Bacterial species of limited pathogenic significance

● Mostly Gram-negative rods

● Includes environmental organisms and opportunistic pathogens

● Often isolated from clinical specimens even when pathogenicity is uncertain

Bacterial species of limited pathogenic significance

○ Gram-negative coccobacilli

○ Easily grown on standard culture media

○ Environmental organisms

○ Opportunistic infections in humans and animals, especially hospital-associated

Acinetobacter Species

Important Species of Acinetobacter

○ Acinetobacter baumannii

○ Acinetobacter calcoaceticus

○ Acinetobacter lwoffii

■ Normally low expression

■ Overexpression occurs due to promoter insertion sequence near AmpC gene

Chromosomal cephalosporinases (AmpC enzymes)

Carbapenem resistance due to __________ is emerging globally

metallo-beta-lactamases

● is a genus formerly classified under Rickettsiales

● Contains 19 recognized species

● Thin, Gram-negative slightly curved rods

● Grow only on blood enriched media

● Slow growth requiring up to 4 weeks for colony development

Bartonella Species

■ Carried by healthy cats

■ Transmitted cat to cat by cat flea Ctenocephalides felis

■ Kittens may remain bacteraemic for weeks to months

Bartonella henselae

■ Usually occurs via cat scratch

■ Less commonly via cat bite

■ Possible entry via flea feces contaminating claws

Human transmission

it is caused by Bartonella henselae

Bacillary angiomatosis

● These are Gram-negative bacteria with shared ecological and biological characteristics

○ Found in aquatic environments

○ Opportunistic pathogens of fish, reptiles, and occasionally mammals and birds

○ Most are catalase positive, oxidase positive, facultative anaerobes

○ Motile via polar flagella

○ Oxidase positive

○ Some grow optimally below 37 degrees Celsius

Aeromonas, Plesiomonas shigelloides, and Vibrio species

are straight medium-sized rods

found in fresh water and on fish and reptile surfaces

Aeromonas and Plesiomonas

are curved rods and halophilic

found in brackish and salt water

Vibrio species

Important species involved in disease

■ Aeromonas hydrophila

■ Plesiomonas shigelloides

■ Vibrio metschnikovii

as a major human pathogen

Vibrio cholerae

Virulence factors of Aeromonas hydrophila

■ Adhesins

■ Exoenzymes

■ Hemolysin

■ Enterotoxins

causes diarrhea in humans via enterotoxins

Plesiomonas shigelloides

1. causes severe enteric infection

2. causes enteric disease in chickens

3. cause fish disease

4. Food poisoning from _________ associated with raw seafood

1. Vibrio cholerae

2. Vibrio metschnikovii

3. Vibrio species and Listonella anguillarum

4. Vibrio parahaemolyticus

Treatment:

For Aeromonas and Plesiomonas:

For Vibrio infections:

Cephalosporin

Gentamicin and nalidixic acid

is a motile Gram-negative rod

Produces violet pigment on culture media

Found in soil and water in tropical and subtropical regions

Causes septicaemic infections in humans, pigs, and dogs

Associated with pleuropneumonia in Barbary sheep and pigs

Chromobacterium violaceum

● This organism is associated with respiratory disease in poultry

○ Pleomorphic Gram-negative rod

○ Produces small grey non-hemolytic colonies on blood agar

○ Growth enhanced in 5 to 10% carbon dioxide

○ Oxidase positive

○ Catalase negative

Treatment: Amoxicillin

Ornithobacterium rhinotracheale

● Previously called Pasteurella anatipestifer

○ Non-motile Gram-negative rod

○ Requires enriched media with 5 to 10% carbon dioxide

○ Causes septicaemia in ducklings and other waterfowl

Treatment: Ampicillin, Amoxicillin, or tetracyclines

Vaccines: bacterin and live avirulent forms

Riemerella anatipestifer

Highly pleomorphic Gram-negative rod

Normal inhabitant of rodent upper respiratory tract

Streptobacillus moniliformis

Streptobacillus moniliformis in Animals cause

Causes bronchopneumonia in laboratory rats and mice

Causes cervical lymphadenitis in guinea pigs

Associated with synovitis and mortality in turkeys due to rat bites

Streptobacillus moniliformis in Human causes

Haverhill fever and rat-bite fever