An investigation into the microflora of heroin

In 2000, an unusual increase of morbidity and mortality among illegal injecting drug users in the UK and Ireland was reported and Clostridium novyi was identified as the likely source of the serious infection, although infections due to C. botulinum and Bacillus cereus were also reported. Because heroin was a possibile source of infection, this study investigated the microflora of heroin samples seized in England during 2000 and 2002. Two methods were developed for the examination of the microflora of heroin. The first consisted of suspension of the drug in maximum recovery diluent (MRD) which was inoculated directly into Clostridium Botulinum Isolation Cooked Meat Broth (CBI). The second method rendered the heroin soluble in citric acid, concentrated particulate material (and bacterial cells) by filtration and removed heroin residues by washing with citric acid and phosphate-buffered saline before placing the filter in CBI broth. Duplicate CBI broths from both methods were incubated without heating and after heating at 60°C for 30 min. Subcultures were made after incubation for 7 and 14 days on to eight different solid media. The methods were evaluated with heroin samples spiked with either C. botulinum or C. novyi spore suspensions; recovery of 10 spores in the original sample was demonstrated. Fifty-eight heroin samples were tested by citric acid solubilisation and 34 by the MRD suspension technique. Fifteen different gram-positive species of four genera were recognised. No fungi were isolated. Aerobic endospore-forming bacteria (Bacillus spp. and Paenibacillus macerans) were the predominant microflora isolated and at least one species was isolated from each sample. B. cereus was the most common species and was isolated from 95% of all samples, with B. licheniformis isolated from 40%. Between one and five samples yielded cultures of B. coagulans, B. laterosporus, B. pumilus, B. subtilis and P. macerans. Staphylococcus spp. were isolated from 23 (40%) samples; S. warneri and S. epidermidis were the most common and were cultured from 13 (22%) and 6 (10%) samples respectively. One or two samples yielded cultures of S. aureus, S. capitis and S. haemolyticus. The remainder of the flora detected comprised two samples contaminated with C. perfringens and two samples with either C. sordellii or C. tertium. Multiple bacterial species were isolated from 43 (74%) samples, a single species from the remaining 15. In 13 samples B. cereus alone was isolated, in one B. subtilis alone and in one sample B. pumilus alone. C. botulinum and C. novyi were not isolated from any of the heroin samples. Recommendations for the optimal examination of the microflora of heroin are given.