Reciprocal relationships in antibiotic resistance of Salmonella spp. carried by wild birds and fish in the danube delta

Purpose: Salmonella spp represents one of the most important pathogens for numerous animal species also holding a strong zoonotic potential, found in most variable habitats, including touristic areas such as the Danube Delta. We hypothesized that: a) domestic animals/wild rodents will represent the major source for fecal pollution of the area and therefore b) the antibiotic resistance of the Salmonella spp. in other wild inhabitants will be high, thus posing an increased public health risk. Methods & Materials: Samples (n = 52) were obtained in the summer season from Letea (45°20′24″N 29°32′13″E) and Sfantu Gheorghe (44°53′47.0″N 29°35′38.0″E), two tourist sites in the Danube Delta Biosphere Reserve, from birds (Calidris feruginea, Calidris minuta, Charadius dubius, Parus major, Parus caeruleus, Fringilla coelebs, Phyrulla phyrulla, Paser montanus, Carduelis carduelis, Pica pica) and fish (Tinca tinca, Perca fluviatilis, Silurus glanis, Cyprinus carpio, Esox lucius) and were processed by bacteriological methods (Mac Conkey, Oxoid, API 20E test, bioMerieux). The antibiotic sensitivity patterns (Kirby Bauer) to penicillin, ampicillin, kanamycin, amikacin, tetracycline, oxytetracycline, enrofloxacin, erythromycin, marbofloxacin, ciprofloxacina and chloramphenicol were adapted to CLSI standards. MAR (multiple antibiotic resistance) index for each strain as well as mean values were calculated and analyzed by Statistica program. PCR was carried out to identify invA (Salmonella specific), rfbJ (group B) and wzxC1 (group C) genes encoding antibiotic resistance. Results: Salmonellae were present in 52.12% of the samples. The results indicated a high MAR index in birds (0.63–1.00, x = 0.84), over that recorded in fish (0.36–0.91, x = 0.65). Salmonella spp. was 100% resistant to penicillin, amikacin and erythromycin in birds and ampicillin and chloramphenicol in fish. Neither in birds nor in fish, none of the antibiotics achieved full effectiveness (100% sensitivity). invA gene was found in 100% of the bird and 66.6% of the fish strains, rfbJ (group B) gene was found in none, while wzxC1 gene was found in three bird isolates (11.53%). Conclusion: The results confirmed that b) the antibiotic resistance of the isolates was high, posing a high health risk to the ecosystem but not a) the exclusive domestic animal/wild rodent origin of the bacteria. Supported by PNII/61-2012.