By Carol A. Kemper, MD, FACP
Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases,
Santa Clara Valley Medical Center
Prevention strategies are necessary to limit transmission of multidrug-resistant organisms (MDRO) in the hospital, especially in high-risk settings. Identification of carriers of extended-spectrum beta-lactamase (ESBL)-producing organisms via active surveillance, and contact isolation of positives, has been recommended for certain high-risk groups (e.g., those in the intensive care unit [ICU]).
To thwart transmission of MDRO/extensively drug-resistant organisms (XDRO), our facility implemented routine ESBL surveillance in high-risk individuals in 2015, using perirectal swab specimens and the chromogenic agar culture technique. High-risk groups were considered to be admissions from long-term care facilities or an outside facility and patients on hemodialysis.
From 2015 to 2017, the prevalence of ESBL carriage steadily increased, up to 14% in patients admitted from skilled nursing facilities (SNF). This meant that many otherwise asymptomatic older SNF patients, who were simply ESBL carriers, now required contact isolation. However, in those who were critically ill or septic, identification of ESBL carriage provided the advantage of preemptively employing the use of a carbapenem as clinically appropriate. One other important advantage to the active surveillance program was that during the three years of surveillance, only one patient was found to have “hospital-onset” ESBL not previously identified on admission. Thus, the program successfully kept the “transmission rates” of this MDRO remarkably low.
Ironically, as the prevalence of ESBL colonization in our screening population increased, so did the cost of the program. By 2017, the estimated the annual cost of ESBL surveillance was approximately $250,000 (based on laboratory costs and not the cost of isolation supplies). This was in addition to active surveillance of methicillin-resistant Staphylococcus aureus (MRSA; required by California regulation), Clostridioides difficile, and carbapenem-resistant Enterobacteriaceae (CRE) (recommended by the CDC) in select patients and travelers. The burden to the micro lab was just too much. Thus, in 2017, the infection control team made the difficult decision to abandon ESBL screening. Our disappointment was mollified only by the knowledge that approximately half of such patients required isolation for other reasons (MRSA/C. difficile), since double and triple colonization was not uncommon.
The debate about active ESBL surveillance continues. Zahar et al argued that enforcement of universal precautions and improved hand hygiene makes more sense and ultimately is likely to be a more effective strategy than “search-and isolate,” for the following reasons:1
- The cost of routine active surveillance is not insignificant (as mentioned earlier) and poses a considerable burden to the microbiology lab; such surveillance costs are not reimbursable by insurance or Medicare.
- The lag in retrieving results (which may be up to 48-72 hours) means that either individuals being screened must be isolated pending results — or those with ESBL colonization are not isolated initially.
- The frequency of false-negative surveillance samples may be as high as 25%, depending on technique and detectable levels of fecal colonization.
- Surveillance focused only on ESBL does not detect other MDRO, such as carbapenem-resistant pseudomonas or Acinetobacter baumanii — two important hospital pathogens.
- Defining high-risk groups for screening may overlook those without recognized risk factors (e.g., prior SNF stay or prior travel or residence in Asia or a developing country).
- Limited studies suggest negligible transmission from asymptomatic carriers of ESBL-containing organisms in the acute care setting.
- The “human” cost of isolation is not insignificant, from the donning and doffing of gowns and gloves, to the occasional distress of patients being screened with rectal swabs, and then the challenging explanation of why “Granny is in isolation.” We have had some families so overreact that they have prevented contact with the grandchildren.
- The authors argued that rather than being a useful clinical result, the detection of ESBL in perirectal swabs may contribute to the overuse of carbapenems.
- The authors argued that ESBL transmission in the critical care setting occurs “rarely” when hand hygiene compliance is maximized. With improved hand hygiene compliance, the authors of one study found little added value to the implementation of contact isolation on acquisition rates of Enterobacteriaceae in the ICU. Further, the use of single rooms and daily chlorhexidine body bathing also may reduce the risk of acquisition of potential pathogens.
The balance in favor of active surveillance for MDRO could shift if more rapid and reliable (and cheaper, less labor-intensive) diagnostic tests were available. But, I wondered, if the risk of transmission of ESBL and other MDRO from asymptomatic individuals with stool carriage is ostensibly so low, as these authors argued, why is such a remarkable increase in ESBL colonization being observed in our local SNF population?
- Zahar JR, Blot S, Nordmann P, et al. Screening for intestinal carriage of extended-spectrum beta-lactamase-producing Enterobacteriaceae in critically ill patients: Expected benefits and evidence-based controversies. Clin Infect Dis 2019;68:2125-2130.