Prevalence, Characterization, and Drug Resistance of Staphylococcus Aureus in Feces From Pediatric Patients in Guangzhou, China

Clinical and molecular epidemiology of carbapenem-resistant Enterobacteriaceae in pediatric inpatients in South China

IMPORTANCE

This study assessed the clinical and molecular epidemiology of carbapenem-resistant Enterobacteriaceae in pediatric inpatients at three hospitals in South China by means of screening stool samples for carbapenem-resistant genes and a nested case-control study to determine risk factors for carriage of carbapenem-resistant Enterobacteriaceae. Of 4,033 fecal samples screened, 158 (3.92%) were positive for CRE, including Escherichia coli (51.27 %), Klebsiella pneumoniae (37.97%), and Enterobacter cloacae (6.96%). The most common carbapenemase genes harbored by gastrointestinal CRE strains were blaNDM-5, blaNDM-1, and blaIMP-4. Hematological malignancies, respiratory diseases, otolaryngological diseases, nervous system diseases, oral administration of third-generation cephalosporins, and the combined use of two or more antibiotics were independently associated with CRE colonization.

Molecular Characteristics of Methicillin-Resistant and Susceptible Staphylococcus aureus from Pediatric Patients in Eastern China

Staphylococcus aureus is an opportunistic pathogen that causes invasive infections in humans. In recent years, increasing studies have focused on the prevalence of S. aureus infections in adults; however, the epidemiology and molecular characteristics of S. aureus from Chinese pediatric patients remain unknown. The present study examined the population structure, antimicrobial resistance, and virulent factors of methicillin-resistant and -susceptible S. aureus isolated from Chinese pediatric patients from one medical center in eastern China. A total of 81 cases were screened with positive S. aureus infections among 864 pediatric patients between 2016 and 2022 in eastern China. Molecular analysis showed that ST22 (28.4%) and ST59 (13.6%) were the most typical strains, and associations between different clonal complex (CC) types/serotype types (ST) and the age of pediatric patients were observed in this study. CC398 was the predominant type in neonates under 1 month of age, while CC22 was mainly found in term-infant (under 1 year of age) and toddlers (over 1 year of age). Additionally, 17 S. aureus isolates were resistant to at least three antimicrobials and majority of them belonged to CC59. The blaZ gene was found in 59 isolates and mecA gene was present in 26 strains identified as methicillin-resistant. Numerous virulent factors were detected in S. aureus isolated from present pediatric patients. Remarkably, lukF-PV and lukS-PV were dominantly carried by CC22, tsst-1 genes were detected in CC188, CC7, and CC15, while exfoliative toxin genes were found only in CC121. Only 41.98% of the S. aureus isolates possessed scn gene, indicating that the sources of infections in pediatric patients may include both human-to-human transmissions as well as environmental and nosocomial infections. Together, the present study provided a phylogenetic and genotypic comparison of S. aureus from Chinese pediatric patients in Suzhou city. Our results suggested that the colonization of multi-drug resistant isolates of S. aureus may raise concern among pediatric patients, at least from the present medical center in eastern China.

Prevalence and molecular characteristics of community-associated methicillin-resistant Staphylococcus aureus in the respiratory tracts of Chinese adults with community-acquired pneumonia

BACKGROUND

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is an important pathogen causing healthcare-associated infections. In recent years, an increasing number of CA-MRSA clones have emerged and rapidly spread in the community and hospital settings in China.

OBJECTIVES

To investigate the molecular epidemiology and resistance of CA-MRSA in the respiratory tracts of Chinese adults with community-acquired pneumonia (CAP).

METHODS

A total of 243 sputum samples were collected from adult patients with CAP at the Nantong Hospital in China between 2018 and 2021. S. aureus was identified using PCR, and its susceptibility to 14 antimicrobials was tested using the broth dilution method. Genomic characterization of respiratory CA-MRSA and our previously collected intestinal CA-MRSA isolates was performed using whole-genome sequencing, and the evolutionary relationships of these isolates were assessed using phylogenetic analysis.

RESULTS

The CA-MRSA colonization rate among adults with CAP in China was 7.8 % (19/243). Antimicrobial resistance analysis revealed that the proportion of multidrug-resistant respiratory CA-MRSA isolates (100 %) was higher than that of intestinal CA-MRSA isolates (6.3 %). Among the 35 CA-MRSA isolates, 10 MLST types were identified and clustered into five clone complexes (CCs). CC5 (48.6 %) and CC88 (20 %) were predominant CA-MRSA clones. Notably, the CC5 clone ST764/ST6292-MRSA-II-t002 was identified as the major lineage causing respiratory tract infections in Chinese adults with CAP.

CONCLUSIONS

The prevalence of CA-MRSA among Chinese adults with CAP is high and often involves ST764/ST6292-MRSA-II-t002 as the causal pathogen.

Phylogenetic Analysis and Virulence Characteristics of Methicillin-Resistant Staphylococcus aureus ST45 in China: a Hyper-Virulent Clone Associated with Bloodstream Infections

Methicillin-resistant Staphylococcus aureus (MRSA) sequence type 45 (ST45) was rarely found in China. This study was conducted to trace the transmission and evolution of emerging MRSA ST45 strains in mainland China and explore its virulence. A total of 27 ST45 isolates were included for whole-genome sequencing and genetic characteristic analysis. Epidemiological results showed that MRSA ST45 isolates were often obtained from blood, primarily originated in Guangzhou, and carried diverse virulence and drug resistance genes. Staphylococcal cassette chromosome mec type IV (SCCmec IV) dominated in MRSA ST45 (23/27, 85.2%). ST45-SCCmec V was located on a phylogenetic clade distinct from the SCCmec IV cluster. We selected two representative isolates, MR370 (ST45-SCCmec IV) and MR387 (ST45-SCCmec V), and performed hemolysin activity, a blood killing assay, a Galleria mellonella infection model, and a mouse bacteremia model, as well as real-time fluorescence quantitative PCR. MR370 was proved to have extreme virulence in the phenotypic assays and at the mRNA level compared with ST59, ST5, and USA300 MRSA strains. MR387 was comparable to USA300-LAC on the phenotype and was verified to have higher expression of scn, chp, sak, saeR, agrA, and RNAIII than USA300-LAC. The results emphasized the extraordinary performance of MR370 and the good potential of MR387 in virulence causing bloodstream infection. Meanwhile, we conclude that China MRSA ST45 showed two different clonotypes, which may be widespread in the future. The entire study is valuable as a timely reminder and reports virulence phenotypes of China MRSA ST45 for the first time. IMPORTANCE Methicillin-resistant Staphylococcus aureus ST45 is epidemic worldwide. This study contributed to the awareness of the Chinese hyper-virulent MRSA ST45 strains and served as a timely reminder of its wide dissemination of clonotypes. Further, we provide novel insights for prevention from the perspective of bloodstream infections. ST45-SCCmec V is a clonotype deserving special attention in China, and we performed genetic and phenotypic analyses for the first time on it.

Molecular Characterization of Methicillin-Sensitive Staphylococcus aureus from the Intestinal Tracts of Adult Patients in China

Intestinal infections caused by methicillin-sensitive Staphylococcus aureus (MSSA) have posed a great challenge for clinical treatments. In recent years, the intestinal carriage rates of MSSA have risen steadily in hospital settings in China. However, the epidemiology and molecular characteristics of MSSA from the intestinal tracts of Chinese adult patients remain unknown. In the present study, a total of 80 S. aureus isolates, including 64 MSSA and 16 methicillin-resistant Staphylococcus aureus (MRSA), were recovered from 466 fecal swabs in adult patients between 2019 and 2021 in China. The MSSA isolates exhibited high resistance to penicillin (92.2%) and erythromycin (45.3%). In addition, a higher proportion of MSSA isolates (14.1%) were multidrug-resistant (MDR) strains than that of MRSA isolates (1.3%). Among the 64 MSSA isolates, we identified 17 MLST types, of which ST398 and ST15 were the most predominant types. The most frequently detected resistance genes were blaZ (87.5%) and erm(C) (21.9%). The hemolysin genes (hla, hld, hlgA, hlgB, hlgC) were detected in all the MSSA isolates, but the Panton–Valentine leucocidin (pvl) gene was identified in 1.7% of the MSSA isolates. Our findings indicated that the prevalence and antimicrobial resistance of intestinal MSSA was a serious concern among adult patients in China.

Antimicrobial susceptibility testing of Staphylococcus aureus isolates from patients at a tertiary hospital in Tehran, Iran, 2018-2019

Background

Staphylococcus aureus, a human skin and mucous membranes colonizer, could opportunistically cause a variety of infectious diseases. Frequently, it is resistant to methicillin (MRSA), and often, co-resistant to many clinically available antibiotics. MRSA is a major burden for healthcare systems and communities all over the world, especially in developing countries. We addressed the issue that more than a decade had passed since the last report about cumulative antibiogram for S. aureus from our center, whereas The Clinical and Laboratory Standards Institute (CLSI) recommends to analyze and report it on an annual basis in order to guide clinicians to select the best initial empiric antimicrobial therapy.

Methods

In a cross-sectional retrospective design, data of culture-proven S. aureus from clinical specimens of hospitalized patients at Imam Khomeini Hospital Complex, Tehran, Iran, were collected from September 2018 to September 2019. Antimicrobial susceptibility testing (AST) had been performed using either Kirby–Bauer disk diffusion or VITEK 2 automated system which is based on minimum inhibitory concentration (MIC). The Chi-squared test was used considering the critical p-value to be ≤ .05.

Results

Among 576 unique isolates, the overall prevalence of MRSA was 37.5%. Patients admitted to the infectious diseases ward and ICUs have a greater chance to have such an isolate. Methicillin resistance was predictive of resistance to most antibiotics: erythromycin (90.9%), clindamycin (85.4% including inducible resistance), gentamicin, cipro-/levo-/moxi-floxacin, trimethoprim–sulfamethoxazole (58.3%), tetracycline, and rifampin. Resistance rate of zero was observed for daptomycin, linezolid, tigecycline, and (roughly) vancomycin. The prevalence of multiple-drug resistant (MDR) isolates was 48.5%.

Conclusions

Although in this study, the prevalence of MRSA was lower than the previous ones from the same hospital, it is still far from the desired rates. Besides, resistance to clindamycin and trimethoprim–sulfamethoxazole were remarkable. So far, vancomycin is the best choice for empiric treatment of MRSA, with linezolid as the second choice. It is advised to avoid prescribing the newer antibacterial agents as long as the older ones are effective to prevent the emergence of MDR species.

Comprehensive evaluation and analysis of the salinity stress response mechanisms based on transcriptome and metabolome of Staphylococcus aureus

Staphylococcus aureus possesses an extraordinary ability to deal with a wide range of osmotic pressure. This study performed transcriptomic and metabolomic analyses on the potential mechanism of gradient salinity stress adaptation in S. aureus ZS01. The results revealed that CPS biosynthetic protein genes were candidate target genes for directly regulating the phenotypic changes of biofilm. Inositol phosphate metabolism was downregulated to reduce the conversion of functional molecules. The gluconeogenesis pathway and histidine synthesis were downregulated to reduce the production of endogenous glucose. The pyruvate metabolism pathway was upregulated to promote the accumulation of succinate. TCA cycle metabolism pathway was downregulated to reduce unnecessary energy loss. L-Proline was accumulated to regulate osmotic pressure. Therefore, these self-protection mechanisms can protect cells from hypertonic environments and help them focus on survival. In addition, we identified ten hub genes. The findings will aid in the prevention and treatment strategies of S. aureus infections.

Active Surveillance, Drug Resistance, and Genotypic Profiling of Staphylococcus aureus Among School-Age Children in China

Methicillin-susceptible (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization predisposes individuals for endogenous infections and is a major threat to children. Recently, oxacillin/cefoxitin-susceptible mecA-positive S. aureus (OS-MRSA) has been reported worldwide. Herein, a prospective, cross-sectional study was conducted across five schools, representing three educational stages, in Guangzhou, China. Nasal swabs from 2,375 students were cultured for S. aureus and all isolates were subjected to antibiotic susceptibility testing phenotypically and confirmed by femB and mecA genetic detection; all the isolates were classified as MSSA, MRSA, or OS-MRSA. All strains were also analyzed by multi-locus sequence typing. Among the 2,375 swabs, S. aureus was detected in 744 children (31.3%, 95% CI: 25.9–36.7%), of whom 72 had MRSA (3.0%, 95% CI: 0.6–5.4%) and 4 had OS-MRSA (0.2%, 95% CI: 0.1–0.3%), of which an oxacillin- and cefoxitin-susceptible MRSA strain was identified. The prevalence of S. aureus and MRSA was higher in younger children. The highest percentage of drug resistance of the S. aureus isolates (n = 744) was to penicillin (85.5%), followed by erythromycin (43.3%) and clidamycin (41.0%). The most prevalent sequence types (STs) were ST30, ST45, and ST188 in MSSA, accounting for 38.7% of the total isolates, whereas ST45, ST59, and ST338 accounted for 74.6% of the MRSA isolates and ST338 accounted for 50.0% of the OS-MRSA isolates. The MRSA and OS-MRSA isolates (n = 76) were grouped into three clades and one singleton, with clonal complex (CC) 45 as the most predominant linkage. The top nine multi-locus sequence typing-based CCs (CC30, CC45, CC5, CC1, CC15, CC944, CC398, CC59, CC7) represented 86.7% of all S. aureus isolates. All CC30 isolates were resistant to erythromycin and clidamycin, and almost all these isolates were also resistant to penicillin (99.2%). The CC45 and CC59 isolates exhibited high resistance rates to oxacillin at 31.5 and 59.0%, respectively. This study provides updated data valuable for designing effective control strategies to mitigate the burden of disease and to improve the adequacy of empirical antimicrobial treatments for potentially harmful infections.

Pharmacokinetics, Urinary Excretion, and Pharmaco-Metabolomic Study of Tebipenem Pivoxil Granules After Single Escalating Oral Dose in Healthy Chinese Volunteers

Tebipenem pivoxil (TBPM-PI), an oral carbapenem antibiotic, has shown special advantages in pediatric infections and was in urgent need in China. Although pharmacokinetics, urinary excretion, and metabolite information of its active form tebipenem (TBPM) has been reported, ethnic differences may exist among the Chinese and Japanese population. By now, no systematic pharmacokinetics, urinary excretion, metabolites, or safety information has been revealed to the Chinese population. The purpose of the present work was to investigate abovementioned information of TBPM-PI granules after oral single ascending doses of 100, 200, and 400 mg in Chinese volunteers. Based on the pharmacokinetic study, the urine pharmaco-metabolomic analysis was conducted to reveal metabolomic interruptions and metabolite information. The study design was a single-center, open-label, randomized, single-dose pharmacokinetic study of 36 healthy volunteers (with half of them being male and the other half female). Time to maximum concentration (T max) was reached at 0.50, 0.50, or 0.67 h for 100, 200, or 400 mg, respectively. The linear pharmacokinetic characteristic of maximum plasma concentration (C max) was detected over 100-200 mg. The area under the concentration time curve (AUC) was proportional to the dose in the range of 100-400 mg. The maximum urinary excretion rate was detected at 0-1 or 1-2 h for dose of 100 or 200-400 mg. Cumulative amount of TBPM excreted in urine by 24 h accounted up to 90, 95, and 80% of dose administered for three groups, respectively. The pharmaco-metabolomic analysis revealed urine metabolic trajectory of deviation at 0-1 or 1-2 h and gradually regressing back to the pre-dose group at the following time periods. Urine metabolites from M1 to M4 were identified, indicating ethnic difference in metabolites among the Chinese or Japanese population. The current work proved safety and tolerance of single-dose administration of oral TBPM-PI in Chinese healthy volunteers over doses of 100-400 mg. All these results provide pharmacokinetics, urine excretion, urine metabolomics, urine metabolites, and safety information in healthy Chinese volunteers after oral single ascending doses of TBPM-PI, benefitting further development and clinical utilities.