Class 1 and 2 integrons and antibiotic resistance profile in Salmonella spp. from San Cristobal River, Laguna, Philippines

Infection with multidrug resistant bacteria is a significant public health concern. Bacteria culture of water samples (n=120) collected in San Cristobal River, Philippines, showed that half (n=60) were positive for Salmonella spp. Screening of all isolates (n=179) for susceptibility to antibiotics showed that most (76.4%; n=113) were positive for class 1 integrons, of which one isolate was also positive for the class 2 integron. The presence of class 1 integrons was associated with resistance to antibiotics (p<0.05). Sequencing of class 1 integron variable regions (VRs) differeciated 11 gene cassettes: dfrA1 or dfrA17; aadA1 or aadA2; blaCTX-M-2 or bla-OXA-1; SmdAB; CmlA1 and aaC 3-Id. However, sequencing of class 2 integron VR differenciated estX, sat2, and aadA1. These results provide insights into evolutionary changes within bacterial multidrug resistant cassettes, more accurately to estimate heath risk associated with the river water.