Transmission dynamics of extended-spectrum β-lactamase and AmpC β-lactamase-producing Escherichia coli in a broiler flock without antibiotic use.

Extended-spectrum and AmpC β-lactamase-producing Escherichia coli (ESBL/AmpC-EC) are found throughout the broiler production pyramid. Transmission of resistance between broilers and humans could occur at any point, representing a potential public health issue. Insight in farm transmission dynamics could provide a basis for control, leading to fewer contaminated broilers. The aim was quantifying transmission rates and routes of ESBL/AmpC-EC, and specific phylogenetic groups, in an organic broiler flock without antibiotic use. In each of two consecutive production rounds, 80 randomly chosen broilers were followed individually. Cloacal swabs from these, 20 other randomly chosen broilers, and 11 environmental samples were taken at several moments from arrival till slaughter. ESBL/AmpC-EC were isolated by selective pre-enrichment, and ESBL/AmpC-genes and E. coli phylogenetic groups were determined. Transmission parameters (β) were estimated using a Generalised Linear Model with a susceptible-infectious-susceptible model. Effect of direct broiler contact as compared to contact through the environment and previous carriage c.q. infectious status and their interaction were included as explanatory variables. Multiplying β by the length of the infectious period gives the reproduction ratio (R). On day 1, prevalence was 28.8% (95%CI 19.2-40.0%) and 0.0% (95%CI 0.0-4.5%) among individually followed broilers, in round 1 and 2 respectively. In round 2, the environment was positive before arrival of day-old chicks. After 3 days, almost 100% of broilers and environmental samples were positive in both rounds. Most samples were positive for CTX-M-1 group genes, and A1 and B1 were predominant phylogenetic groups. From day 3 there was a shift towards more phylogenetic groups. R was 1.70 (95%CI 0.55-5.25) for total ESBL/AmpC-EC. Risk for broilers to become infectious was lower if previously infectious (βpreviously infectious=0.02 vs. βnot previously infectious=3.41; P<0.0001). For phylogenetic groups separately, R was 0.88 (95%CI 0.38-2.07), 0.51 (95%CI 0.27-0.98), 0.99 (95%CI 0.65-1.51) for A1, B1 and rest (i.e. A0, B2, D1, D2) groups, respectively. The interaction effect for A1 and B1 was reflected in the fact that when broilers were previous infectious, the environment was relatively more important for transmission of the A1 group, while this was direct contact between broilers for the B1 group. Positive day-old chicks and the environment both play a role in introduction and transmission of ESBL/AmpC-EC in flocks. These results suggest that, even without selective pressure from antibiotics, total ESBL/AmpC-EC persistence, and resulting endemic situation, seem to be caused by shifts in carriage of different phylogenetic groups. It implies that contaminated broilers enter the slaughterhouse.

Huijbers PMC ，Graat EAM ，van Hoek AHAM ，Veenman C ，de Jong MCM ，van Duijkeren E ... -  《-》

Competitive Exclusion Reduces Transmission and Excretion of Extended-Spectrum-β-Lactamase-Producing Escherichia coli in Broilers.

Extended-spectrum β-lactamases (ESBLs) and plasmid-mediated AmpC β-lactamases (pAmpC) are enzymes able to hydrolyze a large variety of β-lactam antibiotics, including third-generation cephalosporins and monobactams. Broilers and broiler meat products can be highly contaminated with ESBL- and pAmpC-producing Escherichia coli strains, also known as extended-spectrum cephalosporin (ESC)-resistant E. coli strains, and can be a source for human infections. As few data on interventions to reduce the presence of ESC-resistant E. coli in broilers are available, we used transmission experiments to examine the role of competitive exclusion (CE) on reducing transmission and excretion in broilers. A broiler model to study the transmission of ESC-resistant E. coli was set up. Day-old chickens were challenged with an ESBL-producing E. coli strain isolated from healthy broilers in the Netherlands. Challenged and not challenged chicks were housed together in pairs or in groups, and ESBL-producing E. coli transmission was monitored via selective culturing of cloacal swab specimens. We observed a statistically significant reduction in both the transmission and excretion of ESBL-producing E. coli in chicks treated with the probiotic flora before E. coli challenge compared to the transmission and excretion in untreated controls. In conclusion, our results support the use of competitive exclusion as an intervention strategy to control ESC-resistant E. coli in the field.IMPORTANCE Extended-spectrum β-lactamases (ESBLs) and plasmid-mediated AmpC β-lactamases are a primary cause of resistance to β-lactam antibiotics among members of the family Enterobacteriaceae in humans, animals, and the environment. Food-producing animals are not exempt from this, with a high prevalence being seen in broilers, and there is evidence pointing to a possible foodborne source for human contamination. We investigated the effect of administration of a commercial probiotic product as an intervention to reduce the amount of ESBL-producing Escherichia coli in broilers. Our results showed a substantial reduction in the level of colonization of broiler intestines by ESBL-producing E. coli after administration of commercial probiotic product. The protective effect provided by these probiotics could be implemented on a larger scale in poultry production. Reductions in the levels of ESBL-producing Enterobacteriaceae in the food chain would considerably benefit public health.

Ceccarelli D ，van Essen-Zandbergen A ，Smid B ，Veldman KT ，Boender GJ ，Fischer EAJ ，Mevius DJ ，van der Goot JA ... -  《-》

Extended-spectrum and AmpC β-lactamase-producing Escherichia coli in broilers and people living and/or working on broiler farms: prevalence, risk factors and molecular characteristics.

The objectives of this study were to: estimate the prevalence of extended-spectrum β-lactamase (ESBL)- and AmpC β-lactamase-producing Escherichia coli carriage among broiler farmers, their family members and employees; identify and quantify risk factors for carriage, with an emphasis on contact with live broilers; and compare isolates from humans and broilers within farms with respect to molecular characteristics to gain insight into transmission routes. A cross-sectional prevalence study was conducted on 50 randomly selected Dutch broiler farms. Cloacal swabs were taken from 20 randomly chosen broilers. Faecal swabs were returned by 141 individuals living and/or working on 47 farms. ESBL/AmpC-producing E. coli were isolated and, for selected isolates, phylogenetic groups, plasmids and sequence types were determined. Questionnaires were used for risk factor analysis. All sampled farms were positive, with 96.4% positive pooled broiler samples. The human prevalence was 19.1%, with 14.3% and 27.1% among individuals having a low and a high degree of contact with live broilers, respectively. Five pairs of human-broiler isolates had identical genes, plasmid families and E. coli sequence types, showing clonal transmission. Furthermore, similar ESBL/AmpC genes on the same plasmid families in different E. coli sequence types in humans and broilers hinted at horizontal gene transfer. The prevalence among people on broiler farms was higher than in previous studies involving patients and the general population. Furthermore, an increased risk of carriage was shown among individuals having a high degree of contact with live broilers. The (relative) contribution of transmission routes that might play a role in the dissemination of ESBL/AmpC-encoding resistance genes to humans on broiler farms should be pursued in future studies.

Huijbers PM ，Graat EA ，Haenen AP ，van Santen MG ，van Essen-Zandbergen A ，Mevius DJ ，van Duijkeren E ，van Hoek AH ... -  《-》

Extended-Spectrum Beta-Lactamase-/AmpC Beta-Lactamase-Producing Enterobacteriaceae in Broiler Farms: Transmission Dynamics at Farm Level.

Daehre K ，Projahn M ，Semmler T ，Roesler U ，Friese A ... -  《-》

Methicillin-resistant Staphylococcus aureus and extended-spectrum and AmpC β-lactamase-producing Escherichia coli in broilers and in people living and/or working on organic broiler farms.

The aim of this study was to estimate the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum and AmpC β-lactamase (ESBL/AmpC)-producing Escherichia coli among broilers, and humans living and/or working on organic broiler farms; further characterise isolates; and compare these results with those from conventional farms. In the Netherlands, only 9 certified organic broiler farms were present. On 8 of these farms, 60 throat swabs and 20 cloacal swabs were taken per farm for MRSA and ESBL/AmpC-E. coli detection, respectively, at an average age of both 34 (T1) and 68 (T2) days. Faecal swabs and questionnaires were returned by 27 out of 36 humans. For selected ESBL/AmpC-producing E. coli isolates, phylogenetic groups, β-lactamase genes, plasmid families, and sequence types were determined. MRSA was not detected in broiler and human samples. ESBL/AmpC-producing E. coli were isolated from broilers on 7/8 farms at T1 and on all farms at T2. Furthermore, 3 farmers at T1, and 2 farmers and 1 family member at T2 were positive. Genes found in broilers and humans were almost exclusively blaCTX-M-1 and blaCMY-2. Given the high overall human ESBL/AmpC-prevalence (18.5%), which is similar to conventional farms, contact with live broilers is assumed a risk factor for carriage. Farm and sample-level prevalence at T1 are consistent with those from conventional farms. At T2, just before slaughter, sample-level prevalence of ESBL/AmpC-E. coli appears to have decreased (94.3% vs. 80%), which could have important consequences for contamination of retail meat.

Huijbers PM ，van Hoek AH ，Graat EA ，Haenen AP ，Florijn A ，Hengeveld PD ，van Duijkeren E ... -  《-》