Fastidious Gram Negative Rods

Fastidious GNR characteristics

don't grow on MAC, require enrichment factors, some grow slow on SBA, some only grow on CHOC

Haemophilus characteristics

"blood-loving," GN coccobacilli or rods, aerobic-facultative anaerobes, grow on CHOC, some grow on SBA, incubate at 37 celsius and 5-10% CO2

Haemophilus Biochemical tests

Oxidase +

Catalase -

Non-motile

convert nitrates to nitrites

Differentiating Haemophilus species

1. Determine X & V factor requirements (quad plate)

2. Porphyrin Test ( is X factor produced?)

3. Rapid ID Kit Tests (based on carbohydrate fermentation)

H. influenzae habitat

mucus membranes of the respiratory tract, non-encapsulated forms are NF

H. influenzae virulence

capsule, IgA protease, adherence factors

H. influenzae significance

serotype b causes meningitis in children <5 yrs, cellulitis, pharyngitis, pneumonia in children

*non-encapsulated: bronchitis, sinusitis, otitis media

H. influenzae Lab ID

GS: GN coccobacilli or filamentous rods

Oxidase +

Catalase +

Porphyrin Test: ALA -

Rapid Kit tests, Capsular swelling test

H. influenzae biotype aegyptius habitat

This organism causes purulent conjunctivitis and Brazilian Purpuric Fever

H. influenzae biotype aegyptius significance

Acute conjunctivitis - children

Brazilian Purpuric Fever - sepsis, fever

H. influenzae biotype aegyptius Lab ID

GS and culture - same as H. influenzae

Cannot utilize Xylose

H. parainfluenzae habitat

Normal flora of URT in healthy people

H. parainfluenzae significance

Most common Haemophilus species isolated

Rarely cause infection - low virulence

H. parainfluenzae Lab ID

GN coccobacillus or filamentous rods

Non-hemolytic gray/white flat colonies

*only requires V factor

*ALA +

H. ducreyi significance

Chancroid - STI

H. ducreyi Lab ID

Difficult to culture - requires very special media

Direct smear - GN coccobacilli in a line

Other Haemophilus species habitat

Normal flora of URT

Other Haemophilus species significance

Rarely cause infections

Other Haemophilus species Lab ID

based on X & V requirements

Pasturella multocida habitat

NF of respiratory and GI tract of animals

Pasturella multocida significance

transmitted through dog and cat bites, abscesses and cellulitis

Pasturella multocida Lab ID

GS: small GNR

Grows on SBA and CHOC w/ a mushroom odor

Oxidase +

Catalase +

Non-motile

Brucella species habitat

found in urine and milk of animals

Brucella significance

Zoonotic infection

Brucellosis or Undulant Fever

Brucella Lab ID

GS: GN coccobacilli

Oxidase & Catalase +

H2S & Urease +

Non-motile

Francisella tularensis habitat

Found in rabbits, deer, squirrels, etc.

Francisella tularensis significance

Level 3 biosafety hazard

Tularemia/Rabbit Fever in humans

Francisella tularensis Lab ID

GS: bipolar staining GNR

Prefers Blood Cysteine Glucose agar

Non-motile

Bordetella pertussis habitat

Found in humans

Bordetella pertussis significance

"Whooping Cough" usually in children

Bordetella pertussis virulence

Pertussis toxin, capsule, cilia

Irritates the respiratory mucus membranes

Bordetella pertussis Lab ID

Special media: Bordet-Gengou and Regan-Lowe agar with "mercury droplet" colonies

Legionella species habitat

water sources

Legionella species significance

transmitted through inhaling contaminated aerosols

Legionnaire's Disease (severe) & Pontiac Fever (mild)

Legionella pneumophilia Lab ID

GS: thin, tiny poor staining GNR

requires cysteine & iron salts for growth

BCYE agar

*Serological testing preferred

Gardnerella vaginalis habitat

Normal vaginal flora

Gardnerella vaginalis significance

Causes bacterial vaginosis

Gardnerella vaginalis Gram Stain

GS: GNR that are gram variable

Direct smear: clue cells, lack of lactobacilli

Gardnerella vaginalis Lab ID

grows poorly on routine media (HBT, or V agar)

Oxidase -

Catalase -

Hippurate +

Rapid ID-NH panel

Whiff test