GI INFECTIONS

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.


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.


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


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


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

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GI INFECTIONS