Antimicrobial Resistance and Molecular Investigation of H2S-Negative Salmonella enterica subsp. enterica serovar Choleraesuis Isolates in China

Abstract

Salmonella enterica subsp. enterica serovar Choleraesuis is a highly invasive pathogen of swine that frequently causes serious outbreaks, in particular in Asia, and can also cause severe invasive disease in humans. In this study, 21 S. Choleraesuis isolates, detected from 21 patients with diarrhea in China between 2010 and 2011, were found to include 19 H2S-negative S. Choleraesuis isolates and two H2S-positive isolates. This is the first report of H2S-negative S. Choleraesuis isolated from humans. The majority of H2S-negative isolates exhibited high resistance to ampicillin, chloramphenicol, gentamicin, tetracycline, ticarcillin, and trimethoprim-sulfamethoxazole, but only six isolates were resistant to norfloxacin. In contrast, all of the isolates were sensitive to cephalosporins. Fifteen isolates were found to be multidrug resistant. In norfloxacin-resistant isolates, we detected mutations in the gyrA and parC genes and identified two new mutations in the parC gene. Pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and clustered regularly interspaced short palindromic repeat (CRISPR) analysis were employed to investigate the genetic relatedness of H2S-negative and H2S-positive S. Choleraesuis isolates. PFGE revealed two groups, with all 19 H2S-negative S. Choleraesuis isolates belonging to Group I and H2S-positive isolates belonging to Group II. By MLST analysis, the H2S-negative isolates were all found to belong to ST68 and H2S-positive isolates belong to ST145. By CRISPR analysis, no significant differences in CRISPR 1 were detected; however, one H2S-negative isolate was found to contain three new spacers in CRISPR 2. All 19 H2S-negative isolates also possessed a frame-shift mutation at position 760 of phsA gene compared with H2S-positive isolates, which may be responsible for the H2S-negative phenotype. Moreover, the 19 H2S-negative isolates have similar PFGE patterns and same mutation site in the phsA gene, these results indicated that these H2S-negative isolates may have been prevalent in China. These findings suggested that surveillance should be increased of H2S-negative S. Choleraesuis in China.

Antibiotic resistance and molecular characterization of the hydrogen sulfide-negative phenotype among diverse Salmonella serovars in China

“…Although a large number of H 2 S-negative Salmonella strains have been reported, their antibiotic resistance patterns were not clarified. Among the H 2 S-negative Salmonella identified in this study, S. Choleraesuis exhibited a high rate of antibiotic resistance, comprising 67% of MDR isolates; similar data on the MDR rate among H 2 S-negative S. Choleraesuis isolates were reported in Japan and in our previous study [ 7 , 14 ]. To the best of our knowledge, MDR has been previously detected only in H 2 S-negative S. Choleraesuis and S. Kentucky [ 6 , 7 ].…”

“…In many regions of the world, a high resistance rate to conventional antimicrobial agents has been reported for H 2 S-positive Salmonella [ 16 – 19 ] . Although H 2 S-negative Salmonella isolates may be highly sensitive to a multitude antibiotics owning to H 2 S defending bacteria against oxidative stress imposed by antibiotics [ 20 ], there is increasing evidence that high resistance rate to antibiotics was also observed in many H 2 S-negative Salmonella isolates [ 6 , 7 , 14 ]. Importantly, extended-spectrum cephalosporins and fluoroquinolones have been widely used as alternative agents for treatment of salmonellosis.…”

Molecular Characterization of Salmonella enterica Serovar Aberdeen Negative for H2S Production in China

“…Senftenberg isolates [ 13 ] and 19 H 2 S-negative S . Choleraesuis isolates were reported in our previously study [ 32 ]. Here, we identified seven H 2 S-negative S .…”

Salmonellosis outbreak archive in China: data collection and assembly

“…However, qualified datasets and knowledge gaps in SO remain significant rational policy-making barriers. Specifically, the scope of available studies is limited, as they fail to comprehensively represent the overall situation, including various serovars 21 , different regions 22 , multiple antimicrobial resistance 23 , and the diversity of animal-derived food sources 24 . Previous studies often focused on individual outbreak cases, employing epidemiological methods such as case-control studies and various biological tracing approaches 25 .…”