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Review
. 2025 May 29;15(11):1598.
doi: 10.3390/ani15111598.

Prevalence of ESBL-Resistant Genes in Birds in Italy-A Comprehensive Review

Muhammad Tahir Sarfraz Khan  1 , Nicoletta Formenti  2 , Giovanni Tosi  2 , Flavia Guarneri  2 , Federico Scali  2 , Muhammad Kashif Saleemi  3 , Eugenio Monti  1 , Giovanni Loris Alborali  2
Affiliations
Review

Prevalence of ESBL-Resistant Genes in Birds in Italy-A Comprehensive Review

Muhammad Tahir Sarfraz Khan et al. Animals (Basel). .

Abstract

Antimicrobial resistance (AMR) is a major global concern in both human and veterinary medicine. Among antimicrobial resistance (AMR) bacteria, Extended-Spectrum Beta-Lactamases (ESBLs) pose a serious health risk because infections can be difficult to treat. These Gram-negative bacteria can be frequently found in poultry and in Italy, where such protein production is established. ESBL-producing Escherichia coli, Salmonella and Klebsiella in chicken and turkey may pose a significant public health risk due to potential transmission between poultry and humans. This review aims to assess the prevalence of ESBL-producing E. coli, Salmonella and Klebsiella phenotypically and genotypically in Italian poultry, identifying the most common genes, detection methods and potential information gaps. An initial pool of 1462 studies found in scientific databases (Web of Sciences, PubMed, etc.) was screened and 29 were identified as eligible for our review. Of these studies, 79.3% investigated both phenotypic and genotypic ESBL expression while blaCTX-M, blaTEM and blaSHV were considered as targeted gene families. Large differences in prevalence were reported (0-100%). The blaCTX-M-1 and blaTEM-1 genes were the most prevalent in Italian territory. ESBL-producing E. coli, Salmonella and Klebsiella were frequently detected in farms and slaughterhouses, posing a potential threat to humans through contact (direct and indirect) with birds through handling, inhalation of infected dust, drinking contaminated water, ingestion of meat and meat products and the environment. Considering the frequent occurrence of ESBL-producing bacteria in Italian poultry, it is advisable to further improve biosecurity and to introduce more systematic surveillance. Additionally, the focus should be on the wild birds as they are ESBL carriers.

Keywords: ESBL-producing bacteria; ESBLs genes; Escherichia coli; Klebsiella; Salmonella; avian species; blaCTX-M; phenotypic test.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Prisma flow chart used for the screening process [48].
Figure 2
Figure 2
Three out of 29 studies (10.3%) collected samples in year 2015, 2018 and 2021 from different areas of the country. In terms of temporal distribution, years 2020, 2022 and 2023 were the years in which the most studies were conducted: 5 (17%), 4 (13.7%) and 6 (20.6%), respectively. Y axis shows the distribution of studies between 2000 and 2024.
Figure 3
Figure 3
A total of 3155 Eschresia coli (E. coli), 4099 Salmonella spp. and 404 Klebsiella spp. samples were collected in the 29 studies from all of Italy. The sample size varied considerably among studies for both E. coli (median 186; range 33–855) and Salmonella (median 612; range 6–1053) and Klebsiella, with only 2 samples (96 and 308).
Figure 4
Figure 4
The figures indicate (a) a flow diagram showing the cycle of antimicrobial resistance (AMR) transmission within poultry, human, agricultural settings and wild birds; (b) the map of Italy indicating the regions e.g., Northern, Central and Southern.
See this image and copyright information in PMC

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