Occurrence of vancomycin MIC creep in methicillin resistant isolates in Saudi Arabia

Pharmacophore modeling, 2D-QSAR, molecular docking and ADME studies for the discovery of inhibitors of PBP2a in MRSA

Methicillin-resistant Staphylococcus aureus (MRSA) is considered to be a worldwide threat to human health and the global spread of MRSA has been associated with the emergence of different types of infections and resultant selection pressure due to exposure to many antibiotics. In the current era characterized by incessant antibiotic resistance, assessment of multiple molecular targets represents notable therapeutic opportunities in the medical and pharmaceutical industry and can aid in the discovery of novel molecules that inhibit various receptors effectively to replace the current weak antimicrobial agents. Penicillin binding protein 2a (PBP2a) of MRSA is a major determinant of resistance to β-lactam antibiotics. The activity of PBP2a is not inhibited by β-lactam antibiotics, allowing the strain to survive in the presence of β-lactams leading to resistance to β-lactam antibiotics. The study aimed at identifying potential inhibitors of PBP2a receptor of MRSA through ligand-based pharmacophore modeling, 2D-QSAR, molecular docking, ADMET screening as well as molecular dynamic (MD) simulations. The study led to the development of a satisfactory, predictive and significant 2D-QSAR model for predicting anti-MRSA activity of compounds and also led to the identification of two molecules: C21H25N7O4S2 (ChEMBL30602) and C20H17NO6S (ChEMBL304837) with favorable pharmacophore features and ADME properties with potential to bind strongly to PBP2a receptor of MRSA. MD simulation analysis showed that the interactions of C20H17NO6S (ChEMBL304837) with PBP2a over 100 ns was more stable and similar to the interaction of ceftobiprole with PBP2a and may become potential drug candidate against MRSA which has developed a lot of resistance to current antibiotics.

Guardians of resistance and virulence: detection of mec, femA, Van, pvl, hlg and spa genes in methicillin and vancomycin-resistant Staphylococcus aureus from clinical and food samples in Southwestern Nigeria

BACKGROUND

Staphylococcus aureus strains are highly virulent and associated with an eclectic range of severe nosocomial and community-acquired infections.

OBJECTIVES

This study assessed methicillin- and vancomycin-resistant Staphylococcus aureus (MRSA/VRSA) from clinical and ready-to-eat (RTE) food sources, screened for antibiotic resistance; and molecular determinants of antibiotic and virulence genes.

METHODS

Altogether, 465 clinical and RTE food samples were analyzed via conventional microbiological techniques and S. aureus identification was confirmed by nuc gene detection. Phenotypic screening for methicillin and vancomycin-resistance was by agar-screen cum micro-broth dilution respectively, while antibiotic susceptibility testing was done by the disc-diffusion technique. VanA/vanB/VanC1, femA, mecA/mecC; pvl/hlg and spa gene detection was via Polymerase chain reaction.

RESULTS

Phenotypically, 211 Staphylococcal isolates were recovered, 138 (65.4%) of them carrying the nuc gene - all 138 (100.0%) were VRSA, while 59/138 (42.8%) were MRSA phenotypically. Overall, 114/138 (82.6%), 7/138 (5.1%), and 6/138 (4.3%) of isolates had the femA, mecA, and mecC genes, while van genes were detected in only 3 (2.2%) isolates, with virulence determinants pvl, hlg, and spa gene carriage in 8 (5.8%), 10 (7.2%), and 77 (55.8%) isolates respectively. In all, 11.6% carried resistance-associated genes, 55.8% carried virulence genes, and co-detection of resistance and virulence genes was observed in 12.3%. Overall, 96/138 (69.6%) were multidrug-resistant (MDR), while one strain was extremely drug-resistant (XDR). MAR Indices ≥ 0.2 was observed in 83.3% of isolates.

CONCLUSION

This study highlights virulence levels of MRSA and VRSA circulating strains in Osogbo, contributing to their sustained surveillance, and improving available data for successive epidemiology investigations. This study also reports the occurrence of the mecC gene in S. aureus isolates from RTE foods and human samples in Southwestern Nigeria.

Effect of low vs. high vancomycin trough level on the clinical outcomes of adult patients with sepsis or gram-positive bacterial infections: a systematic review and meta-analysis

BACKGROUND & OBJECTIVE

The Infectious Disease Society of America guidelines recommend vancomycin trough levels of 15-20 mg/L for severe methicillin-resistant Staphylococcus aureus. However, recent consensus guidelines of four infectious disease organizations no longer recommend vancomycin dosing using minimum serum trough concentrations. Therefore, this study aimed to evaluate the impact of low (< 15 mg/L) vs. high (≥ 15 mg/L) vancomycin trough levels on clinical outcomes in adult patients with sepsis or gram-positive bacterial infections.

METHOD

A systematic literature review from inception to December 2022 was conducted using four online databases, followed by a meta-analysis. The outcomes of interest included clinical response/efficacy, microbial clearance, length of ICU stay, treatment failure, nephrotoxicity, and mortality.

RESULTS

Fourteen cohort studies met the inclusion criteria from which vancomycin trough concentration data were available for 5,228 participants. Our analysis found no association between vancomycin trough levels and clinical response [OR = 1.06 (95%CI 0.41-2.72], p = 0.91], microbial clearance [OR = 0.47 (95% CI 0.23-0.96), p = 0.04], ICU length of stay [MD=-1.01 (95%CI -5.73-3.71), p = 0.68], or nephrotoxicity [OR = 0.57 (95% CI 0.31-1.06), p = 0.07]. However, low trough levels were associated with a non-significant trend towards a lower risk of treatment failure [OR = 0.89 (95% CI 0.73-1.10), p = 0.28] and were significantly associated with reduced risk of all-cause mortality [OR = 0.74 (95% CI 0.62-0.90), p = 0.002].

CONCLUSION

Except for a lower risk of treatment failure and all-cause mortality at low vancomycin trough levels, this meta-analysis found no significant association between vancomycin trough levels and clinical outcomes in adult patients with sepsis or gram-positive bacterial infections.

Presence of multiple van genes among glycopeptide non-susceptible Staphylococcus aureus exhibiting in vitro MIC creep phenomenon: A study from north-east India

Background & objectives The global prevalence of vancomycin-resistant Staphylococcus aureus (VRSA) has increased two fold since 2010, accounting for 2.4 per cent of S. aureus infections. The emerging hVISA isolates and their increasing trends pose a serious therapeutic challenge. The present study investigated in vitro vancomycin and teicoplanin minimum inhibitory concentration (MIC) creep in S. aureus and assessed their revertants. Methods A total of 845 isolates were collected for this study, and 246 were confirmed as S. aureus. Molecular characterization of vancomycin resistance was carried out by PCR assay targeting genes types viz: vanA, vanB, vanC, vanC2/C3, vanD, vanE, and vanG. MIC was determined for vancomycin and teicoplanin by agar dilution method. MIC creep and revertant analysis were done by broth dilution method in the presence and absence of antibiotics. Results PCR assay confirmed 12 isolates were harboured vanA, followed by vanD (n=8) and vanB (n=7). The study showed 69 isolates were screened positive for glycopeptide non-susceptibility. While analyzing vancomycin MIC creep, four isolates showed a significant increase in MIC, whereas no creep phenomenon was observed for the rest. In the case of teicoplanin, seven isolates showed the MIC creep phenomenon. Revertant analysis of all the isolates that showed MIC creep phenomenon for vancomycin and teicoplanin reverted to their original MIC when the antibiotic pressure was withdrawn. Interpretation & conclusions In the present study setting, glycopeptide non-susceptibility was found in eight per cent of the isolates, and the present study found the occurrence of multiple van genes from isolates calculated from a single study center will impose a serious challenge in infection control and antibiotic policy. This study also underscores that heterogenic resistant isolates, upon exposure to vancomycin and teicoplanin at a minimum level, exhibited an increase in MIC, which will impact individuals receiving glycopeptide therapy.

An Overview of Antimicrobial Resistance in Saudi Arabia (2013-2023) and the Need for National Surveillance

Antimicrobial resistance (AMR) is a well-recognized global threat. The World Health Organization (WHO) issued a report ranking the critical types of bacterial resistance that need to be monitored. Several studies from individual institutions in Saudi Arabia have reported rates of antimicrobial resistance using automated methods. However, no national surveillance study has been conducted to date using gold standard methods for antimicrobial susceptibility testing. This review summarizes AMR rates for major bacterial pathogens in Saudi Arabia and provides a justification for the need for a national surveillance project. In Saudi Arabia, AMR rates for both Gram-positive and Gram-negative bacteria are on the rise. Surveillance studies help identify AMR trends and emergence of outbreaks. The WHO has started a program, the Global Antimicrobial Resistance Surveillance System (GLASS), encouraging its member states, including Saudi Arabia, to conduct antimicrobial surveillance studies to estimate AMR rates worldwide. Of the microbiological methods used to test antimicrobial susceptibility, only broth microdilution (BMD) is considered the "gold standard." As AMR studies in Saudi Arabia are sparse, mostly limited to single centers and were conducted using automated methods, a national AMR surveillance project is needed to evaluate the current status and to inform stewardship decisions.

Implantable biomedical materials for treatment of bone infection

The treatment of bone infections has always been difficult. The emergence of drug-resistant bacteria has led to a steady decline in the effectiveness of antibiotics. It is also especially important to fight bacterial infections while repairing bone defects and cleaning up dead bacteria to prevent biofilm formation. The development of biomedical materials has provided us with a research direction to address this issue. We aimed to review the current literature, and have summarized multifunctional antimicrobial materials that have long-lasting antimicrobial capabilities that promote angiogenesis, bone production, or "killing and releasing." This review provides a comprehensive summary of the use of biomedical materials in the treatment of bone infections and a reference thereof, as well as encouragement to perform further research in this field.

Staphylococcal Cassette Chromosome mec Typing and Multilocus Variable Number Tandem Repeat Analysis of Methicillin Resistant Staphylococcus aureus Clinical Isolates with Vancomycin Creep Phenomenon

Background

The association of treatment failure and mortality with vancomycin minimum inhibitory concentration creep (MIC) is a matter of serious concern in patients with severe methicillin resistant Staphylococcus aureus (MRSA) infections. The purpose of the study was to identify and characterize staphylococcal cassette chromosome mec (SCCmec) and clonal types of MRSA strains, exhibiting the vancomycin MIC creep phenomenon.

Methods

A total of 3305 S. aureus strains were isolated from various clinical samples of Lahore General Hospital, Lahore, Pakistan. MRSA strains were identified by cefoxitin resistant (≤21mm) followed by mecA and mecC gene genotyping. Vancomycin MIC creep was determined by E-test. Isolates having MIC values >1.5 µg/mL were further subjected for SCCmec typing (I–V and XI) and multiple-locus variable number tandem repeat analysis (MLVA) by amplification of spa, sspA, clfA, clfB, and sdrCDE genes. A dendrogram was created based on the similarity index using bioneumerics software.

Results

About 13.3% (440/3305) isolates were MRSA with 99.3% (437/440) and 0.7% (3/440) carried mecA and mecC genes, respectively. In 120 MRSA isolates, the MIC of vancomycin was >1.5µg/mL. In MRSA isolates with high vancomycin MIC (>1.5µg/mL), the most common SCCmec type was SCCmec III (38.3%), followed by SCCmec IVa (15.8%), SCCmec IIIa (13.3%,), SCCmec IVc (7.5%), SCCmec IVe (5.8%), SCCmec IVd (5.8%), SCCmec IVb (4.2%), SCCmec II (2.5%), SCCmec V (1.7%), SCCmec I (1.7%) and SCCmec XI (1.7%). MLVA revealed 60 genotypic groups of MRSA isolates having a 92% similarity index.

Conclusion

SCCmec III was the most common type in genetically related MRSA isolates showing vancomycin MIC creep. The presence of SCCmec XI may further add burden to infection control measures.

Investigational agents for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia: progress in clinical trials

INTRODUCTION

Bacteremia caused by Staphylococcus aureus is common. Cases caused by methicillin-resistant S. aureus (MRSA) are particularly formidable and often lethal. The mortality associated with MRSA bacteremia has not significantly decreased over the past couple of decades and concerns regarding efficacy and toxicity of standard therapy highlight the need for novel agents and new therapeutic approaches.

AREAS COVERED

This paper explores clinical trials investigating novel therapeutic approaches to S. aureus bacteremia. There is a special focus on MRSA bacteremia. Monotherapy and combination therapies and novel antimicrobials and adjunctive therapies that are only recently being established for therapeutic use are discussed.

EXPERT OPINION

The unfavorable safety profile of combination antimicrobial therapy in clinical trials has outweighed its benefits. Therefore, future investigation should focus on optimizing duration and de-escalation protocols. Antibody and bacteriophage lysin-based candidates have mostly been limited to safety trials, but progress with these agents is demonstrated through a lysin-based agent receiving a phase III trial. Antibiotics indicated for use in treating MRSA skin infections see continued investigation as treatments for MRSA bacteremia despite the difficulty of completing trials in this patient population. Promising agents include dalbavancin, ceftobiprole, ceftaroline, and exebacase.

In Vitro Activity of Vancomycin, Teicoplanin, Linezolid and Daptomycin Against Methicillin-Resistant Staphylococcus aureus Isolates Collected from Chinese Hospitals in 2018-2020

Introduction

Vancomycin, teicoplanin, linezolid and daptomycin are four major antibacterials used for methicillin-resistant Staphylococcus aureus (MRSA) infection treatment. However, with the increasing failure of clinical MRSA anti-infective treatment, it is urgent to investigate the status of MRSA sensitivity to these four drugs.

Methods

In the present study, 407 non-duplicated MRSA isolates from 6 provinces in China were collected from January 2018 to August 2020. The minimum inhibitory concentrations (MICs) of vancomycin, teicoplanin, linezolid and daptomycin were determined by broth microdilution method, and their MIC50, MIC90, and geometric mean MIC were calculated.

Results

All 407 MRSA strains were sensitive to these four antibacterials. MIC range of vancomycin, teicoplanin, linezolid and daptomycin was 0.25 to 2 mg/L, 0.125 to 4 mg/L, 0.25 to 4 mg/L and 0.06 to 1 mg/L, respectively. Between 2018 and 2020, there was no “MIC creep” in vancomycin, teicoplanin and daptomycin. The geometric mean MIC of linezolid was not increased, but both MIC50 and MIC90 in 2019 and 2020 MRSA isolates were higher than 2018 isolates.

Conclusion

All MRSA isolates remained sensitivity to vancomycin, teicoplanin, linezolid and daptomycin. The linezolid MIC50 and MIC90 increased have been found in this study.

Nemonoxacin enhances antibacterial activity and anti-resistant mutation ability of vancomycin against methicillin-resistant Staphylococcus aureus in an in vitro dynamic pharmacokinetic/pharmacodynamic model

Reduced susceptibility and emergence of resistance to vancomycin in methicillin-resistant Staphylococcus aureus (MRSA) have led to the development of various vancomycin based combinations. Nemonoxacin is a novel nonfluorinated quinolone with antibacterial activity against MRSA. The present study aimed to investigate the effects of nemonoxacin on antibacterial activity and the anti-resistant mutation ability of vancomycin for MRSA and explore whether quinolone resistance genes are associated with a reduction in the vancomycin minimal inhibitory concentration (MIC) and mutant prevention concentration (MPC) when combined with nemonoxacin. Four isolates, all with a vancomycin MIC of 2 μg/mL, were used in a modified in vitro dynamic pharmacokinetic/pharmacodynamic model to investigate the effects of nemonoxacin on antibacterial activity (M04, M23 and M24) and anti-resistant mutation ability (M04, M23 and M25, all with MPC ≥19.2 μg/mL) of vancomycin. The mutation sites of gyrA, gyrB, parC, and parE of 55 clinical MRSA isolates were sequenced. We observed that in M04 and M23, the combination of vancomycin (1g q12h) and nemonoxacin (0.5g qd) showed a synergistic bactericidal activity and resistance enrichment suppression. All clinical isolates resistant to nemonoxacin harbored gyrA (S84→L) mutation; gyrA (S84→L) and parC (E84→K) mutations were the two independent risk factors for the unchanged vancomycin MPC in combination. Nemonoxacin enhances the bactericidal activity and suppresses resistance enrichment ability of vancomycin against MRSA with a MIC of 2 μg/mL. Our in vitro data support the combination of nemonoxacin and vancomycin for the treatment of MRSA infection with a high MIC.