Molecular analysis of Shiga toxin-producing Escherichia coli O157:H7 and non-O157 strains isolated from calves

Antibiotic Resistance and Genomic Analysis of Shiga Toxin-Producing Escherichia coli from Dairy Cattle, Raw Milk, and Farm Environment in Shaanxi Province, China

To investigate the epidemiology of Shiga toxin-producing Escherichia coli (STEC) in dairy cattle, 975 samples (185 feces, 34 silage, 36 cattle drinking water, 360 raw milk, and 360 teat skin swabs) were collected from two dairy farms in Baoji and Yangling, Shaanxi Province, China, and were screened for STEC. Whole-genome sequencing was used to analyze the genomic characteristics and potential transmission of STEC isolates. A total of 32 samples were contaminated with STEC, including 4.0% (19/479) in Farm A and 2.6% (13/496) in Farm B. Compared with adult cows (4.5%), nonadult cows had a higher rate (21.3%) of STEC colonization. A total of 14 serotypes and 11 multilocus sequence typing were identified in 32 STEC isolates, among which O55:H12 (25.0%) and ST101 (31.3%) were the most predominant, respectively. Six stx subtypes/combinations were identified, including stx1a (53.1%), stx2g (15.6%), stx2d, stx2a+stx2d, stx1a+stx2a (6.3%, for each), and stx2a (3.1%). Of 32 STEC isolates, 159 virulence genes and 27 antibiotic resistance genes were detected. Overall, STEC isolates showed low levels of resistance to the 16 antibiotics tested (0-40.6%), with most common resistance to ampicillin (40.6%). The phylogenetic analysis confirmed that STEC in the gut of cattle can be transmitted through feces. The results of this study help to improve our understanding of the epidemiological aspects of STEC in dairy cattle and provide early warning and control of the prevalence and spread of the bacterium.

Virulence factors, serogroups, and antibiotic resistance of Shiga-toxin producing Escherichia coli from raw beef, chicken meat, and vegetables in Southwest Iran

Background

Shiga-toxin-producing Escherichia coli (STEC) is an important food-borne pathogen causing human diseases with severe symptoms. Although the O157 serotype has been mostly isolated from human specimens, the increasing incidence rates of non-O157 serogroups have attracted special attention in recent years.

Aims

Evaluation of the epidemiology and identification of different characteristics of STEC isolates from raw beef, chicken meat, and vegetable samples in Shiraz, Southwest Iran.

Methods

Two hundred beef and chicken meat samples from different parts of carcasses and four hundred vegetable samples (carrots, lettuce, cucumber, and leafy greens) were randomly taken; STEC were isolated and confirmed using standard microbiological methods. Antimicrobial susceptibility testing (AST) was performed using the Kirby-Bauer disc diffusion method. Polymerase chain reaction (PCR) was used for the identification of O-serogroups, virulence, and antibiotic resistance genes.

Results

52% of beef, 8% of chicken, and 7.2% of vegetable samples were STEC-positive. Further, the highest frequency of virulence factors belonged to the co-existence of stx1 and stx2. O157 serogroup was only detected in beef (3.8%) and lettuce (16.6%) isolates, while the rates of the non-O157 serogroups were relatively high (up to 44.2%). The highest resistance rate in the STEC isolates of different samples belonged to nalidixic acid (62.5%), tetracycline (55.7%), and ampicillin (48%).

Conclusion

Paying more attention to non-O157 serogroups in future studies is recommended due to the relatively high prevalence of theses STEC serogroups in our study. Besides, the high level of resistance to some antibiotics observed in this study needs to be addressed.

Prevalence of class 1 integron in Escherichia coli isolated from animal sources in Iran: a systematic review and meta-analysis

Background

Among the genetic elements, integrons may contribute to the widespread incidence and spreading of antibiotic resistance among Escherichia coli isolates. Accordingly, this review aims to investigate the prevalence of class 1 integron in E. coli isolated from animal sources in Iran.

Methods

This systematic literature search was performed from January 1, 2000 to the end of May 1, 2019.

Then, publications that met our inclusion criteria were selected for data extraction and analysis. Also, the quality of included studies was independently assessed by two researchers based on the Joanna Briggs Institute. Meta-analysis was performed by the Comprehensive Meta-Analysis (CMA) software using the random effects model, Cochran’s Q, and I² tests. Publication bias was estimated by funnel plot and Egger’s linear regression test.

Results

Based on inclusion criteria, five studies were included to meta-analysis. From those studies, the pooled prevalence of integrons was 33% (95% CI, 23.8–43.7%) ranging from 23.8 to 52.4%. There was a significant heterogeneity among the 5 studies (χ² = 11.73; p < 0.019; I² = 65.91%). Additionally, Begg’s and Egger’s tests were performed to quantitatively evaluate the publication biases. According to the results of Begg’s test (z = 1.22, p = 0.22) and Egger’s test (t = 3.03, p = 0.056), a significant publication bias was not observed.

Conclusions

Our finding revealed the relatively high prevalence of class 1 integrons among E. coli isolates. Moreover, there was a significant heterogeneity among studies and subgroup analysis also showed that there was no difference about prevalence of class 1 integrons among different sample source.