Antimicrobial resistance of heterotrophic marine bacteria isolated from seawater and sands of recreational beaches with different organic pollution levels in southeastern Brazil: evidences of resistance dissemination

Antimicrobial resistance of marine heterotrophic bacteria to different antimicrobials agents were evaluated in seawater, dry and wet sands from three marine recreational beaches with different pollution levels. In all studied beaches, the greatest frequencies of resistance were found in relation to penicillin. on Gonzaguinha, the most polluted beach, 72.3% of all isolated strains showed simple resistance, whilst 8.33% had multiple resistance. The values found on Ilha Porchat beach, were 70.8% and 6.9% for simple and multiple resistances, respectively. on GuaraA(0), the less polluted beach, only 35.3% of isolated strains had simple resistance. Multiple resistance was not observed. While samples from Gonzaguinha and Ilha Porchat beach showed isolated strains resistant to seven and six different antimicrobial agents, respectively, samples from GuaraA(0) beach were resistant only to penicillin and erytromicin. The positive correlations obtained between the degree of seawater contamination and frequency and variability of bacterial resistance indicate that polluted marine recreational waters and sands are sources of resistant bacteria contributing thus, to the dissemination of bacterial resistance.

Antimicrobial resistance and species composition of Enterococcus spp. isolated from waters and sands of marine recreational beaches in Southeastern Brazil

Density, species composition and antimicrobial resistance in bacteria of the Enterococcus genus were evaluated in seawater and sands from 2 marine recreational beaches with different levels of pollution. The 2 beaches showed predominance of Enterococcus faecalis and Enterococcus faecium, in the water and the sand. Dry sand presented higher densities of Enterococcus sp. and higher frequency of resistant strains than wet sand and seawater. The beach with a higher degree of pollution presented higher percentages of resistant strains (66.7% and 61.5%, in sand and in water, respectively) and resistance to a larger number of antimicrobials compared with the less polluted beach, Ilha Porchat (35.7% and 31.25% of resistant strains in sand and water, respectively). in water samples, the highest frequencies of resistance were obtained against streptomycin (38.5%) and erythromycin (25%), whilst in sand, the highest frequencies were observed in relation to erythromycin and tetracycline (38.1% and 14.3%, respectively). These results show that water and sands from beaches with high indexes of faecal contamination of human origin may be potential sources of contamination by pathogens and contribute to the dissemination of bacterial resistance. (C) 2007 Elsevier Ltd. All rights reserved.

Are the preference and selection patterns of hermit crabs for gastropod shells species- or site-specific?

Experimental analyses of hermit crabs and their preferences for shells are essential to understand the intrinsic relationship of the crabs' dependence on shells, and may be useful to explain their shell use pattern in nature. The aim of this study was to evaluate the effect of crab species and site on the pattern of shell use, selection, and preference in the south-western Atlantic hermit crabs Pagurus brevidactylus and Pagurus criniticornis, comparing sympatric and allopatric populations. Differently from the traditional approach to evaluate shell preference by simply determining the shell selection pattern (i.e., the number of shells of each type selected), preference was defined (according to [Liszka, D., Underwood, AJ., 1990. An experimental design to determine preferences for gastropod shells by a hermit-crab. J. Exp. Mar. Biol. Ecol., 137(1), 47-62]) by the comparison of the number of crabs changing for a particular shell type when three options were given (Cerithium atratum, Morula nodulosa, and Tegula viridula) with the number of crabs changing for this same type when only this type was offered. The effect of crab species was tested at Cabelo Gordo Beach, where P. brevidacrylus was found occupying shells of C. atratum, M. nodulosa, and T viridula in similar frequencies, whereas P. criniticornis occupied predominantly shells of C atratum. In laboratory experiments the selection patterns of the two hermit-crab species for these three gastropods were different, with P criniticornis selecting mainly shells of C atratum, and R brevidactylus selecting more shells of M. nodulosa. The shell preference was also dependent on crab species, with P. criniticornis showing a clear preference for shells of C atratum, whereas P. brevidactylus did not show a preference for any of the tested shells. The effect of site was tested for the two species comparing data from Cabelo Gordo to Preta (P brevidactylus) and Araca beaches (P. criniticornis). The pattern of shell use, selection, and preference was demonstrated to be dependent on site only for P. brevidactylus. The results also showed that the shell use pattern of P criniticornis can be explained by its preference at both sites, whereas for P. brevidactylus it occurred only at Cabelo Gordo, where the absence of preference was correlated with the similar use of the three gastropod species studied. Finally, the results showed that the shell selection pattern cannot be considered as a measure of shell preference, since it overestimates crab selectivity. (C) 2009 Elsevier B.V. All rights reserved.