Contamination of drug-resistant Acinetobacter baumannii and its antibiotic resistance genes in the dust on the return vent filters of air-conditioners in hospital wards

Background: Acinetobacter baumannii ( A. baumannii) has been one of the predominant causative agents of nosocomial infections. The purpose of this research was to study the situation of drug-resistant A. baumannii contamination in the dust on the return vent filters of air-conditioners in health care settings. Methods The study was conducted in 34 wards of three tertiary hospitals in Wuhan from November 2018 to November 2021. The dust samples on the return vent filters of air-conditioners were collected and inoculated on chromogenic media. A. baumannii were identified by time of flight mass spectrometry. Susceptibility testings were performed on the isolates using the Kirby-Bauer disk diffusion technique. Ten β-lactam antibiotic resistance genes (ARGs) was detected by PCR and quantitative PCR. Results A total of 279 strains producing β-lactamases and carbapenems were screened from 218 dust samples. A. baumannii was detected in 16.97% (37/218) of dust samples. The positive rate of dust samples in different wards were as follows: intensive care unites (ICUs) 20.97% (13/62), surgical wards 20.51% (16/78) and internal medicine wards 10.26% (8/78). Of the 49 A. baumannii colonies isolated, 12 were multidrug-resistance A. baumannii (MDRAB) with the highest proportion in ICUs. The frequency of bla ADC , bla OXA−51 , bla OXA−23 and bla KPC , bla VIM , bla TEM , bla CTX−M , bla SHV in A. baumannii were 100.00% (49/49), 79.59% (39/49), 59.18% (29/49), 59.18% (29/49), 46.94% (23/49), 44.90% (22/49), 32.65% (16/49) and 14.29% (7/49), respectively. However, bla IMP and bla NDM−1 were not detected. The relative quantitative value of ARGs from high to low were bla ADC > bla OXA−51 > bla KPC > bla TEM > bla OXA−23 > bla CTX−M > bla VIM > bla SHV . Conclusion Drug-resistant A. baumannii was commom in the dust on the return vent filters of air-conditioners in hospital wards, especially in ICUs. ARGs of bla ADC , bla OXA−51 , and bla KPC genes were most in need of attention. The relative quantitative value of bla OXA−23 and bla TEM had a positive correlation with the drug resistance of A. baumannii .