*
AMERICAN JOURNAL or EPIDIMIOLOOY
Vol. 106, No 1
Copyright O 1977 by The Johns Hopkins University School of Hygiene and Public Health
Printed in USA
•4
j
LOCATION OF FOOD CONSUMPTION AND TRAVELERS' DIARRHEA
•
W. S. TJOA, H. L. DuPONT, P. SULLIVAN, L. K. PICKERING, A. H. HOLGUIN, J OLARTE, D. G. EVANS AND D J EVANS, J E
"> *
, K
V "
Tjoa, W. S., H. L. DuPont (U. of Texas Medical School, Houston, TX 77030), P. Sullivan, L. K. Pickering, A. H. Holguln, J. Olarte, D. G. Evans and D. J . Evans, Jr. Location of food consumption and travelers' diarrhea. Am J Epidemiol 106:61-66, 1977. Dally food histories for one month were obtained In summer, 1975, from students attending a Mexican university to determine the Influence of food consumption on the development and etiology of diarrhea. In newly-arrived students from the U.S. who ate half or more of their meals in the school cafeteria and public restaurants there were significant increases in diarrhea (p < 0.005), shlgella infection (p < 0.05) and toxlgenic E. coll Infection (p < 0.025) compared to the students eating a comparable number of meals in private homes. In the summer U.S. students there was also an association of diarrhea and eating from street vendors (p < 0.05). In full-time U.S. students who had lived in Mexico a year or longer as well as in Latin American students a relationship between location of meals and occurrence of enteric disease was not apparent. High numbers of enteric bacteria were recovered from food from the school's cafeteria, public restaurants, street vendors and small grocery stores. Shlgella were isolated from cooked and uncooked hamburger patties from the school cafeteria. Four shigella carriers were found among kitchen personnel at the school. This study demonstrates that food serves as a major vehicle through which travelers' diarrhea occurs.
t
diarrhea; disease outbreaks; travel
r
i r
4 /
Diarrhea of travelers usually develops within 14 days of arrival in a foreign country. It is worldwide in distribution but appears to be more prevalent in tropical and sub-tropical countries with poor sanitation and hygiene. The condition is characterized by acute onset of watery diarrhea with the absence of blood and mucus in stools and often with nausea, vomiting, abdominal cramps, malaise, chills or fe-
Microbial pathogens have been focused upon as etiologic agents of travelers' diarrhea. Recent investigations have shown evidence of enterotoxigenic Escherichia coli as the single most important cause of travelers' diarrhea (1-3). While tourists quest8:
Dr. H. L. DuPont, 6400 West Cullen Street, Houston, TX 77030.) ^ ^ P P 0 ^ , !* f * £ £ |*T * e National insti-
1, i. ver. T h e disease g e n e r a l l y lasts for two to t h r e e d a y s a n d in n e a r l y all cases it is selflimited
tutes of Health (AI 12699-01) and a grant from the Norwich Pharmacal Company, Division of MortonNorwich Products, Inc. Presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy, Chicago, IL October 29, 1976. The authors acknowledge the support of the faculty, staff and students at Universidad de las Americas, and the cooperation of Drs. M. Rendon, H. Kirkpatrick, E. Simmen, E. Rice-Wray, P. Carrillo, and C. Moctezuma. G. Haynes and E. Galindo worked on the study. Dr. B. P. Hsi helped with the statistical analysis and Dr. C. S. Hacker assisted with the study design. K. Boyle helped to prepare the manuscript.
Received for publication December 27, 1976, and in final form March 11,1977. Abbreviations; EMB agar, eosin methylene blue agar; LT-E. coli, heat labile enterotoxic Escherichia coli; S-S agar, Salmonella-Shigella agar. From the University of Texas Medical School at Houston and The University of Texas School of Publie Health, Houston, TX and Hospital Infantil de Mexico, Mexico City, D. F., Mexico. (Reprint re61
62
TJOA ET AL
commonly believe the condition is due to contaminated drinking water, there is little evidence to incriminate water in the common form of "turista". Food, with its capacity for supporting bacterial growth, was felt by us to be a more logical source. The present investigation was designed to correlate locations of food consumption with the development of enteric infection among a student population in Mexico.
the preceding week were identified. Students were grouped according to the general location of 50 per cent or more of the meals that week. This per cent was selected to avoid bias in data analysis.
Laboratory procedures The stool specimens were collected in clean cartons provided by the field team. Stools were cultured for enteric pathogens. For the isolation of enteric pathogens, a MATERIALS AND METHODS stool was cultured on eosin methylene blue Two hundred eighty students attending (EMB) agar, sodium tetradecyl sulfate summer school at the University of the (Tergitol 7), and Salmonella-Shigella agar Americas in Cholula, Puebla, Mexico, in (S-S). Shigella colonies were identified by the summer of 1975 were prospectively en- routine techniques of Edwards and Ewing rolled in the study. They were comparable (4). Five colonies of Escherichia coli were in age and health status. Two hundred transferred to nutrient agar stabs for sixty completed the 30-day study, giving a transport back to Houston for studies of dropout rate of 7.1 per cent. This student toxigenicity as recently described (3). Heat population consisted of 49 newly-arrived labile enterotoxigenic E. coli (UT-E. coli) U.S. summer students, 132 full-time U.S. infection was diagnosed by finding LT-E. students who had been at the school one coli in stool during illness and being abyear or longer, and 79 Latin American sent on baseline cultures or by documentstudents from Venezuela or Mexico. The ing fourfold serum antibody rises to the newly-arrived U.S. students were enrolled toxin (5). in the study within 24 hours of arrival at Food was collected in styrofoam specithe school. A stool sample was collected on men cups from the various sources, includthe day of arrival or as soon as their bowel ing restaurants, small stores, open marhabits permitted. A stool sample was col- kets, street vendors and the school cafetelected from all students every three days ria. Samples from private homes were not for 30 days and each student was evalu- obtained in the present study. Ten grams ated daily for the occurrence of diarrhea. of each sample were weighed on a Chaus Rectal swabs were not taken. Daily food Triple Beam Balance. All samples were history sheets containing information re- homogenized with 90 ml of buffer solution garding type of food eaten and the date in a sterile Waring blender for 2 min and and place where each meal was eaten, processed according to a published method including food eaten from a street vendor, (6). Dilutions of 1:100 and 1:1000 were were recorded by each subject. made from the original homogenate. A sample (1 ml) of each of the 100-fold and In the study, diarrhea was defined as 1000-fold homogenate dilutions was greater than twice the usual number of mixed with 9 ml of EMB agar and plated unformed bowel movements within a 12 immediately in disposable petri dishes. 0.1 hour period plus the presence of either fever, nausea, vomiting, abdominal ml of the samples (1:100, 1:1000, 1:10,000) cramps, or malaise. Students reporting ill- were plated on EMB agar. All plates were ness were objectively evaluated for diar- incubated at 33 C for 48 hr. The enteric rhea; unformed stools had to be observed bacteria were enumerated and identified by the field team. When diarrhea was di- according to Edwards and Ewing (4). agnosed the location of meals consumed Stools were obtained from 22 of the
63
FOOD CONSUMPTION AND TRAVELERS' DIARRHEA
meals in a private home (p < 0.005). Shigella infection was significantly greater (p < 0.05) in U.S. summer students eating in the cafeteria or restaurants (31 per cent) when compared to those eating in private homes (5 per cent). In contrast, there was no correlation between location of food consumption and occurrence of diarrhea or shigella isolation among full-time U.S. students or Latin Americans (Venezuelans and Mexicans). Table 2 shows the occurrence of toxigenic LT-E. coli infection (which occurred throughout the month of study) and location of major food consumption the week preceding the infection. Toxigenic E. coli infection was related to eating food at the school cafeteria and public restaurants. A
kitchen personnel in the school cafeteria for isolation of enteric pathogens as a single survey. Data were analyzed by the chi-square test of independence. No adjustments were made for comparing groups of different size or composition. RESULTS
Diarrhea development was associated with eating meals at the various local restaurants and the school cafeteria (see table 1). Diarrhea occurred in 13 of the 29 U.S. summer students (45 per cent) who ate more than 50 per cent of their meals in the school cafeteria and/or public restaurants, compared to three of the 20 U.S. summer students (15 per cent) who ate most of their
TABLE 1
Occurrence of diarrhea and shigella isolation from stool, according to location of major food consumption during a 30-day period, m 260 students attending a Mexican university, summer, 1975 Greater than fifty per cent of meals In school cafeteria and/or public restaurants
In private homes
Student status
Shipella isolation (%)
No. students
Diarrhea
AMERICAN JOURNAL or EPIDIMIOLOOY
Vol. 106, No 1
Copyright O 1977 by The Johns Hopkins University School of Hygiene and Public Health
Printed in USA
•4
j
LOCATION OF FOOD CONSUMPTION AND TRAVELERS' DIARRHEA
•
W. S. TJOA, H. L. DuPONT, P. SULLIVAN, L. K. PICKERING, A. H. HOLGUIN, J OLARTE, D. G. EVANS AND D J EVANS, J E
"> *
, K
V "
Tjoa, W. S., H. L. DuPont (U. of Texas Medical School, Houston, TX 77030), P. Sullivan, L. K. Pickering, A. H. Holguln, J. Olarte, D. G. Evans and D. J . Evans, Jr. Location of food consumption and travelers' diarrhea. Am J Epidemiol 106:61-66, 1977. Dally food histories for one month were obtained In summer, 1975, from students attending a Mexican university to determine the Influence of food consumption on the development and etiology of diarrhea. In newly-arrived students from the U.S. who ate half or more of their meals in the school cafeteria and public restaurants there were significant increases in diarrhea (p < 0.005), shlgella infection (p < 0.05) and toxlgenic E. coll Infection (p < 0.025) compared to the students eating a comparable number of meals in private homes. In the summer U.S. students there was also an association of diarrhea and eating from street vendors (p < 0.05). In full-time U.S. students who had lived in Mexico a year or longer as well as in Latin American students a relationship between location of meals and occurrence of enteric disease was not apparent. High numbers of enteric bacteria were recovered from food from the school's cafeteria, public restaurants, street vendors and small grocery stores. Shlgella were isolated from cooked and uncooked hamburger patties from the school cafeteria. Four shigella carriers were found among kitchen personnel at the school. This study demonstrates that food serves as a major vehicle through which travelers' diarrhea occurs.
t
diarrhea; disease outbreaks; travel
r
i r
4 /
Diarrhea of travelers usually develops within 14 days of arrival in a foreign country. It is worldwide in distribution but appears to be more prevalent in tropical and sub-tropical countries with poor sanitation and hygiene. The condition is characterized by acute onset of watery diarrhea with the absence of blood and mucus in stools and often with nausea, vomiting, abdominal cramps, malaise, chills or fe-
Microbial pathogens have been focused upon as etiologic agents of travelers' diarrhea. Recent investigations have shown evidence of enterotoxigenic Escherichia coli as the single most important cause of travelers' diarrhea (1-3). While tourists quest8:
Dr. H. L. DuPont, 6400 West Cullen Street, Houston, TX 77030.) ^ ^ P P 0 ^ , !* f * £ £ |*T * e National insti-
1, i. ver. T h e disease g e n e r a l l y lasts for two to t h r e e d a y s a n d in n e a r l y all cases it is selflimited
tutes of Health (AI 12699-01) and a grant from the Norwich Pharmacal Company, Division of MortonNorwich Products, Inc. Presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy, Chicago, IL October 29, 1976. The authors acknowledge the support of the faculty, staff and students at Universidad de las Americas, and the cooperation of Drs. M. Rendon, H. Kirkpatrick, E. Simmen, E. Rice-Wray, P. Carrillo, and C. Moctezuma. G. Haynes and E. Galindo worked on the study. Dr. B. P. Hsi helped with the statistical analysis and Dr. C. S. Hacker assisted with the study design. K. Boyle helped to prepare the manuscript.
Received for publication December 27, 1976, and in final form March 11,1977. Abbreviations; EMB agar, eosin methylene blue agar; LT-E. coli, heat labile enterotoxic Escherichia coli; S-S agar, Salmonella-Shigella agar. From the University of Texas Medical School at Houston and The University of Texas School of Publie Health, Houston, TX and Hospital Infantil de Mexico, Mexico City, D. F., Mexico. (Reprint re61
62
TJOA ET AL
commonly believe the condition is due to contaminated drinking water, there is little evidence to incriminate water in the common form of "turista". Food, with its capacity for supporting bacterial growth, was felt by us to be a more logical source. The present investigation was designed to correlate locations of food consumption with the development of enteric infection among a student population in Mexico.
the preceding week were identified. Students were grouped according to the general location of 50 per cent or more of the meals that week. This per cent was selected to avoid bias in data analysis.
Laboratory procedures The stool specimens were collected in clean cartons provided by the field team. Stools were cultured for enteric pathogens. For the isolation of enteric pathogens, a MATERIALS AND METHODS stool was cultured on eosin methylene blue Two hundred eighty students attending (EMB) agar, sodium tetradecyl sulfate summer school at the University of the (Tergitol 7), and Salmonella-Shigella agar Americas in Cholula, Puebla, Mexico, in (S-S). Shigella colonies were identified by the summer of 1975 were prospectively en- routine techniques of Edwards and Ewing rolled in the study. They were comparable (4). Five colonies of Escherichia coli were in age and health status. Two hundred transferred to nutrient agar stabs for sixty completed the 30-day study, giving a transport back to Houston for studies of dropout rate of 7.1 per cent. This student toxigenicity as recently described (3). Heat population consisted of 49 newly-arrived labile enterotoxigenic E. coli (UT-E. coli) U.S. summer students, 132 full-time U.S. infection was diagnosed by finding LT-E. students who had been at the school one coli in stool during illness and being abyear or longer, and 79 Latin American sent on baseline cultures or by documentstudents from Venezuela or Mexico. The ing fourfold serum antibody rises to the newly-arrived U.S. students were enrolled toxin (5). in the study within 24 hours of arrival at Food was collected in styrofoam specithe school. A stool sample was collected on men cups from the various sources, includthe day of arrival or as soon as their bowel ing restaurants, small stores, open marhabits permitted. A stool sample was col- kets, street vendors and the school cafetelected from all students every three days ria. Samples from private homes were not for 30 days and each student was evalu- obtained in the present study. Ten grams ated daily for the occurrence of diarrhea. of each sample were weighed on a Chaus Rectal swabs were not taken. Daily food Triple Beam Balance. All samples were history sheets containing information re- homogenized with 90 ml of buffer solution garding type of food eaten and the date in a sterile Waring blender for 2 min and and place where each meal was eaten, processed according to a published method including food eaten from a street vendor, (6). Dilutions of 1:100 and 1:1000 were were recorded by each subject. made from the original homogenate. A sample (1 ml) of each of the 100-fold and In the study, diarrhea was defined as 1000-fold homogenate dilutions was greater than twice the usual number of mixed with 9 ml of EMB agar and plated unformed bowel movements within a 12 immediately in disposable petri dishes. 0.1 hour period plus the presence of either fever, nausea, vomiting, abdominal ml of the samples (1:100, 1:1000, 1:10,000) cramps, or malaise. Students reporting ill- were plated on EMB agar. All plates were ness were objectively evaluated for diar- incubated at 33 C for 48 hr. The enteric rhea; unformed stools had to be observed bacteria were enumerated and identified by the field team. When diarrhea was di- according to Edwards and Ewing (4). agnosed the location of meals consumed Stools were obtained from 22 of the
63
FOOD CONSUMPTION AND TRAVELERS' DIARRHEA
meals in a private home (p < 0.005). Shigella infection was significantly greater (p < 0.05) in U.S. summer students eating in the cafeteria or restaurants (31 per cent) when compared to those eating in private homes (5 per cent). In contrast, there was no correlation between location of food consumption and occurrence of diarrhea or shigella isolation among full-time U.S. students or Latin Americans (Venezuelans and Mexicans). Table 2 shows the occurrence of toxigenic LT-E. coli infection (which occurred throughout the month of study) and location of major food consumption the week preceding the infection. Toxigenic E. coli infection was related to eating food at the school cafeteria and public restaurants. A
kitchen personnel in the school cafeteria for isolation of enteric pathogens as a single survey. Data were analyzed by the chi-square test of independence. No adjustments were made for comparing groups of different size or composition. RESULTS
Diarrhea development was associated with eating meals at the various local restaurants and the school cafeteria (see table 1). Diarrhea occurred in 13 of the 29 U.S. summer students (45 per cent) who ate more than 50 per cent of their meals in the school cafeteria and/or public restaurants, compared to three of the 20 U.S. summer students (15 per cent) who ate most of their
TABLE 1
Occurrence of diarrhea and shigella isolation from stool, according to location of major food consumption during a 30-day period, m 260 students attending a Mexican university, summer, 1975 Greater than fifty per cent of meals In school cafeteria and/or public restaurants
In private homes
Student status
Shipella isolation (%)
No. students
Diarrhea
