β-Lactamases, transferable quinolone resistance determinants, and class 1 integron-mediated antimicrobial resistance in human clinical Salmonella enterica isolates of non-Typhimurium serotypes

Abstract

This work investigates the occurrence and features of class 1 integrons and the presence of transferable quinolone resistance determinants (TQRD) among 382 clinical Salmonella enterica isolates of non-Typhimurium serotypes as well as the β-lactamases produced by amoxicillin-resistant isolates. These isolates were recovered in 2001 and from 2004 to 2009 from patients from the health region of Terres de l'Ebre (Catalonia, Spain) and comprised 41 different serotypes, mostly of serovar Enteritidis (n=272), being 16.5% multidrug-resistant (MDR). Among the 93 amoxicillin-resistant isolates, 84 produced TEM-1,4 produced an extended-spectrum β-lactamase (CTX-M-9 in one S. Grumpensis and in one S. Virchow, CTX-M-15 in S. Kapemba, and SHV-12 in S. Enteritidis), one produced DHA-1 (S. Newport), and 4 did not present any of the investigated β-lactamases. TQRD were found in 2 isolates (qnrA1 in CTX-M-9-producing S. Grumpensis and qnrB4 in DHA-1-producing S. Newport). Overall, 35 isolates (9.2% of all isolates and 54% of MDR isolates) belonging to 15 different serotypes carried class 1 integrons that were transferred by conjugation in 17 isolates. Eleven distinct cassette arrangements were identified, with dfrA1-aadA1, dfrA17-aadA5, and dfrA12-orfF-aadA2 being the most prevalent and widely distributed ones. Atypical sul3-associated integrons were detected in 5 isolates of serotypes Rissen and Enteritidis. Moreover, the presence of integrons in the serotypes Kapemba, Mikawasima, and [9,12:Iv:i:-], of the estX-psp (linked to sul3) and aadA13-sat cassette arrangements in S. enterica, of extended-spectrum β-lactamases in S. Kapemba and S. Grumpensis, and of TQRD in S. Grumpensis is reported here for the first time.