Abstract
The relationship between the multidrug-resistant (MDR) phenotype and biofilm-forming capacity has been a topic of extensive interest among biomedical scientists, as these two factors may have significant influence on the outcomes of infections. The aim of the present study was to establish a possible relationship between biofilm-forming capacity and the antibiotic-resistant phenotype in clinical Acinetobacter baumannii (A. baumannii) isolates. A total of n = 309 isolates were included in this study. Antimicrobial susceptibility testing and the phenotypic detection of resistance determinants were carried out. The capacity of isolates to produce biofilms was assessed using a crystal violet microtiter-plate-based method. Resistance rates were highest for ciprofloxacin (71.19%; n = 220), levofloxacin (n = 68.61%; n = 212), and trimethoprim-sulfamethoxazole (n = 66.02%; n = 209); 42.72% (n = 132) of isolates were classified as MDR; 22.65% (n = 70) of tested isolates were positive in the modified Hodge-test; the overexpression of efflux pumps had significant effects on the susceptibilities of meropenem, gentamicin, and ciprofloxacin in 14.24% (n = 44), 6.05% (n = 19), and 27.51% (n = 85), respectively; 9.39% (n = 29), 12.29% (n = 38), 22.97% (n = 71), and 55.35% (n = 170) of isolates were non-biofilm-producing and weak, moderate, and strong biofilm producers, respectively. A numerical, but statistically not significant, difference was identified between the MDR and non-MDR isolates regarding their biofilm-forming capacity (MDR: 0.495 ± 0.309 vs. non-MDR: 0.545 ± 0.283; p = 0.072), and no association was seen between resistance to individual antibiotics and biofilm formation. Based on numerical trends, MER-resistant isolates were the strongest biofilm producers (p = 0.067). Our study emphasizes the need for additional experiments to assess the role biofilms have in the pathogenesis of A. baumannii infections.
Highlights
In a recent meta-analysis of 114 studies, the estimated mortality of A. baumannii VAP has been reported at 42.6%, while other studies have shown that the mortality rate of the A. baumannii bacteremia in ICUs was between
Isolates were verified as A. baumannii, and they were included in the subsequent experiments
The antimicrobial resistance levels of the A. baumannii isolates included in the study were the following: CIP 71.19% (n = 220), LEV 68.61%
Summary
Microorganisms 2021, 9, 2384 menting Gram-negative bacteria (NGFNBs; including Pseudomonas aeruginosa, Acinetobacter spp., and Stenotrophomonas maltophilia) have increased considerably [1]. A. baumannii is an important opportunistic pathogen in nosocomial infections, which— traditionally considered a low-grade pathogen—has been implicated in a wide array of infectious syndromes, including bacteremia, pneumonia (especially ventilator-associated pneumonia (VAP)), urinary tract infections, and eye and wound infections, affecting patients with immunosuppression, severe underlying conditions, or patients in critical condition (treated in Intensive Care Units (ICUs)) [3,4,5,6]. The reported mortality rate of invasive A. baumannii infections is considerably high, ranging between 23% and 68% and between 0% and 64% for nosocomial and community-associated infections, respectively [8]. In a recent meta-analysis of 114 studies, the estimated mortality of A. baumannii VAP has been reported at 42.6% (95% CI, 37.2–48.1%), while other studies have shown that the mortality rate of the A. baumannii bacteremia in ICUs was between
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