Emerging Biocide Resistance among Multidrug-Resistant Bacteria: Myth or Reality? A Pilot Study.

Context: Possible linkage between biocide and antibiotic resistance in bacteria is a major area of concern.

Aim: To evaluate the susceptibility of multidrug-resistant (MDR) bacteria to four commonly used biocides.

Settings and Design: A pilot study was conducted in a tertiary care hospital from April to November 2017.

Materials and Methods: Fifty-four MDR bacterial isolates, namely Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa , and Staphylococcus aureus , were obtained from various clinical samples of inpatients. These isolates were subjected to tube dilution method for determining minimum inhibitory concentration (MIC) of four commonly used biocides in our hospital, namely 5% w/v povidone iodine, absolute ethanol (99.9%), sodium hypochlorite (4% available chlorine), and quaternary ammonium compounds (QACs) (3.39%). Minimum bactericidal concentration (MBC) of these biocides was determined as per standard guidelines. Similar tests were also performed on corresponding American Type Culture Collection (ATCC) bacterial strains.

Statistical Analysis: The Fisher exact test.

Results: Twenty-two MDR bacterial isolates had higher MIC values for QACs than their corresponding ATCC strains. Statistically significant difference in proportion of test isolates exhibiting higher MIC values for QACs and absolute ethanol was observed ( P -value = 0.02). Twenty-four MDR bacterial isolates exhibited higher MBC values for sodium hypochlorite than their corresponding ATCC strains. The difference in proportion of test isolates exhibiting higher MBC values for sodium hypochlorite and absolute ethanol, respectively, was statistically significant ( P -value <0.0001). The difference in proportion of test isolates exhibiting higher MBC values for absolute ethanol versus QACs and povidone iodine, respectively, was statistically significant ( P -values = 0.0003 and 0.0076). Statistically significant differences in susceptibility to biocides among test isolates were also observed.

Conclusion: Emergence of biocide resistance among MDR bacteria poses a serious threat to our efforts in containing outbreaks of nosocomial infections.