1 Introduction

Patients in an intensive care unit (ICU) are more prone to hospital-acquired infections than those in a general ward because of their critical condition, complex disease state, atraumatic surgery as well as their weakened immunity to pathogenic bacteria. Song Xiaochao et al. reported a higher incidence of hospital-acquired infection in an ICU compared with general wards, especially ventilator-associated pneumonia and bacterial infections [1]. Cross-infection among patients is highly likely to happen when patients are nursed in an open ICU with a consequent increasing multi-drug resistant bacterial [2]. Bacterial is usually transmitted in a direct or indirect way, mainly by the hands of medical personnel and contact with environmental surface [3]. Reducing such transmission will help prevent hospital-acquired infections and will improving ward management. Nonetheless, there is insufficient evidence to support the establishment of single room ICUs [4, 5]. Few hospitals in developed countries and even fewer in China have adopted a single room ward management model and there is no global consensus on its benefit. In 2019, the Department of Critical Care Medicine of the First Affiliated Hospital of Bengbu Medical College (hereafter referred to as “our department”) moved to a department comprised only of single-room wards, and re-enforced methods of infection prevention and control. To determine whether single-room management could reduce the incidence of hospital-acquired infection in an ICU, we analyzed the changes in the type of pathogenic bacteria and drug resistance patterns over a period of 5 years.

2 Materials and Methods

2.1 Setting of Wards

Based on the “Chinese Expert Consensus on Prevention and Control of Multi-drug Resistant Bacteria Hospital Infections” [6], our department moved into a new department in 2019 comprised of only single rooms. Unlike the previous open-plan ward (14 beds separated by curtains and unified management of all patients), the new ward is divided into two patient areas, A and B, with 21 beds in A and 18 beds in B. All beds are multi-functional and fully adjustable in a fully equipped single room,it can be seen in Fig. 1, layout of the single room ward. They are the holistic view of the single room ward, internal view of the single room ward, left view of the single room ward, right view of the single room ward. This offered many advantages for infection control and prevention.

Fig. 1
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Layout of the single room ward. a Holistic view. b Internal View. c Left view.b Right view

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First, it is established that transmission of multi-drug resistant bacterial infection is related to direct contact and a contaminated environment [7, 8]. When adopting the new management model of single-rooms, each room had induction doors. Windows between rooms enabled a clear view by staff of other patients while keeping patients apart. Curtains provided privacy when required. When patients were moved out of a room, the room was disinfected using ultraviolet light. Second, all equipment in each room is disinfected between patients. Each room is fully equipped with its own ventilator, piped oxygen, tubing and masks, stethoscope and hand disinfectant and alcohol-based hand sanitizer. Medical equipment that must be shared such as wheelchairs, transfer beds, portable ventilators and ECG machines, are disinfected after each use. Third, a strict system of hand washing is in place. Staff are required to wash and disinfect their hands before and after contact with each patient. Increasing the frequency of hand washing and the use of hand disinfectant as well as regular reinforcement of correct handwashing technique improves hand hygiene. Fourth, a strict isolation system is established. If a patient is infected with a certain bacteria, an isolation sign is placed on the automatic door as a reminder for staff to maintain good hand hygiene. Finally, number of personnel caring for an infected patient is kept to a minimum. The ratio of nurses: beds is maintained at 1:3 and the length and number of family visits is limited to reduce the chance of air contamination [9].

2.2 Collection of Data

Information about pathogenic bacteria and patterns of drug resistance from patient samples were reviewed from January 2016 to December 2020. Data were also obtained from the Anhui Province Bacterial Drug Resistance Surveillance Network (Hui Net) [10].

Results were analyzed in two groups by time: prior to January 2019 (data from 2016–2018 when the ICU was open-plan) and between January 2019 and 2020 when the ICU had adopted single-room management.

2.3 Observation Index

Results of all samples that underwent microscopy, culture and sensitivity testing were collated from January 2016 to December 2020 and strains of pathogenic bacteria and any changes associated with drug-resistance recorded and analyzed. The main observation measures were: the distribution of pathogenic bacteria and sources in the ICU over the last 5 years; drug resistance rates of common pathogenic bacteria and their resistance to commonly used antibiotics; trend of some specific drug-resistant bacteria.

2.4 Data Processing

EXCEL was used to collect the data, and SPSS 26.0 for data analysis. Count data and rates between the two groups were compared by χ2 test with p < 0.05 considered statistically significant.

3 Results

3.1 Distribution of Pathogenic Bacteria in the ICU over the Last 5 years

The number of pathogenic bacterial species isolated in our department was 320 in 2016, 246 in 2017, 397 in 2018, 559 in 2019 and 601 in 2020, with an overall increase rate of 87.9%. The majority were Gram-negative (84.69–80.70%) with significantly fewer being Gram-positive (15.31–19.30%). Table 1 shows changes in the number and composition ratio of pathogenic bacteria detected. The total number of beds in the department was 14 between 2016 and 2018, and 39 between 2019 and 2020. The corresponding ratio of total number of pathogenic bacteria to number of beds was respectively for the 5 years 2016–2020, 22.86, 17.57, 28.36, 14.33, and 15.41, revealing a decreasing trend (P < 0.05). The ratio of the number of Gram-negative bacteria detected to the number of beds also showed a decreasing trend (P < 0.05). Although the change for Gram-positive bacteria showed a similar decreasing trend, it was not statistically significant (P = 0.268), Fig. 2 and Table 2 show trends in the ratio of the number of pathogens detected to the number of beds in 2016–2020, statistical analysis of the ratio of the number of pathogens detected to the number of beds in 2017–2020.

Table 1 Changes in the number and composition ratio of pathogenic bacteria detected
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Fig. 2
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Trends in the ratio of the number of pathogens detected to the number of beds in 2016–2020. The vertical scale indicates the ratio of the number of bacteria to the number of beds (strain/sheet). The horizontal scale indicates the year

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Table 2 Statistical analysis of the ratio of the number of pathogens detected to the number of beds in 2017–2020
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Gram-negative bacteria comprised mainly Acinetobacter baumannii, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli and Burkholderia cepacia, with all except for Burkholderia cepacian showing a decreasing trend, Table 3 shows number and composition ratio of isolated strains over the last 5 years. Gram-positive bacteria comprised mostly Staphylococcus epidermidis, Staphylococcus aureus, Staphylococcus hominis and Enterococcus faecium, among which Staphylococcus was the most common, while Staphylococcus epidermidis and Staphylococcus aureus showed a decreasing trend.

Table 3 Number and composition ratio of isolated strains over the last 5 years
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3.2 Specimen Sources and Distribution of Pathogenic Bacteria in our Department

Over the last 5 years the source of specimens remained principally sputum, followed by blood, Fig. 3 shows sources of specimens from 2016 to 2020. Hospital-acquired infections in our department mainly originated from the respiratory tract, bloodstream and the urinary tract. The detection rate of sputum specimens revealed a downward trend from 79.69% in 2016 to 65.06% in 2020, in parallel with a decreasing incidence of ventilator-related infections. On the contrary, bloodstream infections increased year by year, from 5.63% in 2016 to 15.81% in 2020. Urinary tract infection showed a downward trend in general, significantly decreasing in 2019 and 2020, with the detection rate dropping to 0.72% and 2.16% respectively,it can be seen in Figs. 3 and 4 shows distribution of sputum specimens in 2016–2020.

Fig. 3
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Sources of specimens from 2016 to 2020

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Fig. 4
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Distribution of sputum specimens in 2016–2020. Dimension indicates time and shaded area is the composition ratio of sputum source specimens per year

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3.3 Drug Resistance of Main Pathogenic Bacteria to commonly prescribed Antibiotics

The main common pathogens in 2016–2020 were Acinetobacter baumannii, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, and Staphylococcus aureus.

3.4 Trends in Drug Resistance of Acinetobacter baumannii

Acinetobacter baumannii showed drug resistance to commonly used antibiotics, and a significantly increasing trend of resistance to levofloxacin, amikacin and ciprofloxacin (P < 0.05), from 64.20%, 20.90%, and 88.70% in 2017–2018 to 78.00%, 63.80%, and 97.60% respectively in 2019–2020. The difference between groups was statistically significant (P < 0.05), see in Table 4, changes in resistance of Acinetobacter baumannii from 2017 to 2020. The resistance rate of Acinetobacter baumannii to piperacillin likewise revealed a rising trend (P < 0.05), from 77.30 to 90.20%. The drug resistance rate to tobramycin and gentamicin not only increased year by year (P < 0.05) but was also at a high level.

Table 4 Changes in resistance of Acinetobacter baumannii from 2017 to 2020
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3.5 Changes in Drug Resistance of Staphylococcus aureus

Staphylococcus aureus has recently been sensitive to vancomycin, linezolid and nitrofurantoin, and its resistance to ciprofloxacin, levofloxacin and erythromycin has declined from 40.0%, 40.0% and 75.0% in 2017 to 19.0%, 19.0% and 57.1% in 2020, respectively. The difference between 2017–2018 and 2019–2020 was statistically significant (P < 0.05), changes in drug resistance of Staphylococcus aureus can be seen in Table 5.

Table 5 Changes in drug resistance of Staphylococcus aureus
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3.6 Number and Drug Resistance Rate of Common Multi-drug Resistant Bacteria

The trend changes of the common multi-drug resistant bacteria with high detection rate in our department were analyzed.

3.6.1 Penicillin-Resistant Escherichia coli

The number of detected penicillin-resistant Escherichia coli showed an increasing trend year on year, from 0 strains in 2016 to 50 strains in 2020. Likewise the drug resistance rate showed an increasing trend although there was no significant difference between the 2017–2018 group and the 2019–2020 group (P > 0.05),Changes in drug resistance of penicillin-resistant Escherichia coli. can be seen in Table 6.

Table 6 Changes in drug resistance of penicillin-resistant Escherichia coli
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3.6.2 Penicillin-resistant Klebsiella pneumoniae

The detection rate of penicillin-resistant Klebsiella pneumoniae over the past 5 years showed an increasing trend although drug resistance showed a decreasing trend with a significant difference between the 2019–2020 group and the 2017–2018 group (P < 0.05), changes in drug resistance of penicillin-resistant Klebsiella pneumoniae can be seen in Table 7.

Table 7 Changes in drug resistance of penicillin-resistant Klebsiella pneumoniae
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3.6.3 Penicillin-Resistant Acinetobacter baumannii

The number of detected strains of penicillin-resistant Acinetobacter baumannii increased from 0 strains in 2016 to 127 strains in 2020, while the difference between the two groups in resistance variation was not significant (P > 0.05), Table 8 shows Changes in resistance of penicillin-resistant Acinetobacter baumannii.

Table 8 Changes in resistance of penicillin-resistant Acinetobacter baumannii
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3.6.4 Penicillin-Resistant Pseudomonas aeruginosa

The number of resistant strains of penicillin-resistant Pseudomonas aeruginosa increased between 2017 and 2018, and decreased between 2019 and 2020, with a statistically significant difference between the two groups (P < 0.05), Table 9 shows changes in resistance of penicillin-resistant Pseudomonas aeruginosa.

Table 9 Changes in resistance of penicillin-resistant Pseudomonas aeruginosa
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3.6.5 Methicillin-Resistant Staphylococcus aureus (MRSA)

The detection rate of methicillin-resistant Staphylococcus aureus revealed no significant changed over the past 5 years although the drug resistance rate demonstrated an obvious decreasing trend during 2019–2020, Table 10 Changes in methicillin-resistant Staphylococcus aureus (MRSA) resistance.

Table 10 Changes in methicillin-resistant Staphylococcus aureus (MRSA) resistance
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4 Discussion

Although several countries and institutions have published guidelines for the design and layout of intensive care units, there is no conclusive evidence that they affect the incidence of nosocomial infections. In this study, we analyzed the distribution of pathogenic bacteria and their altered patterns of antibiotic resistance before and after the introduction of single-room units in our department, and their impact on hospital-acquired infections. The number of pathogenic bacteria in our department has been increasing over the past 5 years, with the majority being Gram-negative. This is similar to the national bacterial drug resistance surveillance data from 2020 and most studies [11, 12]. Among the Gram-negative bacteria isolated in the last 5 years, Acinetobacter baumannii, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, and Burkholderia cepacia onion were more common, slightly different from the bacterial detection in our hospital in 2017 [13] and unlike the study by Julio Alencar et al. [14]. The large number of departments in the hospital and variation in sites of infection, and types and complexity of disease would have affected the analysis. Another reason may be due to the special situation of our department, the poor health of patients, more invasive operations, and the need for prolonged artificial ventilation, all of which increase the chance of infection. This led to a more rapid spread of bacteria with mainly contact transmission, and therefore inconsistent detection of susceptible pathogens. The trend of drug resistance varies among pathogens with some such as Acinetobacter baumannii and Staphylococcus aureus more associated with the surrounding environment and thus more likely to be transmitted through contact with medical personnel [15,16,17,18]. With this in mind, we focused on the trends for drug resistance in these two pathogens. Unlike the results of the National Bacterial Resistance Surveillance Network, the detection rate of Acinetobacter baumannii decreased nationwide, and that of Escherichia coli and Enterobacter cloacae increased significantly. The sources of specimens were mainly sputum, blood, ascites fluid, and urine, roughly consistent with the results of surveillance in our hospital and hospitals in northern Anhui Province [13, 19]. However, in difference to the findings of Tian Li et al. [20]. The results of national bacterial drug resistance surveillance showed that the strains originated from sputum specimens (1,245,951 strains, accounting for 38.3%), urine specimens (667,681 strains, accounting for 20.5%) and blood specimens (295,868 strains, accounting for 9.1%).

Multi-drug resistant bacteria are a concern, especially multi-drug resistant gram-negative bacilli such as carbapenem-resistant Enterobacteriaceae (CRE), carbapenem-resistant Acinetobacter baumannii (CRAB), and carbapenem-resistant Pseudomonas aeruginosa (CRPA). The bacterial drug resistance surveillance network in Anhui Province revealed no multi-drug resistant bacteria in our department in 2016. This may have been due to poor testing or a lack of awareness of the need to test. Alternatively, the number of strains monitored may have been too few for a statistical reference value and so they were excluded from the statistics. The results of this study showed an increasing trend in the detection rate of CRO, except for a decrease in CRE. Similar to data of the National Drug Resistance Surveillance Network in 2021, the National Drug Resistance Surveillance Network showed that the resistance rate of Escherichia coli to carbapenems was still at a low level, while that of Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii to carbapenems was generally higher and on a slow upward trend. There were significant regional differences in the trend of multi-drug resistant bacteria, with a high proportion in Henan province and a low proportion in Tibet and Qinghai. The use of carbapenem antimicrobial drugs and the management of nosocomial infections vary from region to region. In addition, some regions still adopt open general ward management in the ICU that may affect the degree of hospital-acquired infections. Carbapenem-resistant strains of bacteria continue to appear and are on the rise, suggesting that the control of hospital-acquired infections and the rational use of antibiotics should be kept under review [14].

Of note, the detection rate of MRSA decreased from 93.3% in 2017 to 52.4% in 2020. The reason for its decrease between 2019 and 2020 may have been our implementation of a single-room management policy. The transmission of pathogenic bacteria and their resistance rates can be effectively prevented by improving single-room wards, enhancing awareness of infection prevention and control, and improving compliance with hand hygiene and infection control measures. Similar to other studies [21, 22], direct contact is the main mode of transmission of multi-drug resistant bacteria [23]. Transmission of MDROs in the ICU can be effectively controlled by proactive interventions, timely identification of patients infected with an MDRO, adoption of isolation measures, and removal of the source of infection.

A domestic study by Hu Xia et al. [24] concluded that single-room wards played only a partial role in the control of hospital-acquired infections. The study examined the catheter infection rate, CRAB, CRE, and CRPA infection rates before and after introduction of single-room management and revealed no statistical difference in the catheter-related infection rate and a statistically significant difference in the comparison of multi-drug-resistant bacteria. The study concluded that the prevention and control of hospital-acquired infections was the result of the combined application of several measures and not just single-room management. In contrast, we analyzed the pathogenic bacteria and their pattern of drug resistance over the last 5 years.

We considered a single room ward as the only independent factor to influence the infection rate of pathogenic bacteria since the improvements with single room ward management not only increased the size of the room but enabled each bed to have its own dedicated equipment and medical staff were more conscious of the importance of hand hygiene. All of these may have contributed to infection control. Similar to other previous studies it is difficult to unravel the cumulative effects of environmental and human factors.

Teltsch et al. [25] and Cepeda et al. [26] examined various factors. Teltsch et al. revealed 12 common, probable exogenous and endogenous organisms that were acquired at a reduced rate after the intervention using a statistical model to compare infection rates in two hospitals. After excluding other influencing factors, changing to a single room significantly reduced the rate of hospital acquired infection in the ICU. Conversely, Cepeda et al. examined rates of MRSA infection and concluded that isolating patients in single rooms was not beneficial. Nonetheless patients were isolated only after they were confirmed to be infected with MRSA, and hand hygiene practices were not changed. This may have concealed any single room benefit.

Unlike the study by Cepeda et al. [26], patients in our study were directly admitted to a single room. Similar to the studies by Teltsch et al. [25] and Levin et al. [27], the difference is that our study focused more on the passage of time and there was no movement of patients from a general purpose ward to a single room. The source of patients and the number of diseases before and after the change of ward management in our department were reasonably consistent,thus,the effects of patients had been avoided. Teltsch et al. compared two hospitals with different ward designs while Levin et al. altered the ward layout and prospectively observed infection in patients before and after admission to a single ward. Those admitted to a single ward acquired significantly fewer drug-resistant bacterial infections than those on a regular ward, with the improved single ward significantly reducing the acquisition of drug-resistant bacteria by 72%. This study also found that after introducing the single room ward model, the rate of infection of some pathogenic bacteria in patients decreased relative to that on the regular ward. In addition, the resistance of some drug-resistant bacteria decreased.

In our study, partial infection rate did not decrease pathogenic bacteria after improved ward management and the change in drug resistance was different, possibly due to environmental factors and compliance with good hand hygiene [28,29,30,31].Several studies have shown that enhanced control of the ward environment and compliance with good hand hygiene can help control infection [32,33,34], especially after the establishment of a single ward pattern. We conclude that establishment of a single room ward helps because transition of staff from one room to another serves as a reminder of the need for good hand hygiene [35,36,37], and also reduces environmental transmission of bacteria due to air pollution. Introduction of a single room ward directly or indirectly reduces the rate of pathogenic bacterial infection and drug resistance. Similarly, several studies [27, 38, 39] have shown that the use of a single ward reduces the risk of acquiring drug-resistant pathogens and that a single-room ward as an infection control strategy helps reduce cross-transmission of drug-resistant pathogens in the ICU [40]. For patients admitted to the ICU, especially those with multi-resistant bacteria, strict contact isolation in a single room should be instigated, as advised by guidelines.

There are limitations to this study. First, the scale of this study is relatively small. It compared data only for the two years before and after the changes, and did not examine or analyze the basic information of patients. This study mainly compared the changes in bacterial composition and drug resistance. The differences in disease types and proportion of hospitalized patients were not significant, and basic information about patients had less impact on the results. Second, the data in this paper showed that the detection rate of pathogenic bacteria increased after establishment of the single room ward, possibly due to previous poor monitoring and poor awareness of medical staff for the need to monitor. In addition, the study was retrospective and focused on a single room ward only. Similar analysis of bacterial infection and drug resistance patterns was not carried out for an open ward so no comparison could be made. Thus monitoring and culture data of some drug-resistant bacteria were not available prior to the introduction of a single room ward so results should be interpreted with caution. Finally, in addition to the use of a single-room isolation ward during the research period, other hospital-infection prevention and control measures were also changed. To further validate the findings of this study, a prospective study could be performed to further analyze the infection rate, infection prevention and control measures, microbiological inspection status, and detection rate before and after the opening of the single-room isolation wards, to confirm the findings.

5 Conclusions

The indicators showed a significant downward trend after the adoption of single room wards. A single-room ward directly or indirectly reduced the probability of cross-infection. Although many studies recommend the introduction of single room wards, there remain insufficient hospitals in China with such a policy with most still operating open wards. We encourage the establishment of single room wards in other hospitals to enable further more rigorous and scientific study.