ID Week 2012

October 17-21, 2012; San Diego, CA
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Increased Risk of Clostridium difficile Observed in Patients Using Concomitant Antibiotics and Probiotics

New evidence shows that the rate of community-acquired Clostridium difficile (C. difficile) is increasing, becoming an issue not just in long-term care settings but also in primary care and outpatient clinics. Thus, clinicians and staff caring for older adults across all healthcare settings should continue strengthening infection control and practice judicious prescribing of probiotics. According to current practice guidelines from the Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA), administration of currently available probiotics is not advised to prevent C. difficile infection due to limited data and the risk of bloodstream infection. An expert panel of the SHEA and the IDSA believes that larger trials are required before this prescribing practice can be recommended. Until then, many clinical sites are conducting their own small studies to evaluate the efficacy of these drugs in C. difficile prevention. In a poster session at ID Week 2012, Justine Dickson, PharmD, and colleagues, Yale-New Haven Hospital, Saint Raphael Campus, New Haven, CT, presented the results of their retrospective cohort study examining the clinical impact of probiotics in C. difficile infection prophylaxis in patients receiving high-risk antibiotics. 

Over a 6-month period in 2010, the study followed 389 adult patients who were hospitalized and received high-risk antibiotics (ie, clindamycin, ceftriaxone, ciprofloxacin, and levofloxacin) for 5 or more days. The formulary probiotics identified in the study were Lactobacillus G.G. and Saccharomyces boulardii. Patients were divided into two groups: those taking probiotics plus antibiotic therapy (n=143; mean age, 80.4 years), and those taking antibiotics alone (n=246; mean age, 73.3 years). For both groups, 5.1% of patients developed C. difficile infection within 90 days of taking an antibiotic. The average duration of high-risk antibiotic use was 7.3 days in the probiotic group and 7.7 days in the antibiotic-alone group. Patients receiving probiotics had an 8.4% incidence of developing C. difficile infection compared with 3.3% of those who only received antibiotics. Additionally, a C. difficile infection occurred in 12.2% of patients who were concomitantly prescribed a proton pump inhibitor (PPI) and a probiotic, compared with 3.3% in those taking probiotics and no PPI. The authors noted that this correlation suggests a potential adverse interaction between these two drug classes. 

Dickson and colleagues concluded that the risk of developing C. difficile infection in those who used probiotics was 2.7 times higher than in nonusers (P<.005). The team also noted that of all the high-risk antibiotics evaluated, levofloxacin was the one most commonly used by patients who developed C. difficile infection (65%). “Patients receiving high-risk antibiotics and a probiotic had a higher incidence of C. difficile infection than those who did not receive a probiotic,” the team concluded. But Whitney Hung, PharmD, co-investigator, also acknowledged the study’s limitations and said, “Ideally, we would like to conduct a randomized study that will allow us to provide a more definitive conclusion of the relationship between antibiotics and concomitant probiotics.”—Allison Musante
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Prevalence of Community-Acquired MRSA Rising in Younger, Healthier Nursing Home Residents

New research suggests that community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA), particularly the USA300 strain, is becoming increasingly prevalent in hospitalized patients, but the extent to which CA-MRSA penetrates long-term care (LTC) settings is not well understood. There is clinical concern that if a majority of patients in nursing homes are admitted from hospitals, the potential exists for heightened transmissibility of the infection and a more severe impact on nursing homes residents, who tend to be frail and chronically ill. However, according to Courtney Murphy, PhD, University of California Irvine, and colleagues, identifying characteristics associated with higher CA-MRSA prevalence in LTC facilities may enable healthcare providers to prevent or control the spread of infection with more targeted interventions. The team presented the results of their study in a poster session at ID Week 2012. 

Between October 2008 and May 2011, the research team collected more than 3000 nasal swabs from LTC patients across 22 facilities in California, 24% of whom (n=824) were found to have MRSA. Among these MRSA-positive swabs, one-quarter of them were community-
acquired strains, 22% of which were identified upon patient admission and 26% were identified at point of care. CA-MRSA was present in 20 of 22 facilities, and 16 of them were characterized as having high CA-MRSA prevalence (defined as CA-MRSA accounting for ≥22% of all MRSA-positive patients). Bivariate and multivariate models used these data as well as nursing home descriptive information taken from the Minimum Data Set and patient records to predict characteristics associated with high versus low percentage of CA-MRSA among all MRSA isolates.

Facilities with a high prevalence of CA-MRSA tended to have younger, possibly healthier residents. In the high-prevalence arm, 36% of residents were younger than 65 years compared with 4% of the low-prevalence arm. The presence of comorbidities (ie, diabetes, indwelling devices, and fecal incontinence) was also much lower in the high-prevalence group. The authors wrote that this finding “may reflect residents’ prior time in the community or acquisition in hospitals that have increasing CA-MRSA.” A longer length of stay was associated with higher prevalence of CA-MRSA, however, the size of the facility did not appear to be significant. Facilities with a higher percentage of Hispanic residents were associated with CA-MRSA carriage (1.2 odds ratio; P=.006). Murphy and colleagues concluded that “nursing homes may contribute to regional CA-MRSA spread” and that “more studies are needed to fully determine if CA-MRSA strains spread more rapidly and are more virulent in nursing home settings.”—Allison Musante
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Study Examines Adnerence to IDSA Clinical Practice Guidelines in Management of Cutaneous Abscesses

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is one of the most common causes of skin and soft-tissue infections, accounting for a large portion of ambulatory care visits in older adults and a significant concern in long-term care settings. In the treatment of uncomplicated cutaneous abscesses or boils, clinical practice guidelines from the Infectious Diseases Society of America (IDSA) advise that incision and drainage alone is the standard of care and antibiotic therapy is often not necessary, as it has not been demonstrated to shorten the clinical course of cutaneous abscesses. In a poster session presented at ID Week 2012, Larissa May, MD, and colleagues, George Washington University and Johns Hopkins University, presented the findings of a study examining adherence to IDSA clinical guidelines in the emergency department (ED) after electronic dissemination of the guidelines to ED physicians. 

Per the guidelines, antibiotics should be considered in immunocompromised patients, patients older than 60 years, if there is more than one abscess and if any are located on the face or perineum, patients who are febrile, patients with comorbidities, and if the erythema diameter is larger than 5 cm. The guidelines also advise that any patient with a cutaneous abscess who requires antibiotic therapy should receive empiric treatment for MRSA. Appropriate anti-MRSA antibiotic regimens include clindamycin, doxycycline/minocycle, linezolid, and cotrimoxazole. For optimal patient outcomes, adherence to these guidelines is recommended; however, May and colleagues reported that nonadherence to these guidelines is common when clinicians aim to reduce unnecessary prescribing of antibiotics. 

The study involved 126 patients from two academic EDs (mean age, 37 years) receiving incision and drainage for a cutaneous abscess. These patients had no history of prior treatment for the same abscess. Patients were randomized to a rapid molecular diagnostic test result versus the standard of care. Clinical and demographic characteristics were collected from patient data forms and charts. Of the enrolled patients, 74% received antibiotics and 47% of providers did not adhere to the IDSA guidelines. Ten patients (22%) did not receive antibiotics when indicated. When guidelines were not followed, 51% of the cases were attributable to unnecessary use of antibiotics. In the 74 patients with MRSA (documented or unknown) and an indication to receive an antibiotic, 14% received cephalosporin alone or in combination in contradiction to the IDSA guidelines. “Cephalosporins are not active against this pathogen,” May said in an interview with Annals of Long-Term Care. “Combination therapy is unnecessary according to the IDSA guidelines and exposes (or overexposes) patients to antibiotics unnecessarily.”

The researchers found that ED physicians are more likely to adhere to IDSA guidelines for patients with comorbidities and cellulitis. Patients with erythema smaller than 2 cm were unlikely to receive an antibiotic prescription when indicated, suggesting that clinicians may “downplay” the need for antibiotics if cellulitis is not present, the authors wrote. Guideline adherence was not significantly associated with age, sex, race, prior hospitalization, history of abscess, or insurance type. “More than 25% of antibiotic prescribing is unnecessary and not consistent with guidelines in patients with cutaneous abscesses,” May said. “This is important because it suggests a tremendous opportunity for antimicrobial stewardship.”—Allison Musante