Análisis microbiológico y resistencia a antibióticos de la leche cruda de bovino comercializada en el mercado San Alfonso de la ciudad de Riobamba.

Abstract

A microbiological analysis and testing of antibiotic resistance of raw bovine milk sold the “San Alfonso” market in Riobamba city was carried out in order to determine bacteriological quality. The collection and transportation of the seven samples tested in each of the collected selections was conducted in accordance with the provisions of INEN Norm 0004. The microbiological indicators that were analyzed to determine the sanitary and hygiene quality were: Total Coliforms, Escherichia coli, Aerobic mesophilic and Staphylococcus aureus using Petrifilm 3M plates. In the case of total Coliforms, the most probable number technique was used on three of the seven samples along with standard method agar plating. The existence of microorganism of interest was verified by confirmatory test. The profile of antimicrobial resistance was performed by the agar diffusion method as according to Kirby Bauer. The total Coliform count exceeded the maximum levels permitted according to the Technical Regulation RTCR: 401-2006 IN 100% (seven out of seven) of the samples and also in that determined by the NMP, the three samples tested were in the range of 210 to 1100 CFU/ mL, thus being greather than the set value (20 NMP/mL) 42.9% (three out of seven) of the samples met the microbiological parameter for Escherichia coli. 14.28% (one out of seven) exceeded the standard value set by the NTE INEN (1.5x106 CFU/mL) for Aerobic mesophilic bacteria. The Staphylococcus aureus count turned out to be higher than the reference value (maximum 500 CFU/mL) ranging between 3.000 CFU/mL and 1.326.667 CFU/mL. Confirmatory tests coincided with the growth in Petrifilm plates thus substantiating the existence of bacterial agents. In 40% (two out of five) of the samples where Escherichia coli was detected, resistance to ampicilim was demonstrated and 20% (one out of five) showed resistance to kanamycin, streptomycin and tetracycline. 100% of the samples in which Staphylococcus aureus was detected were resistant only to penicillin and 100% of them were sensitive to ciprofloxacin, clindamycin, amikacin, tetracycline, cefoxitin and erythromycin. It was concluded that the bacteriological quality of raw milk being sold is deficient, and that the microorganism showed high resistance to ampicillin and penicillin antibiotics. It is recommended to the Ministry of Health to develop a permanent ongoing training and control using technical and trained staff to protect public health.