Resistant Methicillin-resistant Staphylococcus Aureus Research Articles

Isolation and encapsulation of bacteriophage with chitosan nanoparticles for biocontrol of multidrug-resistant methicillin-resistant Staphylococcus aureus isolated from broiler poultry farms

This study was divided into two parts. The first part, the determination of methicillin-resistant Staphylococcus aureus (MRSA) prevalence in 25 broiler chicken farms, with the detection of multidrug resistant MRSA strains. The prevalence of MRSA was 31.8% (159 out of 500 samples) at the level of birds and it was 27% (27 out of 100) in the environmental samples. The highest antimicrobial resistance of the recovered MRSA strains was recorded to streptomycin (96%). All isolates (100%) had multidrug resistance (MDR) to four or more antibiotics with 16 distinct antibiotic resistant patterns, and multiple antibiotic resistance index (MARI) of 0.4–1. The second part, implementing novel biocontrol method for the isolated multidrug resistant MRSA strains through the isolation of its specific phage and detection of its survival rate at different pH and temperature degrees and lytic activity with and without encapsulation by chitosan nanoparticles (CS-NPs). Encapsulated and non-encapsulated MRSA phages were characterized using transmission electron microscope (TEM). Encapsulation of MRSA phage with CS-NPs increasing its lytic activity and its resistance to adverse conditions from pH and temperature. The findings of this study suggested that CS-NPs act as a protective barrier for MRSA phage for the control of multidrug resistant MRSA in broiler chicken farms.

Optical Mapping: Detecting Genomic Resistance Cassettes in MRSA.

Methicillin-resistant Staphylococcus aureus (MRSA) is a multidrug-resistant bacterium with a global presence in healthcare facilities as well as community settings. The resistance of MRSA to beta-lactam antibiotics can be attributed to a mobile genetic element called the staphylococcal cassette chromosome mec (SCCmec), ranging from 23 to 68 kilobase pairs in length. The mec gene complex contained in SCCmec allows MRSA to survive in the presence of penicillin and other beta-lactam antibiotics. We demonstrate that optical mapping (OM) is able to identify the bacterium as S. aureus, followed by an investigation of the presence of kilobase pair range SCCmec elements by examining the associated OM-generated barcode patterns. By employing OM as an alternative to traditional DNA sequencing, we showcase its potential for the detection of complex genetic elements such as SCCmec in MRSA. This approach holds promise for enhancing our understanding of antibiotic resistance mechanisms and facilitating the development of targeted interventions against MRSA infections.

Antibiotic resistance’s of Staphylococcus aureus strains isolated at Hue University Hospital of Medicine and Pharmacy (3/2022 - 3/2023)

Background: Staphylococcus aureus is one of the major causes of infections in hospitals. Many studies have pointed out the fact that Staphylococcus aureus is resistant to many antibiotics, especially Methicillin-Resistant Staphylococcus aureus (MRSA). Objectives: To determine the frequency of Staphylococcus aureus and the frequency of the antibiotic resistance of S. aureus strains isolated at Hue University Hospital of Medicine and Pharmacy in 2022. Materials and methods: A cross-sectional descriptive study on S. aureus strains isolated at Hue University Hospital of Medicine and Pharmacy from March 2022 to March 2023, determining antibiotic resistance by Kirby-Bauer technique. Results: The frequency of S. aureus infections is 18.0%. The frequency of MRSA infections was 61.7%, the antibiotic resistance rates of S. aureus strains were the highest in the beta-lactam antibiotic group (61.7%-95.8%), followed by erythromycin 65.1%, clindamycin (59.9%). The rates of resistance of MRSA to penicillin, erythromycin, clindamycin, trimethoprim-sulfa antibiotics were higher than that of MSSA and this difference was statistically significant (p < 0.05). The rate of multi-resistance to over 6 antibiotics of MRSA accounted for 9.3%. Conclusion: The frequency of S. aureus infections was 18.0%. The rate of MRSA accounts for 61.7%, the rate of multi-antibiotic resistant MRSA (over 6 antibiotics) was low, with 9.3%. Key words: Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus, Atibiotic Resistance.

Exploiting the synergistic antibacterial activity of shikimic acid and ceftiofur against methicillin-resistant Staphylococcus aureus.

Efforts to curtail the escalating health threat posed by methicillin-resistant Staphylococcus aureus (MRSA), a formidable superbug, necessitate the development of innovative treatment strategies. Leveraging potential compounds from natural sources in tandem with antibiotics has emerged as a promising approach against MRSA. These strategies should enhance the antibiotic efficacy, reduce dosage and toxicity, and bypass MRSA resistance. In this study, we used a checkerboard assay to illustrate the significant synergistic anti-MRSA effect of shikimic acid (SA), a naturally occurring compound, and ceftiofur (CF). Time-kill curves further revealed that a combination of 1/4 of the minimum inhibitory concentration (MIC) of SA and 1/8 MIC of the sodium CF eradicated MRSA within 2h, with no noticeable toxicity observed with these concentrations. In vivo experiments confirmed that this combination therapy demonstrated robust antimicrobial activity against MRSA-induced bacteremia in mice, significantly reducing bacterial loads in the kidneys, liver, and spleen, attenuating inflammatory cell infiltration, and alleviating pathological damage. This study not only offers a compelling strategy, capitalizing on the synergistic potential of SA and CF, to rapidly address antibiotic resistance but also contributes significantly to the refinement of antimicrobial therapeutic strategies.

Clindamycin Resistance Detection among MRSA at a Tertiary Care Hospital: A Cross-sectional Study

Introduction: Antimicrobial resistance is on the rise, posing a global threat to the success of modern surgical procedures. A common and notorious superbug causing community and hospital-acquired infections is Methicillin-resistant Staphylococcus aureus (MRSA). Its potential for easy and rapid spread leads to increased mortality in hospitals. Clindamycin, a relatively inexpensive and effective drug, is empirically prescribed for the treatment of MRSA infections. Due to the risk of misidentifying clindamycin resistance as susceptibility, leading to treatment failure, its judicious use after D-test is advocated. Aim: To isolate Staphylococcus aureus (S.aureus) from various clinical specimens and to identify MRSA using cefoxitin disc (30 μg), further determining the incidence of inducible clindamycin resistance among MRSA by the disc diffusion method (D-test). Materials and Methods: The present cross-sectional study was conducted in the Department of Microbiology, Government Mohan Kumaramangalam Medical College Hospital (GMKMCH), Salem, Tamil Nadu, India, from June 2023 to August 2023. Study was conducted using 185 S.aureus isolates collected from samples received from patients of all genders treated at the present study hospital. Various clinical samples such as pus, sputum, blood, urine and fluids collected from patients treated at the study Institute Salem during the study period were included. A cefoxitin disc (30 μg) was used to detect MRSA among the 185 S.aureus isolates by disc diffusion method as per Clinical and Laboratory Standards Institute (CLSI) guidelines, which were further tested for clindamycin resistance using clindamycin (2 μg) with erythromycin (15 μg) discs by the D-test. The data of the study were analysed using Statistical Package for the Social Sciences (SPSS) software version 21.0. Further descriptive statistics and a chi-square test with a level of significance, p-value ≤0.005 (statistically significant), were used. Results: Among 185 S.aureus isolates, 130 (70.27%) were Methicillin-sensitive S.aureus (MSSA) and 55 (29.7%) were MRSA. Inducible clindamycin resistance was observed in 22 (40%) isolates, while 17 (30.9%) isolates showed constitutive resistance, 9 (16.36%) showed the MS phenotype, and the remaining 7 (12.72%) showed the susceptible phenotype. Among the clindamycin resistance patterns in MRSA, inducible clindamycin resistance was reported predominantly. Conclusion: The majority of S.aureus was isolated from pus samples, highlighting its importance as a pyogenic microorganism. The current study records a high rate of MRSA resistance among S.aureus isolates. The present study reports a higher rate of inducible clindamycin resistance among MRSA isolates when compared to other phenotypes of clindamycin resistance. Therefore, routine D-testing must be implemented to identify inducible resistance to clindamycin in MRSA to avoid treatment failure.

Medicinal Remedies for the Treatment of Methicillin Resistant Staphylococcus Aureus

Antimicrobial resistance has led to the rise of formidable microbes like methicillin-resistant Staphylococcus aureus (MRSA). This infection can be acquired at the hospital and in a community, making the search for efficient treatment critical, given the rise in inefficacy of conventional treatments such as vancomycin. Phytocompounds can offer protection against these threats. They not only have the ability to kill MRSA but also enhance its susceptibility to previously ineffective antimicrobial agents. Plant-derived anti-MRSA agents can produce therapeutic effects comparable to some conventional treatments, and in some cases, they may even outperform an antibiotic. This article provided many examples of botanical compounds that have proven potent agents against MRSA in both in vitro and in vivo studies. These compounds achieve these effects by inhibiting the resistance mechanisms in MRSA, breaking down its defenses, making it vulnerable, and eventually killing it. Many of these compounds are inherently bactericidal; however, they may produce a synergistic response when combined with allopathic antibiotics. For example, plumbagin, from Plumbago zeylanica, not only disrupts MRSA cell wall morphology, eliciting cytoplasmic changes but also produces a synergistic effect with ciprofloxacin and piperacillin. Moreover, honokiol and magnolol glycosides, from Magnolia officinalis, reversed the quintessential resistance of MRSA by repressing genes, responsible for resistance development. The possibilities are indeed endless, but further research and financial investments are required for proper drug development.

Evaluation of In-Vitro Activity of Ceftaroline Against Methicillin-Resistant Staphylococcus aureus Clinical Isolates.

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the major causes of hospital and community-acquired infections. Fewer drugs, such as vancomycin, teicoplanin, and daptomycin, are effective against it, but they come with high toxicity. Fifth-generation cephalosporins like ceftaroline and second-generation cefuroxime are effective against MRSA. Limited studies are available on ceftaroline resistance in the literature. This study was undertaken to determine ceftaroline resistance in MRSA in a tertiary care hospital in Eastern India. A cross-sectional, hospital-based study was carried out with MRSA isolates obtained from various clinical samples of patients. Identification of the isolates to the species level was performed by an automated Vitek system, and selected samples were genotypically confirmed by detecting the mecA gene via real-time PCR. Out of a total of 334 Staphylococcus aureus isolates examined in this study, the prevalence of MRSA was seen in 59.3% (198/334), and methicillin-sensitive Staphylococcus aureus was in 40.7% (136/334). Of the total 198 MRSA isolates, ceftaroline intermediate MRSA was seen in 8.6% (17/198), and ceftaroline sensitive MRSA was in 91.4% (181/198), respectively. Among the 17 ceftaroline intermediate MRSA isolates, 88.2% (15/17) showed aminimum inhibitory concentration (MIC) of 2 µg/ml, and 11.8% (2/17) showed an MIC of 3 µg/ml. All the remaining 91.4% (181/198) isolates were sensitive to ceftaroline and showed an MIC ≤1 µg/ml. Real-time PCR confirmed the presence of the mecA gene in MRSA isolates. In this present study, not a single isolate was resistant to ceftaroline, suggesting that it, being a safer drug, can be used in place of glycopeptides such as vancomycin or teicoplanin and linezolid, where resistance has already been detected. The rational use of ceftaroline could be useful in clinical settings, and further studies will confirm the findings.

Superior Performance of Iron-Coated Silver Nanoparticles and Cefoxitin as an Antibiotic Composite Against Methicillin-Resistant Staphylococcus aureus (MRSA): A Population Study.

The synergistic effects of antimicrobial nanostructures with antibiotics present a promising solution for overcoming resistance in methicillin-resistant Staphylococcus aureus (MRSA). Previous studies have introduced iron as a novel coating for silver nanoparticles (AgNPs) to enhance both economic efficiency and potency against S. aureus. However, there are currently no available data on the potential of these novel nanostructures to reverse MRSA resistance. To address this gap, a population study was conducted within the MRSA community, collecting a total of 48 S. aureus isolates from skin lesions. Among these, 21 isolates (43.75%) exhibited cefoxitin resistance as determined by agar disk diffusion assay. Subsequently, a PCR test confirmed the presence of the mecA gene in 20 isolates, verifying them as MRSA. These results highlight the cefoxitin disk diffusion susceptibility test as an accurate screening method for predicting mecA-mediated resistance in MRSA. Synergy tests were performed on cefoxitin, serving as a marker antibiotic, and iron-coated AgNPs (Fe@AgNPs) in a combination study using the checkerboard assay. The average minimal inhibitory concentration (MIC) and fractional inhibitory concentration (FIC) of cefoxitin were calculated as 11.55mg/mL and 3.61mg/mL, respectively. The findings indicated a synergistic effect (FIC index < 0.5) between Fe@AgNPs and cefoxitin against 90% of MRSA infections, while an additive effect (0.5 ≤ FIC index ≤ 1) could be expected in 10% of infections. These results suggest that Fe@AgNPs could serve as an economically viable candidate for co-administration with antibiotics to reverse resistance in MRSA infections within skin lesions. Such findings may pave the way for the development of future treatment strategies against MRSA infections.

Profiling daptomycin resistance among diverse methicillin-resistant Staphylococcus aureus lineages in China.

Daptomycin (DAP) is effective against methicillin-resistant Staphylococcus aureus (MRSA). However, reduced susceptibility to DAP in MRSA may lead to treatment failures. We aim to determine the distribution of DAP minimum inhibitory concentrations (MICs) and DAP heteroresistance (hDAP) among MRSA lineages in China. A total of 472 clinical MRSA isolates collected from 2015 to 2017 in China were examined for DAP susceptibility. All isolates (n = 472) were found to be DAP susceptible, but 35.17% (166/472) of them exhibited a high DAP MIC (MIC >0.5 µg/mL). The high DAP MIC group contained a larger proportion of isolates with a higher vancomycin or teicoplanin MIC (>1.5 µg/mL) than the low DAP MIC group (19.3% vs 7.8%, P < 0.001; 22.3% vs 8.2%, P < 0.001). We compared the clonal complex (CC) distributions and clinical characteristics in MRSA isolates stratified by DAP MIC. CC5 isolates were less susceptible to DAP (MIC50 = 1 µg/mL) than CC59 isolates (MIC50 = 0.5 µg/mL, P < 0.001). Population analysis profiling revealed that 5 of 10 ST5 and ST59 DAP-susceptible MRSA isolates investigated exhibited hDAP. The results also showed that CC5 MRSA with an agrA mutation (I238K) had a higher DAP MIC than those with a wild-type agrA (P < 0.001). The agrA-I238K mutation was found to be associated with agr dysfunction as indicated by the loss of δ-hemolysin production. In addition, agr/psmα defectiveness was associated with hDAP in MRSA. Whole-genome sequencing analysis revealed mutations in mprF and walR/walK in DAP-resistant subpopulations, and most DAP-resistant subpopulations (6/8, 75%) were stable. Our study suggests that the increased DAP resistance and hDAP in MRSA may threaten the effectiveness against MRSA infections.

The origin of sequence type 72 community-associated methicillin-resistant Staphylococcus aureus (MRSA) and fusidic acid (FA) resistant sequence type 5 MRSA: Analysis of FA resistance and spa type in a single center in South Korea

IntroductionWe investigated the prevalence of fusidic acid (FA) resistance in MSSA and MRSA stratified by sequence (ST) and spa types, and determined the prevalence of FA resistance mechanisms. MethodsFrom August 2014 to April 2020, S. aureus blood isolates were collected in Asan Medical Center, Seoul, South Korea. Antimicrobial susceptibility tests were performed using broth microdilution and interpreted according to EUCAST's FA criteria. We performed spa typing for fusA mutation presence and acquired FA resistance determinants (fusB, fusC, and fusD) by PCR. ResultsOf the 590 MRSA isolates, 372 were FA resistant, and among 425 MSSA isolates, 136 were resistant. Of the 380 ST5-MRSA isolates, 350 were FA resistant, whereas only 1 of 14 ST5-MSSA isolates was FA resistant. Conversely, of the 163 ST72-MRSA isolates, only 8 were resistant, whereas 37 of 42 ST72-MSSA were resistant. The fusA mutation (80%) was the most common determinant. The one FA resistant ST5-MSSA isolate belonged to the t2460 spa type, the most common spa type (24 of 35 isolates) of FA resistant ST5-MRSA. In addition, t324 and t148, which are minor spa types of ST72-MSSA, were susceptible to FA, in contrast to other ST72-MSSA spa types, and the major spa type of ST72-MRSA (110 of 163 isolates). ConclusionsFA resistance was common in ST5-MRSA and ST72-MSSA, and rare in ST5-MSSA and ST72-MRSA. Our findings suggest that minor clones of ST5-MSSA isolates, with the fusA mutation and minor clones of ST72-MSSA susceptible to FA, may have evolved to harbor the mecA gene.

Resensitisation of Methicillin-Resistant Staphylococcus aureus to Conventional Antibiotics in the Presence of an Engineered Enzybiotic.

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most dreadful pathogens relevant in community and nosocomial-related infections around the world. Resensitising MRSA to antibiotics, once it became resistant, was a tough choice due to the high adaptability of this bacteria to savage conditions. This study aimed to create a chimeric enzybiotic against MRSA and test its efficiency, either individually or in combination with antibiotics. The novel enzybiotic BAC100 was constructed by fusing the catalytic domain from the bacteriocin BacL1 from Enterococcus faecalis with the cell-wall-binding domain from protein P17 of Staphylococcus aureus bacteriophage ϕ44AHJD. Apart from its partial lone activity, BAC100 was found to resensitise the MRSA strain to traditional antibiotics, including ampicillin and tetracycline. Both drugs were able to reduce live MRSA cells by 85 and 90%, respectively, within 60 min of treatment together with BAC100. However, no significant activity was observed against MRSA when these drugs were tested independently, pointing to the inherent resistance of MRSA against these conventional antibiotics. To our knowledge, this is one of the first instances where an engineered enzybiotic was found to resensitise MRSA to conventional antibiotics. This study will pave the way for the development of similar peptides that can be used together with antibiotics against gruesome pathogens of clinical importance.

2,4-Diacetylphloroglucinol (DAPG) derivatives rapidly eradicate methicillin-resistant staphylococcus aureus without resistance development by disrupting membrane

Methicillin-resistant Staphylococcus aureus (MRSA) causes severe public health challenges throughout the world, and the multi-drug resistance (MDR) of MRSA to antibiotics necessitates the development of more effective antibiotics. Natural 2,4-diacetylphloroglucinol (DAPG), produced by Pseudomonas, displays moderate inhibitory activity against MRSA. A series of DAPG derivatives was synthesized and evaluated for their antibacterial activities, and some showed excellent activities (MRSA MIC = 0.5–2 μg/mL). Among these derivatives, 7g demonstrated strong antibacterial activity without resistance development over two months. Mechanistic studies suggest that 7g asserted its activity by targeting bacterial cell membranes. In addition, 7g exhibited significant synergistic antibacterial effects with oxacillin both in vitro and in vivo, with a tendency to eradicate MRSA biofilms. 7g is a promising lead for the treatment of MRSA.

Ayanin, a natural flavonoid inhibitor of Caseinolytic protease, is a promising therapeutic agent to combat methicillin-resistant Staphylococcus aureus infections

Antimicrobial resistance (AMR) is a global health threat. The dramatic increase of Methicillin-resistant Staphylococcus aureus (MRSA) infections emphasizes the need to find new anti-infective agents with a novel mode of action. The Caseinolytic protease (ClpP) is a central virulence factor in stress survival, virulence, and antibiotic resistance of MRSA. Here, we found ayanin, a flavonoid isolated from Callicarpa nudiflora, was an inhibitor of MRSA ClpP with an IC50 of 19.63 μM. Using quantitative real-time PCR, ayanin reduced the virulence of Staphylococcus aureus (S. aureus) by down-regulating the level of some important virulence factors, including agrA, RNAⅢ, hla, pvl, psmα and spa. The results of cellular thermal shift assay and thermal shift assay revealed a binding between ayanin and ClpP. Molecular docking showed that ASP-168, ASN-173 and ARG-171 were the potential binding sites for ClpP binding to ayanin. ClpP mutagenesis study further indicated that ARG-171 and ASN-173 were the main active sites of ClpP. The affinity constant (KD) value of ayanin with ClpP was 3.15 × 10−5 M measured by surface plasmon resonance. In addition, ayanin exhibited a significant therapeutic effect on pneumonia infection induced by S. aureus in mice in vivo, especially in combination with vancomycin. This is the first report of ayanin with in vivo and in vitro efficacy against S. aureus infection. In conclusion, ayanin is a promising therapeutic agent to combat MRSA infections by targeting ClpP.

Detection of Methicillin-resistant Staphylococcus aureus (MRSA) resistant to vancomycin and linezolid in bulk tank milk by E-test method

Staphylococcus aureus is considered a serious threat to public health, besides is one of the most common causes of subclinical mastitis in dairy cows. Therefore, especially methicillin-resistant Staphylococcus aureus (MRSA) is among the most critical reasons for antibiotic treatment. Monitoring the antibiotic resistance of MRSA from livestock animals and foods is of great significance. The E-test method is a suitable option for detecting antibiotics' minimum inhibition concentration (MIC) value because it is an easy and fast assay to perform. This study aimed to detect vancomycin, teicoplanin, and linezolid resistance of milk-borne 34 MRSA isolates with subclinical mastitis by the E-test method to determine MIC values. The study determined that 8.8% of MRSA isolates isolated from milk with subclinical mastitis were also resistant to vancomycin and 11.7% to linezolid, while none of the isolates were determined to be resistant to teicoplanin, according to EUCAST. The data obtained from the study reveal that the efficacy of vancomycin and linezolid antibiotics, which are commonly used against MRSA infections, are in danger. Especially before MRSA treatment, MIC values of antibiotics should be determined, and appropriate antibiotics should be used in effective doses.

HptA Mutation May Mediate Fosfomycin Resistance in Methicillin-Resistant Staphylococcus aureus Clinical Isolates.

Fosfomycin can be used alone or in combination to treat methicillin-resistant Staphylococcus aureus (MRSA) infection. However, fosfomycin resistance has been observed in MRSA. In S. aureus, fosfomycin resistance is mediated by the fosfomycin-modifying enzyme FosB, or mutations in the target enzyme MurA. Mutations in the chromosomal glpT and uhpT genes, which encode fosfomycin transporters, also result in fosfomycin resistance. The three-component regulatory system HptRSA mediates the expression of uhpT and glpT in S. aureus. This study aimed to investigate the role of hptRSA mutation in fosfomycin resistance in MRSA clinical isolates. We found that hptRSA mutations were common in MRSA strains isolated from our hospital. Most mutations were amino acid substitutions and widely distributed in fosfomycin-sensitive and fosfomycin-resistant strains. However, HptA-truncated mutations were only found in fosB-negative fosfomycin-resistant strains with wild-type uhpT and glpT genes. Quantitative real-time PCR results showed that the transcription level of uhpT decreased by 13.7-25.6-fold in the HptA-truncated strains. Concordantly, the fosfomycin minimum inhibitory concentration (MIC) of HptA-truncated strains was 64-128 μg/mL, while SA240 was 2 μg/mL. The low transcription level of uhpT and high increase in MIC suggest that hptA mutation may lead to fosfomycin resistance in MRSA. We complemented hptA in one of the HptA-truncated clinical strains (SA179), showing reversal of fosfomycin resistance (from 128 to 32 μg/mL). Then we knocked out hptA in S. aureus Newman; fosfomycin MIC increased from 4 to 64 μg/mL, suggesting that HptA mutation may play an important role in fosfomycin resistance.

Whole genome characterization of methicillin resistant Staphylococcus aureus in an Egyptian Tertiary Care Hospital.

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant healthcare-associated (HA-MRSA) pathogen due to its increased morbidity and mortality rates. There is a paucity of data regarding MRSA clones circulating in the Middle East in the literature, especially from Egypt. We aimed to identify the pattern of resistance and virulence in the propagating clones using NGS technologies for the whole genome sequence. From an 18-month surveillance program for MRSA-positive patients, 18 MRSA isolates from surgical healthcare associated infections were selected. The Vitek2 system was used to assess antimicrobial susceptibility. The whole genome sequencing was performed using the NovaSeq6000. The reads were mapped to the reference genome (Staphylococcus_aureus_ATCC_BAA_1680), used for variant calling, screened for virulence/resistance genes, and typed using multi-locus sequence typing and spa typing. Correlation between demographic and clinical data and molecular findings were performed. All the MRSA isolates were highly resistant to tetracycline followed by gentamicin (61%) and highly susceptible to trimethoprim/sulfamethoxazole. Most of the isolates showed a high virulence profile. ST239 was the predominant sequence type (6/18), while t037 was the predominant spa type (7/18). Five isolates shared the same ST239 and spa t037. ST1535, an emerging MRSA strain, was the second most prevalent in our study. One isolate showed a unique pattern of a high abundance of resistance and virulence genes. WGS elucidated the resistance and virulence profiles of MRSA isolated from clinical samples of HAI patients with high-resolution tracking of clones predominant in our healthcare facility.

DNA Nanoflower Eye Drops with Antibiotic-Resistant Gene Regulation Ability for MRSA Keratitis Target Treatment.

Methicillin-resistant Staphylococcus aureus (MRSA) biofilm-associated bacterial keratitis is highly intractable, with strong resistance to β-lactam antibiotics. Inhibiting the MRSA resistance gene mecR1 to downregulate penicillin-binding protein PBP2a has been implicated in the sensitization of β-lactam antibiotics to MRSA. However, oligonucleotide gene regulators struggle to penetrate dense biofilms, let alone achieve efficient gene regulation inside bacteria cells. Herein, an eye-drop system capable of penetrating biofilms and targeting bacteria for chemo-gene therapy in MRSA-caused bacterial keratitis is developed. This system employed rolling circle amplification to prepare DNA nanoflowers (DNFs) encoding MRSA-specific aptamers and mecR1 deoxyribozymes (DNAzymes). Subsequently, β-lactam antibiotic ampicillin (Amp) and zinc oxide (ZnO) nanoparticles are sequentially loaded into the DNFs (ZnO/Amp@DNFs). Upon application, ZnO on the surface of the nanosystem disrupts the dense structure of biofilm and fully exposes free bacteria. Later, bearing encoded aptamer, the nanoflower system is intensively endocytosed by bacteria, and releases DNAzyme under acidic conditions to cleave the mecR1 gene for PBP2a down-regulation, and ampicillin for efficient MRSA elimination. In vivo tests showed that the system effectively cleared bacterial and biofilm in the cornea, suppressed proinflammatory cytokines interleukin 1β （IL-1β） and tumor neocrosis factor-alpha （TNF-α）, and is safe for corneal epithelial cells. Overall, this design offers a promising approach for treating MRSA-induced keratitis.

Bacteriology and trends of antimicrobial resistance of Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus in otitis media: A retrospective data analysis.

Otitis media (OM) has a high prevalence worldwide and the treatment is crucial because hearing loss in children can lead to growth disorders such as language development disorders. The aim of this study is to analyse the changes in bacterial strains and the trends of antibiotic susceptibility in otitis media with effusion (OME), chronic otitis media (COM) and cholesteatomatous otitis media (Chole OM). This retrospective study involved 2926 patients diagnosed with OME, COM, or Chole OM between January 2000 and December 2020. The clinical data were collected and analysed through chart review from May 2021 to July 2021. Two tertiary medical centres. The 2926 OM patients. An otorrhea sample was collected on the first day of their hospital visit. Middle ear fluid samples for bacterial culture and antibiotics susceptibility test were collected from patients during middle ear surgery, including ventilation tube insertion. In each type of OM, the distribution of bacterial strains in the 2000s and the 2010s was compared. In addition, changes in the detection rate of methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PA) and trends in their antibiotic susceptibility over the last 10 years were analysed. The most frequently detected bacterial strains in OME, COM and Chole OM over the study period were coagulase-negative Staphylococcus (CNS) (29.6%), MRSA (24.1%), and PA (20.1%). Compared to the 2000s, the proportion of non-typable Haemophilus influenzae in OME and MRSA in COM increased in the 2010s (27.4%-31.6% and 1.5%-29.5%, respectively). In total three types of OM, although there was no significant trend of change in detection rates of MRSA, PA, and multidrug resistant-P. aeruginosa (MDR-PA) during the last 10 years, resistance to the Quinolone class of MRSA and PA tended to increase (P < .05). The composition of bacterial strains in each types of OM has changed over the past 20 years. Additionally, the antibiotic resistance of MRSA and PA has increased in the last decade. Therefore, when using empirical antibiotics in necessary situations, it is necessary to change to an appropriate antibiotic through a bacterial culture test and antimicrobial susceptibility test.

Hybrid Biomimetic Membrane Coated Particles-Mediated Bacterial Ferroptosis for Acute MRSA Pneumonia.

Acute methicillin resistant Staphylococcus aureus (MRSA) pneumonia is one of the most frequently seen lung infection diseases with high morbidity and mortality. It is urgent to explore an efficient antibacterial strategy owing to the increase of drug resistance, virulence, and pathogenicity of MRSA. It was found that Fe3O4 can induce ferroptosis in MRSA, but its effect was inhibited by glutathione (GSH) to a certain extent, while cinnamaldehyde (CA) can enhance ferroptosis by consuming GSH. As a bacterial quorum sensing (QS) inhibitor, CA can suppress the QS system and further exert its antibacterial and antibiofilm effects. Here, we developed an Fe3O4-based ferroptosis inducer to promote ferroptosis in MRSA, interrupt the QS, destroy biofilm, and thus effectively treat acute MRSA pneumonia. We used sodium alginate (SA) to wrap Fe3O4 and CA to form particles, and then coated the surface with a hybrid biomimetic membrane composed of an erythrocyte membrane and platelet membrane to obtain lung targeted antibacterial particles (mFe-CA). Under ultrasonic (US) stimulation, mFe-CA can efficiently release Fe3O4 and CA, thereby synergically inducing MRSA death with the characteristics of ferroptosis, including mass ROS production, lipid peroxidation, GSH depletion, and respiratory chain suppression. Furthermore, mFe-CA + US can inhibit the QS system, remove biofilms, and reduce strain virulence. In the mouse model of MRSA pneumonia, mFe-CA + US treatment markedly advanced the survival rate of the mice, reduced the bacterial load in the lungs, and alleviated the inflammatory damage, but there was no obvious toxicity. This study proposes an antibacterial substitute to induce ferroptosis of MRSA, which may provide a foreground for overcoming microbial drug resistance and fighting biofilm-associated infections and also provides a target and theoretical basis for clinical treatment of acute MRSA pneumonia.

Molecular Surveillance of MRSA in Raw Milk Provides Insight into MRSA Cross Species Evolution.

Methicillin-resistant Staphylococcus aureus (MRSA) in foods has been associated with severe infections in humans and animals worldwide. In the present study, the molecular characteristics of livestock-associated MRSA (LA-MRSA) and human-associated MRSA (hMRSA) isolates obtained in China, as well as MRSA isolates obtained from raw milk in 2018, were investigated. In total, 343 (20.38%; 343/1,683) S. aureus isolates were obtained from 1,683 raw milk samples from 100 dairy farms in 11 provinces across China. Among these, 49 (2.91%; 49/1,683) were mecA-positive MRSA. All LA-MRSA isolates were resistant to penicillin and highly resistant to erythromycin, sulfisoxazole, and clindamycin. Bioinformatic analysis the 49 genomes of LA-MRSA and 71 previously published hMRSA genomes isolated from Chinese individuals in 2018 indicated that blaZ, erm, ant(6)-Ia, aph(3')-III, tet(K), cat, and aph(2″)-Ia were more prevalent in MRSA from raw milk (P < 0.05) compared to hMRSA. Additionally, hMRSA isolates were more significantly associated with ST5 (P < 0.01) compared to LA-MRSA; in contrast, ST338 was more prevalent among LA-MRSA isolates (P < 0.01). Likewise, the SCCmec type II was only detected in hMRSA isolates, whereas SCCmec type V and IV were more prevalent among LA-MRSA (P < 0.01). Furthermore, core-genome phylogenetic analysis showed the endemic characteristics of LA-MRSA in local provinces, as well as the close evolutionary relationships between MRSA from cattle and humans. Finally, homology analysis of mecA and blaZ genetic contexts revealed a high possibility of horizontal transmission of MRSA resistance genes among raw milk-associated and hMRSA strains, which increases the risk for public health. IMPORTANCE Methicillin-resistant Staphylococcus aureus (MRSA) is considered a public health concern as it is resistant to multiple antibiotics, thus being in zoonotic transmission of antibiotic resistance genes. MRSA causes serious public health issues and leads to hard-to-treat infections in humans and animals; therefore, it was meaningful to determine the prevalence of MRSA in raw milk samples and investigate phenotype and genotype of antimicrobial resistance and molecular characteristics in livestock-associated MRSA (LA-MRSA) and human-associated MRSA (hMRSA) in China, which could provide a theoretical basis for preventing and controlling the spread of MRSA between livestock and humans.