This is the first study from Lebanon defining the prevalence and risk factors for ESBL-PE colonization in nursing staff in relation to different hospital infection control measures with ESBL-colonized and ESBL-infected patients.
Hospital 1, where contact isolation was still being performed, had the lowest prevalence rate of colonization in nursing staff. We believe that it was likely due to a favorable effect of CP. Surprisingly, Hospital 2, where CP was removed within the month preceding sample collection, had the highest prevalence of ESBL-PE colonization. Having found no explanation for this phenomenon in the literature, we propose a few possible reasons leading to this highest prevalence.
First, we theorize that this might likely be explainable by a ‘flooding' effect, whereby the gastrointestinal tracts of nursing staff were rather quickly populated by resistant organisms ‘new' to their systems after lifting CP. Second, it is possible that nursing staff may have felt more ‘secure' that isolation was no more required, and consequently less compliant with strict adherence to standard precautions, hence driving the rates of colonization to a high level. A
third possible explanation is that environmental contamination may play a significant role (e.g. phones, cart…)49-51, where ESBL-PE can survive on surfaces for many months if disinfection is not well performed10,52, leading to concerns about direct causality. Consequently, evaluating the environmental contamination and monitoring the cleaning process are critical53. Hence, upon discontinuation of CP for ESBL-PE colonized/infected patients in any healthcare organization, it is recommended to provide enhanced and ongoing education to staff about the need for compliance with standard precautions and monitoring of compliance48. This education should emphasize the critical need for compliance with hand hygiene, environmental cleaning and decontamination, ongoing surveillance, all in order to mitigate the potential for increased transmission. Furthermore, molecular typing of ESBL-PE from HCW may have a role in case of an outbreak, to investigate the source of acquisition, whether from the hospital or the community, knowing that there may be differences within the community vs. hospital-acquired strains, whereby the community strains are less resistant48. However, this was not performed in our study due to lack of resources and since it was not part of the original study design.
A study conducted by Bassyouni et al. in Egypt in 2013, published in 2015, demonstrated that the rate of fecal carriage of ESBL-PE in HCW practicing standard precautions was 21%41, which is roughly comparable to what we found despite the smaller number of samples in our study.
In the current study, the highest rates of ESBL-PE colonization were in nurses with 2-4 years of clinical experience, especially compared to those who have worked much longer. Our interpretation of this observation is that less experienced nurses get colonized upon entering
the hospital environment, which is consistent with the ‘flooding' effect described above, especially in settings were contact isolation is not performed. Similarly, the ESBL-PE prevalence data for nurses in hospitals that do not require CP in our study are comparable to the rates of colonized patients found in a retrospective study of 16 different Lebanese hospitals between January 2011 and December 2013, published in 2016 by the Lebanese Society of Infectious Diseases and Clinical Microbiology54, where ESBL-PE rate of E. coli isolates was 32.3% and that of Klebsiella was 29.2%.
On the other hand, we find a similarity between the prevalence data of the hospital still requiring CP to that of a Lebanese nursing home data55, which is lower than the hospital resistance data described above54. This is likely due to the nursing home prevalence being more reflective of community prevalence data as opposed to acute care hospital data. Hence, once again, we question the role of the hospital environmental contamination by hospital-acquired strains in regards to direct causality of the higher ESBL-PE rates upon discontinuation of CP. Accordingly, we suggest that hospital environmental sampling be examined as a possible additional reservoir in support of our theory regarding the efficacy of ongoing CP for ESBL-PE.
Hence, it is certainly not surprising to unveil a high rate of colonization of ESBL producers in the Lebanese community, of which nurses are an integral part. This is where the dissection of the sources of ESBL, whether community- or nosocomially-acquired, becomes a question that can be answered neither microbiologically nor epidemiologically, at this point and with the current resources in the country.
Notwithstanding complexity and variability of data collection and methodologies used to assess resistance in the different studies, a study by Challita et al. completed during the second half of 2015 showed an ESBL E. coli prevalence of 7.7% in a Lebanese nursing home55. This is lower than hospital resistance data in the country, as detailed above. We are not able to justify this lower than average prevalence data point, especially in an elderly institutionalized cohort of patients. However, we do find a reflection of this prevalence in our nursing staff cohort of hospital 1, where CP continues to be practiced. Hence, we question whether the effect of health-care acquisition is mitigated by strict adherence to CP, ultimately resulting in a lower prevalence of ESBL Gram-negative colonization amongst nurses. Only 8.9% were ESBL positive carriers in Hospital 1, and this was in agreement with the prevalence of ESBL E. coli in the Challita study (7.7%)55.
A study conducted by Hilty M et al. demonstrated that the contact isolation effect might be distinguishable between the clones of ESBL-PE22. One hypothesis explaining this observation is that there may be differences within community vs. hospital-acquired strains, such that the community strains are less resistant and may hence be more easily cleared by the gastrointestinal tract48. Based on our observation that showed a high colonization rate especially in the hospital where CP was recently removed and knowing the existence of the different strains, we do believe that CP imparts at least a partially protective effect on transmission of specific nosocomial strains of ESBL-PE to healthy nursing staff without being able to prove it in this study. To reduce the burden of this colonization, one promising approach
is fecal microbiota transplantation that may lead to ‘decolonization' of ESBL-PE from the GI tract of carriers. However, this theory needs further research.
Additionally, since ESBL-carrying organisms are spreading their resistance genes via plasmids, discovery of the "pCURE", targeting plasmids might be another promising approach for de- colonization without harming the normal flora in the colonized individual56. This would be particularly valuable in HCWs who may potentially spread it to their patients. However, further investigations are required concerning these innovations.
This study has several limitations. In the first place, the level of nursing staff participation was somewhat low (269 volunteered from a potential pool of 733 nurses) and participation was not congruous between the three hospitals. Our sample contained many more nurses from Hospital 1 (52.4% of our sample) compared to Hospital 2 (18.2%) and Hospital 3 (29.4%). We theorize that this higher rate of participation of Hospital 1 nursing staff is mainly fueled by an inherent interest to confirm that their laborious practices of donning gowns and gloves for each ESBL-PE patient encounter are indeed leading to a transmission protective effect both for them and for patients. Additionally, another unstated reason could be the ultimate possibility of discontinuing this practice if it were found to be ineffective. Finally, the overall low rate of participation could be due to needing to provide stool samples, which many people find uncomfortable. Despite the potential limitation of lower participation rates and unequal sample sizes, we were adequately powered, and our group differences were significant, revealing the
importance of CP as a protective way for curtaining transmission of ESBL-PE from patients to nursing staff.
Moreover, with our strict exclusion criteria, 33.1% of volunteers were excluded due to the recent intake of antibiotic within the preceding 4 months. The most commonly utilized antibiotics were amoxicillin-clavulanic acid (39%), multiple antibiotics (14.6%), cephalosporins (10%) and fluoroquinolones (10%). In a country like Lebanon, where medications such as antibiotics are purchased without a prescription, such a high rate of antibiotic use may not be surprising although it is very disturbing, particularly in a relatively younger population and healthcare professionals. We suggest that the overly high use of amoxicillin-clavulanic acid is likely based on its low price, availability, and familiarity with its use57.
Another limitation of the current study was our inability to relate the prevalence of ESBL-PE in nurses with the clinical setting where most of the nurse’s time was spent. Our initial intent was to attempt establishing some link with high-risk settings such as the emergency department and the Intensive Care Unit (higher risk of unprotected contact, exposure to wounds, trauma, etc.). However, the rates of response from the different settings were insufficient to permit examination of site-specific data.
Lastly, due to the lack of funding, we could not utilize PCR technology to analyze specific ESBL gene types in each hospital58. Such a tool would be highly recommended in studies like ours, in
order to determine the clonality of ESBL genes, which may explain certain epidemiologic trends (nosocomial vs. community strains, site-specificity, environmental acquisition, etc.).
Despite those limitations, we do believe this study provides an important confirmatory observation regarding the protective impact that CP have against transmission of ESBL-PE strains to nursing staff.