Data were collected from 12,412 patients across 28 ACHs, comprising 39 acute care facilities throughout the Lombardy Region. Each hospital enrolled a median of 434 patients (IQR: 199–663). Participating facilities constituted 20% (39 out of 195) of all acute care facilities and accounted for 44% (18,620 out of 42,018) of acute care beds within the Region. Additionally, these facilities (5 small, 7 medium-sized, and 16 large hospitals) represented 50% (646,261 out of 1,288,198) of annual hospital admissions.
Patients’ characteristics
Out of 12,412 patients enrolled in the study, 6,465 (52.2%) were male, 5,930 (47.8%) were female while the sex of 7 patients was unspecified. The median age was 68 years (IQR: 48–79, minimum 0, maximum 103). 740 patients were younger than 2 years, as infants were also included in the study.
Most enrolled patients were admitted to Medicine (14.7%), General Surgery (6.8%), and Cardiology (6.1%) wards. Other specialized wards each accounted for less than 5% of admissions.
Based on the estimated clinical severity assessed using the McCabe Score, 67.2% of the enrolled patients had a non-fatal disease (expected survival > 5 years), 16.6% had an ultimately fatal disease (expected survival 1 to 5 years), 6.6% had a rapidly fatal disease (expected survival < 1 year), and in 9.6% of cases the McCabe Score was unknown or unregistered.
Of the enrolled patients, 34% (4,278) underwent surgery on the day of the study, and among them 2,783 (22%) underwent major surgery, and 1,495 (12%) underwent a minimally invasive surgery.
Use of invasive medical devices
4,548 (36.6%) patients had at least one invasive medical device (MD) in place (urinary catheter, central venous catheter, and/or intubation), specifically 3,468 (76.3%) had only one device, 766 (16.8%) had two, and 314 (6.9%) had three MDs.
The most used MD was the urinary catheter, 3,582 (29.1%) patients, followed by the central venous catheter (1,919, 15.5%) and intubation (441, 3.6%).
The number and type of MDs varied by care area, with the highest utilization observed in the intensive care units (71.9% of patients using at least one device), followed by medical (43.3%) and surgical (39.2%) wards.
Prevalence of HAIs
Healthcare-associated infections were detected in 1,259 patients, resulting in a prevalence of 10.1% (95% CI 9.6–10.7%). In total, 1,385 HAIs were reported, with 1.1 HAIs per patient on average.
Among the participating ACHs, the prevalence of HAIs varied significantly, ranging from 1.4% (95% CI 0.2-5.0%) to 28.2% (95% CI 18.6–39.5%).
Specifically, 260 (2.1%) patients had at least one HAI upon hospital admission, while 998 (8.0%) patients developed the HAI during their stay in the hospital. Excluding hospital-acquired SARS-CoV-2 infections from the analysis, the overall prevalence of HAIs was 8.4% (95% CI 7.9–8.9%), affecting 1,045 patients. Of these, 795 (6.4%) developed at least one HAI during their hospitalization and 247 (2.0%) had an HAI present upon admission.
As shown in Table 1, the prevalence of HAIs was significantly higher in men, in patients aged over 64 years, in those with severe McCabe score or having undergone major surgery. When stratifying by hospital size, a higher prevalence of HAIs was observed in small and large hospitals compared to medium-sized hospitals. Further stratification by healthcare areas revealed an elevated prevalence within intensive care units (ICUs), excluding long-term care due to very limited data. Additionally, the presence of invasive medical devices was linked to a higher HAI prevalence, reaching 31.3% among intubated patients.
Among the 1,385 HAIs reported, the most common types were bloodstream infections (BSI, 262 cases, 18.9%), followed by urinary tract infections (UTI, 237 cases, 17.1%), SARS-CoV-2 infections (236 cases, 17.0%), pneumonia and lower respiratory tract infections (PN-LRTI, 231 cases, 16.7%), surgical site infections (SSI, 152 cases, 11.0%), and gastrointestinal tract infections (GI, 103 cases, 7.4%). See Table 2 for complete results.
Isolated microorganisms
Laboratory detection was achieved for 887 HAIs (64% of total HAIs), with 1,039 microorganisms isolated (up to 2 microorganisms per HAI). A total of 71 different pathogens were identified. The most frequently isolated microorganisms included SARS-CoV-2 (145, 14%), E. coli (128, 12.3%), K. pneumoniae (108, 10.4%), S. aureus (94, 9%), and P. aeruginosa (77, 7.4%). Figure 1 shows the most frequently isolated microorganisms per HAI type.
Regarding antibiotic resistance, S. aureus was resistant to oxacillin in 35.3% (n = 30) of cases; K. pneumoniae was resistant to third generation cephalosporins in 53.4% (n = 55) of cases and in 21.8% (n = 22) of cases to carbapenems; P. aeruginosa and A. baumannii were respectively resistant to carbapenems in 24.2% (n = 16) and 89% (n = 8) of cases.
There were also 4 confirmed cases (0.6%) and 1 possible case (0.1%) of pan-drug-resistant microorganisms, meaning they were resistant to all tested antibiotics. These cases included two A. baumannii, one K. pneumoniae, and one P. aeruginosa, with one possible case of K. pneumoniae.
Distribution of HAIs per site and most frequently isolated microorganisms
Antimicrobial use
5,225 patients (42.1%, 95% CI 41.3–43.0%) were on systemic antimicrobial therapy. The total number of antimicrobial therapies was 6,884, with each patient receiving 1.32 medications on average. In Table 3, we provide data regarding antimicrobial use stratified by area of care (top 5), most frequently used molecule (top 5), antimicrobial class (top 5), AWaRe classification and clinical indication. The prevalence of patients on therapy varied significantly across the areas, with the highest prevalence registered in ICUs. The most used antimicrobials were Piperacillin associated with enzyme inhibitors and Ceftriaxone. According to the WHO AWaRe classification [21, 22], the most used antibiotics belonged to the Watch class, followed by the Access class and the Reserve class; for 300 antimicrobials the AWaRe classification was not applicable (antifungal and antituberculosis drugs). Antimicrobials were mostly used to treat community-acquired infections followed by HAIs.
Upon further analysis, antibiotics used for treating infections (including community-acquired, healthcare-associated, and long-term-care-associated) mostly belonged to the Watch class (2,906, 71.8%), followed by the Access class (792, 19.6%) and the Reserve class (349, 8.6%).
Antimicrobials used to treat infections were mostly used to treat pneumonia (1,301, 31.4%), followed by bacteremia with laboratory confirmation (370, 8.9%), lower-urinary-tract infections (362, 8.7%) and intra-abdominal sepsis (332, 8.0%).
Antibiotics used for prophylaxis mostly belonged to the Access class (1,267, 67.4%), followed by the Watch class (595, 31.6%) and the Reserve class (18, 1.0%).
Antimicrobials used for surgical prophylaxis lasting more than one day (43% of all surgical prophylaxis), compared to prophylaxis lasting one day or less belonged significantly more to the Watch class (32.3% vs. 14.9%, p < 0.001) and significantly less to the Access class (66.1% vs. 84.8%, p < 0.001). Figure 2 summarize the distribution of the AWaRe classification for each antibiotic indication.
Distribution of the AWaRe classification for each antibiotic indication
Legend: CI: community-acquired infections; LI: long-term acquired infections; HI: Healthcare-associated infections; SP1: Surgical prophylaxis (single dose); SP2: Surgical prophylaxis (1 day); SP3: Surgical prophylaxis (> 1 day); MP: Medical prophylaxis
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