Antibiotic resistance and molecular characterization of diarrheagenic Escherichia coli and non-typhoidal Salmonella strains isolated from infections in Southwest China

Abstract

BackgroundBacterial diarrhea is one of the most common causes for medical consultations, mortality and morbidity in the world. Diarrheagenic Escherichia coli (DEC) and non-typhoidal Salmonella (NTS) are major intestinal pathogens in developing countries, and the indiscriminate use of antibiotics has greatly contributed to resistant strains. Hence, the aim of the present study is to identify the antimicrobial resistance patterns and the molecular characteristics of DEC and NTS in southwest, China.Methods1121 diarrheal patients and 319 non-diarrheal subjects across all age groups were recruited from four sentinel hospitals from June 2014 to July 2015 in Kunming City, Yunnan Province. Each stool specimen was collected to detect DEC and NTS with standard microbiological and molecular methods. Antimicrobial resistance testing was performed with the Kirby-Bauer disk diffusion method, and the standards for antimicrobial susceptibility testing complied with the Clinical and Laboratory Standards Institute (CLSI). Molecular characterization of strains was carried out using pulsed-field gel electrophoresis (PFGE). A structured questionnaire was used to record basic epidemiological data (e.g. sex, age, residence, season, etc.). Data were analyzed using Chi-square or Fisher’s exact test.ResultsDEC was detected in 127 (11.33%) diarrhea cases and 9 (2.82%) non-diarrheal cases (χ2 = 20.69, P < 0.001, OR = 4.36, 95% CI: 2.19–8.65), and the prevalence of NTS isolated from diarrhea cases was higher than that of non-diarrheal cases across all age groups (n = 42, 3.75%, n = 1, 0.31%, χ2 = 10.10, P = 0.002, OR = 12.38, 95% CI: 1.70–90.29). The rates of resistance to ten antibiotics of DEC and NTS showed significant differences (χ2 = 386.77, P < 0.001; χ2 = 191.16, P < 0.001). The rates of resistance to Amoxicillin and Clavulafiate (AMC), Cephalothin (CEP), Gentamicin (GEN) and Sulfamethoxazole-Trimethoprim (SXT) of DEC isolated from diarrhea cases were higher than those of NTS isolated from diarrhea patients (37.01% vs 14.29%, χ2 = 7.57, P = 0.006; 29.92% vs 11.90%, χ2 = 5.40, P = 0.02; 37.01% vs 11.90%, χ2 = 5.80, P = 0.016; 62.20% vs 26.19%, χ2 = 16.44, P < 0.001; respectively). Ciprofloxacin (CIP) was the most sensitive antibiotic for DEC and NTS strains isolated from diarrhea cases. Resistance rates of DEC isolates from cases and controls to more than three kinds antimicrobials (multidrug resistance, MDR) showed no significant differences (81.10% vs 88.89%, P = 0.33). Pulsotype patterns of DEC strains were highly diverse; however, the pulsotype pattern of NTS strains was closely related to the serotype. The pattern of S. enteritidis was highly similar, but the S. enterica Typhimurium strain was discrete.ConclusionsAntibiotic resistance of Enterobacteriaceae is of great concern. The societal effects of antibiotic use justify strict monitoring to combat increases in antimicrobial resistance. Molecular epidemiology and systematic epidemiological investigation can provide accurate evidence for tracking the infection source.Electronic ...

Detection of Non-Typhoidal Salmonella Gastroenteritis in a Tertiary Children’s Hospital in China

“…In our study, S. enteritidis (29.6%) was the second common subtype identified among the NTS isolated from stool samples. A study from Southwest China reported S. enteritidis as the most predominant subtype identified, however with a much lower rate (1.87%) than that reported in our study (27). Another study from Venezuela reported that S. enteritidis (48.7%) as the predominant serovar followed by S. typhimurium (37.8%) which is contrary to our result where S. typhimurium was the most common subtype followed by S. enteritidis (25).…”

“…In our study, the prevalence of NTS was 10.1% and iNTS was 9.4%. A study from Northwest China reported NTS prevalence at a rate of 3.75% from the diarrheal patients and 0.31% from the non-diarrheal patients, which was much lower than that reported in our study (27). In contrast, studies from the US (42%) and Shangai (17.2%) reported NTS as the leading cause of bacterial enteric illness, which was much higher than that reported in our study (15,28).…”

“…Other studies from West Africa (31) and Malaysia (35) reported 100% susceptibility to ciprofloxacin. We reported that 41.3% of our isolates were resistant to cefotaxime, which was higher than that reported from India (32.5%) (22), Congo (2.1%) (33), Southwest China (11.9%) (27), and comparable to that reported from Iraq (42.4%) (23). Gentamicin resistance was reported to be 39.1% among our isolates, while studies from Ethiopia (7.5%) (34), Southwest China (11.9%) (27), reported lower and a study from India (40%) (22), reported a comparable rate of resistance to gentamicin.…”

“…We reported that 41.3% of our isolates were resistant to cefotaxime, which was higher than that reported from India (32.5%) (22), Congo (2.1%) (33), Southwest China (11.9%) (27), and comparable to that reported from Iraq (42.4%) (23). Gentamicin resistance was reported to be 39.1% among our isolates, while studies from Ethiopia (7.5%) (34), Southwest China (11.9%) (27), reported lower and a study from India (40%) (22), reported a comparable rate of resistance to gentamicin. Other antibiotics for which our isolates were found to be resistant included amoxicillin (34.8%), ampicillin (30.4%), co-trimoxazole (30.4%), amikacin (26.1%), and chloramphenicol (18.5%), a study from Congo reported lower rates of resistance to the abovementioned antibiotics (33).…”

“…An alarming increase in the antibiotic resistance by NTS was reported elsewhere (11,12). In our study, 54.3% of our isolates were found to be resistant to nalidixic acid, which is lower than that reported from India (77%) (22), Southwest China (66.7%) (27), and higher than that reported from Congo (4.3%) (33), Iraq (45.5%) (23), Ethiopia (23.9%) (34), and Iran (31.5%) (17). Among the NTS isolated from stool samples, Nalidixic acid was predominant among our NTS, (64.8%) which was very much higher than that reported from Kenya (6%) (16).…”