The occurrence of atypical enteropathogenic Escherichia coli strains among children with diarrhea in Iran

Molecular typing and prevalence of extended-spectrum β-lactamase genes in diarrhoeagenic Escherichia coli strains isolated from foods and humans in Mashhad, Iran

AIMS

Present study was aimed to determine ESBL-encoding genes distribution in Diarrhoeagenic Escherichia coli (DEC) isolated from animal-source food products and human clinical samples in Mashhad, Iran. The strains were also further studied to analyse genotypic diversity and find genetic relationships between them.

METHODS AND RESULTS

The number of 85 DEC strains including 52 and 33 strains isolated from 300 food and 520 human stool samples, respectively. Randomly amplified polymorphic DNA (RAPD), and repetitive extragenic palindromic-PCR (rep-PCR) typing methods were used to track their genetic relationships. The ESBL-encoding genes prevalence was approximately 70% in both groups of isolates. The bla_TEM , bla_CTX-M and bla_SHV were prevalent in 67·1, 20 and 10·6% of isolates, respectively. The ESBL-positives showed significantly higher resistance rates to gentamicin, co-trimoxazole, tetracycline, aztreonam and chloramphenicol (P < 0·05). Fingerprinting patterns-based dendrograms divided DEC strains into separate clusters irrespective of their sources and pathotypes. In typing field, rep-PCR provided more discriminatory power (Simpson's index of diversity (SID) = 0·925) than RAPD (SID = 0·812).

CONCLUSION

Molecular similarity between certain animal-sourced food products and clinical sample strains supported food-borne transmission routes for genotypic elements such as ESBL-encoding genes.

SIGNIFICANCE AND IMPACT OF THE STUDY

Findings emphasize the importance of resistance issues, the need to improve treatment guidelines and routine surveillance of hygienic measures during food processing.

Characterization of Antimicrobial Susceptibility, Extended-Spectrum β-Lactamase Genes and Phylogenetic Groups of Enteropathogenic Escherichia coli Isolated from Patients with Diarrhea

Objectives

Infectious diarrhea is one of the most common causes of pediatric death worldwide and enteropathogenic Escherichia coli (EPEC) is one of the main causes. There are 2 subgroups of EPEC, typical and atypical, based on the presence or absence of bundle forming pili (bfp), of which atypical EPEC is considered less virulent, but not less pathogenic. Antimicrobial resistance towards atypical EPEC among children is growing and is considered a major problem. In this study the pattern of antibiotic resistance in clinical isolates was determined.

Methods

Using 130 isolates, antibiotic resistance patterns and phenotypes were assessed, and genotypic profiles of extended spectrum β-lactamase (ESBL) production using disc diffusion and PCR was carried out. Phylogenetic groups were analyzed using quadruplex PCR.

Results

There were 65 E. coli isolates identified as atypical EPEC by PCR, among which the highest antibiotic resistance was towards ampicillin, followed by trimethoprim-sulfamethoxazole, and tetracycline. Multidrug resistance was detected in 44.6% of atypical EPEC isolates. Around 33% of isolates were determined to be extended spectrum β-lactamase producers, and in 90% of isolates, genes responsible for ESBL production could be detected. Moreover, the majority of atypical EPEC strains belonged to Group E, followed by Groups B1, B2 and C.

Conclusion

High rates of multidrug resistance and ESBL production among atypical EPEC isolates warrant periodical surveillance studies to select effective antibiotic treatment for patients. It is considered a critical step to manage antibiotic resistance by avoiding unnecessary prescriptions for antibiotics.

An overview of diarrheagenic Escherichia coli in Iran: A systematic review and meta-analysis

BACKGROUND

Diarrheagenic Escherichia coli (DEC) is a common enteric pathogen that causes a wide spectrum of gastrointestinal infections, particularly in developing countries. This is a systematic review and meta-analysis to determine the prevalence of DEC in various geographical regions in Iran.

MATERIALS AND METHODS

English (PubMed, Web of Science, Scopus, Embase, Cochrane Library, and Google Scholar) and Persian (IranMedex, SID, Magiran, and Iran Doc) databases were comprehensively searched from January 1990 to April 2017. Study selection and data extraction were performed by two independent reviewers. After assessing heterogeneity among studies, a random effects model was applied to estimate pooled prevalence. Data analyses were done with the Stata software (version 12.0). This meta-analysis was registered with PROSPERO, number CRD42017070411.

RESULTS

A total of 73 studies with 18068 isolates were eligible for inclusion within the meta-analysis. The results of random effects model showed that the most prevalent DEC pathotypes were enterotoxigenic E. coli (ETEC) (16%; 95% confidence interval [CI]: 11%-23%), enteroaggregative E. coli (11%; 95% CI: 8%-15%), atypical enteropathogenic E. coli (EPEC) (11%; 95% CI: 8%-14%), Shiga toxin-producing E. coli (9%; 95% CI: 6%-13%), diffuse adherent E. coli (6%; 95% CI: 6%-12%), enteroinvasive E. coli (4%; 95% CI: 2%-6%), and typical EPEC (3%; 95% CI: 1%-5%).

CONCLUSION

This study showed that DEC infections in the Iranian population have low frequency. Our data suggest that the ETEC pathotype can be regarded as one of the most important etiological agents of diarrhea in this country. However, the prevalence of DEC pathotypes is diverse in different regions of Iran.

Occurrence of multidrug-resistant and ESBL-producing atypical enteropathogenic Escherichia coli in China

Background

Atypical enteropathogenic Escherichia coli (aEPEC) is regarded as a globally emerging enteropathogen. aEPECs exhibit various level of resistance to a range of antibiotics, which is increasing alarmingly. The present study investigated the antimicrobial resistance of aEPEC isolates recovered from diarrheal patients, healthy carriers, animals, and raw meats.

Results

Among 267 aEPEC isolates, 146 (54.7%) were resistant to tetracycline, followed by ampicillin (49.4%), streptomycin (46.1%), and piperacillin (41.2%). Multidrug resistance (MDR) was detected in 128 (47.9%) isolates, and 40 MDR isolates were resistant to ≥ 10 antimicrobial agents. A total of 47 (17.6%) aEPEC isolates were identified as extended-spectrum β-lactamase (ESBL)-producers. The bla_CTX-M-14 and bla_CTX-M-15 genes were predominant among ESBL-producing isolates.

Conclusions

This investigation depicted the occurrence of multidrug-resistant and ESBL-producing aEPEC isolates in China. The results suggested that it is necessary to continuously monitor the emergence and spread of MDR aEPEC.

Electronic supplementary material

The online version of this article (10.1186/s13099-018-0234-0) contains supplementary material, which is available to authorized users.

The trend of enteropathogenic Escherichia coli towards atypical multidrug resistant genotypes

The aim of this study was to investigate the prevalence of multidrug resistance (MDR) in atypical enteropathogenic Escherichia coli (EPEC) genotypes among 547 diarrheal children. All E. coli isolates with eae⁺stx1^-stx2^- genotypes included in this study and atypical property of EPEC was characterized by the absence of Bundle-forming pili (bfpA gene). Bacterial pathogens were detected in 70 patients (12.8%) among which atypical EPEC (5.3%) were the most common. The higher resistance rate was seen to tetracycline (70%), cotrimoxazole (60%) and nalidixic acid (53.3%) related to MDR phenotype in 63.3% of isolates. The presence of class 1 and 2 integrons was 30% and 6.6% with the dominance of dfrA, aadA gene cassettes among the isolates. Eleven out of 21 phenotypically tetracycline-resistant isolates (52.38%) harboured one or two tetracycline resistance genes (A-D) which shows the incapability of known data to reasonable tetracycline resistance phenotypes among EPEC isolates. A high level of genotypic diversity was seen among the isolates by Pulsed-field gel electrophoresis method which ranged from 89.7 to 29% and no clear correlation was obtained between tetracycline resistance or integron carriage and specific pulsotypes. In conclusion, the data presented here add to knowledge about the heterogeneous nature of MDR EPEC population in Iran which has a growing tendency towards atypical genotypes. The distribution of integrons among EPEC isolates in Iran is decreasing; although, the resistance gene content is almost stable through years.

Expression of enteropathogenic Escherichia coli map is significantly different than that of other type III secreted effectors in vivo

The enteropathogenic Escherichia coli (EPEC) locus of enterocyte effacement (LEE)-encoded effectors EspF and Map are multifunctional and have an impact on the tight junction barrier while the non-LEE-encoded proteins NleH1 and NleH2 possess significant anti-inflammatory activity. In order to address the temporal expression of these important genes in vivo, their promoters were cloned upstream of the luxCDABE operon, and luciferase expression was measured in EPEC-infected mice by bioluminescence using an in vivo imaging system (IVIS). Bioluminescent images of living mice, of excised whole intestines, and of whole intestines longitudinally opened and washed were assessed. The majority of bioluminescent bacteria localized in the cecum by 3 h postinfection, indicating that the cecum is not only a major colonization site of EPEC but also a site of EPEC effector gene expression in mice. espF, nleH1, and nleH2 were abundantly expressed over the course of infection. In contrast, map expression was suppressed at 2 days postinfection, and at 4 days postinfection it was totally abolished. After 2 to 4 days postinfection, when map is suppressed, EPEC colonization is significantly reduced, indicating that map may be one of the factors required to maintain EPEC colonization. This was confirmed in a competitive colonization study and in two models of chronic infection, repeated exposure to ketamine and Citrobacter rodentium infection. Our data suggest that map expression contributes to the maintenance of EPEC colonization.

High Prevalence of Class 1 to 3 Integrons Among Multidrug-Resistant Diarrheagenic Escherichia coli in Southwest of Iran

OBJECTIVES

Horizontal transfer of integrons is one of the important factors that can contribute to the occurrence of multidrug-resistant (MDR) bacteria. This study aimed to determine the prevalence of integrons among MDR Escherichia coli strains isolated from stool specimens and investigate the associations between the existence of integrons and MDR properties in the southwest of Iran.

METHODS

There were 164 E. coli strains isolated from January 2012 to June 2012. Fecal specimens identified as E. coli by the conventional methods. Subsequently the antibiotic resistance was assessed using Clinical and Laboratory Standard Institute criteria. The presence of class 1-3 integrons and embedded gene cassettes was verified using specific primers by multiplex polymerase chain reaction assay.

RESULTS

Among a total of 164 studied samples, 69 (42.07%) isolates were multidrug resistant. Class 1 and class 2 integrons were present in 78.26% and 76.81% MDR isolates, respectively. For the first time in Iran, class 3 integron was observed in 26.09% MDR isolates. Significant correlations were identified between: class 1 integron and resistance to amikacin, gentamicin, chloramphenicol, ampicillin, tetracycline, nalidixic acid, and co-trimoxazole; class 2 integron and resistance to aminoglycosides, co-trimoxazole, cefalexin, ampicillin, and chloramphenicol; and class 3 integron and resistance to gentamicin, kanamycin, and streptomycin.

CONCLUSION

Our results indicate that integrons are common among MDR isolates and they can be used as a marker for the identification of MDR isolates. Therefore, due to the possibility of a widespread outbreak of MDR isolates, molecular surveillance and sequencing of the integrons in other parts of the country is recommended.

Molecular characterization of enterohemorrhagic Escherichia coli isolates from cattle

A total of 21 (4.3%) enterohemorrhagic E. coli strains were isolated by biochemical tests and identification of the eae⁺stx1⁺stx2⁺ genotype from 490 stool samples obtained from calves with diarrhea during 1-year period from a major farm in Tehran, Iran. All of the strains showed resistance to ampicillin, ciprofloxacin, trimethoprim, streptomycin, chloramphenicol and tetracycline, while 19% showed resistance to gentamicin. Out of 21 EHEC strains, 11 (53%) harbored class 1 integron. Two different amplification products, which were approximately 750 and 1,700 bp in size, were obtained from amplified variable regions (in-F/in-R primers) in 3 (14.3%) and 4 (19%) of the EHEC isolates, which corresponded to dfrA7(dihydrofolate reductase type I) and dfrA1/aadA1(dihydrofolate reductase/aminoglycoside adenyltransferase) resistance gene cassettes, respectively, and this was confirmed by sequencing. Genotyping analysis revealed a total of 16 pulsotypes that corresponded to 16 isolates with the similarity indices of 62% and 30% for the most and least similar isolates, respectively, 9 of which harbored class 1 integron. Analysis of pulsotypes showed an extensive diversity among the isolates harboring integron, which is indicative of a lack of any significant genetic relatedness among the isolates. No obvious relation could be deduced between integron content and special pulsotypes. The little data available on the genotyping patterns of EHEC isolates from cattle and their resistance gene contents emphasize the need to establish genotyping databases in order to monitor and source track the source of emergence and spread of new resistant and integron-carrying genotypes.

Recent advances in understanding enteric pathogenic Escherichia coli

Although Escherichia coli can be an innocuous resident of the gastrointestinal tract, it also has the pathogenic capacity to cause significant diarrheal and extraintestinal diseases. Pathogenic variants of E. coli (pathovars or pathotypes) cause much morbidity and mortality worldwide. Consequently, pathogenic E. coli is widely studied in humans, animals, food, and the environment. While there are many common features that these pathotypes employ to colonize the intestinal mucosa and cause disease, the course, onset, and complications vary significantly. Outbreaks are common in developed and developing countries, and they sometimes have fatal consequences. Many of these pathotypes are a major public health concern as they have low infectious doses and are transmitted through ubiquitous mediums, including food and water. The seriousness of pathogenic E. coli is exemplified by dedicated national and international surveillance programs that monitor and track outbreaks; unfortunately, this surveillance is often lacking in developing countries. While not all pathotypes carry the same public health profile, they all carry an enormous potential to cause disease and continue to present challenges to human health. This comprehensive review highlights recent advances in our understanding of the intestinal pathotypes of E. coli.