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Background and Objectves:
Poultry farms are known as reservoirs of extended-spectrum β-lactamase (ESBL) and plasmid-mediated AmpC β-lactamase-(AmpC) producing Enterobacteriaceae. Therefore, cleaning and disinfection (C&D) between the fattening periods are crucial for an effective elimination of these microorganisms. However, the general procedure of C&D has never been questioned and studies investigating the possibility of transmission of ESBL- /AmpC-producing Enterobacteriaceae between fattening runs are missing. We therefore deeply surveyed broiler farms after C&D to identify possible niches for bacterial survival on broiler fattening farms.
Materials and Methods:
For the study we investigated a conventional broiler fattening farm in Germany. First, we identified ESBL- /AmpC- positive flocks based on boot swabs and pooled faeces samples from chicken at end of their fattening period. Following, we systematically sampled four of ESBL- /AmpC carriage positive barns after C&D. The disinfection was done twice with at first a formaldehyde fumigation followed by application of liquid disinfectants. Environmental samples i.e. gauze swabs as well as boot swabs from inside and outside the barn were taken and suspicious enterobacteria were isolated after cultivation (using MacConkey agar with 1 mg/l cefotaxime). Species identification was performed using MALDI-TOF, affiliation to ESBL- /AmpC was performed by real time PCR for resistance genes followed by sequencing. As an indicator for faecal contamination all samples were furthermore analysed for Enterococci using a selective agar (bile esculin azide agar).
Our results indicate that both microorganisms investigated can survive the process of C&D: on average 42,1% of the pre-enriched samples in the barns (n=38) were positive for EnterococciA and 3,9% positive for ESBL- /AmpC-producing EnterobacteriaceaeB. While the anteroom of the barn (n=22-23, no C&D) was much less contaminated (26,5%A vs. 1,1%B), the surrounding areas (n=7-9, no C&D) showed highest contamination at all: 87,4%A vs. 9,8%B.
Thereby, ESBL- /AmpC-producing Enterobacteria were only found in samples simultaneously contaminated with
Enterococci. In comparison to the initial sampling at the end of the fattening period, the isolates of our ESBL-/AmpC- producing Enterobacteria comprise identical resistance genes.
Summary and Conclusion:
The so far analysed stables are pre-selected by an initial screening of the ESBL-/ AmpC- status of the previous broiler flock at the end of the fattening periode. Only stables with positive flocks are included in our study. Our preliminary results from four out of five analysed stables demonstrate that there is a survival of resistant bacteria in cleaned and disinfected broiler fattening stables. Sequence analyses will follow to extensively compare the isolates before and after the process of C&D. Though, our data give evidences for a possible transmission of ESBL- /AmpC-producing Enterobacteriaceae from the former chicken flock to the newly arriving chicken. ESBL- /AmpC-producing Enterobacteria survive the process of C&D especially via hygienically critical niches such as scratches in the ground. Theses niches were also positive for Enterococci indicating a faecal contamination – a sign for an inadequate cleaning and disinfection. This knowledge is necessary to develop a concept for an optimisation of C&D especially according to these hotspots. An effective C&D is crucial to reduce the spread of ESBL-/AmpC- producing Enterobacteria in poultry farming.