A Five-Year Trend Analysis of Antibacterial Resistance Patterns Among Non-fermenting Gram-Negative Bacilli: A Retrospective Study From the ICU Settings of a Tertiary Care Hospital.

Introduction: Non-fermenting gram-negative bacilli (NFGNB) infections have emerged as a serious health concern in ICUs. Multi-drug resistant (MDR) strains of NFGNB can evolve by acquiring resistance genes to at least one agent in three or more antibacterial categories. This study aimed to analyse the prevalence of NFGNB, the distribution of MDR strains, and antibiotic resistance trends of NFGNB in different ICUs of a tertiary care hospital over a period of five years.

Materials And Methods: This retrospective study was conducted in a tertiary care teaching hospital in eastern India, including a total of 20,256 samples received from various ICUs over five years. Data retrieved from the Laboratory Information System (LIS) of the hospital, and repetitive isolates from the same patients, were excluded. All samples were processed according to standard microbiological protocols by automated systems. Data were entered into a Microsoft Excel spreadsheet (Microsoft® Corp., Redmond, WA, USA), analysed using Epi Info software, and presented using descriptive statistics. Chi-square and Fisher's exact tests (where appropriate) were used as tests of significance, with a p-value of <0.05 considered statistically significant.

Results: A total of 18,032 culture-positive samples out of 20,256 samples showed growth of 18,659 bacteria. Out of these, 952 isolates were NFGNB. The prevalence of NFGNB was found to be 5.10% among all isolated bacteria. The predominant sources were respiratory samples (37.3%). spp. emerged as the most prevalent NFGNB (46.5%), followed by spp. (31%) and spp. (14.3%). Among the NFGNB isolates, 61.76% exhibited MDR, with the highest prevalence of MDR strains seen in spp. (94.7%). Among the most prevalent NFGNB, spp., 64.8% were MDR strains. Trend analysis of antibiotic resistance patterns of spp. indicated a substantial increase for trimethoprim-sulfamethoxazole by 18.5%, minocycline (44.4%), amikacin (20.4%), and ceftazidime (7.4%), whereas there was a reduced trend in resistance to carbapenems (6.5%), ciprofloxacin (4.7%), and cefepime (3.7%) over five years. In spp., resistance to meropenem increased by 17.4%, and for ceftazidime (11.8%), amikacin (10.6%), and piperacillin-tazobactam (7.9%), whereas resistance to aztreonam diminished by 13.9%. spp. exhibited a 23.5% escalation in resistance to meropenem and ceftazidime (5.9%), while resistance to levofloxacin experienced a decrease of 30.2%.

Conclusions: The study showed the prevalence of various NFGNB as 5.10% in ICU settings, with spp. (46.5%) being the most common isolated bacteria. Notably, 61.76% of the isolates were MDR. Antibiotic trend analysis over five years showed increasing resistance of spp. to trimethoprim-sulfamethoxazole, minocycline, and ceftazidime, with improved susceptibility for carbapenems, ciprofloxacin, and cefepime. spp. showed increased susceptibility to aztreonam and rising resistance for meropenem, piperacillin-tazobactam, ceftazidime, and amikacin. In Burkholderia spp., there was increased susceptibility to levofloxacin and rising resistance to meropenem and ceftazidime. These findings focus on the need for vigilant antibiotic stewardship, with the adoption of appropriate infection prevention and control practices to restrict the emergence and spread of MDR NFGNB infections in ICU settings of hospitals.