Bacterial zoonoses infections associated with bites

Question 1

Leptospira: shape and living conditions

Answer 1

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

Question 2

leptospira transmission

Answer 2

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

Question 3

Leptospira occurence

Answer 3

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

Question 4

Leptospira clinical manifestations

Answer 4

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)

Question 5

leptospira diagnosis

Answer 5

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

Question 6

leptospira rx, prevention and control

Answer 6

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

Question 7

Tularemia: gram stain, source

Answer 7

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

Question 8

tularemia transmission

Answer 8

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

Question 9

Tularemia: clinical manifestations

Answer 9

Ulceroglandular: most common. Maculo papular lesion at entry site, with later ulceration and painful

lymphadenitis

oculo glandular

oropharyngeal

pneumonic

typhoidal (fever, hepatosplenomeagaly)

intestinal

Question 10

Tularemia: DX

Answer 10

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

Question 11

Tularemia: RX and prevention

Answer 11

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

Question 12

Brucellosis

Answer 12

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)

Question 13

Brucellosis: epidemoiology

Answer 13

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

Question 14

Burcellosis: clinical manifestations

Answer 14

undulant fever

malaise, fever, chills, sweats, arthralgias

can become chronic

can progress to systemic involvement: GI tract, respiratory, bones. Suppurative complications

Question 15

Brucellosis: DX

Answer 15

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

Question 16

Brucellosis: treatment and prevention

Answer 16

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.

Question 17

Plague: Yersinia pestis

Answer 17

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

Question 18

Plague: black death

Answer 18

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.

Question 19

Plague clinical manifestations 3 forms.

Answer 19

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.

Question 20

plague DX

Answer 20

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

Question 21

Plague: management

Answer 21

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

Question 22

plague TX

Answer 22

streptomycin, tetracycline, chloramphenicol, gentamicin

meningitis: chloramphenicol

drainage of buboes

prophylaxis of contacts with close exposure to pneumonic plauge with doxycycline.

Question 23

Plague control

Answer 23

national notifiable disease

early detection and tx of affected cases

control rat and fleas

Question 24

Coxiella burnetii

Answer 24

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

Question 25

Q fever: clinical manifestations

Answer 25

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

Question 26

Q fever: DX, RX, prevention, control

Answer 26

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)

Question 27

bartonella henselae (cat scratch fever)

Answer 27

fastidious, aerobic gram negative rod.

reservoir: cats and fleas: lives in feline oropharynx and can cause transient bacteremia in kittens > cat scratch disease.

Question 28

CSD

Answer 28

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

Question 29

CSD dx and tx

Answer 29

cultures usually negative

diagnosis: serology. IgG titers (IgM is unreliable)
course: self limited

TX: azithromycin, ciprolfoxacin, TMP-SMX

avoid surgical drainage (fistual formation)

Question 30

animal bites

Answer 30

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

Question 31

Management of animal bites

Answer 31

wound care: irrigate, debridement

wound closure: NO

fracture, foreign body?: imaging needed sometimes

prophylactic antibiotics

vaccines (tetanus and rabies)

Question 32

Pasteurella

Answer 32

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

Question 33

Capnocytophaga canimorsus

Answer 33

slowing growing, gram negative fusiform bacilli

tirkcy susceptibility to antibiotics

resistant to TMP-SMX

produces beta lactamases: treat with amoxicillin clavulanic

Question 34

Eikenella corrodens

Answer 34

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