Topical Povidone Iodine Inhibits Bacterial Growth in the Oral Cavity of Patients on Mechanical Ventilation

A Randomized Controlled Study

Shoma Tsuda; Sakiko Soutome; Saki Hayashida; Madoka Funahara; Souichi Yanamoto; Masahiro Umeda


BMC Oral Health. 2020;20(62) 

In This Article


One of the main causes of VAP is thought to be aspiration of oropharyngeal fluid containing pathogenic microorganisms. Based on this premise, researchers have attempted to reduce VAP through oral care. Munro and Ruggiero,[5] Pobo et al.,[10] and Lorente et al.[11] conducted randomized controlled studies of the effect of tooth brushing on VAP prevention. They concluded that mechanical tooth brushing is not effective in preventing VAP. In another study, Mori et al.[12] reported that swabbing with povidone iodine gargle, tooth brushing, and irrigation with 300 mL of acidic water decreased a risk of VAP in 1252 mechanically ventilated patients compared with 414 patients who did not receive these procedures. Sone et al.[13] also described that tooth brushing, rinsing with tap water, and application of 0.12% chlorhexidine could decrease frequency of VAP. However, their studies were conducted with historical controls. Moreover, it remained unclear whether their oral care procedures actually reduced oral bacteria and how long the effects of oral care lasted. Hayashida et al.[14] reported that number of bacteria in the oropharyngeal fluid increased rapidly after intubation without growth of dental plaque, and stated that dental plaque was not a main reservoir of oropharyngeal bacteria in mechanically intubated patients. Funahara et al.[15] also described that the number of bacteria in the saliva increased after surgery but was not related to dental status such as amount of dental plaque and number of teeth.

Hayashida et al.[14] reported that irrigation with tap water reduces oral bacteria in ventilated patients, but the number of bacteria in oropharyngeal fluid increased within 3 h after irrigation. Funahara et al. described that topical tetracycline ointment on the tongue reduces the number of bacteria in oropharyngeal fluid for about 6 h;[16] furthermore, in a multicenter randomized clinical trial, topical application of tetracycline ointment on the tongue every 6 h for 24 h after surgery significantly prevented surgical site infection in patients undergoing oral cancer surgery with flap reconstruction and tracheotomy.[17] Some studies have investigated the effects of oral decontamination on VAP prevention. Rodriguez-Roldán et al.[18] reported that topical application of a paste containing tobramycin, amphotericin B, and polymyxin E in the oral cavity reduced the risk of VAP in 13 ventilated patients, although the overall mortality was not improved. Abele-Horn et al.[19] also reported that the incidence of VAP was reduced by topical administration of that same paste in 58 ventilated patients. Bergmans et al.[20] reported that topical antimicrobial prophylaxis consisting of an orabase paste containing gentamycin, colistin, and vancomycin reduced the risk of VAP in 92 patients. However, these studies failed to demonstrate the effect of topical antibiotics on decreasing mortality rate or hospital day. Furthermore, antibiotic administration may promote the emergence of resistant bacteria; therefore, the topical use of antibiotics is not recommended for mechanically ventilated patients.

One meta-analysis has shown that topical 0.12% chlorhexidine is effective in preventing VAP.[21] Although topical application of 0.12% chlorhexidine is a standard procedure in patients undergoing mechanical ventilation, its use in the oral mucosa is not approved in Japan because of reports of anaphylactic shock. Similar to chlorhexidine, povidone iodine has antibacterial activity and is approved for use in the oral cavity. However, it is not commonly used to prevent VAP. It has been suggested that povidone-iodine is cytotoxic to normal mucosal cells, and it has been pointed out that prolonged use of povidone iodine may cause tooth coloring. The CDC guidelines 2017[22] recommend the use of iodine before wound closure during surgery, so we believe that the usefulness of the disinfecting effect outweighs the cytotoxicity concerns.

This randomized controlled study showed that topical application of 10% povidone iodine—an alternative to 0.12% chlorhexidine in Japan—after cleaning and irrigation of the oral cavity inhibited bacterial growth in the oropharyngeal fluid of patients on mechanical ventilation while not disrupting the balance of the oral microbiota. The present study showed that povidone iodine reduced the number of oral bacteria for at least 3 h after oral care in patients undergoing mechanical ventilation. Furthermore, the results of real-time PCR showed that topical povidone iodine did not disturb the balance of the oral microbiota or promote the growth of bacteria resistant to antibiotics (e.g., MRSA) or fungi. These findings suggest that topical application of povidone iodine is a simple and safe method to reduce oral bacteria for a longer time that could be used as standard prophylaxis against VAP in Japan—similar to 0.12% chlorhexidine globally. In this study, we investigated only up to 3 h after application, so it would be necessary to study for a longer time to establish an appropriate oral care method.

This study has some limitations. First, the sample size was small and the last measurements were obtained at only 3 h after oral care. Second, the outcome of the study was bacterial count, not the development of VAP. Therefore, we cannot conclude whether topical application of povidone iodine reduces the frequency of VAP, only that it inhibits bacterial growth in the oral cavity of patients undergoing mechanical ventilation. Further investigation is necessary to tackle these issues.