The outcome of the antimicrobial disc susceptibility tests followed by PCR, revealed that 81.8% of E. faecalis SNP profiles and 70.21% of E. faecium SNP CBL0137 nmr profiles were associated with antibiotic resistance. The highest percentage of antibiotic resistant E. faecalis was found at Paradise Point (C5) 37.7% followed by

Coombabah (C6) 22.2%, Jabiru Island (C4) 19.1%, Marina (C1) 15.5%, Santa Barbara (C3) 4.4% and Sanctuary Cove (C2) 2.2%. No antibiotic resistant E. faecium strains were found at Marina (C1) and Sanctuary Cove (C2). The highest percentage of antibiotic resistant E. faecium was found at Paradise Point (C5) 51.5% followed by Coombabah (C6) 21.2%, Jabiru Island (C4) 15.1% and Santa Barbara (C3) 12.1%. Phenotypic and genotypic antibiotic resistance profiles of E. faecalis and E. faecium at individual sampling sites are listed in additional files 5 and 6. Gentamicin resistance was more prevalent in E. faecalis (47% resistant and 16% intermediate resistant) and these strains contained the aac(6′)-aph(2′) gene. Whereas ciprofloxacin resistance is more common in E. faecium (12.7% resistant and 36.2% intermediate-resistant). According to previous studies, one of the factors used to determine ciprofloxacin resistance is the association with mutations in the DNA gyrase genes [34]. The sequencing results revealed that there were no mutations detected in gyrA gene of intermediate resistant strains,

however, amino acid changes were detected in five E. faecium isolates that were disc-resistant Immune system to ciprofloxacin. Amino acid changes at position 83 (serine to arginine) were found in two isolates belonging to SNP ID 9, whereas the remaining Buparlisib order three isolates, belonging to SNP ID 10 and 21 had an amino acid change at position 87 (glutamate to lysine). According to previous studies, glutamate

at position 87 can also be replaced by glycine in ciprofloxacin-resistant isolates, but this was not detected in our environmental isolates [34]. Tetracycline resistance was less common among E. faecalis (14%) and E. faecium (12.7%) strains. Of these, the tet(L) and tet(M) genes were the predominant genetic determinants. This finding is consistent with previous studies [48]. Ampicillin resistance was found in only six E. faecium strains. Ampicillin resistance was observed in both multi-drug resistant strains and in human-related strains. Previous studies have shown an amino acid substitution in ampicillin-resistant enterococci. Potentially significant mutations that confer ampicillin resistance are methionine to alanine substitution at position 485, an additional serine at position 466, and CB-5083 molecular weight replacement of a polar amino acid with a non-polar one (alanine or isoleucine) at position 558, 562, or 574. A glutamate to valine substitution at position 629 has also been associated with ampicillin resistance [49]. In the present study, an ampicillin-resistant E. faecium isolate with SNP ID 2 had alanine at position 485 and all the other ampicillin- resistant E.