Bacterial zoonoses infections associated with bites Flashcards
Leptospira: shape and living conditions
long thing motile spirochete
poor staining > dark field microscopy needed
may be free living or associated with animal hosts (rodents) and survive well in freash water, soil and mud in tropical areas
molecular taxonomic studies identified 17 speices of pathogenic leptospires
leptospira transmission
infection occurs through abrasion or cuts in the skin or through the conjunctiva and mucous membranes
humans may be infected by direct contact with urine or reproductive fluids from infected animals or with water or soil contaminated with those fluids
prolonged immersion in contaminated water increases the risk for infection: outbreaks in triathlons
infection rarely occurs through animal bites or human to human contact
Leptospira occurence
world wide distribution, with a hgiher incidence in tropical climates
proliferate in fresh water, damp soil or mud
flooding after hurricanes facilitates the spread of the organism, contributing to outbreaks
rodent borne leptospirosis may be a risk to persons exposed to rat urine in infested urban areas
Leptospira clinical manifestations
Self limited systemic illness (flu-like) in 90% of patients
can be life threatening with jaundice and renal dysfunction (weil syndrome)
usually biphasic: 1- septicemic 2- immune mediated (fever, aseptic meningitis, uveitis, purpuric rash)
leptospira diagnosis
based on serology: microscopic agglutination test (MAT)
antibodies may be detected in the blood within 5-7 days of symptom onset
culture or demonstration of the organism under dark field microscopy are both relatively insensitive
No pcr assay validated with clinical specimens
leptospira rx, prevention and control
mild disease: doxycycline
IV penicillin is the drug of choice for severe disease
preventio: doxycycline 200 mg weekly for high risk occupational exposure
vaccination: livestock, pets
rodent control
Tularemia: gram stain, source
francisella tularenisis
aerobic and fastidious gram negative bacterium
source: wild and domestic mammals and their ticks/deerflies
in US, ticks and rabbits are major sources
tularemia transmission
Human infection: skin mucous membrane contact with tissue/body fluids of infected animals. Bites of deerflies, mosquitoes, ticks. Less common, but still happens, inhalation of dusts (lawn mowing over animal carcasses). Ingestion of contaminated foods and water.
Viable in water, soil, caracsses for weeks: highly contagious
person to person transmission does not occur
Tularemia: clinical manifestations
Ulceroglandular: most common. Maculo papular lesion at entry site, with later ulceration and painful
lymphadenitis
oculo glandular
oropharyngeal
pneumonic
typhoidal (fever, hepatosplenomeagaly)
intestinal
Tularemia: DX
micrscopy exercise extreme caution (let micro lab know of suspicion, need of BSL III)
culture: cysteine enriche chocolate blood agar, incubation for longer time
serology: 4 fold increase in IgG in paired specimens (may cross react with brucella) or 1 titer > 1: 160
Tularemia: RX and prevention
TX: streptomycin is the drug of choice based on experience, efficacy and FDA approval. Gentamicin is considered an acceptable alternative, but some series have reported a lower primary success rate
Prevention: gloves, rapid removal of ticks, cook wild meats, insect repellents
Brucellosis
Brcella
small, non motile gram neg coccobacilli
grows slowly and in special media\
intracellular replicates in reticuloendothelial system
four species: B abortus (cattle), B melitensis (gaots, sheep), B. Suis (swine), B. canis (dogs, coyotes)
Brucellosis: epidemoiology
worldwide distribution, esp latin America, Middle east, africa
In USA: rare. most of cases in CA and TX (imported from mexico). Associated with unpasteurized milk and dairy.
Acquired via direct contact with organism (labs), ingestion or inhalation
has a predilection for infection tissues rich in erythritol (animal breast, uterus, placenta)
high bacterial load in milk and birth products
Burcellosis: clinical manifestations
undulant fever
malaise, fever, chills, sweats, arthralgias
can become chronic
can progress to systemic involvement: GI tract, respiratory, bones. Suppurative complications
Brucellosis: DX
serology: serum agglutination test (SAT). 4 fold increase in IgG or single titer > 1:160
Cultures: blood tissues. lab should be notified. SHould be incubated for two weeks.
Bone marrow cultures offer high yield
microscopy is insensitive
Brucellosis: treatment and prevention
combination therapy for 6 weeks
doxycycline and rifampin for at least 6 weeks
tmp-smx and rifampin for pregnant/children
relapses are common if treated fro less than 6 weeks
control of human cases is done through control of disease in livestock. animal vaccination, elimination of infected herds. Avoid unpasteurized products.
Plague: Yersinia pestis
gram negative, bipolar staining bacillus
safety pin appearance on gram stain.
maintained in rodents and feas
In us, mainly rural disease: average of 10 to 15 cases each year.
globally 1,000 to 3,000 cases of plague every year
Plague: black death
one of the most devastating pandemics in human history, peaking in europe between 1348 and 1350
millions of peopel in europe died from plague in the middle ages, when human homes and places of work were inhabited by flea infested rats.
male xenopsylla cheopis is the primary vector of plague.
Plague clinical manifestations 3 forms.
Bubonic (most common): mortality=50%. usually lowe rextremeities , bitten by flea. Lymph nodes enlarge.
Primary septicemic: hyptension resp distress, pura pura, DIC
Pneumonic: mortality: 100%. cough, fever, hemoptysis. Primary route: inhalation. Secondary; via bubonic or septicemia. Only form that is transmitted person to person.
plague DX
on gram or wayson stain: safety pin
immunofluorescent stain increased sensitivity
PCR only in reference labs (state/CDC)
culture
genotyping shoudl be performed to detect if isolate is endemic or engineered (potential for bioterrorism)
serology: passive hemagglutination or EIA
Plague: management
standard precautions for buibonic
droplet precautions for pneumonic plague for at least 48 hours and clinical response to therapy
severe infection: mortality 50-90% if untreated. 15% when diagnosed and treated
plague TX
streptomycin, tetracycline, chloramphenicol, gentamicin
meningitis: chloramphenicol
drainage of buboes
prophylaxis of contacts with close exposure to pneumonic plauge with doxycycline.
Plague control
national notifiable disease
early detection and tx of affected cases
control rat and fleas
Coxiella burnetii
Q fever (Q for query)
short, pleomorphic rod, possessing a membrane similar to a gram negative bacterium
strict intracellular
worldwide distribution: reservoir: cattle, sheep, goats, dogs
routes: inhalation of contaminated aerosols from birthing fluids or dust or direct exposure to tissues. Ingestion of unpasteruized dairy products
Q fever: clinical manifestations
often asymptomatic (60%)
acute disease; 20 days incubation. HA, high fever, chills, myalgias. Atypical pneumonia. 50% liver/spleen enlargement
Chronic disease: rare, subacute endocarditis, incubation months to years, pregnant and immunosuppressed are more likely to develop chronic infection
Q fever: DX, RX, prevention, control
culture: possibly, rarely done (biosafety)
serology: acute phase II ag (igM, IgG). Chronic: Phase I and Phase II ab; 1»2
RX: acute q fever: doxycycline. Chronic q fever: doxycycline and hydroxychloroquine.
control: safety practices in farms (esp handling parturient animals)
bartonella henselae (cat scratch fever)
fastidious, aerobic gram negative rod.
reservoir: cats and fleas: lives in feline oropharynx and can cause transient bacteremia in kittens > cat scratch disease.
CSD
common in children
chronic regional lymphadenopathy of nodes draining site of contact
can also cause osteomyeltis, hepatic involvement, prolonged fever with no source: cause of fever of unknown origin (FUO)
generalized infection in immunocompromised patients > bacillary angiomatosis
CSD dx and tx
cultures usually negative
diagnosis: serology. IgG titers (IgM is unreliable)
course: self limited
TX: azithromycin, ciprolfoxacin, TMP-SMX
avoid surgical drainage (fistual formation)
animal bites
mouth flora of animals > infection post bites
P multocida, anaerobes, strep, SA, capnocytophaga: common in cats/dogs
humans: eikenella, aerobic streptococci and anaerobes
cat bites are more prone (80%) to infection than dog bites (10%)
puncture wounds are more prone to infection
Management of animal bites
wound care: irrigate, debridement
wound closure: NO
fracture, foreign body?: imaging needed sometimes
prophylactic antibiotics
vaccines (tetanus and rabies)
Pasteurella
small, fermentative, gram neg. cocco bacillus (small rod)
P. multocida (in 90% of cat saliva, but also dogs)
P. Canis (in saliva of 50% of dogs)
typical clinical picture of rapidly developing cellulitis after bites (within 24 hs.)
resistant to clindamycin and 1st gen cephalosporins
TX: penicillin
some strains can produce B lactamases > amoxicillin clavulanic recommended
Capnocytophaga canimorsus
slowing growing, gram negative fusiform bacilli
tirkcy susceptibility to antibiotics
resistant to TMP-SMX
produces beta lactamases: treat with amoxicillin clavulanic
Eikenella corrodens
more common in human bites/fistfights injury: colonizes human oropharynx
small, fastidious gram neg rods (HACEK)
Name origin: ability to corrode agar (splits polyglacturonic acid) and bleach like odor
susceptible to penicillin
resistant to clindamycin and 1st gen cephalosporins
