Discussion

Current guidelines call for contact precautions when providing care for patients known to be colonized or infected by CRAB, but active screening of patients for CRAB is recommended only in special circumstances (eg, outbreaks). ² The immediate vicinity of nearly all CRAB carriers was contaminated by CRAB and CRAB load in the environment was similar between clinical and nonclinical carriers. These findings suggest that CRAB screening to detect carriers might have a role in curtailing environmental contamination and preventing transmission.

Carriers and infected patients shed pathogens into their environment. Dissemination into the surroundings may differ between patients and between pathogens. We previously showed that carbapenem-resistant Enterobacterales (CRE) dissemination to the environment follows the 20:80 rule: 20% of carriers act as superspreaders and are responsible for 80% of shedding. ^{Reference Lerner, Adler, Abu-Hanna, Cohen Percia, Kazma Matalon and Carmeli5} In contrast, in the current study, the CRAB loads in the environment were similar in the surroundings of >80% of carriers. One possible explanation may be the different anatomic site of colonization between CRE and CRAB. In a study looking only at CRAB, Rosa et al ^{Reference Rosa, Depascale, Cleary, Fajardo-Aquino, Kett and Munoz-Price6} showed that environmental contamination differed by colonization site.

We did not detect a significant difference in the environmental load between clinical and nonclinical carriers. In one study, 48% of rooms of multidrug-resistant A. baumannii (MDR-AB) carriers were contaminated, even among patients in whom MDR-AB was detected >2 months earlier. ^{Reference Thom, Johnson, Lee and Harris7} High environmental contamination has also been observed in carriers of gram-positive, drug-resistant organisms (ie, VRE and MRSA). ^{Reference Knelson, Williams and Gergen8}

The WHO determined that there is insufficient evidence to recommend routine CRAB screening because the value of screening and the optimal screening method are uncertain. ² Regarding the optimal screening method, a growing body of evidence indicates that culturing the skin using a premoistened sponge with overnight enrichment is the best method to detect CRAB carriage. ^{Reference Nutman, Lerner, Schwartz and Carmeli4,Reference Doi, Onuoha and Adams-Haduch9,Reference Nutman, Temkin, Lellouche, Ben David, Schwartz and Carmeli10} Regarding the benefit of screening, identifying and isolating CRAB carriers and intensifying terminal cleaning of their surroundings should reduce transmission. However, more studies are needed to determine whether the “search and isolate” strategy in endemic settings could prevent in-hospital transmission and to outline screening criteria (ie, who and when to screen).

A strength of this study is that we reported CRAB load semiquantitatively, not just as present or absent. A limitation is that we did not perform molecular studies to test similarity between patient and environmental isolates (ie, environmental contamination could be unrelated to the current patient).

In summary, the environment surrounding CRAB carriers, including those identified solely by surveillance cultures, is contaminated with CRAB. Screening to detect and isolate nonclinical CRAB carriers may be important to prevent CRAB transmission. Studies that evaluate whether implementation of CRAB screening in endemic settings reduces CRAB incidence are needed.