zoonotic bacterial dz

Question 1

Modes of zoonotic bacterial acquisition

Answer 1

cutaneous contact (bites), arthropod vector, inhalation, ingestion

Question 2

ZOONOTIC INFECTIONS-Definition

Answer 2

•Infections which are transmitted between man and other vertebrate animals. Humans are not necessary for transmission of zoonotic infections in nature. Infections in other animal host are frequently asymptomatic or mildly symptomatic

Question 3

Name the bacteria associated with the following diseases: plague, Tularemia, Lyme’s disease, cat scratch fever, Typhus

Answer 3

plague: Yersinia pestis. Tularemia: Francisella tularensis. Lymes disease: Borrelia burgdorferi. Cat scratch: Bartonella species. Typhus: Rickettsia species

Question 4

What caused the black death

Answer 4

The plague- yersinia pestis transmitted by fleas

Question 5

define enzootic plague

Answer 5

A stable rodent - flea infection cycle that is maintained in a relatively resistant host population without excessive host mortality; a long-term reservoir of infection

Question 6

define epizootic plague

Answer 6

Occurs when plague bacilli are introduced into rodent or small mammal populations that are moderately or highly susceptible to the lethal effects of the infection

Question 7

define zootic plague

Answer 7

Transmission from animals to humans. Cats (NOT dogs) can develop pneumonic disease which can allow the organism to spread directly to people (e.g. veterinarians) without an intermediate insect vector. Fleas are usually responsible for human transmission though.

Question 8

define demic plague

Answer 8

Transmission from humans to humans (e.g. Pneumonic Plague which is spread by aerosols)

Question 9

types of plague

Answer 9

BUBONIC - Fever, painful lymphadenopathy from bite of flea 2-5 days earlier - 60-90% mortality untreated. SEPTICEMIC - - fever, hypotension, Invasion of almost all organs; no significant evidence of prior disease - death occurs in 12-24 hours. Usully from ingestion. PNEUMONIC - primary or secondary lung infection which is highly infectious and 100% fatal untreated.

Question 10

Yersinia Pestis structure

Answer 10

Bipolar “safety-pin” Staining Bacteria. facultative bipolar-staining Gram-negative bacillus with capsule belonging to the Enterobacteriaceae. Contains coagulase-fibrinolysin. Grows more slowly at 37oC than at 28oC. Plasmids provide virulence and encode complement-resistant determinants and YOPS (tyrosine phosphatases) that interfere with phagocytes.

Question 11

Y. enterocolitica/Y. pseudotuberculosis

Answer 11

less virulent relatives of Y. pestis cause enterocolitis (which mimics an appendicitis), reactive arthritis, septicemia, and mesenteric adenitis,

Question 12

Septicemic plague complications

Answer 12

Hallmarks are ecchymoses (rupture of blood vessels under skin) and petechia, complicated by DIC

Question 13

Yersinia pestis virulence factors

Answer 13

Ability to penetrate and multiply in non-phagocytic eukaryotic cells, and to kill phagocytic cells. These actions are due to: 1. plasma encoded genes: VW surface antigens; Type III secreted proteins -tyrosine phosphatase, cytotoxic factors; Flea associated virulence factors - coagulase-fibrinolysin. 2. Chromosome encoded genes: iron acquisition systems, attachment and invasion factors, endotoxin

Question 14

Plague diagnosis

Answer 14

Wayson/Giemsa/Gram strains of a bubo aspirate; bubo/blood/sputum culture with confirmation by fluorescent antibody; serology

Question 15

Plague treatment

Answer 15

streptomycin; supportive care; alternative: tetracycline, chloramphenicol and fluoroquinolones. You have to use antibiotics that are effective against intracellular pathogens since many will not penetrate human cells.

Question 16

Plague prevention

Answer 16

killed vaccine gives short-term protection to high-risk individuals. (e.g. All laboratory and field personnel who are working with Y. pestis

Question 17

Francisella tularensis transmission/ life cycle

Answer 17

Spread occurs from wild-animal reservoirs to domestic animals, especially rabbits and cats, and transmission to humans results from animal or insect bites, the handling of infected animal tissues, or inhalation of aerosolized organisms during activities such as landscaping or lawn mowing.

Question 18

Francisella tularensis infectious dose

Answer 18

This is one of the most infectious bacterial organisms known. < 50 organisms applied to the unbroken skin can cause an infection; 5 - 10 organisms by the respiratory route; 10^6 - 10^8 organisms by ingestion. However, F. tularensis infections are not a severe as those caused by Y. pestis.

Question 19

Types of Tularemia

Answer 19

Glandular - lymph node only. from a tick bite or other arthropod; no apparent lesion. Ulceroglandular - breach of skin; direct contact with infected animals (rabbits, rodents, coyotes)- ulcers (80% of cases). tender regional lymph node and a local papule that evolves into a chancriform lesion. Oculoglandular- inoculation of infected material directly into the eye or conjunctiva (~1%). Typhoidal - ingestion of contaminated material (meat, H2O). systemic disease without localized findings. Pulmonary - inhalation of contaminated material or hematogenous spread- occupational disease (bioterrorism??)

Question 20

Francisella tularensis structure/ growth

Answer 20

Aerobin, pleomorphic Gram-negative coccobacillus that requires cysteine for growth; survives intracellularly; phase variation allows organism to avoid host immune system.

Question 21

Which animals is F. tularensis most often associated with?

Answer 21

Type A is most commonly associated with infections with rabbits and cats

Question 22

Tularemia diagnosis and treatment

Answer 22

diagnosis: serology. Treatment: Streptomycin or Gentamicin. Alternatives are levofloxacin, chloramphenicol or doxycycline.

Question 23

Compare/contrast Tularemia and plague

Answer 23

Both are potential Bioterrorist weapons, Both are spread by aerosol and insect vectors, Both present with similar symptoms - Plague is usually more severe and more likely to be fatal. Only Plague can be transmitted person to person (i.e. pneumonic plague). A person with Tularemia does NOT spread the infection to another person.

Question 24

Lyme disease- mode of transmission

Answer 24

Bite of Ixodes tick infected with Borrelia burgdorferi. Animal reservoirs include white-footed mouse and deer. Ticks have a 2 yr life cycle

Question 25

Borrelia burgdorferi structure

Answer 25

loosely-coiled spirochete; difficult to culture from humans.

Question 26

Lyme disease diagnosis

Answer 26

clinical. Serology in late dz but cant differentiate btw active/ previous dz. Use two tier testing: ELISA or IFA, confirmed by western blot. PCR not standardized. Infection with Babesia, Ehrlichia or tick-borne encephalitis must be ruled out.

Question 27

Lyme disease clinical features

Answer 27

Erythema migrans, recurrent arthritis. Also possible is Bells palsy, radiculoneuropathy, meningitis/ encephalitis and cardiac problems

Question 28

Stages of Lyme disease

Answer 28

1. 3-30 day incubation period. 2. Stage 1- Localized infection, 1-4 weeks. Causes erythema migrans due to organisms multiplying in skin. 3. Stage 2- Disseminated infection 1 week- 6 months, symptoms are commonly intermittent. Secondary annular skin lesions, meningitis, carditis, musculoskeletal pain, eye abnormalities. 4. Stage 3- latent infection 6 months to 30 years. Acrodermatitis chronica atrophicans. Intermittent or chronic arthritis, chronic encephalopathy, polyneuropathy or leukoencephalitis, chronic cardiomyopathy

Question 29

Describe erythrema migrans

Answer 29

Bulls eye rash. It may be warm, but is not usually painful. . The binding of human plasminogen and its activators to the surface of the spirochete may facilitate spread through the skin and other tissue matrices.

Question 30

describe arthritis in Lyme disease

Answer 30

Large joint (knee) arthritis occurs months after exposure. Spirochetal decorin-binding proteins A and B bind decorin, a glycosaminoglycan on collagen fibrils; this binding may explain why the organism is commonly aligned with collagen fibrils in the extracellular matrix in the heart, nervous system, or joints

Question 31

Most common cardiac conditions associted with Lyme disease

Answer 31

conduction block

Question 32

Sx and treatment for suspected Lyme dz (high probability)

Answer 32

Sx: erythema migrans. Treatment: Empirical antibiotic treatment without serologic testing

Question 33

Sx and treatment for suspected Lyme dz (intermediate probability)

Answer 33

Sx: oligoarticular arthritis. Plan: Serologic testing and antibiotic treatment if test results are positive

Question 34

Sx and treatment for suspected Lyme dz (low probability)

Answer 34

Sx: nonspecific findings like myalgias, arthralgias and fatigue. Plan: Neither serologic testing nor antibiotic treatment

Question 35

Which Abx are used for Lyme disease

Answer 35

doxycycline for early disease (oral) if >9. Alternatives are amoxicillin cefuroxime, azithromycin. Amoxicillin if <9 yrs. ; ceftriaxone (IV) 2-4 wks for neurologic disease

Question 36

Lyme vaccine

Answer 36

Arthritis side effects. NO longer in use