Gram Pos: Staphylococcus Flashcards
Describe the bacterial characteristics of staphylococcus.
-gram pos cocci in clusters
-facultative anaerobes
-non motile, non spore forming
-catalase +
-normal host associated microbiota ‘commensal’ on skin & mucus membrane
>URT (nose/nares)
>lower urogenital tract
>GIT
-host: human, animal, environment (stable)
-opportunistic, suppurative infections w pus filled lesions (abscess)
Describe virulence factors & pathogenesis.
-pyogenic bacteria are opportunistic pathogens
-subclinical to acute & severe or peracute, severe, & life threatening
Describe protein A.
-inhibition of opsonization
-goal is to decrease phagocytosis
Describe coagulase.
-fibrinogen -> fibrin
-S. Aureus can coat w fibrin (fibrin clot) to protect bacteria from phagocytosis = more virulent
Describe coagulase test.
-detects most virulent staphylococci
(+) = fibrinogen converted to fibrin by coagulase & visible clot formation in tubes
(-) = coagulase neg staphylococci (CoNS)
>ex: s. Epidermidis
Describe species of vet imp.
Describe classification of mastitis.
- Environmental mastitis
-subclinical mastitis - Clinical mastitis
-peracute gangrenous
-acute
-chronic (intermittent acute episodes during lactation)
Describe bovine staphylococcal mastitis.
-contagious mastitis in cattle caused by s. Aureus
-majority not cleared by IS -> chronic, low grade or sub clinical -> production loss
-source of infection = from infected mammary gland of another cow in herd
-host predisposition = impaired phagocyte function -> pathogen survive in mammary gland
-transmission:
>milking thru contaminated hands of milker
>teat cup liners & udder cloths
Describe peracute gangrenous, acute, & chronic subclinical mastitis.
- Peracute gangrenous
-venous thrombosis & local edema
-tissue necrosis, udder discolor
-swollen quarters, sore on palpitation
-fever, depression, anorexia - Acute
-severe swelling of gland
-purulent secretion w clots in milk
-fibrosis - Chronic subclinical (most common)
-elevated somatic cell counts
-episode of bacterial shedding
-inflam response -> block ducts & atrophy of alveoli
Describe the T & P of BSM.
-proper milking technique & good hygiene during milking
>single use paper towel to dry teat
>milker gloves
>teat dip after milking
-dry cow therapy
-detect subclinical infections
>segregation of infected cows
>antimicrobial treatment for severe acute
>cull chronic
-prevent intro of pos cows into herd
Describe botryomycosis.
-rare chronic granulomatous suppurative disorder w formation of micro abscessation
-post castration complication in horses (open castration w lack of hygiene)
-cutaneous form w small sub dermal granulomas
-treatment: long term AB treatment & removal of affected tissue
-prevention: hygiene during surgical procedures, proper wound care
Describe bumblefoot.
-local chronic pododermatitis (tenosynovitis) of foot in birds
-bacteria entry thru weakened area or scratch in bird foot -> staphylococcal arthritis & septicemia in turkeys
-prevention: good husbandry
Describe pyoderma, otitis externa, & other suppurative conditions.
-local skin disease in dogs & cats
>otitis externa, infected wounds, UTI, vaginitis, metritis, balanitis, conjunctivitis, bacteremia, abscesses
-S. PSEUDINTERMEDIUS most common opportunistic pathogen in dogs
-primary cause for otitis externa are parasites, food allergy, foreign body, hair, autoimmune disease, anatomic predisposition, pustules
-secondary cause is bacterial infections
Describe bacterial pyoderma.
-triggered by overgrowth of normal resident or transient skin microbiota
-skin disease that changes dry -> humid can predispose host to overcolonization
*S. Pseudintermedius
S. Aureus
colonization doesn’t equal infection
Describe pyoderma T & P.
-ID of underlying problems
-cleansing shampoo -> antimicrobial shampoo
-topical VS systemic antibiotics
>narrow spec
-ointment
-groom hair
Describe greasy pig disease.
-contagious exudative epidermis in suckling & weaned pigs up to 3mo of age (NO pus & generalized)
-excessive sebaceous secretion & exfoliation, anorexia, depression, fever
-morbidity 20-100%, mortality 90%
-S. Hyicus can be isolated from vag mucosa & skin of healthy sow & preputial diverticulum of boars
-entry of skin thru abrasions
Describe greasy pig disease T & P.
-early systemic antibiotics therapy + topical treatment w antiseptic or antibiotic
-isolation of infected pigs
-cleaning & disinfect buildings
-clip needle teeth of newborn pig
-soft bedding, good hygiene
Describe staphylococcal toxic shock syndrome (TSS) & food poisoning.
- TSS = caused by effect of superanitgens entering bloodstream
-fever, headache, vomit, diarrhea
-conjunctival reddening, hypotension, skin rash, kidney failure - Food poisoning = caused by s. Aureus that has made enterotoxins
-nausea, vomiting, ab cramp, diarrhea, sweating
Describe lab diagnosis.
- specimen: exudate, pus from abscess, mastitis milk, skin scrape, urine, affected tissue
- direct microscopy = gram stain
>gram + cluster & evidence of inflam w high neutrophil - isolation
>culture on selective blood agar for hemolysis & MacConkey agar (absence of growth)
>contaminant (CoNS), resident or pathogen - Molecular typing w PCR
Describe treatment of s. Aureus.
-antimicrobial & elimination of primary cause
-therapy depends on infection site, severity, staphylococcal strain
>amoxicillin, penicillinase resistant B lactam, aminoglycosides, cephalosporins, clindamycin
>quinolones not rec
-antimicrobial susceptibility testing rec
Describe AMR.
-B lactamase mediated resistance common in staphylococcal spp
-methicillin resistance in s. Aureus (MRSA) & S. Pseudintermedius (MRSP)
-resistance to B lactam antibiotics often coincides w resistance to other antibacterial drugs -> multi drug resistance (macrolides, aminoglycosides, tetracycline, sulfa)
Describe MRSA.
-methicillin resistance mediated by mecA gene resulting in altered penicillin binding proteins
-hospital acquired infections (nosocomial) & inc circ of community acquired infections by MRSA
Describe MRSA VS MRSP.
-rapidly emerging
-reflect lax infection control or predisposition
-household transmission & occupational risk
-colonization of animals by human MRSA is transient & vice versa
-staphylococci at human animal interface = potential route of dissemination of AMR
Describe infection control.
-nares most common site of colonization
-hands most common source of transmission in humans
-contact precaution
-awareness of inc risk
-isolation of animals
-counsel owner w potential risk
-immunocompetent old client consult w physician
-people in patient care assume potential source of disease
-prevention
-hygiene & herd management
-choose antibiotic wisely
-underlying primary cause
