Antibiotic resistance, integrons and Salmonella genomic island 1 among Salmonella Schwarzengrund in broiler chicken and pig

Abstract

Salmonella Schwarzengrund is an infrequent serovar isolated from humans in Taiwan. However, this serovar
is which is highly invasive, is found in humans as report by two independent epidemiologic surveys. The
present study delineated the widespread resistance to fluoroquinolone in S. Schwarzengrund isolated from
both poultry and swine carcesses in Taiwan. We conducted the present study to investigate the prevalence
and characteristics of S. Schwarzengrund isolated from broiler chicken in central Taiwan. A total of 187 S.
Schwarzengrund isolates was gotten from slaughtered chicken and pigs in central Taiwan between June
2006 and March 2007. The percentages of resistance were as follows: ampicillin (90.74%), chloramphenicol
(69.75%), florfenicol (24.07%), streptomycin (91.98%), trimethoprim and sulfamethoxazole (91.36%), nalidixic
acid (96.30%), ciprofloxacin (8.02%), tetracycline (95.68%), amikacin (8.64%), ceftiofur (0.62%) and ceftriaxone
(0%). Four types of class 1 integrons were detected: 1.2 kb carried blaPSE-1, aadA2 gene (n = 2), 1.2 kb
carried blaPSE1, dfraA1 gene (n = 2), 1.0/1.2 kb carried blaPSE-1, aadA2 ( n = 2) and 1.9 kb carried dfrA12,
aadA2 gene (n = 152). XbaI-digested PFGE patterns generated related clusters implicated in the
dissemination of integron. Thirteen ciprofloxacin-resistant isolates were all detected in 5 identical mutations
in the QRDR of gyrA, parC and parE. Our results suggest that there is a risk of transmitting multidrug
resistant Salmonella between pig and chicken farms, and also suggest that there is a need to prevent the
transmission of this organism from a neighboring contaminated farm.