GI INFECTIONS
Brenda Beckett, PA-C
Clinical Medicine II
GI Infections
Gastroenteritis
Viral Hepatitis
Gastroenteritis
Diarrhea, vomiting, cramping– Increased fluid output, more than 4-5,
watery bowel movements per day Acute diarrhea – symptoms for less
than 2 weeks– Exception: C. diff sx can last longer
Pathophysiology
Viruses damage the small intestinal villi, decreasing intestinal surface area and unmasking ongoing fluid secretion by enteric crypts
Rotavirus produces an enterotoxin that induces secretion and contributes to the watery diarrhea
Pathophysiology
Invasive bacteria cause mucosal ulceration and abscess formation with an inflammatory response (WBCs in stool)
Bacterial toxins may influence enteric and extraenteric cellular processes (HUS, etc)
Other noninvasive bacteria and protozoa adhere to the gut wall, causing inflammation
Patient Evaluation Duration of symptoms Quantity (frequency of stools) Quality (watery) Fever Hematochezia – visible blood in stool S/S of dehydration Other sx: N/V, abd pain, tenesmus, anorexia Recent travel, recent abx use, hepatitis risk Other family members sick? Ability to take PO fluids
Physical Exam
Jaundice Hydration status – check for signs of
dehydration Stool Guaiac – occult blood Abdominal tenderness, bowel sounds Mental status
Oral Rehydration
Replace water, salt, sugars lost due to diarrhea, vomiting
In mildly dehydrated patient, it is first line therapy before IV rehydration.
Formulas are based on patient weight, degree of dehydration
75 ml/kg over 4 hrs every 2 min
Enteric Illness, categories
Non-specific gastroenteritis Gastroenteritis with bloody diarrhea Extraintestinal illness Non-infectious causes of GI symptoms
Nonspecific Gastroenteritis
Diarrhea without high fever or bloody stool
May have: cramps, low grade fever, headache, malaise, dehydration, N/V
Etiology: Viral (Norwalk-like viruses, Rotavirus), protozoal (giardia, crypto), foodborne toxins (S. aureus), traveller’s diarrhea, noninfectious causes.
Gastroenteritis with bloody diarrhea
Bloody stools with fever, +/- vomiting: Consider Salmonella, Shigella, Campylobacter (bacterial)
Bloody stools without fever: Could be above or E. coli 0157:H7.
GI illness with Extraintestinal Disease
Jaundice: Hepatitis A (we’ll get there in a little bit)
Meningitis: Listeria, salmonella Arthritis: Campylobacter, salmonella Flaccid paralysis and cranial
neuropathies: C. botulinum (Botulism) HUS: E. coli 0157:H7
Noninfectious causes of GI sx
Otitis media, Group A Streptococcal infection, irritable bowel syndrome, inflammatory colitis, stress, medications, gallbladder disease, peptic ulcer disease
Staphylococcal Food Toxin
S/S: Vomiting, severe cramping, low grade fever, diarrhea (no blood in stool)
Incubation: VERY short – 30 minutes to a few hours.
Complications: None, spontaneous recovery
Diagnosis: No specific test available. Clinical dx.
Staphylococcal Food Toxin
Treatment: Supportive – rest, hydration, compazine or other antiemetic for persistent vomiting
Origin: Toxin producing S. aureus strains, usually from human skin, inoculate food, multiply at room temp. Toxins not destroyed by reheating.
Other toxin producing bacteria: Clostridium perfringens, Bacillus cereus.
Staphylococcal Food Toxin
Prevention– Decrease food handling– Do not allow foods to sit at room temp. for
long periods– Glove use by food handlers– Exclude persons from food handling when
obvious skin infections are present.
Salmonella
Agent: Multiple subtypes of Salmonella species (S. enteritidis, S. typhimurium are most common)
Reservoir: Birds (chickens, turkeys), reptiles, others
Occurrence: Common Transmission: Undercooked meat/eggs, cross
contamination by meat juices, unpasteurized milk, handling reptiles
Salmonella
Incubation: 6-72 hours (usually 10-12) Diagnosis: Stool culture Clinical: Diarrhea, often bloody, fever,
cramps, vomiting Complications (elderly, immunocomp.):
Arthritis, meningitis, sepsis. Treatment: Usually supportive. Quinolones if
severe or if immunocompromised.
Campylobacter
Agent: C. jejuni Reservoir: Poultry, cattle, others Occurrence: Common Transmission: Undercooked poultry,
cross contamination, unpasteurized milk Incubation: 3-5 days Diagnosis: Stool culture
Campylobacter
Clinical: Diarrhea (often bloody), severe cramps, fever, +/- vomiting
Complications: Arthritis, cholecystitis Treatment: Quinolones or erythromycin Prevention: Adequate cooking, kitchen
hygiene, pasteurization
E. Coli 0157:H7
Agent: As above Reservoir: Cattle (and foods contaminated
with cow feces) Occurrence: Less common than Salmonella
and Campy, but increasing Transmission: Ingestion of undercooked beef,
cross contamination, unwashed contaminated fruits & veggies, person to person, water contamination. HIGHLY transmissible.
E. Coli 0157:H7
Incubation: 2-7 days Clinical: Watery diarrhea progressing to
bloody diarrhea after a few days. Fever usually absent. Cramps, vomiting.
Complications: 5-10% of kids younger than 5 will develop HUS, a life threatening multisystem disease. Can occur in adults.
E. Coli 0157:H7
Diagnosis: Stool culture, toxin assay Treatment: Supportive. Antibiotics
usually avoided (can increase HUS) Prevention: Thorough cooking of ground
beef, avoid cross contamination with beef juices, wash fruits/veggies, pasteurization. Early diagnosis will prevent person to person transmission.
Shigella
Agent: S. sonnei, S. flexneri, others Reservoir: Humans Transmission: Person to person,
foodborne, flies. Clinical: Fever, bloody diarrhea,
cramps, vomiting. Patients often appear toxic.
Diagnosis: Stool culture
Shigella
Complications: Sepsis, meningitis Treatment: Quinolones, hydration Communicability: Extremely high Prevention: Early diagnosis and
isolation, hand washing, food and water hygiene
Occurrence: Rare locally, high in third world countries.
Clostridium difficile
Most common antibiotic associated diarrhea- due to changes in colonic bacterial fermentation of carbohydrates
Colitis associated with toxin produced by C. diff.
Hospitalized, immunocompromised are most susceptible
Clostridium difficile
Antibiotics disrupt the normal flora, C. diff. flourishes (carried asymptomatically by 3-8% healthy adults). Any abx can trigger, but most common are: cephalosporins, penicillins, clindamycin, flouroquinolones
Sx start during or after abx therapy, may be delayed 8 weeks
Easily transmitted in hospital setting
Clostridium difficile
Toxins (A- enterotoxin & B-cytotoxin) have effect on colon- secretes fluid, develops pseudomembranes (discrete yellow-white plaques), easily dislodged.
Diagnosed by C. diff toxins in stool. EIA rapid toxin A & B.
Treat with Metronidazole 500 mg po tid x10-14 d. D/c other abx if possible.
Infection control measures to reduce spread in hospital settings.
Viral Gastroenteritis
Most common cause of infectious diarrhea in US
Infect epithelium of small intestine Diarrhea is watery WBC’s and visible blood are rare 4 categories: Rotavirus, Claicivirus
(norovirus), Astroviurs, Enteric Adenovirus.
Rotavirus
Most common cause of diarrhea in young children
Highly contagious: fecal-oral. Incubation 1-3 days, lasts 4-8 days Dehydration and hospitalization common in
young children Diagnose by EIA antigen in stool Treat with oral rehydration or IV Oral vaccine now available (controversial)
Calcivirus
Infect older children and adults Nonspecific, self-limiting Large water-borne and food-borne
outbreaks occur, fecal-oral Incubation 24-48 hrs, lasts 12-60 hrs No commercial tests to diagnose Treatment supportive (oral rehydration)
Giardiasis
Agent: Giardia lamblia Reservoir: Human and animal stool Occurrence: Very common Transmission: fecal-oral, contaminated
water or food Incubation: 3-10 days
Giardiasis
Clinical: Persistent or recurring diarrhea, bloating, cramps, steatorrhea (frothy fatty stool), weight loss. No blood in stool.
Diagnosis: Ova and parasite slide or direct antigen test.
Treatment: Metronidazole or other antiparasitic
Prevention: Water filtration, avoid drinking untreated surface water.
Traveler’s Diarrhea
Usually caused by endemic bacteria, not one specific agent. Most common is E. coli.
Usually benign, self-limiting Prophylactic abx for immunocomp. Treat with flouroquinolone if bloody
diarrhea and fever
Changing gears…
Hepatitis - Causes
Drugs: antihypertensives, statins, antibiotics, others.
Toxic agents: acetaminophen, alcohol, others.
Viruses: Hepatitis A (HAV), B (HBV), C (HCV) commonly. Uncommon: EBV, CMV, measles, rubella, etc.
Hepatitis – Clinical Presentation
Anorexia Malaise N/V Fever Enlarged, tender liver Jaundice Abnormal liver enzymes
Liver Function Tests
Serum Aminotransferases (ALT and AST). ALT usually >8x upper limit of normal
Serum and urine Bilirubin. (Neither sensitive nor specific for viral hepatitis)
Serum Alkaline Phosphatase Additionally: LDH, GGTP, Albumin,
Prothrombin Time
Lab and Physical Findings
In viral hepatitis ALT is usually higher than AST, as opposed to alcoholic hepatitis
Many people are entirely asymptomatic or mildly symptomatic with jaundice (especially HBV and HCV infections)
Children <6yrs with acute HAV infection are usually asymptomatic, rarely jaundiced
Table p 238-239 Wallach.
Acute Viral Hepatitis
Any combination of: malaise, fever, nausea, vomiting, abdominal pain or fullness, diarrhea, myalgias, headache.
Can have +/- jaundice, dark urine AND abrupt, dramatic elevation of
ALT/AST Hepatitis serologies to diagnose,
discussed in lab lecture.
Hepatits A
Most common cause of acute viral hepatitis Small RNA picornavirus About 30 day incubation Fecal-oral transmission Epidemics or sporadic cases Source: contaminated water, food (shellfish) No chronicity, no carrier state
Hepatitis A
Most children asymptomatic, most adults symptomatic
Low mortality Excreted in feces up to 2wks before
illness, rarely after first week of illness Only viral hepatitis causing spiking
fevers Viremia intermittent
Hepatitis A Vaccine
Available since the mid 1990’s Recommended for:
– children 12-23 months– International travelers– People who live or work where there are
outbreaks– Some other high risk groups
Hepatitis A Treatment
Symptomatic treatment (rest, fluids, etc) Avoid strenuous physical exertion,
alcohol and hepatotoxins
IG given to close contacts Vaccination of close contacts
Hepatitis B
Second most common cause of acute viral hepatitis
dsDNA Hepadnaviridae Most complex hepatitis virus Infective particle made up of viral core
plus an outer surface coat Transmission: sexual, parenteral,
perinatal
Hepatitis B
Can become chronic (5-10% of acute), may result in cirrhosis, hepatocellular ca
Often asymptomatic or nonspecific symptoms
Incubation 6-12 weeks If recover from HBV infection, will be
immune
Hepatitis B Vaccination
Available since the 1980’s Routine childhood vaccine (3 doses)
– Given at birth to babies of HBsAg pos mothers
Anti-HBs response Other high risk groups Post exposure prophylaxis: HBIG and
start vaccine
Hepatitis B Treatment
HBIG given within 7 days of exposure Initiation of HBV vaccine series
Symptomatic treatment (rest, fluids, etc) Avoid strenuous physical exertion,
alcohol and hepatotoxins
Hepatitis C
Single-stranded RNA flavivirus 6 major subtypes with varying genotypes Primarily transmitted by blood
– Injection drug use >50% of cases– Posttransfusion, hemodialysis, tattoos, body
piercing– Sexual and vertical transmission uncommon, but
increased risk with multiple sex partners.– HIV patients at increased risk
Hepatitis C
Incubation period: 6-7 weeks avg, ranges from 2-26 weeks
Clinical illness often mild, asymptomatic Chronicity common: >70%, may
progress to cirrhosis, carcinoma Leading cause of liver transplant No protective antibody response
Hepatitis C
Prolonged viremia Aminotransferases will be elevated off
and on (can have ALT >7x normal) Diagnose with Anti-HCV EIA
Hepatitis C Treatment
Interferon or peginterferon for 6-24 weeks decreases risk of chronicity
May reserve treatment for those that do not clear virus in 3-4 months (monitor HCV-RNA). Clearance more likely in symptomatic than asymptomatic pts.
Liver transplantation in acute liver failure
Hepatitis C
NO immunization No post exposure prophylaxis Chronicity common Different genotypes respond differently
to therapy
Other Hepatitis Viruses
Hepatitis D (Delta). – Due to ssRNA virus. – Always associated with Hepatitis B. – Acute or chronic. – Often severe, high mortality.
Hepatitis E. Due to ssRNA virus. – Rare, occurs in endemic areas.
Chronic Hepatitis
HBV – 5-10% of acute infections HCV - >70% of acute infections HDV – with HBV coinfection or
superinfection
Chronic Hepatitis
Elevated aminotransferases for more than 6 months
May lead to cirrhosis, hepatocellular carcinoma
Liver transplantation indicated for end-stage disease