Keypoints - Bacteria Flashcards
Staphylococcus
Gram-positive cocci in clusters resembling bunches of grapes
Grow on non-enriched media
Moderately-sized white or golden colonies
Colonies of S. aureus and S. intermedius produce double haemolysis
Facultative anaerobes, non-motile, catalase-positive
Commensals on mucous membranes and skin
Coagulase production correlates with pathogenicity
Comparatively stable in the environment
Cause pyogenic infections
Rhodococcus equi
Gram-positive rods or cocci Growth on non-enriched media Salmon-pink mucoid colonies with no haemolysis Aerobic, non-motile CAMP test-positive Soil saprophyte Respiratory pathogen of foals
Actinomycetes
Gram-positive bacteria, many species with branching filaments Relatively slow growth on laboratory media Opportunistic pathogens producing diverse inflammatory responses Actinomyces, Arcanobacterium and Actinobaculum species -anaerobic or facultatively anaerobic -morphologically heterogeneous -non-spore-forming, non-motile -MZN-negative --colonize mucous membranes Nocardia species -aerobic, non-motile -spores from aerial filaments -growth on Sabouraud dextrose agar -MZN-positive -soil saprophytes Dermatophilus congolensis -aerobic and capnophilic -motile zoospores -no growth on Sabouraud dextrose agar II -found in scabs and in foci on skin of carrier animals
Listeria Species
Small, Gram-positive rods
Grow on non-enriched media
Tolerates wide temperature and pH ranges
w Small haemoly tic coionies on blood agar
Facultative anaerobes, catalase-positive,
oxidase-negative
Tumbling motility at 25°C
Aesculin hydrolysed
= Environmental saprophytes
Outbreaks of listeriosis often rclatcd to silage feeding
Erysipelothrix rhusiopathiae
Gram-positive, small rods (smooth form) or
filaments (rough form)
Growth on non-enriched media
Small colonies, with incomplete haemolysis in
48 hours
Growth over wide temperature and pH ranges
Catalase-negative
Coagulase-positive
Non-motile, oxidase-negative, facultative anaerobe
H,S formed along stab line in TSI agar
Found in porcine tonsils
Causes swine erysipelas and turkey erysipelas
Bacillus species Keypoints
Large, Gram-positive rods
Endospores produced
Aerobes or facultative anaerobes
Growth on non-enriched media
Most species motile, catalasc-positive and
oxidase-negative
Majority are non-pathogenic environmental
organisms
Bacillus anthracis causes anthrax
= Bacillus licheniformis is implicated in sporadic abortions in cattle and sheep
Clostridium Species
Large, Gram-positive rods
Endospores produced
Anaerobic, catalase- and oxidase-negative
Motile (except C, perfringens)
Enriched media required for growth
Colonies of C. perfringens surrounded by zones of double haemolysis
Present in soil, in alimentary tracts of animals
and in faeces
Pathogens can be grouped according to the mode and sites of action of their potent exotoxins:
-neurotoxic clostridia
-histotoxic clostridia
enteropathogenic and enterotoxaemia producing clostridia
Produce diverse forms of disease in many animal species
Mycobacterium species Key Points
Acid-fast (ZN-positive) rods
Cell walls rich in complex lipids and waxes
containing mycolic acids
Complex egg-enriched media required for growth of pathogenic species ,
Aerobic, non-motile, non-spore-forming
Genus includes obligatc pathogens, opportunistic
pathogens and saprophytes
Pathogenic species grow slowly, colonies visible after several weeks
. Some mycobacteria produce caroterloid pignrents Resistant to chemical disinfectants and environmental influences but susceptible to heat treatment (pasteurization)
Multiply intracellulary and cause chronic,
granulomatous infections
Major discases include tuberculosis, Johne’s disease and feline Leprosy
Enterobacteriaceae
Gram-negative rods Growth on non-enriched media Oxidase-negative Facultative anaerobes, catalase-positive Most are motile by peritrichous flagella Ferment glucose, reduce nitrate to nitrite Enteric bacteria which tolerate bile salts in MacConkey agar Cause a variety of clinical infections = Major enteric and systemic pathogens: -Escherichia coli Salmonella serotypes -Yersinia species Opportunistic pathogens: -Proteus species -Enterobacter species -Klebsiella specie
Pseudomonas aeruginosa and Burkholderia Species
Medium-sized, Gram-negative rods
Obligate aerobes
Most isolates are oxidase-positive and catalasepositive
Pseudumonas species and Burkholderia
pseudomuilei are motile by polar ilagella
Burklholderia mallei is non-motile and requires 1
glycerol in media for optimal growth
Diffusable pigments are produced by P aeroginosa
Burkholderia mallei causes glanders
Burholderio pseudomallei causes mcl ioidosis i!i Prrudumorius aeruginosa causcs opportunistic infections
Actinobacillus species
Medium-sizcd, non-motile, Gram-negative rods
Facultative anaerobes
= Most species are oxidase-positive and produce
ureas
Species of veterinary importance
grow on MacConkey agar, apart from
Actinoblacillus pleuropneumoniae
Commensals on mucous membranes
Produce a wide range of disease conditioris in
domestic animals
Pasteurella and Mannheimia Species
Small Gram-negative rods
Optimal growth on enriched media
Non-motile, oxidase-positive, facultative
anaerobes
Most species are catalase-positive
Some species grow on MacConkey agar
Bipolar staining is prominent in smears from lesions, using the Giemsa Method
Commensals in the upper respiratory tract
Respiratory Pathogens
Francisella tularensis
Gram-negative coccobacillary rods Non-motile, obligate aerobes Fastidious, cysteine required for growth No growth on MacConkey agar Oxidase-negative, catalase-positive m Facultative intracellular pathogen Survives in the environment for up to 4 months Wildlife reservoirs and arthropods important in epidemiology causes tulaeremia in animals and humans
Haemophilus Species
Small, motile Gram-negative rods Fastidious, requirement for the X and V factors in chocolate agar Optimal growth in 510% CO, Facultative anaerobes
Commensals on mucous membranes of many animal species Important pathogens include 'Haemophilus somnus' (cattle) H. parasuis (pigs) and H. paragallinarum (poultry)
Taylorella equigenitalis
Short, non-motile Gram-negative rods
Fastidious, optimal growth on chocolate agar
Microaerophilic, 510% CO2 required Positive oxidase, catalase and phosphatase tests
but otherwise unreactive
Causes contagious equine metritis
Bordetella Bronchiseptica and Bordetella avium
Small Gram-negative rods
m Growth on non-enriched media and on
MacConkey agar
m Strict aerobes
m Motile, catalase-positive, oxidase-positive
m Utilize amino acids for energy
m Toxigenic strains agglutinate mammalian red
blood cells
m Commensals of upper respiratory tract
m Cause respiratory disease in mammals and birds
Moraxella bovis
Short Gram-negative rods, usually in pairs
Optimal growth on enriched media
rn Aerobic, non-motile
1 Usually catalase- and oxidase-positive
m Proteolytic, unreactive with sugar substrates
1 Virulent strains are fimbriated and haemolytic
m Susceptible to desiccation
= Found on mucous membranes of carrier cattle
Causes infectious bovine keratoconjunctivitis
Brucella species
m Small Gram-negative coccobacilli
rn Stain red using the modified Ziehl-Neelsen method
m Aerobic and capnophilic
a Non-motile, catalase-positive
m Most isolates are oxidase-positive
1 Urease-positive
rn Intracellular pathogens
m Target reproductive organs of certain species
m Some species cause undulant fever in humans
Campylobacter species
9 Slender, curved Gram-negative rods in gullwinged
shapes and spiral forms
1 Motile, microaerophilic
m Most species grow on MacConkey agar
9 Enhanced growth on enriched media
m Non-fermentative, oxidase-positive with variable catalase reactions
m Commensals of the intestinal tract and sometimes of the reproductive tract
Pathogens in the reproductive and intestinal tracts
Lawsonia intracellularis
Curved, Gram-negative rods
m Obligate intracellular pathogens
m Microaerophilic
1 No growth on inert media
Growth in tissue culture prepared from enterocytes
m Implicated in porcine proliferative enteropathy
Spirochaetes
Spiral motile bacteria with endoflagella
m Labile in the environment and sensitive to
. desiccation Although Gram-negative, many stain poorly using
conventional methods
m Some grow only in liquid media; most require
. specialized media Many produce zoonotic infections
m Leptospira species
-Found in aquatic environments
-Produce systemic infections in many species
-Shed in urine of affected species
–Cultured in liquid media aerobically at 30°C
-Dark-field microscopy, silver staining and
. immunofluorescence used for recognition Borrelia species
-Transmission by arthropod vectors
-Cause systemic infections in many species
-Grow slowly in specialized culture media at
30-35”C, in microaerophilic conditions
–Culture of borreliae from infected animal is
confirmatory
a Brachyspira I Serpulina species
-Intestinal spirochaetes; some are important
enteropathogens of pigs
-Can be demonstrated in stained faecal smears
or in silver-stained histopathological sections
-Diagnosis confirmed by culture on
selective blood agar anaerobically at 42°C
Mycoplasma
Smallest free-living prokaryotic microorganisms
m Possess triple-layered limiting membranes but I lack cell walls
Do not stain by the Gram method
1 Highly pleomorphic, filterable plastic forms
-m Susceptible to desiccation and disinfectants Microcolonies have a ‘fried-egg’ appearance
Most are facultative anaerobes
Do not replicate in the environment
Most are host-specific
Mycoplasma and Ureaplasma contain species
of veterinary importance
Mycoplasma species cause a wide range of
diseases in animals, including contagious bovine
pleuropneumonia
Clamydia
Sperical intracellular bacteria with unique
developmental cycle
Appropriate staining procedures include the
modified Ziehl-Neelsen and Giemsa methods
= Unable to synthesize ATP and replicate only in
living cells
= Cell walls lack .oe .~ tido-g.lv canb ut contain
genus-specific lipopolysaccharide
1 Species vary in virulence for particular hosts;
some strains are associated with specific diseases
in domestic animals
m Produce respiratory, enteric, plural and
reproductive tract diseases in animals and humans
Rickettsiales
Minute, non-motile Gram-negative bacteria
m Obligate intracellular pathogens, replicating only
in cells
m Demonstrated in blood smears by Romanowsky
stains
Host specificity and tropism for particular cell
types evident
* Extracellular survival brief for most members
apart from Coxiella burnetii
Cause systemic diseases, mainly arthropodborne,
in humans and animals
Rickettsiaceae
–cell walls often contain peptidoglycan
–cultured in specific cell lines or in fertile eggs
-tropism for vascular endothelium or leukocytes
m Anaplasmataceae
-lack cell walls, possess cell membranes
-have not been cultured in vitro
–tropism for erythrocytes
