Dissemination and Molecular Characterization of Staphylococcus aureus at a Tertiary Referral Hospital in Xiamen City, China

The antimicrobial activity of cethromycin against Staphylococcus aureus and compared with erythromycin and telithromycin

BACKGROUND

This study aims to explore the antibacterial activity of cethromycin against Staphylococcus aureus (S. aureus), and its relationship with multilocus sequence typing (MLST), erythromycin ribosomal methylase (erm) genes and macrolide-lincosamide-streptogramin B (MLSB) phenotypes of S. aureus.

RESULTS

The minimum inhibitory concentrations (MICs) of cethromycin against 245 S. aureus clinical isolates ranged from 0.03125 to ≥ 8 mg/L, with the resistance of 38.8% in 121 methicillin-resistant S. aureus (MRSA). This study also found that cethromycin had strong antibacterial activity against S. aureus, with the MIC ≤ 0.5 mg/L in 55.4% of MRSA and 60.5% of methicillin-sensitive S. aureus (MSSA), respectively. The main MLSTs of 121 MRSA were ST239 and ST59, and the resistance of ST239 isolates to cethromycin was higher than that in ST59 isolates (P = 0.034). The top five MLSTs of 124 MSSA were ST7, ST59, ST398, ST88 and ST120, but there was no difference in the resistance of MSSA to cethromycin between these STs. The resistance of ermA isolates to cethromycin was higher than that of ermB or ermC isolates in MRSA (P = 0.016 and 0.041, respectively), but the resistance of ermB or ermC isolates to cethromycin was higher than that of ermA isolates in MSSA (P = 0.019 and 0.026, respectively). The resistance of constitutive MLSB (cMLSB) phenotype isolates to cethromycin was higher than that of inducible MLSB (iMLSB) phenotype isolates in MRSA (P < 0.001) or MSSA (P = 0.036). The ermA, ermB and ermC genes was mainly found in ST239, ST59 and ST1 isolates in MRSA, respectively. Among the MSSA, the ermC gene was more detected in ST7, ST88 and ST120 isolates, but more ermB genes were detected in ST59 and ST398 isolates. The cMLSB phenotype was more common in ST239 and ST59 isolates of MRSA, and was more frequently detected in ST59, ST398, and ST120 isolates of MSSA.

CONCLUSION

Cethromycin had strong antibacterial activity against S. aureus. The resistance of MRSA to cethromycin may had some clonal aggregation in ST239. The resistance of S. aureus carrying various erm genes or MLSB phenotypes to cethromycin was different.

Molecular Epidemiology of Staphylococcus aureus in a Tertiary Hospital in Anhui, China: ST59 Remains a Serious Threat

Purpose

This study aimed to investigate the molecular characteristics, antimicrobial resistance and hemolytic phenotype of Staphylococcus aureus isolated from Anhui, China.

Results

From August 2021 to January 2022, 214 S. aureus isolates were collected from the Anhui Provincial Hospital. This study identified 117 methicillin-resistant S. aureus and 97 methicillin-sensitive S. aureus isolates, and the detection rate of methicillin-resistant isolates was 1.8-fold higher than the average isolates reported in China (53.9% vs 30.5%). S. aureus isolates share identity at five or more of the seven MLST-based housekeeping loci, referred to as the clonal complex (CC). Forty ST types were found in 214 clinical S. aureus isolates, with the most extensive distribution of ST59 and ST6697 typing numbers and higher CC5 detection rates than any other clonal group. (The ST typing is the result of the MLST typing website query.) To detect the virulence of ST types of S. aureus, hemolysis experiments were performed on 214 clinical isolates, and it was concluded that ST59 had a relatively robust hemolytic capacity.

Conclusion

Anhui S. aureus isolates have unique molecular and antibiotic resistance profiles. The antibiotic resistance profile may be related to the random use of antibiotics.

Molecular Characterization of Community- and Hospital- Acquired Methicillin-Resistant Staphylococcus aureus Isolates during COVID-19 Pandemic

Methicillin-resistant Staphylococcus aureus (MRSA) is a drug-resistant superbug that causes various types of community- and hospital-acquired infectious diseases. The current study was aimed to see the genetic characteristics and gene expression of MRSA isolates of nosocomial origin. A total of 221 MRSA isolates were identified from 2965 clinical samples. To identify the bacterial isolates, the clinical samples were inoculated on blood agar media plates first and incubated at 37 °C for 18-24 h. For further identification, the Gram staining and various biochemical tests were performed once the colonies appeared on the inoculated agar plates. The phenotypic identification of antibiotic susceptibility patterns was carried out using Kirby-Bauer disk diffusion method by following the Clinical and Laboratory Standards Institute (CLSI) 2019 guidelines. The biofilm-producing potentials of MRSA were checked quantitatively using a spectrophotometric assay. All strains were characterized genotypically by SCCmec and agr typing using the specific gene primers. Furthermore, a total of twelve adhesion genes were amplified in all MRSA isolates. MRSA was a frequently isolated pathogen (44% community acquired (CA)-MRSA and 56% hospital acquired (HA)-MRSA), respectively. Most of the MRSA isolates were weak biofilm producers (78%), followed by moderate (25%) and strong (7%) biofilm producers, respectively. Prominent adhesion genes were clfB (100%), icaAD (91%), fib (91%), sdrC (91%) followed by eno (89%), fnbA (77%), sdrE (67%), icaBC (65%), clfA (65%), fnbB (57%), sdrD (57%), and cna (48%), respectively. The results of the current study will help to understand and manage the spectrum of biofilm-producing MRSA-associated hospital-acquired infections and to provide potential molecular candidates for the identification of biofilm-producing MRSA.

Characteristics of Virulence Genes of Clinically Isolated Staphylococci in Jingzhou Area

Purpose

The aim of this study was to further understand the distribution characteristics of staphylococcal virulence genes in the Jingzhou area, in order to provide a basis for clinically effective treatments and prevention and control measures.

Methods

A total of 181 strains of staphylococci were collected from Jingzhou Hospital Affiliated to Yangtze University from April 2013 to April 2021, which were divided into the methicillin-resistant Staphylococcus aureus (MRSA) strains and the methicillin-sensitive Staphylococcus aureus (MSSA) strains and coagulase-negative staphylococci (CoNS) by an antimicrobial susceptibility test and PCR method. The 73 MRSA strains were classified by staphylococcal cassette chromosome mec (SCCmec) and Staphylococcus protein A (Spa). Sea, sec, seh, sek, seb, seq, sep, Tsst-1, clfA, clfB, fnbA, hla, hld, hlg, lukE, bbp, cna, eap, ebpS, sdrC, sdrD, sdrE, and Pvl genes were also detected in all strains. The χ² test was used for statistical analysis for comparison between groups.

Results

The 181 strains of staphylococci were divided into 97 strains of MRSA, 54 strains of MSSA, and 30 strains of CoNS. 73 MRSA strains were derived from clinical specimens such as lower respiratory tract, secretions, sepsis secreted by tissue infection, urine, and hydrothorax. There were 70 strains that can be identified including SCCmec types and 15 Spa types of all strains, while the most popular types were SCCmecIII-t030 and SCCmecIV-t437 from lower respiratory tract specimens. There were four virulence genes that were detected including seb, seq, clfB, and hld in CoNS strains, while the detection rates of these four virulence genes in Staphylococcus aureus were higher than that of CoNS, and the differences were statistically significant, P < 0.05(P=0.004, P=0.001, P=0.001, P=0.001). 23 virulence genes were detected in 151 strains of Staphylococcus aureus, among which the detection rate of the Tsst-1 gene was the lowest and that of the clfB gene was the highest, and the other genes were 4.6%∼98.0%. The detection rates of sea, sek, seb, seq, sep, cna, eap, ebpS, sdrC, and sdrE virulence genes in MRSA were higher than that of MSSA, and the differences were statistically significant, P < 0.05 (P=0.001, P=0.001, , P=0.001, P=0.001, P=0.009, , P=0.019, P=0.001, , P=0.001, P=0.001, , P=0.003).

Conclusion

The mainly prevalent type of MRSA strains in Jingzhou is SCCmecIII-t030 in lower respiratory tract specimens. Virulence genes of Staphylococcus aureus and antibiotic drug resistance rates are also different from other regions. In this experiment, virulence genes were also detected in CoNS, suggesting that more attention should be paid to the prevention and treatment of these strains clinically.

Mechanisms of high-level fosfomycin resistance in Staphylococcus aureus epidemic lineage ST5

Objectives

Fosfomycin resistance has become a clinical concern. In this study, we analysed the dynamic change of fosfomycin MIC in the epidemic Staphylococcus aureus lineages in a teaching hospital in Shanghai for 12 years and sought to elucidate the major underlying mechanisms.

Methods

MLST was conducted for 4580 S. aureus isolates recovered from 2008 to 2019. Fosfomycin MIC was determined by the agar dilution method. The genome data of 230 S. aureus epidemic lineage isolates were acquired from a next-generation sequencing (NGS) platform. Gene deletion and corresponding complementation mutants were constructed to confirm the mechanism of fosfomycin resistance.

Results

The predominant S. aureus lineages during the past 12 years were ST5 and ST239 (45.6%; 2090/4580). However, ST5 has been spreading clinically, while ST239 has gradually disappeared recently. Consistent with epidemic trends, fosfomycin-resistant ST5 increased from 19.5% to 67.3%. Most fosfomycin-resistant ST5 isolates (92.7%; 647/698) possessed high-level resistance (MIC > 1024 mg/L) with combined mutations mainly in glpT and uhpT. In contrast, fosfomycin-resistant ST239 isolates (76.8%; 149/194) mainly acquired low-level resistance (MIC = 64–128 mg/L) with mutation primarily in hptA. Deletion of a single resistant gene merely resulted in low-level fosfomycin resistance, while double-gene mutants ΔglpTΔuhpT, ΔglpTΔhptA and ΔglpTΔhptR acquired high-level fosfomycin resistance.

Conclusions

The high-level fosfomycin resistance of S. aureus epidemic lineage ST5 is mainly due to the accumulation of mutations in the resistant genes related to membrane transporter systems, and partly contributes to its persistent prevalence under clinical antibiotic pressure.

Methicillin-resistant Staphylococcus aureus of the clonal lineage ST5-SCCmecII-t2460 was associated with high mortality in a Wuhan hospital

Methicillin-resistant Staphylococcus aureus (MRSA) is an important human pathogen that can cause serious infectious diseases. An emerging MRSA strain, ST5-SCCmecII spa-type-t2460 (SMRSA), has spread rapidly since its recent emergence in China, but little information is available about this lineage. In this study, 91 MRSA isolates were collected from patients treated in the Zhongnan Hospital, Wuhan University, from 2018 to 2019, and investigated for their molecular characteristics, antibiotic resistance profiles, and clinical characteristics. The predominant lineage, SMRSA, accounted for 37.4% (34/91) of the isolates, followed by ST239-SCCmecIII-t030 (19.8%, 18/91) and ST59-SCCmecIV-t437 (8.8%, 8/91). In contrast to the latter two non-SMRSA (nSMRSA) lineages, which are among the main MRSA found in Chinese settings, SMRSA exhibited small colony variant (SCV) phenotype and had extremely high resistance rates to erythromycin (100.0%), clindamycin (100.0%), levofloxacin (100.0%), tetracycline (97.1%), moxifloxacin (97.1%), and ciprofloxacin (100%), but was more susceptible to rifampicin (resistance rate 3%). The levels of white blood cells (WBC) and procalcitonin (PCT) and the 30-day mortality in patients infected with SMRSA were (12.54 ± 6.61) × 10⁹/L, 0.66 ng/mL, and 52.9%, respectively, which were much higher than those in patients infected with nSMRSA. In addition, patients infected with SMRSA were more frequently admitted to the intensive care unit (ICU) and submitted to invasive procedures than those infected with nSMRSA. In conclusion, SMRSA showed SCV phenotype and exhibited multiple antibiotic-resistance profiles. In this study, SMRSA was associated with serious infections and poor prognosis. Compared with ST239, ST59, or other nSMRSA strains, patients infected with SMRSA strains have higher 30-day mortality, increased levels of inflammatory biomarkers, and more frequent ICU hospitalization and invasive procedures.

Comparison of the Prevalence of Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMMs) among Staphylococcus aureus Isolates in a Burn Unit with Non-Burning Units

Background:

Staphylococcus aureus (S. aureus) is one of the most important pathogens in burn infections colonized in the nose and increase the risk of infections.

Methods:

Overall, 85 S. aureus isolates were isolated from clinical and nasal hospitalized patients and health care workers (HCWs) in a burn unit and non-burn units in Isfahan from June 2016 and September 2016. Genes encoding penicillin-binding protein 2a (mecA) and adhesive surface proteins, including fibronectin-binding proteins (fnbA,fnbB), fibrinogen binding protein (fib), laminin-binding protein(eno), collagen binding protein (cna), elastin binding protein (ebps), intracellular adhesion operon (icaA and icaD) were detected using PCR method.

Results:

The rate of methicillin-resistant S. aureus (MRSA) among burn and non-burn isolates were 62% (18/29) and 25% (14/56), respectively. The most prevalent MSCRAMMs genes in burn units were eno (86%) and fib (66%). The most common gene pattern in burn center was icaA+fib+eno. The frequency of icaD, fib and ebpS was higher in clinical samples than nasal samples. No relation was found between the MSCRAMMs genes in the burn unit and non-burn units.

Conclusion:

The high prevalence of MRSA in burn center can be a new challenge for clinicians. The higher frequency of icaD, fib and ebpS in clinical isolates than nasal isolates may reflect the important role of these genes in colonization and pathogenesis of S. aureus.

Pathogenic characteristics of Staphylococcus aureus isolates from arthroplasty infections

BACKGROUND

Staphylococcus aureus has a great ability to form biofilms on implant-related biomaterials. This study aimed to investigate the resistance, biofilm and molecular characteristics of S. aureus strains isolated from patients with postoperative infections after arthroplasty in two Chinese tertiary care hospitals during 2017 to 2018.

METHODS

Antimicrobial susceptibility was determined by the agar dilution method. Bacterial biofilm formation was determined by crystal violet staining. The genes related to biofilm formation and molecular typing were analyzed by PCR amplification.

RESULTS

A total of 33 isolates were collected, 21 of which were from Henan. The strains were completely sensitive to vancomycin, linezolid, and nitrofurantoin. All the isolates had adhesion ability and could produce biofilms. Of the isolates, 75.0% from Chongqing and 85.7% from Henan had stronger biofilm formation abilities. The strains from Henan had slightly higher resistance, adhesion and biofilm-forming abilities than those from Chongqing. The strains in both hospitals carried at least two genes related to biofilm formation, and the ica and fnb genes were the most frequently detected genes. Three SCCmec types and seven sequence types (STs) were found in Henan, and two SCCmec types and six STs were found in Chongqing. ST239-SCCmec III was the main epidemic clone in the two hospitals.

CONCLUSION

The resistance phenotype and molecular characteristics of S. aureus strains varied in different hospitals. The results reflect the potential risks of S. aureus infection in postoperative arthroplasty patients. Our study provides a powerful basis for the clinical treatment, infection control and monitoring of outbreaks of epidemic strains.

Molecular Characteristics, Antimicrobial Resistance and Virulence Gene Profiles of Staphylococcus aureus Isolates from Wuhan, Central China

Purpose

This study aimed to investigate the molecular characteristics, antimicrobial resistance and virulence genes profiles of S. aureus isolates from Wuhan, central China.

Materials and Methods

A total of 302 non-duplicate S. aureus isolates were collected successively during January–December 2018 and subjected to multi-locus sequence typing (MLST), staphylococcal protein A (spa) typing and Panton–Valentine leucocidin (PVL) and staphylococcal enterotoxin A, B, C, D, E, G, H and I (sea, seb, sec, sed, see, seg, seh and sei) detection. All methicillin-resistant S. aureus (MRSA) isolates were additionally subjected to staphylococcal chromosomal cassette mec(SCCmec) typing.

Results

Of the 302 S. aureus isolates, 131 were categorised as MRSA, yielding a rate 1.4 times the average rate in China during 2018 (43.4% vs 30.9%). Thirty-one sequence types (STs) and 82 spa types were identified. The most prevalent clones were ST5-t2460 (10.9%), ST239-t030 (9.3%), ST188-t189 (7.9%) and ST59-t437 (6.3%). Notably, the continued prevalence of ST239-t030 in Wuhan differs from other areas in China. SCCmec types and subtypes I, II, III, IVa and V were present in 0.8%, 36.6%, 26.0%, 20.6% and 8.4% of MRSA isolates. A comprehensive analysis identified ST5-t2460-SCCmec II (25.2%,), ST239-t030-SCCmec III (19.8%) and ST59-t437-SCCmec IVa (7.6%) as the major clones among MRSA isolates. The genes pvl, sea, seb, sec, sed, see, seg, seh and sei were detected at respective frequencies of 11.9%, 42.1%, 49.7%, 45.0%, 20.9%, 33.8%, 60.5%, 25.8% and 66.9%.

Conclusion

ST239-t030 remains one of the most prevalent clones in S. aureus isolates from Wuhan, leading us to conclude that S. aureus isolates from Wuhan possess unique molecular characteristics. The S. aureus isolates also exhibit unique antimicrobial resistance profiles and harbour relatively high numbers of enterotoxin virulence genes, compared with other reports from China.

Molecular characteristics and virulence gene profiles of Staphylococcus aureus isolates in Hainan, China

Background

There have been no reports regarding the molecular characteristics, virulence features, and antibiotic resistance profiles of Staphylococcus aureus (S. aureus) from Hainan, the southernmost province of China.

Methods

Two hundred twenty-seven S. aureus isolates, consisting of 76 methicillin-resistant S. aureus (MRSA) and 151 methicillin-susceptible S. aureus (MSSA), were collected in 2013–2014 and 2018–2019 in Hainan, and investigated for their molecular characteristics, virulence genes, antibiotic resistance profiles and main antibiotic resistance genes.

Results

Forty sequence types (STs) including three new STs (ST5489, ST5492 and ST5493), and 79 Staphylococcal protein A (spa) types were identified based on multilocus sequence typing (MLST) and spa typing, respectively. ST398 (14.1%, 32/227) was found to be the most prevalent, and the prevalence of ST398-MSSA increased significantly from 2013 to 2014 (5.5%, 5/91) to 2018–2019 (18.4%, 25/136). Seventy-six MRSA isolates were subject to staphylococcus chromosomal cassette mec (SCCmec) typing. SCCmec-IVa was the predominant SCCmec type, and specifically, ST45-SCCmec IVa, an infrequent type in mainland China, was predominant in S. aureus from Hainan. The antibiotic resistance profiles and antibiotic resistance genes of S. aureus show distinctive features in Hainan. The resistant rates of the MRSA isolates to a variety of antibiotics were significantly higher than those of the MSSA isolates. The predominant erythromycin and tetracycline resistance genes were ermC (90.1%, 100/111) and tetK (91.8%, 78/85), respectively. Eleven virulence genes, including the Panton-Valentine leukocidin (pvl) and eta, were determined, and the frequency of eta and pvl were found to be 57.3 and 47.6%. Such high prevalence has never been seen in mainland China before.

Conclusion

S. aureus isolates in Hainan have unique molecular characteristics, virulence gene and antibiotic resistance profiles, and main antibiotic resistance genes which may be associated with the special geographical location of Hainan and local trends in antibiotic use.

Characterisation of Staphylococcus aureus isolated from rabbits in Fujian, China

Staphylococcus aureus has been recognised as one of the important zoonotic pathogens. However, knowledge about the epidemiology and genetic characteristics of S. aureus in rabbits was limited. The aim of this study was to determine the characteristics of 281 S. aureus isolated from dead rabbits of nine rabbit farms in Fujian Province, China. All the isolates were characterised by multi-locus sequencing typing, detection of virulence factors and antimicrobial susceptibility test. The results showed that the 281 isolates were grouped into two sequence types, ST121 (13.52%, 38/281) and ST398 (86.48%, 243/281). Surprisingly, the ST121 strains were only recovered from the lung samples from one of the nine rabbit farms studied. In the 281 isolates, the virulence genes of nuc, hla, hlb, clfA, clfB and fnbpA were positive, whereas the sea, seb, tsst, eta and etb genes were negative. Notably, the 38 ST121 isolates carried the pvl gene. All the 281 isolates were methicillin-susceptible S. aureus, and the isolates were susceptible to most of the used antibiotics, except for streptomycin, kanamycin, azithromycin and penicillin, and the resistance rates of which were 23.84%, 19.57%, 16.01% and 11.03%, respectively. This study first described the epidemiology and characteristics of S. aureus in rabbits in Fujian Province, which will help in tracking the evolution of epidemic strains and preventing the rabbit-human transmission events.

Phylogenetic analysis and virulence determinant of the host-adapted Staphylococcus aureus lineage ST188 in China

Staphylococcus aureus (S. aureus) is an important pathogen of humans and livestock species, but an understanding of the clonal distribution of S. aureus causing different host-species infections in the same geographical environment and within the same period is lacking. By characterizing infections caused by S. aureus in bovine, pediatric, and adult patients in Shanghai, China, between 2012 and 2014, we identified methicillin-sensitive S. aureus (MSSA) ST188 as the major lineage causing infections in multiple host species. Whole-genome sequencing and phenotypic analyses demonstrated that ST188 might evolve from livestock, and there was no significant genomic or virulence difference between ST188 isolated from livestock and humans. The virulence of ST188 is related to its adhesion and nasal colonization ability. This result is in accord with the strong epithelial cell adhesion and biofilm formation properties of ST188. Furthermore, the adhesion- and biofilm-formation-related genes are present in multiple copies and exhibit significantly increased expression in ST188. In conclusion, S. aureus ST188 is the major lineage causing human and livestock infections in Shanghai, China. Due to its high expression of the factors associated with bacterial adhesion and biofilm formation, ST188 has the ability to colonize and infect different host species.