INIQUI   05448
INSTITUTO DE INVESTIGACIONES PARA LA INDUSTRIA QUIMICA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Multiple antibiotic resistance of microorganism isolated from a water sample in Salta, Argentina
Autor/es:
CID, A. G.; LÓPEZ, G. M.; RAJAL, V. B.
Lugar:
Florianólois
Reunión:
Simposio; 17th International Symposium on Health-Related Water Microbiology - WaterMicro 2013; 2013
Resumen:
Since their discovery in the twentieth century, antibiotics have substantially reduced the threat caused by infectious diseases and their extensive use has contributed to the increase observed in life expectancy. However this progress is at risk because of the recent emergence and international spread of antibiotic resistant bacteria. Antimicrobial resistance is a natural biological phenomenon that can be amplified and accelerated by a variety of factors, including human practices. The abuse and over-use of antibiotics to treat any infection, real or not, has contributed to the emergence of resistant bacteria in recent years. Antibiotic residues are discharged into the environment, causing a selective pressure on bacteria, some of which can adapt and survive due to mutation and from there ahead they carry genes for resistance. These genes can then be transferred vertically and horizontally to other bacteria through different mechanisms. The great capacity of bacteria to transfer genes makes antibiotic resistance to accumulate and transport in the environment, constituting it in a large reservoir. All this contributes to the distribution of antibiotic resistance genes, which favors the emergence of multi-resistant bacteria that can cause infections increasingly difficult to treat. Thus, resistance to antibiotics has become a global public health problem, constituting an epidemic that must be treated by all the countries. AIMS: The aim of this study was to evaluate the presence of oxytetracycline resistant bacteria in a water sample taken from the Arenales River that flows through the city of Salta in Argentina. We also studied the resistance of the isolated bacteria against various commonly used antibiotics. METHODS: 164 colonies were isolated in the presence of oxytetracycline (42.7 µg ml-1) from a water sample from Arenales River, which crosses the city of Salta in northwestern Argentina. It was determined by disk diffusion method their sensitivity to 9 antibiotics: ciprofloxacin (CIP), ampicillin (AMN), cephalothin (CEP), nitrofurantoin (NIT), ampicillin sulbactam (AMS), trimethoprim-sulfamethoxazole (TMS), penicillin (PEN), nalidixic acid (NAL) and tetracycline (TET). The isolates with resistance to at least 6 antibiotics were selected and tested also by disk diffusion method for sensitivity to other 12 antibiotics: piperacillin tazobactam (TAZ), cefepime (FEP), amikacin (AKN), meropenem (MEM), imipenem (IMP), gentamicin (GEN), ceftazidime (CAZ), cefotaxime (CTX), levofloxacin (LVX), azithromycin (ZIT), norfloxacin (NOR) and amoxicillin-clavulanic acid (AMC). Morphology and response to Gram stain were studied. It was also evaluated their ability to ferment lactose by culture in Endo agar and the presence of catalase and oxidase. RESULTS: Twenty five strains were selected from a total of 164 colonies isolated in presence of oxytetracycline from the water sample collected in the Arenales River. All of them were Gram-negative and coccobacillus or rod-shaped bacteria. Fifteen were able to ferment lactose and tested negative for oxidase and positive for catalase, what suggests that they may belong to the Enterobacteriaceae family. While all of the isolates were resistant to tetracycline, penicillin and ampicillin, the antibiotics meropenem and imipenem inhibited the growth of all of them. More than half of the isolates resisted also cephalotin, nalidixic acid, trimethoprim-sulfamethoxazole, azithromycin, ampicillin sulbactam, norfloxacin, and levofloxacin. Regarding multiresistance, it can be observed in Figure 1 that more than 60% of the isolates were resistant to at least 9 antibiotics and almost 25% were resistant to more than the half of the 21 antibiotics tested. Figure 1: Multiresistance presented by the isolates. CONSLUSIONS: From these results, we conclude that water may be an important reservoir of antibiotic resistant microorganisms, which can be the result of the environment contamination with these drugs in combination with a high fecal contamination. Some commonly used antibiotics will be no longer effective to inhibit the growth of Gram-negative rods bacteria. Furthermore, the presence of bacteria that can resist a high number of antibiotics is disturbing, which may be the result of the wide spread of resistance genes in the environment.