Enb03-01w.p65

http://www.env.gov.sg/info/publications/enb_news.html PUBLICATION OF THE COMMITTEE ON EPIDEMIC DISEASES Surveillance of multi-drug resistant Salmonella
typhimurium
The emergence of Salmonella strains that are by the clinical laboratories of hospitals. S. typhi, S. resistant to commonly used antibmicrobials is impor- paratyphi, S. enteritidis and S. typhimurium are also tant to clinicians, microbiologists and those respon- sible for the control of foodborne infectious diseases.
Salmonella typhimurium definite type 104 (DT104) In July 2000, an unusual increase in the isola- or phage type 104 (PT104) with resistance to ampi- tion of S. typhimurium PT104L with resistance to cillin, chloramphenicol, streptomycin, sulphonamide ampicillin, chloramphenicol, gentamicin, streptomy- and tetracycline (ACS Su T) was first reported in the cin, tetracycline and sulphonamide or R-type UK in 1984. Since then, it has been reported with ACGSTS3), was noted. The isolates came mainly increasing frequency in other European countries, from the stool cultures of children below 18 months Japan and the United States. In the UK, it is the sec- ond most prevalent type of Salmonella isolated from The Quarantine & Epidemiology Department humans. Outbreaks related to this strain have also of the Ministry of the Environment was notified and been reported in Ireland, Northern California and epidemiological investigations were conducted.
In Singapore, laboratory surveillance to moni- Epidemiological investigations
tor the introduction of multidrug-resistant S. typhimurium strain is undertaken by the National Infants and toddlers aged between one month Enteric Bacteria Centre of the Department of Pathol- and 36 months whose stool cultures were positive ogy, Singapore General Hospital. The centre under- for S. typhimurium DT104L during the period July- takes serotyping of all Salmonella isolates submitted August 2000 were traced to determine the source of CONTENTS
Surveillance of multi-drug resistant Salmonella typhimurium . P. 15
The infectious disease situation in 2000 . P. 18
Epidemiological News Bulletin readership survey . P. 20
Cases of specified notifiable diseases . P. 22
infection and the mode of transmission. The home 10 in August, 4 in September and 2 in October. Ex- of each child was visited to look for other unre- cept for 4 adults aged between 31 years and 66 years, ported cases among contacts. The parent, guard- all the others were toddlers and infants as young as 2 ian, or domestic maid was interviewed by two days of age. There were 19 males and 14 females trained environmental health officers using a struc- (Table 1). None of them had a recent travel history tured questionnaire. Over 90 questions were in- outside Singapore. All the cases occurred singly and cluded to elicit clinical and epidemiological infor- sporadically and were not clustered in any particular mation such as intake of different food items, food locality. No secondary cases were identified in the handling and personal hygiene practices in the kitchen and contact with household pets with diar- rhoea. For each notified case, 2-3 controls compris- The main presenting clinical symptoms of 19 ing children of the same age group (within 6 months cases investigated were watery diarrhoea (100%), of the age of the case), gender and ethnic group liv- fever (78.9%), vomiting (52.6%) and abdominal ing in the same neighbourhood, and with no recent cramps (26.3%). About 58% had bloody stool. Sev- travel history and gastro-intestinal symptoms during enteen of them were hospitalised and 2 were treated the previous 2 weeks, were selected and interviewed.
as outpatients. No death was reported.
The questionnaire covered 3 days preceding the on- Results of the case-control study based on 19 set of symptoms of the cases, and for the controls, 3 cases and 55 controls implicated porridge with “ikan bilis” (dried anchovy) as the vehicle of transmission Samples of milk powder, cereal and other food (p<0.01). No other food items or risk factors were items were obtained from the homes of the cases and retail outlets, and submitted to the Food and Water Laboratory, Singapore General Hospital, for isola- Age-gender distribution of 33 reported cases of
S. typhimurium phage type 104L, Singapore
Age group
Differences in proportion between cases and controls were examined using chi-square or Fischer’s exact test; a p-value of <0.05 was considered to be During the period 13 July – 17 October 2000, a total of 33 isolates of S. typhimurium of the same R-type ACGSTS3 and of the same phage type 104L were identified. Their PFGE patterns were indistin- guishable. Of the isolates, 17 were detected in July, None of the food samples taken from the homes Comments
of 6 cases, including one sample of grounded dried Periodic outbreaks of salmonellosis caused by anchovy, were positive for Salmonella species. Sal- multidrug–resistant strains occurred periodically in monella group E was isolated from one of the 16 sam- Singapore: S. typhimurium in 1971-1997, S. ples of dried anchovies subsequently purchased from orainberg in 1978-1979, and S. blockley in 1983.
the retail outlets. However, further samples collected However, the vehicle of transmission could not be were repeatedly free from Salmonella contamination.
determined. The predominant serotypes in 1999 were Results of matched case-control analysis in an outbreak of Salmonella typhimurium PT104L, Jul to Oct 2000
S. enteritidis (20.3%), S. stanley (12.8%) and S. method of processing “ikan bilis” is subject to gross weltevreden (10.8%), followed by S. typhimurium environmental contamination, including excreta of birds, rats and flies. After processing, the dried sea- food was packed in gunny sacks and exported. It was The risk factors for S. typhimurium DT104 in- transported by container trucks, fishing boats or lor- fection in developed countries include contact with ries to Singapore. Further contamination could have ill farm animals and consumption of chicken, pork occurred during transport, storage and display at re- sausage and meat paste. Consumption of contami- tail outlets where it was usually sold without proper nated beef, turkey and raw-milk cheese has also been The dried anchovy is a rich source of calcium This outbreak of S. typhimurium DT104L was and protein and is a popular ingredient for the prepa- associated with the consumption of grounded “ikan ration of a variety of foods, including soup stock. It bilis” (dried anchovies). However, the same strain is commonly deep fried and served with chilli. If used was not detected from samples taken from the retail as an infant feed, the common practice is to ground it outlets, although another serogroup (Salmonella and then cooked with porridge. In this outbreak, it was found that in the households where cases had oc- curred, the “ikan bilis” was first grounded and stored Salmonella is one of the most prevalent enteric in a container at room temperature for subsequent use.
pathogens encountered in seafood. It has been iso- It was either sprinkled onto or added to freshly cooked lated from ready-to-eat imported seafood such as porridge, instead of boiling with the porridge, and cooked shrimp, shellfish, fish paste, smoked fish, salted dried fish and caviar in the US. Outbreaks of salmonellosis caused by ingestion of contaminated This is an isolated incident believed to be due cuttlefish chips snack have been reported in Japan.
to a batch of contaminated “ikan bilis” imported into the country. The dried anchovy should be thoroughly In Singapore, the “ikan bilis” was imported cooked before consumption. The practice of sprin- from Thailand, Vietnam, Malaysia and Indonesia and kling or adding grounded “ikan bilis” onto cooked sold at retail outlets throughout the country. The porridge should be discouraged as the temperature small anchovies caught in fishing villages in these attained would not be adequate to destroy the Salmo- countries were lightly salted and dried outdoor. This The infectious disease situation in 2000
The infectious disease situation in Singapore A high level of vigilance on the disease activity was closely monitored through a well-established was also maintained on emerging infectious diseases system of epidemiological surveillance.
throughout the world to prevent their introduction into Singapore and to deal with them swiftly and effec- (82.4%) of 17 cases of hepatitis E were classified as tively should they be detected. On 1 October 2000, three infectious diseases were made legally notifiable, viz. hand, foot and mouth disease, legionellosis and A total of 213 notifications of food poisoning involving 1,542 cases were reported. A water-borne outbreak of 122 cases occurred in a shopping, office The trend of vector-borne, food-borne and vac- and residential complex at Bukit Timah.
cine-preventable diseases is shown in Fig. 1. The incidence of Campylobacter enteritis de- creased from 344 cases in 1999 to 231 cases in 2000.
Vector-borne diseases
The incidence rate was highest in children below the There was a marked decrease in the incidence of dengue fever (DF)/dengue haemorrhagic fever Air-borne diseases
(DHF) from 1,355 cases in 1999 to 673 cases in 2000.
One death (imported case) was reported. Most of the There were 509,966 attendances at government cases occurred in the south-eastern and north-eastern outpatient clinics for acute respiratory illnesses and 26,077 attendances for conjunctivitis. The incidence of chickenpox decreased from 31,592 cases in 1999 to A total of 266 cases of malaria were reported.
24,074 cases in 2000. Mumps also declined from 6,384 Majority (99%) of the cases were imported, mainly cases in 1999 to 5,981 cases in 2000 and rubella from from the Indian subcontinent and Southeast Asia. No 432 cases in 1999 to 312 cases in 2000. However, the case of Japanese encephalitis was reported.
incidence of measles increased from 65 cases in 1999 to 141 cases in 2000. No local cases of diphtheria or Food-borne diseases
The incidence of cholera remained low with 7 Environment-related diseases
indigenous and 3 imported cases reported.
A total of 55 cases of legionellosis and 67 cases The incidence of indigenous typhoid and para- of melioidosis were reported. Those at higher risk typhoid was also low with 14 and 2 cases reported, respectively. Majority of the notified cases of ty- phoid (82.5%) and paratyphoid (90.5%) were im- Hand, foot and mouth disease
A cluster of four deaths clinically related to There were 13 indigenous cases of hepatitis A hand, foot and mouth disease occurred in Aug and and 3 indigenous cases of hepatitis E cases. 64 Sep. Closure of all preschool centres effectively (83.1%) of 77 reported cases of hepatitis A and 14 Annual incidence rates of specified vector-borne, food-borne and vaccine-
preventable diseases in Singapore, 1991 - 2000
Vector-borne diseases
D e ng ue fe ve r/de ng ue ha e mo rrha g ic fe ve r
J a pa ne s e e nc e pha litis +
Food-borne diseases
T ypho id fe ve r
P a ra typho id fe ve r
He pa titis A
Vaccine-preventable diseases
D iphthe ria *
P o lio mye litis*
He pa titis B
* No local cases of diphtheria and poliomyelitis were reported during this period+ One imported case of Japanese encephalitis were reported in 1996, two imported cases in 1997, one imported case in 1998 and one imported case in 1999 MIX002/CMH/080101
Epidemiological News Bulletin readership survey
In May 2000, the Quarantine & Epidemiology a) How do you usually obtain the Epidemiologi-
Department of the Ministry of the Environment con- cal News Bulletin?
ducted an Epidemiological News Bulletin Readership Survey. The intent of the survey was to obtain feed- back from the readers in order to improve the rel- evance and quality of the information in the monthly bulletin. A total of 116 (3.4%) out of 3390 readers in the mailing list responded. These included private general practitioners, government and private hospi- tal physicians and health administrators. Readers b) How long do you usually take to read it?
from countries such as the USA and China also par- c) Do you circulate it to other members of your staff?
d) Which of the following categories of health
service do you belong to?
g) Topics which the respondents would like to be
in cluded:
• Regional statistics, epidemic news and trends • Treatment options/modalities available for • Identification and management of outbreaks e) Do you find the bulletin useful in your work?
• Information sheets on common conditions for h) General remarks:
f) How would you grade the usefulness of the
• “Extremely useful in providing local following regular features?
perspective on infectious disease. Goodsupplement to textbook.” i) Surveillance of specific infectious diseases • “Essential reading for all doctors, medical • “Very good work. Keep it up. Keep sending.” • “I find the bulletin useful and look forward to • “Excellent review - I always read it and refer to • “Like its small format” while others preferred ii) Monthly statistics of notifiable diseases “Email would be more convenient” “makeavailable on interactive website” • Requests for color photographs and more charts Cases of specified notifiable diseases, Republic of Singapore, February 2001
The data in this Bulletin are provisional, based on reports to the Quarantine & Epidemiology Department, Ministry of the Environment,and the Department of Clinical Epidemiology, Tan Tock Seng Hospital. Any comments or questions should be addressed to: Editorial Board
- Head, Quarantine & Epidemiology Department, Ministry of the Environment Scientific Advisory Committee :
Prof Tan Chorh Chuan - Director of Medical Services, Ministry of HealthProf Chan Soh Ha - Head, Department of Microbiology, National University of Singapore - Emeritus Consultant, Department of Pathology, Singapore General Hospital

Source: http://www.nea.gov.sg/cms/qed/enb03_01w.pdf