Salmonella Typhimurium BETWEEN 2000 AND 2012: ANTIMICROBIAL RESISTANCE AND PFGE PATTERNS OF ISOLATES FROM ANIMALS, HUMANS AND FOOD

Jasna Mičunović, Mateja Pate, Jana Avberšek, Matjaž Ocepek

Abstract


Salmonella Typhimurium is an important zoonotic pathogen with high levels of antimicrobial resistance. In the present study, we compared the pulsed-field gel electrophoresis (PFGE) and antimicrobial resistance patterns of 275 S. Typhimurium isolates collected between 2000 and 2012: 93 from humans, 111 from animals and 71 from food. A high rate of antimicrobial resistance was detected (71.6%). Multidrug resistance (MDR), defined as phenotypic resistance to three or more antimicrobial classes, was detected in more than half of the isolates (54.9%). The proportion of MDR isolates was the highest in animals (43%), followed by food (30.5%) and humans (26.5%). Among 27 phenotypically determined resistance patterns, three were found to be most common: ACNaSuT (19.3%), ACSuT (12%) and ASuT (11.3%). The first two patterns were the most prevalent in animal isolates (47.2% and 51.5%, respectively), while ASuT isolates were most commonly obtained from humans (58.1%). Macrorestriction with XbaI revealed 72 pulsotypes in nine clusters (A to I) and 19 unique pulsotypes (X1-X19). By far largest cluster F with 29 pulsotypes comprised 58.2% of tested isolates and included 53.8% animal, 26.3% food and 20% human isolates. Two thirds (66.3%) of the isolates in this cluster were MDR. The second largest was cluster E with 11.4% isolates of 12 pulsotypes, including 59.4% human, 31.3% food and 9.4% animal isolates. MDR was detected in 78.1% isolates with the most prevalent resistance pattern ASuT. Cluster I (16 isolates, 2 genotypes) consisted of 87.5% human and 12.5% animal isolates. The majority of these isolates (81.3%) were sensitive to tested antimicrobials and MDR isolates (12.5%) were of ASuT resistance pattern. This work provided valuable data about resistance and PFGE patterns of S. Typhimurium isolates in Slovenia and as global knowledge is essential for improved surveillance of the infections, the data obtained could serve as a base for both national and multistate outbreak investigations.

Key words: Salmonella Typhimurium; human; animal; food; PFGE; antimicrobial resistance


Salmonella Typhimurium MED LETOMA 2000 IN 2012: VZORCI ODPORNOSTI PROTI PROTIMIKROBNIM ZDRAVILOM IN VZORCI PFGE IZOLATOV IZ ŽIVALI, LJUDI IN ŽIVIL 

Povzetek: Salmonella Typhimurium je pomembna povzroÄiteljica zoonoz, pri katerih se pojavlja visok odstotek proti protimikrobnim zdravilom odpornih sevov. V raziskavi smo primerjali restrikcijske vzorce, pridobljene z metodo elektroforeze v pulzirajoÄem elektriÄnem polju (PFGE), in vzorce odpornosti 275 izolatov S. Typhimurium, izoliranih med letoma 2000 in 2012 iz 93 ljudi, 111 živali in 71 vzorcev hrane. Dokazali smo visok odstotek odpornih sevov (71,6 %). Odpornost proti trem ali veÄ skupinam protimikrobnih zdravil (VOB) smo ugotovili pri veÄ kot polovici izolatov (54,9 %). NajveÄ VOB izolatov smo ugotovili pri živalih (43 %), sledita hrana (30,5 %) in ljudje (26,5 %). Med 27 fenotipskimi vzorci odpornosti so bili najpogostejÅ¡i trije: ACNaSuT (19,3 %), ACSuT (12 %) in ASuT (11,3 %). Prva dva vzorca sta bila najpogostejÅ¡a pri živalih (47,2 % in 51,5 %), medtem ko so bili izolati z vzorcem ASuT najpogosteje dokazani pri ljudeh (58,1 %). Na podlagi makrorestrikcije z encimom XbaI smo ugotovili 72 vzorcev PFGE, razvrÅ¡Äenih v devet genetskih skupin (A – I), in 19 edinstvenih vzorcev (X1 – X19). NajveÄja je bila genetska skupina F z 29 vzorci, ki so predstavljali 58,2 % vseh izolatov (53,8 % iz živali, 26,3 % iz hrane in 20 % iz ljudi). Dve tretjini (66,3 %) izolatov v genetski skupini sta bili VOB. Druga najveÄja je bila genetska skupina E z 11,4 % vseh izolatov (12 vzorcev PFGE), od tega 59,4 % iz ljudi, 31,3 % iz hrane in 9,4 % iz živali. VOB je bila dokazana pri 78,1 % izolatov z najpogostejÅ¡im vzorcem odpornosti ASuT. V genetski skupini I (16 izolatov, 2 genotipa) je bilo 87,5 % izolatov iz ljudi in 12,5 % izolatov iz živali. VeÄina teh izolatov (81,3 %) je bila obÄutljiva na vsa testirana protimikrobna zdravila, medtem ko so izolati VOB (12,5 %) imeli vzorec ASuT. V raziskavi smo pridobili dragocene podatke o odpornosti in vzorcih PFGE bakterije S. Typhimurium na nacionalni ravni. Za uspeÅ¡en nadzor izbruhov je zelo pomembno globalno poznavanje te tematike, zato so podatki iz te raziskave pomemben prispevek k nacionalnemu in mednarodnemu preiskovanju izbruhov.

KljuÄne besede: Salmonella Typhimurium; Älovek; žival; hrana; PFGE; odpornost


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DOI: https://doi.org/10.26873/SVR-465-2017

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