This study prospectively investigated the associations between the prevalence of GNB and the point-oral exam among 55 hematology inpatients at a hospital. The prevalence of GNB was higher in patients with poor oral health (score of 5 or more in the point-oral exam) than those with good oral health (score of 4 or less). The results suggest that a value of 5 or higher is effective in identifying the presence of GNB, whereas a value of less than 4 might indicate the absence of GNB. To the best of our knowledge, this is the first study to focus specifically on the association between GNB detection rates and oral health scores.
The point-oral exam was categorized into four items (hygiene, xerostomia, mucositis, and occlusion) to evaluate its association with the prevalence of GNB. In the present study, the GNB detection group had poorer oral hygiene and xerostomia status compared with the GNB nondetection group. However, no significant difference in occlusion was observed between the two patient groups. Additionally, the evaluation items for mucositis could not be specified from this study because the 75th percentile of the score of xerostomia was low (1) in the detection and nondetection groups, making it difficult to distinguish between them based on the scoring, although there was a significant difference in scoring between the detection and nondetection groups.
Bacteria colonize in various parts of the oral cavity, including the dental plaque and the tongue. However, pathogenic bacteria, such as GNB, are rarely detected in the oral cavity of healthy individuals. On other hand, the frequencies of GNBs are reported to be high in hospitalized patients. Furthermore, patients with aspiration pneumonia and those who are medically compromised are known to have increased levels of GNBs in their oral cavity and pharynx . In the study by El-Solh et al. , GNBs were the most predominant organisms (49%) detected in bronchial samples from 67 patients with AP, followed by anaerobes (16%) and Streptococcus aureus (12%). In the present study, the detection rate of GNB was high at 45.5%, which was consistent with the results of previous studies[40, 41].
It has been reported that hospitalized patients, especially those with leukemia and bone marrow transplants, have higher rates of oral and pharyngeal GNB. Moreover, in one study, enteric microorganisms identified as Klebsiella (42.7%), Enterobacter (18.8%), and Pseudomonas (15.6%) were isolated from 62.2% of leukemia patients compared to 28% of controls [42, 43]. In some studies, the prevalence of GNB in the oropharyngeal flora correlated best with the clinical severity of the disease and motility in hematological inpatients [44–46]. Similarly, in the present study, ROC analysis suggested that a score of 5 or more on the oral assessment was associated with higher mortality due to the hematological disease.
This study may show that maintaining good oral hygiene and a moist oral mucosa might improve the condition of the oral cavity, a potential reservoir of GNB [47, 48], and reduce the retention of GNB in high-risk, hospitalized, hematological patients. Previous studies have shown that poor oral hygiene and xerostomia are closely related to increased bacteria, including GNB, in the oral cavity [49, 50]. On the other hand, according to the study by Senpuku et al., oral management (including hygiene and professional care) that involves the elimination of pneumonia-causing bacteria and fungi could diminish the risk of developing systemic diseases . These points of view suggest that maintaining the cleanliness and moisture of the oral cavity should prevent the development of systemic complications in hospitalized patients with hematological diseases, such as those requiring high-dose chemotherapy for leukemia and bone marrow transplantation. In our previous study, we reported that the group of patients with good nutritional status had a better oral health status and lower GNB prevalence than those with poor nutritional status . In the current study, GNB was frequently detected in eight out of ten malnourished patients who required strict nutritional management (data not shown).
One of the limitations of this study is that we did not use molecular biology techniques, such as polymerase chain reaction, to identify the species of the bacteria. In particular, the metabolic profiling of saliva should be adopted to detect and quantify the pathogens because this method can detect a higher proportion of various bacterial infections in the oral cavity than fluid cultures of the bronchoalveolar lavage, without causing any distress to the patient [52, 53]. Furthermore, culturing of these organisms in a future study is necessary to determine their sensitivity to various antibacterial agents and for application in the clinical setting. Although careful sputum sampling was conducted to reduce the risk of oral bacterial contamination in the present study, the possibility of contamination leading to inaccurate results cannot be ignored. A large-scale, multicenter, prospective cohort study is required to confirm the findings of this study and to ensure interobserver reliability.
The strength of the present study was that data management and analyses were performed by an independent biostatistician and a health information manager to exclude evaluator subjectivity. The evaluation method used herein could be easily implemented and evaluated by nontrained nurses if the assessment item of occlusion, which may require evaluation by a dentist, is excluded. Occlusion might not be an important item to evaluate since no significant difference in occlusion was noted between the detection and nondetection groups. However, the importance of each item should be determined by increasing the number of cases and conducting an inter-rater reliability test for the point-oral exam.
In conclusion, the present study demonstrated an association between the prevalence of GNB and oral health assessment in hematological inpatients. The prevalence of GNB was evidently higher in patients with poor oral health (score, ≥ 5 on the point-oral exam) than in those with good oral health (score, ≤ 4). Thorough oral management should be considered as early as possible in patients with a total score of ≥ 5, before full-scale treatment of the main disease.