Microbial resistance to antimicrobial agents (AMR) has been a major challenge. The main cause of AMR is the overuse and misuse of antimicrobial agents in healthcare settings and by the general public. The containment of AMR is an urgent priority, both in China and worldwide (
14). Monitoring AMR is the most effective means to provide useful information for prevention and help clinicians prescribe effective antibiotic therapy.
Our study showed that only the percentages of sputum/endotracheal aspirate specimens were higher in the ICUs than in the whole hospital. Moreover, the culture-positive rates of sputum/endotracheal aspirates in the ICUs were higher than those in the whole hospital. The reason may be that ICU-acquired pneumonia and ventilator-associated pneumonia (VAP) were the most common types of healthcare-associated infections in ICU patients, and ICU-acquired pneumonia and VAP are major causes of morbidity and mortality in ICU patients (
15,
16). It was similar to those from Tanzania (
17). Additionally, this study showed that most of the isolates were recovered from sputum/endotracheal aspirates from the whole hospital (40.4%) and ICUs (72.5%), similar to reports from CHINET surveillance in China (
18,
19) (40.0% in 2017 and 41.6% in 2016) for the whole hospital and in Iran (
20) (70.63%) for ICUs. The distributions of the other specimens with isolates were different in the ICUs and the whole hospital. The sources of isolates in the whole hospital were significantly different from those in the ICUs. Therefore, it was necessary to analyze the distribution and detection rate of specimens in different areas.
This study showed that the percentages of GPB and GNB in the whole hospital were similar to those reported by CHINET surveillance in China (
19) (GPB, 29.2% and GNB, 70.8%) and Greece (
21) (GPB, 31.8% and GNB, 68.2%) and different from those reported in China (
22) (GPB, 20.25% and GNB, 79.75%) and southern Ethiopia (
23) (GPB, 37.23% and GNB, 62.77%). In the ICUs, the percentages of bacteria were 18.4% for GPB and 81.6% for GNB, different from those reported in Poland (
24) (GPB, 21.6% and GNB, 71.6%) and similar to those reported in Saudi Arabia (
25) (GPB, 15.9% and GNB, 81.0%) and Greece (
21) (GPB, 18.5% and GNB, 81.5%). The percentage of GNB was significantly higher in the whole hospital than in the ICUs (P < 0.05). This study found that there were differences in the percentages of isolates between different cities, but we could still refer to the national data of CHINET surveillance in China.
Our results showed that the species of the five dominant bacteria were consistent with those reported in studies in other regions, including the CHINET for China (
5), Zhengzhou (China) (
6), Nanjing (China) (
26), Seoul (Korea) (
27), Somalia (
28), and Greece (
21), but the proportions of the five dominant bacteria were different. Therefore, it was necessary to analyze the proportions of bacteria in different areas. This study found that the detection rates of MRSA, ESBL-
E. coli, CRPA, CRAB, and XDRAB in the whole hospital were lower than those in the ICUs, similar to other reports from China (Wuhan) (
29); however, the detection rates of ESBL-
K. pneumoniae, CREC, CRKP, and XDRPA in the ICUs and the whole hospital were similar, while the detection rates of XDREC, XDRKP, and XDRSA in the ICUs were lower than those in the whole hospital. These results were different from reports in New Jersey (the USA) (
30). Besides, MRSA showed a decreasing trend in both the ICUs and the whole hospital, similar to that reported by CHINET surveillance (
5). The detection rates of XDRPA and XDRAB were similar to those reported by CHINET surveillance, but the rate of XDRKP was lower than that reported by CHINET surveillance (
5). Therefore, it is necessary to monitor the patterns of AMR in this area, and this study provides reference data for the prevention and control of super-resistant bacteria in this area.
The trends of most antimicrobial resistance levels among
E. coli and
K. pneumoniae were stable in the ICUs and the whole hospital. For
P. aeruginosa, a decrease in resistance with time was observed for amikacin, gentamicin, ciprofloxacin, and levofloxacin, and an increase in resistance was observed for ticarcillin/clavulanic acid, cefoperazone/sulbactam, cefepime, imipenem, and meropenem in both the ICUs and the whole hospital. For
A. baumannii, a decrease in resistance with time was observed for amikacin, gentamicin, tobramycin, piperacillin/tazobactam, ciprofloxacin, imipenem, and tigecycline in the ICUs, while an increase in resistance was observed for cefoperazone/sulbactam in both the ICUs and the whole hospital. The resistance rates of
S. aureus to all the antimicrobial agents showed decreasing trends, especially in the ICUs, similar to other reports (Wuhan) (
29).
The results of the present study showed that the resistance levels to carbapenems, β-lactam-containing agents, and tigecycline in
E. coli were higher than those in
K. pneumoniae; however,
E. coli and
K. pneumoniae maintained high sensitivity to all the agents. In this study, the resistance rates of
E. coli to all the antimicrobial agents in the whole hospital and the ICUs were higher than those reported in other areas, including by CHINET surveillance (
5) and in Nanjing (
26), Zhengzhou (
6), and Greece (
31). However, the resistance levels of
K. pneumoniae to most of the antimicrobial agents were lower than those reported in these areas. For
P. aeruginosa, we found that it was more sensitive to all the antimicrobial agents than
A. baumannii. However,
A. baumannii had a high sensitivity to only cefoperazone/sulbactam and tigecycline, while it had a high resistance rate to all the other antimicrobial agents.
In the whole hospital and ICUs, the resistance rates of
A. baumannii to ceftazidime, cefepime, imipenem, and meropenem were higher than those reported by CHINET surveillance (
5) and those in Zhengzhou (
6) and Kazakhstan (
32) but lower than those reported in Nanjing and Lebanon. However, in the whole hospital and ICUs, the resistance rates of
P. aeruginosa to all the antimicrobial agents were lower than those reported by CHINET surveillance (
5) and those in Zhengzhou (
6), Nanjing (
26), and Greece (
21). We also found that
P. aeruginosa was more sensitive to ceftazidime and cefepime than to imipenem and meropenem in our study. This may be related to the mechanism of carbapenem resistance caused by the deletion of outer membrane proteins and the overexpression of efflux pump genes in
P. aeruginosa. For
S. aureus, the resistance rate to most of the antimicrobial agents in the whole hospital was lower than that reported by CHINET surveillance (
5) and those in Zhengzhou (
6), Nanjing (
26), and North Korea (
27), but higher than that reported in Dongguan (
33). In the ICUs, the resistance rates of
S. aureus to most of the antimicrobial agents were lower in our study than those in Greece (
21) and higher than those in Kazakhstan (
32). The difference in resistance of these bacteria to different antibiotics may be related to the distribution of patients in the region and the management of antibiotic use.
The results of the present study showed that the susceptibility of
A. baumannii to tigecycline began in 2014, with resistance rates of 3.4% (hospital-wide) and 6.7% (ICUs). However, resistance to tigecycline showed a decreasing trend with time. The resistance level of
E. coli to tigecycline (< 0.05) has remained stable since 2015, but it was higher than those reported in Africa (0), North America (0), and South America (0) and lower than those reported in Asia (0.3%) and Europe (0.1%) (
34). The resistance levels of
K. pneumoniae to tigecycline showed an increasing trend with time, which was higher than those reported in Africa (0) and North America (0) but lower than those reported in Asia (1.3%), South America (0.9%), and Europe (0.7%) (
34). However, bacterial isolates were still highly sensitive to tigecycline in vitro in our study (susceptibility > 99%).
This study has two limitations. First, it was a single-center study. Since susceptibility rates vary among hospitals and units in different regions, the results may not be representative of and generalizable to other institutions, especially primary health care institutions. Second, incubation periods may vary according to the type of the pathogen or a patient’s underlying condition, and it was difficult to distinguish between cases of ICU-acquired infections and pre-existing colonization on ICU admission. Therefore, we will conduct a separate and more detailed study of cases of ICU-acquired infections and pre-existing colonization on ICU admission in future studies.
5.1. Conclusions
The distribution of clinical samples, the detection rate, and the sensitivity of clinical isolates varied with time and region. The susceptibility rates of E. coli and A. baumannii to antimicrobial agents were significantly higher than those in other areas. Besides, K. pneumoniae and P. aeruginosa had higher susceptibility to antimicrobial agents in our study than those reported in other regions, and the resistance of S. aureus to antimicrobial agents gradually decreased over time. Between the ICUs and the whole hospital, the resistance rates to antimicrobial agents were significantly different for A. baumannii and slightly different for E. coli, but there was no difference for K. pneumoniae, S. aureus, and P. aeruginosa. These data provide important useful information for the treatment and prevention of clinical infections.