Carbapenem-Resistant Among Patients with Ventilator-Associated Pneumonia: Evaluation of Antibiotic Combinations and Susceptibility to New Antibiotics.

BACKGROUND

Carbapenemase-producing Gram-negative bacteria, particularly (), are at the forefront of the list of causative agents of ventilator-associated pneumonia (VAP). The treatment options for such infections are limited, and various antimicrobial combinations have been suggested as alternatives in clinical practice. New antibiotics, such as ceftazidime/avibactam, ceftolozane/tazobactam and cefiderocol, have shown advantages in both in vitro and clinical studies.

PURPOSE

To evaluate the in vitro effect of meropenem-ciprofloxacin and meropenem-colistin combinations on carbapenem-resistant (CR) VAP isolates and to determine their susceptibility to new antibiotics.

METHODS

Seventy-three isolates from 176 endotracheal samples from VAP cases were studied. Antibiotic susceptibility testing and phenotypic detection of extended-spectrum β lactamase (ESBL) and carbapenemase production were done. CR isolates were tested for the five predominant carbapenemase genes ( , , , and ). In vitro evaluation of meropenem-ciprofloxacin and meropenem-colistin combinations was done by MIC test strips. Susceptibility to new antibiotics was tested by disk diffusion method.

RESULTS

Sixty-three (86.3%) of the isolates were ESBL producers and 52 (71.2%) were carbapenem resistant. was the most prevalent carbapenemase gene (50%), followed by , (36.5%) then in (11.5%). and were not detected. Meropenem-ciprofloxacin combination showed indifferent effect on all isolates, while meropenem-colistin combination showed 25% synergism, 15.4% addition and 59.6% indifference. All (100%) CR isolates were resistant to ceftolozane/tazobactam and 79% were resistant to ceftazidime/avibactam, while 96% were sensitive to cefiderocol.

CONCLUSION

A high rate of carbapenem resistance exists among VAP isolates. Meropenem-colistin combination and cefiderocol appear to be potential treatment options for infections caused by CR . Resistance to the tested new β-lactam/β-lactamase inhibitors was high, signifying a major threat.