ABSTARCT
Objective:
To report and to determine the cause and source of food poisoning which occurred at a Military Training School in Zarqa at July 15th 2009,
and to characterize staphylococcal food poisoning.
Methods:
A total of 243 students who developed signs and symptoms of suspected food poisoning at a Military Training School in Zarqa on July 15th
2009 were interviewed using a structured special food poisoning questionnaire. Data were transferred to a specified food poisoning attack rate table
where the incubation period, attack rates, attributable risks, relative risks, chi square, confidence intervals and p-value were calculated. Stool
specimens, food and water samples were collected and analyzed.
Results:
The data collection, laboratory and environmental sanitation indicate that this food poisoning was caused by Staphylococcus aureus and the incriminated
food was the dairy product (Labanah) component of a breakfast meal.
Conclusion:
This outbreak highlights the public health significance of positive food poisoning outbreaks that may involve a large number of people in a close
community.
Key words
:
Epidemiology, Outbreak, Staphylococcus aureus.
JRMS March 2015; 22(1): 75-78 / DOI:
10.12816/0009791
Introduction
Food borne diseases (FBD), including food borne intoxications and food borne infections, are terms applied to illnesses acquired through consumption of
contaminated food; they are frequently and inaccurately referred to as food poisoning.
These diseases include those caused by chemical contaminants
such as heavy metals and many organic compounds; the more frequent causes of food borne illnesses are: (1) Toxins elaborated by bacterial growth
in the food before consumption (Staphylococcus aureus and Bacillus cereus, (2) Bacterial, Viral, and Parasitic infections ( Brucellosis, Campylobacter enteritis, E.coli, and (3) Toxins produced by harmful algal species.(1)
Surveillance of food borne illnesses is complicated by several factors, the first is underreporting, although food borne illnesses can be severe or
even fatal.(1)
Among the bacteria involved in these diseases, Staphylococcus aureus is a leading cause of gastroenteritis.(2) FBDs are defined by
the World Health Organization (WHO) as “Diseases of infectious or toxic nature caused by, or thought to be caused by the consumption of food or water". (3)
FBDs outbreaks are recognized by the occurrence of illness within a variable but usually short time period; also many countries
defined FBD outbreaks as the occurrence of two or more cases of a similar illness resulting from the ingestion of a common food.(1,3) FBDs are suspected of ~ 76 million illnesses, 325,000 hospitalization and 5,200 deaths each year.(3) The symptoms of
Staphylococcal food poisoning are abdominal cramps, nausea, vomiting, sometimes followed by diarrhoea (never diarrhoea alone), the onset of symptoms is
rapid from 30 minutes to 8 hours, usually 2-4 hours, and spontaneous remission is observed after 24 hours.(1,3)
Methods
A total 243 students at the Military School in Zarqa ate their breakfast on July 15th, 2009. The meal was prepared at the school's kitchen.
A number of school students developed clinical signs and symptoms of food poisoning within few hours after breakfast and were investigated to determine
the source and the agent of the outbreak. All the students were males with age range of 18-24 years (mean age 21 years). All attendants of the
breakfast meal were included in the investigation. The breakfast meal consisted of olives, milk, hummus, cheese and dairy product (labaneh),
Collection of field data was performed through face to face interviews of the 243 students at the Military School, using a special food poisoning
structured questionnaire. The interviews were conducted by two trained physicians on the same day of the outbreak. The questionnaire covered the
following data: clinical details of the illness such as nausea, cramps, vomiting, diarrhoea, fever, time of onset following breakfast and details of
consumed foods. A case was defined as a person who experienced at least one of the following symptoms within 12.5 hours of eating the school meal:
cramps, nausea, vomiting or diarrhoea (three or more loose stools). Staphylococcal food poisoning was defined as a gastro-intestinal illness in two or
more persons with a common food exposure and adequate isolation of 10(5) or more micro-organisms from the implicated food.
Stool specimens for culture were collected from ill students and food handlers. No food handlers had symptoms or signs suggesting skin infections. Food
samples were also obtained for bacteriological and toxicological analysis. Also nasopharyngeal swabs were taken from all eight asymptomatic food
handlers working in the military school kitchen; all these samples were sent to specialized laboratories: Jordan Military Laboratory for Quality
Control and Princess Iman Centre for Research and Laboratory Sciences.
Sanitation
A complete kitchen sanitation inspection was conducted at the school on the day of the outbreak. The inspection included the refrigeration, food
preparation procedures, general cleanliness, water tanks and general condition of kitchen equipment. Eight water samples were collected from different
sites and sent for bacteriological examinations.
Data Analysis
All information obtained from the questionnaire was transferred into specific food poisoning attack rate table. Attack rates for those who had eaten
and those who had not eaten the specified food item were calculated using the formula of: Attack rate, Attributable, Relative risk, X2
(Yate's correction), Confidence interval (CI) and p-value.
Results
Face to face interviews revealed that of the 243 cadets interviewed, 146 (60%) were ill, and met the case definition. Of those, 54 students (37%) were
discharged following supportive treatment at the Emergency Department and 92 (63%) were treated at the school clinic (Table I). Regarding the most
common symptoms and complaints, the most common complaint was vomiting (86%) followed by abdominal cramps (79) and diarrhoea (66%). Subjective fever
was reported by 4% patients only, as shown in Table II.
Table III demonstrated that the highest attack rate was for the Labanah compared with other food items. Similarly the attributable risk was also
highest in the Labanah meal (67%). The risk of eating Labanah was 35 times more than the risk of eating other food items. Calculated chi-square was
14.2, p<0.0001 and 95% confidence interval = 8.4, 130.7 as shown in Table IV.
Laboratory Results
Results of the microbiological analysis of the food samples are summarized in Table V.
Table I:
Number of ill students interviewed in the outbreak
|
Interviewed students
|
Number
|
%
|
|
Ill
|
146
|
60
|
|
Well
|
97
|
40
|
|
Total
|
243
|
100
|
Table II:
The number of signs and symptoms among ill patients
|
%
|
Number
|
Signs & Symptoms
|
|
86
|
127
|
Vomiting
|
|
79
|
116
|
Abdominal cramps
|
|
66
|
89
|
Diarrhoea
|
|
4
|
8
|
Fever
|
Table III:
Specified food poisoning attack rate for food items consumed in the outbreak
|
P-value
|
Person who DID NOT EAT suspected food
|
Person who DID EAT suspected food
|
Suspected food
|
|
|
Sick Well Total AR%
|
Sick Well Total AR%
|
|
|
-17
|
60
|
77
|
31
|
46
|
43
|
46
|
25
|
21
|
Olive
|
|
67
|
2
|
25
|
24
|
1
|
69
|
85
|
30
|
55
|
Labanah
|
|
-12
|
59
|
74
|
30
|
44
|
47
|
48
|
25
|
23
|
Hummus
|
|
4
|
53
|
48
|
23
|
25
|
57
|
76
|
32
|
44
|
Cheese
|
|
-15
|
60
|
78
|
31
|
47
|
45
|
46
|
24
|
22
|
Milk
|
Table IV:
Incidence rate, Relative Risk, Confidence Interval, Chi-square and P-value of the specific food after the outbreak of food poisoning
|
P-value
|
Chi-square
|
95% Confidence Interval
|
RR
|
AR among who did not eat specified food %
|
AR among who ate specified food %
|
Food item
|
|
0.005>
|
12.04
|
0.60-0.87
|
0.72
|
60
|
43
|
Oliver
|
|
0.0011
|
14.2
|
8.4-130.7
|
34.5
|
2
|
69
|
Labanah
|
|
0.01>
|
7.7
|
0.64-0.92
|
0.78
|
59
|
47
|
Hummus
|
|
0.05*<
|
0.8
|
0.07-1.3
|
1.1
|
53
|
57
|
Cheese
|
|
0.005>
|
10.2
|
0.62-0.90
|
0.75
|
60
|
45
|
Milk
|
* Value not significant
Table V:
Results of bacteriologic studies, gastroenteritis in a Military school at Zarqa 2009
|
Organism/Salmonella, Shigella, Staphylococcus
|
Source of food sample
|
|
Not isolated
|
Oliver
|
|
Staphylococcus aureus >105 micro-organisms
|
Labanah
|
|
Not isolated
|
Hummus
|
|
Not isolated
|
Cheese
|
|
Not isolated
|
Milk
|
Table VI. Differential diagnosis of bacterial poisoning, incubation period and clinical signs and symptoms
|
Cramps
|
Vomiting
|
Diarrhoea
|
Fever
|
Incubation period/hours
|
Causative Organism
|
|
+
|
+
|
±
|
-
|
0.5-8
|
Staphylococcus aureus
|
|
+
|
±
|
+
|
+
|
6-72
|
Salmonella
|
|
+
|
-
|
+
|
-
|
6-24
|
Clostridium welchi
|
|
+
|
±
|
±
|
-
|
1-16
|
Bacillus cereus
|
Staphylococcus aureus
was cultured from the Labanah meal, toxicological analysis of food samples revealed no evidence of performed chemical toxins by the Atomic Absorption
Analyzer.(4) Water samples showed no evidence of E. coli or other microbiologic contamination,
stool cultures were performed from 26-56 sick students with diarrhoea referred to hospital and were all negative for Salmonella and Shigella. (5) Differential diagnosis between different micro-organisms that causes food outbreak supports this conclusion as shown in Table VI.
Discussion
The epidemiologic, clinic, laboratory and environmental investigations indicated that this large food poisoning outbreak was caused by Staphylococcus aureus contaminating the Labanah meal. A significant number of students had onset of illness (within few hours of consumption of the
implicated meal), with vomiting, consistent with the finding of the Labanah by Staphylococcus aureus. Diarrhoea without vomiting is rare in persons
with staphylococcal food poisoning.
Food borne disease outbreaks are recognized by the occurrence of illness within a short period of time (a few hours to a few weeks), FBD may be one of the
most common causes of acute illness; many cases and outbreaks are unrecognized and unreported.(1) In most countries (including the USA
and France), bacteria is the leading cause of FBD and appear to be the causative agent of more than two thirds of the recorded FBD outbreaks. The
pathogenesis of bacteria using FBD depends in their capacity to produce toxins after ingestion in the digestive tract or before (toxins preformed in
foodstuff).(2)
The responsible pathogen of this outbreak coincides with other studies which revealed that micro-organisms Salmonella,
Clostridium perfringens and Staphylococcus enterotoxin were responsible for about 20%, 6% and 3% respectively of the food borne outbreaks in the USA
according to CDC surveillance,(6) and coincides also with other studies confirmed these results and findings regarding the etiological
agents are reported by Adwan(7) Asao et al. described an extensive outbreak of staphylococcal food poisoning occurred
in Kansai in Japan in 2006 where 13,420 cases frequently ingested dairy products.(8)
Another outbreak with staphylococcus aureus as a
causative micro-organism occurred among twelve people attended a birthday party in 1994 was reported by Maria and Luiz (9) Other food
poisoning outbreak due to staphylococcus aureus was investigated in a military establishment and reported by Mustafa et al. in 2009.(10) Also in an airforce base in Western Greece had occurred among military personnel as reported by Jelastopulu and Veniere. (11)
It has been shown that Staphylococcus aureus is able to colonize milk and dairy products producing toxins that can cause poisoning in
humans, causing serious health problem for food security, and was reported by Fueyo et al.(12) Adwan et al. (13) reported that Staphylococcus aureus strains produce toxins that are common causes of food poisoning outbreaks.
Conclusion
This outbreak highlighted the importance of food poisoning outbreaks that involve big number of people in a closed community, and satisfactory results
could be achieved with a proper treatment.
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