Healthcare-associated infection (HAI) impacts care and costs, and is one of significant causes of morbidity and mortality while in hospital. The pediatric intensive care unit (PICU) is the department treating high-risk pediatric patients in the hospital. A variety of causes could contribute to the increased risk of HAI in PICU, including the intrinsic factors such as young age, low nutritional status, immature immune system, and extrinsic factors such as the presence of multi-resistant bacteria in the environment, numerous invasive operations and so on (1). A recent study in developing country suggested that there were 27.5 and 33.0 HAIs per 1,000 patient days in PICU, which was significantly higher than that in the non-ICU setting, with 6.8 HAIs per 1,000 patient days in both 2013 and 2014 (2). HAI is serious and important in PICU, and effective surveillance will allow the development and evaluation of targeted interventions to improve care of patients.

Congenital heart disease (CHD) is one of the most common birth defects, which seriously threatens the health and life of patients. Long term left-to-right shunt in the heart will result in increased pulmonary blood flow or pulmonary vascular resistance, leading to pulmonary arterial hypertension (PAH). World symposium on Pulmonary Hypertension classified CHD-PAH into the first category (3), which has been proven to be closely related to the impairment in functional class, quality of life, and survival. It was reported that the overall cumulative incidence of PAH in CHD was 5%–10% (4), and the 1, 5 and 10 year mortality in CHD-PAH was 24%, 44% and 52% respectively (5). As well known, most congenital heart diseases require surgical correction. Cardiac surgery, especially cardiopulmonary bypass, could worsen damage to the lungs and other systems, making patients more susceptible to infections. Previous literature has found that nearly 40.0% CHD children in hospital were tested as positive by sputum culture, predominantly induced by Gram-positive bacteria susceptible to cephalosporins and vancomycin (6). However, there are few studies on various types and risk of HAI in patients with CHD-PAH.

In the present study, we intend to analyze clinical characteristics of all patients in a single PICU from a tertiary general hospital in China, and provide a detailed description of HAI in children with CHD-PAH.

Compared to adult patients, organs in pediatric patients are not fully developed. Immature immune system, couple with underlying diseases, could lead to weak resistance to external pathogens. Hospital and even ICU setting is a place where various pathogens accumulate (9, 10). In addition with a mass of invasive operations such as puncture and intubation, pediatric patients are susceptible to HAI. The results showed that per-case infection rate of HAI in PICU from 2018 to 2021 was 1.38%, and the per-thousand-day infection rate was 2.99. Previous studies reported the incidence of HAI was almost over ten percent in developing countries (1, 11–13). This significant progress attributed mostly to the thorough and comprehensive surveillance management of HAI in our single center. The three-level management mode was adopted for HAI prevention and control, including hospital's HAI management committee, professional department of HAI, and side-bar HAI team in clinical department. Each patient follows a different specific regimen for HAI, executed by professional HAI staff, nurses and clinicians together.

The proportion of device-related infections was not consistent across hospitals. Hatachi and his colleagues found that CAUTI was the leading one (14), while another study in Turkey reported that the most commonly observed HAI was bloodstream infection (15). Different from above two researches, we found that the main site of nosocomial infection was lower respiratory tract, and VAP was the most likely to appear, accounting for 46.29%. It was probably because that most patients in our PICU were postoperative, who needed the support of mechanical ventilation. Similarly, pathogens will change greatly because of different hospitals in different regions. Our study reported that Klebsiella pneumoniae and Enterococcus faecium were the most frequently isolated microorganism, which provided a basis for the selection of antibiotics in early period.

Our study was the first one focusing on HAI in CHD-PAH. We found that the per-thousand-day infection rate of HAI in patients CHD-PAH was significantly higher than that in patients without CHD-PAH. PAH is a fatal complication of CHD, characterized by progressively increased pulmonary vascular resistance and pulmonary artery pressure (16). Excessive pulmonary congestion makes the lungs more susceptible to bacterial attack (17). Surgery is the main treatment method for children with CHD. After undergoing cardiopulmonary bypass, systemic immune system could further deteriorate (18). All these factors determine higher incidence of HAI in patients with CHD-PAH. On the other hand, local inflammatory reaction in the lung could induce spasm and contraction of pulmonary arterioles, and then cause the increase of pulmonary circulation resistance, aggravating pulmonary hypertension (19). Therefore, it's usually thought that the presence of HAI in CHD-PAH is closely associated with poor prognosis. In the present study, we also explore the difference of clinical characteristics in CHD-PAH. In our opinion, more attention should be paid to the problem of central venous catheterization. Aiming at its clinical features, effective measures should be taken to strengthen the prevention and control of CLABSI. In order to minimize the occurrence of HAI, the following measures were recommended for reference according to our experience: minimize the indwelling time, strengthen the training of clinical medical staff, be proficient in catheterization and maintenance techniques, strictly observe hand hygiene and aseptic technical operation, adopt the maximum aseptic barrier, regularly evaluate the necessity of catheter indwelling, remove any unnecessary vascular catheters as early as possible, and so on.

Some limitations still existed in the present study. First, the effect of HAI on the clinical outcomes of patients with CHD-PAH in PICU was not considered. Second, more factors can be future included to explore the risk factors of HAI in patients with CHD-PAH, as well as the effective measures to prevent HAI. Third, since the pandemic of COVID-19, both the management strategies and clinical characteristics of HAI have changed a lot (20), which was neglected in our research.

In summary, HAIs are easy to occur in PICU, especially in patients with CHD-PAH. G-bacteria is the predominant pathogen, which requires reasonable selection of antibiotics and strict aseptic operation. To reduce unnecessary invasive procedures will be helpful for the decreased incidence of postoperative HAI in children with CHD-PAH. Our study comprehensively describes the surveillance data of HAI in PICU from a tertiary hospital in western China, and firstly focuses on the subpopulation with CHD-PAH, which provides evidence for clinical prevention and control.