Frequency of isolation of nosocomial pneumonia pathogens from the respiratory tract of cardiac surgery hospital patients who are under extended artificial lung ventilation and efficiency of oral cavity sanitation with chlorhexidine solution

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INTRODUCTION

          Patients in intensive care units in 9–65% of cases develop nosocomial pneumonia (HA) associated with artificial lung ventilation (ALV) [1, 2]. The artificial airways created by the ventilator are thought to reduce the ability to swallow. In this case, bacteria enter the lower respiratory tract mainly from the oral cavity through the gap between the wall of the tracheal tube and the respiratory tract [2, 3]. At the same time, parallel bacteriological studies of the contents of the oral cavity and tracheobronchial tree were carried out mainly in healthy people [4] and patients with chronic lung pathology [5, 6]. At the same time, in the available literature, we were unable to find works in which such bacteriological studies would be carried out in the same patients during prolonged mechanical ventilation.

           In the prevention of CAP associated with mechanical ventilation, sanitation of the upper respiratory tract is of particular importance. In medical organizations of the Russian Federation, the above procedure is included in the list of medical services technologies regulated by the National Standard [7]. The standard recommends in the process of mechanical ventilation to carry out the sanitation of the upper respiratory tract (nose and oropharynx) by mechanical cleaning of the teeth. Meanwhile, the literature discusses the question of the advisability of including the use of antiseptics in the oral sanitation algorithm [8].

The aim of the study was to assess the frequency and degree of bacterial contamination of the respiratory tract of patients in a cardiac surgery hospital who are on prolonged mechanical ventilation, and the effectiveness of sanitation of the oral cavity with a solution of chlorhexidine.

MATERIALS AND RESEARCH METHODS 24 adult patients of the anesthesiology and resuscitation department of the cardiosurgical hospital, who were on extended mechanical ventilation, were under observation. The selection of clinical material (contents of the oral cavity and lower respiratory tract) for bacteriological examination was performed 48-72 hours after the start of intubation in accordance with the recommendations [9]. The selection of smears from the oral cavity was carried out using sterile swab probes, the contents of the tracheobronchial tree - using a bronchoscope. After sampling, the patients' oropharynx was sanitized in accordance with the approved procedure for the care of the respiratory tract [7]. Additionally, special oral care sticks soaked in a 0.1% aqueous solution of chlorhexidine sequentially treated the vestibule of the oral cavity, teeth, back of the tongue, root of the tongue and oropharyngeal mucosa. After sanitation, re-sampling of the contents of the mouth for bacteriological examination was carried out. The total number of samples from 24 patients was 72. Bacteriological studies were performed in the clinical diagnostic department of the cardiosurgical hospital. The concentration of microorganisms in the clinical material was determined by a semiquantitative method [10]. To do this, the material was seeded on a dense nutrient medium in a Petri dish, divided into four equal sectors. After incubation of the material at 370 C for 24 hours, the number of colonies of microorganisms in each sector was counted and, using a special table, the indicators of microbial contamination were determined. Subsequently, microorganisms were identified on a Phoenix M 50 bacteriological analyzer (USA). For Gram-positive microorganisms, the PMIC/ID-600 panel was used; for Gram-negative microorganisms, the NMIC/ID-435 panel was used.

During statistical processing of materials, confidence intervals of indicators (0.95% CI) were determined using the WinPepi program, version 11.65 (authored by Professor Joe Abramson, Israel). The statistical significance of differences in the frequency of isolation of microorganisms was assessed using the Fisher test. Comparison of indicators of the intensity of microbial contamination was carried out with the calculation of the arithmetic mean number of microorganisms (M), standard error (m) and parametric Mann-Whitney U-test. At p < 0.05, the difference in indicators was considered statistically significant.

RESULTS AND ITS DISCUSSION

          The results of bacteriological studies of the contents of the respiratory tract showed (Table 1) that 36 strains of microorganisms were isolated from the oral cavity of 24 patients, and 23 strains from the lower respiratory tract. The microbiota of the oral cavity and tracheobronchial tree in patients on prolonged mechanical ventilation was represented by gram-positive (Staphylococcus epidermidis), gram-negative (Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii) microorganisms, as well as fungi of the genus Candida. At the same time, the frequency of isolation of bacteria found in the oral cavity and in the bronchi did not differ (p > 0.05 in all cases).

The study of the degree of microbial contamination of the respiratory tract made it possible to establish (Table 2) that the average number of colony-forming units (CFU) of certain types of bacteria isolated from the lower respiratory tract of patients was lower than from the oral cavity. However, statistically significant differences between these indicators in most cases, apparently due to a small number of studies, could not be found. At the same time, the average amount of   S. epidermidis in the contents of the lower respiratory tract compared with the upper respiratory tract decreased statistically significantly, namely, by 12.4 times (p = 0.05).

Evaluation of the effectiveness of sanitation of the oral cavity using a 0.1% aqueous solution of chlorhexidine showed (Table 3) that the species composition of the oral microflora did not change after the procedure. S. epidermidis, K. pneumoniae, P. aeruginosa, A. baumannii, and fungi of the genus Candida were isolated both before and after sanitation. There were no statistically significant differences in the frequency of detection of pathogens before and after sanitation (p > 0.05 in all cases).

   Assessment of the degree of contamination of the oral cavity before and after sanitation with chlorhexidine revealed a statistically significant decrease in the average number of A. baumannii (by 5.8 times) and fungi of the genus Candida (by 13.8 times) (p = 0.05 and 0.02, respectively). The decrease in the degree of sample contamination by other microorganisms was not statistically significant.

The results of the studies indicate that the composition of the microbiota of the oral cavity of patients on prolonged mechanical ventilation does not differ from the microbiota of the tracheobronchial tree. Indicators of the frequency of isolation of opportunistic microorganisms and the degree of microbial contamination of the contents of the lower respiratory tract were comparable to those of the oral cavity. The exception is S. epidermidis, the number of which in the lower respiratory tract decreased statistically significantly compared to the upper ones. These data confirm the aspiration of microorganisms from the upper respiratory tract to the lower during the ventilator procedure. At the same time, the site of the maximum pre-aspiration concentration of microorganisms in an intubated patient may be the subglottic space between the outer wall of the endotracheal (intubation) tube in front, the tracheal skeleton in the back, the glottis from above, and the cuff of the endotracheal tube of the trachea from below [11]. In this regard, the search for effective methods of sanitation of this space in the process of mechanical ventilation seems to be relevant.

In cardiac surgery patients, after the sanitation procedure with the use of a 0.1% aqueous solution of chlorhexidine, a statistically significant decrease in the number of A. baumannii and fungi of the genus Candida was noted, which indicates the microbiological effectiveness of the use of this antiseptic in the process of oral care and the feasibility of including this procedure in the algorithm sanitation of the respiratory tract of patients on prolonged mechanical ventilation.

CONCLUSIONS

1. Indicators of the frequency and intensity of isolation of opportunistic microorganisms (K. pneumoniae, P. aeruginosa, A. baumannii, fungi of the genus Candida) from the oral cavity and lower parts of the respiratory tract in patients of a cardiac surgery hospital who are on prolonged mechanical ventilation do not have statistically significant differences. The exception was S. epidermidis, the number of which in the lower respiratory tract is lower than in the upper ones.
2. The microbiological efficiency of using a 0.1% aqueous solution of chlorhexidine in the process of sanitation of the oral cavity of patients on prolonged mechanical ventilation has been established.

About the authors

Larisa G. Kudryavtseva

S.G. Sukhanov Federal Center of Cardiovascular Surgery

Author for correspondence.
Email: kudryavcevalg@mail.ru
ORCID iD: 0000-0002-2707-0768

Candidate of Medical Sciences, Head of the Epidemiological Department, epidemiologist

Russian Federation, Perm

Victor I. Sergevnin

E.A. Vagner Perm State Medical University

Email: viktor-sergevnin@mail.ru
ORCID iD: 0000-0002-2729-2248

MD, PhD, Professor of the Department of Epidemiology and Hygiene

Russian Federation, Perm

Olga G. Pegushina

S.G. Sukhanov Federal Center of Cardiovascular Surgery

Email: pegushina.olga2011@yandex.ru
ORCID iD: 0000-0002-9904-0760

bacteriologist

Russian Federation, Perm

Alexey V. Krasotkin

S.G. Sukhanov Federal Center of Cardiovascular Surgery

Email: kav@permheart.ru
ORCID iD: 0000-0003-2259-528X

Head of the Department, anesthesiologist-resuscitator

Russian Federation, Perm

Marina M. Vorobyova

S.G. Sukhanov Federal Center of Cardiovascular Surgery

Email: marina.w71@mail.ru

head nurse of the Department of Anesthesiology and Resuscitation

Russian Federation, Perm

References

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