Bacterial bloodstream infections (BSIs) cause high morbidity and mortality worldwide in humans, but the pathogenic spectrum varies from region to region. Long-term monitoring of the pathogenic spectrum and changes in bacterial antibiotic resistance is hugely important for effective clinical therapy and infection control. This study examined the data for BSIs in Tongji Hospital, one of the largest teaching hospitals in China, in an attempt to gain better understanding of bacterial antibiotic resistance in China, focusing on central China. Data from Tongji Hospital for a 20-year period (1998–2017) were used for a retrospective analysis to understand the pathogenic spectrum of BSIs and the changes occurring in antimicrobial resistance in central China. The disk diffusion and E test methods were used for antimicrobial susceptibility testing according to Clinical & Laboratory Standards Institute methodologies, and the data were analyzed by WHONET 5.6 software. The isolated pathogens mainly came from hospitalized patients not treated in intensive care units (ICUs), and accounted for 81.5% of the total (9130/11200). The most common Gram-negative and Gram-positive bacterial BSI-causing pathogens were Escherichia coli and Staphylococcus aureus, respectively. The detection rate for methicillin-resistant S. aureus (MRSA) in the hospitalized non-ICU patients increased from 8.4% in 1998–2002 to 63% in 2013–2017, while the detection rate for carbapenem-resistant (CR) Klebsiella pneumoniae was below 5% in 1998–2012 but increased to 34.9% in 2013–2017. In contrast, worryingly, the detection rate for CR K. pneumoniae in ICU patients increased from 0% in 2013 to 75% in 2016. E. coli displayed the highest sensitivity rates to imipenem, meropenem and amikacin, all of which were > 90%, followed by cefoxitin at > 80%, and cefoperazone/sulbactam at > 70%. K. pneumoniae isolates were most sensitive to imipenem, meropenem and amikacin antibiotics, with sensitivity rates exceeding 60%. S. aureus isolates were most sensitive to vancomycin, teicoplanin and trimethoprim/sulfamethoxazole, with sensitivity rates exceeding 90%. BSIs caused by CR K. pneumoniae clearly posed a severe challenge to infection control and treatment of ICU and non-ICU patients in this retrospective study, while MRSA was an issue for non-ICU patients.

Data on the pathogens responsible for nosocomial bloodstream infection (BSI) and their antimicrobial resistance (AMR) in Hubei province are limited. This study was conducted to determine the major pathogens causing BSI and to characterize their AMR. Data from the China Antimicrobial Resistance Surveillance System (CARSS) from 2014 to 2016 were analyzed retrospectively. Escherichia coli, Staphylococcus aureus and Klebsiella pneumoniae were the most common pathogens responsible for nosocomial BSI. Individuals aged 0–5 years and ≥ 40 years old were the major demographics at risk of infection by E. coli, K. pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii and Enterobacter cloacae, while individuals aged 0–5 years were the major demographic at risk of infection by S. aureus, Enterococcus faecalis, E. faecium, Streptococcus pneumoniae and Stenotrophomonas maltophilia. The frequencies of E. coli and K. pneumoniae isolates resistant to cefotaxime were 59.1% and 24.3%, respectively, and the frequencies of resistant isolates to ceftazidime were 42.9% and 27.2%, respectively. From 2014 to 2016, the frequency of extended-spectrum β-lactamase (ESBL)-positive E. coli declined from 29.07 to 24.5%, and the frequency of ESBL-positive K. pneumoniae declined from 18.64 to 12.33%. The frequency of carbapenem-resistant (CR) E. coli was below 0.5%, but 1–10% of K. pneumoniae isolates were CR. The emergence of methicillin-resistant S. aureus and the expansion of ESBL and fluoroquinolone resistance among Gram-negative Enterobacteriaceae increased AMR severity. Carbapenemase-producing K. pneumoniae isolates responsible for nosocomial BSI increased year over year and effective infection control measures should be taken to prevent them from spreading.

Background: Lower respiratory tract infection (LRIs) is very common both in terms of community-acquired infection and hospital-acquired infection. Sputum and bronchoalveolar lavage fluid (BALF) are the most important specimens obtained from patients with LRI. The choice of antibiotic with which to treat LRI usually depends on the antimicrobial sensitivity of bacteria isolated from sputum and BALF. However, differences in the antimicrobial sensitivity of pathogens isolated from sputum and BALF have not been evaluated. Methods: A retrospective study was conducted to analyze the differences between sputum and BALF samples in terms of pathogen isolation and antimicrobial sensitivity in hospitalized patients with LRI. Results: Between 2013 and 2015, quality evaluation of sputum samples was not conducted before performing sputum culture; however, between 2016 and 2018, quality evaluation of sputum samples was conducted first, and only quality-assured samples were cultured. The numbers of sputum and BALF in 2013–2015 were 15,549 and 1671, while those in 2016–2018 were 12,055 and 3735, respectively. The results of pathogen culture showed that Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus, Hemophilus influenzae, Escherichia coli, Stenotrophomonas maltophilia, and Streptococcus pneumoniae were in the top ten pathogens isolated from sputum and BALF. An antimicrobial susceptibility test showed that the susceptibility of BALF isolates to most antibiotics was higher compared with the susceptibility of sputum isolates, especially after quality control of sputum samples (2016–2018). Conclusions: Our findings suggest that caution is needed in making therapeutic choices for patients with LRI when using antimicrobial sensitivity results from sputum isolates as opposed to BALF isolates.

Purpose: Bloodstream infections (BSIs) are a common consequence of infectious diseases and cause high morbidity and mortality. Appropriate antibiotic use is critical for patients’ treatment and prognosis. Long-term monitoring and analysis of antimicrobial resistance are important in guiding physicians to choose appropriate antibiotics and understand the changes in antimicrobial resistance and infection control. Here, we report a retrospective study on the trends of antimicrobial resistance in the common BSI-associated pathogens. Methods: The identification of strains and antimicrobial susceptibility tests were performed in each anticipating hospital independently. Data from the Hubei Province Antimicrobial Resistance Surveillance System (HBARSS) from 1998 to 2017 were retrospectively analyzed using WHONET 5.6 software. Results: Data from HBARSS (1998– 2017) revealed that 40,518 Gram-positive bacteria and 26,568 Gram-negative bacteria caused BSIs, the most common of which were Staphylococcus aureus and Escherichia coli. Salmonella typhi was a predominant BSI-associated pathogen in 1998– 2003. Antimicrobial susceptibility data showed that the resistance rates of E. coli and Klebsiella pneumoniae to cefotaxime were significantly higher than those to ceftazidime. The proportion of strains of special antimicrobial resistance phenotypes including difficult-to-treat resistance (DTR), carbapenem-resistant (CR), extended-spectrum cephalosporin resistant (ECR) and fluoroquinolone resistant (FQR) in E. coli was 0.18%, 0.26%, 13.95%, 22.78% while in K. pneumoniae was 11.95%, 14.00%, 31.91% and 11.40%, respectively. In 2013– 2017, K. pneumoniae showed resistance levels reaching 15.8% and 17.5% to imipenem and meropenem, respectively, and Acinetobacter baumannii showed high resistance rates ranging from 60 to 80% to common antibiotics. The detection rate of Salmonella typhi resistance to third-generation cephalosporins and fluoroquinolones was less than 5%. Control of methicillin-resistant Staphylococcus aureus (MRSA) remains a major challenge, and in 2009– 2017, the MRSA detection rate was 40– 50%. Conclusion: Prevalence of CR K. pneumoniae has increased significantly in recent years. Resistance rates of A. baumannii to common antimicrobial agents have increased exponentially, reaching high levels. MRSA remains a challenge to control. For K. pneumoniae, DTR, CR, ECR and FQR were antimicrobial resistance phenotypes that could not be ignored while for E. coli DTR and CR were rare antimicrobial resistance phenotypes. CR K. pneumoniae, A. baumannii and MRSA present major challenges for controlling BSIs.

Carbapenem-resistant Salmonella has recently aroused increasing attention. In this study, a total of four sequence type 36 Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) isolates were consecutively isolated from an 11-month-old female patient with a gastrointestinal infection, of which one was sensitive to carbapenems and three were resistant to carbapenems. Via antibiotic susceptibility testing, a carbapenemases screening test, plasmid conjugation experiments, Illumina short-reads, and PacBio HiFi sequencing, we found that all four S. Typhimurium isolates contained a bla_CTX-M-14-positive IncI1 plasmid. One carbapenem-sensitive S. Typhimurium isolate then obtained an IncHI2 plasmid carrying bla_NDM-1 and an IncP plasmid without any resistance genes during the disease progression. The bla_NDM-1 gene was located on a new 30 kb multiple drug resistance region, which is flanked by IS26 and TnAs2, respectively. In addition, the ST_F0903R isolate contained eight tandem copies of the ISCR1 unit (ISCR1-dsbD-trpF-ble-bla_NDM-1-ISAba125Δ1), but an increase in MICs to carbapenems was not observed. Our work further provided evidence of the rapid spread and amplification of bla_NDM-1 through plasmid. Prompting the recognition of carbapenem-resistant Enterobacterales and the initiation of appropriate infection control measures are essential to avoid the spread of these organisms.

Interpreting the results of metagenomic next-generation sequencing (mNGS) presents a significant challenge in both clinical and laboratory contexts. A retrospective analysis was conducted to validate mNGS findings, with a particular emphasis on Mycobacterium tuberculosis, Mycoplasma pneumoniae, and Pneumocystis jirovecii as representative pathogens, examined from both clinical and laboratory perspectives. Based on a comprehensive clinical analysis, the mNGS demonstrated detection accuracies for M. tuberculosis, M. pneumoniae, and P. jirovecii of 87.0% (60 out of 69; 95% confidence interval [CI], 77.04%–92.99%), 97.6% (81 out of 83; 95% CI, 91.63%–99.34%), and 78.9% (45 out of 57; 95% CI, 66.72%–87.53%), respectively. Conversely, when incorporating laboratory confirmation from a variety of detection methodologies, the accuracy rates for mNGS in identifying M. tuberculosis, M. pneumoniae, and P. jirovecii were 92.7% (51 out of 55; 95% CI, 82.74%–97.14%), 82.3% (51 out of 62; 95% CI, 70.96%–89.80%), and 83.9% (26 out of 31; 95% CI, 67.36%–92.91%), respectively. Additionally, our analysis revealed no statistically significant difference in read counts and relative abundances between mNGS results deemed clinically as false positives and those considered true positives (P < 0.05). In contemporary clinical practice, the detection of positive results from mNGS is notably high from both laboratory and clinical standpoints. Nonetheless, the interpretation of results with low read counts presents significant challenges for both clinical and laboratory environments under current conditions.