Survival and susceptibility of Burkholderia cepacia complex in chlorhexidine gluconate and benzalkonium chloride

The Burkholderia cepacia complex (BCC) includes opportunistic pathogenic bacteria that have occasionally been recovered from various pharmaceutical products, including antiseptics and disinfectants. Plausible reasons for the contamination include intrinsic sources, such as inadequate process controls, especially for water or equipment used during product manufacture, or extrinsic sources, such as improper handling and dilution or distribution in contaminated containers. Because the survival of BCC in antiseptics is a concern to the public health and pharmaceutical industry, we determined minimum inhibitory concentrations (MICs) of 36 BCC strains against the antiseptics, following exposure to chlorhexidine gluconate (CHX) and benzalkonium chloride (BZK) solutions (1–500 µg/ml for each chemical). Susceptibility to CHX and BZK varied across the BCC strains and was recorded as mean 90.3 and 111.1 µg/ml, respectively, at initial inoculation, which was significantly higher than the 46.4 and 61.1 µg/ml levels measured for BCC incubated in water for 40 days. After determining antiseptic MICs of individual BCC strains, BCC recovery was measured on Tryptic Soy Agar (TSA), Reasoner’s Second Agar (R2A) and diluted preparations of these media under their sub-MICs. The survival of BCC was monitored for 14 days (336 h) in sub-MICs diluted to less than their antiseptic susceptible concentration value. Diluted TSA and R2A media exhibited greater efficiency of recovery for most BCC strains from the CHX and BZK solutions than full strength TSA or R2A. For BCC survival in antiseptic solutions, the cell number of BCC decreased rapidly within the first 20 min in both antiseptics, but after this, recovery remained constant in CHX and increased in BZK over the 14 day incubation period. The results indicate that BCC in water can remain viable with low susceptibility to antiseptics for 14 days, which suggests the necessity for improved detection methods and control measures to monitor BCC contamination in pharmaceutical products.