Microbiology and Initial Antibiotic Therapy for Injection Drug Users and Non-Injection Drug Users with Cutaneous Abscesses in the Era of Community-associated Methicillin-resistantStaphylococcus aureus

Abstract

Objectives The incidence of cutaneous abscesses has increased markedly since the emergence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA). Injection drug use is a risk factor for abscesses and may impact the microbiology and treatment of these infections. In a cohort of patients hospitalized with cutaneous abscesses in the era of CA-MRSA, our objectives were to: 1) compare the microbiology of abscesses between injection drug users and non-injection drug users, and 2) evaluate antibiotic therapy started in the emergency department in relation to microbiological findings and national guideline treatment recommendations. Methods This was a secondary analysis of two published retrospective cohorts of patients requiring hospitalization for an acute bacterial skin infection between January 1, 2007 and May 31, 2012 in 7 academic and community hospitals in Colorado. In the subgroup of patients with a cutaneous abscess, microbiological findings and the antibiotic regimen started in the emergency department were compared among injection drug users and non-injection drug users. Antibiotic regimens involving multiple agents, lack of activity against MRSA, or an agent with broad gram-negative activity were classified as discordant with Infectious Diseases Society of America (IDSA) guideline treatment recommendations. Results Of 323 patients with a cutaneous abscess, 104 (32%) occurred in injection drug users. Among the 235 cases where at least one microorganism was identified by culture, S. aureus was identified less commonly among injection drug users compared with non-injection drug users (55% vs 75%, p = .003), with similar patterns observed for both MRSA (33% vs. 47%, p = .054) and methicillin-susceptible S. aureus (17% vs. 26%, p = .11). In contrast to S. aureus, streptococcal species (53% vs 25%, p <.001) and anaerobic organisms (29% vs 10%, p < .001) were identified more commonly among injection drug users. Of 88 injection drug users and 186 non-injection drug users for whom antibiotics were started in the emergency department, the antibiotic regimen was discordant with IDSA guideline recommendations in 47 (53%) and 101 (54%), respectively (p = 0.89). In cases where MRSA was ultimately identified, the antibiotic regimen started in the emergency department lacked activity against this pathogen in 14% of cases. Conclusions Compared with non-injection drug users, cutaneous abscesses in injection drug users were less likely to involve S. aureus, including MRSA, and more likely to involve streptococci and anaerobes; however, MRSA was common in both groups. Antibiotic regimens started in the emergency department were discordant with national guidelines in over half of cases and often lacked activity against MRSA when this pathogen was present.

Repeat cultures in septic arthritis, do they change antibiotic management?

“…[8] These organisms are responsible for a recent decrease in the proportion of MRSA infections among patients who inject intravenous drugs. [9] Polymicrobial cultures also made up a sizable portion of all infections in the study, at 11.7%. Polymicrobial infections represent a significant challenge for eradication, due to concerns of antibiotic resistance and insufficient treatment.…”

Efficacy and Safety of Omadacycline Versus Linezolid in Acute Bacterial Skin and Skin Structure Infections in Persons Who Inject Drugs

“…Cultures obtained from abscesses in PWID show that, similar to the general population, most infections are likely to be caused by S. aureus , including MRSA [ 15 ]; however, causative pathogens may be more diverse than seen in the general population, and dependent on injection practices [ 15 , 16 ].…”

Compliance to antibiotic guidelines leads to more appropriate use of antibiotics in skin and soft tissue infections in injecting drug users

“…The bacteria causing SSTIs are introduced from the commensal skin and oral flora and from contaminated drugs and injection paraphernalia [3,5,[7][8][9]. In PWID, the dominating etiology is staphylococci and streptococci [2,3,5,[10][11][12][13][14][15]. Some studies, mainly from urban USA, show a high incidence of infections caused by methicillin resistant Staphylococcus aureus (MRSA) [3,7,10,[14][15][16][17][18][19].…”

“…In PWID, the dominating etiology is staphylococci and streptococci [2,3,5,[10][11][12][13][14][15]. Some studies, mainly from urban USA, show a high incidence of infections caused by methicillin resistant Staphylococcus aureus (MRSA) [3,7,10,[14][15][16][17][18][19]. Northern European studies have not reproduced these findings, except in isolated outbreaks [2,13,16,20].…”