Öz

Bu çalışmada kalıntı miktarda antibiyotik içeren yeraltı sularına kısa süreli maruz bırakılan üç Salmonella enterica subsp. enterica serotipinin hastalık yapıcı özelliklerindeki değişiklikler ve hayatta kalabilme seviyeleri genel mikrobiyel fitnes çerçevesinde incelenmiştir. Serotipler gerçek bir salgından izole edilen kamçılı doğal fenotip Salmonella enterica ser. Typhimurium, kamçısı fonksiyonel olmayan bir başka Salmonella enterica ser. Typhimurium suşu ve kuş türlerinde salgına yol açan doğal fenotip Salmonella enterica ser. Pullorum’dan oluşup, iyon şiddeti değişken (3-30 mM) ve kalıntı miktarda antibiyotik içeren yeraltı suyuna 6-24 saat sürecince maruz bırakılmıştır. Serotiplerin hastalık yapıcı özellikleri in vitro koşullarda HEp2 türü insan epitel hücre kültürleri kullanılarak ölçülmüştür. Antibiyotik direnç seviyeleri ise yaygın kullanılan 10 antibitiyotiğe karşı disk difüzyon testi yardımıyla belirlenmiştir. Deneyler sonucunda S. enterica ser. Typhimurium suşlarında antibiyotik direnç seviyelerinde az miktarda artış gözlenirken S. enterica ser. Pullorum suşunda değişiklik gözlenmemiştir. In vitro deneylerde ise suşların HEp2 hücrelerini enfekte etmeleri zamanla önce azalmış, 24 saatlik dilim sonunda ise artmıştır. Sonuç olarak, kalıtsal antibiyotik içeren yeraltı sularına temas eden S. enterica serotiplerinin hastalık yapıcı karakterlerinin arttığı, antibiyotik direnç seviyelerinin suşa bağlı olarak değişkenlik gösterirken hayatta kalma oranlarının yüksek olduğu gözlenmiştir.

FITNESS AND PATHOGENICITY OF OUTBREAK CAUSING Salmonella UPON SHORT-TERM EXPOSURE TO GROUNDWATER WITH RESIDUAL ANTIBIOTICS

Abstract

The changes in survival and pathogenicity of three Salmonella enterica subsp. enterica serotypes upon short term exposure to groundwater with residual antibiotics have been studied in relationship to overall microbial fitness. A wild type flagellated Salmonella enterica ser. Typhimurium outbreak strain, a mutant Salmonella enterica ser. Typhimurium strain, and a wild type avian disease-causing Salmonella enterica ser. Pullorum strain were exposed to a range of ionic strength (3-30 mM) groundwater with residual antibiotics for 6-24 hours. Exposed organisms’ pathogenicity was tested in vitro exposure to a human epithelial cell line (HEp2). Resistance profiles against 10 common antibiotics were also tested and compared to unexposed controls. Results show minor antibiotic resistance changes for S. enterica ser. Typhimurium strains in response to some antibiotic classes mediated with active efflux pumps. This trend was not observed for S. enterica ser. Pullorum, suggesting that resistance found in groundwater exposed organisms might be strain-dependent. In vitro epithelial cell invasion assays showed bacterial invasion of HEp2 cells initially decreases with time and increases after 24 hours. It is concluded that S. enterica serotypes reaching groundwater environments in the presence of residual antibiotics may exhibit increased levels of pathogenicity, strain-dependent resistance to antibiotics, and sustained levels of viability.

Keywords

• Salmonella,antibiotic resistance,invasion,groundwater,pathogenicity

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