YERSINIAE, PASTEURELLA€¦ · endotoxic activity The three pathogenic species - produce antigens and toxins that act as virulence factors. (2) The virulent yersiniae produce V and

YERSINIAE, PASTEURELLADrThin Thin Mar

Modified by Pro. WWMaw

PREVENTION

• Zoonotic• Vector-borne• widespread pandemics• Bioweapon• Category A select agent • required biosafety level 3 (BSL-3) facilities

YERSINIAE

• are short, pleomorphic gram-negative rods that can

exhibit bipolar staining

– are catalase-positive

– oxidase-negative ???

– microaerophilic or facultatively anaerobic

• Most have animals as their natural hosts, but they

can produce serious disease in humans

YERSINIAE

• The genus Yersinia includes

1 .Yersinia pestis, the cause of plague

2 .Yersinia pseudotuberculosis and

3 .Yersinia enterocolitica --- important causes

• of human diarrheal diseases

• others - nonpathogenic for humans

YERSINIA PESTIS & PLAGUEEtiology

A .Morphology & Identification

• Yersinia pestis is a gram-negative rod bipolar staining with special stains

• It is nonmotile

B. Culture

• It grows as a facultative anaerobe on many • bacteriologic media

• Growth is more rapid in media containing blood or tissue fluids and

• fastest at 30°C

• In cultures on blood agar at 37°C, • colonies may be very small at 24 hours

Yersinia PESTIS on blood agar

C. Antigenic Structure(1)All yersiniae - possess lipopolysaccharides

endotoxic activity

The three pathogenic species - produce antigens and toxins

that act as virulence factors.

(2) The virulent yersiniae produce V and W antigens,

which are encoded by genes on a plasmid. This is essential for virulence

(3)Yersinia pestis - additional plasmids, pPst – contains genes that yield

plasminogen-activating protease(Pla genes)

1 .temperature-dependent coagulase activity (20–28°C, the temp: of the flea) and

2 .fibrinolytic activity (35–37°C, the temp: of the host)For dissemination of the organism from

the flea bite injection site.

(4) The pFra/pMT plasmid

encodes the capsular protein (fraction F1) produced mainly at 37°C confers antiphagocytic properties

(5) The 3 pathogenic yersiniae have a pathogenecity island (PAI)

encodes for an iron-scavenging siderophore,

Yersiniabactin (Ybt siderophore)

• Y. pestis are serum resistance

• Produce several exotoxins ,

• one is lethal for mice; -adrenergic blockade and is cardiotoxic in animals,

• role in human infection is unknown

vIRulence Factors

Diagnostic Laboratory Tests

• Plague should be suspected in febrile patients who have been exposed to rodents in known endemic areas

• Rapid recognition and laboratory confirmation of the disease are essential in order to institute lifesaving therapy


• A. Specimens

1 .Blood(culture)2 .aspirates of enlarged lymph nodes (smear and

culture)3 .acute and convalescent sera for antibody levels4 .sputum for culture (pneumonia)5 .cerebrospinal fluid (in possible meningitis) for

(smear and culture)


• StainsI. Gram stain• small gram-negative bacilli appear in single

cells or as pairs or short chains 2. Wright's, Giemsa's, or Wayson's: Y pestis :

bipolar appearance (safety pin shape)3. More specific fluorescent antibody stains:

for the capsular F1 antigen

Wayson stain(Bipolar stain)

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Diagnostic Laboratory TestsB. Culture:

– All materials are cultured on – blood agar, chocolate, and – MacConkey agar plates and in brain-heart infusion

broth– Growth on solid media may be slow, requiring

more than 48 hours– but blood cultures are often positive in 24 hours– nonlactose-fermenting colonies on MacConkey

agar– it grows better at 28°C than at 37°C.

Yersinia pestis on chocolate agar

Yersinia pestis on blood agar

Yersinia pestis on MacConkey agar

Cefsulodin-Irgasan-Novobiocin (CIN) agar medium, for a72 hour time period, at a temperature of 37°C

• C. Identification

• identified by biochemical reactions

is catalase positiveindole, oxidase, urease negative nonmotile

• An organism with the above characteristics should be referred to a public health laboratory for more confirmatory testing

Definite identification of cultures

• is best done by immunofluorescence or by lysis by a specific Y pestis bacteriophage

• *All cultures are highly infectious and • must be handled with extreme caution inside

• a biological safety cabinet.

D. Serology

• In patients who have not been previously vaccinated

• a convalescent serum antibody titer of 1:16 or greater is presumptive evidence of Y pestisinfection

• A titer rise in two sequential specimens confirms the serologic diagnosis

The method of choice:

• An enzyme linked immunosorbent assay (ELISA) with FI antigen

• Polymerase chain reaction (PCR), with primers based on Fl gene sequences, offers a rapid and less hazardous than culture

Treatment

• Unless promptly treated plague may have a

mortality rate of nearly 50%pneumonic plague, nearly 100%

Treatment

• The drug of choice is streptomycin, but the more readily available aminoglycoside gentamicin has been shown to be as effective

• Doxycycline is an alternative drug and is sometimes given in combination with streptomycin.

• Drug resistance has been noted in Y pestis.

Epidemiology & Control

• Plague is an infection of wild rodents (field mice, gerbils, moles, skunks, and other animals)

• that occurs in many parts of the world

• The chief enzootic areas are India, Southeast Asia (especially Vietnam), Africa, and North and South America.

• The western states of the United States and Mexico always contain reservoirs of infection.


• Epizootics with high mortality rates occur • intermittently• • the infection can spread to domestic rodents (eg, rats) and other animals (eg, cats) and humans can be infected by flea bites or by

contact


• The commonest vector of plague is • the rat flea (Xenopsylla cheopis)

• but other fleas may also transmit the infection• Pneumonic plague can be transmitted directly

from person to person via• infected air droplets or through infected

clothing and other contaminated articles.

Oriental rat flea, Xenopsylla cheopis

Rat flea

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two forms of Y. pestis infection

1 .urban plague, for which rats are the natural reservoirs,

2. sylvatic plague, which causes infections in squirrels, rabbits,

field rats, and domestic cats

• Wild plague exists• in natural foci independent of human

populations and their activity.

• Domestic plague is intimately associated with rodents living with humans and can produce epidemics in both human and animal

• populations.

The infection cycle of Y. pestis

Ecology of plague - mild infection in most animals - frequently fatal in rats & humans

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The control of plague requires

1 .surveys of infected animals, vectors, and human contacts and

2 .by destruction of plague-infected animals

• If a human case is diagnosed health authorities must be notified

promptly

Rat Control

• Destruction of rat• Rat-proof building• Killing , trapping, fumigation

• Rat flee control • DDT


Epidemiology & Control• All patients with suspected plague should be

isolated • particularly if pulmonary involvement has not

been ruled out

• All specimens must be treated with extreme caution.

Epidemiology & Control• Contacts of patients with suspected plague

pneumonia

• should receive doxycycline, as chemoprophylaxis.• a 7- to 10-day course of antimicrobic therapy • regardless of vaccination history.

• Recommended antimicrobials include

• tetracyclines, chloramphenicol, or streptomycin


• Patients• Quarantine• Formalin-killed vaccine ( virulent strains of Y.

pestis ) • Haffkine vaccine can confer significant

protection against bubonic but • not pneumonic plague.

• Because of concern for bioterrorism, numerous vaccines are currently under

development.

• Primary Vaccination • given intramuscularly.

• Adults and children greater than or equal to 11 years old:

• 3 doses of vaccine. • The first dose, 1.0 ml, is followed by • the second dose, 0.2 ml, 4 weeks later. • The third dose, 0.2 ml, is administered 6 months

after the first dose.

I 2 3

4 weeks 6 months


• If an accelerated schedule is essential• 3 doses of 0.5 ml each• administered at least 1 week apart, may be

given• The efficacy of this schedule has not been

determined.

I 2 3

I week I week


• Booster Doses • When needed because of continuing

exposure, 3 booster doses should be given atapproximately 6-month intervals

• Thereafter, antibody levels decline slowly and booster doses at 1- to 2-year intervals, depending on the degree of continuing exposure, should provide good protection.

6mn 6 mn I yr I yr

• The following statement is true for Yersinia Pestis:

A .It exhibits striking bipolar staining with special stains.

B .It produces plasminogen activating protease for dissemination.

C .Its pathogenicity island encodes for siderophore and yersiniabactin.

D .Specimens include blood and aspirates of enlarged lymph nodes.

E .Can be prevented by vaccine.

• The following statement is true for Yersinia Pestis:

A .It exhibits striking bipolar staining with special stains.

B .It produces plasminogen activating protease for dissemination.

C .Its pathogenicity island encodes for siderophore and yersiniabactin.

D .Specimens include blood and aspirates of enlarged lymph nodes.

E .Can be prevented by vaccine.

PASTEURELLA

• are small, facultatively anaerobic, fermentative coccobacilli

• commonly found as commensals in the oropharynx of healthy animals

• Most human infections result from animal contact (e.g., animal bites, scratches, shared food)

• Pasteurella multocida • (the most common isolate) and • Pasteurella canis are human pathogens

• Three general forms of disease

(1) localized cellulitis and lymphadenitis • that occur after an animal bite or scratch

• P. multocida from contact with cats or dogs

• P. canis from dogs

(2) an exacerbation of chronic respiratory disease

• in patients with underlying pulmonary dysfunction

• presumably related to colonization of the patient's oropharynx

• followed by the aspiration of oral secretions

(3) Systemic infection in immunocompromised patients

• particularly those with underlying hepatic disease

Pandemics

• The first record of plague was an• outbreak among the Philistines in 1320 BC, described

in the Bible (I Samuel, V and VI).

• The first pandemic that we are certain of, known as Justinian=s plague, occurred between 542 AD and

• 546 AD, causing epidemics in Asia, Africa and Europe. It is estimated to have claimed nearly 100 million

• victims.

The second plague pandemic

• is the well-known "Black Death" of the fourteenth century (1347–1350).

• This pandemic was the beginning of a number of outbreaks of plague, which ravaged Europe and

• Africa in subsequent centuries.

The third pandemic

• began in Canton and Hong Kong in 1894 and spread rapidly throughout the world,

• by rats aboard the swifter steamships that replaced slow–moving sailing vessels in merchant fleets.

• Within 10 years (1894–1903) plague entered 77 ports on five continents. Plague became widespread in a number of countries.

• In India, there were over 6 million deaths from 1898 to 1908.3

• Myanmar and Viet Nam have reported cases of human plague virtually every year since 1954.

• Y. pestis can be divided into three biovars: Antiqua, Medievalis, and Orientalis.

• Significant rodent hosts include prairie dogs (Cynomys spp.), ground squirrels/ susliks (Spermophilus spp.), antelope ground squirrels (Ammospermophilus spp.), chipmunks (Tamias spp.), rats (Rattus spp.), wood rats (Neotoma spp.). mice (Peromyscusspp.), Siberian marmots (Marmota sibirica), voles (Microtus spp.), jerboas, and some gerbils (Rhombomys opimus and

• Dog and cat fleas (Ctenocephalides spp) can be infected, but are poor vectors compared to species such as X. cheopis.

• Human fleas (Pulex irritans) can also carry Y. pestis.

• Fleas are usually short-lived; however, some may survive for several months, or even a year or more, in rodent burrows after their host have died

Direct transmission

• can also occur between animals or people, but the importance of this route varies with the form of the disease.

• Y. pestis is present in tissues, draining lesionsand some body fluids, and these bacteria may enter the body through mucous membranes and broken skin.

Air-borne

• In humans, this occurs most readily in crowded, poorly ventilated conditions.

• Pnuemonic plague is most contagious duringits final stages, when the number of bacteria in the sputum increases.

• In the earlier stages, transmission does not seem to occur as readily.

Animals,

• including cats, can transmit bacteria in bites. • Carnivores and omnivores, including

humans, may also be infected by eating tissues from infected animals.

• In camels and other herbivores, this might occur when dead rodents or their excretions contaminate the animal's feed.

• At present, there is little information about the survival and growth

on fomites• Y. pestis can be transmitted on fomites at least

for short periods; however, its long-term survival in the environment, particularly in soil, is still poorly understood.

• This organism is not resistant to desiccation or heat, and on surfaces such as glass and steel, it usually persists for less than 72 hours.

• However, it is reported to survive for long periods of time in organic material;

• it may remain viable for up to 100 days in blood and for as long as 9 months in human bodies.

area

• Y. pestis can be found in parts of Africa, the Middle East, Asia, and North and South America, as well as Madagascar.

• The distribution of this organism is patchy. • In North America, Y. pestis occurs in the

western third of the continent, from British Columbia and Alberta, Canada to Mexico, and as far east as Dallas and the western borders of Kansas, Nebraska, Oklahoma and South

Disinfection

• Y. pestis is susceptible to a number of disinfectants including

• 1% sodium hypochlorite, • 70% ethanol, • 2% glutaraldehyde, • formaldehyde, and iodine–based and phenolic

disinfectants. • It can also be inactivated by moist heat (121° C

[250° F] for at least 15 minutes) or dry heat (160-170° C [320-338°F] for at least 1 hour).

Documents

YERSINIAE, PASTEURELLA€¦ · endotoxic activity The three pathogenic species - produce antigens and toxins that act as virulence factors. (2) The virulent yersiniae produce V and