ABSTRACT
Resistance to disinfectants used in hospital infection control measures, is emerging. Against the background of paucity of data on disinfectant effectiveness in our environment, this study aimed to detect Pseudomonas species resistance genes to commonly used disinfectants in hospitals in Benin City, Nigeria. A total of 1200 specimens obtained from Central Hospital (CHB), Stella Obasanjo Hospital (SOH) and University of Benin Teaching Hospital (UBTH), all in Benin City, were used for this study. The specimens consisted of 700 from environmental sources (sink, floor and bench tops) and 500 from various clinical specimens. The entire specimens were processed to recover Pseudomonas species using cetrimide agar. Emergent colonies were identified by organism’s colonial morphology, pigment production, motility, oxidase positivity, and ability to reduce nitrate to nitrites; definitive identification was done using molecular techniques. Disc susceptibility, minimum inhibitory concentration (MIC) of sodium hypochlorite and chlorhexidine as well as presence of efflux pump activity among the Pseudomonas isolates were determined by standard techniques. Presence of plasmid and Qac genes was detected by molecular techniques. A total of 178 and 138 presumptive Pseudomonas isolates were recovered from environmental and clinical specimens respectively. Of these, 14 and 20 were non-Pseudomonal isolates recovered from environmental and clinical specimens respectively, using molecular techniques. Generally and in UBTH only (both environmental and clinical), Pseudomonas aeruginosa and other Pseudomonas species were mostly recovered from sinks (p=0.0118; p=0.0001) and from wounds (p<0.0001) with other Pseudomonas species failing to reach statistical significance (p=0.0850). Environmental isolates from CHB and UBTH were more resistant to all antibiotics used except Aminoglycosides and flouroquinolones, while isolates from SOH exhibited resistance to βLactams antibiotics and gentamycin. Clinical isolates were generally more resistant to flouroquinolones and the β-Lactams, with aminoglycosides exhibiting moderate activity. MIC of sodium hypochlorite against Pseudomonas aeruginosa and other Pseudomonas species did not differ significantly (p=0.9555) in isolates from both environmental and clinical specimens. For chlorhexidine, Pseudomonas aeruginosa had significantly lower MIC (p=0.0036) compared to other Pseudomonas species (p>0.05) generally and from isolates recovered from UBTH. Among clinical isolates, there was no significant difference in MIC of chlorhexidine to Pseudomonas aeruginosa and other Pseudomonas species (p>0.05). A total of 51(18.09%) out of 282 Pseudomonas isolates possessed efflux pump activity. The prevalence of efflux pump did not differ significantly (p>0.05) between the 3 hospitals and in comparison between clinical and environmental isolates. However, Pseudomonas aeruginosa from clinical specimens had significantly higher prevalence of efflux pump than other Pseudomonas species (p=0.0077). A total of 183 (64.89%) out of 282 Pseudomonas isolates possessed qac genes. Generally, among clinical isolates, Pseudomonas aeruginosa had higher prevalence of qac genes than other Pseudomonas species (p<0.0001). The reverse was the case for environmental isolates where other Pseudomonas species had significantly higher prevalence of qac genes compared to Pseudomonas aeruginosa (p=0.0106). In CHB, clinical isolates of Pseudomonas aeruginosa had higher prevalence of qacE genes (p=0.0139) while their environmental counterparts had lower prevalence of qacE genes compared with other Pseudomonas species (p=0.0457). In UBTH, qacE∆1 and qacE+qacE∆1 genes predominated (p<0.05) among clinical isolates of Pseudomonas aeruginosa compared with other isolates of Pseudomonas species. Curing of plasmids resulted to loss of resistance to some antibiotics and reduction in MIC to sodium hypochlorite among some xv Pseudomonas isolates. Prudent use of sodium hypochlorite is advocated to stem the tide of high resistance to disinfectants.
