Detection of multiple cephalosporin-resistant Escherichia coli from a cattle fecal sample in Great Britain

Characterization of O25b-ST131 Escherichia coli Clone Producing CTX-M-15, DHA-4, and CMY-42 in Urinary Tract Infections in a Tunisian Island

The dissemination of extended-spectrum β-lactamases encoding genes in Escherichia coli, especially in the uropathogenic O25b-ST131 E. coli clone, constitutes a real concern. We aimed to identify the molecular mechanisms of resistance to cephalosporins among E. coli clinical isolates and to estimate the prevalence of the uropathogenic O25b-ST131 clone in our study. Forty-two cephalosporin-resistant E. coli implicated in urinary tract infections were collected from the Regional Hospital of a southeastern Tunisian Island from April 2015 to August 2016. Molecular screening of β-lactamases encoding genes by PCR and sequencing showed that the majority of our isolates harbored bla_CTX-M gene (bla_CTX-M-15 [n = 36], bla_CTX-M-14 [n = 2]). Nevertheless, the bla_SHV, bla_TEM, and bla_OXA-1 genes were not detected. Various class C β-lactamases encoding genes were observed in association or not with bla_CTX-M genes and were as follows: bla_ampC (n = 14), bla_CMY-42 (n = 7), bla_CMY-2 (n = 1), and bla_DHA-4 (n = 1). The research of O25b-ST131 clone was carried out by duplex PCR (pabB and trpA genes) and revealed that most of our isolates (n = 30) belonged to this clone. We also noted that the majority of our isolates belonged to the B2 phylogenetic group (n = 32), five isolates to the B1 phylogenetic group, three isolates to the D phylogenetic group, and only two isolates belonged to the A phylogenetic group. Our study provides new epidemiological information about E. coli clinical isolates in this area. Indeed, this is the first report of CTX-M-14 producing O25b-ST131 E. coli in our country and the first report of DHA-4 and CMY-42 producing E. coli in Tunisia.

Adherent/invasive Escherichia coli (AIEC) isolates from asymptomatic people: new E. coli ST131 O25:H4/H30-Rx virotypes

BACKGROUND

The widespread Escherichia coli clone ST131 implicated in multidrug-resistant infections has been recently reported, the majority belonging to O25:H4 serotype and classified into five main virotypes in accordance with the virulence genes carried.

METHODS

Pathogenicity Islands I and II (PAI-I and PAI-II) were determined using conventional PCR protocols from a set of four E. coli CTXR ST131 O25:H4/H30-Rx strains collected from healthy donors' stool. The virulence genes patterns were also analyzed and compared them with the virotypes reported previously; then adherence, invasion, macrophage survival and biofilm formation assays were evaluated and AIEC pathotype genetic determinants were investigated.

FINDINGS

Non-reported virulence patterns were found in our isolates, two of them carried satA, papA, papGII genes and the two-remaining isolates carried cnfI, iroN, satA, papA, papGII genes, and none of them belonged to classical ST131 virotypes, suggesting an endemic distribution of virulence genes and two new virotypes. The presence of PAI-I and PAI-II of Uropathogenic E. coli was determined in three of the four strains, furthermore adherence and invasion assays demonstrated higher degrees of attachment/invasion compared with the control strains. We also amplified intI1, insA and insB genes in all four samples.

INTERPRETATION

The results indicate that these strains own non-reported virotypes suggesting endemic distribution of virulence genes, our four strains also belong to an AIEC pathotype, being this the first report of AIEC in México and the association of AIEC with healthy donors.

Cefotaxime resistant Escherichia coli collected from a healthy volunteer; characterisation and the effect of plasmid loss

In this study 6 CTX-M positive E. coli isolates collected during a clinical study examining the effect of antibiotic use in a human trial were analysed. The aim of the study was to analyse these isolates and assess the effect of full or partial loss of plasmid genes on bacterial fitness and pathogenicity. A DNA array was utilised to assess resistance and virulence gene carriage. Plasmids were characterised by PCR-based replicon typing and addiction system multiplex PCR. A phenotypic array and insect virulence model were utilised to assess the effect of plasmid-loss in E. coli of a large multi-resistance plasmid. All six E. coli carrying bla_CTX-M-14 were detected from a single participant and were identical by pulse field gel electrophoresis and MLST. Plasmid profiling and arrays indicated absence of a large multi-drug resistance (MDR) F-replicon plasmid carrying blaTEM, aadA4, strA, strB, dfrA17/19, sul1, and tetB from one isolate. Although this isolate partially retained the plasmid it showed altered fitness characteristics e.g. inability to respire in presence of antiseptics, similar to a plasmid-cured strain. However, unlike the plasmid-cured or plasmid harbouring strains, the survival rate for Galleria mellonella infected by the former strain was approximately 5-times lower, indicating other possible changes accompanying partial plasmid loss. In conclusion, our results demonstrated that an apparently healthy individual can harbour bla_CTX-M-14E. coli strains. In one such strain, isolated from the same individual, partial absence of a large MDR plasmid resulted in altered fitness and virulence characteristics, which may have implications in the ability of this strain to infect and any subsequent treatment.

Prevalence of extended-spectrum β-lactamase-producing Escherichia coli on Bavarian dairy and beef cattle farms

Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli strains are believed to be widely distributed among humans and animals; however, to date, there are only few studies that support this assumption on a regional or countrywide scale. Therefore, a study was designed to assess the prevalence of ESBL-producing E. coli in dairy cows and beef cattle in the southern part of Bavaria, Germany. The study population included 30 mixed dairy and beef cattle farms and 15 beef cattle farms. Fecal samples, boot swabs, and dust samples were analyzed for ESBL-producing E. coli using selective media. PCR was performed to screen for CTX-M and ampC resistance genes. A total of 598 samples yielded 196 (32.8%) that contained ESBL-producing E. coli, originating from 39 (86.7%) of 45 farms. Samples obtained from mixed farms were significantly more likely to be ESBL-producing E. coli positive than samples from beef cattle farms (fecal samples, P < 0.001; boot swabs, P = 0.014; and dust samples, P = 0.041). A total of 183 isolates (93.4%) of 196 ESBL-producing E. coli-positive strains harbored CTX-M genes, CTX-M group 1 being the most frequently found group. Forty-six additional isolates contained ampC genes, and 5 of the 46 isolates expressed a blaCMY-2 gene. The study shows that ESBL-producing E. coli strains are commonly found on Bavarian dairy and beef cattle farms. Moreover, to our knowledge, this is the first report of the occurrence of blaCMY-2 in cattle in Germany.

Epidemiology of extended spectrum beta-lactamase E. coli (CTX-M-15) on a commercial dairy farm

The epidemiology of an extended spectrum beta-lactamase Escherichia coli (CTX-M-15) was observed and described on a commercial dairy farm located in the United Kingdom. During 2008 longitudinal sampling of faecal pat samples from different cattle groups comprising milking and non-milking cows, calving cows, calves, and the environment was carried out. The proportion of CTX-M-15 E. coli positive samples was significantly (p<0.0.01) higher in milking cows (30.3%, CI(95%) 26.8; 33.8) than in the herd as a whole (17.0%, CI(95%) 14.9; 19.0). In 2008 95.6% of sampled calves tested positive for CTX-M-15 E. coli at two days of age. A more detailed investigation in 2009 revealed that cows and heifers were approximately eight times more likely to test positive in the 10 days after calving than the 9 days before (OR 7.6, CI(95%) 2.32; 24.9). The CTX-M15 E. coli was also readily isolated from the immediate calving pen environment, including the water troughs. A cyclic pattern was apparent where cows immediately after calving and as high yielders were highly positive, but where the prevalence decreased during the dry period. The increased prevalence of the CTX-M-15 E. coli in certain cattle groups and farm environments including calving pens suggested that husbandry, antimicrobial usage and hygiene may play a significant role on a farm with regards to the epidemiology of CTX-M-15. This may offer a practical opportunity to reduce further dissemination through good practice and hygiene around calving.

Evaluation of CHROMagar CTX, a novel medium for isolating CTX-M-ESBL-positive Enterobacteriaceae while inhibiting AmpC-producing strains

OBJECTIVES

The aim of this study was to evaluate CHROMagar CTX (CHROMagar France), a novel agar for the selective isolation of Enterobacteriaceae expressing the bla(CTX-M) gene in the presence of enteric bacteria expressing AmpC enzymes.

METHODS

A panel of 150 Gram-negative bacteria (mainly Escherichia coli, Enterobacter, Klebsiella, Pseudomonas and Salmonella) isolated from humans and animals were assembled for the purpose of evaluating CHROMagar CTX and comparing it with CHROMagar ECC with the addition of 1, 2, 4 and 8 mg/L cefotaxime or ceftazidime and with bioMérieux extended-spectrum beta-lactamase (ESBL)-Bx agar. CHROMagar CTX was also assessed for its ability to isolate bla(CTX-M) strains from farm animal faeces (n = 342).

RESULTS

The panel contained CTX-M-positive (n = 70) strains (CTX-M types 1, 9, 14 and 15), ESBLs (n = 31) belonging to other families (OXA, PER, SHV, TEM, VEB), strains positive for ampC genes (n = 31), strains that overexpressed ampC (n = 6), non-ESBL/AmpC strains (n = 11) and Klebsiella oxytoca (n = 1). CHROMagar CTX was superior to other agars tested for selective isolation of Enterobacteriaceae expressing the bla(CTX-M) gene with 100% sensitivity and 64.2% specificity for CTX-M strains in the panel and 90.1% of the colonies from animal faeces plated on CHROMagar CTX were CTX-M strains.

CONCLUSIONS

CHROMagar CTX is a valuable agar in situations where it is important to isolate bla(CTX-M) strains in the presence of AmpC strains. The agar may be particularly useful in veterinary studies, where AmpC-producing commensal E. coli can be encountered reasonably frequently in the enteric flora of some animal species and may also be useful, following further evaluation, for samples from humans.

Expression of AmpC beta-lactamase in Enterobacter cloacae isolated from retail ground beef, cattle farm and processing facilities

AIMS

To better understand antibiotic resistance of Enterobacter cloacae isolates originated from food animals, the phenotypic and genotypic resistance of Ent. cloacae isolates from retail ground beef, cattle farm, processing facilities and clinical settings were investigated.

METHODS AND RESULTS

The ampC, ampD and ampR genes in the isolates were sequenced and analysed. beta-Lactamase activities and beta-lactamase profiles of the isolates were analysed by the enzymatic hydrolysis of nitrocefin and isoelectric focussing, respectively. The ampC gene of the Ent. cloacae isolate was cloned and transformed into Escherichia coli strains. The genomic DNA profiles of Ent. cloacae isolates were analysed by using pulse field gel electrophoresis (PFGE). Mutation at one residue (Val-54-->Ile) in the AmpR amino acid sequence was consistently found in Ent. cloacae isolates that were resistant to a broadspectrum of beta-lactam agents. The enzyme activity in the isolates was induced by cefoxitin. The pI (isoelectric point) of the enzymes produced by the test strains ranged from 8.4 to 8.9. Cloning of ampC gene of the Ent. cloacae isolate conferred the resistance to ampicillin, cephalothin and amoxicillin in recipient E. coli strains. One recipient of E. coli O157:H7 strain additionally acquired resistance to ceftiofur. The genomic analysis of Ent. cloacae isolates by PFGE showed that the isolates from various sources were genetically unrelated.

CONCLUSIONS

The spread of diverse clones of AmpC-producing Ent. cloacae occurred in the ecosystem and retail products.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our findings suggested that AmpC-producing Ent. cloacae could be a contributor in spreading beta-lactamase genes in farm environments and food processing environments.

Population-based laboratory surveillance for AmpC beta-lactamase-producing Escherichia coli, Calgary

AmpC β-lactamase–producing E. coli are commonly isolated from the urinary tract of older women.

In the Calgary Health Region during 2000–2003, prospective, active, population-based laboratory surveillance for all cefoxitin-resistant Escherichia coli isolates was performed. Isolates were screened with an inhibitor-based disk test, and plasmid-mediated types were identified by multiplex PCR with sequencing. A total of 369 AmpC β-lactamase–producing E. coli isolates were identified; annual incidence rates were 1.7, 4.3, 11.2, and 15 per 100,000 residents for each year, respectively. AmpC β-lactamase–producing E. coli was 5× more likely to be isolated from female than male patients across all age groups except <1 year. Of these isolates, 83% were community onset, and urine was the principal site of isolation (90% of patients). PCR showed that 125 (34%) were positive for bla_cmy genes; sequencing identified these enzymes to be CMY-2. In this large Canadian region, AmpC β-lactamase–producing E. coli is an emerging community pathogen that commonly causes urinary tract infections in older women.

Short Communication:Antimicrobial Resistance Patterns ofEscherichia coliThrough the Digestive Tract of Veal Calves

The aim of the present study was to evaluate differences in resistance patterns of Escherichia coli in different parts of the digestive tract of veal calves. Therefore, after slaughter, the lower intestinal tract of 19 calves was sampled at five locations (duodenum, jejunum, cecum, colon, and rectum), and up to three E. coli isolates per sample underwent susceptibility testing for seven antimicrobial agents (gentamicin, amoxycillin + clavulanic acid, tetracycline, trimethoprim + sulfamethoxazole, ampicillin, nalidixic acid, and enrofloxacin), using the Kirby-Bauer disk diffusion method. Multiresistance (resistance to more than two compounds) was present in 93.5% of all isolates (n = 179). For gentamicin, nalidixic acid, and enrofloxacin, the percentage of resistant E. coli isolates was significantly lower in the duodenum and jejunum than in the cecum, colon, and rectum. For ampicillin, the percentage of resistance was significantly lower in the jejunum, compared to the other segments of the intestinal tract. For the other antimicrobials tested, no significant differences in the percentage of resistant isolates throughout the intestinal tract were detected. In conclusion, resistance among enteric E. coli from veal calves can reach high levels and prevalence depends on localization of sampling. These considerations should be taken into account when further fine-tuning sampling protocols for indicator bacteria.

beta-Lactam resistance and beta-lactamases in bacteria of animal origin

beta-Lactams are among the most clinically important antimicrobials in both human and veterinary medicine. Bacterial resistance to beta-lactams has been increasingly observed in bacteria, including those of animal origin. The mechanisms of beta-lactam resistance include inaccessibility of the drugs to their target, target alterations and/or inactivation of the drugs by beta-lactamases. The latter contributes predominantly to beta-lactam resistance in Gram-negative bacteria. A variety of beta-lactamases have been identified in bacteria derived from food-producing and companion animals and may further serve as a reservoir for beta-lactamase-producing bacteria in humans. While this review mainly describes beta-lactamases from animal-derived Escherichia coli and Salmonella spp., beta-lactamases from animal-derived Campylobacter spp., Enterococcus spp., Staphylococcus spp. and other pathogens are also discussed. Of particular concern are the increasingly-isolated plasmid-encoded AmpC-type CMY and extended-spectrum CTX-M beta-lactamases, which mediate acquired resistance to extended-spectrum beta-lactams. The genes encoding these enzymes often coexist with other antimicrobial resistance determinants and can also be associated with transposons/integrons, increasing the potential enrichment of multidrug resistant bacteria by multiple antimicrobial agents as well as dissemination of the resistance determinants among bacterial species. Characterization of beta-lactam-resistant animal-derived bacteria warrants further investigation of the type and distribution of beta-lactamases in bacteria of animal origin and their potential impact on human medicine.

Replicon typing of plasmids carrying CTX-M or CMY beta-lactamases circulating among Salmonella and Escherichia coli isolates

Replicon typing of plasmids carrying bla(CTX-M) or bla(CMY) beta-lactamase genes indicates a predominance of I1 and A/C replicons among bla(CMY)-carrying plasmids and five different plasmid scaffolds associated with the different types of bla(CTX-M) genes (I1, FII, HI2, K, and N). These results demonstrate the association of certain beta-lactamase genes with specific plasmid backbones.

Molecular epidemiology of ceftiofur-resistant Escherichia coli isolates from dairy calves

Healthy calves (n = 96, 1 to 9 weeks old) from a dairy herd in central Pennsylvania were examined each month over a five-month period for fecal shedding of ceftiofur-resistant gram-negative bacteria. Ceftiofur-resistant Escherichia coli isolates (n = 122) were characterized by antimicrobial resistance (disk diffusion and MIC), serotype, pulsed-field gel electrophoresis subtypes, beta-lactamase genes, and virulence genes. Antibiotic disk diffusion assays showed that the isolates were resistant to ampicillin (100%), ceftiofur (100%), chloramphenicol (94%), florfenicol (93%), gentamicin (89%), spectinomycin (72%), tetracycline (98%), ticarcillin (99%), and ticarcillin-clavulanic acid (99%). All isolates were multidrug resistant and displayed elevated MICs. The E. coli isolates belonged to 42 serotypes, of which O8:H25 was the predominant serotype (49.2%). Pulsed-field gel electrophoresis classified the E. coli isolates into 27 profiles. Cluster analysis showed that 77 isolates (63.1%) belonged to one unique group. The prevalence of pathogenic E. coli was low (8%). A total of 117 ceftiofur-resistant E. coli isolates (96%) possessed the bla(CMY2) gene. Based on phenotypic and genotypic characterization, the ceftiofur-resistant E. coli isolates belonged to 59 clonal types. There was no significant relationship between calf age and clonal type. The findings of this study revealed that healthy dairy calves were rapidly colonized by antibiotic-resistant strains of E. coli shortly after birth. The high prevalence of multidrug-resistant nonpathogenic E. coli in calves could be a significant source of resistance genes to other bacteria that share the same environment.

Molecular epidemiology of ceftiofur-resistant Escherichia coli isolates from dairy calves

Healthy calves (n = 96, 1 to 9 weeks old) from a dairy herd in central Pennsylvania were examined each month over a five-month period for fecal shedding of ceftiofur-resistant gram-negative bacteria. Ceftiofur-resistant Escherichia coli isolates (n = 122) were characterized by antimicrobial resistance (disk diffusion and MIC), serotype, pulsed-field gel electrophoresis subtypes, beta-lactamase genes, and virulence genes. Antibiotic disk diffusion assays showed that the isolates were resistant to ampicillin (100%), ceftiofur (100%), chloramphenicol (94%), florfenicol (93%), gentamicin (89%), spectinomycin (72%), tetracycline (98%), ticarcillin (99%), and ticarcillin-clavulanic acid (99%). All isolates were multidrug resistant and displayed elevated MICs. The E. coli isolates belonged to 42 serotypes, of which O8:H25 was the predominant serotype (49.2%). Pulsed-field gel electrophoresis classified the E. coli isolates into 27 profiles. Cluster analysis showed that 77 isolates (63.1%) belonged to one unique group. The prevalence of pathogenic E. coli was low (8%). A total of 117 ceftiofur-resistant E. coli isolates (96%) possessed the bla(CMY2) gene. Based on phenotypic and genotypic characterization, the ceftiofur-resistant E. coli isolates belonged to 59 clonal types. There was no significant relationship between calf age and clonal type. The findings of this study revealed that healthy dairy calves were rapidly colonized by antibiotic-resistant strains of E. coli shortly after birth. The high prevalence of multidrug-resistant nonpathogenic E. coli in calves could be a significant source of resistance genes to other bacteria that share the same environment.

Characterization of AmpC-mediated resistance in clinical Salmonella isolates recovered from humans during the period 1992 to 2003 in England and Wales

The increase in AmpC-mediated resistance in salmonellae constitutes a serious public health concern, since these enzymes confer resistance to a wide range of beta-lactams. One hundred six isolates were selected from 278,308 Salmonella isolates based on resistance to ampicillin and cephalosporins and were subjected to further characterization. Nine isolates had a cefoxitin inhibition diameter < or = 17 mm and were proven to be AmpC positive by multiplex PCR. Sequence analysis revealed the presence of bla(DHA-1), bla(CMY-2), and bla(CMY-4) genes. All nine isolates presented different pulsed-field gel electrophoresis restriction profiles. The AmpC genetic determinants were present in transferable plasmids of around 11, 42, 70, 98, and 99 MDa. A combination of size and restriction fragment length polymorphism (RFLP) analysis showed that all the bla(CMY) plasmids investigated in our study were different, which suggests that bla(CMY) may be located in different plasmid environments. Some United Kingdom isolates linked to foreign travel showed RFLP plasmid patterns consistent with plasmids previously seen in the United States, which suggests that bla(CMY-2) has also been disseminated through plasmid transfer. The fact that two of the domestically acquired United Kingdom isolates presented previously unseen RFLP plasmid patterns could indicate that these strains have followed routes different from those prevalent in North America or other parts of the world. This study represents the first report of bla(CMY) genes in Salmonella isolates in the United Kingdom and the first report of CMY-4 in Salmonella enterica serotype Senftenberg worldwide.