A study on antibiotic resistance and pigment production by locally isolated Pseudomonas aeruginosa

Abstract

This study aimed to investigate the phenotypic and antibiotic resistance characteristics of Pseudomonas aeruginosa isolates obtained from various clinical specimens. A total of 55 isolates were recovered from 390 samples, with the highest recovery from ear swabs, burns, and wound infections. The identification of P. aeruginosa was confirmed using morphological, biochemical, and selective culture methods. All isolates were Gram-negative, motile rods, oxidase- and catalase-positive, and demonstrated characteristic growth on cetrimide and MacConkey agar. IMViC testing showed negative results for indole, methyl red, and Voges–Proskauer, while citrate was utilized by all isolates. Antibiotic susceptibility profiling revealed variable resistance patterns. The highest resistance was noted for ticarcillin-clavulanate (98.18%) and cefepime (78.18%), while piperacillin-tazobactam showed the lowest resistance (18.18%). Alarmingly, colistin resistance was detected in 96.36% of the isolates based on MIC values (≥ 4 µg/mL), raising serious clinical concerns. Furthermore, 87% of the isolates exhibited multidrug resistance (MDR), and 18% were classified as extensively drug-resistant (XDR), reflecting a significant threat to treatment efficacy. All isolates produced βhemolysin on human blood agar and 100% of selected strains synthesized pyocyanin on King A agar, confirming the presence of key virulence factors. The high rates of resistance and virulence indicate an urgent need for surveillance, antibiotic stewardship, and the development of alternative treatment strategies. These findings contribute to the growing body of evidence on the clinical challenges posed by P. aeruginosa in healthcare settings.