Diversidade e padrões de susceptilidade a antimicrobianos em bactérias isoladas de ostras (Crassostrea rhizophorae) e do ambiente aquático

Abstract

The main objective of the following research was to compare the bacterial microbiota present in the soft tissue (ST) and intravalvular liquid (IL) of oysters (Crassostrea hizophorae) and water surroundings from a cultivation structure, as well as from a natural bank, establishing antimicrobial resistance profiles among bacterial isolates. The material was collected at the rio Jaguaribe estuary in Fortim-CE, from October 2010 to March 2011. Temperature, salinity and pH levels from water samples ranged from 27 to 34 °C; 38 to 42, and from 8.13 to 8.42, respectively. Shell sizes, ST weight, IL volume, ST and IL pH ranged from 36.15 to 60.66 mm; 1.24 to 3.30 g; 0.65 to 3.26 mL; 6.11 to 6.64, and from 6.83 to 7.16, respectively. Concerning in-water CHB (culturable heterotrophic bacteria) counting, cultured oysters (CO) and wild oysters (WO) IL and ST, the average values for in colony forming units (CFU) were of 32 x 103 CFU/mL; 57 x 103 CFU/mL; 31.5 x 104 CFU/g; 17 x 103 CFU/mL; 31 x 103 CFU/mL, and 58.7 x 103 CFU/g, respectively. Average values for in-water Vibrio spp. counting, CO and SO of the IL and ST were of 33.7 CFU/mL; 113 CFU/mL; 40.5 x 103 CFU/g; 32.7 CFU/mL; 28.3 CFU/ml and 236 CFU/g, respectively. For environmental parameters, salinity only had influence (r> 0.9 and P = 0.02) on CHB countings in IL and ST collected during the rainy season. No relation was established between the environmental parameters and the culturable vibrios population. From the 118 CHB cultures isolated, 101 strains were identified and distributed in 14 genera. Aeromonas, Vibrio, and Bacillus were the most frequent. From the 68 strains of vibrios identified, the highest incidences were of V. ruber (25.0%) and V coralliilyticus (16.2%). Ampicillins (AMP), cefepime, cefotaxime were the antimicrobials to which isolates presented higher resistance rates (above 60%). Chloramphenicol (CLO) was the only drug 100% related to plasmid resistance among THB strains. Regarding the vibrios, the antibiotics were the following: Chloramphenicol, florfenicol, and gentamicin. The minimum inhibitory concentration ranged from 32 to > 128 µg/ml for penicillin G in Gram-positive THBs; 16 to > 128 µg/ml ampicillin in Gramnegative THBs; 16 to 128 µg/mL ampicillin for Vibrio spp. The results indicated the presence of antimicrobials multidrug-resistant strains and a significant share of mobile elements in these profiles. Besides the well-known microbiological hazards related to fresh clams’ intake, oysters may also play an important role as a resistance spreading site to several antimicrobial with potential use on both human and veterinary medicine.