2. AEROBIC GRAM-NEGATIVE BACTERIA: Miscellaneous Gram-Negative Bacilli

• Carried by wild animals including: Deer, Rabbits, Beavers, Squirrels

• Humans may acquire the infection by:

a. Skinning animals

b. Eating undercooked meat

c. From animal bites

d. From the bite of deerflies or ticks

• _____: causes “Tularemia”

• Biosafety LEVEL 3

• Intracellular bacteria that resist phagocystosis

Francisella

• F.tularensis

• Faintly staining coccobacilli

• Colony morphology: Small and Grayish

• The medium of choice is Glucose-Cystine Blood Agar

• Agglutination and Direct Fluorescent Antibody Test, are used to confirm the identification

Francisella

• Normal GI biota of animals

• Isolated from blood and bone marrow

• Causes undulant fever

• Acquired by humans: drinking contaminated milk, aerosols from slaughterhouse exposure, and has an incubation period of: 1-3 weeks

• Biosafety LEVEL 3

Brucella

• Oxidase, Catalase = POSITIVE 

• Will grow on: Buffered Charcoal Yeast Extract (BCYE) and Modified Thayer-Martin Agars

• Require 10% CO2 in humidified air and 3-4 weeks for growth

• _____ - causes the most severe infection

• Presumptive diagnosis: Slide Agglutination in Antisera

• Primary mrthod of diagnosing: Serological tetsing of patient sera 

Brucella

• B.melitenis

Inhabits the mucous membrane of the respiratory tract of humans

Nasopharyngeal swabs are recommended for the diagnosis

Bordetella

• Catarrhal, Paroxysmal, and Convalescent are the three stages of caused disease 

• Colonies small,smooth and they resembles mercury droplets and are BETA- HEMOLYTIC

• Urease NEGATIVE and does not grow on MAC Agar 

• Grows on: Bordet-Gengou (potato infusion), Regan-Lowe agars (Charcoal- horse blood agar)

• Media are often selective by adding Cephalexin

• PCR is used for the diagnosis and specimen can be transmitted without transport medium

Bordetella pertussis

• Found mostly as the Oral biota of animals

• Infections are caused by Animal bites, which can result in cellulitis

• Produces colonies that show “Starlike” centers

• Grows well in SBA, Choc Agar, DOES NOT GROW ON MAC 

Actinobacillus

• Normal respiratory/GI biota of animals

• Acquired by humans from: Animal bites (cats and dogs)

• Inhalation of dried animal feces

• Caused cellulitis which can progress into ostomyelitis, meningitis, joint infections and pneumonia

• _____ causes most human infection 

Pasteurella

P. multocida

• Plemorphic

• Coccobacilli that may show bipolar staining

• Oxidase, Catalase, Indole, Nitrate = POSITIVE 

• Motility = NEGATIVE 

• Penicillin = VERY SUSCPETIBLE 

• Grows well on NON-SELECTIVE Agars but not MAC

Pasteurella

• Normal biota of the Mouth and the Upper respiratory tract

• Causes Abscesses of the oral cavity and human bite wound infection

• A member of HACEK group and has been associated with endocarditis

Eikenella corodens

• Approx 50% of the strains corrode or pit the agar surface

• Requires hemin (X factor ) for growth unless 5-10% CO2 is present

• Produces a “Bleachlike” odor

Eikenella corodens

• Aquatic organisms that may be found in various water systems 

• Resistant to commonly used concentrations of chlorine

• Most human infection are caused by _____

• Causes Legionellosis, Pontiac fever

• On Gram stain, appear as thin, poorly staining bacilli it is better to use 0.1% basic fuchsin asn the counter stain instead of safranin

Legionella

• L.pneumophila serogroup 1

• Most biochemical test are NEGATIVE

• Requires L-cysteine for growth

• Grow on BCYE agar but not on SBA

• Urine Antigen Test is the most common lab assay used for the diagnosis

Legionella

• _____ is found in water and soil

• Causes wound infection acquired from contaminated soil water

• In Nutrient Agar: produces purple/violet pigment

Chromobacterium

• C.violaceum

• In low numbers it is considered as a normal vaginal biota 

• Presence of clue cells, epithelial cells with numerous bacteria attached

• Uses Amsel and Nugent to diagnose 

Gardnerella vaginalis

• Gram-negative, curved bacilli

Bartonella

• Agent of trench fever

• Also causes growth of neoplastic blood vessels in various parts of the body (bacillary angiomatosis) and other infections such as endocarditis

• Spread by human lice

Bartonella quintana

Causes cat-scratch disease and also bacillary peliosis hepatitis and bacillary angiomatosis

B. henselae

• Normal biota in humans in: Upper respiratory tract, Possibly Gastrointesti nal, Genital tract

• It is a member of the HACEK group and is mainly associated with endocarditis

• In Gram stains: appears as short chains, pairs, or rosettes of irregularly staining bacilli with bulbousn ends

Cardiobacterium hominis

• Requires CO2 for initial isolation

• Can be recovered on SBA, although growth is enhanced in media containing yeast extract

Cardiobacterium hominis

• Normal oral biota in rats and other rodents

• Best isolated from blood, synovial fluid and abscess material

• Cases Rat-bite fever and Haverhill fever

Streptobacillus moniliformis

• Facultative, gram-negative pleomorphic bacillus

• It grows on media enriched with SBA (15% is optimal) incubated in a CO2 incubator.

Streptobacillus moniliformis