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

Abstract

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.

Keywords: China; Clonal lineage; Drug resistance; Methicillin‐resistant Staphylococcus aureus (MRSA); Pediatric.

Figure 1

Dynamics of epidemic MRSA in pediatric populations in China. (A) Dynamics of dominant clones among CA‐MRSA isolates. (B) Dynamics of dominant clones among HA‐MRSA isolates. MRSA, methicillin‐resistant Staphylococcus aureus; CA‐MRSA, community‐associated MRSA; HA‐MRSA, hospital‐acquired MSRA

Figure 2

Drug resistance rates of CA‐MRSA (A) and HA‐MRSA (B) in pediatric populations in China from 2010 to 2017. All isolates were susceptible to vancomycin and linezolid, which are not listed in the figure. MRSA, methicillin‐resistant Staphylococcus aureus; CA‐MRSA, community‐associated MRSA; HA‐MRSA, hospital‐acquired MSRA; PEN, penicillin; OXA, oxacillin; ERY, erythromycin; CLI, clindamycin; TET, tetracycline; GEN, gentamicin; CHL, chloramphenicol; CIP, ciprofloxacin; RIF, rifampin; SXT, trimethoprim‐sulfamethoxazole; MDR, multidrug resistance, resistant to ≥ 3 classes of non‐β‐lactam antimicrobials. *P < 0.05

Figure 3

Drug resistance rates of MRSA in pediatric populations stratified by genotype. (A) Drug‐resistance rates for ST239‐SCC mec type III, ST59‐SCC mec IV and other genotypes. (B) Drug resistance rates for ST59‐SCC mec IV between 2010–2013 and 2016–2017. (C) Drug resistance rate for CA‐MRSA and HA‐MRSA among ST59‐SCC mec IV isolates. All isolates were susceptible to vancomycin and linezolid, which are not listed in the figure. MRSA, methicillin‐resistant Staphylococcus aureus; CA‐MRSA, community‐associated MRSA; HA‐MRSA, hospital‐ acquired MRSA; PEN, penicillin; OXA, oxacillin; ERY, erythromycin; CLI, clindamycin; TET, tetracycline; G EN, gentamicin; CHL, chloramphenicol; CIP, ciprofloxacin; RIF, rifampin; SXT, trimethoprim‐sulfamethoxazole; MDR, multidrug resistance, resistant to ≥ 3 classes of non‐β‐lactam antimicrobials. *P < 0.05

Figure 4

Trends in the vancomycin susceptibility of MRSA strains in pediatric populations in China in 2010–2017. (A) and (B) present the distribution of MICs for vancomycin among all isolates and isolates belonging to ST59‐SCC mec IV, respectively. MRSA, methicillin‐resistant Staphylococcus aureus; MIC, minimal inhibitory concentration