Common Antibiotic Combinations for Multidrug-Resistant Gram-Negative Bacilli Isolated from Intensive Care Unit Infected Patients, Egypt.

Abstract

Background: Infections with multidrug-resistant Gram-negative bacilli (MDR GNB) represent a principal threat particularly in intensive care unit (ICU) patients as the lack of effective antimicrobial therapy constitutes a serious challenge. Antimicrobial combinations could be a possible alternative. However, the most effective combination remains to be determined.

Objectives: Aims of this study were to detect the incidence of MDR GNB infections among ICU patients in Al-Ahrar Teaching Hospital, Zagazig, Egypt, to determine the most effective antibiotic combination against them, and to screen them for the presence of five major carbapenemase genes.

Subjects and methods: In a cross-sectional study, GNB were isolated and identified from different clinical specimens collected from ICU patients diagnosed with healthcare-acquired infections (HAIs) in Al-Ahrar hospital over the period from May 2017 to Mars 2021. Isolates were tested for antibiotic susceptibility by the disc diffusion method. MDR strains were tested against three antimicrobial combinations by Epsilometer (E-test) and screened for the presence of five carbapenemase genes by polymerase chain reaction (PCR). 

Results: A total of 55 MDR isolates were obtained representing 58% of the isolated GNB. Ceftazidime/avibactam inhibited more than half of MDR isolates recording a 61.8% sensitivity ratio. The use of colistin/amikacin had a slightly higher synergistic effect on MDR isolates (27.4%) compared to amikacin/aztreonam combination (23.6%).  One or more carbapenemase gene have been detected in 52.7% of MDR isolates. bla_KPC was detected in 29.1% of MDR isolates and was the most frequent among the five tested carbapenemase genes. 

Conclusion: The incidence of MDRGNB infections is remarkably high in the ICU of Al-Ahrar Hospital with a high prevalence of carbapenemase genes. Among the tested antibiotic combinations, ceftazidime/avibactam demonstrated the best in-vitro performance against isolated MDR GNB.