Changes of Klebsiella pneumoniae infection and carbapenem resistance in ICU elderly infected patients before and after the COVID-19 pandemic in Zhengzhou, China

Recent articles suggested that Streptococcus pneumonia (S. pneumoniae), Haemophilus influenzae (H. influenzae) and Moraxella catarrhalis (M. catarrhalis) infections among children in Zhengzhou, China showed a decreasing trend during the COVID-19 pandemic.^{,  ,}  Previous studies also reported changes in carbapenemase-producing Enterobacteriaceae and extended-spectrum beta-lactamase (ESBL) E. coli infections during the COVID-19 pandemic.^, However, Klebsiella pneumoniae (K. pneumoniae), especially carbapenem-resistance K. pneumonia (CRKP) infection, is the main cause of mortality among elderly in the ICU, and its’ impact during the COVID-19 pandemic has not been reported.

K. pneumoniae is a Gram-negative pathogen associated with pneumonia, urinary tract infection, sepsis, wound infection, and meningitis. K. pneumoniae naturally colonizes the nasopharyngeal and gastrointestinal tracts after infection. However, nasopharyngeal colonization was relatively low (maximum of 15%) compared with that of the gut (approximately 20%). K. pneumoniae is usually susceptible to carbapenems, but more than 40% of clinical K. pneumoniae isolates collected from 30 medical centers in China were identified as CRKP in 2017. CRKP has emerged as a major worldwide human health threat, as CRKP infections are associated with high mortality and morbidity. Moreover, the morbidity and mortality rates for CRKP-infected patients in the ICU are much higher than the non-ICU patients. A previous study showed that nearly half of all K. pneumonia (45.7%) infections occurred in the elderly, and suggested that age is also an independent risk factor for CRKP, which may result from the decreased immune function of elderly patients. Therefore, the prevention and control of K. pneumonia and CRKP infections in elderly ICU patients is a major public health concern worldwide.

In this study, we assessed the positive rate, age, basic information and epidemic trend of K. pneumonia and CRKP infections in ICU elderly infected patients before and after the COVID-19 pandemic to provide a reference for hospital infection control and treatment of CRKP. The number of positive cases of K. pneumonia and CRKP infections among elderly (defined as more than 60 years old), in the stratified age groups of 60–70 years, 70–80 years and more than 80 years, were examined between January 1, 2018, and December 31, 2021, at the First Affiliated hospital of Zhengzhou University according to laboratory surveillance. The number of elderly with K. pneumonia and CRKP infections increased from 2018 to 2019, but showed a steady decline after the outbreak of COVID-19 in Zhengzhou, China. Additionally, K. pneumonia and CRKP infections showed an obvious seasonality from 2018 to 2019 before the COVID-19 pandemic, with the number of positive cases increasing in winter, but no seasonality was observed in 2020–2021 after the COVID-19 pandemic (Fig. 1A and 1C). Furthermore, the percentage of positive cases (positive cases/total cases) with K. pneumonia and CRKP infections showed an obvious seasonality from 2018 to 2019 before the pandemic, in which the percentage of positive cases was higher in winter, but the seasonality was inconspicuous from 2020 to 2021 after the COVID-19 pandemic (Fig. 1B and 1D). Interestingly, the number of positive cases of K. pneumonia and CRKP infections in 2021 was slightly lower than in 2020, which may be associated with the preventive and control measures of COVID-19 that resulted in a significant reduction in the number of elderly going to the hospital. Furthermore, both the number of positive cases of K. pneumonia and CRKP infections, as well as the percentage of positive cases of K. pneumonia infections rapidly increased owing to the COVID-19 outbreak in Zhengzhou from February to June 2021 (Fig. 1A–C). The percentage of positive cases of CRKP infections rapidly increased due to the COVID-19 outbreak in Zhengzhou between July and August 2021,and the large population mobility and increased transmissibility of COVID-19 may cause it's increased during the Chinese Spring Festival (Fig. 1D). Taken together, these results suggested that the COVID-19 pandemic could influence the infection status of K. pneumonia and CRKP infections.

Additionally, the number of elderly infected with K. pneumonia and CRKP in the ICU was the lowest in the >80 years age group, who only accounted for 23.3% and 24.5% of the total number of infected elderly ICU patients from 2018 to 2021, and was similar between the 60–70 years age group and the 70–80 years age group (Fig. 2A and 2C). However, among all age groups, the highest proportion of K. pneumonia and CRKP infections in the >80 years age group was 35.3% and 84%, respectively. Importantly, the number of infections showed a decreasing trend before and after the COVID-19 pandemic, particularly in the >80 years age group, but the percentage of positive cases showed an increasing trend in the elderly, especially, in the >80 years age group. This may like a report showed that although the number of positive cases with infections (i.e., the numerator) decreased, the extent of the decrease in the total number of tested patients (i.e., the denominator) was larger. Specifically, the decrease in the total number of tested patients would be because the increase in the number of new polymerase chain reaction-positive COVID-19 patients and hospitalized COVID-19 patients caused a decrease in the number of hospital admissions due to other diseases and increased the testing threshold due to the risk of transmission of COVID-19. Although the COVID-19 pandemic restrictions are completely lifted in some Chinese cities, the global pandemic continues and its prevention and control remains inadequate. Therefore, the long-term prevalence of K. pneumonia and CRKP infections in elderly ICU patients should be closely monitored. Moreover, ICU elderly infected patients, especially those >80 years old, should be aware of the risk of K. pneumoniae and CRKP infections.

In summary, this study suggested that K. pneumoniae and CRKP infections in ICU elderly infected patients had decreased during the COVID-19 pandemic. Monitoring epidemiological trends is important for preventing K. pneumoniae and CRKP infections in ICU elderly infected patients who are more than 80 years old.