Objective To understand the elonal expansion and genetic diversity of Salmonella en-terica semtype Paratyphi A (SPA) and to construct a typing method to determine the epidemic clones of the isolates. Methods Antimicrobial susceptibility testing was performed with 3980 SPA isolates by the cen-trolled Kirby-Bauer disc diffusion technique on Muller-Hinton agar plates. A total of 15 SPA with nalidixie acid resistance for mutations in gyrA, gyrB, gyrC and gyrE genes within the quinolone-resistant determina-tion region (QRDR) were examined. Subtyping of 121 isolates of SPA from seven counties in Yuxi were studied using pulsed-field gel eleetrophoresis (PFGE) analysis following digestion of chromosomal DNA with restriction endanucleases Spe Ⅰ and Xba Ⅰ. PFGE patterns were analyzed by duster analysis. Results The nalidixic acid-susceptible isolates predominated in 1999 but was replaced by nalidixic acid -resistant (NAR) isolates after 2000. Amplification by PCR and sequencing of the genes with subsets of 15 NAR strains re-vealed that the resistance mechanisms had resulted from single point mutations in the gyrA gene. Spe Ⅰ and Xba Ⅰ digestion of 121 isolates gave five and four different PFGE patterns with the predominance of the Spe Ⅰ 01 and Spe Ⅰ 02 (or the Xba Ⅰ 01) epidemic patterns, respectively. Spe Ⅰ 01 and Spe Ⅰ 02 consisted of 37.2% and 57.9% of isolates, respectively, or Xba Ⅰ 01 consisted of 95.0% of isolates. Conclusion The incidence of resistance to nalidixic acid of the isolates increased during the study period. PFGE patterns Spe Ⅰ 01 and Spe Ⅰ 02 (or Xba Ⅰ 01), the main clones of the epidemics, are highly prevalent in Yuxi. PFGE with Spe Ⅰ and Xba Ⅰ is a useful technique to differentiate SPA.

OBJECTIVETo study the epidemiological characteristics and antibiotic resistance of Salmonella enterica serovar Pomona (S. Pomona).

METHODSAntimicrobial susceptible testing (AST) and pulsed field gel electrophoresis (PFGE) methods were used to analyze on S. Pomona strains that were isolated from diarrhea cases through the diarrhea network monitoring program, environment and food samples in Shanghai as well as from reptiles in Guangxi Zhuang Autonomous Region.

RESULTS4 553 clinic Salmonella (S.) strains were isolated from the Shanghai network laboratories from 2005 to 2012. The top 10 serotypes would include 20 serotypes all belonged to A-F groups, while S. Pomona was next to S. Wandsworth, according to the non- A-F groups. Young children seemed to be susceptible to S. Pomona, and might cause bloody stools and super-infection. The top 10 serotypes from 1 805 foodborne Salmonella strains were significantly more extensive than those from the human S. Pomona strains, followed by those rare serotypes which were mostly isolated from turtle, sea-shellfish and reptiles. Antibiotic resistance of S. Pomona strains from other sources were significantly more severe than those from human samples, and belonged to A and B clones by means of PFGE. Clone A strains were non-epidemic strains which showed multi-drug resistance (MDR) to antimicrobials. Clone B was the main epidemic-causing strain that not resistant to drugs, which consisting B- I from young-age-groups and B-II were from the seniors. B-I strains were homologous to those from shellfish, tortoises and lizards, while B-II strains only showing homology to those from shellfish. One S. Pomona strain-MDR, isolated from human was homologous to 8 antimicrobials.

CONCLUSIONS. Pomona was a quite common serotype among those rare serotypes, which showed higher pathogenicity to infants while genetic evolution might take place when comparing them with the strains isolated from the clinics in 2005. Surveillance programs should be intensified along with the early warnings systems on infections which were from seafood and reptiles.

China ; epidemiology ; Drug Resistance, Multiple, Bacterial ; Humans ; Molecular Epidemiology ; Salmonella Infections ; epidemiology ; microbiology ; Salmonella enterica ; classification ; isolation & purification ; Serogroup