Emergence of Resistance to Quinolones and ß-Lactam Antibiotics in Enteroaggregative and Enterotoxigenic Escherichia coli Causing Traveler's Diarrhea.

The objective of this study was to assess the antimicrobial resistance of enteroaggregative Escherichia coli (EAEC) and enterotoxigenic E. coli (ETEC) strains causing traveler's diarrhea (TD) and to investigate the molecular characterization of antimicrobial resistance genes to third-generation cephalosporins, cephamycins, and quinolones. Overall, 39 EAEC and 43 ETEC clinical isolates were studied. The susceptibilities of EAEC and ETEC against ampicillin, amoxicillin-clavulanic acid, cefotaxime, imipenem, chloramphenicol, tetracycline, co-trimoxazole, nalidixic acid, ciprofloxacin, azithromycin, and rifaximin were determined. All genes encoding resistance determinants were detected by PCR or PCR plus DNA sequencing. The epidemiology of selected EAEC and ETEC strains was studied using multilocus sequence typing (MLST). The resistance to quinolones of EAEC and ETEC strains causing TD has significantly increased over the last decades, and high percentages have been found especially in patients traveling to India and sub-Saharan Africa. Sequence type 38 (ST38) and ST131, carrying the blaCTX-M-15 and blaCTX-M-27 genes, respectively, are highly prevalent among extended-spectrum ß-lactamase (ESBL)-producing EAEC and ETEC strains. The cephamycinase ACT-20 is described in the present study for the first time in EAEC and ETEC strains causing TD in patients who had traveled to Central America. The percentages of resistance to azithromycin in EAEC and ETEC isolates from patients to Southeast Asia/India and Africa are above 25%. Meanwhile, rifaximin is still active against EAEC and ETEC, with the prevalence of resistant strains not being high. In conclusion, fluoroquinolones should no longer be considered the drugs of choice for the prevention or treatment in TD for travelers traveling to India and Africa. Azithromycin and rifaximin are still a good alternative to treat TD caused by EAEC or ETEC.

Antimicrobial resistance and virulence characterization among Escherichia coli clinical isolates causing severe obstetric infections in pregnant women.

The virulence markers and the antimicrobial resistance profiles of 78 Escherichia coli isolates causing obstetric infections accompanied by sepsis or not were studied. Adhesion-related virulence factors were the most prevalent markers. Low rates of resistance to the antimicrobial agents used as first-line therapy suggest their correct implementation in stewardship guidelines.

Antimicrobial resistance of Escherichia coli strains causing neonatal sepsis between 1998 and 2008.

BACKGROUND: Bloodstream infections are a significant cause of neonatal morbidity and death. An increase in the incidence of early neonatal sepsis due to Escherichia coli has been reported. The objective was to evaluate the antimicrobial resistance of E. coli strains causing early-onset neonatal sepsis (EONS) and late-onset neonatal sepsis (LONS) and their evolution. METHODS: E. coli strains from EONS and hospital-acquired LONS collected at the Hospital Clinic of Barcelona were included in the study. RESULTS: No statistically significant differences in resistance profiles were found between strains causing EONS and LONS. An increase in the resistance to all the antimicrobial agents studied was observed for the period 2000-2008 in comparison with the 1985-1999 period, with the increase in resistance to gentamicin, piperacillin and tobramycin being statistically significant. Two strains carried the bla(CTX-M) genes (bla(CTX-M-14) and bla(CTX-M-15)). CONCLUSION: The increase in ampicillin and gentamicin resistance makes a change in the treatment of neonates necessary.

CTX-M-15-producing enteroaggregative Escherichia coli as cause of travelers' diarrhea.

Travelers' diarrhea is a major public health problem. From patients in whom diarrhea developed after travel to India, 5 enteroaggregative Escherichia coli strains carrying ß-lactamase CTX-M-15 were identified; 3 belonged to clonal complex sequence type 38. This ß-lactamase contributes to the multidrug resistance of enteroaggregative E. coli, thereby limiting therapeutic alternatives.

Epidemiology and molecular characterization of multidrug-resistant Escherichia coli isolates harboring blaCTX-M group 1 extended-spectrum ß-lactamases causing bacteremia and urinary tract infection in Manhiça, Mozambique.

BACKGROUND: The emergence and spread of extended-spectrum ß-lactamases (ESBLs), especially CTX-M, is an important public health problem with serious implications for low-income countries where second-line treatment is often unavailable. Knowledge of the local prevalence of ESBL is critical to define appropriate empirical therapeutic strategies for multidrug-resistant (MDR) organisms. This study aimed to assess and characterize the presence of ESBL and especially CTX-M-producing Escherichia coli MDR isolates from patients with urinary tract infections (UTIs) and bacteremia in a rural hospital in Mozambique. MATERIALS AND METHODS: One hundred and fifty-one E. coli isolates from bacteremia and UTI in children were screened for CTX-M, TEM, SHV and OXA ß-lactamases by polymerase chain reaction and sequencing. Isolates carrying CTX-M group 1 ß-lactamases were further studied. The resistance to other antibiotic families was determined by phenotypic and genotypic methods, the location of the blaCTX-M gene and the epidemiology of the isolates were studied, and extensive plasmid characterization was performed. RESULTS: Approximately 11% (17/151) of E. coli isolates causing bacteremia and UTI were ESBL producers. CTX-M-15 was the most frequently detected ESBL, accounting for 75% of the total isolates characterized. The blaCTX-M gene is located in different plasmids belonging to different incompatibility groups and can be found in non-epidemiologically related isolates, indicating the high capacity of this resistance determinant to spread widely. CONCLUSION: Our data suggest the presence of a co-selection of third-generation cephalosporin-resistant determinants in the study area despite limited access to these antibiotics. This highlights the importance of continuous surveillance of antimicrobial resistance of both genetic elements of resistance and resistant isolates in order to monitor the emergence and trends of ESBL-producing isolates to promote adequate therapeutic strategies for the management of MDR bacterial infections.

Diversity of CTX-M-1-producing E. coli from German food samples and genetic diversity of the blaCTX-M-1 region on IncI1 ST3 plasmids.

Antimicrobial resistance to cephalosporins is commonly mediated by extended-spectrum ß-lactamases (ESBL) or plasmidic AmpC ß-lactamases (pAmpC). In livestock blaCTX-M-1 is the most frequently detected ESBL-encoding gene. As transmission to consumers through contaminated food is often proposed, this study characterized ESBL/pAmpC-producing E. coli collected from food samples. Therefore, samples from food products of animal origin and vegetables were screened for phenotypically resistant E. coli by selective cultivation. The ESBL genotype was confirmed for 404 isolates with the majority of them (n = 212) harboring the blaCTX-M-1 gene. PFGE and MLST analyses as well as plasmid characterization were carried out for 89 isolates, selected under epidemiological aspects. In addition, 44 isolates were investigated by whole genome sequencing and/or sequencing of their plasmids on an Illumina Miseq platform. MLST and PFGE indicated a diverse population of CTX-M-1-producing E. coli in German food samples with no spread of single clonal lineages. The majority of the isolates harbored the blaCTX-M-1 gene on IncI1 plasmids. Frequently, the gene was associated with the ISEcp1 element and located on a ∼100 kb IncI1 plasmid depicting the plasmid multilocus sequence type (ST) 3. The blaCTX-M-1 gene and its flanking sequences were located within the shufflon of the type IV pilus region in diverse orientations. In conclusion, dissemination of the CTX-M-1 ß-lactamase within food samples of animal origin is driven by the transmission of a ∼100 kb large IncI1 ST3 plasmid. Apart from conjugal transfer of IncI1 ST3 plasmids the transmission of the blaCTX-M-1 gene might be further promoted through mobilization due to its location within a recombination hot-spot of IncI1 plasmids.

CTX-M-15-Producing E. coli Isolates from Food Products in Germany Are Mainly Associated with an IncF-Type Plasmid and Belong to Two Predominant Clonal E. coli Lineages.

Extended-spectrum beta-lactamases (ESBL) mediating resistance to 3rd generation cephalosporins are a major public health issue. As food may be a vehicle in the spread of ESLB-producing bacteria, a study on the occurrence of cephalosporin-resistantu Escherichia coli in food was initiated. A total of 404 ESBL-producing isolates were obtained from animal-derived food samples (e.g., poultry products, pork, beef and raw milk) between 2011 and 2013. As CTX-M-15 is the most abundant enzyme in ESBL-producing E. coli causing human infections, this study focusses on E. coli isolates from food samples harboring the blaCTX-M-15 gene. The blaCTX-M-15 gene was detected in 5.2% (n = 21) of all isolates. Molecular analyses revealed a phylogenetic group A ST167 clone that was repeatedly isolated from raw milk and beef samples over a period of 6 months. The analyses indicate that spread of CTX-M-15-producing E. coli in German food samples were associated with a multireplicon IncF (FIA FIB FII) plasmid and additional antimicrobial resistance genes such as aac(6)-Ib-cr, blaOXA-1, catB3, different tet-variants as well as a class 1 integron with an aadA5/dfrA17 gene cassette. In addition, four phylogenetic group A ST410 isolates were detected. Three of them carried a chromosomal copy of the blaCTX-M-15 gene and a single isolate with the gene on a 90 kb IncF plasmid. The blaCTX-M-15 gene was always associated with the ISEcp1 element. In conclusion, CTX-M-15-producing E. coli were detected in German food samples. Among isolates of different matrices, two prominent clonal lineages, namely A-ST167 and A-ST410, were identified. These lineages may be important for the foodborne dissemination of CTX-M-15-producing E. coli in Germany. Interestingly, these clonal lineages were reported to be widely distributed and especially prevalent in isolates from humans and livestock. Transmission of CTX-M-15-harboring isolates from food-producing animals to food appears probable, as isolates obtained from livestock and food samples within the same time period exhibit comparable characteristics as compared to isolates detected from human. However, the routes and direction of transmission need further investigation.

Vaginal versus Obstetric Infection Escherichia coli Isolates among Pregnant Women: Antimicrobial Resistance and Genetic Virulence Profile.

Vaginal Escherichia coli colonization is related to obstetric infections and the consequent development of infections in newborns. Ampicillin resistance among E. coli strains is increasing, which is the main choice for treating empirically many obstetric and neonatal infections. Vaginal E. coli strains are very similar to extraintestinal pathogenic E. coli with regards to the virulence factors and the belonging to phylogroup B2. We studied the antimicrobial resistance and the genetic virulence profile of 82 E. coli isolates from 638 vaginal samples and 63 isolated from endometrial aspirate, placental and amniotic fluid samples from pregnant women with obstetric infections. The prevalence of E. coli in the vaginal samples was 13%, which was significant among women with associated risk factors during pregnancy, especially premature preterm rupture of membranes (p<0.0001). Sixty-five percent of the strains were ampicillin-resistant. The E. coli isolates causing obstetric infections showed higher resistance levels than vaginal isolates, particularly for gentamicin (p = 0.001). The most prevalent virulence factor genes were those related to the iron uptake systems revealing clear targets for interventions. More than 50% of the isolates belonged to the virulent B2 group possessing the highest number of virulence factor genes. The ampicillin-resistant isolates had high number of virulence factors primarily related to pathogenicity islands, and the remarkable gentamicin resistance in E. coli isolates from women presenting obstetric infections, the choice of the most appropriate empiric treatment and clinical management of pregnant women and neonates should be carefully made. Taking into account host-susceptibility, the heterogeneity of E. coli due to evolution over time and the geographical area, characterization of E. coli isolates colonizing the vagina and causing obstetric infections in different regions may help to develop interventions and avoid the aetiological link between maternal carriage and obstetric and subsequent puerperal infections.

Characterisation of extended-spectrum ß-lactamases among Klebsiella pneumoniae isolates causing bacteraemia and urinary tract infection in Mozambique.

The aim of this study was to determine the prevalence of extended-spectrum ß-lactamase (ESBL)-producing Klebsiella pneumoniae isolated from urinary tract and bloodstream infections in a rural hospital in Manhiça, Mozambique. ESBLs were investigated among ceftriaxone-non-susceptible K. pneumoniae clinical isolates recovered between 2004 and 2009. Characterisation of blaCTX-M, blaSHV, blaOXA and blaTEM genes was performed by PCR and sequencing. Epidemiological relationships were established by phylogenetic analysis, repetitive extragenic palindromic PCR (REP-PCR), pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST), whilst plasmid transferability was evaluated by conjugation. In addition, the presence of class 1 and 2 integrons was studied. A total of 19 K. pneumoniae were analysed. The blaCTX-M-15 gene was found in all strains. Other ESBL genes were found concomitantly, including blaSHV-5, blaSHV-2, blaSHV-2A, blaSHV-12 and blaSHV-38. In addition, other ß-lactamases such as blaTEM-1 and blaOXA-30 were also detected. REP-PCR identified 15 different epidemiological profiles. MLST analysis also showed great variability of sequence types. The blaCTX-M-15 gene showed a high transfer capacity. The presence of class 1 integrons was high. High levels of multidrug resistance were also found. In conclusion, these data show the dominance of the CTX-M-type ESBL, particularly CTX-M-15, supporting its worldwide dissemination, including in areas with limited access to third-generation cephalosporins. This finding is a matter of concern for clinical management as third-generation cephalosporins are an alternative for treating severe cases of multidrug-resistant infections in this community.

Characterization of CTX-M-14 and CTX-M-15 producing Escherichia coli strains causing neonatal sepsis.

Neonatal sepsis is a disease affecting newborns ≤1 month of age with clinical symptoms and positive blood cultures. The number of Escherichia coli strains causing neonatal sepsis resistant to the antibiotics used in the treatment is increasing. In this study, two E. coli strains causing sepsis in neonates of mothers infected with an E. coli strain harboring extended spectrum beta-lactamases were characterized. The bla(CTX-M-15) and the bla(CTX-M-14) genes were found in an IncFIA and nontypeable transferable plasmids, respectively. In addition, these highly virulent strains belonged to ST705 and ST156 clonal groups, respectively. The presence of strains, which are highly virulent and resistant to ampicillin, gentamicin, and cephalosporins, makes a change in empirical treatment necessary as well as an increase in the surveillance of these infections.

Prevalence of Escherichia coli among samples collected from the genital tract in pregnant and nonpregnant women: relationship with virulence.

Escherichia coli are enteric Gram-negative bacilli that can colonize the female genital tract and become implicated in different infections in pregnant women, including intra-amniotic infection, puerperal infections and neonatal infections. The virulence profiles of E. coli isolates from vaginal swabs from pregnant and nonpregnant women were compared. The hly-, cnf-, pap- and iroN-genes were found significantly more frequently in E. coli isolated from pregnant women in comparison with those isolated from nonpregnant women. Escherichia coli from pregnant women seem to be more virulent than from nonpregnant women developing severe infections, thereby increasing possible neonatal sepsis.

Prevalence of enterotoxins among Escherichia coli isolates causing bacteraemia.

The most frequent cause of bacteraemia among Gram-negative bacteria is Escherichia coli. Analysis of the genes encoding the Shigella enterotoxin 1 (ShET-1), ShET-2, enteroaggregative heat stable toxin 1 (EAST-1) toxins and AggR factor in E. coli strains causing bacteraemia revealed that set1 genes were presented significantly more frequently among quinolone-susceptible strains (P<0.0001), in phylogenetic group B2 (P=0.0004) and in biofilm strains (P=0.02). In contrast, sen genes were significantly more frequent among nalidixic acid-resistant isolates (15% vs. 6%, P=0.046) and in phylogenetic group B1 (P=0.0001). This is the first study in which ShET1, ShET2 and EAST-1 have been found in E. coli collected from blood.