Transferência do gene blaTEM entre Salmonella e Escherichia coli em condições de beneficiamento de produtos de origem animal: influência de um complexo de cobre

Abstract

The high prevalence of infection caused by eating contaminated food is a challenge for global public health, which is intensified by the increasing resistance to antimicrobials (RAM). As gene recombination is an important tool for disseminating bacterial resistance, the factors that promote it must be continuously investigated. Byproducts originating from the processing of products of animal origin such as chicken juice have already shown the ability to interfere in the mechanism of virulence of bacteria, which encourages research about their effect and of whey cheese on the transfer of resistance genes. The dissertation was divided into two chapters, the first with the bibliographic review about the subject, and the second with a scientific article whose objective was to evaluate the frequency of blaTEM gene transfer between Salmonella Heidelberg (SH) and Escherichia coli (EC) in different conditions that simulate the environment found in an industry that processes products of animal origin, and the influence of the Lu54 copper complex as a new alternative to mitigate RAM. For this, SH positive for blaTEM gene (resistant to ampicillin) was used as donor and, as a recipient, EC J53 AzR, resistant to sodic azide and sensible to ampicillin. The conjugation methods used were: 1) liquid medium/three hours of incubation, shaking; 2) solid medium/overnight and; 3) liquid medium/overnight. All the essays were carried out in the presence and absence of whey cheese (SL) and chicken juice (CJ). Recombination rates were confirmed by the phenotypic method (recovery in selective agar) and genotypic method (confirmation of the blaTEM gene by PCR) and calculated by the frequency of conjugation using the recipient (FCR). The concentration of 125μg/mL of Lu54 was established by the minimum inhibitory concentration in a microdilution test. Conjugation 1 was chosen for treatment with Lu54, as it showed an increase in FCR greater than 2.5 orders of magnitude in the presence of SL and CJ when compared to the absence of supplement (traditional). In conjugation 2, the FCR's were lower, less than 1%, while the conjugation in liquid medium/overnight showed a higher FCR than the first method only in SL. The presence of SL acidified the medium, which resulted in higher FCR. The Lu54 complex was tested in conjugation 1 and proved to be effective in controlling the transfer of blaTEM, as it reduced the FCR from 2.2 to 0.3% in the traditional test, from 8.2 to 1.7% in SL and 6.2 to 0.9% with CJ, that is equivalent to a reduction of 7.3, 4.8 and 6.9 times, respectively. The colonies of transconjugants tested had the blaTEM gene, confirming the effectiveness of the process. The results demonstrate that the presence of SL or CJ is able to increase gene transfer when present in liquid medium and the Lu54 copper complex is effective in reducing conjugation, being a promising alternative for controlling gene exchange and mitigating antimicrobial resistance, especially in dairy and meat processing industries.