Dr.T.V.Rao.MD

E. COLI 0104:H4

EMERGING PATHOGEN – NEW CONCERNS

DR.T.V.RAO MD 1

• Shiga toxin-producing

Escherichia coli (STEC) can

cause severe enteric infections

and the potentially life

threatening hemolytic uremic

syndrome (HUS). Prompt

diagnosis of these infections is

important to implement early

clinical management that

minimizes the likelihood of

developing HUS, to reduce the

risk of transmitting the infection

to others, and to detect outbreak

• Commonly consumed vegetables

are source of spread.

SHIGA TOXIN-PRODUCING ESCHERICHIA COLI (STEC)

CURRENT OUTBREAK

DR.T.V.RAO MD 2

DR.T.V.RAO MD 3

• Large outbreak of Shiga toxin-

producing Escherichia coli O104:H4

(STEC O104:H4) infections ongoing

in Germany. The responsible strain

shares virulence characteristics with

enter aggregative E. coli (EAEC). As

of June 2, 2011, case counts

confirmed by Germany’s Robert

Koch Institute* include 520 patients

with hemolytic uremic syndrome

(HUS) – a type of kidney failure that

is associated with E. coli or STEC

infections – and deaths.

NEW REPORT ON E.COLI 0104 H4 OUTBREAK

DR.T.V.RAO MD 4

• Disease Prevention

and Control (ECDC)

said the "causative

agent" was a strain

of bacteria that are

called Shiga toxin-

producing

Escherichia coli, or

STEC.

EUROPEAN CENTRE FOR DISEASE PREVENTION

AND CONTROL (ECDC)

REPORTS

DR.T.V.RAO MD 5

• While suspicion has fallen on raw

tomatoes, cucumbers and lettuce

as the source of the germ,

researchers have been unable to

pinpoint the food responsible.

The outbreak is considered the

third-largest involving E. coli in

recent world history, and it is

already the deadliest. Twelve

people died in a 1996 Japanese

outbreak that reportedly sickened

more than 9,000, and seven died

in a Canadian outbreak in 2000.

VEGETABLES AS SOURCE OF

E.COLI INFECTIONS

DR.T.V.RAO MD 6

CYCLE OF EVENTS IN SPREAD OF STEC

RUMINANTS AND CONTAMINATION CYCLE

DR.T.V.RAO MD 7

CYCLE OF EVENTS IN SPREAD OF STEC

STEC RUMINANTS AND CONTAMINATION CYCLE

DR.T.V.RAO MD 8

• E-coli isn’t usually disease- causing, a major commensal in humans.

• Shiga toxin is one of the most potent toxins known to man, so much so that the Centers for Disease Control and Prevention lists it as a potential bioterrorist agent

• Most kinds of E. coli bacteria do not cause disease in humans, indeed, some are beneficial, and some cause infections other than gastrointestinal infections, such urinary tract infections.

SHIGA TOXINS

DR.T.V.RAO MD 9

• Some kinds of E. coli cause disease

by making a toxin called Shiga toxin.

The bacteria that make these toxins

are called ―Shiga toxin-producing‖ E.

coli, or STEC for short. You might hear

them called Vero cytotoxic E. coli

(VTEC) or Enterohemorrhagic E. coli

(EHEC); these all refer generally to the

same group of bacteria. The most

commonly identified STEC in North

America is E. coli O157:H7 (often

shortened to E. coli O157 or even just

―O157‖). When you hear news reports

about outbreaks of ―E. coli‖ infections,

they are usually talking about E. coli

O157.

WHAT ARE SHIGA TOXIN-PRODUCING E. COLI?

DR.T.V.RAO MD 10

• E. coli serotype O157:H7 is a rare

variety of E. coli that produces

toxins which are capable of inflicting

damage to the lining of the intestine.

These toxins are closely related or

identical to the toxin produced by

Shigella dysenteriae and are

referred to as Shiga toxins. In very

rare instances, the infection can

progress to hemolytic uremic

syndrome ("HUS") and kidney

failure. E. coli O157:H7 can survive

at low temperatures as well as under

acidic conditions, and the infectious

dose is relatively small.

E.COLI 0104: H4 RESEMBLES E. COLI SEROTYPE O157:H7

DR.T.V.RAO MD 11

• t's observed that E. coli O104:H4

has picked up some new genes,

almost certainly through horizontal

gene transfer, in which stretches of

DNA are picked up from other E. coli

strains, or possibly different species

entirely. Once incorporated into the

genome, the new genes can provide

the bacteria with entirely novel

properties. In the case of E. coli

O104:H4, tests have shown that it

now carries a gene for shigatoxin,

which is commonly found in other

disease-causing strains of this

species.

E.COLI 0104;H4 PICKED UP NEW

GENES

DR.T.V.RAO MD 12

• The toxins produced by STEC

were named based on their

similarity in structure and

function to Shiga toxins produced

by Shigella dystenteriae type .

Shiga toxin 1 (Stx1) is

neutralized by antibodies

against Shiga toxin, whereas

Shiga toxin 2 (Stx2) is not

neutralized by antibodies against

Shiga toxin but is neutralized by

homologous antibodies

STRUCTURE OF STEC

DR.T.V.RAO MD 13

• Strain appeared "to be a

hybrid of two different

E. coli types.

• The hybrid strain also

contains the Shiga-like

toxin from

Enterohaemorrhagic E.coli,

This toxin binds to and

damages kidney cells and

can lead to potentially fatal

HUS.

THE NEW STRAIN OF E.COLI 0104 H4

A HYBRID STRAIN

DR.T.V.RAO MD 14

GENOME OF A KILLER: GERMAN AND CHINESE SCIENTISTS

CRACKED THE GENETIC CODE BEHIND THE STRAIN OF

ESCHERICHIA COLI

DR.T.V.RAO MD 15

• STEC are also

referred to as

verocytotoxigenic E.

coli; STEC that

cause human illness

are also referred to

as Enterohemorrhagic

E. coli.

STEC ARE REFERRED AS VEROCYTOTOXINS

DR.T.V.RAO MD 16

• Symptoms of STEC infection

include severe stomach cramps,

diarrhea (which is often bloody),

and vomiting. If there is fever, it

usually is not very high. Most

people get better within 5–7

days, but some patients go on to

develop HUS—usually about a

week after the diarrhea starts.

Symptoms of HUS include

decreased frequency of

urination, feeling very tired, and

losing pink color to skin and

membranes due to anemia.

HOW THE PATIENTS PRESENT

DR.T.V.RAO MD 17

• Around 5–10% of those who are

diagnosed with STEC infection

develop a potentially life-

threatening complication known

as hemolytic uremic syndrome

(HUS). Clues that a person is

developing HUS include

decreased frequency of urination,

feeling very tired, and Persons

with HUS should be hospitalized

because their kidneys may stop

working and they may develop

other serious problems. Most

persons with HUS recover within

a few weeks, but some suffer

permanent damage or die.

HEMOLYTIC UREMIC SYNDROME (HUS)

DR.T.V.RAO MD 18

DR.T.V.RAO MD 19

• Early diagnosis of

STEC infection is

important for

determining the proper

treatment promptly.

Initiation of parenteral

volume expansion early

in the course of O157

STEC infection might

decrease renal damage

and improve patient

outcome

NEED FOR EARLY DIAGNOSIS –

REDUCES RENAL DAMAGE

DR.T.V.RAO MD 20

PROMPT LABORATORY DIAGNOSIS

• Prompt laboratory diagnosis of STEC infection

facilitates rapid subtyping of STEC isolates by public

health laboratories and submission of PFGE patterns to

PulseNet, the national molecular subtyping network for

foodborne disease surveillance . Rapid laboratory

diagnosis and subtyping of STEC isolates leads to

prompt detection of outbreaks, timely public health

actions, and detection of emerging STEC strains.

DR.T.V.RAO MD 21

• As a major outbreak

of a highly toxic

strain of E. coli

bacteria continues

to sicken residents

of Europe, medical

experts are racing to

find the source

SAMPLES ARE TAKEN FROM A CUCUMBER

FOR A MOLECULAR BIOLOGICAL STUDY

DR.T.V.RAO MD 22

• Specimens should be sent to the

laboratory as soon as possible

for O157 or 0104 STEC culture

and Shiga toxin testing. Ideally,

specimens should be processed

as soon as they are received by

the laboratory. Specimens that

are not processed immediately

should be refrigerated until

tested; if possible, they should

not be held for >24 hours

unpreserved or for >48 hours in

transport medium.

EARLY PROCESSING OF RESULTS – YIELDS

BETTER RESULTS.

DR.T.V.RAO MD 23

STEC INFECTIONS DIAGNOSED WITH..

• STEC infections are usually diagnosed through

laboratory testing of stool specimens (feces).

Identifying the specific strain of STEC is essential for

public health purposes, such as finding outbreak. Slabs

that test for the presence of Shiga toxins in stool can

detect non-O157 STEC infections. However, for the

O group (Serogroup) and other characteristics of non-

O157 STEC to be identified. Shiga toxin-positive

specimens must be sent to a Reference laboraoreis in

doubtful cases of 0104 serotypes

DR.T.V.RAO MD 24

• To isolate O157 STEC,

a stool specimen

should be plated onto a

selective and

differential medium

such as sorbitol-

MacConkey agar

(SMAC) , cefixime

tellurite-sorbitol

MacConkey agar (CT-

SMAC), or

CHROMagar O157.

0157AND 0104 CAN BE ISOLATED ON

SELECTIVE MEDIUM

DR.T.V.RAO MD 25

• O157 and 0104 STEC

can usually be easily

distinguished from most

E. coli that are

members of the normal

intestinal flora by their

inability to ferment

sorbitol within 24

hours on sorbitol-

containing agar

isolation media

CULTURE FOR STEC

DR.T.V.RAO MD 26

• Rapid and reliable detection of the

enterohaemorrhagic E.coli O157. Easily

distinguishable colonies due to the purple

colouring they have aquired. Most other

bacterial species are inhibited, giving

blue or colourles colonies. Despite

specifity is improved in comparison to

Sorbitol MacConkey Agar, when direct

isolation method is used, the false

positive must be screened out by

additional tests and candidates must be

further studied for confirmation.

• . E.coli O157 - purple

• other bacterial colonies - inhibited, blue or colourles

CHROMAGAR FOR E.COLI O157

DR.T.V.RAO MD 27

• After incubation for 16–

24 hours at 37°C

(99°F), the plate should

be examined for

possible O157 colonies,

which are colorless on

SMAC or CT-SMAC

and are mauve or pink

on CHROMagar O157

COLONIES APPEAR AS PINK ON

CHROMAGAR

DR.T.V.RAO MD 28

• To identify O157 STEC, a portion of a well-isolated colony (i.e., a distinct, single colony) should be selected from the culture plate and tested in O157-specific antiserum or O157 latex reagent as recommended by the manufacturer . Colonies that agglutinate with one of the O157-specific reagents and do not agglutinate with normal serum or control latex reagent are presumed to be O157 STEC. At least three colonies should be screened (CDC, unpublished data, 2009). If O157 STEC bacteria are identified in any one of the three colonies, no additional colonies need to be tested

IDENTIFICATION OF 0157 LATEX AGGLUTINATION TEST

DR.T.V.RAO MD 29

• The colony in which

O157 STEC are

detected should be

streaked onto SMAC or

a nonselective agar

medium such as tryptic

soy agar (TSA), heart

infusion agar (HIA), or

blood agar and

biochemically confirmed

to be E. coli

IDENTIFICATION WITH BIOCHEMICAL

METHODS

DR.T.V.RAO MD 30

• PCR assays to detect the stx1 and stx2 genes are used by many public health laboratories for diagnosis and confirmation of STEC infection. Depending on the primers used, these assays can

distinguish between stx1 and stx2 Assays also have been developed that determine the specific O group of an organism, detect virulence factors such as intimin and enterohemolysin and can differentiate among the subtypes of Shiga toxins

PCR ASSAYS CAN DETECT GENETIC

BASIS OF STEC

DR.T.V.RAO MD 31

• The new isolates of E.coli 0104 : H4 are emerging pathogens with a potential to cause morbidity and mortality with community concern,

• The search is for the fool proof method for isolation and identification of the Bacteria

NEED FOR FOOLPROOF METHODS IN

DIAGNOSIS

DR.T.V.RAO MD 32

• Non-specific supportive

therapy, including

hydration, is important.

Antibiotics should not be

used to treat this

infection. There is no

evidence that treatment

with antibiotics is helpful,

and taking antibiotics may

increase the risk of HUS.

Antidiarrheal agents like

Imodium® may also

increase that risk.

SUPPORTIVE TREATMENT

DR.T.V.RAO MD 33

HOW CAN STEC INFECTIONS BE

PREVENTED?

DR.T.V.RAO MD 34

• WASH HANDS thoroughly after using the

bathroom or changing

diapers and before

preparing or eating food.

WASH YOUR HANDS

after contact with animals

or their environments (at

farms, petting zoos, fairs,

even your own backyard).

HANDING WASHING THE MOST ESSENTIAL

STEP

DR.T.V.RAO MD 35

• COOK meats thoroughly.

Ground beef and meat that

has been needle-

tenderized should be

cooked to a temperature of

at least 160°F/70˚C. It’s

best to use a thermometer,

as color is not a very

reliable indicator of

―doneness.‖

PROPER COOKING MOST ESSENTIAL STEP

DR.T.V.RAO MD 36

• AVOID raw milk, unpasteurized dairy products, and unpasteurized juices (like fresh apple cider).

• AVOID swallowing water when swimming or playing in lakes, ponds, streams, swimming pools, and backyard ―kiddie‖ pools.

AVOID

DR.T.V.RAO MD 37

• PREVENT cross

contamination in food

preparation areas by

thoroughly washing

hands, counters, cutting

boards, and utensils

after they touch raw

meat.

NEED FOR PREVENTION

DR.T.V.RAO MD 38

• Antibiotics might increase the risk for HUS in patients infected with O157 STEC, and antidiarrheal medications might worsen the illness.

• True with 0104:H4

ROLE OF ANTIBIOTICS – CAN THEY HARM ?

DR.T.V.RAO MD 39

• Delayed diagnosis of STEC

infections might lead to

secondary transmission in

homes, child-care

settings, nursing homes,

and food service

establishments and might

delay detection of

multistate outbreaks related

to widely distributed foods .

Outbreaks caused by STEC

with multiple Serogroups

or PFGE patterns have

been documented.

DELAYED DIAGNOSIS LEADS TO

OUTBREAKS

DR.T.V.RAO MD 40

• The World Health

Organization is warning

people not to take

antibiotics if they get sick in

the E. coli outbreak that

began in Germany last

month.

• Anti-diarrhea medication

isn't recommended either,

as it stops the bacteria from

quickly leaving the body.

WHO ADVISES

DR.T.V.RAO MD 41

• Use of antibiotics other

Antidiarrheal treatments "can

actually make the situation

worse." That's because killing

toxin-producing bacteria, such as

the ones responsible for this

outbreak, can actually cause

them to release more toxins. can

actually make the situation

worse." That's because killing

toxin-producing bacteria, such as

the ones responsible for this

outbreak, can actually cause

them to release more toxins.

WHY DRUGS ARE DANGEROUS

DR.T.V.RAO MD 42

VEGETABLES TOO ARE INFECTIOUS

DO BELIEVE IT ???

DR.T.V.RAO MD 43

DR.T.V.RAO MD 44

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INFECTIOUS DISEASES AND MICROBIOLOGY ..

DR.T.V.RAO MD 45

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