• Antibiotic resistance, integrons and Salmonella genomic island 1 among non-typhoidal Salmonella serovars in The Netherlands.

      Vo, An T T; Duijkeren, Engeline van; Fluit, Ad C; Wannet, Wim J B; Verbruggen, Anjo J; Maas, Henny M E; Gaastra, Wim (2006-09-01)
      The objective of this study was to investigate the antimicrobial resistance patterns, integron characteristics and gene cassettes as well as the presence of Salmonella genomic island 1 (SGI1) in non-typhoidal Salmonella (NTS) isolates from human and animal origin. Epidemiologically unrelated Dutch NTS strains (n=237) originating from food-producing animals and human cases of salmonellosis were tested for their susceptibility to 15 antimicrobial agents. Resistance to 14 of these antimicrobials, including the third-generation cephalosporins, was detected. Resistance to sulphonamides, ampicillin, tetracycline, streptomycin, trimethoprim and nalidixic acid was common (>/=10% of the strains were resistant). Resistance against three or more antimicrobials was observed in 57 isolates. The same 237 strains were studied for the prevalence of class 1 integrons, their gene cassettes and the presence of SGI1. Thirty-six isolates (15.2%) carried class 1 integrons. These integrons had ten distinct profiles based on the size of the integron and restriction fragment length polymorphism analysis. Integrons were detected for the first time in serovars Indiana and Senftenberg. Multidrug resistance was strongly associated with the presence of class 1 integrons in which the aadA2, aadA1, bla(PSE-1), dfrA1, dfrA5, dfrA14 or sat genes were present, as determined by nucleotide sequence determination. The presence of gene cassettes or combinations of gene cassettes not previously found in integrons in Salmonella was observed. SGI1 or its variants (SGI-B, -C and -F) were present in 16 isolates belonging to either serovar Typhimurium, Derby or Albany. Regardless of whether the isolate was of human or animal origin, the same resistance phenotype, integron profile and SGI1 structure could be observed.
    • Distribution of Salmonella enterica serovars from humans, livestock and meat in Vietnam and the dominance of Salmonella Typhimurium phage type 90.

      Vo, An T T; Duijkeren, Engeline van; Fluit, Ad C; Heck, Max E O C; Verbruggen, Anjo J; Maas, Henny M E; Gaastra, Wim (2006-03-10)
      Epidemiologically unrelated non-typhoid Salmonella isolates from humans (n = 56) and animal origin (n = 241, from faeces, carcasses and meat) in Vietnam were investigated. Salmonella Typhimurium, S. Anatum, S. Weltevreden, S. Emek, and S. Rissen were the most prevalent serovars. S. Typhimurium phage type 90 was predominant among S. Typhimurium isolates. The serotype and phage type distribution of the Salmonella isolates was different from that in Europe and America. Many sero- and phage types found in humans were also found in cattle, pigs, and poultry suggesting that food producing animals are an important source of human non-typhoid Salmonella infection in Vietnam.
    • Intensieve surveillance van Shigatoxine-producerende Escherichia coli O157 in Nederland, 2005

      Friesema, I H M; Jager, C M de; Heuvelink, A E; Zwaluw, W K van der; Maas, Henny M E; Pelt, W van; Wannet, Wim J B; Duynhoven, Yvonne T H P van (RIVM, 2006-08-01)
      Since January 1999, an enhanced surveillance of Shiga toxin-producing Escherichia coli (STEC) O157 has been implemented in the Netherlands. In 2005, 53 symptomatic patients were diagnosed with STEC O157. This was relatively high compared with the number in previous years (annually 36 to 57), due to a national outbreak with 21 patients involved. Of the patients, 33% were hospitalised, 8% developed the haemolytic-uraemic syndrome (exclusion of outbreak-cases: 13%), including one one-year-old boy who died. Consumption of raw or undercooked beef and contact with farm animals and manure are still most frequently mentioned by the patients as possible cause. In 2005, cluster analyses of the fingerprints of bacterial DNA from the STEC O157 isolates (by pulsed-field gel electrophoresis) nine times suggested a relationship between several patients. For three clusters this was supported by additional epidemiological information. One cluster, consisting of two sub clusters, comprises the national outbreak caused by filet américain, except for two patients who fell ill two and one month before this outbreak. Furthermore, one household cluster was identified for which an indistinguishable PFGE pattern was found in a manure isolate taken from their cattle. In addition, an isolate from one individual case could be matched with an isolate taken from their neighbours cattle. As other serogroups than O157 can cause serious illness, a collaboration between RIVM and eight medical microbiological laboratories to assess the relative importance of non-O157 serogroups was started in the Netherlands in the autumn of 2005.