After the identification of a high MDR-GNB carriage in a specific NICU during the first two years of surveillance, an episodic implementation of control strategy had been organized through an extraordinary collection of rectal swabs, reinforcement of good clinical practice and an informational meeting involving all healthcare workers. These measures determined a short-term decrease of MDR-GNB carriage prevalence from 68.5% in 2015 to 43.3% in 2016. But after few months, prevalence of MDR-GNB carriage raised again up to 70% in 2017 (Table 1). High prevalence of MDR-GNB carriage was reported from Ecuador (56%), Philippines (61%) and Hungary (> 50%) (25,26). Nevertheless, differences in local epidemiology, logistics and hospital organization must be considered. In our setting, the contextual rapid increase of carriage of ESBL-KP, that accounted for most MDR-GNB identified, suggested the need for a more structured and permanent intervention to achieve a long-lasting containment of carriage. This intervention strategy included a strengthening of sample collection with extraordinary clinical samples and environmental samples, frequent stakeholders’ meetings and improvement of prevention measures regarding the correct use of antibiotic therapy, sensitization to hand-washing, implementation of checklists for common procedures and invasive procedure management.
The impact of this multiple and coordinated intervention strategy for the reduction of MDR-GNB carriage has been statistically significant and sustained (especially related to ESBL-KP) even in the second year after intervention, with a further reduction of ESBL-KP prevalence despite a modest increase of MDR-GNB carriage (Fig. 3).
The two months strengthened surveillance of patients together with microbiological analysis of surfaces and healthcare workers’ hands was useful for strictly monitoring colonization trend, tracing transmission roots and enhancing the adherence to preventive measures, first of all hand hygiene in the five key moments suggested by WHO (27–29). During this period, MDR-GNB were detected not only from rectal swab, but also from nasal and oral mucosa. In addition, feeding bottles, soothers and milk samples were analysed because, when contaminated after feeding, they represent a further source of MDR-GNB environmental spreading. The role of cross-transmission of MDR-GNB was confirmed by the presence of identical or closely-related ESBL-KP strains in rectal, oral, nasal swabs, milk and environmental samples (Fig. 2). The evidence of MDR-GNB spreading by saliva and milk increased the awareness of doctors and nurses and the adherence to hand hygiene before and after milk administration and to the immediate substitution of contaminated devices after feeding (30). In our experience, the finding of environmental contamination by intestinal bacteria highlighted the role of healthcare workers in the prevention of such spreading and prompted the implementation of a detailed procedure for diaper change and a better compliance to correct actions. Environmental contamination by ESBL-KP in NICU has been reported by Szél and colleagues, and has been associated to high prevalence of MDR-GNB carriage and infection. Successful elimination of ESBL-producing nosocomial bacteria was obtained thanks to the implementation of a multidisciplinary intervention based on reduction of invasive procedures, changes of the antibiotic policies, microbiological screening at short intervals, progressive feeding, safer bathing protocol, staff hand hygiene training and continuous monitoring of the number of newly infected and newly colonized patients (25). This interdisciplinary approach is aligned with ours for the most of the measures taken and our results are comparable. In 2018 in Montpellier, a hospital surveillance program revealed an outbreak of ESBL-KP infection/colonization related to incubators as probable pathogen reservoir: ESBL-producing strains from 19 patients displayed the same molecular profile between them and a strain isolated from an incubator after cleaning. In accordance with our data, the introduction of new preventive hygiene measures stopped the outbreak pinpointing the fundamental role of environmental colonization management (31).
The role of MDR-GNB intestinal colonization as a risk factor for infection has been reported in several studies (30,32,33). Colonization by ESBL-producing GNB was a risk factor for developing ESBL infections in paediatric cardiac surgery patients (34). Cross-transmission of colonization, however, is above all a sign of poor adherence to infection prevention measures and, therefore, the prevalence of colonization could be used as an indicator of health workers' compliance with standard and contact precautions in patient care. Furthermore, colonization certainly represents a potential source of dissemination of microorganisms from colonized patients to other NICUs or other paediatric and community health facilities (35). Recent studies have shown the persistence of MDR-GNB colonization even up to 2–5 years after NICU discharging, emphasizing the impact of the problem (36).
The present study aims to analyse the impact of the coordinated strategy of measures on the intestinal carriage of MDR-GNB, while a direct effect on MDR-GNB-related infections has not been evaluated. Our analysis considers the role of the whole set of control measures performed at the same time but we are not able to identify the single contribution of each group of actions (strengthening of sample collection, improvement of prevention measure or stakeholders weekly meeting) on the reduction of MDR-GNB and ESBL-KP carriage. Different studies analysed the impact of single measures on microbial colonization or infection. The correct management of central venous accesses proved to be effective against related infections (37). Antimicrobial stewardship for the correct use of antibiotics in term of doses, duration of therapy and administration route is a key point for prevention and control of drug-resistance(38–40). Use of appropriate audits and measures to promote adherence to infection prevention and control procedures, decision-making and feedback outcomes to stakeholders has been included among essential infection prevention strategies in the paediatric population (41). Intensification of microbiological surveillance has been used as a strategy to contain ESBL-KP outbreaks (31).
The quasi-experimental analysis was carried out in order to evaluate the eventual interference of different clinical characteristics of patients in determining the reduction of MDR-GNB carriage after introduction of coordinated intervention measures. Defined selection criteria have been used for both intervention and control populations in order to minimize selection bias. Possible confounders related to different structural organizational and seasonal settings were ruled out by choosing as controls a group of patients admitted in the same hospital ward in the same season of the preceding year and cared by the same healthcare personnel. Prevalence of MDR-GNB and ESBL-KP carriage significantly reduced in the intervention population compared to controls (12% vs 42.3% and 2% vs 42.3%, respectively). The two populations have been compared in accordance to clinical features, use of medical devices (invasive and non-invasive) and type of treatment: differences for specific variables were observed and statistically investigated (Table 2). Gestational age, birth weight, being inborn, feeding, antibiotics and length of stay in NICU resulted associated to MDR-GNB carriage at univariate analysis and were included in the multivariate model in order to analyse their possible contribution to the global risk of colonization. The risk of colonization by MDR-GNB in patients admitted during the intervention period was significantly lower than that observed in patients admitted during the control period and multivariate analysis confirmed the main significative role of introduction of coordinated intervention measures in reducing bacterial circulation (OR adjusted = 0.15, p = 0.01), regardless of patient characteristics and procedures (Table 3).
Being inborn seemed to increase the risk of colonization (OR = 1.90) even if this association was not significant (0.55). Cassettari et al. observed a possible protective role of breastfeeding against ESBL-KP colonization in newborns (42), but our data did not support this evidence (OR = 2.34, p = 0.34), so the role of this factor needs to be further elucidated. Previous studies reported the role of low gestational age and birth weight, mechanical ventilation, parenteral nutrition, invasive devices and use of antibiotics as risk factors associated to MDR-GNB carriage (26,35,43,44). In our experience these associations were confirmed but not significant, probably because of the small number of patients examined: the risk of colonization increased with lower gestational age and with the use of nasogastric tube (OR = 0.73, p = 0.09 and OR = 2.68, p = 0.22 respectively). Moreover, lower birth weight was not associated to the outcome probably because the mean weight in our population was high. First-line empiric treatment was significantly different between the two groups. In particular, ampicillin-sulbactam was replaced by ampicillin in the intervention period, as suggested by international guidelines (45). Univariate analysis showed a significant association between the use of cephalosporins and the risk of MDR-GNB carriage (OR = 1.54, p = 0.02), however, this association was not confirmed by multivariate analysis (p = 0.68).
Our study has some limitations. The complexity of the preventive intervention did not allow evaluating the specific contribution of each measure implemented towards the reduction of the prevalence of MDR-GNB carriage. Some patients were excluded from the analysis because of the lack of clinical records; we cannot know if some other risk factors would result significantly associated with MDR-GNB carriage including such patients. Moreover, we did not perform any screening on the mothers, so we could not rule out this possible source of colonization, as previously demonstrated (46). Finally, in our five-year active surveillance program (2014–2019), collection of rectal swabs was scheduled only every four weeks due to organizational needs, including all the newborns present in the NICU at the time of sample collection. Because of this schedule, newborns hospitalized in the period between monthly samplings were not tested.
On the other hand, network-based approach is essential for the management of the diffusion of multi-resistant pathogens, as patients move between one hospital and another and their microorganisms move together with them. This is particularly important for neonatal patients in an interconnected area, where they are frequently transferred from one NICU to another to undergo specialized procedures (17,38). This approach also allows for harmonization of procedures with the aim of optimizing assistance to the newborns (38). With these goals, several neonatal networks have emerged in the world for the surveillance of care-related infections. The presence of an established surveillance program and working group allows the identification of epidemiological changes in colonization trend and the implementation of related control measures.