Food-borne salmonella outbreak at a bank cafeteria an

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					470                                     La Revue de Santé de la Méditerranée orientale, Vol. 15, N° 2, 2009

Case report

Food-borne salmonella outbreak at
a bank cafeteria: an investigation in
an Arab country in transition
N.M. Hanna,1 S.M. Adib2 and Z. Daoud1

Introduction                                           were sent on 18 May to the Central Labora-
                                                       tory, the government reference laboratory in
Symptoms of gastroenteritis compatible                 Beirut. On 19 May, testing of the remains of
with a food-borne outbreak started appear-             the incriminated dish demonstrated the pres-
ing among employees at the central head-               ence of S. enterica Serovar Enteritidis, thus
quarters of a “Bank” located in Beirut,                confirming the contamination of the dish.
Lebanon, on the evening of Monday 17
May 2004. Earlier on that day, many em-
ployees had had lunch at the bank cafeteria.           Case report
All of those with signs and symptoms had
eaten the main dish of chicken noodles au              Preliminary epidemiological findings
gratin served at the cafeteria on that day.            A team of independent Lebanese investiga-
The chicken noodle dish had been brought               tors hired by the Bank conducted inves-
from the kitchen of a local catering com-              tigations in parallel to the public health
pany in 2 large serving containers. This ca-           services. They obtained the chronological
tering company has an excellent reputation             order of events. The incriminated dish had
in Beirut and had been serving the Bank for            been brought from the catering kitchen at
more than a year with no previous problems             11:30 on May 17, and set up on the heating
reported.                                              table of the cafeteria. It started to be served
    Public health officers alerted to the out-         about 1 hour later. The cafeteria personnel
break went to the caterer on May 18 in line            reported serving about 40 dishes during the
with legal regulations. Based on the mandate           lunch break on that day. Of those eating it,
of an obsolete law they were supposed to               only 32 people could be identified by name.
“destroy” the remains of the “poisoned”                Upon being interviewed, it appeared that 26
food items. This kind of policy usually                had developed signs and symptoms of gas-
renders all evidence-based epidemiological             troenteritis, and 14 had been hospitalized.
investigations impossible. Fortunately, a              In at least 1 case, the chicken noodle dish
portion of leftovers of the chicken noodles            had been the only food item consumed at
had been hidden by the caterers from the               the cafeteria or outside throughout the day
public health food inspectors, in anticipation         prior to the appearance of gastroenteritis
of potential court action. Those leftovers             symptoms. No cases appeared among those
  Department of Medical Laboratory Sciences, Faculty of Health Sciences, University of Balamand, Beirut,
Lebanon (Correspondence to Z.D. Daoud:
  Department of Public Health, Faculty of Medicine, Saint-Joseph University, Beirut, Lebanon.
Received: 07/04/06; accepted: 13/09/06

                 ٢٠٠9 ،٢ ‫املجلة الصحية لرشق املتوسط، منظمة الصحة العاملية، املجلد اخلامس عرش، العدد‬
 Eastern Mediterranean Health Journal, Vol. 15, No. 2, 2009                                                  471

 who had not taken the dish or had not eaten               Table 1 Frequency of signs/symptoms
 at the cafeteria.                                         following the outbreak (n = 32)
     For this investigation, a case of food-               Sign/symptom                   No.          %
 borne illness was defined as a person who                 Diarrhoea                      23          88.5
 had developed diarrhoea or fever greater                  Fever                          22          84.6
 than 38 °C between 17 and 19 May. The                     Abdominal pain                 21          80.8
 attack rate was thus very high at 81%, sug-               Vomiting                       16          61.0
 gesting a very large infective dose ingested              Loss of consciousness           3          11.5
 via the incriminated dish.
     Signs started emerging as early as 5.5
 hours after ingestion of the incriminated                 after ingestion of contaminated food or wa-
 meal, and up to 22.5 hours later. The mean                ter and may last between 2 and 7 days [1].
 incubation period was 10.3 (standard devia-               The most credible differential diagnosis in
 tion 4.1; median 9.1) hours for the whole                 this case would have been a staphylococcal
 group. The distribution of the incubation                 intoxication. However, signs of intoxication
 periods is shown in the epidemiological                   with staphylococcus usually appear a few
 curve (Figure 1).                                         hours following ingestion, and end within
     Most commonly reported signs were                     1-2 days. The clinical presentation did not
 diarrhoea (88.5%) and fever (84.6%), with                 point to a diagnosis of botulism or any other
 signs of systemic infection in at least 11.5%             enteric infection [2].
 of the group (Table 1). In one case, se-                      Salmonellosis was confirmed in stool
 vere septicaemia occurred. These findings                 and blood cultures within 48–72 hours after
 are compatible with salmonella infection,                 hospital admission of the first cases. S.
 which may classically begin 6–48 hours                    enterica Serovar Enteritidis was isolated




No. of cases






                   5h−7.5h   7.5h−10h   10h−12.5h   12.5h−15h   15h−17.5h   17.5h−20h   20h−22.5 h   22.5h−25h


 Figure 1 Appearance of clinical symptoms in infected patients, epidemiological curve (n = 26)

 ٢٠٠9 ،٢ ‫املجلة الصحية لرشق املتوسط، منظمة الصحة العاملية، املجلد اخلامس عرش، العدد‬
472                                 La Revue de Santé de la Méditerranée orientale, Vol. 15, N° 2, 2009

from 2 patients in 2 different hospitals, and          All 3 avenues had to be explored to
identified using the API 20E test strip (Bio-      determine the origin of the contamination.
Mérieux, France). It corresponded to the               All 18 kitchen workers provided samples
strain found in the incriminated dish, further     of rectal and nasal mucosa to be cultured at
supporting the suggestion of a point source        the laboratory of the Saint-Georges Ortho-
food infection in all gastroenteritis cases        dox Hospital in Beirut. Results confirmed
reported at the Bank.                              the absence of Salmonella carriage in all
                                                   workers. At the time of the outbreak, drink-
Upstream findings                                  ing water was provided to the catering com-
After confirming the epidemiological links         pany from a tanker company, as city water
between the infected chicken noodle dish           is not sufficient for their needs. Despite the
and the gastroenteritis cases, a visit to the      usual chlorination and filtration procedures,
catering company kitchen was conducted.            water samples repeatedly done on May 18
It showed that standard procedures of food         and 21 yielded high faecal coliform counts
handling had been followed. The dish had           but no Salmonella. This evidence that some
been served at the Bank in the past with no        long-term contamination had been tak-
apparent health problems, suggesting that          ing place in the water reservoirs involving
the usual preparation process in the kitch-        ubiquitous, though not pathogenic, bacteria
en may not be immediately incriminated.            did not have direct relevance to the outbreak
Preparation normally starts in the evening         under investigation.
prior to the day the dish is served. However,          On May 28, the caterers revealed the
in this instance, some of the constituents         existence of a frozen batch of the same raw
had been prepared 3 days ahead, because            chicken breast consignment that had been
the dish was to be served on a Monday, im-         used for the chicken noodles. This batch
mediately after the week-end closure.              yielded a significant growth of S. enterica
    In the process of preparing the chicken        Serovar Enteritidis, thus providing a bacte-
noodle dish, there were at least 3 potential       rial link to the infected dish and to the
routes of contamination:                           gastroenteritis cases. The batch of chicken
• chicken: the raw chicken obtained from           came from a large producer of poultry and
    a local farm could have been contami-          eggs in Lebanon. Within a few days of
    nated prior to the cooking process;            finding the contaminated raw chicken, in-
• kitchen water: could have contaminated           formal information was channeled to the
  the noodles at the time of cooling, or           investigators through the catering business
  milk put in at the time of mixing the            grapevine about the existence of other cases
  sauce: organisms by this route may have          of salmonellosis related to chicken from the
  had enough time to multiply and become           same origin.
  a large infective inoculum;                          This suggested that the outbreak was
                                                   multicentred, and serious enough to war-
• food-handlers: carriers of infective or-         rant an intervention at the farm level. The
  ganisms may have contaminated the                producer was advised of their potential in-
  ingredients during the preparation proc-         volvement in a major food-borne outbreak.
  ess; at various stages, almost all workers       They refused to provide access for further
  in the kitchen were involved in prepar-          investigation on their property.
  ing the chicken noodles.

                ٢٠٠9 ،٢ ‫املجلة الصحية لرشق املتوسط، منظمة الصحة العاملية، املجلد اخلامس عرش، العدد‬
Eastern Mediterranean Health Journal, Vol. 15, No. 2, 2009                                       473

Laboratory confirmation of the chain                       This investigation revealed important
of events                                              gaps in the process of food-borne outbreak
The final proof of the alleged chain of events         control in Lebanon. Its usefulness as a case
came after the isolates growing in the raw             study results from the conjunction of sever-
chicken and in the chicken noodle leftovers,           al factors not usually found in all outbreaks.
as well as those isolated from 2 hospitalized          First, the management of the Bank was suf-
patients, appeared to be genetically similar.          ficiently incensed to decide to litigate, and
Confirmation tests were conducted at the               was aware of the need for solid evidence
Institut Pasteur in Paris, as the techniques           to win any court action. Having observed
necessary for this process are not currently           the apparently inefficient way that public
available in Lebanon. The confirmation was             authorities were conducting the procedure,
obtained using random amplified polymor-               they took the initiative to call upon an
phic DNA-PCR (RAPD-PCR).                               independent investigative team. The cater-
    In light of these findings, it was sug-            ers, concerned that they would be the only
gested that raw chicken contaminated with              party blamed for the salmonella outbreak,
S. enterica Serovar Enteritidis had been               had succeeded in concealing some raw and
shipped to the catering company. The prep-             cooked items from the destructive path of
aration process not only did not eradicate             the public health authorities. These items
the contamination, but provided it with                were central to establishing contamination
substrates and delays sufficient to increase           upstream from the caterers’ kitchen.
the inoculum to infective doses. The end                   It is generally admitted that food prep-
result was a serious outbreak of salmonel-             aration does not by itself guarantee the
losis among the Bank employees.                        eradication of bacteria. Cooking reduces
                                                       the bacterial load to a minimal level not im-
                                                       mediately dangerous to humans in normal
Discussion and practical                               health. However, should fully cooked or
implications                                           semi-cooked items be stored in less than
                                                       adequate conditions, the load will increase
Food-borne salmonella outbreaks can create             to an infective threshold. For the catering
a severe public health threat [3]. Prevention          company, it has become clear that storage
is therefore an appropriate and necessary              of food items prepared with potentially con-
policy. In Lebanon, food-borne outbreaks,              taminated raw ingredients at the standard
whenever detected, must be reported by                 4 ºC was inadequate when the delay before
law to the Epidemiological Surveillance                consumption was several days. Freezing
Unit at the Ministry of Public Health in               cabinets have now been recommended for
Beirut. It is believed that the major part             items which have to be stored for longer
of the case-load goes undiagnosed, and                 than overnight.
therefore undetected, and that only the very               Obsolete laws dating back to the 1930s
tip of the iceberg is ever reported. Despite           still govern what should be done following
this, food-borne diseases are still the most           a report of “food poisoning”. Public health
commonly reported infectious diseases, in              officers are mandated to stop the spread by
a country where this category of diseases is           “destroying” allegedly contaminated food
generally receding within the context of an            items and closing down incriminated facili-
epidemiological transition similar to that in          ties. The result of this activity is generally
more advanced nations [4].

٢٠٠9 ،٢ ‫املجلة الصحية لرشق املتوسط، منظمة الصحة العاملية، املجلد اخلامس عرش، العدد‬
474                                   La Revue de Santé de la Méditerranée orientale, Vol. 15, N° 2, 2009

agreeable to the public but has never been           Acknowledgements
proven to be epidemiologically sound.
   This investigation was conducted at               This study was made possible through fund-
times almost in contravention to cur-                ing provided by the Bank to the health inves-
rent laws, but in as much conformity to              tigation team composed of academic experts
textbook procedures as possible [5]. It              in the field. Some laboratory tests were con-
may provoke several changes in the way               ducted free of charge at the Institut Pasteur in
food-borne outbreaks are investigated,               Paris, France. We are particularly grateful to
controlled and prevented in the future in            Ms D. Populaire who conducted the tests.

1.    Mims C et al. Gastrointestinal tract infec-    4.   Ministry of Public Health. Epidemiological
      tions. In: Mims medical microbiology,               Surveillance Unit. Epi-news (http://cms1.
      3rd ed. Philadelphia, Elsevier Mosby,     
      2004:282–3.                                         miologicalSurveillanceUnit, accessed 12
                                                          April 2009).
2.    Black JG. Oral and gastro-intestinal dis-
      eases. In: Microbiology: principles and        5.   American Medical Association et al. Di-
      explorations, 6th ed. New York, John                agnosis and management of foodborne
      Wiley & Sons, 2004:652–4.                           illnesses: a primer for physicians and
                                                          other health care professionals. MMWR
3.    Centers for Disease Control. Preliminary
                                                          recommendations and reports, 2004,
      FoodNet data on incidence of foodborne
                                                          53(RR04):1–33 (
      illnesses—selected sites, United States,
      2001. Morbidity and mortality weekly
                                                          accessed 16 May 2008).
      report, 2002, 51(15):325–9.

                  ٢٠٠9 ،٢ ‫املجلة الصحية لرشق املتوسط، منظمة الصحة العاملية، املجلد اخلامس عرش، العدد‬

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