The antibiotic resistome in Escherichia coli isolated from human, food, and animal sources.

AIMS: The aim of this study was to analyze and compare the prevalence and distribution of resistance genes in Escherichia coli genomes isolated from human clinical samples and animal-based foods worldwide. METHODS AND RESULTS: We download from NCBI Pathogen Detection Database the corresponding metadata of the 7,123 E. coli genome to access the information about the antimicrobial resistance gene content. The geographic location and the source of isolation were also obtained and compiled with the antimicrobial resistance gene for statistical analysis, results and discussion. Our criteria considered four groups for analyzing the antimicrobial resistance gene distribution. The first group of genomes from invasive clinical human (ICH) samples from countries with Human Development Index (HDI) ≥ 0.850; the second group of ICH from countries with an HDI ≤ 0.849; the third group of animal-based foods (ABF) from countries with HDI ≥ 0.850 and the fourth group of ABFs from countries with HDI ≤ 0.849. The most prevalent genes in the first group were blaCTX-M-134 (96.53%) and blaCTX-M-27 (86.35%). In the second group, ere(A) (95.96%), soxS (94.49%), qepA8 (90.81%), blaCTX-M-15 (85.66%), and fosA3 (80.88%). In the third group, the most frequently detected were aadA12 (98.5%), ant(3") (89.92%), and blaCARB-2 (87.2%). In the fourth group, aadA12 and aac(3)-IV were identified in 100% of the analyzed genomes. CONCLUSIONS: It was clear that the use of aminoglycosides in animal production is increasing the selective pressure on micro-organisms in both groups of countries since genes linked to aminoglycoside resistance are related to E. coli from ABF samples. The genomic profile of E. coli from HDI ≥ 0.850 countries indicates a selective pressure aimed at cephalosporins given the high prevalence in both sources.

Food safety concerns on polycyclic aromatic hydrocarbon contamination in fish products from estuarine bays throughout the American continent.

Estuarine environments are highly productive ecosystems exhibiting high fish biodiversity and richness. Estuarine bays yield significant fisheries catches, making them the target of extractive activities by both artisanal and industrial fisheries. These areas, however, are highly vulnerable to chemical contamination, such as polycyclic aromatic hydrocarbons (PAH) associated with oil spills and other anthropogenic activities, which can jeopardize animal health and consumer welfare. In this context, this systematic review aimed to evaluate PAH levels detected in seafood from estuarine bays throughout the entire American continent and assess potential human health risks. The PICO methodology was applied, and 27 experimental papers were evaluated. The findings indicate that naphthalene and pyrene are routinely detected at high concentrations in several species, such as white mullet and catfish, and that biliary metabolites concentrations tend to be higher than tissue levels. Although the effects of PAH on animal health are well defined due to several decades of assessments, food safety evaluations are still not routine, evidencing a significant knowledge gap and the need for legislative measures based on toxicological data.

Toxic metal and metalloid contamination in seafood from an eutrophic Brazilian estuary and associated public health risks.

Guanabara Bay (GB) is a highly contaminated estuarine system and an important fishing area in Southeastern Brazil. In this regard, knowledge concerning the association of certain contaminants in seafood to abiotic factors and human health risk assessments is still understudied. Therefore, this study aimed to quantify nine toxic elements in highly consumed crabs, shrimp, and squid, and associate the results with abiotic factors. A human health risk assessment was also performed. Our findings indicate that crabs are the main bioaccumulators. Transparency and depth were noteworthy for all three taxonomic groups. In general, contaminant concentrations were below the limits established by different international agencies, except for As, which was higher than the Brazilian limit (1 mg kg-1). However, the Hazard Index identified risks to consumer health for the ingestion of seafood. This study emphasizes the importance of jointly evaluating different toxic elements, for a more accurate health risk assessment.

Staphylococcus aureus biofilm: the role in disseminating antimicrobial resistance over the meat chain.

Staphylococcus aureus is responsible for severe skin and respiratory infections and food poisoning, resulting in hospitalizations and high morbidity worldwide. Staphylococci have extensive virulence mechanisms and antimicrobial resistance that pose a global challenge to contain the spread of infectious outbreaks. Antimicrobials are used as growth promoters, and for prevention and treatment of infections in animals that provide us with food. The improvement of animal health is undeniable, but the selection of multidrug-resistant strains that can spread resistance genes among microorganisms is undesirable. The administration of sublethal doses of antimicrobials in farm animals causes stress to Staphylococci inducing the formation of a complex extracellular polymeric structure called biofilm. Such a structure may favor the persistence of infection by disseminating antimicrobial-resistant strains that can be consumed in contaminated food of animal origin. In ruminant mastitis and hospitals, the potential of the biofilm structure in the persistence of infections, especially those caused by S. aureus, has already been demonstrated, as well as its role as a source of resistant genes. In the meat production chain, the potential for persistent contamination by biofilm structure is evidently a worrying health risk . This review brings together studies demonstrating that biofilm production facilitates the exchange of mobile genetic elements and random mutations in S. aureus strains within the structure. This contributes to the emergence of more resistant clonal complexes and, with biofilm support, persists in the meat production chain.

Baseline titanium levels of three highly consumed invertebrates from an eutrophic estuary in southeastern Brazil.

Titanium (Ti) is considered a contaminant of emerging interest, as it displays toxic potential and has been increasingly employed in everyday products, pharmaceuticals, and food additives, mainly in nanoparticle form. However, several knowledge gaps are still noted, especially concerning its dynamics in the water. In this context, this study aimed to quantify total Ti concentrations in highly consumed swimming crabs, squid, and shrimp from an important estuary located in southeastern Brazil. Ti concentrations were higher than those reported in most studies carried out worldwide. Animal length and weight, as well as, depth, transparency, dissolved oxygen, and salinity, significantly influence Ti concentrations in the animals. Human health risks were also noted after calculating a simulated exposure to titanium dioxide, especially considering the uncertainties regarding the effects of this element and the absence of regulatory limits.

Revisiting the Biological Behavior of Salmonella enterica in Hydric Resources: A Meta-Analysis Study Addressing the Critical Role of Environmental Water on Food Safety and Public Health.

The increasing number of studies reporting the presence of Salmonella in environmental water sources suggests that it is beyond incidental findings originated from sparse fecal contamination events. However, there is no consensus on the occurrence of Salmonella as its relative serovar representation across non-recycled water sources. We conducted a meta-analysis of proportions by fitting a random-effects model using the restricted maximum-likelihood estimator to obtain the weighted average proportion and between-study variance associated with the occurrence of Salmonella in water sources. Moreover, meta-regression and non-parametric supervised machine learning method were performed to predict the effect of moderators on the frequency of Salmonella in non-recycled water sources. Three sequential steps (identification of information sources, screening and eligibility) were performed to obtain a preliminary selection from identified abstracts and article titles. Questions related to the frequency of Salmonella in aquatic environments, as well as putative differences in the relative frequencies of the reported Salmonella serovars and the role of potential variable moderators (sample source, country, and sample volume) were formulated according to the population, intervention, comparison, and outcome method (PICO). The results were reported according to the Preferred Reporting Items for Systematic Review and Meta-Analyzes statement (PRISMA). A total of 26 eligible papers reporting 148 different Salmonella serovars were retrieved. According to our model, the Salmonella frequency in non-recycled water sources was 0.19 [CI: 0.14; 0.25]. The source of water was identified as the most import variable affecting the frequency of Salmonella, estimated as 0.31 and 0.17% for surface and groundwater, respectively. There was a higher frequency of Salmonella in countries with lower human development index (HDI). Small volume samples of surface water resulted in lower detectable Salmonella frequencies both in high and low HDI regions. Relative frequencies of the 148 serovars were significantly affected only by HDI and volume. Considering that serovars representation can also be affected by water sample volume, efforts toward the standardization of water samplings for monitoring purposes should be considered. Further approaches such as metagenomics could provide more comprehensive insights about the microbial ecology of fresh water and its importance for the quality and safety of agricultural products.

Nucleic Acid-Based Nanobiosensor (NAB) Used for Salmonella Detection in Foods: A Systematic Review.

Salmonella bacteria is a foodborne pathogen found mainly in food products causing severe symptoms in the individual, such as diarrhea, fever, and abdominal cramps after consuming the infected food, which can be fatal in some severe cases. Rapid and selective methods to detect Salmonella bacteria can prevent outbreaks when ingesting contaminated food. Nanobiosensors are a highly sensitive, simple, faster, and lower cost method for the rapid detection of Salmonella, an alternative to conventional enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) techniques. This study systematically searched and analyzed literature data related to nucleic acid-based nanobiosensors (NABs) with nanomaterials to detect Salmonella in food, retrieved from three databases, published between 2010 and 2021. We extracted data and critically analyzed the effect of nanomaterial functionalized with aptamer or DNA at the limit of detection (LOD). Among the nanomaterials, gold nanoparticles (AuNPs) were the most used nanomaterial in studies due to their unique optical properties of the metal, followed by magnetic nanoparticles (MNPs) of Fe3O4, copper nanoparticles (CuNPs), and also hybrid nanomaterials multiwalled carbon nanotubes (c-MWCNT/AuNP), QD/UCNP-MB (quantum dotes upconverting nanoparticle of magnetic beads), and cadmium telluride quantum dots (CdTe QDs@MNPs) showed excellent LOD values. The transducers used for detection also varied from electrochemical, fluorescent, surface-enhanced Raman spectroscopy (SERS), RAMAN spectroscopy, and mainly colorimetric due to the possibility of visualizing the detection result with the naked eye. Furthermore, we show the magnetic separation system capable of detecting the target amplification of the genetic material. Finally, we present perspectives, future research, and opportunities to use point-of-care (POC) diagnostic devices as a faster and lower cost approach for detecting Salmonella in food as they prove to be viable for resource-constrained environments such as field-based or economically limited conditions.

The Role of the Ecotoxicology Applied to Seafood as a Tool for Human Health Risk Assessments Concerning Polycyclic Aromatic Hydrocarbons.

BACKGROUND: Polycyclic aromatic hydrocarbons (PAHs) are persistent pollutants routinely detected in aquatic ecosystems. It is, therefore, necessary to assess the link between deleterious marine biota PAH effects, especially in commercialized and consumed animals, environmental health status, and potential human health risks originating from the consumption of contaminated seafood products. Thus, this review seeks to verify the relationships of ecotoxicological studies in determining effect and safety concentrations on animals routinely consumed by humans. METHODS: A total of 52 published studies between 2011 and 2021, indexed in three databases, were selected following the PICO methodology, and information on test animals, evaluated PAH, and endpoints were extracted. RESULTS: Benzo(a)pyrene and phenanthrene were the most investigated PAHs in terms of biomarkers and test organisms, and mussels were the most evaluated bioindicator species, with an emphasis on reproductive responses. Furthermore, despite the apparent correlation between environmental PAH dynamics and effects on aquatic biota and human health, few assessments have been performed in a multidisciplinary manner to evaluate these three variables together. CONCLUSIONS: The links between human and environmental sciences must be strengthened to enable complete and realistic toxicity assessments as despite the application of seafood assessments, especially to mussels, in bioassays, the connection between toxicological animal responses and risks associated with their consumption is still understudied.

A Systematic Review on Metal Dynamics and Marine Toxicity Risk Assessment Using Crustaceans as Bioindicators.

Metals, many of which are potentially toxic, are present in the aquatic environment originated from both natural and anthropogenic sources. In these ecosystems, these elements are mostly deposited in the sediment, followed by water dissolution, potentially contaminating resident biota. Among several aquatic animals, crustaceans are considered excellent bioindicators, as they live in close contact with contaminated sediment. The accumulation of metal, whether they are classified as essential, when in excessive quantities or nonessential, not only cause damage to the health of these animals, but also to the man who consumes seafood. Among the main toxic elements to animal and human health are aluminum, arsenic, cadmium, chromium, copper, lead, mercury, nickel and silver. In this context, this systematic review aimed to investigate the dynamics of these metals in water, the main bioaccumulative tissues in crustaceans, the effects of these contaminants on animal and human health, and the regulatory limits for these metals worldwide. A total of 91 articles were selected for this review, and an additional 68 articles not found in the three assessed databases were considered essential and included, totaling 159 articles published between 2010 and 2020. Our results indicate that both chemical speciation and abiotic factors such as pH, oxygen and salinity in aquatic environments affect element bioavailability, dynamics, and toxicity. Among crustaceans, crabs are considered the main bioindicator biological system, with the hepatopancreas appearing as the main bioaccumulator organ. Studies indicate that exposure to these elements may result in nervous, respiratory, and reproductive system effects in both animals and humans. Finally, many studies indicate that the concentrations of these elements in crustaceans intended for human consumption exceed limits established by international organizations, both with regard to seafood metal contents and well as daily, weekly, or monthly intake limits set for humans, indicating consumer health risks.

Interactions between mercury and environmental factors: A chemometric assessment in seafood from an eutrophic estuary in southeastern Brazil.

Guanabara Bay (GB) is an estuary in Brazil, constantly the target of pollutants, such as mercury (Hg). Thus, our study aimed to evaluate (i) total mercury (THg) content in shrimp and squid species from GB; (ii) associate THg content to contamination in swimming crabs; (iii) explore potential differences between species, and size; (iv) correlate abiotic water data to the determined THg contents; (v) verify if Hg concentrations are below acceptable limits. Swimming crabs showed greater Hg contamination compared to other species. For shrimp only biometric variables are related to Hg, while for squid, only abiotic. Only squids did not show a correlation between Hg and animal size. Finally, the detected Hg values are below the tolerable limits established by legislations. Our results indicate that the dynamics of Hg contamination differs between groups and that further studies are needed to elucidate the mechanisms that affect bioaccumulation in different species.

Arsenic in shellfish: A systematic review of its dynamics and potential health risks.

Arsenic is the most toxic element for humans. Presenting naturally in aquatic ecosystems and due to anthropogenic action, this semi-metal transfers to shellfish through the food chain. This systematic review aims to explain the dynamic of arsenic in the marine aquatic system, investigating factors that affect its bioaccumulation. A total of 64 articles were considered from three databases. The key abiotic factor influencing the presence of arsenic in shellfish is anthropogenic contamination, followed by geographic location. The crucial biotic factor is the genetics of each species of shellfish, including their diet habits, habitat close to the sediment, metabolic abilities, physiological activities of organisms, and metal levels in their habitats and food. Finally, arsenic presents an affinity for specific tissues in shellfish. Despite containing mostly less toxic organic arsenic, shellfish are a relevant source of arsenic in the human diet.

Antimicrobial resistance genes in bacteria from animal-based foods.

Antimicrobial resistance is a worldwide public health threat. Farm animals are important sources of bacteria containing antimicrobial resistance genes (ARGs). Although the use of antimicrobials in aquaculture and livestock has been reduced in several countries, these compounds are still routinely applied in animal production, and contribute to ARGs emergence and spread among bacteria. ARGs are transmitted to humans mainly through the consumption of products of animal origin (PAO). Bacteria can present intrinsic resistance, and once antimicrobials are administered, this resistance may be selected and multiply. The exchange of genetic material is another mechanism used by bacteria to acquire resistance. Some of the main ARGs found in bacteria present in PAO are the bla, mcr-1, cfr and tet genes, which are directly associated to antibiotic resistance in the human clinic.

Frequency of Antimicrobial Resistance Genes in Salmonella From Brazil by in silico Whole-Genome Sequencing Analysis: An Overview of the Last Four Decades.

Salmonella is a leading human pathogen and a significant public health concern worldwide. Massive food production and distribution have contributed to this pathogen dissemination, which, combined with antimicrobial resistance (AMR), creates new control challenges in food safety. The development of AMR is a natural phenomenon and can occur in the bacterial evolutionary process. However, the overuse and the misuse of antimicrobial drugs in humans and in animals have increased AMR selective pressure. In Brazil, there is an accuracy lack in AMR frequency in Salmonella because too many isolates are under-investigated for genetic and phenotypic AMR by the Brazilian health authorities and the research community. This underreporting situation makes the comprehension of the real level of Salmonella AMR in the country difficult. The present study aimed to use bioinformatics tools for a rapid in silico screening of the genetic antimicrobial resistance profile of Salmonella through whole-genome sequences (WGS). A total of 930 whole-genome sequences of Salmonella were retrieved from the public database of the National Biotechnology Information Center (NCBI). A total of 65 distinct resistance genes were detected, and the most frequent ones were tet(A), sul2, and fosA7. Nine point mutations were detected in total, and parC at the 57 position (threonine → serine) was the highest frequent substitution (26.7%, 249/930), followed by gyrA at the 83 position (serine → phenylalanine) (20.0%, 186/930) and at the 87 position (aspartic acid → asparagine) (15.7%, 146/930). The in silico prediction of resistance phenotype showed that 58.0% (540/930) of the strains can display a multidrug resistance (MDR) profile. Ciprofloxacin and nalidixic acid were the antimicrobial drugs with the highest frequency rates of the predicted phenotype resistance among the strains. The temporal analysis through the last four decades showed increased frequency rates of antimicrobial resistance genes and predicted resistance phenotypes in the 2000s and the 2010s when compared with the 1980s and 1990s. The results presented herein contributed significantly to the understanding of the strategic use of WGS associated with in silico analysis and the predictions for the determination of AMR in Salmonella from Brazil.

Dredging Activities Carried Out in a Brazilian Estuary Affect Mercury Levels in Swimming Crabs.

(1) Although suffers from intense pollution inputs, Guanabara Bay, the most socioeconomically and environmentally important estuary in Rio de Janeiro, Brazil, is still home to a diverse fauna, including several fish and crab species consumed by humans. The bay presents high sedimentation rates and sediment contamination, further aggravated by dredging processes carried out in recent years. In this context, this study aimed to verify the effect of the dredging process on total mercury (THg) concentrations at Guanabara Bay through swimming crab assessments sampled before (2016), during (2017), and after (2018) the dredging process, and mainly, if the detected concentrations can be harmful to consumer health; (2) Methods: Swimming crab samplings were carried out at the same time and sampling points in 2016, 2017 and 2018 and the total Hg was determined using a Direct Mercury Analyzer (DMA-80, Milestone, Bergamo, Italy); (3) Results: Increased Hg concentrations were observed during the dredging process, decreasing to lower values, close to the initial concentrations, at the end of the process. Some of the investigated abiotic factors favor Hg dynamics in the aquatic environment, while others were positively altered at some of the assessed sampling areas at the end of the dredging process; (4) Conclusions: Although crab Hg levels were below maximum permissible limits for human consumption, it is important to note that these animals are significantly consumed around Guanabara Bay, which may lead to public health issues in the long term.

Antimicrobial Resistance in Nontyphoidal Salmonella Isolates from Human and Swine Sources in Brazil: A Systematic Review of the Past Three Decades.

Salmonella is the leading cause of foodborne illnesses worldwide. The widespread use of antimicrobials as prophylactic, therapeutic, and growth promoters in both livestock and human medicine has resulted in selective pressure regarding antimicrobial-resistant (AMR) bacteria. This systematic review summarizes phenotypic antimicrobial resistance profiles in Salmonella isolates from human and swine sources between 1990 and 2018 in Brazil. The 20 studies that matched the eligibility criteria-isolates from pigs and humans from Brazil, between 1990 and 2016, containing information on the number of Salmonella isolates, and applying the disk diffusion susceptibility method-were included. During the assessed period, Salmonella strains isolated from swine sources displayed the highest resistance rates for tetracycline (20.3%) and sulfonamides (17.4%). In contrast, human isolates displayed the highest resistance rates against ampicillin (19.8%) and tetracycline (17%). Salmonella Typhimurium was the most frequent AMR isolate from both swine and human sources, corresponding to 67% of all isolates. From 2001 to 2005, tetracycline and ampicillin were the top antimicrobial resistance compounds, and the most frequently detected in swine and human sources, respectively. A total of 63 and 58 multiple drug resistance profiles were identified in swine and human isolates, respectively. Antimicrobial resistance has decreased throughout the 1990-2016 period, except for gentamicin and nalidixic acid in swine and human isolates, respectively. The results indicate that Salmonella isolated from human and swine display resistance against clinically important antimicrobials, indicating that swine are possibly one of the main vectors for spreading human salmonellosis in Brazil.

Seasonal influences on swimming crab mercury levels in an eutrophic estuary located in southeastern Brazil.

Although significantly impacted, Guanabara Bay (GB), located in southeastern Brazil, is still an important fishery source for the state of Rio de Janeiro. Hg contamination, in particular, is of concern in the area and should be regularly monitored, as Hg bioaccumulation and biomagnification processes may lead public health risks to the local human population due to the consumption of contaminated food items, such as crabs. In this context, the aim of the present study was to determine total Hg (THg) concentrations in swimming crabs from three GB areas and investigate the influence of biotic and abiotic factors on Hg concentrations at the beginning and the end of the rainy season. Crabs and water samples were obtained from three areas, inside the bay, at the mouth of the bay and outside the bay. A clear rainfall effect on the investigated abiotic variables was observed, with increased rainfall and temperatures noted at the end of the study period. Significant statistical correlations were observed between THg concentrations and the assessed abiotic variables at the three study points at the beginning and end of the rainy season. The rainy season was noted as directly affecting THg concentrations at Guanabara Bay and, consequently, swimming crab THg contents. THg concentrations in swimming crabs at Urca and at the Cagarras Islands were higher at the beginning of the rainy season compared to the end, while the opposite was observed for the sampling point outside the bay. Higher Hg concentrations were detected at the outermost point of the bay in relation to the Cagarras Islands, probably due to the local upwelling event. THg values in Callinectes sp. were higher than concentrations reported for other areas in Brazil but lower than other reports worldwide. Calculated THg intakes surpassed the maximum National Research Council permissible limits of 0.049 mg/week at all sampling stations during both seasons, raising public health concerns. Further research for longer monitoring periods during different seasons are essential to ascertain which climatic period is most critical regarding Hg availability at this anthropogenically-impacted estuary.

Mercury in aquatic fauna contamination: A systematic review on its dynamics and potential health risks.

Mercury is an important pollutant, released into aquatic ecosystems both naturally and by anthropogenic action. This element is transferred to aquatic organisms in different ways, causing potential health risks. In addition, mercury can be accumulated by humans, especially through the consumption of contaminated food. This systematic review aims to present mercury pathways, the major routes through which this element reaches the aquatic environment and its transformations until becoming available to living animals, leading to bioaccumulation and biomagnification phenomena. The key biotic and abiotic factors affecting such processes, the impact of mercury on animal and human health and the issue of seafood consumption as a source of chronic mercury contamination are also addressed. A total of 101 articles were retrieved from a standardized search on three databases (PubMed, Emabse, and Web of Science), in addition to 28 other studies not found on these databases but considered fundamental to this review (totaling 129 articles). Both biotic and abiotic factors display fundamental importance in mediating mercurial dynamics, i.e., muscle tropism, and salinity, respectively. Consequently, mercurial contamination in aquatic environments affects animal health, especially the risk of extinction species and also on human health, with methylmercury the main mercury species responsible for acute and chronic symptomatology.

Expression of the marA, soxS, acrB and ramA genes related to the AcrAB/TolC efflux pump in Salmonella entérica strains with and without quinolone resistance-determining regions gyrA gene mutations

Several studies have been conducted in recent years to elucidate the structure, function and significance of AcrB, MarA, SoxS and RamA in Salmonella enterica. In this study, the relative quantification of acrB, soxS, marA and ramA genes expression was evaluated in 14 strains of S. enterica, with or without accompanying mutations in the quinolone resistance-determining regions of the gyrA gene, that were exposed to ciprofloxacin during the exponential growth phase. The presence of ciprofloxacin during the log phase of bacterial growth activated the genes marA, soxS, ramA and acrB in all S. enterica strains analyzed in this study. The highest expression levels for acrB were observed in strains with gyrA mutation, and marA showed the highest expression in the strains without mutation. Considering only the strains with ciprofloxacin minimum inhibitory concentration values < 0.125 [1]g/mL (sensitive to ciprofloxacin), the most expressed gene in the strains both with and without mutations was acrB. In the strains with ciprofloxacin minimum inhibitory concentration values > 0.125 [1]g/mL (low susceptibility), with and without mutations in gyrA, the most expressed gene was marA. In this study, we observed that strains resistant to nalidixic acid may express genes associated with the efflux pump and the expression of the AcrAB-TolC pump genes seems to occur independently of mutations in gyrA.

Expression of the marA, soxS, acrB and ramA genes related to the AcrAB/TolC efflux pump in Salmonella enterica strains with and without quinolone resistance-determining regions gyrA gene mutations.

Several studies have been conducted in recent years to elucidate the structure, function and significance of AcrB, MarA, SoxS and RamA in Salmonella enterica. In this study, the relative quantification of acrB, soxS, marA and ramA genes expression was evaluated in 14 strains of S. enterica, with or without accompanying mutations in the quinolone resistance-determining regions of the gyrA gene, that were exposed to ciprofloxacin during the exponential growth phase. The presence of ciprofloxacin during the log phase of bacterial growth activated the genes marA, soxS, ramA and acrB in all S. enterica strains analyzed in this study. The highest expression levels for acrB were observed in strains with gyrA mutation, and marA showed the highest expression in the strains without mutation. Considering only the strains with ciprofloxacin minimum inhibitory concentration values<0.125 µg/mL (sensitive to ciprofloxacin), the most expressed gene in the strains both with and without mutations was acrB. In the strains with ciprofloxacin minimum inhibitory concentration values ≥ 0.125 µg/mL (low susceptibility), with and without mutations in gyrA, the most expressed gene was marA. In this study, we observed that strains resistant to nalidixic acid may express genes associated with the efflux pump and the expression of the AcrAB-TolC pump genes seems to occur independently of mutations in gyrA.

Detection of quinolone-resistance mutations in Salmonella spp. strains of epidemic and poultry origin

Mutations into codons Aspartate-87 (62 percent) and Serine-83 (38 percent) in QRDR of gyrA were identified in 105 Salmonella strains resistant to nalidixic acid (94 epidemic and 11 of poultry origin). The results show a high incidence of mutations associated to quinolone resistance but suggest association with others mechanisms of resistance.