Title : In vitro activity of colistin against pseudomonas aeruginosa with difficult-to-treat resistance isolates from critically ill burn patients
Pseudomonas aeruginosa is an opportunistic pathogen, commonly causing hospital-acquired infections in burn patients. P. aeruginosa with difficult-to-treat resistance (DTR-PA) is resistant to all of the following: piperacillin-tazobactam, ceftazidime, cefepime, aztreonam, meropenem, imipenem-cilastatin, ciprofloxacin and levofloxacin and presents a significant clinical challenge. In low- to-middle-income countries, where costly novel antipseudomonal antibiotics are not available, colistin remains an important option against multidrug resistant gram-negative bacteria, particularly P. aeruginosa.
The aim of this study was to investigate the in vitro susceptibility of DTR-PA to colistin and determine its minimum inhibitory concentration (MIC).
We conducted a monocentric retrospective study of clinical P. aeruginosa isolates collected from critically ill burn patients over a period of 5 years (2018-2022) .
Isolates were identified using conventional methods . Antimicrobial susceptibilities to amikacin, piperacillin-tazobactam, ceftazidime, cefepime, aztreonam, meropenem, imipenem-cilastatin, ciprofloxacin and levofloxacin were determined by the disk diffusion method. Susceptibility was assessed according to European Committee on Antimicrobial Susceptibility Testing breakpoints.
The MIC of colistin was determined using broth microdilution. Isolates with a colistin MIC ≤2 mg/L were considered to be susceptible.
During the study period, 150 non-repetitive strains of DTR-PA were isolated, accounting for 19,1% of all P. aeruginosa isolates from burn patients.
Most isolates were recovered from male patients (64%) of all ages. DTR-PA strains were obtained from pus/wound swabs (46%), followed by central catheter cultures (26%), blood (13%), respiratory samples (10,3) and urine (4,1%). Almost 98% of the isolates were resistant to amikacin. Only one isolate was found to be colistin resistant.
This study highlights the high prevalence of DTR-PA among critically ill burn patients. The majority of DTR-PA isolates remained susceptible to colistin. Effective antimicrobial stewardship is crucial to ensure the appropriate use of colistin in order to preserve this antibiotic of last resort.
Audience Take Away:
The emergence and spread of Pseudomonas aeruginosa with difficult-to-treat resistance are challenging given the already limited therapeutic options.
Colistin has excellent activity against Pseudomonas aeruginosa with difficult-to-treat resistance.
Constant surveillance of antimicrobial resistance is important.