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-SCCmec Ⅳ was the most prevalent type in both CA-MRSA (65.4%) and healthcare-associated-MRSA (HA-MRSA) (46.7%).ST239-SCCmec 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-SCCmec Ⅳ and ST239-SCCmec Ⅲ isolates.Vancomycin minimal inhibitory concentration (MIC) creep was found in the study period in all MRSA and ST59-SCCmec Ⅳ isolates.Interpretation:ST59-SCCmec Ⅳ has spread to hospitals and replaced the traditional ST239-SCCmec Ⅲ clone,accompanied by changes in drug resistance.Furthermore,vancomycin MIC creep indicated that the rational use of antibiotics should be seriously considered.

The diversity of clinical manifestations of human monkeypox should be emphasized in practice

The World Health Organization(WHO)announced on July 23,2022,that the human monkeypox(HMPX)epidemic 2022 was a public health emergency of international concern.In the current outbreak,the main HMPX patients were men who had sex with men in adults.Children less than 18 years of age accounted for only 0.15%(27/17641)of the confirmed HMPX cases in this outbreak.

A fatal case of liver abscess caused by hypervirulent Klebsiella pneumoniae in a diabetic adolescent:A clinical and laboratory study

Importance Hypervirulent variants of Klebsiella pneumoniae(hvKp)are capable of causing life-threatening pyogenic liver abscesses(PLAs),but hvKp caused PLAs was seldom reported in pediatric populations.Hence,there is an urgent need to raise our awareness of this phenomenon in pediatric populations.Objective This study aimed to report the clinical characteristics of hvKp that caused fatal PLA complicated by bacteremia in an adolescent and further identify the microbiological and genomic features of the causative strain.Methods A 14-year-old boy with diabetes mellitus was admitted to our hospital with a diagnosis of PLA complicated by bacteremia.A hypermucoviscous hvKp strain,KPN_19-106,was isolated from the drainage fluid present within the liver abscess cavity and blood.The hypermucoviscosity phenotype of the causative strain was determined by string test.Its virulence was measured using serum resistance assay and Galleria mellonella larvae-killing assay.Antimicrobial susceptibility was determined by broth microdilution method.Genetic information was obtained by whole-genome sequencing and bioinformatics analysis.Results KPN_19-106 belonged to sequence type 380 and serotype K2 and exhibited stronger serum resistance and higher in vivo lethality than the well-characterized hvKp NTUH-K2044 strain.Although KPN_19-106 is susceptible to most antibiotics,no sign of improvement was observed during treatment with such drugs.Whole-genome sequencing revealed that the isolate had integrated multiple mobile genetic elements related to virulence.Interpretation Antibiotic-susceptible hvKp can cause fatal PLA complicated by bacteremia in adolescents,with no improvement during antimicrobial therapy.The causative strain in this case had integrated multiple virulence genes and thus exhibited higher virulence both in vitro and in vivo when compared with NTUH-K2044.