The oral cavity of hospitalised and bedridden patients is often a reservoir for opportunistic respiratory pathogens (Boaden et al., 2017; Tada & Miura, 2012), and can thus serve as a source of infection for the lungs if aspirated. There is a significant correlation between the presence of pathogenic bacteria in the oral cavity and the occurrence of respiratory diseases, such as pneumonia, especially in people who present with dysphagia (swallowing impairment) (Fernández & Clavè, 2013; Konradsen, Trosborg, Christensen, & Pedersen, 2012; Simpelaere, Nufflen, Vanderwegen, Wouters, & De Bodt, 2016; Sørensen et al., 2013; Yoon & Steele, 2012). Swallowing is a complex neuromuscular activity that consists of oral, pharyngeal and oesophageal phases, and involves the coordinated function of many muscles (Hiramatsu, Kataoka, Osaki, & Hagino, 2015). Physiological deficits in any of the swallowing phases result in dysphagia (González-Fernández & Daniels, 2008) and may affect swallow efficacy (deficits with mechanical clearance) and/or safety of the swallow (subsequent aspirations). Impaired safety of the swallow not only increases the risk for aspiration and the uncontrolled introduction of pathogenic pathogens into the lower respiratory tract (Fernández & Clavè, 2013), but has also been associated with the presence of gram-negative bacteria; dysphagia is thus an important risk factor associated with the development of aspiration pneumonia (AP).

The incidence of pneumonia caused by aspiration of pathogenic bacteria in patients who present with dysphagia, increases both the mortality and the need for acute care hospitalisation (Sørensen et al., 2013), which in turn can impact on oral hygiene (Danckert, Plummer, & Williams, 2016; Neto, De Paula Ramos, Sant’ana, & Passanezi, 2011; Tada & Hanada, 2010). This is partly because of the fact that oral infections often remain asymptomatic and may still result in bacteraemia despite an absence of overt symptoms (Rautemaa, Lauhio, Cullinan, & Seymour, 2007). Oral care practices are often an overlooked component in the care of hospitalised patients (Chipps et al., 2014) as poor oral hygiene is not a highly visible condition, and related concerns, such as gingivitis and dental plague require a closer inspection of the mouth (Yoon & Steele, 2012). Furthermore, potentially pathogenic bacteria are frequently carried in the oral cavity and hospitalisation appears to create conditions that favour oropharyngeal colonisation (Boaden et al., 2017). The problem, however, is that dysphagia is often a symptom of multiple diseases and disorders, such as neurological disorders, cerebrovascular and neurodegenerative diseases that often require hospitalisation. Moreover, these diseases and disorders are often accompanied by impaired communication making dysphagia and its repercussions such as oral bacterial colonisation a highly invisible disorder and a silent epidemic. Unless we increase our knowledge and strengthen our understanding of the risk posed by poor oral hygiene to individuals with dysphagia, opportunistic respiratory bacteria originating in the mouth have the potential to become the silent killer of vulnerable hospitalised patients who present with dysphagia.

Data were collected during two stages: (1) a CSE and (2) an oral health assessment. The oral health assessment consisted of two components, namely visual inspection of the oral cavity and microbiology laboratory testing of oral swab samples.

The clinical data from the MASA, the OHAT and the microbiology swab results were analysed, using descriptive statistics, namely univariate analysis, to describe and summarise patterns found in the data. Statistical analyses of data included frequency distribution, central tendency (mean, median and mode) and measures of variability (range and standard deviation).

Pulse oximetry and CA were used as adjuncts to the MASA assessment during the CSE, as a means to increase sensitivity and specificity of the MASA findings. To determine whether the relationship between the variables was statistically significant, categorical data from the PO, CA and MASA scores were tested using a test of independence, namely the Fischer’s exact test. The statistical analysis was performed using SPSS^TM Version 24, a p-value of ≤ 0.005 being considered significant. A cross-tabulation between (1) MASA scores and PO and (2) MASA scores and CA was done. More than 20% of the cells have an expected count of less than 5 and thus Fischer’s exact test was used. The MASA scores were split into three groups: (1) lower – score less than MASA quartile 1 value for the 40 respondents; (2) average – score between MASA quartile 1 and quartile 3 values; and (3) higher – score greater than MASA quartile 3. A significant correlation was found between PO and the MASA score. The p value was less than 0.005. Those who pass the PO have significantly higher MASA scores (almost double) than those who fail; thus confirming results of MASA. Similarly, the p value for CA to MASA scores was 0.000 indicating a significant association between the two. Results thus indicate that the two supplemental procedures PO and CA had a high rate of agreement with the MASA findings.

This study found that the majority of participants did not present with satisfactory oral hygiene, with a high prevalence of bacterial colonisation. Furthermore, poor oral hygiene status was associated with hospitalisation and not limited to those presenting with dysphagia. The findings support those of previous studies, which report the prevalence of oral health problems amongst acutely hospitalised patients to be very high (Danckert et al., 2016; Matthews et al., 2012; Tada & Hanada, 2010). In recent years, the interaction between opportunistic respiratory pathogens and Candida albicans has been reported (Dahlén, 2009). This finding was corroborated in the current study, as the most commonly occurring bacteria in the oral cavity of participants were (1) Candida species and (2) opportunistic respiratory pathogens. In five (17.5%) participants, Candida albicans was found to co-occur with an opportunistic respiratory pathogen.

In the context of oral health, stroke can cause hemiparesis and hemiplegia to the muscles of the pharynx, tongue and palate and the muscles of mastication, resulting in an impaired ability to chew and grind food and reduced oral clearance. Plaque biofilms are dislodged by the movement of the oral musculature, such as the cheeks and tongue, during speech and mastication (Kilian et al., 2016). Furthermore, studies have shown that effective salivary flow and swallowing is needed to clear bacteria-laden secretions from the oral and pharyngeal cavities (Ortega et al., 2015; Palmer, 2008). In this study, poor mechanical clearance of the bolus, which included the clearance of accumulated saliva, was found to be an area of significant difficulty for most participants with dysphagia. This resulted in oropharyngeal residue that was particularly related to tongue weakness and difficulties with coordination. According to Palmer et al. (2001), the reduction in mechanical clearance of potential pulmonary and oropharyngeal pathogens may be the first step in the path that leads to oral pharyngeal colonisation and pneumonia. Oropharyngeal residue that is not cleared promotes bacterial growth and invasion as pathogens have increased time in the mouth for proliferation. Reduction in mechanical clearance could also account for the finding that all participants presented with deficient oral cleanliness related to the accumulation of plaque, saliva and debris. The motor function of the tongue is described to be related to its self-cleaning function. Reduced activity as a result of weakness possibly accounts for the finding that 80% of the study participants had oral hygiene issues related to the tongue, more specific to tongue coating. This finding is concerning as studies have identified the dorsum of the tongue as a major oral site of bacterial multiplication, as well as a major source for the bacteria found in saliva. This indicates that many salivary bacteria mirrors those coming from the flora of the dorsum of the tongue (Danser, Go´mez, & Van der Weijden, 2003; Kikutani et al., 2009; Pace & McCullough, 2010) which could account for the high prevalence of pathogenic bacteria found in the oral cavities of participants with dysphagia. Participants with dysphagia were found to have more food debris, plaque, poorer oral clearance and more denture problems. This can be ascribed to functional impairments of the oral phase of the swallow, such as reduced orofacial muscular control and loss of oral sensory function, which are symptoms and complications of disease processes, such as cerebrovascular accident (CVA) that affect the efficacy of the swallow. These deficits may thus have the potential to significantly affect oral hygiene, creating a favourable environment for pathogenic bacteria to grow and colonise.

It has been extensively researched and is well known that oral microbiota contributes to oral and general well-being and its loss can be detrimental to the health of the individual. Numerous studies have implicated oral colonisation with pathogenic bacteria as a precursor condition contributing to AP risk. Participants in the current study presented with an increased number of pathogenic oral bacteria, with only 15 participants presenting with normal oral flora. It was interesting to note that the larger majority of participants presented with bacteria strains commonly associated with the acquisition of nosocomial infections, such as bacterial pneumonia. Infection control efforts are applied in hospitals to prevent nosocomial infections, with microbiology surveillance often put into place to detect harmful microorganisms before they have the chance to ensue disease. Research states that as long as the microbial load is not too high, the harmony between pathogenic bacteria and oral resident flora will not be tilted toward infection (Danser et al., 2003; Rautemaa et al, 2007). However, the results of this study indicate that when bacterial species were found in the oral cavities of participants, the virulence was already quite high. This bacterial virulence suggested the delicate oral homeostasis had potentially already been tipped toward infection and if not treated could potentially lead to systemic disease such as AP. In this study, 70% of participants presented with some degree of risk for aspiration -– thus presenting with an increased likelihood to aspirate pathogenic bacteria, which could overburden the host defence mechanisms and lead to infection, resulting in longer hospital stays, costly care and possible death (Terpenning & Shay, 2002). The monitoring of oral bacterial colonisation may thus be crucial in determining the risk for pneumonia in hospitalised patients who present with risk factors such as dysphagia (Yoon & Steele, 2013).

Pain is a key indicator for patients and medical professionals, such as nurses, that something is wrong (Germossa, Hellesø, & Sjetne, 2019). An interesting finding of the study was that although oral hygiene was poor, 83% of participants (n = 33) demonstrated no signs of oral and/or dental pain, with no participants having any verbal reports of pain. Because of the nature of the clinical population, such as increased reliance on others for care including oral hygiene, communication disorders and the resulting inability to effectively communicate their needs, people with dysphagia can be regarded as a voiceless population. Furthermore, it is known that oral hygiene issues may not be painful and often remain asymptomatic (Dahlén, 2009), requiring further inspection. These patient factors in combination with the asymptomatic nature of oral hygiene problems highlight the silent nature of oral diseases.

Thus, because of the nature of the patient population, interprofessional collaboration and problem solving between dental staff, nurses and speech-language therapists is required to address patient oral care during hospitalisation.

This study demonstrated that the oral hygiene status of hospitalised patients who present with dysphagia is concerning. Patients with dysphagia may present with many oral hygiene problems, which may lead to a high prevalence of colonisation of respiratory pathogens. The findings of this study not only corroborate the findings from previous research, which indicated that oral hygiene is poor during hospitalisation, but also provide novel information regarding the oral hygiene problems people with dysphagia present with. Furthermore, it highlights the fact that oropharyngeal swallowing disorders in conjunction with poor oral hygiene, constitute an increasing problem for the often silent hospitalised patient who presents with co-morbid communication disorders. Hospitalised patients with dysphagia thus require greater vigilance in oral care, which may include improved screening of oral hygiene and frequent and professional dental care during hospitalisation, to minimise the potential effect of this undetected, silent killer.

The study employed a relatively small sample size of only 40 participants. Furthermore, the study location was a sub-acute rehabilitation hospital based within the private sector in South Africa. Patients admitted there thus had private medical aids and would present with very different socio-economic characteristics compared to those admitted to a government facility. As a result, the researcher does not expect the sample from this study to be representative of all hospitalised patients in South Africa. Future research in South Africa should focus on obtaining population representative data by investigating oral hygiene in both private and government institutions, as well as utilising a larger sample size.