Some Foodborne Illness Agents 
Characteristics and Confirmation

Copyright 2000

O. Peter Snyder, Jr., Ph.D.

Hospitality Institute of Technology and Management

Agent or Cause of

Illness or Disease

Incubation Period, Symptoms, Duration

Confirmation Tests

Staphylococcus aureus

Onset: 2 to 7 hours

Symptoms: Nausea, vomiting, retching, abdominal pain, diarrhea, prostration

Duration:1 to 3 day

Food:Isolation of S. aureus toxin in food.

-Ion exchange resins
-Rapid methods based on monoclonal antibodies (e.g., ELISA, Reverse passive latex agglutination).
Bacillus cereus (emetic)
Onset: 1/2 to 6 hours

Symptoms: Nausea, vomiting, occasionally diarrhea.(May resemble S. aureus intoxication.)

Duration:Generally less than 1 day

1) Isolation of strains of the same serotype from suspect food and feces or vomitus of patient(s).

2) Isolation of large numbers of a B. cereus serotype known to cause foodborne illness from the suspect food or from the feces or vomitus of patient(s).

3) Isolation of B. cereus from suspect foods and determination of their enterotoxigenicity by serological (diarrheal toxin) or biological (diarrheal and emetic) tests.

Bacillus cereus (diarrheal)

Onset: 6 to 15 hours

Symptoms: Abdominal pain, nausea, watery diarrhea. (Simulates C. perfringens gastroenteritis).

Duration:24 hours

(See above.)
Clostridium perfringens
Onset: 8 to 22 hours

Symptoms: Abdominal pain, watery diarrhea.

Duration:24 hours (Less severe illness symptoms can persist in some individuals for 1 or 2 weeks.)

Diagnosis confirmed by detection of toxin in feces of patients.

Bacteriological confirmation can also be done by finding large numbers of the causative bacteria in implicated foods and/or in the feces of patients. 

Campylobacter jejuni
Onset: 2 to 5 days

Symptoms: Abdominal pain, diarrhea (may contain occult blood), headache, fever, nausea, feeling of ill health, loss of appetite, muscle pain.

Duration:7 to 10 days (Relapse occurs in about 25% of cases.)

C. jejuni is usually present in high numbers in the diarrheal stools of individuals.Isolation requires special antibiotic-containing media and a special microaerophilic atmosphere (5% oxygen).[Most clinical laboratories are equipped to isolate C. jejuni.]
Salmonella spp.
Onset: 2 to 5 days

Symptoms: Abdominal pain, diarrhea, nausea, vomiting, chills, fever, headache, feeling of ill health, loss of appetite.
Chronic consequences: arthritic symptoms may follow 3 to 4 weeks after onset of acute symptoms, 

Duration:Acute symptoms may last for 1 to 2 days, or may be prolonged, depending on host factors, ingested dose, and strain.

Diagnosis of human illness:serological identification of culture isolated from stool.

Food may be analyzed by conventional culture methods that require 5 days for presumptive results, or by several rapid methods that are now available.

Shigella spp.
Onset: 12 to 50 hours

Symptoms: Abdominal pain; cramps; diarrhea; fever; vomiting; stools may contain mucous, pus, and blood.

Duration:Acute symptoms may last for 1 to 2 days, or may be prolonged, depending on host factors, ingested dose, and strain. 

Diagnosis of human illness:serological identification of culture isolated from stools.

Isolation procedures in food are difficult due to many factors, among them is the time illness was reported and attempted recovery of suspected food.Enrichment procedures may be needed to recover suspected pathogen since low numbers in food can cause illness. 

Escherichia coli O157:H7

Onset: 3 to 9 days

Symptoms: Abdominal pain, diarrhea, stools are initially watery but become grossly bloody.Vomiting occurs occasionally.Fever may or may not be present. 

Duration:The illness is usually self-limiting and lasts for an average of 8 days.Some individuals exhibit watery diarrhea only. 
Complications: Hemolytic uremic syndrome, vascular and neurologic complications in very young , elderly, and any immune-compromised individuals can be fatal.

Diagnosis of human illness: serological identification of culture isolated from stools.

Rapid methods for detecting this pathogen in food are being developed.One of these methods is the use of DNA probes to detect genes encoding for the production of verotoxins.


(Group A)
Onset: 1 to 3 days

Symptoms: Sore throat, fever, nausea, vomiting, rhinorrhea, tonsillitis, sometimes a rash.

Duration:Variable.Can be treated with antibiotics.

Diagnosis of human illness: culturing of nasal and throat swabs, pus, sputum, blood, suspect food.

Clostridium botulinum
Onset: 18 to 36 hours (Range:4 hours to 8 days)

Symptoms:Early signs of intoxication include lassitude, weakness and vertigo, usually followed by double vision and progressive difficulty in speaking and swallowing.Difficulty in breathing, weakness of other muscles, abdominal distension, and constipation may also be common symptoms

Duration:Can be fatal.Botulinum toxin causes flaccid paralysis by blocking motor nerve terminals at the myoneural junction.Flaccid paralysis progresses symmetrically downward, starting with the face and eyes, to the throat, chest and extremities.When the diaphragm and chest muscles become involved, respiration is stopped and death from asphyxia results.
Treatment involves administration of botulinal toxin and intensive supportive care (including mechanical breathing assistance).Recovery depends on early treatment and care. 

Diagnosis of human illness:Clinical symptoms.Confirmation is determined by demonstrating the presence of toxin in blood and feces, or in food that patient consumed.This is the mouse neutralization test.The test takes 48 hours and culturing specimens takes 5 to 7 days.

Listeria monocytogenes
Onset: Time is unknown.Thought to be greater than 12 hours for gastrointestina1 symptoms.For serious symptoms to develop, the time is thought to be a few days to 3 weeks

Symptoms: Fever, headache, nausea, vomiting, diarrhea precede complications of stillbirths, meningitis, encephalitis, sepsis.

Use of antacids may predispose healthy people to illness.

Duration:Duration of illness is dependent on health status of individuals.Most healthy persons probably show no symptoms unless food was heavily contaminated.Illness can present severe complications to pregnant women and their fetuses (perinatal and neonatal infections), as well as meningitis and septicemia in immune-compromised persons and the elderly.Fatalities occur from these severe complications.

Diagnosis of human illness:Listeriosis is positively confirmed by culturing the organism from blood, cerebrospinal fluid, or stool (although the latter is difficult and of limited value).

Isolation and culturing from food requires an enrichment and identification procedure that requires 5-7 days.Newer methods of DNA technology are now being investigated and used. This technology offers a more 
rapid assessment for the presence of 
L. monocytogenes in food. 

Vibrio cholerae

serogroup non-01
Onset: Illness occurs within 48 hours after ingestion of organism in food (raw oysters along coast of U.S. in warmer months of year). 

Symptoms: Diarrhea, abdominal cramps, and fever.Occasionally nausea, vomiting, and or blood and mucus in stools.Immuno-suppressed individuals and those with cirrhosis may develop severe complications, e.g., septicemia.

Duration:Diarrhea may last from 6 to 7 days and is self-limiting.

Diagnosis of human illness:Culture of human stools.

Isolation and culturing of this microorganism from food also involves pathogenicity testing on suitable animal models.

Vibrio parahaemolyticus
Onset: Illness occurs within 4 to 96 hours after consumption of raw, improperly cooked, or cooked recontaminated fish and shellfish along coast of U.S. in warmer months of year).Use of antacids increases susceptibility.

Symptoms: Abdominal pain, nausea, vomiting, diarrhea, fever, chills, and headache.

Duration:Duration of illness is about 2 1/2 days.

Diagnosis of human illness: Culture of human stools.

Isolation and culturing of this microorganism from food also involves pathogenicity testing on suitable animal models.

Yersinia enterocolitica

Onset: Illness occurs within 24 to 48 hours after ingestion of microorganism in food or drink.

Symptoms: Gastroenteritis with diarrhea, and/or vomiting; fever and abdominal pain are common symptoms.May mimic appendicitis and lymphadentitis.May cause reactive arthritis.

Duration: As long as 2 to 3 weeks.May be treated with antibiotics other than penicillin.

Diagnosis of human illness: Isolation of the organism from the human host's feces, blood, or vomit, or sometimes at the time of appendectomy.Serological identification is also necessary.

Determining the presence of this organism in food involves isolation, confirmation. And:pathogenicity testing.


Hepatitis A virus

Onset: Illness occurs within 10 to 50 days after exposure (median = 30 days).

Symptoms: Fever, general feeling of ill health, loss of appetite, tiredness, nausea, abdominal pain, jaundice.

Duration: If disease is mild, recovery is complete in 1 to 2 weeks.If symptoms are severe, recovery and convalescence can take several months.

Hepatitis A is diagnosed by finding IgM class anti-HAV in serum collected during the acute or early convalescent phase of the disease.

No satisfactory method is available for the routine examination of food at this time.(Sensitive molecular methods used to detect HAV in water and clinical specimens may be used in the future on food.)

Norwalk or Norwalk-like virus
Onset:Illness occurs within 24 to 48 hours after ingestion of microorganism in food or drink..

Symptoms:Nausea, vomiting, abdominal pain, diarrhea, low-grade fever, chills, general feeling of ill health, loss of appetite, headache.

Duration:24 to 60 hours

Specific diagnosis can only be made by a few laboratories that have reagents from human volunteer studies.Identification of the virus can be made on early stool specimens using immune electron microscopy and various immunoassays.Confirmation often requires demonstration of seroconversion, the presence of specific IgM antibody, or a four-fold rise in antibody titer to Norwalk virus on paired acute-convalescent sera.

Has been identified in oysters and clams by radioimmunoassay.Development of gene probes and PCR amplification techniques to detect the virus in clinical specimens and food are under way.

Parasitic Protozoa

Giardia lamblia

Onset: Illness occurs within 3 to 48 days (7 - 10 days median time).

Symptoms: Diarrhea, abdominal pain, steatorrhea, bloating, frequent loose and pale greasy stools, fatigue, weight loss.

Duration: Usually 1 to 2 weeks.In some individuals, it may remain for months to years.

Identification of cysts and/or trophozoites in feces. 

Filtration of water from contaminated water supplies.(Water may contaminate food products when used for irrigation or washing of fresh produce.)

Cryptsporidium spp.
Onset: Illness occurs within 1 to 12 days (7 days median time).

Symptoms: Severe watery diarrhea, but may also be asymptomatic.Pulmonary and tracheal cryptosporidiosis in humans is associated with coughing, possible low grade fever, and sever intestinal distress.

Duration: Usually 2 to 4 days.In some individuals, it may last 1 to 4 weeks.

Identification of oocysts and/or trophozoites in feces.

Procedures for analyzing vegetables for presence of Crytosporidium spp. is given in FDA's Bacteriological Analytical Manual.

Other Parasites 

Trichinella spiralis

Onset: Illness occurs within 8 to 15 days 

(range = 5 to 45 days).

Symptoms: Some gastrointestinal symptoms, other symptoms are dependent on organs or tissue affected.For example, muscle soreness and pain with edema of upper eyelids is an early symptom.These symptoms are followed by retinal hemorrhages, pain and photophobia.There is thirst, profuse sweating, chills (fever), weakness, prostration, and a rapidly increasing number of white blood cells.

Duration: Can cause severe illness and may be fatal if not treated with medication (Mebendazole) in early stages.

Serological tests and rise in number of white blood cells.Biopsy of skeletal muscle is used as a conclusive test.


Benenson, A.S.1995.Control of Communicable Diseases in Man.16th Edition.American Public Health Assoc.Washington, D.C.

FDA.1993.HACCP.Regulatory Food Applications in Retail Food Establishments.Dept. of Health and Human Services.Division of Human Resource Development.HFC-60.Rockville, MD.