Although MDR-Ab is emerging more frequently in Chinese hospitals, [28, 29] localized nosocomial outbreaks are rarely reported in China. The present study described a nosocomial bronchofiberscope-associated outbreak of A. baumannii. The significant association between bronchofiberscope use and MDR-AB incidence in this case–control study (Table 2) and the temporal association between bronchofiberscope use and MDR-Ab culture positivity (Figure 2) supported the conclusion. We also found MDR-Ab bronchofiberscope contamination and identified several potential administrative and technical problems with the in-ICU bronchofiberscope reprocessing practice. Nevertheless, univariate analysis revealed other significant risk factors, and the outbreak strain was not isolated from the bronchoscope only. Thus, the bronchofiberscope is among several rather than the only important factor that contributed to the outbreak.
In this study, genotype A MDR-Ab was defined as the outbreak strain. During the epidemic period, seven of 12 patients were infected or colonized with the outbreak strain, which was also isolated from multiple environmental surfaces within the ICU. Only one patient acquired the outbreak strain without direct bronchofiberscope exposure. Two patients were infected or colonized with MDR-Ab after intervention on 21st October, one of whom had undergone bronchofiberscopy; however, these 2 MDR-Ab isolates were not identified as the outbreak strain, so the intervention definitely controlled the outbreak.
A similar large outbreak due to clonal MDR-Ab transmission has been reported, and widespread environmental contamination was perhaps promoted by the aerosolization of organisms during the pulsatile lavage debridement of infected wounds . Our finding of an association between bronchofiberscopy and the MDR-Ab outbreak also highlights the importance of appropriate infection control measures when invasive medical procedures are performed. Since the environmental sample collection started before the infection control intervention measures were implemented, the cultures taken from the environment yielded high MDR-Ab rates. Eighty-five percent of the MDR-Ab isolates from the environmental samples were identical to the outbreak strain, indicating serious contamination of the surrounding environmental surfaces .
Importantly, four isolates collected directly from the non-disinfected and disinfected bronchofiberscope were also identified as being the outbreak strain, suggesting that serious failure of the bronchofiberscope reprocessing procedure and that the outbreak strain of MDR-Ab might have been transmitted through direct contact with the bronchofiberscope. Alternatively, these organisms could have been introduced into the environment by the index case or possibly by an unidentified patient and then transmitted through healthcare workers’ hands during other medical procedures; however, we did not identify the index case who “imported” the outbreak strain into the ICU, and no similar case was reported in other wards of the hospital.
In our investigation, most of the environmental MDR-Ab were isolated from the healthcare-associated environmental surfaces including the bed sheets, bedrails, dispensing table, nurses’ desk, and outer surface of the invigilator. There were no positive cultures collected from the healthcare workers’ hands or nasal cavities (data not shown), a finding that might be associated with high hand hygiene compliance rates during the investigation since all of the healthcare workers were concerned about the probable correlation between personnel contact and this MDR-Ab outbreak.
In addition to bronchofiberscopy treatment, univariate analysis of the case–control study showed that septic shock and renal disease were more common in the cases than in the controls. Similar results were also found that the underlying patient illness severity was a significant factor contributing to the acquisition of carbapenem-resistant A. baumannii in the ICU . Moreover, length of ICU stay and the receipt of carbapenem were also risk factors [31, 32]. Attempts were made to identify independent risk factors using multivariate logistic regression; however, the sample sizes were too small to allow for the drawing of reliable conclusions .
Bronchofiberscopy is used frequently within ICUs. Our findings emphasize that bronchofiberscopy must be performed with appropriate infection control measures. The present outbreak was not associated with bronchofiberscope defects or damage [20–22] but apparently was associated with its related cleaning and disinfection procedures. Therefore, strict bronchofiberscope reprocessing should be performed after each procedure and at the end of the day according to the published guidelines. It might be wise to increase the number of bronchofiberscopes available in each ICU to guarantee professional bronchofiberscope reprocessing within the hospital’s cleaning and disinfection department; however, this is usually limited for economic reasons, especially in less developed districts or countries. Therefore, assigning and training specific personnel to reprocess bronchofiberscopes in the ICU according to strict guidelines might also be a plausible solution. On the other hand, standard precautions must be implemented during bronchofiberscopy procedures, such as the use of personal protective equipment including fluid-resistant gowns, gloves, surgical masks, eye protection, and shoe and hair covers . In addition, patients who receive bronchofiberscopy should be draped during treatment, and any potentially contaminated environmental surfaces should be thoroughly cleaned and disinfected after the procedure.
This outbreak was clinically significant due to the extensive antibiotic resistance of A. baumannii and the severity of the patient outcomes. Five of six cases who underwent bronchofiberscopy treatment developed MDR-Ab BSIs with severe clinical manifestations . Half of the MDR-Ab carriers died in the ICU during the epidemic period, and MDR-Ab infection possibly contributed to four deaths. However, the significance of this case–control study is limited by its small sample size and wide 95% CIs.
The results of this case–control study demonstrated an association among factors but could not make a conclusion about causality. Further studies of similar outbreaks are needed to confirm these results. However, a strong association between bronchofiberscopy and MDR-Ab acquisition was confirmed by the epidemiologic and microbiologic analyses conducted during the outbreak.