CTX-M-2-producing Salmonella Typhimurium isolated from pediatric patients and poultry in Brazil

Salmonella enterica serotypes from human and nonhuman sources in Sao Paulo State, Brazil, 2004-2020

Salmonellosis ranks among the most frequently reported zoonosis worldwide and is often associated with foodborne outbreaks. Since the 1950s, the distribution of Salmonella serotypes in Sao Paulo State, Brazil, has been documented and periodically reported. In this study, we updated the data on the distribution of Salmonella serotypes received in our reference laboratory, isolated from human infections and nonhuman sources, from 2004 to 2020. In that period, a total of 9,014 Salmonella isolates were analyzed, of which 3,553 (39.4%) were recovered from human samples, mainly of stool (65%) and blood (25.6%), and 5,461 (60.6%) were isolated from nonhuman origins, such as animals (47.2%), food (27.7%) and animal environments (18.6%). In human isolates, a total of 104 serotypes were identified and the most frequent ones were Enteritidis, Typhimurium, S . I. 4,[5],12:i:-, Dublin and Typhi. A consistent reduction of the Enteritidis proportion was observed over the years. Among the 156 serotypes identified in isolates with nonhuman origins, Enteritidis, Mbandaka, Typhimurium, Agona and Anatum were ranked as the top five Salmonella serotypes; in more recent years, S . Heidelberg has increased in frequency. Although with different proportions, the top 10 prevalent serotypes were identified in both human and nonhuman origins, underscoring the role of animals, food products and environment as reservoirs of Salmonella with potential to cause human salmonellosis.

Global Spread and Molecular Characterization of CTX-M-Producing Salmonella Typhimurium Isolates

This study aimed to determine the global prevalence and molecular characterization of CTX-M-producing Salmonella Typhimurium isolates. A total of 330 (15.2%, 330/21779) bla_CTX-M-positive S. Typhimurium were obtained from the public databases in July 2021. Thirteen variants were found in the 330 members of the bla_CTX-M group, and bla_CTX-M-9 (26.4%, 88/330) was the most prevalent. The majority of bla_CTX-M-positive S. Typhimurium were obtained from humans (59.7%, 197/330) and animals (31.5%, 104/330). The number of bla_CTX-M-positive S. Typhimurium increased annually (p < 0.0001). These isolates were primarily found from China, the United Kingdom, Australia, the USA, and Germany. In addition, these isolates possessed 14 distinct sequence types (ST), and three predominated: ST34 (42.7%, 141/330), ST19 (37.0%, 122/330), and ST313 (10.3%, 34/330). The majority of ST34 S. Typhimurium isolates were distributed in China and mainly from swine. However, the majority of ST19 were distributed in the United Kingdom and Australia. Analysis of contigs showed that the major type of bla_CTX-M-carrying plasmid was identified as IncI plasmid (52.9%, 27/51) and IncHI2 plasmid (17.6%, 9/51) in 51 bla_CTX-M-positive S. Typhimurium isolates. In addition, WGS analysis further revealed that bla_CTX-M co-existed with nine antibiotic-resistant genes with a detection rate over 50%, conferring resistance to five classes of antimicrobials. The 154 virulence genes were detected among these isolates, of which 107 virulence genes were highly common. This study revealed that China has been severely contaminated by bla_CTX-M-positive S. Typhimurium isolates, these isolates possessed numerous ARGs and virulence genes, and highlighted that continued vigilance for bla_CTX-M-positive S. Typhimurium in animals and humans is urgently needed.

Isolation, characterization, and resistance profile of Salmonella spp. from chicken cuts

ABSTRACT The present study aimed at isolating and characterizing Salmonella spp. from chicken cuts marketed in Francisco Beltrão, PR, and verify the resistance profile of the isolates against antimicrobials used in human therapy. Samples of chicken cuts (n=40) were purchased from supermarkets and submitted to microbiological analysis for the detection of Salmonella spp. The suspected colonies underwent biochemical testing for the identification of enterobacteria. Four colonies were selected from each sample positive for Salmonella spp., totaling 28 isolates that were tested for antimicrobial sensitivity. Colonies that showed resistance to ceftriaxone were subjected to extended-spectrum beta-lactamases (ESBL). Among the analyzed chicken samples, seven (17.5%) showed biochemical behavior characteristic of Salmonella spp. Among the 28 isolates, seventeen different resistance profiles were found, of which 46.42% (n=13) had a multi-resistance profile, and 21.4% (n=6) of the isolates had a phenotype for ESBL production. The strains of Salmonella spp. isolated from chicken cuts found in this study showed a high level of resistance to antimicrobials of different classes and of last generations, these data serve as a warning, as they put the human treatment of salmonellosis at risk.

Whole-Genome Sequencing Reveals the Presence of the blaCTX-M-65 Gene in Extended-Spectrum β-Lactamase-Producing and Multi-Drug-Resistant Clones of Salmonella Serovar Infantis Isolated from Broiler Chicken Environments in the Galapagos Islands

Salmonella Infantis, a common contaminant of poultry products, is known to harbor mobile genetic elements that confer multi-drug resistance (MDR) and have been detected in many continents. Here, we report four MDR S. Infantis strains recovered from poultry house environments in Santa Cruz Island of the Galapagos showing extended-spectrum β-lactamase (ESBL) resistance and reduced fluoroquinolone susceptibility. Whole-genome sequencing (WGS) revealed the presence of the ESBL-conferring bla_CTX-M-65 gene in an IncFIB-like plasmid in three S. Infantis isolates. Multi-locus sequence typing (MLST) and single nucleotide variant/polymorphism (SNP) SNVPhyl analysis showed that the S. Infantis isolates belong to sequence type ST32, likely share a common ancestor, and are closely related (1–3 SNP difference) to bla_CTX-M-65-containing clinical and veterinary S. Infantis isolates from the United States and Latin America. Furthermore, phylogenetic analysis of SNPs following core-genome alignment (i.e., ParSNP) inferred close relatedness between the S. Infantis isolates from Galapagos and the United States. Prophage typing confirmed the close relationship among the Galapagos S. Infantis and was useful in distinguishing them from the United States isolates. This is the first report of MDR bla_CTX-M-65-containing S. Infantis in the Galapagos Islands and highlights the need for increased monitoring and surveillance programs to determine prevalence, sources, and reservoirs of MDR pathogens.

High occurrence of β-lactamase-producing Salmonella Heidelberg from poultry origin

Salmonella Heidelberg is commonly reported in foodborne outbreaks around the world, and chickens and poultry products are known as important source of these pathogen. Multidrug-resistant S. Heidelberg strains are disseminated into poultry production chair, which can lead to severe clinical infections in humans and of difficult to treat. This study aimed at evaluating the β-lactam susceptibility and genotypic relatedness of Salmonella Heidelberg at Brazilian poultry production chain. Sixty-two S. Heidelberg strains from poultry production chain (poultry, poultry meat and poultry farm) were used. All strains were evaluated to antimicrobial susceptibility by diffusion disk test, as well as β-lactam resistance genes. Genotypic relatedness was assessed by Pulsed-Field Gel Eletrophoresis, using Xba1 restriction enzyme. Forty-one strains were characterized as multidrug-resistant according to phenotype characterization. The resistance susceptibility revealed 31 distinct profiles, with higher prevalence of streptomycin (61/62), nalidixic acid (50/62), tetracycline (43/62) and β-lactam drugs (37/62). blaCMY-2 was the more frequent β-lactamase gene found (38/62); other resistance genes found were blaCTX-M (2/62), blaSHV (3/62) and blaTEM-1 (38/62). No carbapenemase genes was found. The Pulsed-Field Gel Electrophoresis showed 58 different profiles. Strains with a larger number of antimicrobial resistance were grouped into ten major clusters apart from others. The spread of resistance by ampC continues to rise, thereby turning concern to public health, since the β-lactam antimicrobials are used as a therapeutic treatment in humans.

Bonelli R, A. Penna B, P. Albuquerque J, M. Souza R, M. F. Cerqueira A. Antimicrobial Resistance in Farm Animals in Brazil: An Update Overview

In animal husbandry, antimicrobial agents have been administered as supplements to increase production over the last 60 years. Large-scale animal production has increased the importance of antibiotic management because it may favor the evolution of antimicrobial resistance and select resistant strains. Brazil is a significant producer and exporter of animal-derived food. Although Brazil is still preparing a national surveillance plan, several changes in legislation and timely programs have been implemented. Thus, Brazilian data on antimicrobial resistance in bacteria associated with animals come from official programs and the scientific community. This review aims to update and discuss the available Brazilian data on this topic, emphasizing legal aspects, incidence, and genetics of the resistance reported by studies published since 2009, focusing on farm animals and derived foods with the most global public health impact. Studies are related to poultry, cattle, and pigs, and mainly concentrate on non-typhoid Salmonella, Escherichia coli, and Staphylococcus aureus. We also describe legal aspects of antimicrobial use in this context; and the current occurrence of genetic elements associated with resistance to beta-lactams, colistin, and fluoroquinolones, among other antimicrobial agents. Data here presented may be useful to provide a better understanding of the Brazilian status on antimicrobial resistance related to farm animals and animal-derived food products.

Antimicrobial Resistance in Farm Animals in Brazil: An Update Overview

In animal husbandry, antimicrobial agents have been administered as supplements to increase production over the last 60 years. Large-scale animal production has increased the importance of antibiotic management because it may favor the evolution of antimicrobial resistance and select resistant strains. Brazil is a significant producer and exporter of animal-derived food. Although Brazil is still preparing a national surveillance plan, several changes in legislation and timely programs have been implemented. Thus, Brazilian data on antimicrobial resistance in bacteria associated with animals come from official programs and the scientific community. This review aims to update and discuss the available Brazilian data on this topic, emphasizing legal aspects, incidence, and genetics of the resistance reported by studies published since 2009, focusing on farm animals and derived foods with the most global public health impact. Studies are related to poultry, cattle, and pigs, and mainly concentrate on non-typhoid Salmonella, Escherichia coli, and Staphylococcus aureus. We also describe legal aspects of antimicrobial use in this context; and the current occurrence of genetic elements associated with resistance to beta-lactams, colistin, and fluoroquinolones, among other antimicrobial agents. Data here presented may be useful to provide a better understanding of the Brazilian status on antimicrobial resistance related to farm animals and animal-derived food products.

Food-to-Humans Bacterial Transmission

Microorganisms vehiculated by food might benefit health, cause minimal change within the equilibrium of the host microbial community or be associated with foodborne diseases. In this chapter we will focus on human pathogenic bacteria for which food is conclusively demonstrated as their transmission mode to human. We will describe the impact of foodborne diseases in public health, the reservoirs of foodborne pathogens (the environment, human and animals), the main bacterial pathogens and food vehicles causing human diseases, and the drivers for the transmission of foodborne diseases related to the food-chain, host or bacteria features. The implication of food-chain (foodborne pathogens and commensals) in the transmission of resistance to antibiotics relevant to the treatment of human infections is also evidenced. The multiplicity and interplay of drivers related to intensification, diversification and globalization of food production, consumer health status, preferences, lifestyles or behaviors, and bacteria adaptation to different challenges (stress tolerance and antimicrobial resistance) from farm to human, make the prevention of bacteria-food-human transmission a modern and continuous challenge. A global One Health approach is mandatory to better understand and minimize the transmission pathways of human pathogens, including multidrug-resistant pathogens and commensals, through food-chain.

Emergence of CMY-2-Producing Salmonella Heidelberg Associated with IncI1 Plasmids Isolated from Poultry in Brazil

In this study we report the characterization of plasmid-mediated CMY-2-producing Salmonella Heidelberg recovered from food, poultry, and poultry environment in Brazil, between 2014 and 2016. The bla_CMY-2 resistance gene was allocated in large (90-148 kb) IncI1 type transferable plasmids. Salmonella Heidelberg isolates were genetically related, indicating the dissemination of closely related isolates among food, poultry, and its environment. This is the first report of IncI1 replicon-types of plasmids encoding the bla_CMY-2 resistance gene in Salmonella Heidelberg isolates in Brazil, the world's biggest exporter of chickens.

Molecular characterization of Salmonella Typhimurium isolated in Brazil by CRISPR-MVLST

CRISPR-multi-locus virulence sequence typing (CRISPR-MVLST) was performed to type 92 S. Typhimurium strains isolated from humans and food sources between 1983 and 2013 in Brazil and assess the suitability of this methodology comparing it with PFGE already used for subtyping the same strains. Among the 92 S. Typhimurium strains studied, we identified 25 CRISPR1 alleles, 27 CRISPR2 alleles, 2 fimH alleles and 3 sseL alleles showing that the genetic variability is much higher in the CRISPRs loci than in the virulence genes. The CRISPR-MVLST analysis provided similar results to the PFGE previously published used to type the same set of strains, demonstrating that CRISPR-MVLST is a very efficient approach for subtyping S. Typhimurium serovar and can be used to complement and validate results obtained by the PFGE methodology.

Prevalence of Extended-Spectrum β-Lactamases CTX-M-8 and CTX-M-2-Producing Salmonella Serotypes from Clinical and Nonhuman Isolates in Brazil

We characterized extended-spectrum β-lactamases (ESBL) enzymes among Salmonella strains isolated in Brazil from 2009 to 2014. Salmonella recovered from both clinical and nonhuman (food, poultry, and environment) sources were subjected to antimicrobial susceptibility testing. β-lactamases genes were detected by polymerase chain reaction/sequencing; plasmid profiles and transferability were assessed by S1-pulsed field gel electrophoresis (PFGE). Genetic diversity was evaluated by XbaI-PFGE. Out of 630 Salmonella strains screened, 46 displayed ESBL phenotype, distributed across 11 different serotypes. bla_CTX-M-8 and bla_CTX-M-2 genes were detected at frequencies of 47% and 41%, respectively. bla_SHV-5 and bla_SHV-2 were also detected but in lower frequencies (4%, 2%). bla_TEM-1 gene was detected in 22% of the strains. Most of the ESBL genes were transferable by conjugation, and the respective bla_ESBL gene was detected in the recipient strain, indicating the location of ESBL determinants on transferable plasmids. XbaI-PFGE revealed genomic diversity of Salmonella Typhimurium bearing bla_CTX-M-2, bla_CTX-M-8, bla_TEM-1, and bla_SHV-2 genes. Salmonella Muenchen (harboring bla_CTX-M-2) and Salmonella Corvallis (bla_CTX-M-8 and bla_SHV-5) showed clonal relatedness within respective serotypes. Our findings underscore the occurrence of diverse ESBL genes in several Salmonella serotypes, reinforcing the need for continuous surveillance of resistance genes circulating in human and nonhuman sources.

Antimicrobial resistance in Enterobacteriaceae in Brazil: focus on β-lactams and polymyxins

During the last 30 years there has been a dissemination of plasmid-mediated β-lactamases in Enterobacteriaceae in Brazil. Extended spectrum β-lactamases (ESBL) are widely disseminated in the hospital setting and are detected in a lower frequency in the community setting. Cefotaximases are the most frequently detected ESBL type and Klebsiella pneumoniae is the predominant species among ESBL producers. Klebsiella pneumoniae carbapenemase-producing Enterobacteriaceae became widely disseminated in Brazil during the last decade and KPC production is currently the most frequent resistance mechanism (96.2%) in carbapenem resistant K. pneumoniae. To date KPC-2 is the only variant reported in Brazil. Polymyxin B resistance in KPC-2-producing K. pneumoniae has come to an alarming rate of 27.1% in 2015 in São Paulo, the largest city in Brazil. New Delhi metallo-β-lactamase was detected in Brazil in 2013, has been reported in different Brazilian states but are not widely disseminated. Antimicrobial resistance in Enterobacteriaceae in Brazil is a very serious problem that needs urgent actions which includes both more strict adherence to infection control measures and more judicious use of antimicrobials.

Virulence-associated genes, antimicrobial resistance and molecular typing of Salmonella Typhimurium strains isolated from swine from 2000 to 2012 in Brazil

AIMS

The aims of this study were to assess the pathogenic potential, antimicrobial resistance and genotypic diversity of Salmonella Typhimurium strains isolated in Brazil from swine (22) and the surrounding swine environment (5) from 2000 to 2012 and compare them to the profiles of 43 human strains isolated from 1983 to 2010, which had been previously studied.

METHODS AND RESULTS

The presence of 12 SPI-1, SPI-2 and plasmid genes was assessed by PCR, the antimicrobial susceptibility to 13 antimicrobials was determined by the disc diffusion assay and genotyping was performed using pulsed-field gel electrophoresis (PFGE), multiple-locus variable-number of tandem repeats analysis (MLVA) and ERIC-PCR. More than 77·8% of the swine strains carried 10 or more of the virulence markers. Ten (37%) strains isolated from swine were multi-drug resistant (MDR). All the molecular typing techniques grouped the strains in two main clusters. Some strains isolated from swine and humans were allocated together in the PFGE-B2, MLVA-A1, MLVA-B and ERIC-A1 clusters.

CONCLUSIONS

The genotyping results suggest that some strains isolated from swine and humans may descend from a common subtype and may indicate a possible risk of MDR S. Typhimurium with high frequency of virulence genes isolated from swine to contaminate humans in Brazil.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provided new information about the pathogenic potential, antimicrobial resistance and genotypic diversity of S. Typhimurium isolates from swine origin in Brazil, the fourth largest producer of pigs worldwide.

Genetic background of novel sequence types of CTX-M-8- and CTX-M-15-producing Escherichia coli and Klebsiella pneumoniae from public wastewater treatment plants in São Paulo, Brazil

The release of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae to the environment is a public health issue worldwide. The aim of this study was to investigate the genetic background of genes encoding ESBLs in wastewater treatment plants (WWTPs) in São Paulo, southeastern Brazil. In 2009, during a local surveillance study, seven ESBL-producing Enterobacteriaceae strains were recovered from five WWTPs and screened for ESBL genes and mobile genetic elements. Multilocus sequence typing (MLST) was carried out, and wild plasmids were transformed into electrocompetent Escherichia coli. S1-PFGE technique was used to verify the presence of high molecular weight plasmids in wild-type strains and in bla ESBL-containing E. coli transformants. Strains harbored bla CTX-M-8, bla CTX-M-15, and/or bla SHV-28. Sequencing results showed that bla CTX-M-8 and bla CTX-M-15 genes were associated with IS26. MLST revealed new sequence types for E. coli (ST4401, ST4402, ST4403, and ST4445) and Klebsiella pneumoniae (ST1574), except for one K. pneumoniae from ST307 and Enterobacter cloacae from ST131. PCR and S1-PFGE results showed CTX-M-producing E. coli transformants carried heavy plasmids sizing 48.5-209 kb, which belonged to IncI1, IncF, and IncM1 incompatibility groups. This is the first report of CTX-M-8 and SHV-28 enzymes in environmental samples, and the present results demonstrate the plasmid-mediated spread of CTX-M-encoding genes through five WWTPs in São Paulo, Brazil, suggesting WWTPs are hotspots for the transfer of ESBL genes and confirming the urgent need to improve the management of sewage in order to minimize the dissemination of resistance genes to the environment.

Salmonellosis: the role of poultry meat

Salmonellosis remains one of the most frequent food-borne zoonoses, constituting a worldwide major public health concern. Currently, at a global level, the main sources of infection for humans include meat products, including the consumption of contaminated poultry meat, in spite of the success of Salmonella control measures implemented in food-animal production of industrialized countries. In recent years, a shift in Salmonella serotypes related to poultry and poultry production has been reported in diverse geographical regions, being particularly associated with the spread of certain well-adapted clones. Moreover, antimicrobial resistance in non-typhoidal Salmonella is considered one of the major public health threats related with food-animal production, including the poultry production chain and poultry meat, which is an additional concern in the management of salmonellosis. The circulation of the same multidrug-resistant Salmonella clones and/or identical mobile genetic elements encoding antibiotic resistance genes from poultry to humans highlights this scenario. The purpose of this review was to provide an overview of the role of poultry meat on salmonellosis at a global scale and the main problems that could hinder the success of Salmonella control measures at animal production level. With the increasing globalization of foodstuffs like poultry meat, new problems and challenges might arise regarding salmonellosis control, making new integrated intervention strategies necessary along the food chain.

Comparison of Antibiotic Resistance and Virulence Factors among Escherichia coli Isolated from Conventional and Free-Range Poultry

Microbiological contamination in commercial poultry production has caused concerns for human health because of both the presence of pathogenic microorganisms and the increase in antimicrobial resistance in bacterial strains that can cause treatment failure of human infections. The aim of our study was to analyze the profile of antimicrobial resistance and virulence factors of E. coli isolates from chicken carcasses obtained from different farming systems (conventional and free-range poultry). A total of 156 E. coli strains were isolated and characterized for genes encoding virulence factors described in extraintestinal pathogenic E. coli (ExPEC). Antimicrobial susceptibility testing was performed for 15 antimicrobials, and strains were confirmed as extended spectrum of β-lactamases- (ESBLs-) producing E. coli by phenotypic and genotypic tests. The results indicated that strains from free-range poultry have fewer virulence factors than strains from conventional poultry. Strains from conventionally raised chickens had a higher frequency of antimicrobial resistance for all antibiotics tested and also exhibited genes encoding ESBL and AmpC, unlike free-range poultry isolates, which did not. Group 2 CTX-M and CIT were the most prevalent ESBL and AmpC genes, respectively. The farming systems of poultries can be related with the frequency of virulence factors and resistance to antimicrobials in bacteria.

β-Lactam Resistance Genes: Characterization, Epidemiology, and First Detection of blaCTX-M-1 and blaCTX-M-14 in Salmonella spp. Isolated from Poultry in Brazil-Brazil Ministry of Agriculture's Pathogen Reduction Program

Salmonella spp. are widespread in nature; however, human infections occur mainly through ingestion of contaminated food, specially poultry and eggs. In Brazil, the Ministry of Agriculture (MAPA) oversees food production in general, with the goal of preventing transmission of pathogens through the food chain. In 2004, MAPA initiated a program to monitor and control levels of Salmonella in poultry during slaughter. This study analyzes isolates from MAPA's program for β-lactam resistance and the resistance genes involved, as well as the geographic distributions of potentially clonal populations of resistant isolates within Brazil. Initially, 1,939 Salmonella spp. isolated between 2004 and 2011 were examined. These isolates were tested for antimicrobial susceptibility, and 100 isolates resistant or intermediate to ampicillin and ceftriaxone were screened initially for the presence of blaSHV, blaTEM, blaOXA, blaPSA, blaCMY-1, and blaCMY-2 genes. There were 55 isolates whose resistance genes were not identified by this panel and these isolates are the subject of this report. These 55 isolates were differentiated into 31 distinct ribogroups, with multiple β-lactam resistance genes, including AmpC blaCMY, blaTEM, blaCTX-M-1, blaCTX-M-2, blaCTX-M-8, and blaCTX-M-14. Isolates carrying variants of blaCTX-M were identified in three geographic regions. Salmonella carrying particular genetic variants of blaCTX-M and belonging to the same ribogroup were identified from multiple poultry slaughtering facilities. In some instances, these presumptive clonal-related isolates were from facilities over 300 miles apart, indicating potential clonal spread between two geographic regions. This is the first report of blaCTX-M-1 and blaCTX-M-14 in Salmonella in Brazil.

Evaluation of the Antibiotic Resistance and Virulence of Escherichia coli Strains Isolated from Chicken Carcasses in 2007 and 2013 from Paraná, Brazil

The frequent use of antimicrobials in commercial poultry production has raised concerns regarding the potential impact of antimicrobials on human health due to selection for resistant bacteria. Several studies have reported similarities between extraintestinal pathogenic Escherichia coli (ExPEC) strains isolated from birds and humans, indicating that these contaminant bacteria in poultry may be linked to human disease. The aim of our study was to analyze the frequency of antimicrobial resistance and virulence factors among E. coli strains isolated from commercial chicken carcasses in Paraná, Brazil, in 2007 and 2013. A total of 84 E. coli strains were isolated from chicken carcasses in 2007, and 121 E. coli strains were isolated in 2013. Polymerase chain reaction was used to detect virulence genes (hlyF, iss, ompT, iron, and iutA) and to determine phylogenetic classification. Antimicrobial susceptibility testing was performed using 15 antimicrobials. The strains were also confirmed as extended-spectrum β-lactamase (ESBL)-producing E. coli with phenotypic and genotypic tests. The results indicated that our strains harbored virulence genes characteristic of ExPEC, with the iutA gene being the most prevalent. The phylogenetic groups D and B1 were the most prevalent among the strains isolated in 2007 and 2013, respectively. There was an increase in the frequency of resistance to a majority of antimicrobials tested. An important finding in this study was the large number of ESBL-producing E. coli strains isolated from chicken carcasses in 2013, primarily for the group 2 cefotaximase (CTX-M) enzyme. ESBL production confers broad-spectrum resistance and is a health risk because ESBL genes are transferable from food-producing animals to humans via poultry meat. These findings suggest that our strains harbored virulence and resistance genes, which are often associated with plasmids that can facilitate their transmission between bacteria derived from different hosts, suggesting zoonotic risks.

Antimicrobial resistance among Enterobacteriaceae in South America: history, current dissemination status and associated socioeconomic factors

South America exhibits some of the higher rates of antimicrobial resistance in Enterobactericeae worldwide. This continent includes 12 independent countries with huge socioeconomic differences, where the ample access to antimicrobials, including counterfeit ones, coexists with ineffective health systems and sanitation problems, favoring the emergence and dissemination of resistant strains. This work presents a literature review concerning the evolution and current status of antimicrobial resistance threats found among Enterobacteriaceae in South America. Resistance to β-lactams, fluoroquinolones and aminoglycosides was emphasized along with description of key epidemiological studies that highlight the success of specific resistance determinants in different parts of the continent. In addition, a discussion regarding political and socioeconomic factors possibly related to the dissemination of antimicrobial resistant strains in clinical settings and at the community is presented. Finally, in order to assess the possible sources of resistant bacteria, we compile the current knowledge about the occurrence of antimicrobial resistance in isolates in South American' food, food-producing animals and off-hospitals environments. By addressing that intensive intercontinental commerce and tourism neutralizes the protective effect of geographic barriers, we provide arguments reinforcing that globally integrated efforts are needed to decelerate the emergence and dissemination of antimicrobial resistant strains.

Extended-spectrum cephalosporin-resistant Gram-negative organisms in livestock: an emerging problem for human health?

Escherichia coli, Salmonella spp. and Acinetobacter spp. are important human pathogens. Serious infections due to these organisms are usually treated with extended-spectrum cephalosporins (ESCs). However, in the past two decades we have faced a rapid increasing of infections and colonization caused by ESC-resistant (ESC-R) isolates due to production of extended-spectrum-β-lactamases (ESBLs), plasmid-mediated AmpCs (pAmpCs) and/or carbapenemase enzymes. This situation limits drastically our therapeutic armamentarium and puts under peril the human health. Animals are considered as potential reservoirs of multidrug-resistant (MDR) Gram-negative organisms. The massive and indiscriminate use of antibiotics in veterinary medicine has contributed to the selection of ESC-R E. coli, ESC-R Salmonella spp. and, to less extent, MDR Acinetobacter spp. among animals, food, and environment. This complex scenario is responsible for the expansion of these MDR organisms which may have life-threatening clinical significance. Nowadays, the prevalence of food-producing animals carrying ESC-R E. coli and ESC-R Salmonella (especially those producing CTX-M-type ESBLs and the CMY-2 pAmpC) has reached worryingly high values. More recently, the appearance of carbapenem-resistant isolates (i.e., VIM-1-producing Enterobacteriaceae and NDM-1 or OXA-23-producing Acinetobacter spp.) in livestock has even drawn greater concerns. In this review, we describe the aspects related to the spread of the above MDR organisms among pigs, cattle, and poultry, focusing on epidemiology, molecular mechanisms of resistance, impact of antibiotic use, and strategies to contain the overall problem. The link and the impact of ESC-R organisms of livestock origin for the human scenario are also discussed.