By Stan Deresinski, MD
Clinical Professor of Medicine, Stanford University
SYNOPSIS: Multiple bacteria were identified in syringes discarded by injection drug users.
SOURCE: Wildenthal JA, Schwartz DJ, Nolan NS, et al. Everything but the kitchen sink: An analysis of bacterial and chemical contaminants found in syringe residue from people who inject drugs. Open Forum Infect Dis 2023;11:ofad628.
As Wildenthal and colleagues state, the United States is experiencing a syndemic resulting from a confluence of epidemics involving not only increasing numbers of drug overdoses, but the associated severe wounds involving injection sites and invasive infections, which include endocarditis. They investigated the basis for these complications by examining syringe residues for the presence of bacteria and, in addition, for chemical adulterants.
The investigators collected needles and syringes from sharps containers containing discarded injection equipment that were provided by drug outreach and harm reduction groups at four sites in St. Louis over a 12-month period. They sampled the syringes (but not the needles) by inserting swabs into the syringes after removal of the plungers. The swabs then were cultivated on a variety of media and incubated in a variety of conditions. Deoxyribonucleic acid (DNA) from individual bacterial isolates then underwent whole genome sequencing.
Bacteria were recovered in culture from 94 of 160 (58.8%) syringe residue samples, with polymicrobial growth in 38/160. Dozens of species were recovered, including many of medical importance. Among the latter, the most frequently isolated were: Bacillus cereus (33/160; 20.6%), Staphylococcus aureus (18.8%), and Pseudomonas aeruginosa (3.1%), with small numbers of Enterobacter spp., Klebsiella spp., Serratia marcescens, and coagulase-negative staphylococci. Thirteen of the samples contaminated with S. aureus demonstrated confluent growth after swab inoculation on mannitol salt agar.
In addition to microbiological evaluation, the syringe residues were examined for the presence of illicit drugs and chemical adulterants by mass spectrometry (MS), with 100 subjected to multiple reaction monitoring (MRM) targeted MS. Methamphetamines, fentanyl, or both were detected in 98/100 (98%), with 97/98 (99%) of these containing methamphetamines, 83/98 (85%) containing opioids, and with cocaine in 56 (57%). Fentanyl was detected in all 83 (100%) of residues containing an opioid, with 23/82 (28%) containing heroin or a heroin metabolite. In addition, targeted liquid chromatography identified, among other compounds, xylazine in 58/98 (59%) and quinine in 52/98 (53%).
COMMENTARY
Marks and colleagues recently reviewed the enormous problem of infectious complications associated with injection drug use.1 While the investigation reviewed here focused on bacteria, fungi such as Candida also cause infection in this population and, of course, there are the viral infections (human immunodeficiency virus, hepatitis B virus, hepatitis C virus) which may contaminate residual blood in the injection equipment. The investigators addressed the lack of detection of streptococci and oral anaerobic bacteria, which commonly are involved in infections in injection drug users, by suggesting these may be unable to survive on inanimate surfaces. They also raised the interesting possibility that needles, which they did not culture, could be a source of these infections as a result of the practice of licking needles before injection, which is reported to be practiced by 30% of injectors.
Consistent with other data, Wildenthal et al confirmed the fact that fentanyl and methamphetamines are the agents of choice among injection drug users (at least in St. Louis). Additional compounds of note also were identified. One, quinine, has well-known potential toxicity. They also confirmed concerns about concomitant injection of xylazine (“tranq”), a sedative used in veterinary medicine that is believed to have contributed to many fentanyl deaths by central nervous system depression. Its injection also has been associated with causing severe necrotizing wounds, which may become infected.
These findings confirm the importance of syringe access programs, “community-based prevention programs that can provide a range of services, including linkage to substance use disorder treatment; access to and disposal of sterile syringes and injection equipment; and vaccination, testing, and linkage to care and treatment for infectious diseases.”2
References
- Centers for Disease Control and Prevention. Syringe Services Programs (SSPs). Last reviewed Sept. 25, 2023. https://www.cdc.gov/ssp/index.html
- Marks LR, Nolan NS, Liang SY, et al. Infectious complications of injection drug use. Med Clin North Am 2022;106:187-200.
