Global Foodborne Infections Network (GFN) National and Regional Projects
Through interaction with participants during and after training courses, many interesting issues come up. Occasionally, these issues are pursued by a small coalition of participants and steering committee members and lead to focused regional or national projects.
Molecular epidemiology of Salmonella enterica serovar Kedougou from Thailand, USA and UK and associated risk factors with human salmonellosis in Thailand
As it is unclear which risk factors may be underlying the prevalence of S. Kedougou in Thailand, the objective of this study was to evaluate age, season, gender, specimen, and geographical location as possible risk factors associated to the presence of this serovar and determine if these were significantly different to other non-typhoid Salmonella (NTS). In addition, antimicrobial susceptibility testing (AST) and pulsed field gel electrophoresis (PFGE) was carried out in strains causing infections in Thailand (n=67), and profiles were compared to those isolated from humans in the United States of America (n=5) and to non-human reservoirs obtained from the United Kingdom of Great Britain and Northern Ireland (n=20) together with one isolate from an African chimpanzee. A total of 66.6% of the S. Kedougou isolates were multi-drug resistant (at least three different classes of antimicrobials). Furthermore, three strains recovered from human stool in Thailand were resistant to third generation cephalosporins. Analysis of the sequences showed the presence of CTX M-63 together with TEM 1b in two of the strains, whereas the third harbored TEM 1b. PFGE analysis showed 46 different macrorestriction profiles. Isolates obtained from human samples in Thailand and the United States of America presented the same PFGE-profile. Interestingly, one of the strains isolated from turkey clustered together with two of the human isolates causing infections in Thailand. The logistic analysis revealed season (p = 0.01), region of Thailand (p < 0.001) and specimen (p < 0.001) as significant risk factors associated to the presence of S. Kedougou when compared to other NTS. To our knowledge this is the first epidemiological report that describes the risk factors, prevalence, molecular epidemiology and antimicrobial resistance patterns of S. Kedougou in Thailand. This knowledge may facilitate the recognition and control of S. Kedougou as a new and emerging pathogen in the affected areas and it may help to establish intervention measures to reduce burden of infection due to the presence of this serovar.
Antimicrobial resistance of Salmonella in the lower central region of Thailand
The study was to elucidate the epidemiological trends and antimicrobial susceptibility of Salmonella serovars among Thai patients and asymptomatic carriers during 2001 to 2006 in the lower central region of Thailand. A total of 1401 human and 247 non-human isolates from various sources were included. The isolates were characterized using serotyping and antimicrobial susceptibility testing. The most common serovars in patients submitting stool samples were S. Weltevreden, S. Stanley, S. Anatum, and S. Rissen, respectively. A significant higher odds ratios of blood samples compared to patient stool were observed for S. Choleraesuis, S. Enteritidis, S. Typhimurium and S. Typhi. Children in the age group of up to five years of age suffered most frequently from gastroenteritis. The patients most common infected with an invasive serovar was children and people from 26 to 55 years of age. Antimicrobial susceptibility data revealed that S. Schwarzengrund, S. Choleraesuis, S. Anatum, S. Stanley, S. Rissen and S. Typhimurium were the serovars where most resistance was observed. The invasive serovar; S. Choleraesuis conferred resistance to cefotaxime and norfloxacin. Antimicrobial resistance to third generation cephalosporins was also observed in S. Agona, S. Rissen, S. Typhimurium, S. Anatum and S. Weltevreden.
An alarmingly high frequency of resistance to third generation cephalosporins was observed which need attention. We recommend the Thai authorities to take action in order to prevent and control the spread of invasive S. Choleraesuis and other serovars among animals and humans by enforcing a more strict policy on the usage of antimicrobials in food animals.
ESBL producing S. Choleraesuis in Thailand
The objective of this study was to characterize extended spectrum cephalosporinase (ESC) producing isolates of Salmonella serovar Choleraesuis recovered from patients in Thailand and Denmark.
Twenty-four blood culture isolates from 22 patients were included in the study of which 23 isolates were recovered from 21 Thai patients during 2003, 2007 or 2008 and one isolate was recovered from a Danish traveller to Thailand. ESC production was confirmed in 13 out of the 24 isolates by minimum inhibitory concentration (MIC) testing. Micro-array and plasmid profiling (replicon typing and restriction fragment length polymorphism (RFLP)) were used to characterize the genetic mechanisms of antimicrobial resistance in the 13 ESC producing isolates. Pulsed Field Gel Electrophoresis (PFGE) and MIC testing was used to compare the clonality between the 13 ESC producing isolates and the 11 non-ESC producing isolates.
Based on susceptibility patterns, the ESC producing isolates were more related than non-ESC producing isolates. Micro-array, PCR, plasmid profiling and replicon typing revealed that the 13 ESC producing isolates harboring either blaCMY-2 containing incA/C or blaCTX-M-14 containing incFIIA, incFrepB, and an unknown replicon located on plasmids ranging in size from 75–200 kb. The RFLP and replicon typing clustered the isolates into four distinct groups. PFGE revealed 16 unique patterns and five clusters; each cluster contained two to three of the 24 isolates. The isolate from the Danish patient was indistinguishable from two Thai clinical isolates by PFGE.
This study revealed the emergence of the blaCTX-M-14 gene among several clones of Salmonella serovar Choleraesuis. Numerous plasmids were identified containing up to two different ESC genes and four distinct replicons. A "travel associated" spread was confirmed. Overall, a high degree of clonal diversity between isolates resistant and susceptible to cephalosporins was observed. The findings represent a serious threat to public health for the Thai people and tourists.
Antimicrobial resistance in Salmonella from Turkey
Thirty-eight Salmonella Enteritidis isolates from chickens and chicken meat in Turkey were examined for antimicrobial susceptibility, XbaI pulsed-field gel electrophoresis (PFGE) patterns, phage types, plasmid profiles, and resistance genes. Seven different PFGE patterns were observed, with the most common accounting for 71% (X1). The most common phage type was PT4, followed by PT7, PT16, PT1, PT6, and PT35. Different phage types shared the same PFGE pattern. Twenty-one isolates were susceptible to all antimicrobial agents tested whereas eight were resistant to two or more antimicrobials. Six isolates were resistant to gentamicin, spectinomycin, streptomycin, and sulphamethoxazole and one of these in addition to nalidixic acid. Two isolates were resistant to ampicillin and nalidixic acid. An additional nine isolates were resistant to nalidixic acid only. All six streptomycin-resistant isolates had aadA located in an integron class 1 structure. Both ampicillin-resistant isolates had the blaTEM gene. Five different plasmid profiles were found among the isolates. Sixty-five percent of isolates contained a single plasmid with an approximate size of 55–60 kb. Plasmid profiling confirmed the PFGE pattern. Foodborne Pathogens and Disease. April 2009, Vol. 6, No. 3: 265-271.
Salmonella risk factors in Thailand
We conducted a retrospective observational study to assess epidemiological trends and risk factors associated with the 10 most common Salmonella serovars isolated from humans in Thailand between 2002 and 2007. A total of 11 656 Salmonella isolates covering all 6 years were included in the study. The top 10 Salmonella serovars identified during the course of this study were Enteritidis, Stanley, Weltevreden, Rissen, I ,4,,12:i:-, Choleraesuis, Anatum, Typhimurium, Corvallis and Panama, which accounted for 8108 (69.6%) of the isolates. Most isolates were from patients <5 years (33%), were isolated during June (13%), and were recovered from stool (82%) and from patients in Bangkok (27%). Statistical analysis revealed that S. Enteritidis and S. Choleraesuis were recovered from blood with a higher frequency than other nontyphoidal serovars. While both serovars tended to be isolated from patients >5 years; S. Choleraesuis was recovered with a higher frequency from patients in Bangkok and the central region, whereas S. Enteritidis was recovered predominantly from patients in the southern region. This study also indicates a shift in prevalence of the most common Salmonella serovars responsible for human infections in Thailand compared to previous studies. Notably, there was an increase in human infections with S. Stanley, S. Corvallis, and S. Choleraesuis, three serovars that have previously been associated with swine, and a decrease in infections due to S. Weltevreden and S. Anatum. The study also revealed differences in the epidemiology among the different serovars, suggesting that serovar-specific interventions are needed. We recommend initiating targeted interventions for the two serovars associated with a high odds ratio for submitted blood samples, S. Enteritidis and S. Choleraesuis. The authors also recommend additional epidemiologic studies to investigate the observed increase in swine associated serovars (S. Stanley, S. Corvallis and S. Choleraesuis) and determine interventions to reduce the burden of disease from these serovars. Foodborne Pathog Dis. 2009 Oct; 6 (8): 1009-19.
Outbreak detection in Mauritius
We report the first outbreak of salmonellosis caused by consumption of contaminated marlin mousse. Between 29 October and 5 November 2008, at least 53 persons developed diarrhoeal illness, all with a history of eating marlin mousse. Salmonella spp. that did not produce gas from glucose was isolated from stools of 26 affected patients and blood culture from one patient. Salmonella sp. isolates with the same phenotype were isolated in three samples of marlin mousse manufactured on 27 October 2008. The constituents of the mousse were smoked marlin, raw eggs, bovine gelatin, oil and cream. A laboratory investigation of one sample of marlin mousse manufactured 3 days later, and the individual ingredients sampled a week after production of the contaminated batch were all negative for Salmonella. Serotyping and minimum inhibitory concentration determination were performed on 12 patient isolates related to the outbreak and two mousse isolates. All isolates belonged to Salmonella serovar Typhimurium and were pansusceptible to all antimicrobials tested. Pulsed-field gel electrophoresis revealed that all the isolates were indistinguishable, thus implicating the mousse as the vehicle of the outbreak. Foodborne Pathogens and Disease July 2009, Vol. 6, No. 6: 739-741.
Democratic Republic of the Congo project
Salmonella serotyping and antimicrobial susceptibility testing were performed on 28 isolates sent to the Danish Institute for Food and Veterinary Research in 2002. A poster presentation of the project was submitted and accepted at the 15th European Congress of Clinical Microbiology and Infectious Diseases in Copenhagen, Denmark, in 2005.
Reference: 2008. Antimicrobial Susceptibility of Bacterial Enteric Pathogens Isolated in Humans from 2002 to 2004 in the Province of South–Kivu, Democratic Republic of Congo (submitted).
Reference: Microbiologcal and clinical features of Salmonella species isolated from bacteremic children in eastern Democratic republic of Congo Pediatr Infect Dis J. 2010 June.