Ciencias Agropecuarias
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Item Evaluación de la resistencia de Proteus mirabilis a Quinolonas y Betalactámicos y su relación con factores de virulencia(Universidad Técnica de Ambato Maestría En Medicina Veterinaria, 2026-07) Borja Ramos, Alva Tatiana; Cruz Quintana, Sandra MargaritaAntimicrobial resistance is a growing threat to public health, veterinary medicine and food safety. Proteus mirabilis is an opportunistic Gram-negative bacillus recognized for its occurrence in animals, animal-derived foods and environments associated with the food chain. The aim of this study was to evaluate the resistance of P. mirabilis isolated from chicken meat to quinolones and β-lactams, and to determine its relationship with virulence factors of clinical, veterinary and epidemiological importance. The study was conducted using a non-experimental, cross-sectional and descriptive design. A total of 41 P. mirabilis strains preserved at the Microbiology and Molecular Biology Laboratory of the Universidad Técnica de Ambato were analysed. These strains originated from registered and non-registered retail outlets in Ambato canton. Resistance genes were detected by PCR: gyrA and aac (6’)-Ib-cr, associated with quinolone resistance, and blaTEM and blaCTX-M, associated with β-lactam resistance. The amplified products were visualised by agarose gel electrophoresis. In addition, virulence factors were assessed through haemolysis on blood agar and swarming motility. The results showed high frequencies of resistance genes. The gyrA gene was detected in 85.37% of the isolates and aac (6’)-Ib-cr in 80.49%. Regarding β-lactams, blaTEM was identified in 80.49% and blaCTX-M in 58.54% of the strains. These findings demonstrate that chicken meat may act as a reservoir of P. mirabilis carrying genetic determinants of antimicrobial resistance. The coexistence of resistance genes with haemolysis and swarming suggests a potential health risk; therefore, strengthening molecular surveillance, food safety measures and the rational use of antimicrobials under the One Health approach is recommended.Item Identificación molecular de Escherichia coli O157 H7 aislada en carne de pollo(Universidad Técnica de Ambato Carrera de Medicina Veterinaria, 2026-07) Guangasi Manobanda, Jenny Fernanda; Cruz Quintana, Sandra MargaritaEscherichia coli O157 is a foodborne pathogen capable of causing severe gastrointestinal diseases in humans, including hemorrhagic colitis and hemolytic uremic syndrome. The aim of this study was to molecularly identify Escherichia coli O157 isolated from chicken meat marketed in Ambato through the detection of the virulence genes Stx1, Stx2, rfbE, and fliC. A total of 31 bacterial isolates previously identified and preserved at the Molecular Biology Laboratory of the Faculty of Agricultural Sciences of the Technical University of Ambato were analyzed. Molecular detection of the target genes was performed using the Polymerase Chain Reaction (PCR) technique, followed by electrophoresis on 2% agarose gel for all genes and visualization of the amplified products using a transilluminator. The results showed that the stx1 gene was not detected in any of the isolates; however, the Stx2 gene was identified in 5 isolates (16.1%). Likewise, no amplification of the rfbE gene was observed in any of the samples, whereas the fliC gene was detected in all 31 isolates (100%). These findings suggest the presence of strains with virulence potential associated with the production of Shiga toxin type 2 and the H7 flagellar antigen, although without molecular evidence of the O157 somatic antigen. This research is framed within the field of food safety and public health, and its scientific contribution lies in expanding epidemiological knowledge and strengthening microbiological surveillance strategies for poultry-derived food products.Item Identificación de genes de virulencia (ipaH) en Shigella spp aisladas de carne de pollo que se expende en el cantón Ambato(2025-02) Toapaxi Chiquito Elizabeth Fernanda; Cruz Quintana Sandra MargaritaShigella spp. infection is usually contracted by consuming contaminated food, with poor hygiene in handling it being a key risk. Likewise, unsanitary conditions in animal slaughter can be an important source of meat contamination. This study focused on the identification of a virulence gene in Shigella spp. isolated from chicken meat marketed in the Ambato canton. Of the 17 Shigella strains used, they were previously isolated and identified using molecular techniques in previous research and were kept in the Microbiology and Molecular Biology Laboratory of the Faculty of Agricultural Sciences of the Technical University of Ambato. In particular, the ipaH gene, a key virulence marker of this bacteria, was investigated. For the detection and analysis of this gene, advanced molecular techniques were used, including the Polymerase Chain Reaction (PCR) and agarose gel electrophoresis. First, pure and diluted Shigella spp DNA, previously extracted from chicken meat samples, was used for subsequent amplification. In the PCR phase, a specific primer designed to amplify the target sequence corresponding to the ipaH gene, with a size of 423 base pairs (bp), was used. In conclusion, the literature review revealed a remarkable diversity of virulence factors, and the presence of the ipaH gene is included in all the references consulted. However, the results obtained in the PCR did not show amplification of the gene, which reflected a 0% prevalence of the ipaH gene in Shigella isolates previously obtained from chicken meat. Finally, according to epidemiological data collected in the last five years, the presence of shigellosis has been recorded in Ecuador. In this regard, it is relevant to note that, both in 2023 and in the research carried out in 2024, the existence of this disease in the province of Tungurahua is not reported, nor is the presence of the related gene in the isolated strains used for the study. However, it is observed that these strains continue to circulate in neighboring provinces.Item Detección de genes de resistencia a antibióticos betalactámicos (blaTEM y blaCTX-M) en Shigella spp. aislada de carne de pollo que se expende en la ciudad de Ambato(2025-02) Rubio Obando Gregory Matheo; Cruz Quintana Sandra MargaritaChicken meat is a widely consumed food that can act as a vehicle for the transmission of antibiotic-resistant pathogenic microorganisms. In this context, the main objective of this research was to determine the presence of the beta-lactam resistance genes blaTEM and blaCTX-M in Shigella spp. strains isolated from chicken meat sold in the city of Ambato. 17 samples of chicken meat were collected from slaughterhouses (9 samples) and informal sales points (8 samples), and phenotypic and molecular identification of the strains was performed. The Shigella species identified were S. sonnei (58.82%), S. flexneri (29.41%) and S. dysenteriae (11.77%). The blaTEM gene was detected in 23.53% of the samples analyzed, while blaCTX-M was present in 88.23%. Both resistant strains were found in S. sonnei and S. dysenteriae, but not in S. flexneri. The highest presence of these genes was found in samples from unregistered sales points, suggesting that inadequate hygienic-sanitary conditions contribute to the spread of resistant bacteria. The results obtained partially agree with previous studies carried out in other regions of Ecuador and Latin America, where the S. flexneri species has historically been the most prevalent. However, a change in epidemiology is observed, with a predominance of S. sonnei in the samples analyzed, which could be explained by the capacity of this species to acquire resistance genes more easily. This study highlights the importance of implementing sanitary control and surveillance measures in the chicken meat production and marketing chain, in order to prevent the spread of bacteria resistant to beta-lactam antibiotics and reduce the associated risks to public health.Item Presencia de genes de resistencia a los antibióticos en Escherichia coli aislada de carne de pollo que se expende en el cantón de Ambato(2024-11) Gómez Aillòn Diego José; Cruz Quintana Sandra MargaritaAntimicrobial resistance is currently a public health problem in Ecuador. It seems that the indiscriminate use of antibiotics in animal production is a way for the development of this resistance. E. coli is a pathogen that affects animals and people and has developed resistance to several antibiotics in recent years. Cephalosporins and quinolones are used in broiler production and are two families of antibiotics to which strains of E. coli They have shown resistance. This resistance is mainly mediated by resistance genes such as gyrA and blaCTXM. Studies have searched for these mechanisms in E. coli strains from chicken meat, as it is one of the main meats consumed in Ecuador. The present study aimed to evaluate the antibioresistance and the presence of resistance genes of 31 Escherichia coli strains to antibiotics. Antibioresistance was carried out by the agar diffusion method and the search for resistance genes through PCR. In this way, a Kruskall Wallis test and the Mann Whitney U test were performed for the antibioresistance data, and for the genes, prevalence and a chi-square test were analyzed, with a 95% confidence interval. The results for the antibioresistance of the strains were resistant to ciprofloxacin 45.1% and ceftriaxone 25.8% and the antibiotics that provided greater susceptibility were gentamicin and amikacin with a p≤0.05. For the gyrA genes of CIP and blaCTXM of CX there were prevalence of 100% and 96.77% respectively. When comparing the difference between the origin of the sales center and the resistance gene, there was no statistical difference p≥ 0.05 in both genes. Finding resistance to antibiotics gives us a warning that the indiscriminate use of these in the country's animal production could be an important factor for this resistance. The prevalence of genes is a guide to the main resistance mechanism that could be used by E. coli, such as mutations in genes and genes that encode enzymes that provide resistance. And finally, finding antibioresistance and resistance genes in chicken meat in the Ambato canton is a warning of the possible risk of transmissibility of resistant strains that could generate resistance to antibiotics in people. However, the current data in Ecuador on this possibility is not yet being studied with the importance of the case. Therefore, studies like this open a gap for us to analyze everything that antibioresistance implies and the repercussions on public health in Ecuador.Item Presencia de genes de resistencia a los antibióticos en Shigella spp. aislada de carne de pollo que se expende en el cantón de Ambato.(2024-11) Pazmiño Orozco Andrés Sebastián; Cruz Quintana Sandra MargaritaShigella spp. is a common causal agent of diarrheal diseases around the world. The treatment of choice for shigellosis is the administration of antibiotics. However, the resistance that Shigella spp. has developed to these molecules poses a major challenge in the need to find effective treatment alternatives. Transmission of Shigella spp. is via the fecal-oral route, however, infection can result from the ingestion of contaminated food where poor hygiene during handling can be considered a risk factor for the occurrence of disease. Likewise, unhygienic conditions during the slaughter of animals could constitute one of the main sources of contamination of meat for human consumption. In this research, we start from previous studies where, from samples of chicken meat taken from points of sale and slaughterhouses in Ambato, 17 strains of Shigella spp. were isolated and molecularly identified and some of them, showed marked resitance mainly to two antibiotics: amoxicillin-clavulanate (AMC) and ciprofloxacin (CIP). The aim of this investigation was to verify the presence of a resistance gene for each of the antibiotics described above. For AMC, the blaTEM gene was searched for, which encodes for class A ESBL (extended spectrum β-lactamases), finding a prevalence of 23.53%, while for CIP, the gyrA gene was searched for, which encodes for the A subunits of DNA gyrase, finding a prevalence of 100%. One of the resistance mechanisms for AMC would be the production of TEM-like ESBLs, while specific mutations in a small region near the start of the gyrA gene, called the quinolone resistance determining region (QRDR), have been widely linked to CIP resistance in Enterobacteriaceae.Item Evaluación de la sensibilidad antibiótica y presencia de genes de resistencia en Enterococcus gallinarum aislado en carne de pollo en Ambato(2024-08) Villacis Gamboa, David Alexander; Cruz Quintana, Sandra MargaritaEnterococcus gallinarum is a Gram-positive bacterium that grows in short chains and can be found in the gastrointestinal tract of animals and humans at temperatures ranging from 10 - 37ºC. The aim of the study was to evaluate the antibiotic sensitivity and presence of resistance genes in Enterococcus gallinarum isolated from chicken meat in Ambato. The Kirby Bauer method with antibiotic discs was used to evaluate the sensitivity and resistance to vancomycin, erythromycin, ciprofloxacin, amoxicillin + clavulanic acid and trimethopin + sulfamethasone. The antibiotic chosen to detect resistance genes was vancomycin by DNA extraction, PCR and electrophoresis. PCR primers VanA F and VanA R were used to amplify a band of 732 base pairs. Resistance to vancomycin, erythromycin, ciprofloxacin and sensitivity to amoxicillin + clavulanic acid and trimethopin + sulfamethasone was shown. No vancomycin resistance genes were detected and the main molecular mechanisms of resistance of Enterococcus gallinarum to vancomycin were investigated as efflux pumps, resistance genes and target site modification. It was concluded that Enterococcus gallinarum from chicken meat sold in the canton of Ambato is sensitive to clavulanic acid and trimethopin + sulfamethasone and resistant to vancomycin, erythromycin and ciprofloxacin. To vancomycin it does not present resistance genes, its main resistance mechanisms are resistance genes, efflux pumps, modification of the target point.Item Presencia de genes de resistencia a fluoroquinolonas y betalactámicos en Proteus mirabilis aislados en carne de pollo en el cantón Ambato(2024-08) Fiallos Barros, Lizbeth Estefanía; Cruz Quintana, Sandra MargaritaThis study focused on the identification and analysis of antimicrobial resistance genes in Proteus mirabilis strains isolated from chicken meat samples from the city of Ambato. In particular, two key genes were investigated: gyrA associated with resistance to fluoroquinolones, and blaTEM-1, related to beta-lactam resistance. For the detection and analysis of these genes, advanced molecular techniques were used, including Polymerase Chain Reaction (PCR) and gel electrophoresis. First, DNA extraction from the samples was performed using standardized methods that ensure purity and adequate concentration of DNA for subsequent amplification, in the PCR phase, specific primers were used to amplify the target sequences of the gyrA and blaTEM-1 genes. The results showed successful amplification of the gyrA gene in all samples analyzed, with a base size of 850 bp, confirming a 100% prevalence of this gene in Proteus mirabilis strains. On the other hand, the amplification of the blaTEM- 1 gene was not universal in all samples, it was detected in 58.3% of the strains analyzed. This finding suggests the presence of variability in beta-lactam resistance in the samples, indicating that although blaTEM-1 is a prevalent gene it is not the only resistance mechanism present. This result underscores the need to consider other betalactam resistance genes and other resistance mechanisms in future studies. This research provides detailed insight into antimicrobial resistance, the high prevalence of the gyrA gene and the considerable presence of the blaTEM-1 gene indicate significant resistance to fluoroquinolones and beta-lactams, respectively. These findings emphasize the importance of continuous and detailed monitoring of antimicrobial resistance in the food chain to implement effective control strategies and protect public health.Item Evaluación de la sensibilidad a los antibióticos y presencia de genes de resistencia en Lactococcus garvieae aislado en carne de pollo que se expende en Ambato(2024-08) Chávez Romero, Anderson Xavier; Cruz Quintana, Sandra MargaritaLactococcus garvieae is a Gram-positive pathogenic bacterium, considered an emerging zoonotic pathogen, as reports of human infection are increasing. In the present research work, the antibioresistance of the L. garvieae strain and the presence of resistance genes in L. garvieae isolated from chicken meat sold in Ambato were evaluated. Sensitivity was identified using the Kirby Bauer method for the following antibiotics: Linezolid, Ceftriaxone, Amoxicillin+clavulanic acid, Lincomycin and Oxytetracycline. After obtaining results where four of the five antibiotics were resistant: Linezolid, Ceftriaxone Lincomycin and Oxytetracycline where we chose oxytetracycline, which showed the highest resistance and is the most widely used antibiotic in livestock farming. An arduous investigation was carried out to identify resistance genes, tetD and tetA, then the DNA of L. garvieae was extracted by the method of Aljanabi & Martinez modified, the PCR technique was carried out with the corresponding primers of the genes and ended with an electrophoresis where it was not identified that it has tetD and tetA genes of resistance to oxytetracycline and finally it was investigated on the molecular mechanisms of resistance of L. garvieae to the different resistant antibiotics.Item Evaluación de la presencia de los genes de resistencia a antibióticos betalactámicos y glucopéptidos en Mammaliicoccus sciuri aislado de la carne de pollo que se expende en Ambato(2024-08) Barreno Mayorga, Jessica Fernanda; Cruz Quintana, Sandra MargaritaAntibiotic resistance represents a significant public health problem due to the ability of bacteria to cause difficult-to-treat infections. The objective of this research is to detect the presence of resistance genes to beta-lactam antibiotics (amoxicillin + clavulanic acid) and glycopeptides (vancomycin) in the bacteria Mammaliicoccus sciuri isolated from chicken meat sold in Ambato. The research was carried out by collecting Mamamlicocus samples isolated from chicken meat and analyzing them in the laboratory to determine the presence of the aforementioned resistance genes, using PCR, DNA extraction and electrophoresis. Obtaining as results the presence of resistance genes in beta-lactams with an amplification of the band of 162 bp but no amplification of glycopeptides was found, which means that there are different ways for the existence of resistance. The identification and monitoring of these genes are crucial to evaluate food safety and prevent the spread of resistant bacteria in the final food chain.