Bacterial Etiology and Antimicrobial Resistance Pattern of Pediatric Bloodstream Infections in Beijing, 2015-2019.

Purpose: Bloodstream infections (BSIs) was an essential cause of morbidity and mortality in children. Empiric broad-spectrum treatment of BSIs may be costly and unable to effectively eliminate the correct pathogenic microbes, resulting in downstream antimicrobial resistance. The purpose was to provide evidence for diagnosis and treatment of bloodstream infections in pediatrics, by revealing the pathogen distribution and antibiotic resistance pattern of BSIs. Methods: In this 5-year study, a total of 2544 pathogenic bacteria stains, isolated from 2368 patients with BSI, were retrospectively analyzed, to define the species distribution and the antimicrobial resistance pattern in Beijing. Results: The most frequently isolated pathogenic bacteria were K. pneumoniae (12.1%), S. aureus (11.5%), E. coli (11.2%), and E. faecium (11.2%). Hematological malignancies were the most common disease among patients with underlying conditions. Methicillin resistance was detected in 30.0% of S. aureus and 81.7% of coagulase-negative Staphylococcus (CoNS), respectively. The detection rates of carbapenem-resistant-E. coli (CRECO) and carbapenem-resistant-K. pneumoniae (CRKPN) were 10.8% and 50.8%, respectively. In terms of 122 isolates of S. pneumonia, 5 isolates (4.1%) were penicillin-resistant Streptococcus pneumoniae (PRSP); meanwhile, 50 isolates (41.0%) were penicillin-intermediate Streptococcus pneumoniae (PISP). Among the non-fermentative gram-negative bacilli isolates, 22.8% and 26.9% of the P. aeruginosa, were resistant to imipenem and meropenem. Furthermore, the resistance rates of A. baumannii to imipenem and meropenem both were 54.5%. Conclusion: In the study, we demonstrated the characteristics of bloodstream infections and antimicrobial susceptibility pattern of pediatrics in Beijing. Gram positive bacteria were the main pathogens of BSIs. CoNS strains presented even higher resistance to multiple antibiotics, including methicillin, than S. aureus. K. pneumoniae and E. coli represent the most common isolated gram-negative bacteria and exhibited high resistance to a variety of antimicrobial agents. Therefore, it was of critical importance to implement appropriate antimicrobial medication according to pathogen distribution and drug susceptibility test.

A Hospital-Based and Cross-Sectional Investigation on Clinical Characteristics of Pediatric Streptococcus pneumoniae Isolates in Beijing from 2015 to 2021.

Introduction: Streptococcus pneumoniae (S. pneumoniae) is a major pathogen causing death in children. Few studies have evaluated the importance of S. pneumoniae in the identified bacteria in clinical work. This retrospective study aimed to reveal the rank of S. pneumoniae in determined bacteria isolated from children in Beijing, China, as well as the antimicrobial resistance of this pathogen. Methods: The number of specimen for bacterial culture and of bacterial species were cumulated and ranked based on the data of the two largest children's hospitals in Beijing from 2015 to 2021. The temporal change of S. pneumoniae culture, as well as the clinical data of S. pneumoniae isolates were collected and analyzed. The minimum inhibitory concentrations of antimicrobial agents were determined by BD Phoenix 100 automated system or Vitek 2 automated system for antimicrobial susceptibility testing. The breakpoints recommended by CLSI were adopted. Results: During the 7-year study period, a total of 45,631 bacterial isolates were cultured from 462,144 submitted specimens, in which S. pneumoniae was the third frequent agent following S. aureus and H. influenza, and accounting for 8.79% of the isolates (4011/45,631). In the 4011 S. pneumoniae isolates, 2239 and 997 ones were, respectively, isolated from sputum and bronchial lavage fluid. Most of S. pneumoniae strains were identified in winter (34.7%) and spring (26.1%), and were mainly isolated from patients under 5 years old (77.1%). Low susceptible rate (27.6%) of CSF isolates was determined to penicillin according to the parenteral meningitis breakpoints, while high susceptible rate (56.9%) of non-CSF isolates was obtained according to the parenteral non-meningitis breakpoints. The isolates showed low sensitivity to erythromycin and tetracycline (<5%). All isolates were susceptible to vancomycin and linezolid. Conclusion: The present results demonstrated that S. pneumoniae was one of the most commonly detected bacteria in current pediatric clinical tests, especially in young children under 5 years old, which emphasized the importance of prevention. Penicillin could still be the first empiric choice to treat non-meningitis pneumococcal infections, while erythromycin should not be involved in the treatment.

Hypervirulent Klebsiella pneumoniae Infections in Pediatric Populations in Beijing (2017-2019): Clinical Characteristics, Molecular Epidemiology and Antimicrobial Susceptibility.

BACKGROUND: Hypervirulent variants of Klebsiella pnuemoniae (hvKp) are emerging globally causing life-threatening infectious diseases; however, comprehensive studies on pediatric hvKp strains and related infections are still lacking. METHODS: Clinical data were collected from medical records. Genotype (multilocus sequence typing), capsular serotype, virulence gene profile and carbapenemase of the isolates were determined by PCR and DNA sequencing. Broth microdilution method was adopted to test the antimicrobial susceptibility. Hypermucoviscosity phenotype and the virulence of the strains were evaluated by string test and Galleria mellonella larvae killing assay. RESULTS: Among 319 K. pneumoniae strains, 26 (8.2%) hvKp were identified, the detection rates in 2017, 2018 and 2019 were 1.8%, 5.2% and 11.3%. The majority of hvKp infections were found in school-age children and adolescents (57.7%). Pneumonia was the most common diagnosis (38.5%). Single fatal case was hvKp caused liver abscess complicated with bacteremia. hvKp were dominated by ST23 (30.8%) and ST11 (30.8%). Eight carbapenem-resistant hvKp (CR-hvKp) were found, which all belonged to ST11. Virulence gene profile revealed that ST11 hvKp might carry incomplete pLVPK-like plasmids, but they exhibited comparable in vivo virulence to the other hvKp. CONCLUSIONS: The infections caused by hvKp are not frequent among pediatric populations, but the detection rate of hvKp in pediatric populations is increasing rapidly in recent years. The emerging and dissemination of ST11 CR-hvKp should be monitored continuously.

Accessory gene regulator (agr) dysfunction was unusual in Staphylococcus aureus isolated from Chinese children.

BACKGROUND: Staphylococcus aureus (S. aureus) with accessory gene regulator (agr) dysfunction occurs in health care settings. This study evaluated the prevalence and the molecular and drug resistance characteristics of S. aureus with dysfunctional agr in a pediatric population in Beijing, China. RESULTS: A total of 269 nonduplicate S. aureus clinical isolates were isolated from Beijing Children's Hospital, including 211 methicillin-resistant S. aureus (MRSA) from September 2010-2017 and 58 methicillin-sensitive S. aureus (MSSA) from February 2016-2017. Only 8 MRSA and 2 MSSA isolates were identified as agr dysfunction, and the overall prevalence rate was 3.7%. For MRSA isolates, ST59-SCCmec IV and ST239-SCCmec III were the most common clones, and the prevalence rate of agr dysfunction in ST239-SCCmec III isolates (17.39%) was significantly higher than in ST59-SCCmec IV (1.69%) and other genotype strains (P = 0.006). Among the agr dysfunctional isolates, only one MRSA ST59 isolate and one MSSA ST22 isolate harbored pvl. No significant difference was detected between agr dysfunction and agr functional isolates regarding the biofilm formation ability (P = 0.4972); however, 9/10 agr dysfunctional isolates could effectuate strong biofilm formation and multidrug resistance. Among MRSA, the non-susceptibility rates to ciprofloxacin, gentamicin, and trimethoprim-sulfamethoxazole were significantly higher in agr dysfunctional isolates than in isolates with functional agr (P < 0.05). Two isolates belonging to ST239 had no mutations in agr locus, but a synonymous mutation was found in agrA in another ST239 isolate. The inactivating mutations were detected in other seven agr dysfunctional isolates. The variants were characterized by non-synonymous changes (n = 5) and frameshift mutations (insertions, n = 2), which mainly occurred in agrC and agrA. CONCLUSIONS: The results showed that agr dysfunctional S. aureus was not common in Chinese children, and ST59-SCCmec IV was associated with lower prevalence of agr dysfunction as compared to ST239-SCCmec III isolates. The agr dysfunctional isolates were healthcare-associated, multidrug resistant and form strong biofilm, which suggested that agr dysfunction might offer potential advantages for S. aureus to survive in a medical environment.

Clonal and drug resistance dynamics of methicillin-resistant Staphylococcus aureus in pediatric populations in China.

IMPORTANCE: Regional clonal replacements of methicillin-resistant Staphylococcus aureus (MRSA) are common. It is necessary to understand the clonal and drug resistance changes in specific areas. OBJECTIVE: To evaluate the clonal and drug resistance dynamics of MRSA in Chinese children from 2010 to 2017. METHODS: MRSA was isolated from patients in Beijing Children's Hospital from 2010 to 2013 and from 2016 to 2017. The molecular characteristics and antibiotic resistance were determined. RESULTS: In total, 211 MRSA isolates were collected, and 104 isolates were classified as community-associated MRSA (CA-MRSA). ST59-SCC mec IV was the most prevalent type in both CA-MRSA (65.4%) and healthcare- associated-MRSA (HA-MRSA) (46.7%). ST239-SCC mec III accounted for 21.5% of all HA-MRSA, which were not detected in 2016, and only three isolates were detected in 2017. The pvl gene carrying rate of CA- MRSA was significantly higher than that of HA-MRSA (42.3% vs. 29.0%, P = 0.0456). Among CA-MRSA, resistance rate to all tested antibiotics excluding chloramphenicol remained stable over the periods of 2010-2013 and 2016-2017. HA-MRSA displayed an overall trend of decreased resistance to oxacillin, gentamicin, tetracycline, ciprofloxacin, and rifampin, and increased resistance to chloramphenicol, consistent with the difference of antibiotic resistance patterns between ST59-SCC mec IV and ST239-SCC mec III isolates. Vancomycin minimal inhibitory concentration (MIC) creep was found in the study period in all MRSA and ST59-SCC mec IV isolates. INTERPRETATION: ST59-SCC mec IV has spread to hospitals and replaced the traditional ST239-SCC mec III clone, accompanied by changes in drug resistance. Furthermore, vancomycin MIC creep indicated that the rational use of antibiotics should be seriously considered.

Multiresistant ST59-SCCmec IV-t437 clone with strong biofilm-forming capacity was identified predominantly in MRSA isolated from Chinese children.

BACKGROUND: This study aimed to investigate the clinical and molecular epidemiology and biofilm formation of Staphylococcus aureus (SA) isolated from pediatricians in China. METHODS: SA strains were isolated from Beijing Children's hospital from February 2016 to January 2017. Isolates were typed by multilocus sequence typing (MLST), spa and SCCmec typing (for Methicillin-resistant SA [MRSA] only). Antimicrobial susceptibility testing was performed by agar dilution method except sulphamethoxazole/trimethoprim (E-test method). Biofilm formation and biofilm associated genes were detected. RESULTS: Totally 104 children (41 females and 63 males; median age, 5.2 months) were enrolled in this study, in which 60 patients suffered from MRSA infection. Among the 104 cases, 54.8% were categorized as community associated SA (CA-SA) infections. The children under 3 years were more likely to occur CA-SA infections compared with older ones (P = 0.0131). ST59-SCCmec IV-t437 (61.7%) was the most prevalent genotype of MRSA, and ST22-t309 (18.2%), ST5-t002 (9.1%), ST6-t701 (9.1%), ST188-t189 (9.1%) were the top four genotypes of methicillin-sensitive SA (MSSA). All the present isolates were susceptible to linezolid, vancomycin, trimethoprim-sulfamethoxazole, mupirocin, tigecyclin, fusidic acid. No erythromycin-susceptible isolate was determined, and only a few isolates (3.8%) were identified as susceptible to penicillin. Multi-drug resistant isolates were reponsible for 83.8% of the ST59-SCCmec IV-t437 isolates. The isolates with strong biofilm formation were found in 85% of MRSA and 53.2% of MSSA, and in 88.7% of ST59-SCCmec IV-t437 isolates. Biofilm formation ability varied not only between MRSA and MSSA (P = 0.0053), but also greatly among different genotypes (P < 0.0001). The prevalence of the biofilm associated genes among ST59-SCCmec IV-t437 clone was: icaA (100.0%), icaD (97.3%), fnbpA (100.0%), fnbpB (0), clfA (100%), clfB (100%), cna (2.7%), bbp (0), ebpS (88.5%), sdrC (78.4%), sdrD (5.4%), and sdrE (94.5%). CONCLUSIONS: These results indicated strong homology of the MRSA stains isolated from Chinese children, which was caused by spread of multiresistant ST59-SCCmec IV-t437 clone with strong biofilm formation ability. The MSSA strains, in contrast, were very heterogeneity, half of which could produce biofilm strongly.

[Transfer of erythromycin-resistance among strains and species of bacteria: plasmid conjugation method in enterococcal isolates].

OBJECTIVE: To study if the resistance to macrolide in Enterococcus can be transferred between strains, and species of the same and different genera. METHODS: Agar dilution was used to screen 30 enterococcal isolates that were resistant to erythromycin. Conjugation was performed by filter mating method. The 30 donor bacteria included 13 strains of Enterococcus faecalis, 16 strains of E. faecium, and 1 strain of E. hirae. The recipient bacteria included 1 strain of E. faecalis sensitive to erythromycin and resistant to tetracycline, and 1 strain of Staphylococcus aureus with the MIC against erythromycin of 0.25 approximately 1 microg/ml. Polymerase chain reaction was used to test the existence of ermB gene and the tranposons Tn1545 and Tn917 in the enterococcal isolates before and after filter mating. RESULTS: The transfer rate between different strains and species of the same genus were all 100%. The MIC(50) and MIC(90) against erythromycin of 13 conjugates were both 512 microg/ml, and Tn1545 and Tn917 were found in the ermB gene of 12 conjugates. 17 conjugates were obtained from 16 strains of donor E. faecium and 1 strain of E. hirae with the MIC(50) and MIC(90) both of 512 microg/ml. The ermB gene was found in 16 of the 17 conjugates, and 11 of the 16 conjugates showed the existence of Tn1545 and Tn917, Tn1545 existed in the ermB gene of 4 conjugates, and Tn917 existed in the ermB gene of 1 conjugate. 30 conjugates of Staphylococcus aureus were obtained by plasmid conjugation and transfer with a transfer rate of 100% and the MIC(50) and MIC(90) both of 512 microg/ml. The ermB gene was found in 28 of the 30 conjugates. Both Tn1545 and Tn917 were found in the ermB gene of 23 of the 28 conjugates, Tn1545 was found in the ermB gene of 4 conjugates, and Tn917 was found in the ermB gene of 1 conjugate. CONCLUSION: The resistance to macrolide of Enterococcus, related with the existence of ermB gene and transposons Tn1545 and Tn917, can be transferred between strains and species of same and different genera.

[Characteristics of community-acquired Methicillin-resistant Staphylococcus aureus infection in children].

OBJECTIVE: To investigate the prevalence and drug resistant patterns of community-acquired Methicillin-resistant Staphylococcus aureus (MRSA) in children. METHODS: Samples of sputum, blood, liquor puris/secretion of skin or stool in Beijing Children's Hospital between January, 2002 and March, 2005 were cultured. The characteristics of community-acquired MRSA infection were analyzed and compared with hospital-acquired MRSA infection. RESULTS: A total of 25 strains of MRSA were found during the study period and they accounted for 4.7% in 512 strains of Staphylococcus aureus. Of the 25 strains of MRSA, 20 strains were community-acquired but only 5 were hospital-acquired. The prevalence of MRSA infection in Staphyloccus aureus has kept rising over last two years, 3.1% in 2003, 5.4% in 2004 and 7.2% in the first season of 2005. There were no statistical differences in the results of antimicrobial susceptibility testing and multi-resistance testing between the groups of community-acquired and hospital-acquired MRSA. In both groups, all isolates were susceptible to vancomycin. The percentage of the patients with underlying disease in the hospital-acquired infection group was significantly higher than in community-acquired infection group (P < 0.05), but the onset age was not different. CONCLUSIONS: The prevalence of community-acquired MRSA infection tends to increase in children. The drug resistant patterns of community-acquired MRSA were not significantly different from the hospital-acquired MRSA in children.