Transcript daily ge

Gasrtointestinal bacterial infections
Gastroentritis
*Is the most common form of acute
gastrointestinal infection, causing diarrhea with
or without vomiting.
*Groups who are at risk of GE are children in
developing, elderly ,travellers to developing
countries , homosexual men ,and infants in day
care facicilities.
Mechanisms
Bacteria can cause diarrhea in three different
ways which are :
1.Mucosal adherence : this is by effacement of
intestinal mucosa and presented as moderate
watery diarrhea.Typical example is
Enteropathogenic E.coli (EPEC).
2.Mucosal invasion : by penetration and
destruction of mucosa and the typical clinical
presentaion is dysentry.Examples are Shigella
,Campylobacter , and Enteroinvasive E.coli
(EIEC).
3.Toxin production
*Enterotoxins : this occurs by fluid secretion
without mucosal damage with the resultant
profuse watery diarrhea.Examples are Vibrio
cholera ,Salmonella spp.,Campylobacter
spp.,Entertoxogenic E.coli (ETEC)
,Bacillus cereus ,Staphylococcus aureus
producing enterotoxin B,Clostridium
perfrigens type A.
*Cytotoxin : through damage to mucosa and
presented as dysentry.Typical examples are
Salmonella spp. ,Campylobacter spp., and
Enterohaemorrhagic E.coli (EHEC).
Clinical syndromes
Bacterial gastroentritis can bedivided on clinical
grounds into two broad syndromes :
1.Watery diarrhea ( usually due to enterotoxins,
or adherence ).
2.Dysentry ( usually due to mucosalinvasion and
damage ).
N.B…..some pathogens such as Campylobacter
jejuni there may be overlap between the two
syndromes.
Salmonella
Gastroentritis can be caused by many of the
numerous serotypes of salmonella ( all of which
are members of a single species ,
S.choleraesuis ), but the most commonly
implicated are S.enteritidis and
S.thyphimurium.These organisms , which are
found all over the world, are commensals in the
bowels of the livestock and they are
transmitted to man in contaminated foodstuffs.
*Salmonella can affect both large and small
bowel, and induce diarrhea both by production
of enterotoxins and by epithelial invasion.
*The typical symptoms commence abruptly 1248 hours after infection and consist of nausea
,cramping abdominal pain , diarrhea and
sometimes fever.
*The diarrhea can vary from profuse and watery
to a bloody dysentery syndrome.Spontaneous
resolution usually occurs in 3-6 daqys,
although the organism may persist in the
faecesfor several weeks.
*Bacteraemia occurs in 1-4% of cases and is
more common in elderly and the
immunosuppressed .Occasionally bacteraemia
is complicated by metastatic infection ,
especially atheroma on vascular
endothelium,with devastating consequences.
*In healthy adults salmonella gastroenteritis is
usually minor illness ,but young children and
the elderly are at risk of significant
dehydration.
.a
*Specific diagnosis is made by culturing of the
organism from blood or faeces , but
management is usually empirical. Antibiotic
therapy ( ciprofloxacin 500 mg twice daily )
may decrease the duration and severity of
symptoms , but is rarely warranted.
Campylobacter jejuni
*C.jejuni is also zoonotic infection , existing as a
bowel commensal in many species of
livestock.It is found world-wide , but is a
common cause of childhood gastroenteritis in
developing countries.Adults in these countries
may be tolerant of the organism , excreting it
asymptomatically.
*Like salmonella, campylobacter can affect large
and small bowel and can cause a wide variety
of symptoms.
*The incubation period is usually 2-4 days , after
which there is an abrupt onset of nausea ,
diarrhea and abdominal cramps.The diarrhea is
usually profuse and watery, but an invasive
haemorrhagic colitis is sometimes seen.
*Bacteraemia is very rare , and infection is
usually self – limiting in 3-5 days.Diagnosis is
made from stool cultures.If symptoms are
severe, azithromycin 500 mg daily is the drug
of choice.
Shigella
*Sigellae are enteroinvasive bacteria which cause
classical bacillary dysentery.The principal
species causing gastroenteritis are
S.dysenteriae ,S.flexeneri and S.sonnei
,which are found with varying prevalence in
different partes of the world.
*All cause a similar syndrome , as a result of
damage to intestinal mucosa.Some strains of
S.dysenteriae also secrete a cytotoxin affecting
vascular endothelium.
*Although shigellae are found world-wide ,
transmission is strongly associated with poor
hygiene.The organism is spread from person to
person , and only small numbers need to be
ingeste3d to cause illness (< 200, compared to
10 for campylobacter and >10 for salmonella).
*Symptoms start 24-48 hours after ingestion and
typically consist of frequent small-volume
stools containing blood and mucus.
*Dehydration is not as significant as in the
secretory diarrhoeas , but systemic symptoms
and intestinal complications are worse.
*The illness is usually self –limiting in 7-10 days,
but in children in developing countries the
mortality may be as high as 20%.
*Antibiotic treatment decreases the severity and
the duration of diarrhea , and possibly reduces
the risk of further transmission.
*Resistance to antibiotics is widespread
: in some areas amoxicillin or co-trimoxazole
may still be effective , but in many places
nalidixic acid or ciprofloxacin is needed.
Enterohaemorrhgic E.coli(EHEC)
EHEC(usually serotype O157:H7 ,and also
known as verotoxin- producing E.coli, or VTEC)
is a well recognized cause of gastroenteritis in
man.
*EHEC secrete a toxin (Shiga-like toxin 1) which
affects vascular endothelial cells in the gut and
in the kidney.
*After an incubation period of 12-48 hours it
causes diarrhea( frequently bloody) ,
associated with abdominal pain and nausea .
*Some days after the onset of symptoms the
patient may develop thrombotic
thrombocytopenic purpura (TTP) , or
haemolytic uremic syndrome (HUS).This is
more common in children , and may lead to
permanent renal damage or death.Treatment is
mainly supportive : there is evidence that
antibiotic therapy might precipitate HUS by
causing toxin release
Enterotoxigenic E.coli(ETEC)
*ETEC produce both heat-labile and heat-stable
enterotoxins which stimulate secretion of fluid
into the intestinal lumen.The result is watery
diarrhea of varying intensity , which usually
resolves within a few days.Transmission is
normally from person to person via
contaminated food.The organism is common in
developing countries , and is a major cause of
traveller ‘s diarrhea.
Vibrio
*Cholera, due to Vibrio cholera is the prototypic
pure enterotoxogenic diarrhea
*Vibrio parahaemolyticus causes acute watery
diarrhea after eating raw fish or shellfish that
has been kept for several hours without
refrigeration.Explosive diarrhea, abdominal
cramps and vomiting occur with a fever in
50%.It is a self-limiting , lasting up to 10 days.
Yersinosis
*Yersinia enterocolitica is a zoonosis of a variety
of domestic and wild mammals.Human disease
can arise either via contaminated food products
,e.g. pork , or from direct animal products.
*Yersinia enterocolitica can cause a range of
gastroenteric symptoms including watery
diarrhea , dysentery , and mesenteric
adenitis.The illness is usually self – limiting ,
but ciprofloxacin may shorten the duration.
Staphylococcus aureus
*Some strains of Staph. aureus can produce a
heat- stable toxin( enterotoxin B) which causes
massive se3cretion of fluid into intestinal
lumen.
*It is a common cause of food – borne
gastroenteritis, outbreaks usually occurring as
a result of poor food hygiene.
*Because the toxin is preformed in the
contaminated food, onset of symptoms is rapid
, often within 2-4 hours of consumption
There is violent vomiting , followed within hours
by profuse watery diarrhoea.The symptoms
have usually subsided within 24 hours .
Bacillus cereus
B.cereus produces two toxins .One produces
watery diarrhoea up to 12 hours after ingesting
the organism.The other toxin is preformed in
food and causes severe vomiting ,e.g ‘fried rice
poisoning’