Infection Control & Hospital Epidemiology
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Fig. 2. Phylogenies of CR-KP (A) and MDR-PA (B) genomes obtained from patient isolates. Genetic distance is based upon the number of SNP differences relative to the reference genome. Note. * = reference genome; sc = scope isolate. The scale indicates the number of nucleotide substitutions per site.
the future. However, the optimal frequency of culturing and the sensitivity of surveillance endoscope culturing for detection of contamination are unknown. Moreover, these measures are not sufficient to detect device-associated outbreaks in a timely fashion. The bronchoscope model implicated in this case is commonly
used in many hospitals, and the outbreak we describe involved one of many Olympus BF-160 bronchoscopes in our hospital. Borescopy revealed a luminal defect and, despite compliance with manufacturer’s recommended reprocessing procedures, accumu- lation of proteinaceous debris in bronchoscope B1 that may have contributed to the establishment of a biofilm and subsequent contamination with MDR-PA and CR-KP. Several other pub- lished reports implicate defective bronchoscopes as the cause of polymicrobial contamination that was linked to outbreaks and pseudo-outbreaks.17–19 Our report, along with others linking bacterial contamination to defective equipment,17,18,20 gives cre- dence to the notion that routine maintenance of bronchoscopes should include visual luminal inspection. Close scrutiny by the FDA of newly marketed medical devices is also necessary to identify engineering vulnerabilities that may engender persistent microbial contamination. The outbreak and pseudo-outbreak we report largely came
to the attention of practitioners because it involved MDROs. Hospital infection prevention departments should consider dedicated surveillance of all endoscopes. Samples that yield microbial isolates should trigger scope usage investigation cou- pled with isolate retrospective review in patients who had undergone procedures with the contaminated scope to mitigate duration of endoscope-associated outbreaks. In addition, the epidemiology of endoscopically obtained specimens should be reviewed to detect outbreaks or pseudo-outbreaks involving sus- ceptible and frequently encountered organisms that could plau- sibly go undetected for long periods or even completely escape the attention of robust infection control programs. Notably, the increase in newly detected MDR-PA, based on
the phenotypic definition specific to this outbreak, went unrecognized initially. At our hospital, P. aeruginosa pheno- types resistant to ≥3 antimicrobial classes are monitored, but because many P. aeruginosa phenotypes fulfill this criterion, data were insufficiently granular to demonstrate an increase in MDR-PA that was specific to the outbreak. Furthermore, we identified several isolates that matched outbreak isolates based
on antimicrobial drug susceptibilities but were genetically unrelated to B1-derived isolates and to each other. This finding highlights the utility of WGS to confirm or refute horizontal transmission in the setting of outbreaks due to infectious pathogens. Our investigation has several limitations. Notably, isolates
from 8 patients were unavailable forWGS to strengthen the link between their B1 exposure and MDRO recovery. However, 6 of these 8 patients fulfilled case status on the same day as B1 exposure, so the epidemiologic link is strong even in the absence of genomic data. Patient 13 yielded MDR-PA 18 days after B1 exposure, and horizontal acquisition from an alternate source may have occurred, especially considering that patient 32 yielded an unrelated MDR-PA isolate 12 days after B1 exposure. Alternate sources of acquisition are also possible for the 10 patients whose isolates matched B1-derived isolates, because WGS cannot establish the directionality of transmis- sion. However, the fact that case status for 17 of 19 patients with presumed B1-derived MDRO acquisition was established on the same day as B1 exposure strengthens the epidemiologic linkage. In conclusion, we report an outbreak and pseudo-outbreak of
MDR-PA and CR-KP that were strongly linked to the con- tamination of a single, physically defective bronchoscope, and we provide genomic data to support our epidemiologic investiga- tion. In addition to adhering to endoscope reprocessing guide- lines, hospital epidemiology programs should prioritize thorough periodic maintenance of endoscopic devices and emphasize scrutiny of endoscope-derived culture data as an important intervention to hasten recognition of endoscope-associated outbreaks.
Acknowledgments. We extend our appreciation to Jessica Schlackman and Chinelo Ezeonwuka for their technical expertise and to Ryan Shields for his assistance in the procurement of microbial isolates. We also thank Vaughn Cooper and Dan Snyder for their assistance with whole-genome sequencing.
Financial support. No financial support was provided relevant to this article.
Conflicts of interest. L.H.H. reports having served on a scientific advisory board for GlaxoSmithKline on meningococcal vaccines. All other authors report no conflicts of interest relevant to this article.
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