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



This is a randomized phase II trial conducted before a large-scaled phase III study with the onset of that VAP as the primary endpoint. This study adheres to CONSORT guidelines. The primary endpoint of the current study is the difference in the number of total bacteria in the oropharyngeal fluid between patients receiving standard oral care and those treated with topical povidone iodine in addition to oral care at 3 h after intervention. From the results of our previous study, assuming that logarithm of number of bacteria in the oropharyngeal fluid after 3 h in the control group is 7.0 ± 0.8 cfu/mL and it reduces to 6.0 cfu/mL in the intervention group, when assigned by 2:1, alpha error is 0.05, and power is 80%, the required number of cases is 24 cases. The allocation will be determined by data manager responsible for biostatistical analysis. This open-labeled, randomized controlled study included 23 patients who received mechanical ventilation in the intensive care unit of Nagasaki University Hospital between April and September 2018. Inclusion criteria are 20–90 years old patients with ventilator by oral intubation. One patient who could not collect saliva due to dry mouth was excluded from the study. Informed consent to participate was obtained in writing for patients admitted for surgery, but in some patients for emergency admission verbally from family members.

Consent for Publication

Intervention. All patients received oral care by a dentist and dental hygienist at the same time every day. Oral care consisted of wiping with 3% hydrogen peroxide (Oxydol; KENEI Pharmaceutical Co., Ltd., Osaka, Japan) and irrigation with 200 mL of tap water plus suction. The patients in the intervention group received 5 mL of 10% povidone iodine (Isodine; Shionogi Seiyaku Co., Ltd., Tokyo, Japan) applied topically in the oral cavity (Figure 1). 5 ml of povidone iodine was dripped into the oral cavity including the gingiva, tongue and buccal mucosa using a syringe. Care was taken with suction through the oropharynx to prevent the patient from aspirating the tap water or povidone iodine. After washing, suction was performed through the side tube of the tracheal cannula.

Figure 1.

Oral care method. a Wiping of the oral mucosa with 3% hydrogen peroxide; b irrigation with tap water; c topical application of 10% povidone iodine

Measurement of the Concentration of Total Bacteria in the Oropharyngeal Fluid by the Rapid Oral Bacteria Quantification System. The concentration of total bacteria in the oropharyngeal fluid was determined using the Rapid Oral Bacteria Quantification System (Panasonic Healthcare Co. Ltd., Osaka, Japan), which is based on dielectrophoresis and impedance measurements.[8,9] To collect the samples, a cotton swab was immersed in oropharyngeal fluid for 5 s before oral care and 1 min, 1 h, 2 h, and 3 h after oral care. Next, to determine the bacterial count, the cotton swab was inserted into the apparatus.

Estimation of the Number of Some Oral Microorganisms by Real-time Polymerase Chain Reaction (PCR). To determine changes in the balance of the oral microbiota in the intervention group, 0.1–0.2 mL of oropharyngeal fluid were collected with a syringe before oral care and 1 min, 1 h, and 3 h after oral care. Genomic DNA from oropharyngeal fluid was isolated using a DNA extraction kit (InstaGene Matrix; Bio-Rad Laboratories, Hercules, CA, USA) according to the manufacturer's instructions. After adding 200 μL of InstaGene Matrix to the precipitate and incubating at 56 °C for 30 min, the sample was stirred and incubated at 100 °C for 8 min. All samples were stored at − 20 °C after the above processing. Samples were thawed immediately prior to quantitative real-time PCR and centrifuged at 10,000×g for 10 min at 4 °C. The supernatant was used to estimate the number of bacteria and generate the standard calibration curve for quantitative real-time PCR.

The concentration of streptococci, methicillin-resistant Staphylococcus aureus (MRSA), Streptococcus pneumoniae, Pseudomonas aeruginosa, Porphyromonas gingivalis, and Candida albicans were estimated based on real-time PCR data. For the standard calibration curve for quantitative real-time PCR, the DNA sequence of the target microorganism was synthesized, and artificial DNA was used (Figure 2). The reaction solution (total volume, 20 μL) contained 10 μL of KOD SYBR® qPCR Mix (TOYOBO Co., Ltd., Osaka, Japan), 1 μL of oropharyngeal fluid DNA sample, 3 μL of primers for each target microorganism (Table 1), and 6 μL of deionized water per well. After the initial heat denaturation at 98 °C for 2 min, the target DNA was amplified by carrying out 40 cycles of two steps: 95 °C for 20 s (heat denaturation) and 62 °C for 90 s (annealing). After completion of amplification, fluorescence signals were detected at 95 °C for 15 s, 60 °C for 30 s, and 95 °C for 15 s to generate a melting curve, and the specificity of the amplified product was confirmed. Data were analyzed using Thermal Cycler Dice® Real-time System software (TaKaRa BIO Inc., Shiga, Japan). The concentration of microorganisms in oropharyngeal fluid was the copy number estimated based on the amplification and calibration curves.

Figure 2.

Artificial DNA sequences used in real-time polymerase chain reaction

Statistical Analysis

The data of patients characteristics were analyzed by means of descriptive statistics and inferential statistics. The differences between total bacterial counts in the intervention and control groups were analyzed by the Mann–Whitney U-test, using SPSS software (version 24.0; Japan IBM Co., Ltd., Tokyo, Japan).