Genotypic, phylogenetic and antibioticresistance profiling of Pseudomonas aeruginosa from tertiary hospitals in Metro Manila

Abstract

Pseudomonas aeruginosa is known for being an opportunistic nosocomial pathogen that targets individuals with weakened and impaired immune systems (Poormasoomi, 2013). Due to its ability to employ many different antibiotic resistance mechanisms, including the novel New Delhi metallo-ß-lactamase (NDM-1) coded by blaNDM-1, it is becoming more difficult to treat (Strateva & Yordanov, 2009; Lambert, 2002). In the study, 30 isolates were obtained from three tertiary hospitals around Metro Manila, and were subjected to phylogenetic reconstruction using their partial 16S ribosomal RNA (rRNA) gene sequences, along with antibiotic susceptibility testing to reveal antibiotic resistance phenotypes. Contingency coefficient was used to determine the strength of association between the 16S rRNA sequences and the antibiotic-resistance phenotypes. The presence of blaNDM-1 in the isolates was also tested. The results revealed that there were seven 16S rRNA genotypes and 11 antibiotic resistance phenotypes, which were highly associated with each other based on contingency coefficient calculation but was statistically not significant (cc = 0.822, p>0.05). Shannon-Weiner Index revealed there was low genotypic diversity (H’ = 1.041), and Simpson"s Index revealed an intermediate level of dominance among genotypes (D = 0.558). blaNDM-1 was also not detected among the isolates, indicating the absence of the said gene in the isolates. Results suggest the presence of positive selection among P. aeruginosa strains on their antibiotic-resistance phenotype.