Our study found that during routine clinical care of patients with MDR bacteria, HCWs frequently contaminate protective gowns and gloves. This happens with MDR A. baumannii more often than other common MDR bacteria. Approximately one of every three times a HCW enters the room of a patient with MDR A. baumannii, they will contaminate their gowns or gloves. Some HCWs in ICUs with MDR bacteria have contaminated hands at the time of room entry. Patient rooms were often contaminated with MDR bacteria, especially MDR A. baumannii. We found that environmental contamination was the best predictor of MDR bacteria transmission to HCW attire.
HCWs frequently become contaminated with MDR bacteria. Using a highly sensitive method, Hayden and colleagues (13
) found that 62% of HCWs who entered the room of patients known to be colonized with VRE contaminated their gloves or hands during care. In experiments of transmission in which investigators touched prespecified areas on a patient or patient room and then imprinted their gloved hands to culture medium, MRSA was found to be transferred to gloves after approximately 30% to 60% of contacts (13
). Using the same method used in the current study with fewer patients and statistical analysis that did not account for clustering, we have examined frequency of contamination with MRSA and VRE (11
) and MDR A. baumannii
or MDR P. aeruginosa
). We found a similar frequency of transmission of MDR bacteria in these studies. The impact of contamination of HCW clothing is not precisely understood. Presumably, HCW contamination with MDR bacteria is a key step in transmission to other patients. A study by Duckro et al (15
) demonstrated that contaminated HCW hands were capable of transmitting VRE to inanimate surfaces. The frequency that HCW contamination results in transmission to patients is unknown. In our study, even after appropriate use of gloves and gown while caring for a patient on contact precautions, 1.7% to 4.2% of HCWs had a MDR bacterium on their hands without hand hygiene. This emphasizes the importance of hand hygiene after removal of gloves and gown (9
Overall, 8% of HCW room entries occurred with a HCW who had MDR bacteria on their hands. The source of contamination of HCW hands may have been prior patient contact or contact with the environment. HCW hand contamination represents a significant potential for transmission and supports Centers for Disease Control and Prevention recommendations to perform hand hygiene before room entry (9
). Alternatively, universal use of gown and gloves for all patient contact in the ICU may best address this problem (16
MDR A. baumannii contaminated HCWs and patient rooms more frequently than other MDR bacteria. MDR A. baumannii was present in 78% of rooms housing a patient colonized with MDR A. baumannii. Similarly, HCWs entering the room of patients had MDR A. baumannii on their hands approximately 4% of the time, twice as often as other bacteria.
The current study supports the hypothesis that MDR A. baumannii
is transmitted more frequently than other MDR bacteria. This increased propensity to contaminate hands, clothing, and the environment may, in part, explain the recent emergence of MDR A. baumannii
). Future research is needed to explore characteristics of MDR A. baumannii
that lead to this result.
A greater risk of contamination was observed when HCWs performed a physical examination or remained in the room longer, which are similar to risks of contamination described previously (4
). Contact with a ventilator was associated with a greater risk of contamination, most likely because the respiratory tract is often heavily colonized with MDR bacteria and contact with respiratory equipment may pose a particular risk (4
). The strongest predictor of HCW contamination was a patient room being found to be contaminated with MDR bacteria. HCWs entering a room that had environmental contamination with MDR bacteria were over four times as likely to become contaminated with that organism. Although studies have found an association between environmental cleaning and decreased risk of hospital-associated infections (17
), the mechanism of and interventions for environmental contamination and transmission of MDR bacteria are not well defined. Our study supports the idea that contamination of a patient’s room increases the likelihood of transmission (19
The reason environmental contamination poses such a significant risk for HCW contamination is unclear. In our study, model building included a variable describing number of times a HCW contacted the environment. Frequency of HCW contact with the environment was not significant in the final model, whereas environmental contamination was. This dichotomy is perplexing but an important finding. It may be that patients who contaminate the environment with MDR bacteria are also more likely to contaminate HCW gowns and gloves through direct patient contact. We did not culture patients for MDR bacteria and cannot address the possibility that patients who contaminated the environment had a greater burden of organism. This should be addressed in future studies. Alternatively, contamination of the environment may be the critical step in contamination of HCWs. The latter option would indicate that transmission of MDR bacteria could be significantly decreased with more aggressive daily environmental cleaning. We also did not collect data relative to most recent environmental cleaning, although this would have been done daily, typically within 2–4 hrs of data collection. At a minimum, contamination of the environment appears to be a marker for a patient room at greater likelihood of HCW contamination.
The best method to control the spread of MDR bacteria in the ICU is unknown. Recent studies have focused on detecting and isolating patients for a specific organism such as MRSA (23
). Detecting and isolating patients has been studied alone (23
) or combined with other interventions, including better hand hygiene, compliance with isolation, and preventive methods for specific healthcare-associated infections (24
). Large multicenter studies such as these are necessary to evaluate infection prevention initiatives. Evidence from ours and other studies (13
) suggest that environmental cleaning may be appropriate to study in a multicenter intervention trial.
Limitations of this study include that it was a single-center study with a modest number of patient rooms sampled. Because HCW participation was anonymous, we could not adjust for repeated measurements from the same HCW, although we adjusted for multiple observations on the same patient using generalized estimating equations. Although we knew 318 interactions occurred with a HCW on their first experience with the study, we did not know how many times other HCWs may have been observed. Although active surveillance for MDR bacteria is different in different ICUs, this potential bias is unlikely to have had an effect on reported rates of contamination because frequency of transmission did not differ by individual ICU. Although we had a significant detection rate of MDR A. baumannii
, our sampling technique may have been insensitive compared with others (25
). We did not record time of most recent environmental cleaning and did not assess effectiveness of cleaning. We were unable to assess which or how many patients’ anatomic sites were originally positive as a measure of organism burden, which has been associated with transmission of MRSA (10
In conclusion, MDR A. baumannii was transmitted in approximately one in three interactions with colonized patients, which was much more frequent than other MDR bacteria. Environmental contamination and contamination of HCW hands before entry were twice as common with MDR A. baumannii compared with other MDR bacteria, implying that the emergence of MDR A. baumannii may be related to its ability to proliferate and spread on inanimate objects. Transmission of MDR bacteria to HCW clothing was common for all MDR bacteria, emphasizing the importance of improving compliance with contact precautions. Environmental contamination with an MDR bacterium was the major predictive factor in HCW contamination during patient care suggesting that efforts to decontaminate patient rooms during their stay may decrease transmission.