Identifying and elucidating the resistance of Staphylococcus aureus isolated from hospital environment to conventional disinfectants


      • A total of 47 (19.1%) S. aureus strains were isolated from 245 hospital environmental samples.
      • Methicillin resistance was found in more than 85% of the isolates.
      • The isolates with qac genes (qacA, qacE, and qac∆E1) had higher MIC values to disinfectants tested.
      • This is the first study to report the presence of qacE gene in S. aureus.
      • The study found substantially higher MIC90 values to chlorhexidine (median = 128 µg/ml).



      Staphylococcus aureus is a nosocomial pathogen, detection and elucidation of its resistance mechanisms to conventional disinfectants may aid in limiting its spread on environmental surfaces in health care settings. In the current study, disinfectant susceptibility of S. aureus strains isolated from the hospital environment as well as possible associations between the presence of disinfectant-resistance genes and reduced susceptibility to disinfectants was investigated.


      A total of 245 samples were collected from the hospital environmental surfaces. The minimum inhibitory (MIC) and bactericidal concentrations (MBC) of disinfectants against S. aureus isolates were determined using the micro-broth dilution method. The qac genes (qacA, qacE, and qacΔE1) were detected by PCR and confirmed by sanger sequencing.


      A total of 47 S. aureus strains were isolated, with more than 85% of them showing methicillin resistance. The qacA, qacE, and qac∆E1 genes were found in 23.4%, 29.7%, and 4.2% isolates respectively. All the isolates with qac genes had higher MIC and MBC values to selected disinfectants.


      Significant methicillin resistant S. aureus (MRSA) contamination in the hospital environment was detected. Furthermore, higher qac gene frequencies were found in MRSA isolates that also correlated with higher MIC/MBC values to different disinfectants. The study proposes that hospitals should develop policies to determine disinfectant MICs against the common environmental isolates to contain the spread of resistant strains.

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