Photo from Images.MD

Microbiology

Pseudomonas aeruginosa infections

• Burn wound

GNR: Glucose “O”, Oxidase +, MAC +

Photo from Images.MD

Microbiology

Burkholderia cepacia

• Nosocomial infections

• CF patient – colonized/infected with: severe social ramifications; person to person spread established

• Some CF – once infected with: fulminant decline of pulmonary function

• Resistant to many antibiotics

GNR: Glucose “O”, Oxidase +/-, MAC +

Microbiology

Glucose “O” or “I”, oxidase (-), MAC +

• Stenotrophomonas maltophilia – Strong maltose oxidizer

• Nosocomial

• Opportunistic

• 3rd most common glucose non-fermenter isolated in clinical lab

GNR: Glucose nonfermenters

Microbiology

Stenotrophomonas maltophilia

• BAP: may produce a pale yellow to lavender pigment

• Oxidase negative• Arginine (-), Ornithine (-), Lysine (+)• DNase (+)• Polymyxin B = “S”• Disk diffusion susceptibilities now

standardized (SXT “S” – drug of choice)

GNR: Glucose “O” or “I”, oxidase (-), MAC +

Microbiology

Glucose “O” or “I”, oxidase (-), MAC +

• Acinetobacter sp.

• 2nd most common glucose non-fermenter isolated in clinical lab

• Nosocomial

• Opportunistic

• Normal flora: skin, vaginal tract

GNR: Glucose “O” or “I”, oxidase (-), MAC +

Microbiology

Acinetobacter sp.

• Gram stain morphology: plump gnr in pairs (can be mistaken for GNDC)

• Oxidase (-)

• Nitrate reduction (-)

• Glucose– “O” Acinetobacter baumannii– “I” Acinetobacter lwoffii

GNR: Glucose “O” or “I”, oxidase (-), MAC +