Gram positive bacteria

Staphylococcus

commensals of skin

causes purulent infections

major Staphylococcus species

S. aureus

S. pseudintermedius

S. hyicus

Staphylococcus aureus

botryomyocosis (chronic pyogranulomatous inflammation)

rare post-castration complication in horses

bumble foot

Staphylococcus aureus in poultry

local chronic pododermatitis/tenosynovitis of foot

can also cause septicemia and osteomyelitis

S. pseudintermedius

skin infections in dogs

pyoderma and otitis externa (swimmer’s ear)

S. hyicus

greasy pig dz

1-6 wk old piglets

exudative epidermitis

coagulase neg staphylococcus sp

nosocomial and UTIs

can colonize in dwelling in catheters, implants, forming biofilms causing bacteremia and endocarditis 

staphylococcus can release

superantigens—can cause toxin-mediated diseases (TSS)

antimicrobial resistance in staphylococcus

methicillin resistant S. aureus and S. pseudintermedius

streptococcus genus

gram positive

commensals of skin and mucous membranes 

streptococcus equi equi

strangles

high morbidity low mortality

how does strangles spread

horses shedding bacteria and the contaminated environment

what age are most susceptible to strangles

young and weaned

<4 mo are still covered by maternal antibodies

when do clinical signs appear of strangles and what are they 

3-14 d after exposure 

fever, moist cough, purulent nasal discharge

abscess in lymph node region around 2 weeks after initial signs

how to test carrier state of strangles

it is a reportable disease in most states

test guttural pouch 30 d after recovery to test long term carrier state

streptococcus equi subsp. zooepidemicus 

opportunist 

purulent infections—upper respiratory, pneumonia, infections of urogenital, mastitis, septicemia 

streptococcus canis

often observed as perinatal infection from vagina or umbilical vein resulting in skin ulceration, chronic respiratory infection, toxic shock-like syndrome, death

streptococcus suis

pathogenic or commensalistic in pigs and humans

variety of conditions: septicemia, serositis, meningitis, polyarthritis, pneumonia, abortion, abscesses

issue with zoonosis with streptococcus suis 

can lead to meningitis 

S. procinus

jowl abscess in pigs

S. iniae

zoonosis from fish 

S. algalactiae and S. dysgalactia 

contagious or chronic mastitis in cattle

S. uberis

subclinical mastitis in cattle

enterococcus spp.

opportunistic pathogen seen as normal intestinal flora and consists of numerous species

causes a range of low-grade to severe infections including mastitis, wound infections and urinary tract infections 

enterococcus spp. has a natural

intrinsic antimicrobial resistance and the emergence of Vancomycin resistance is a concern 

bacillus anthracis

cause of anthrax

sporadic cases are mostly restricted to cattle and are transmitted from soil contaminated with spores 

Bacillus anthracis is a “_________”

biological warfare agent and exposure can lead to multiple manifestations

major virulence factors of Bacillus anthracis

anti-phagocytic capsule produced only in vivo (in the host)

tripartite toxin consisting of 3 proteins

1. edema factor

2. lethal factor

3. protective antigen

what does the toxin in bacillus anthracis do

impairs or kills neutrophils and macrophages leading to bacterial replication in the blood resulting in the release of inflammatory mediators from macrophages, and death occurs through septic shock 

ruminant anthrax

per acute septicemia

horse anthrax

acute septicemia

human anthrax

pulmonary (wool sorter’s disease)

pig and dog anthrax

pharyngeal 

anthrax in humans, pigs, horses

intestinal

what animal is most susceptible to anthrax

cattle

infection results in rapidly fatal disease often with high fever, bleeding from orifices, shock, and respiratory distress

anthrax post mortem signs 

dark, unclotted blood from natural orifices and dead animals presented with incomplete rigor mortis 

splenomegaly

current-jelly spleen

typically postmortem lesion if you open the carcass and is an indication to suspect anthrax 

you must do what for anthrax

report

proper carcass disposal

diagnosis of anthrax can be made by examining

peripheral blood smears stained with polychromatic methylene blue staining rods with pink capsule (80% of bacteria in blood at the time of death)

cultures and PCR must be attempted only by reference labs

control of anthrax

vaccination using anthrax spore vaccine in healthy animals in endemic/high risk areas

anthrax zoonosis status

can spread to humans often airborne and lethal pulmonary forms

Listeria monocytogenes

facultative intracellular bacterium

ubiquitous in the environment and animal intestinal tract

capable of growing in the fridge (psychrophilic)

how L. monocytogenes is spread in humans

consumption of contaminated products (Food)

L. moncytogenes spread in ruminants

feeding poor quality silage

LIteria monocytogenes invades

through the oral mucosa

travels along the trigeminal nerve

localizes in the brain leading to neurologic signs

circling disease 

Listeria monocytogenes or silage disease in cattle 

observed in winter/spring after feeding poor-quality silage 

post-mortem lesions of L. mono.

micro abscesses in the brain (brain stem)

minigitis with acute vascular necrosis

neuritis

peri-neuritis of cranial nerves

septicemic listeriosis

induced (calves < 3 weeks old) and major lesions include focal hepatic necrosis and hemorrhagic gastroenteritis

listeria enrichment culture 

used for diagnosis 

Erysipelothrix rhusiopathiae

gram positive rod

inhabits tonsils and intestines of animals 

most common in pigs and turkeys 

E. rhusiopathiae in pigs

occurs by ingestion

swine erysipelas or diamond skin disease

lesions due to bacteremia resulting in inflammation of the blood vessels

acute and subacute forms result in septicemia

chronic forms result in endocarditis, polyarthritis, and skin lesions

E. rhusiopathiae in sheep

rsult in non-suppurative polyarthritis and outbreaks of post-dipping lameness when contaminated dipping solutions are used

zoonosis E. rhusiopathiae

localized cellulitis in fingers in humans

corynebacterium pseudotuberculosis 

causes caseous lymphadenitis 

chronic pyogranulomatous infection of lymph nodes in sheep and goats 

resulting in chronic contagious disease characterized by weight loss and emaciation 

serology test for C. pseudotuberculosis

using synergistic hemolysin inhibition (SHI) test that detects antibodies to the phospholipase D exotoxin is used

disease is not “curable”

control—biosecurity and vx

pigeon fever in horses

colorado strangles, dry land distemper

different biotype of Corynebacterium pseudotuberculosis

how does bacteria enter for pigeon fever 

through skin abrasions and cause ulcerative lymphangitis of the lower extremities and abscesses in the pectoral region and ventral abdomen

Corynebacterium renale group

C. renale, C. cystiditis, C. pilosum

commensals of the urogential tract and cause contagious bovine pyelonephritis in adult cows

Corynebacterium kutscheri

causes murine pseudotuberculosis, a suppurative pneumonia, and similar lesions in other organs

Corynebacterium bovis

causes dermatitis and hyperkeratosis in mice

Rhodococcus equi

a significant pathogen of horses, is an opportunistic facultative intracellular pathogen in soil

Rhodococcus equi infection

foal pneumonia

slowly progressive disease resulting in pyogranulomatous lesions in the lungs and other organs 

how to test for foal pneumonia

Cytology of the transtracheal wash will demonstrate intracellular coccobacilli in macrophages.

Nocardia

e facultative intracellular bacteria, ubiquitous in the soil and water, and cause pyothorax, mastitis, pneumonia, abscesses, cutaneous/subcutaneous lesions, and mastitis during dry-cow treatment.

Actinomyces bovis

s causes pyogranulomatous osteomyelitis (lumpy jaw) of cattle, a localized, chronic, progressive, pyogranulomatous abscess involving the mandible, the maxillae, or other bony tissues in the head

How actinomyces bovis enters body

bacteria introduced via penetrating wound of the oral mucosa

bone infections result in facical distortion, loose teeth, dyspnea from swelling into the nasal cavity 

Dermatophilus congolensis

causes skin lesions in animals and is most frequent in cattle and horses.

Motile zoospores of bacteria are chemotactic and attracted to moist, damaged skin, resulting in keratinolysis leading to epidermal abscesses with hyperkeratosis.

The infection can be diagnosed by microscopic demonstration of bacteria in scabs appearing as a “tram-track” pattern

Trueperella pyogenes

an important opportunistic pathogen causing chronic purulent infections in ruminants and swine.

Disease prevalence is sporadic and predisposed by stress or trauma.

Causes a wide variety of symptoms, including abscesses, mastitis, metritis, abortion, omphalophlebitis, and chronic pneumonia.

Actinobaculum suis

an anaerobic sexually transmitted bacteria that causes porcine cystitis and pyelonephritis