Gastrointestinal infections
1
2 Introduction
Acute gastrointestinal illnesses rank second only to acute
upper respiratory illnesses as the most common diseases
worldwide
The incidence of diarrhea for all children under 5 years is
estimated to be 2.9 episodes per child per year
Younger children also have a higher risk of death from
acute dehydrating diarrhea, and diarrheal disease
3
Cont.
Gastroenteritis is an illness characterized by diarrhea which may
be accompanied by nausea, vomiting, fever, and abdominal pain.
Diarrhea is usually defined as a decrease in consistency of bowel
movements (i.e., unformed stool) and an increase of stools to ≥3
per day.
For best diagnosis and management, it is important to distinguish
secretory diarrhea that produces watery diarrhea from
inflammatory diarrhea.
inflammatory diarrhea caused by invasive pathogens, often
presents as fever, tenesmus, or bloody stool.
Watery vs. Inflammatory diarrhea
Watery Inflammatory
Percentage of patients 90 5–10
Stools
Appearance Watery Bloody
Volume Increased: ++/+++ Increased: +/++
Number per day <10 >10
pH 5.0–7.5 6.0–7.5
Occult blood Negative Positive
Fecal PMN cells Absent or few Many
Watery vs. Inflammatory
Watery Inflammatory
Mechanisms Production of toxins Mucosal invasion
Complications
Dehydration Could be severe Mild
Others Acidosis, shock, Tenesmus, rectal pro-
electrolyte imbalance lapse, seizures
Watery Inflammatory
Etiology Vibrio cholerae Shigella
Enterotoxigenic Escherichia coli Salmonella
(ETEC)
Enteropathogenic E. coli (EPEC) Campylobacter
Rotaviruses Yersinia
Noroviruses Enterohemorrhagic E. coli
(EHEC)
Enteroinvasive E. coli (EIEC)
Enteroaggregative E. coli (EAEC)
Cytotoxigenic C. difficile
7 Bacillary Dysentery (Shigellosis)
The shigellae are gram-negative bacilli belonging to the
family Enterobacteriaceae.
usually affects children 6 months to 10 yrs of age.
more common in daycare centers and in areas with crowded
living conditions or poor sanitation
transmitted through the fecal–oral route
the bacteria multiply and spread within the submucosa of
the small bowel
8 Pathogenesis
Infection with Shigella occurs after ingestion of as few as 10 to 100
organisms
Shigella strains invade intestinal epithelial cells, with subsequent
multiplication, inflammation, and destruction.
This organism only rarely invades the bloodstream;
But bacteremia may occur in malnourished children and in
immunocompromised patient
Symptoms develop in about 3 days (range, 1–7) after contracting the
bacteria.
9 Clinical presentation and Diagnosis
Early—high fever, bloody diarrhea
Later— colitis develops with urgency, tenesmus, and
dysentery, low-grade fever, vomiting
Diagnosis
Stool examination (show leukocytosis, RBC)
10
Cont.
v Complication
proctitis (infant and young children)
intestinal obstruction
colonic perforation
bacteremia
metabolic disturbance
11 Treatment
Infection with shigella is generally self-limited but
antibiotic therapy is indicated to shorten duration of illness
and to reduces the risk of transmission
First-line drug: is ciprofloxacin
Children : Ceftriaxone/Azithromycin
Duration of treatment: five days
12 Salmonellosis
Salmonella enterica are gram-negative bacilli belonging
to the family Enterobacteriaceae
Non-typhoidal Salmonella (NTS) are important causes
of food-borne infection.
13 Cont.
Risk factors
P extremes of age
P alteration of endogenous GI flora due to ab use
P acid suppressive therapy
P diabetes , malignancy, HIV
P immune suppressive therapy
14 Pathogenesis
The inoculum necessary for clinical illness is estimated to be
106 organisms
Once ingested and successfully beyond host defense
mechanisms organisms can attach and invade the distal
ileum and proximal colon.
Gastroenteritis often is characterized by massive neutrophil
infiltration followed by lymphocytes and macrophages
15 Cont.
Release of toxic substances by neutrophils may contribute
to inflammation and result in:
Ø tissue damage,
Ø fluid secretion, or
Ø leakage across the intestinal mucosa
16 Clinical presentation
Most patients experience symptoms within 48 hours of ingestion of
contaminated food or water.
Patients often complain of nausea and vomiting followed by
abdominal cramps, headache, fever, and diarrhea
bacteremia is the most common complication of gastroenteritis.
High-risk patients include
Infants,
Elderly, and
Patients with immunosuppression
17 Treatment
Salmonella gastroenteritis is usually self-limited,
fluid and electrolyte replacement is the primary
mode of treatment
most patients respond well to ORT
18
Cont.
Antibiotic therapy
used in high-risk patients
neonates or infants
persons older than age 50 years
immunodeficiency
Ciprofloxacin for 5–7 days is recommended.
Alternatives: azithromycin, Cotrimoxazole
19
Campylobacteriosis
Campylobacter jejuni is the most commonly identified
cause of bacterial diarrhea worldwide.
is primarily a pediatric disease
20
Cont.
Risk factors
P contaminated foods of animal origin
P unpasteurized milk
P contaminated water
P contact with farm animals and pets
P use of antimicrobial therapy
P foreign travel
P poor sanitation
21 Pathophysiology
P Campylobacter spp. are gram-negative bacilli
P are sensitive to stomach acidity; as a result, diseases or
medications that buffer gastric acidity may increase the
risk of infection
P after an incubation period, infection is established in the
jejunum, ileum, colon, and rectum
22
Clinical presentation
Incubation period of 1 to 7 days.
fever, headache, and myalgias is followed by crampy
abdominal pain, and several bowel movements
Abdominal pain is more prevalent in Campylobacter
infection than shigella/salmonella
Tenesmus occurs in approximately 25% of patients.
Diagnosis of Campylobacter is established by stool culture.
23 Treatment
Fluid replacement is the cornerstone of therapy
Antibiotic therapy should be considered in patients with
high fevers, bloody stools, symptoms lasting longer
than 1 week, pregnancy,
Immunocompromising conditions
24
Cont.
First line: Macrolides
Alternative: fluoroquinolone
N:B antimotility agents should be avoided
Prolong the duration of symptoms and associated with
worse outcomes
25 Escherichia Coli
Diarrheagenic E. coli is differentiated into several distinct
categories based on pathogenic features of diarrheal disease:
Enterotoxigenic E. coli (ETEC)
Enteropathogenic E. coli (EPEC)
Enteroinvasive E. coli (EIEC)
Enteroaggregative E. coli (EAEC)
Enterohemorrhagic E. coli (EHEC)
26 Cont.
The most common diarrheagenic E. coli infection is
caused by ETEC manifested by watery (enterotoxigenic)
diarrhea.
Dysentery is caused by EHEC.
Infections with EIEC and EPEC are primarily a disease of
children in developing countries.
EAEC strains are implicated in persistent diarrhea ( ≥14
days) in HIV-infected patients.
27
Pathogenesis
Enterotoxigenic E. coli are capable of producing
enterotoxins
luminal accumulation of electrolytes that draws water into
the intestine, and production of a cholera-like secretory
diarrhea
EHEC is able to produce shiga-like toxins
the cytotoxic effect of shiga-like toxins disrupts the mucosal
integrity of the large intestine, causing diarrhea
28 Clinical presentation
ETEC:
watery stools, nausea and abdominal cramp
abrupt in onset and resolves within 24 to 48 hours without complication
EHEC:
as many as 12 bloody stools per day
cramping abdominal pain, abdominal distension
nausea occurs in about two-thirds of patients, and vomiting occurs in
less than half.
the white blood cell count is elevated and accompanied by a left shift
29 Cont.
EPEC
Acute onset of profuse watery diarrhea, vomiting, and
low-grade fever.
EAEC
Persistent, watery, mucoid, secretory diarrhea with low-
grade fever
EIEC
Presents most commonly as watery diarrhea
30 Treatment
Prevent dehydration by correcting fluid and electrolyte
imbalances.
ETEC: antibiotics are rarely needed except in severe cases.
Recommended antibiotics include TMP-SMX and
quinolones
31 Cont.
EHEC: the only recommended treatment is supportive,
including fluid and electrolyte replacement
antibiotics are CI because they can induce the
expression and release of toxin.
antimotility agents should be avoided because they
delay clearance of the pathogen and toxin,
32 Cholera (Vibrio Cholerae)
is caused by the bacterium vibrio cholerae that leads to a
massive loss of fluid loss
results in life-threatening dehydration
cholera can be transmitted by contaminated water or food
A relatively large inoculum of 10 3 to 10 6 organisms is
required for infection if water is the vehicle, and 102 to 104
if the vehicle is food.
33 Pathophysiology
vibrios cholerae is a gram-negative bacillus
pathology of cholera results from an enterotoxin (cholera
toxin) produced by the bacteria
vibrios pass through the stomach to colonize the upper small
intestine.
They possess filamentous protein extensions that attach to
receptors on the intestinal mucosa, and
their motility assists with penetration of the mucus layer
34 Cont.
The enterotoxin causes an increase in cyclic adenosine
monophosphate (cAMP), and results in inhibition of sodium
and chloride absorption by microvilli
The net effect of the cholera toxin is isotonic fluid secretion
by SI that exceeds the absorptive capacity of duodenum
This results in the production of watery diarrhea with
electrolyte concentrations similar to that of plasma.
35 Clinical presentation
Diarrhea:
patients may lose up to 1 L of isotonic fluid
every hour
the onset of diarrhea is abrupt
is followed rapidly or sometimes preceded by
vomiting
36 Cont.
Fever: < 5% of patients
Abdominal distension and ileus
Laboratory abnormalities: increased RBC volume and
total protein, magnesium, and calcium levels
37 Complication
Hypoglycemia
Seizures
Fever
Mental alterations
Metabolic acidosis
Prerenal azotemia
Aspiration pneumonia
38 Treatment
Goals of therapy
rapid restoration of fluid losses,
correction of metabolic acidosis, and
replacement of potassium deficiency
39
Cont.
Rehydration
Mild cases:
ORS; for children: < 2yrs: 50 – 100ml; 2-10yrs: 100
– 200ml after each loose stool.
For severe cases: Ringer lactate/NS 50-100ml/min until
shock is reversed;
40 Cont.
Antibiotics are not necessary in most cholera cases
However, in severe cases, antibiotics shorten the duration of diarrhea,
decrease fluid loss, and shorten the duration of the carrier state.
A single dose of
Doxycycline
Ciprofloxacin
Erythromycin/azithromycin
Cotrimoxazole
41 Prevention
ensuring a safe water supply
safe food preparation,
improving sanitation, and
patient education
Vaccination
In high-risk groups, such as children and patients
infected with HIV, in countries where the disease is
endemic.
42 Clostridium difficile infection
C. difficile is the primary cause of hospital-acquired
infectious diarrhea in hospitalized patients, including
children
C. difficile, a gram-positive, spore-forming anaerobe, is
spread by the fecal–oral route
43 Pathophysiology
the organism is ingested either as the vegetative form or
spores, which can survive for long periods
once the GI tract is colonized with spores, disruption of the
gut flora, which occurs with antibiotic therapy, allows C.
difficile to proliferate.
toxin production is responsible for the inflammation, fluid
and mucus secretion and mucosal damage
44
Risk factors
Common risk factors include
increasing age
severe underlying illness
ICU admission
gastric acid suppression
exposure to broad spectrum antimicrobials
45
Clinical presentation
Symptoms can start as first day of antibiotic therapy or
several weeks after antibiotic therapy is completed
Colitis
p r o f u s e , w a t e r y d i a r r h e a , a b d o m i n a l p a i n ,
abdominal distention, nausea, and anorexia
left or right lower quadrant abdominal pain
46
Cont.
toxic megacolon: suggested by acute dilation of the
colon to a diameter greater than 6 cm
fulminant colitis: Acute abdomen and systemic
symptoms such as fever, tachycardia, dehydration, and
hypotension
47 Treatment
Patients who develop CDI while receiving an antibiotic
should have the antibiotic discontinued, if possible or
switch to an agent with a lower risk of CDI.
48
Cont.
First line
mild- moderate disease
Metronidazole(500 mg orally TID 7–14 days; or,30 mg/kg/day
divided q 6 hr for children)
Severe disease (WBC greater than 15,000 cells/mm3)
oral vancomycin (125 mg qid for 7-14 days or, 40-50
mg/kg/day divided q 6hr for children)
use of antimotility agents should be avoided since they may
precipitate toxic megacolon.
49
Viral gastroenteritis
Viruses are the most common cause of diarrheal illness in
the world
Many viruses may cause gastroenteritis, including
rotaviruses, noroviruses, astroviruses, enteric adenoviruses,
and coronaviruses
50
Agents Responsible for Acute Viral Gastroenteritis and Diarrhea
Virus Peak age Transmission Symptoms
Rotavirus 6month -2 Fecal–oral, water, Diarrhea, vomiting, fever,
years food abdominal pain
Adenovirus <2 years Fecal–oral Diarrhea, respiratory symptoms,
vomiting, fever
Astrovirus < 7 years Fecal–oral, water Vomiting, diarrhea, fever,
abdominal pain
Noroviruses > 5 years Fecal–oral, food Nausea, vomiting, diarrhea,
abdominal cramps, headache,
fever, chills, myalgia
51
Cont.
Rotavirus
is a double-stranded, RNA virus accounts for the most
common cause of infectious diarrhea in children
The cornerstone of rotavirus treatment is supportive
care and rehydration with ORT or IV fluids.
IV hydration in case of shock, severe emesis, and
high stool output (>10 mL/kg/hr).
52
Cont.
antimotility agents should be avoided
zinc supplementation: shorten the duration and
frequency of diarrhea
Dose: ≤6 month 10mg/d for 10 days
> 6 month 20mg/d for 10 days
53 Prevention
Promotion of exclusive breast-feeding (prevent through
promotion of passive immunity)
Improved complementary feeding practices
malnutrition is an independent risk for the frequency and
severity of diarrheal illness
Improved water and sanitary facilities
Promotion of personal and domestic hygiene
Rotavirus immunization
