Could bedbug bites transmit MRSA?

January 12th, 2015

Given the bodice-ripping élan of the vampire in current culture, one may presume that other creatures feeding on precious blood by night may be afforded similar status. Alas, such is not the case for the lowly bedbug, a parasite viewed with abject disgust, a character more befitting of Franz Kafka than Bram Stoker. As surging infestations continue to be reported of Cimex lectularius in hotels, lodgings and even hospitals, there is some suggestion that part of the reasons is that the bugs have developed immunity to pesticides. That is, like their bacterial brethren, the exposed bedbugs have been selected out for resistance by the “antibiotic” as it were, and now are genetically conveying that trait to their hearty offspring. While the pesticide researchers and their exterminators are faced with leveling that playing field, the common question to the infection preventionist is “Can the bites transmit infections?” The standard answer has been “No,” with some qualification, even though on any given day the insects may be carrying a wide array of viruses, bacteria, protozoa, and parasitic worms. Research reveals that hepatitis B viral DNA can be detected in bed bugs up to 6 weeks after they feed on infectious blood, but no transmission of hepatitis B infection was found in a study using chimpanzees. With its high titers in the blood, HBV would be one of the prime suspects for transmission, but there have been no documented cases of infection via bedbugs with that virus nor with the generally less transmissible HCV or HIV. However, a recent letter to Emerging Infectious Diseases, raises that possibility that under certain conditions, bedbugs could serve as a vector for transmission of drug-resistant bacteria like methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin resistant enterococci (VRE). The authors report that “three patients, all residents of Vancouver’s Downtown Eastside—an impoverished community … with high rates of homelessness, poverty, HIV/AIDS, and injection drug use—were hospitalized and found to be infested with bedbugs.” Hypothesizing that the parasites may be vectors for the transmission of antimicrobial drug–resistant pathogens, they collected 5 bedbugs and tested them for drug-resistant organisms. For 2 patients, VRE was isolated from 1 bedbug each. These bacterial isolates were also resistant to ampicillin, teicoplanin, and aminoglycosides but susceptible to linezolid, quinupristin/dalfopristin, and tetracycline. For 1 other patient, MRSA was isolated from 3 bedbugs. All MRSA isolates had susceptibility patterns consistent with pulsed-field gel electrophoresis type USA300 (susceptible to vancomycin, clindamycin, trimethoprim/sulfamethoxasole, tetracycline, and rifampin; resistant to erythromycin). Thickening the plot, the authors note that irritation at the site of the bites can cause further skin abrasion, thereby providing an entry point for colonizing bacteria. S. aureus, which is commonly found on the skin and can cause cellulitis, has been reported to colonize the salivary glands of bedbugs for as long as 15 days. “However, although transient and persistent forms of colonization may play a role in disease transmission, we did not differentiate these forms because the clinical bedbug specimens were processed at the time of receipt in the laboratory,” they concluded. So no smoking gun, but the intuitive insight is that MRSA transmission may be possible with repeated bites by colonized bedbugs in the absence of routine hygiene. Hopefully, that rules most of us out, but the resurgence of bedbugs in areas of urban squalor is not likely confined to Vancouver. “Bedbugs carrying MRSA and/or VRE may have the potential to act as vectors for transmission,” the authors note. “…Bedbug carriage of MRSA, and the portal of entry provided through feeding, suggests a plausible potential mechanism for passive transmission of bacteria during a blood meal. Because of the insect’s ability to compromise the skin integrity of its host, and the propensity for S. aureus to invade damaged skin, bedbugs may serve to amplify MRSA infections in impoverished urban communities.”