Abstract
Natural aquatic environments represent one of the most important vehicles of bacterial dissemination. Therefore, we aimed to isolate staphylococci from surface waters and to investigate the presence of antimicrobial resistance genes and virulence factors as well as the genetic lineages of all Staphylococcus aureus isolates. Staphylococci were recovered from water samples collected from 78 surface waters, including rivers, streams, irrigation ditches, dams, lakes, and fountains. The presence of antimicrobial resistance genes and virulence factors was investigated by PCR. Multilocus sequence typing and spa-typing were performed in all S. aureus isolates. From the 78 water samples, 33 S. aureus, one S. pseudintermedius, and 51 coagulase-negative staphylococci (CoNS) were identified. Among the S. aureus isolates, four MRSA were identified, and all harbored the mecC gene. Fourteen S. aureus were susceptible to all antimicrobials tested and the remaining showed resistance to penicillin, erythromycin and/or tetracycline encoded by the blaZ, ermT, msr(A/B), tetL, and vgaA genes. Regarding the clonal lineages, one mecC-MRSA isolate belonged to spa-type t843 and sequence type (ST) 130 and the other three to t742 and ST425. The remaining S. aureus were ascribed 14 spa-types and 17 sequence types. Eleven species of CoNS were isolated: S. sciuri, S. lentus, S. xylosus, S. epidermidis, S. cohnii spp. urealyticus, S. vitulinus, S. caprae, S. carnosus spp. Carnosus, S. equorum, S. simulans, and S. succinus. Thirteen CoNS isolates had a multidrug resistance profile and carried the following genes: mecA, msr(A/B), mph(C), aph(3′)-IIIa, aac(6′)-Ie–aph(2′’)-Ia, dfrA, fusB, catpC221, and tetK. A high diversity of staphylococci was isolated from surface waters including mecCMRSA strains and isolates presenting multidrug-resistance profiles. Studies on the prevalence of antibiotic-resistant staphylococci in surface waters are still very scarce but extremely important to estimate the contribution of the aquatic environment in the spread of these bacteria.
Highlights
The incidence of antimicrobial resistant bacteria (ARB) is increasing worldwide and is becoming one of the greatest medical challenges of our time
These results are comparable with the results obtained by a similar study conducted in Spain in which 89.4% of the surface water samples were positive for staphylococci [21] and in Hawai‘i where 98.1% were positive for Staphylococcus spp
In the study by Heß and Gallert, the prevalence of staphylococci was investigated in sewage and in river waters and it was noted that the prevalence of S. saprophyticus was higher than S. sciuri group strains in sewage, but the percentage of S. saprophyticus decreased in favor of S. sciuri group isolates in river water [29]
Summary
The incidence of antimicrobial resistant bacteria (ARB) is increasing worldwide and is becoming one of the greatest medical challenges of our time. While antimicrobial resistance has existed for millions of years, the misuse and overuse of antimicrobial agents in the last decades has led to the development of multidrug-resistant bacteria some of which showing resistance to all classes of antimicrobials [2,3] These superbugs are mostly found in the hospital environment, current data has shown that these bacteria can spill over from their anthropogenic sources into natural ecosystems where they can create secondary reservoirs leading to the spread of these bacteria and their resistance determinants through the environment [4]. The genus Staphylococcus is composed of at least 50 species and 24 subspecies, of which, S. aureus, S. epidermidis, S. saprophyticus and S. pseudintermedius stand out for their capacity to cause human and animal infections [18]. The presence of S. aureus and CoNS in the aquatic environment, surface water and drinking water, has been reported across the globe [27,28,29,30,31,32]
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