Carbapenem-resistant bacterial infections associated with prior hospitalizations and comorbid conditions

1. This study found that over 90% of carbapenem-resistant Enterobacteriaceae (CRE) cases were reported in patients with prior health care exposures and comorbid conditions.

2. In this study, a low incidence of CRE was noted in the 7 states that were evaluated. This may indicate that recent interventions could be having a significant effect.

Evidence Rating Level: 3 (Good)

Study Rundown: Enterobacteriaceae are a family of Gram-negative bacteria including Escherichia coli and Klebsiella pneumoniae. Infections with these bacteria have been successfully treated with a class of beta-lactam antibiotics known as carbapenems for decades. In 2001, significant resistance to these drugs via the bacterial enzyme carbapenemase was first described. Since then reports of drug resistance have been on the rise. In order to gauge the breadth of carbapenem resistance in this country, the authors of this study conducted carbapenem-resistant Enterobacteriaceae (CRE) surveillance via the CDC Emerging Infections Program (EIP) Multi-site Gram-negative Surveillance Initiative.

While CRE was reported in all seven states evaluated, the overall crude incidence rate was relatively low at 2.93 per 100,000, particularly as compared to the incidence rate of 25 per 100,000 for MRSA. Most CRE cases were patients with comorbid conditions or prior hospitalizations. While this is the most comprehensive study on CRE in the United States, many of the clinical and public health laboratories involved were unable to determine mechanism of CRE resistance, leading to incomplete results. This study has certainly advanced the development of a more focused understanding of drug resistance in this country. Future work should expand such surveillance efforts to other states and aim to improve laboratory capabilities of molecular analysis.

Click to read the study in JAMA

Click to read the accompanying editorial in JAMA

Relevant Reading: Vital signs: carbapenem-resistant enterobacteriaceae

In-Depth [survey]: The overall crude annual CRE incidence during the 2-year period was 2.93 (95%CI 2.65-3.23) per 100,000 cases. Oregon reported the highest incidence of 4.58-4.80 per 100,000. Prior health care exposures were reported for 531/575 cases (92.3%; 95%CI 90.2% to 94.5%). A total of 415/454 individuals (91.4%; 95%CI 88.8% to 94.0%) had at least 1 underlying comorbid condition. The most common comorbid conditions were diabetes (201 or 44.3%; 95%CI 39.7% to 48.9%) and neurological disorders (185 or 40.7%; 95%CI 36.2% to 45.3%). Of the 185 patients with neurological disorders, 107 (57.8%; 95%CI 50.7% to 65.0%) had an indwelling urinary catheter within 2 days prior to their initial culture. Of the 188 CRE isolates that underwent carbapenemase testing, K. pneumoniae carbapenemase was the only one identified (90 or 47.9%; 95%CI 40.6% to 55.1%).

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