Comparison and evaluation of neutralization of clinically frequently used antimicrobial agents using three different culture media in simulated blood cultures.

The performance of BACT/ALERT FA/FN Plus (France) blood culture containing a novel resin, DL (China) blood culture containing common resin, and adsorbent-free REDOX (USA) blood culture relying on dilution for antimicrobial neutralization at %peak serum concentration was evaluated by measuring the recovery of organisms and time to detection (TTD) in nine simulated microorganism-antimicrobial combination blood cultures. Significant differences were observed in the recovery rates among the aerobic media: 87.5% for BACT/ALERT media, 42.9% for DL media, and 12.5% for REDOX media. In contrast, no statistical difference was found in the TTD between FA Plus media and DL aerobic media. For the anaerobic media, the recovery rates were 91.4% for BACT/ALERT media, 2.9% for DL media, and 14.3% for REDOX media, with significant differences only between BACT/ALERT FN Plus media and the others. Among the seven main antimicrobial categories, only BACT/ALERT FA/FN Plus culture media demonstrated high recovery of microorganisms, with the exception of carbapenems. The DL culture media exhibited a relatively high recovery rate of microorganisms in the presence of piperacillin/tazobactam, levofloxacin, and gentamicin, but only in aerobic conditions. Conversely, REDOX media displayed microorganism recovery solely in the presence of gentamicin. BACT/ALERT FA/FN Plus culture media with novel resin showed absolute advantages over DL and REDOX culture media and can, therefore, be selectively applied in clinical settings when antimicrobials are used prior to blood collection. DL culture media, containing common resin, outperformed adsorbent-free dilution-based REDOX culture media, making it a viable backup option. There is a need to focus on improving the neutralization of carbapenems with current inefficiency in all three medias. IMPORTANCE: We present a study on performance comparison of three different commercial culture media for neutralization of antibiotic effects in simulated blood cultures. BACT/ALERT (FA Plus and FN Plus) culture media with novel resin showed absolute advantages over DL and REDOX culture media at %PSL concentration of antimicrobials.

Analysis and application of volatile metabolic profiles of Escherichia coli: a preliminary GC-IMS-based study.

Nosocomial infections caused by Escherichia coli (E. coli) may pose serious risks to patients, and early identification of pathogenic bacteria and drug sensitivity results can improve patient prognosis. In this study, we clarified the composition and relative content of volatile organic compounds (VOCs) generated by E. coli in tryptic soy broth (TSB) using gas chromatography-ion mobility spectrometry (GC-IMS). We explored whether imipenem (IPM) could be utilized to differentiate between carbapenem-sensitive E. coli (CSEC) and carbapenem-resistant E. coli (CREC). The results revealed that 36 VOCs (alcohols, aldehydes, acids, esters, ketones, pyrazines, heterocyclic compounds, and unknown compounds) were detected using GC-IMS. Besides, the results indicated that changes in the relative content of VOCs as well as changes in the signal intensity of fingerprints were able to assess the growth state of bacteria during bacterial growth and help identify E. coli. Lastly, under selective pressure of IPM, volatile fingerprints of E. coli could be employed as a model to distinguish CSEC from CREC strains.

Gas Chromatography-Ion Mobility Spectrometry Reveals Acetoin as a Biomarker for Carbapenemase-Producing Klebsiella pneumoniae.

BACKGROUND This study aimed to detect the volatile organic compound (VOC), 3-hydroxy-2-butanone (acetoin) using gas chromatography-ion mobility spectrometry (GC-IMS) in antimicrobial-resistant Klebsiella pneumoniae (K. pneumoniae) carbapenemase (KPC)-producing bacteria. MATERIAL AND METHODS Using stromal fluid of blood culture bottles (BacT/ALERT® SA) as the medium, 3-hydroxy-2-butanone (acetoin) released by K. pneumoniae during growth was detected using GC-IMS. The impact of imipenem (IPM) and carbapenemase inhibitors [avibactam sodium or pyridine-2,6-dicarboxylic acid (DPA)] on the emission of 3-hydroxy-2-butanone (acetoin) from various carbapenemase-producing K. pneumoniae was further investigated. Subsequently, VOCal software was used to generate a pseudo-3D plot of 3-hydroxy-2-butanone (acetoin), and the relative peak volumes were exported for data analysis. Standard strains served as references, and the findings were validated with clinical isolates. RESULTS The pattern of temporal changes in the 3-hydroxy-2-butanone (acetoin) release from K. pneumoniae in the absence of IPM was consistent with the growth curve. After the IPM addition, carbapenemase-positive strains released significantly higher contents of 3-hydroxy-2-butanone (acetoin) than carbapenemase-negative strains at the late exponential growth phase (T2). Notably, adding avibactam sodium significantly decreased the 3-hydroxy-2-butanone (acetoin) content released from the class A carbapenemase-producing strains as compared to the absence of the carbapenemase inhibitor. Conversely, adding DPA significantly decreased the 3-hydroxy-2-butanone (acetoin) content released from the class B carbapenemase-producing strains (both standard and clinical strains, all P<0.05). CONCLUSIONS This study demonstrated the potential of 3-hydroxy-2-butanone (acetoin) as a VOC biomarker for detecting carbapenemase-producing K. pneumoniae, as revealed by GC-IMS analysis.

Gynecologic infection rates after ablation treatment for cervical intraepithelial neoplasia grade 2 and higher (CIN2+): Secondary analysis of a non-inferiority randomized trial.

Although concerns have been raised regarding potential infection and morbidity in women undergoing ablation treatment for cervical precancer in low- and middle-income countries (LMIC), there is extremely limited data to substantiate this claim. This is a secondary analysis of a randomized non-inferiority trial (id: NCT03084081) that compares the efficacy and safety of three ablation treatments for biopsy-confirmed cervical intraepithelial neoplasia grade 2 or higher (CIN2+): CO2 gas-based cryotherapy, non-gas cryotherapy, and thermal ablation (TA). Here, we present findings regarding the incidence of sexually transmitted infections (STI) and vaginitis post-treatment. Samples were collected at enrollment and again at 6 weeks post-treatment and assessed for STIs (Chlamydia trachomatis (CT), Neisseria gonorrhea (NG), and Trichomonas vaginalis (TV)) and vaginitis (Bacterial vaginosis (BV) and/or Candida albicans (Candida)). This analysis reflects 864 women with baseline and 6-week follow-up data. None of the ablative treatments put women at increased risk for STIs (CT, NG, TV) or vaginitis (BV, Candida). While most women adhered to post-treatment recommendations (97%) and no difference by treatment arm was observed, the incidence of STIs at follow-up in women that did not adhere with a given recommendation was higher compared to their adherent counterparts. The incidence of gynecologic infection did not increase with any of the ablation treatments from baseline to the six-week follow-up. Non-gas cryotherapy and TA emerge as safe alternatives to gas-based cryotherapy with respect to gynecologic infection rates.

Clinical Characteristics, Prognosis and Treatment of Bloodstream Infections with Enterobacter Cloacae Complex in a Chinese Tertiary Hospital: A Retrospective Study.

Objective: This research aimed to analyze the clinical characteristics, prognosis, and antimicrobial treatment of bloodstream infections (BSI) caused by Enterobacter cloacae complex (ECC). Methods: The clinical data of patients with bloodstream infections caused by Enterobacter cloacae complex from April 2017 to June 2023 were collected retrospectively. These data were then analyzed in subgroups based on the detection results of extended-spectrum ß-lactamase (ESBL), 30-day mortality, and the type of antimicrobial agent used (ß-lactam/ß-lactamase inhibitor combinations (BLICs) or carbapenems). Results: The proportion of ESBL-producing Enterobacter cloacae complex was 32.5% (37/114). Meanwhile, ICU admission, receiving surgical treatment within 3 months, and biliary tract infection were identified as risk factors for ESBL-producing ECC-BSI. Additionally, immunocompromised status and Sequential Organ Failure Assessment (SOFA) score ≥ 6.0 were identified as independent risk factors of 30-day mortality in patients with ECC-BSI (n = 108). Further analysis in BSI patients caused by non-ESBL-producing ECC revealed that patients treated with BLICs (n = 45) had lower SOFA scores and lower incidence of hypoproteinemia and sepsis compared with patients treated with carbapenems (n = 20). Moreover, in non-ESBL-producing ECC-BSI patients, the univariate Cox regression analysis indicated a significantly lower 30-day mortality rate in patients treated with BLICs compared to those treated with carbapenems (hazard ratios (HR) [95% CI] 0.190 [0.055-0.662], P = 0.009; adjusted HR [95% CI] 0.106 [0.013-0.863], P = 0.036). Conclusion: This study investigated the factors influencing the susceptibility to infection by ESBL-producing strains and risk factors for 30-day mortality in ECC-BSI patients. The results revealed that ESBL-negative ECC-BSI patients treated with BLICs exhibited significantly lower 30-day mortality compared to those treated with carbapenems. BLICs were found to be more effective in ECC-BSI patients with milder disease (ESBL-negative and SOFA ≤6.0).

GC-IMS facilitates identification of carbapenem-resistant Klebsiella pneumoniae in simulated blood cultures.

This study aimed to identify carbapenem-resistant Klebsiella pneumoniae (CRKP) based on changes in levels of its volatile organic compounds (VOCs) in simulated blood cultures (BCs) using the gas chromatography-ion mobility spectrometry (GC-IMS) technique. A comprehensive analysis of volatile metabolites produced by Klebsiella pneumoniae (K. pneumoniae) in BC bottles was conducted using GC-IMS. Subsequently, the released VOCs were analyzed to examine differences in VOC release between CRKP and carbapenem-susceptible Klebsiella pneumoniae (CSKP). A total of 54 VOCs were detected, of which 18 (6 VOCs found in both monomer and dimer forms) were successfully identified. The VOCs produced by K. pneumoniae in BC bottles (BacT/ALERT® SA) were primarily composed of organic acids, alcohols, esters, and ketones. The content of certain VOCs was significantly different between CRKP and CSKP after the addition of imipenem (IPM). Moreover, the inclusion of carbapenemase inhibitors facilitated the identification of carbapenemase-producing K. pneumoniae based on the variations in VOCs. This study demonstrates the utility of GC-IMS technology in identifying CRKP, and reveals that changes in VOCs are closely related to the growth and metabolism of K. pneumoniae, indicating that they can be leveraged to promote early identification of CRKP bacteremia. However, further in-depth studies and experiments are needed to validate our findings.

Comparison of bacteremic pneumonia caused by Escherichia coli and Klebsiella pneumoniae: A retrospective study.

OBJECTIVES: To compare the prognosis of bacteremic pneumonia caused by Klebsiella pneumoniae (K. pneumoniae) and Escherichia coli (E. coli) pathogens. METHODS: A retrospective analysis was carried out on the clinical data of 162 patients who were diagnosed with bacterial pneumonia caused by either K. pneumoniae or E. coli between 2016-2019. The primary outcome of the analysis was the patients' 30-day mortality rate. RESULTS: There were 82 patients in the E. coli bacteremic pneumonia (E. coli-BP) group and 80 patients in the K. pneumoniae bacteremic pneumonia (KP-BP) group. The 30-day mortality rate was 43.75% (n=35/80) in the KP-BP group and 21.95% (n=18/82) in the E. coli-BP group (p<0.001). Following the adjustment for confounding variables in 4 distinct models, the hazard ratios for the primary outcome in KP-BP were determined to be 0.70 (95% confidence interval [CI]: [0.44-1.02]) in Model 1, 0.72 (95% CI: [0.46-1.14]) in Model 2, 0.99 (95% CI: [0.57-1.73]) in Model 3, and 1.22 (95% CI: [0.69-2.18]) in Model 4. CONCLUSION: Patients diagnosed with KP-BP exhibited a similar prognosis as those diagnosed with E. coli-BP. For patients with KP-BP, the risk of mortality was significantly higher for those who were in the intensive care unit, were infected with carbapenem-resistant strains, or had a high sequential organ failure assessment score. In patients with E. coli-BP, the Pitt bacteremia score was strongly associated with the 30-day mortality rate.

Biological characteristics and pathogenicity of a Staphylococcus aureus strain with an incomplete hemolytic phenotype isolated from bovine milk.

Staphylococcus aureus is a common pathogen capable of infecting both humans and animals and causing various severe diseases. Here, we aimed to determine the biological features and pathogenicity of S. aureus strain Sa9, of the incomplete hemolysis phenotype, isolated from bovine milk. Sa9 was classified as ST97 by multilocus sequence typing, and it showed increased ß-hemolysin expression and lower Hla and Hld expression levels compared with that in the S. aureus USA300 strain LAC. RT-PCR and ELISA results showed that the expression levels of inflammatory cytokines were higher in Sa9-induced mouse primary peritoneal macrophages compared with those induced by the LAC strain. However, the Sa9 strain also mediated anti-inflammatory effects by upregulating IL-10 and IFN-ß in macrophages, which were not apparently induced by S. aureus culture supernatants. Phagocytosis and whole-blood survival assays were also performed to assess the in vitro survival of bacteria, and the virulence was evaluated in mice. Although the Sa9 strain showed lower ability of intracellular survival in macrophages than LAC, similar multiplication in human whole blood and pathogenicity toward mice were observed. Taken together, we report that the distinctive immune response induced by the S. aureus strain with an incomplete hemolysis phenotype occurs in cattle, and its potential pathogenicity and risk of transmission to humans require attention.

Clinical Characteristics and Prognosis of Hospital-Acquired Klebsiella pneumoniae Bacteremic Pneumonia versus Escherichia coli Bacteremic Pneumonia: A Retrospective Comparative Study.

Objective: This research aimed to investigate the variations in clinical features and prognosis of HABP caused by E. coli and K. pneumoniae. We also aimed to evaluate the risk variables related to 30-day death in the investigated groups. Methods: A single-center retrospective cohort research lasting four years was performed. A total of 117 patients with HABP were involved in this research. The primary prognosis was 30-day death. Results: Among 117 patients with HABP, 60 patients were infected with K. pneumoniae (KP-HABP), and 57 patients were infected with E. coli (E. coli-HABP). A higher proportion of males, ICU admission, undergoing tracheotomy and trachea cannulation, carbapenem-resistant strains, inappropriate empirical therapy (IET), immune compromise, diabetes mellitus, and sepsis were observed in the patients with KP-HABP (all P < 0.05). Meanwhile, the median SOFA score and Pitt score were significantly (P < 0.001) higher in the KP-HABP group compared to the E. coli-HABP group. The 30-day death was 48.33% in the KP-HABP group and 24.56% in the E. coli-HABP group (P = 0.008). After adjusting for the main covariates, the hazard ratios for 30-day mortality in KP-HABP were 1.58 (95% CI:0.80-3.12), 3.24 (95% CI:1.48-7.06), 5.67 (95% CI:2.00-16.07), and 5.99 (95% CI:2.10-17.06), respectively. Multivariate logistic regression models revealed that IET, hypoproteinaemia, cerebral vascular disease (CVD), and SOFA score ≥ 5.0 were the independent risk variables for 30-day death in KP-HABP. Simultaneously, SOFA score ≥ 4.0 and Pitt score ≥ 2.0 were independent risk factors for 30-day mortality in E. coli-HABP. Conclusion: The clinical features of HABP vary depending on whether it is caused by Escherichia coli or K. pneumoniae. KP-HABP patients have higher 30-day mortality than E. coli-HABP patients. To ensure greater validity, it is necessary to further verify this conclusion using a larger sample size.

Early Lactate/Albumin and Procalcitonin/Albumin Ratios as Predictors of 28-Day Mortality in ICU-Admitted Sepsis Patients: A Retrospective Cohort Study.

BACKGROUND Lactate/albumin (LA/ALB) and procalcitonin/albumin (PCT/ALB) ratios have been implicated in predicting mortality in sepsis patients. However, their prognostic value and relationship to sepsis severity require further investigation. This retrospective study aimed to assess the prognostic value of lactate/albumin (LA/ALB) and procalcitonin/albumin (PCT/ALB) ratios in septic patients admitted to the Intensive Care Unit (ICU). MATERIAL AND METHODS A total of 340 adult sepsis patients admitted to the ICU were included in the derivation cohort. LA/ALB and PCT/ALB ratios were calculated and analyzed in relation to sepsis severity and survival status. Additionally, a validation cohort of 75 sepsis patients from another medical center was selected. RESULTS In the derivation cohort, higher LA/ALB and PCT/ALB ratios and SOFA scores were significantly associated with increased mortality (P<0.001). The LA/ALB and PCT/ALB ratios positively correlated with SOFA score. Survival analysis revealed significantly higher 28-day mortality in sepsis patients with elevated PCT/ALB (≥0.256) and LA/ALB (≥0.079) ratios upon ICU admission. The constructed prediction model incorporating LA/ALB ratio, PCT/ALB ratio, and SOFA score yielded an AUC of 0.826, demonstrating good predictive ability. The associations between LA/ALB and PCT/ALB ratios and 28-day mortality in sepsis patients were validated in the validation cohort. CONCLUSIONS The LA/ALB and PCT/ALB ratios at ICU admission provide valuable prognostic information for predicting 28-day mortality in sepsis patients. Combining these ratios with SOFA score improves the assessment of prognosis in sepsis patients.

Rapid Identification of Carbapenemase-Producing Klebsiella pneumoniae Using Headspace Solid-Phase Microextraction Combined with Gas Chromatography-Mass Spectrometry.

Background: Carbapenemase-producing Klebsiella pneumoniae is an unprecedented threat to public health, and its detection remains challenging. Analysis of microbial volatile organic compounds (VOCs) may offer a rapid way to determine bacterial antibiotic susceptibility. Purpose: The aim of this study was to explore the VOCs released by carbapenemase-producing carbapenem-resistant Klebsiella pneumoniae (CRKP) using headspace solid-phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS). Methods: Test bacteria were incubated in trypticase soy broth to the end of exponential growth phase, and imipenem was added in the middle time. Headspace VOCs were concentrated and analyzed using HS-SPME/GC-MS. Results: The compound 3-methyl-1-butanol was found to be a biomarker among the 26 bacterial isolates (10 KPC-positive, 10 NDM-positive, 2 IMP-positive, 2 carbapenemase-negative CRKP, and 2 carbapenem-susceptible K. pneumonoiae). Conclusion: This study explored a promising new strategy for the screening of carbapenemase-producing CRKP strains. Further research with larger sample sizes will potentially accelerate the application of biomarkers in routine microbiology.

Assessment of Effective Antimicrobial Regimens and Mortality-Related Risk Factors for Bloodstream Infections Caused by Carbapenem-Resistant Acinetobacter baumannii.

Objective: This study aimed to determine the clinical features, risk factors, and effective antimicrobial therapy for Carbapenem-resistant Acinetobacter baumannii (CRAB) bloodstream infection (BSI). Methods: This was a retrospective analysis of data from patients with CRAB bacteremia in a Chinese tertiary hospital between January 2012 and October 2021. Risk factors, predictors of 30-day mortality, and effective antimicrobial therapy for CRAB BSI were identified using logistic and cox regression analyses. Results: Data from 276 patients with Acinetobacter baumannii (AB) BSI were included, of whom 157 (56.9%) had CRAB BSI. The risk factors that were significantly associated with CRAB BSI included previous intensive care unit (ICU) stay (P < 0.001), immunocompromised status (P < 0.001), cephalosporin use (P = 0.014), and fluoroquinolone use (P = 0.007). The 30-day mortality of the CRAB BSI group was 49.7% (78/157). ICU stay after BSI (P = 0.047), sequential organ failure assessment (SOFA) score ≥10 (P < 0.001), and multiple organ failure (MOF) (P = 0.037) were independent predictors of 30-day mortality. Among antibiotic strategies for the treatment of patients with CRAB BSI, we found that definitive regimens containing cefoperazone/sulbactam were superior to those without cefoperazone/sulbactam in reducing the 30-day mortality rate (25.4% vs 53.4%, P = 0.005). After propensity score matching, we observed a significant increase in the 30-day mortality (77.8%vs 33.3%, P = 0.036) in patients receiving tigecycline monotherapy compared to those receiving cefoperazone/sulbactam monotherapy. The mortality rate of patients receiving tigecycline with cefoperazone/sulbactam was also higher than that of patients receiving cefoperazone-sulbactam monotherapy; however, the difference was not significant (28.6%vs 19.0%, P = 0.375). Conclusion: The severity of patient conditions was significantly associated with mortality in patients with CRAB BSI. Those Patients treated with cefoperazone/sulbactam had better clinical prognoses, and tigecycline should be used with caution.

Ceftazidime/Avibactam, Polymyxin or Tigecycline as a Rescue Strategy for the Treatment of Carbapenem-Resistant Klebsiella pneumoniae in Bloodstream Infection: A Retrospective Cohort Study.

Objective: To analyze the clinical characteristics, outcomes, and risk factors of patients treated with ceftazidime/avibactam, polymyxin, or tigecycline (CPT) compared with those receiving a conventional therapy (CT) (ie, imipenem, levofloxacin, or gentamicin). Methods: A single-center retrospective cohort study included patients with carbapenem-resistant Klebsiella pneumoniae bloodstream infection (CRKP-BSI) treated at one Chinese tertiary hospital between March 2012 and November 2022 was performed. Clinical characteristics, outcomes, and risk factors of patients treated with CPT or CT were compared. Predictors of 30-day mortality of patients with CRKP-BSI were also analysed in our study. Results: Among 184 recruited patients with CRKP-BSI, 39.7% (73/184) were treated with CPT, while 60.3% (111/184) were treated with CT. Compared to patients treated with CT, patients treated with CPT had worse conditions, as evidenced by a higher rate of underlying diseases and invasive procedures; however, they also had a better prognosis and lower rates of 14-day treatment failure (p = 0.024). In addition, univariate analysis and multivariate analysis showed that SOFA score [odds ratio (OR) = 1.310, 95% confidence interval (CI) 1.157-1.483; p < 0.001] and cold weather (OR = 3.658, 95% CI 1.474-9.081; p = 0.005) were independent risk factors for 30-day mortality. Conclusion: Compared to CRKP-BSI patients treated with CT, patients treated with CPT had worse conditions but better prognoses. CRKP-BSI occurred more frequently in hot weather; however, higher 30-day mortality was associated with cold weather. A randomized trial is needed to confirm these observational results.

Risk Factors for 30-Day Mortality in Patients with Bacteremic Pneumonia Caused by Escherichia coli and Klebsiella pneumoniae: A Retrospective Study.

Objective: Escherichia coli and Klebsiella pneumoniae are prevalent Gram-negative microorganisms responsible for pneumonia, as well as the primary Enterobacteriaceae pathogens causing bacteremic pneumonia. The objective of this research is to analyze the risk factors associated with bacteremic pneumonia caused by these pathogens and develop a predictive model. Patients and Methods: This retrospective investigation encompassed a cohort of 252 patients diagnosed with Escherichia coli or Klebsiella pneumoniae-induced bacteremic pneumonia between 2018 and 2022. The primary endpoint was 30-day mortality, which was analyzed using multifactorial logistic regression, nomogram construction, and Bootstrap validation. Results: Among the 252 patients diagnosed with Escherichia coli and Klebsiella pneumoniae, 65 succumbed to the disease while 187 survived. The overall 30-day mortality was found to be 25.8%. A multifactorial logistic regression analysis revealed that diastolic blood pressure, cerebrovascular diseases/transient ischemic attacks (TIA), immunosuppression, blood urea nitrogen, Pitt score, and CURB-65 score were statistically significant factors. The Nomogram model demonstrated an AUC of 0.954, which closely aligns with the Bootstrap-derived mean AUC of 0.953 (95% CI: 0.952-0.954). Conclusion: In patients with bacteremic pneumonia caused by Escherichia coli and Klebsiella pneumoniae, Low diastolic blood pressure (≤61 mmHg), pre-existing cerebrovascular disease/ transient ischemic attacks (TIA), immunosuppression status, elevated blood urea nitrogen levels (≥8.39 mmol/L), high Pitt score (≥3), and a high CURB-65 score (≥2) are all independent risk factors for Escherichia coli and Klebsiella pneumoniae bacteremic pneumonia, among which the first three warrant particular attention.

Comparison of Molecular Characteristics Between Methicillin-Resistant and -Susceptible Staphylococcus aureus Clinical Isolates by Whole-Genome Sequencing.

Introduction: The transmission of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA) are great public health concern worldwide. To better understand S. aureus evolution and dissemination, we compared the molecular features of MSSA and MRSA isolates. Methods: In this study, 74 MSSA and 102 MRSA non-duplicate isolates were recovered from clinical samples between 2016 and 2020. Molecular epidemiology, antimicrobial resistance determinants, and virulence gene profiles were carried out by whole-genome sequencing (WGS). Results: Twenty distinct sequence types were identified in MRSA isolates, with the most common being ST59, ST630, and ST338. The major genotypes of MSSA were ST188 and ST7. The toxin genes clfA, sek, and seq were significantly associated with MRSA, while splA/B, clfB, map, sdrC/D, and sem-sen-seo-seu were detected more frequently in MSSA isolates than MRSA (P < 0.05). The tst positive isolates were more commonly identified in CC1 and CC72, whereas lukE/D was mainly found in the CC7, CC15, CC88, and completely absent in CC59 clones. Conclusion: Our results compared the genetic diversity between MRSA and MSSA strains, suggesting efforts to fight infections caused by MSSA need to be intensified due to MSSA isolates carrying wide range of virulence factors. Comparative epidemiological studies of large populations of MSSA and MRSA will be necessary in the future to understand how MSSA and MRSA populations may co-evolve and interact in the future.

Identification of methicillin-resistant Staphylococcus aureus ST8 isolates in China with potential high virulence.

Methicillin-resistant Staphylococcus aureus (MRSA) ST8 strains have spread worldwide, causing outbreaks in various regions. However, this clone has only been sporadically reported in China. Consequently, detailed information regarding the phylogeny and potential virulence of S. aureus ST8 strains in China remains unknown. In this study, we characterized six ST8 strains collected from three tertiary hospitals in China, including three MRSA (MR50, MR526, and MR254) and three MSSA (H78, H849 and H863). Whole genome sequencing and phylogenetic analysis showed that the six strains formed two separate clusters, including two (MR50 and MR526) and four (MR254, H78, H849 and H863) isolates, respectively. Among them, MR50 and MR526 harboured spa t008, SCCmec IVa, arginine catabolic mobile element, and were phylogenetically close to the epidemic USA300 strains, while other four strains belonged to spa t9101 and formed a unique branch. MR254 carried a novel hybrid SCCmec element (namely SCCmec254). Same as the USA300 prototype strain LAC, the China S. aureus ST8 strains produced weak biofilms except MR254. Among them, MR254 had significantly stronger haemolysis ability and higher α-toxin levels than others, while MR526 showed comparable haemolysis and α-toxin production levels as USA300-LAC. In mouse skin abscess model, MR254 showed particularly strong invasions, accompanied by necrosis, while MR526 exhibited similar infection levels as USA300-LAC. These data suggested that the China MRSA ST8 isolates (e.g. MR254 and MR526) were highly virulent, displaying higher or similar virulence potential as the epidemic USA300 strain. Active surveillance should be enacted to closely monitor the further spread of these hyper-virulent MRSA strains in China.

Methicillin-resistant Staphylococcus aureus in China: a multicentre longitudinal study and whole-genome sequencing.

The aim of this study was to investigate the genomic epidemiology of MRSA in China to identify predominant lineages and their associated genomic and phenotypic characteristics. In this study, we conducted whole-genome sequencing on 565 MRSA isolates from 7 provinces and municipalities of China between 2014 and 2020. MRSA isolates were subjected to MLST, spa typing, SCCmec typing, analysis of virulence determinants and antimicrobial susceptibility testing. Among 565 MRSA isolates tested, clonal complex (CC) 59 (31.2%), CC5 (23.4%) and CC8 (13.63%) were the major lineages, and the clonal structure was dominated by ST59-t437-IV (14.9%), ST239-t030-III (6.4%) and ST5-t2460-II (6.0%), respectively. Of note, CC8, the predominant lineage in 2014-2015, was replaced by CC59 after 2016. Interestingly, the extension and unstable structure of the CC5 population was observed, with ST5-t311-II, ST764-t1084-II, ST5-t2460-II and ST764-t002-II existing complex competition. Further analysis revealed that virulence determinant profiles and antibiograms were closely associated with the clonal lineage. The CC59 MRSA was less resistant to most tested antimicrobials and carried fewer resistance determinants. But rifampicin resistance and mupirocin resistance were closely linked with CC8 and CC5, respectively. MRSA isolates conservatively carried multiple virulence genes involved in various functions. PVL encoding genes were more common in ST338, CC30, CC398, ST8 and CC22, while tsst-1 was associated with ST5. In conclusion, the community-associated CC59-ST59-t437-IV lineage was predominant in China, with diverse clonal isolates alternately circulating in various geographical locations. Our study highlights the need for MRSA surveillance in China to monitor changes in MRSA epidemiology.

Molecular Mechanisms of Colistin Resistance in Klebsiella pneumoniae in a Tertiary Care Teaching Hospital.

Background: Over the last two decades, the prevalence of colistin resistance among the members of Enterobacteriaceae has been increasing, particularly among Klebsiella pneumoniae isolates; this limits the potential use of colistin and leads to worsened clinical outcomes. Methods: We investigated the prevalence and genetic characteristics of colistin-resistant K. pneumoniae (COLR-KP) in clinical isolates using genomic sequencing. Results: In total, 53 K. pneumoniae isolates (4.5%, 53/1,171) were confirmed as COLR-KP, of which eight isolates carried mobile colistin-resistant (mcr) gene. Although the overall prevalence rate (0.7%, 8/1,171) of mcr-like genes in clinical K. pneumoniae remained relatively low, the presence of mcr (15.1%, 8/53) among the COLR-KP isolates indicated that the mobile resistance gene was already widespread among K. pneumoniae isolates in hospital setting. We randomly selected 13 COLR-KP isolates (four mcr-bearing and nine non-mcr-bearing isolates) for whole-genome sequencing, including two pandrug-resistant and four sequence type 11 (ST11) isolates. Phylogenetic analysis revealed that all COLR-KP isolates were genetically diverse. Among the four mcr-bearing isolates, three (KP4, KP18, and KP30) were positive for mcr-1 and one (KP23) for mcr-8; none of the other mcr genes were detected. The mcr-1 in the KP4 and KP30 isolates were located in an IncX4 plasmid (approximately 33 kb) and could be successfully transferred to Escherichia coli J53AZR. In contrast, for the mcr-8-bearing plasmid in KP23 (IncFII), colistin resistance could not be transferred by conjugation. The mcr-1-producing isolate KP18 coexists a novel plasmid-carried tigecycline resistance gene tmexCD1-toprJ1. The most common chromosomal mutation associated with colistin resistance was a T246A amino acid substitution in PmrB, which was identified in most COLR-KP isolates (11/13, 84.6%). All ST11 isolates additionally had an R256G amino acid substitution. Critical virulence factors associated with hypervirulent K. pneumoniae were detected in four COLR-KP isolates; these virulence factors included aerobactin, salmochelin, and yersiniabactin. Conclusion: We found that mcr-bearing COLR-KP emerged in our hospital and was growing at an increasing rate. Simultaneous emergence of hypervirulence and colistin-tigecycline-carbapenem resistance in the epidemic clone ST11 K. pneumoniae was also observed; this highlights the significance of active and continuous surveillance.

Corrigendum: First Report of Coexistence of bla SFO-1 and bla NDM-1 ß-Lactamase Genes as Well as Colistin Resistance Gene mcr-9 in a Transferrable Plasmid of a Clinical Isolate of Enterobacter hormaechei.

[This corrects the article DOI: 10.3389/fmicb.2021.676113.].