Survey of infections due to Staphylococcus species: frequency of occurrence and antimicrobial susceptibility of isolates collected in the United States, Canada, Latin America, Europe, and the Western Pacific region for the SENTRY Antimicrobial Surveillance Program, 1997-1999

Blood Culture Result Profile in Patients With Central Line-Associated Bloodstream Infection (CLABSI): A Single-Center Experience

Background Central line-associated bloodstream infection (CLABSI) is among the most common bloodstream infections in the university hospital and intensive care unit settings. This study evaluated the routine blood test findings and microbe profiles of bloodstream infection (BSI) by the presence and types of central vein (CV) access devices (CVADs). Methods A total of 878 inpatients at a university hospital who were clinically suspected for BSI and underwent blood culture (BC) testing between April 2020 and September 2020 were enrolled. Data regarding age at BC testing, sex, WBC count, serum C-reactive protein (CRP) level, BC test results, yielded microbes, and usage and types of CVADs were evaluated. Results The BC yields were detected in 173 patients (20%), suspected contaminating pathogens in 57 (6.5%), and 648 (74%) with a negative yield. The WBC count (p=0.0882) and CRP level (p=0.2753) did not significantly differ between the 173 patients with BSI and the 648 patients with negative BC yields. Among the 173 patients with BSI, 74 used CVADs and met the diagnosis of CLABSI; 48 had a CV catheter, 16 had CV access ports, and 10 had a peripherally inserted central catheter (PICC). Patients with CLABSI showed lower WBC counts (p=0.0082) and serum CRP levels (p=0.0024) compared to those with BSI who did not use CVADs. The most commonly yielded microbes in those with CV catheters, CV-ports, and PICC were Staphylococcus epidermidis (n=9; 19%), Staphylococcus aureus (n=6; 38%), and S. epidermidis (n=8; 80%), respectively. Among those with BSI who did not use CVADs, Escherichia coli (n=31; 31%) was the most common pathogen, followed by S. aureus (n=13; 13%). Conclusion Patients with CLABSI showed lower WBC counts and CRP levels than those with BSI who did not use CVADs. Staphylococcus epidermidis was among the most common microbes in CLABSI and accounted for the majority of yielded microbes in patients who used PICC.

Staphylococcus aureus Infection: Pathogenesis and Antimicrobial Resistance

Staphylococcus aureus, a Gram-positive, coagulase-positive pathogen belonging to the family Staphylococcaceae with a spherical shape that forms grape-like clusters, is a commensal that is often present asymptomatically on parts of the human body [...].

Phenotypic and molecular characterization of Staphylococcus aureus from mobile phones in Nigeria

The presence of Staphylococcus aureus, a normal human flora on cellphones of different professionals in Ile-Ife was investigated with a view to determining their antibiotic susceptibility profile and nature of resistance and virulence genes. One hundred swab samples were collected aseptically from mobile phones of various users based on their profession. Surfaces of the mobile phones were swabbed and the streak plate method was used to isolate colonies showing characteristic golden yellow on mannitol salt agar plates. These isolates were further identified using standard microbiological methods. The antibiotic susceptibility of the isolates was determined using Kirby-Bauer's disk diffusion technique. Molecular detection of nuc, mecA and pvl genes in some isolates was carried out by polymerase chain reaction technique. All the 36 isolates obtained in this study were 100% resistant to amoxicillin and augmentin; the isolates also displayed 55.6%, 44.4% and 41.7% resistance to ceftriazone, erythromycin and chloramphenicol, respectively. Based on resistance to oxacillin, prevalence of methicillin resistant Staphylococcus aureus (MRSA) was 11.1%. Only one S. aureus was positive for plasmid analysis. MecA gene was genetically confirmed in four (4) out of the 16 suspected phenotypic MRSA strains, nuc gene was confirmed in all 28 isolates investigated, while there was no pvl gene in the strains investigated. Mobile phones harbor multiple antibiotics resistant S. aureus, which are responsible for important diseases in humans and could be difficult to manage with antibiotics thereby posing serious health risks.

New Antibiotics for Staphylococcus aureus Infection: An Update from the World Association of Infectious Diseases and Immunological Disorders (WAidid) and the Italian Society of Anti-Infective Therapy (SITA)

Staphylococcus aureus is an extremely virulent pathogen that is capable of quickly evolving and developing antibiotic resistance. To overcome this problem, new antibiotics have been developed. Some of these have been licenced for use in clinical practice, mainly for the treatment of adults with acute skin and soft tissue infections, in addition to both community-acquired pneumonia (CAP) and nosocomial pneumonia (hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia). In this paper, the main characteristics and clinical use of new licenced anti-staphylococcal drugs have been discussed. In vitro studies have demonstrated that some new anti-staphylococcal antibiotics have better antimicrobial activity and, at least in certain cases, more favourable pharmacokinetic properties and higher safety and tolerability than the presently available anti-staphylococcal drugs. This suggests that they may have a potential use in reducing the risk of failure of S. aureus therapy. However, an in-depth analysis of microbiological and clinical studies carried out with these new drugs seems to indicate that further studies need to be conducted before the problem of resistance of S. aureus to the antibiotics available today can be completely solved. Considering the overall available research, the drugs that are active against S. aureus appear to present a great therapeutic opportunity for overcoming resistance to traditional therapy. There are advantages in the pharmacokinetic characteristics of some of these drugs and they have the potential to reduce hospital stays and economic costs associated with their use.

Identification and Molecular Modification of Staphylococcus aureus Bacteriophage Lysin LysDZ25

With the continuous emergence and spread of drug-resistant and multi-drug-resistant Staphylococcus aureus, traditional antibiotic treatment has gradually lost its effect. There is an urgent need to develop and study new and effective bio-green inhibitors to control S. aureus. In this study, the S. aureus phage DZ25 was isolated from milk and the lysin LysDZ25 with excellent tolerance to serum and NaCl solution was identified. Subsequently, to improve the lytic activity and thermal stability of LysDZ25, RoseTTAFold was used to construct three-dimensional (3D) structures, molecular dynamics (MD) simulation was used for conformational acquisition, and the MDL strategy previously developed in our lab was used to rationally design variants. After two rounds of rational design, the optimal variant with improved thermal stability, S333V/N245R/D299L, was obtained, and its half-life time was 4.0-fold that of wild-type LysDZ25. At 37, 40, 45, and 50 °C, the lytic activity of the optimal triple-point variant S333V/N245R/D299L was increased by 17.3-, 26.7-, 20.2-, and 50.1-fold compared with that of the wild-type LysDZ25, respectively. Finally, cell count was used to evaluate the lytic activity, and the results showed that the optimal variant S333V/N245R/D299L could drop about 3.5 log 10 values compared with the control and about 2.6 log 10 values compared with the wild-type LysDZ25.

Controlled processivity in glycosyltransferases: A way to expand the enzymatic toolbox

Glycosyltransferases (GT) catalyse the biosynthesis of complex carbohydrates which are the most abundant group of molecules in nature. They are involved in several key mechanisms such as cell signalling, biofilm formation, host immune system invasion or cell structure and this in both prokaryotic and eukaryotic cells. As a result, research towards complete enzyme mechanisms is valuable to understand and elucidate specific structure-function relationships in this group of molecules. In a next step this knowledge could be used in GT protein engineering, not only for rational drug design but also for multiple biotechnological production processes, such as the biosynthesis of hyaluronan, cellooligosaccharides or chitooligosaccharides. Generation of these poly- and/or oligosaccharides is possible due to a common feature of several of these GTs: processivity. Enzymatic processivity has the ability to hold on to the growing polymer chain and some of these GTs can even control the number of glycosyl transfers. In a first part, recent advances in understanding the mechanism of various processive enzymes are discussed. To this end, an overview is given of possible engineering strategies for the purpose of new industrial and fundamental applications. In the second part of this review, we focused on specific chain length-controlling mechanisms, i.e., key residues or conserved regions, and this for both eukaryotic and prokaryotic enzymes.

Detection of Methicillin-Resistant Staphylococcus aureus among Foodborne Pathogenic Strains and Assessment of Their Adhesion Ability and Cytotoxic Effects in HCT-116 Cells

Staphylococcus aureus is one of the high-threat pathogens equipped with a repertoire of virulence factors making it responsible for many infections in humans, including foodborne diseases. The present study aims to characterize antibiotic resistance and virulence factors in foodborne S. aureus isolates, and to investigate their cytotoxic effects in human intestinal cells (HCT-116). Our results revealed methicillin resistance phenotypes (MRSA) along with the detection of mecA gene (20%) among tested foodborne S. aureus strains. Furthermore, 40% of tested isolates showed a strong ability for adhesion and biofilm formation. A high rate of exoenzymes production by tested bacteria was also registered. Additionally, treatment with S. aureus extracts leads to a significant decrease in HCT-116 cell viability, accompanied by a reduction in the mitochondrial membrane potential (MMP), as a result of reactive oxygen species (ROS) generation. Thereby, S. aureus food poisoning remains daunting and needs particular concern to prevent foodborne illness.

Precise Photothermal Treatment of Methicillin-Resistant S. aureus Infection via Phage Lysin-Cell Binding Domain-Modified Gold Nanosheets

The increasing spread of antibiotic resistance in bacterial pathogens poses a huge threat to global human health. Precise targeting of bacterial pathogens while avoiding collateral damage to healthy tissues has become the overriding goal for bacterial infection treatment. Inspired by the host specificity of bacteriophages, a biomimetic intelligent platform was designed for highly precise photothermal treatment herein. As proof-of-concept, the lysin cell-binding domain (CBD) from a newly discovered virulent methicillin-resistant S. aureus (MRSA) phage Z was applied to the functionalization of gold nanosheets. Our results demonstrated that the bionanocomposite gold particles (Au@PEG-CBDz) could be effectively delivered directly to MRSA and kill them effectively under near infrared irradiation in vitro, while displaying good in vivo biocompatibility. This work is the first to report the combination of phage lysin navigatory function with photothermal effect-induced bactericidal activity from Au nanosheets, providing a novel therapeutic mode for the precision treatment of antibiotic-resistant bacterial infections.

Current and emerging drug treatment strategies to tackle invasive community-associated methicillin-resistant Staphylococcus aureus (MRSA) infection: what are the challenges?

INTRODUCTION

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections represent a leading cause of purulent skin and soft tissue infections in some geographical regions. Traditionally, 'old antibiotics' such as trimethoprim-sulfamethoxazole, tetracyclines, clindamycin, chloramphenicol,vancomycin, and teicoplanin have been used to treat these infections, but these were often associated with low efficacy and excessive side effects and toxicity, especially nephrotoxicity. Along with the development of new compounds, the last decade has seen substantial improvements in the management of CA-MRSA infections.

AREAS COVERED

In this review, the authors discuss the current and emerging drug treatment strategies to tackle invasive CA-MRSA infections. Articles reported in this review were selected from through literature searches using the PubMed database.

EXPERT OPINION

The availability of new drugs showing a potent in vitro activity against CA-MRSA represents a unique opportunity to face the threat of resistance while potentially reducing toxicity. All these compounds represent promising options to enhance our antibiotic armamentarium. However, data regarding the use of these new drugs in real-life studies are limited and their best placement in therapy and in terms of optimization of medical resources and balance of cost-effectiveness requires further investigation.

MRSA compendium of epidemiology, transmission, pathophysiology, treatment, and prevention within one health framework

Staphylococcus aureus is recognized as commensal as well as opportunistic pathogen of humans and animals. Methicillin resistant strain of S. aureus (MRSA) has emerged as a major pathogen in hospitals, community and veterinary settings that compromises the public health and livestock production. MRSA basically emerged from MSSA after acquiring SCCmec element through gene transfer containing mecA gene responsible for encoding PBP-2α. This protein renders the MRSA resistant to most of the β-lactam antibiotics. Due to the continuous increasing prevalence and transmission of MRSA in hospitals, community and veterinary settings posing a major threat to public health. Furthermore, high pathogenicity of MRSA due to a number of virulence factors produced by S. aureus along with antibiotic resistance help to breach the immunity of host and responsible for causing severe infections in humans and animals. The clinical manifestations of MRSA consist of skin and soft tissues infection to bacteremia, septicemia, toxic shock, and scalded skin syndrome. Moreover, due to the increasing resistance of MRSA to number of antibiotics, there is need to approach alternatives ways to overcome economic as well as human losses. This review is going to discuss various aspects of MRSA starting from emergence, transmission, epidemiology, pathophysiology, disease patterns in hosts, novel treatment, and control strategies.

Molecular Epidemiology of Community-Acquired Methicillin-Resistant Staphylococcus aureus and Clinical Characteristics of Different Sites of Infection

Purpose

Since community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) was recognized, the molecular epidemiology of CA-MRSA in China has been diverse. It is unclear whether different sites of CA-MRSA infection differ in antimicrobial resistance and clinical characteristics. The purpose of this study was to identify the molecular types, virulence factors and antimicrobial resistance of CA-MRSA strains and to analyze the clinical characteristics of different sites of CA-MRSA infection.

Methods

26 CA-MRSA strains were screened from Beijing Chao-Yang Hospital from 2014 to 2022. SCCmec type, MLST type, spa type, Panton-Valentine leukocidin (PVL), hemolysin α (Hla), phenolic soluble regulatory protein α (PSMα), toxic shock syndrome toxin-1 (TSST-1), and enterotoxin (SE) A to E were detected by PCR and gene sequencing. Antimicrobial susceptibility tests and the clinical features of CA-MRSA infection cases were collected for statistical analysis.

Results

The predominant type of CA-MRSA was ST59-t437-IV. New non-epidemic types, SCCmec VII, were also found. PVL was seen in 65.4% of CA-MRSA strains and TSST-1 was only be detected in 3.8% of CA-MRSA strain which caused poor prognosis. There were three types of infections: pneumonia (61.5%), infective endocarditis (7.7%), and skin and soft tissue infections (SSTIs) (30.8%). CA-MRSA pneumonia cases were secondary to influenza infection (37.5%). Patients with CA-MRSA-associated infective endocarditis were more likely to have underlying cardiac diseases. Patients with CA-MRSA-associated SSTIs were more likely to have a history of diabetes mellitus, and strains in this group were more susceptible to erythromycin and clindamycin.

Conclusion

ST59-t437-IV was the primary CA-MRSA type in our research and in China. We proposed that TSST-1 might be one of the indicators to predict the severity and prognosis of CA-MRSA infection. Different sites of CA-MRSA infection had difference in antibiotics susceptibility testing and underlying diseases of patients. It could provide a new perspective on treating different types of CA-MRSA infection.

Synergistic Potentiation of Antimicrobial and Antibiofilm Activities of Penicillin and Bacitracin by Octyl Gallate, a Food-Grade Antioxidant, in Staphylococcus epidermidis

Staphylococcus epidermidis is a major nosocomial pathogen that frequently forms biofilms on indwelling medical devices. This study aimed to investigate the synergistic antimicrobial and antibiofilm activities of octyl gallate (OG) in combination with penicillin and bacitracin against S. epidermidis. Antimicrobial synergy was assessed by conducting checkerboard titration assays, and antibiofilm activity was determined with biofilm assays and fluorescence microscopy analysis. The presence of 8 µg/mL of OG increased both the bacteriostatic and bactericidal activities of penicillin and bacitracin against S. epidermidis. It lowered the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of penicillin by eight-fold and those of bacitracin by four-fold. Moreover, when used with penicillin or bacitracin, OG significantly decreased the level of biofilm production by preventing microcolony formation. Furthermore, OG significantly permeabilized the bacterial cell wall, which may explain its antimicrobial synergy with penicillin and bacitracin. Together, these results demonstrate that OG, a food-grade antioxidant, can be potentially used as a drug potentiator to enhance the antimicrobial and antibiofilm activities of penicillin and bacitracin against S. epidermidis.

Nontargeted metabolomics reveals differences in the metabolite profiling among methicillin-resistant and methicillin-susceptible Staphylococcus aureus in response to antibiotics

Staphylococcus aureus (S. aureus) causes infections and can be fatal. In the long-term struggle against antibiotics, S. aureus has acquired resistance toward antibiotics and become more difficult to kill. Metabolomics could directly reflect the responses of S. aureus toward antibiotics, which is effective for studying the resistance mechanism of S. aureus. In this study, based on a nontargeted metabolic figure printing technique, the metabolome of a pair of isogenic methicillin-susceptible and resistant S. aureus strains ATCC25923 (MSSA) and ATCC43300 (MRSA) treated with or without oxacillin was characterized. 7 and 29 significantly changed metabolites in MRSA and MSSA were identified by combined accurate mass and mass fragmentation analysis. Pathway enrichment analysis suggested that DNA repair and flavin biosynthesis are the universal pathways of both MSSA and MRSA under antibiotic stress. MRSA systematically and effectively fights against oxacillin through precise control of energy production, PBP2a substrate biosynthesis and antioxidant function. In contrast, MSSA lacks effective defense pathways against oxacillin. The different metabolome responses of MSSA and MRSA toward antibiotics provide us with new insights into how S. aureus develops antibiotic resistance.

Phenotypic and Molecular Detection of Antiseptic Resistance Genes among Clinical Staphylococcus aureus Isolates During COVID-19 Pandemic

The coronavirus disease (COVID-19) pandemic has expanded the use of chlorhexidine digluconate, a biocide frequently used in hospitals, to inhibit the spread of infection. Genes responsible for resistance against the quaternary ammonium compound qac in Staphylococcus aureus isolates have been shown to confer tolerance to a number of biocidal chemicals, including chlorhexidine. The aim of this study was to determine the occurrence of antiseptic resistance genes (qacA/B and qacC) in clinical isolates of methicillin-susceptible (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA). The study also aimed to investigate the association between the presence of the mecA, qacA/B, and qacC genes in MRSA isolates and the susceptibility of the isolates to chlorhexidine to evaluate its future use in the Theodor Bilharz Research Institute (TBRI) hospital, following the Centers for Disease Control and Prevention recommendations for patients with MRSA. S. aureus isolates (n = 100) were collected from inpatients and outpatients at TBRI. A minimal inhibitory concentration of chlorhexidine was also detected. Polymerase chain reaction was used to detect the mecA, qacA/B, and qacC genes. The results revealed that 84% of S. aureus isolates were MRSA. MRSA (61.9%) and MSSA (68.8%) isolates were susceptible to chlorhexidine. The qacA/B gene was more dominant, being detected in 34%, while qacC was detected in only 5% of S. aureus isolates. All S. aureus isolates with reduced susceptibility to chlorhexidine harbored either the qacA/B or qacC genes. The clinical use of chlorhexidine may continue to increase, emphasizing the significance of continuous caution underlining the emergence of new clones with reduced susceptibility and avoiding antiseptic misuse.

CRISPR/Cas-Based Biosensor As a New Age Detection Method for Pathogenic Bacteria

Methods enabling rapid and on-site detection of pathogenic bacteria are a prerequisite for public health assurance, medical diagnostics, ensuring food safety and security, and research. Many current bacteria detection technologies are inconvenient and time-consuming, making them unsuitable for field detection. New technology based on the CRISPR/Cas system has the potential to fill the existing gaps in detection. The clustered regularly interspaced short palindromic repeats (CRISPR) system is a part of the bacterial adaptive immune system to protect them from intruding bacteriophages. The immunological memory is saved by the CRISPR array of bacteria in the form of short DNA sequences (spacers) from invading viruses and incorporated with the CRISPR DNA repeats. Cas proteins are responsible for triggering and initiating the adaptive immune function of CRISPR/Cas systems. In advanced biological research, the CRISPR/Cas system has emerged as a significant tool from genome editing to pathogen detection. By considering its sensitivity and specificity, this system can become one of the leading detection methods for targeting DNA/RNA. This technique is well applied in virus detection like Dengue, ZIKA, SARS-CoV-2, etc., but for bacterial detection, this CRISPR/Cas system is limited to only a few organisms to date. In this review, we have discussed the different techniques based on the CRISPR/Cas system that have been developed for the detection of various pathogenic bacteria like L. monocytogenes, M. tuberculosis, Methicillin-resistant S. aureus, Salmonella, E. coli, P. aeruginosa, and A. baumannii.

Isovitexin Protects Mice from Methicillin-Resistant Staphylococcus aureus-Induced Pneumonia by Targeting Sortase A

The rise of methicillin-resistant Staphylococcus aureus (MRSA) has resulted in significant morbidity and mortality, and clinical treatment of MRSA infections has become extremely difficult. Sortase A (SrtA), a virulence determinant that anchors numerous virulence-related proteins to the cell wall, is a prime druggable target against S. aureus infection due to its crucial role in the pathogenicity of S. aureus. Here, we demonstrate that isovitexin, an active ingredient derived from a variety of traditional Chinese medicines, can reversibly inhibit SrtA activity in vitro with a low dose (IC₅₀=24.72 μg/ml). Fluorescence quenching and molecular simulations proved the interaction between isovitexin and SrtA. Subsequent point mutation experiments further confirmed that the critical amino acid positions for SrtA binding to isovitexin were Ala-92, Ile-182, and Trp-197. In addition, isovitexin treatment dramatically reduced S. aureus invasion of A549 cells. This study shows that treatment with isovitexin could alleviate pathological injury and prolong the life span of mice in an S. aureus pneumonia model. According to our research, isovitexin represents a promising lead molecule for the creation of anti-S. aureus medicines or adjuncts.

Rates of Antimicrobial Resistance With Extended Oral Antibiotic Prophylaxis After Total Joint Arthroplasty

Background

There is increased interest and utilization of extended oral antibiotic prophylaxis (EOAP) following primary and revision total hip arthroplasties (THAs) and total knee arthroplasties (TKAs). The purpose of this study was to look for potential associations between EOAP and differential rates of antimicrobial resistance or epidemiology of organisms causing periprosthetic joint infection (PJI) following primary and aseptic revision THAs/TKAs.

Methods

Patients who developed PJI following a primary or aseptic revision TKA/THA at a single institution from 2009 to 2020 were retrospectively identified. Patients who received at least 7 days of EOAP following the surgery were noted. Rates of antimicrobial resistance were compared between standard antibiotic prophylaxis and EOAP cohorts using the Fisher's exact test.

Results

One hundred twenty-eight cultures were obtained from 119 patients with PJI. Fourty-four cases (37%) developed PJI after EOAP. Staphylococcus aureus was the most frequently isolated organism (30% of all cultures; 78% were methicillin-sensitive). Rates of antimicrobial resistance were similar between standard antibiotic prophylaxis and EOAP cohorts in all but 2 instances: Increased resistance to erythromycin and trimethoprim-sulfamethoxazole was observed in coagulase-negative Staphylococci isolates in the EOAP cohort (89% vs 21%, P < .01; 44% vs 0%, P = .02). An increased frequency of gram-negative organisms was observed in the EOAP group (22% vs 8%, P = .03).

Conclusions

Rates of antimicrobial resistance were not significantly different between EOAP and standard antibiotic prophylaxis cohorts except in coagulase-negative Staphylococci. The increased frequency of gram-negative infections was present in the EOAP cohort. Larger, multicenter studies are needed to better understand the impact of EOAP on antimicrobial resistance and PJI epidemiology.

Level of Evidence

Level III; retrospective cohort study.

Molecular Basis of Non-β-Lactam Antibiotics Resistance in Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most successful human pathogens with the potential to cause significant morbidity and mortality. MRSA has acquired resistance to almost all β-lactam antibiotics, including the new-generation cephalosporins, and is often also resistant to multiple other antibiotic classes. The expression of penicillin-binding protein 2a (PBP2a) is the primary basis for β-lactams resistance by MRSA, but it is coupled with other resistance mechanisms, conferring resistance to non-β-lactam antibiotics. The multiplicity of resistance mechanisms includes target modification, enzymatic drug inactivation, and decreased antibiotic uptake or efflux. This review highlights the molecular basis of resistance to non-β-lactam antibiotics recommended to treat MRSA infections such as macrolides, lincosamides, aminoglycosides, glycopeptides, oxazolidinones, lipopeptides, and others. A thorough understanding of the molecular and biochemical basis of antibiotic resistance in clinical isolates could help in developing promising therapies and molecular detection methods of antibiotic resistance.

Characterization of Staphylococcus epidermidis clinical isolates from hospitalized patients with bloodstream infection obtained in two time periods

Background

In recent years Staphylococcus epidermidis has been considered an important and frequent causative agent of health care-associated infections (HAIs), increasing the costs of hospitalization, morbidity, and mortality. Antibiotic resistance and biofilm formation are the most important obstacles in the treatment of infections caused by this microorganism. The aim of this work was to determine the most prevalent STs, as well as the antibiotic resistance profile and biofilm formation of S. epidermidis clinical isolates obtained from hospitalized patients in two hospitals in Acapulco, Guerrero in two time periods.

Methods

Twenty methicillin-resistant S. epidermidis strains isolated from patients with bacteremia in two hospitals in two time periods were analyzed. Identification and antibiotic susceptibility were performed using the Vitek automated system. Molecular confirmation of the identification and methicillin resistance was performed by duplex PCR of the mecA and nuc genes. Biofilm production was analyzed, and the clonal origin was determined by multilocus sequence typing (MLST).

Results

We identified 14 antibiotic resistance profiles as well as 13 sequence types (ST), including the new ST761. We also found that ST2 and ST23 were the most prevalent and, together with ST59, were found in both time periods. Seventeen of our clinical isolates were multidrug-resistant, but all of them were sensitive to linezolid and vancomycin, and this was not related to biofilm production. Additionally, we standardized a duplex PCR to identify methicillin-resistant S. epidermidis strains. In conclusion, S. epidermidis STs 2, 23, and 59 were found in both time periods. This study is the first report of S. epidermidis ST761. The clinical isolates obtained in this work showed a high multidrug resistance that is apparently not related to biofilm production.

A potent antibiotic-loaded bone-cement implant against staphylococcal bone infections

New antibiotics should ideally exhibit activity against drug-resistant bacteria, delay the development of bacterial resistance to them and be suitable for local delivery at desired sites of infection. Here, we report the rational design, via molecular-docking simulations, of a library of 17 candidate antibiotics against bone infection by wild-type and mutated bacterial targets. We screened this library for activity against multidrug-resistant clinical isolates and identified an antibiotic that exhibits potent activity against resistant strains and the formation of biofilms, decreases the chances of bacterial resistance and is compatible with local delivery via a bone-cement matrix. The antibiotic-loaded bone cement exhibited greater efficacy than currently used antibiotic-loaded bone cements against staphylococcal bone infections in rats. Potent and locally delivered antibiotic-eluting polymers may help address antimicrobial resistance.

Analysis of the Distribution and Antibiotic Resistance of Pathogens Causing Infections in Hospitals from 2017 to 2019

Background. Antibiotic resistance is a global public health problem, leading to high mortality and treatment costs. To achieve more efficient treatment protocols and better patient recovery, the distribution and drug resistance of pathogens in our hospital were investigated, allowing significant clinical guidance for the use of antimicrobials. Methods. In this retrospective study (2017–2019), 3482 positive samples were isolated from 43,981 specimens in 2017; 3750 positive specimens were isolated from 42,923 specimens in 2018; and 3839 positive pathogens were isolated from 46,341 specimens in 2019. These samples were from various parts of the patients, including the respiratory tract, urine, blood, wound secretions, bile, and puncture fluids. The distribution and antibiotic resistance of these isolated pathogens from the whole hospital were analyzed. Results. The results from pathogen isolation showed that Escherichia coli (12.8%), Staphylococcus aureus (11%), Klebsiella pneumoniae (10.8%), Pseudomonas aeruginosa (10.7%), and Acinetobacter baumannii (6.4%) represented the five main pathogenic bacteria in our hospital. Pseudomonas aeruginosa (16.2% and 17.5%) occupied the largest proportion in the central intensive care unit (central ICU) and respiratory intensive care unit (RICU), while Acinetobacter baumannii (15.4%) was the most common pathogen in the emergency intensive care unit (EICU). The resistance rate of Escherichia coli to trimethoprim and minocycline was 100%, and the sensitivity rate to ertapenem, furantoin, and amikacin was above 90%. The resistance rate of Pseudomonas aeruginosa to all antibiotics, such as piperacillin and ciprofloxacin, was under 40%. The sensitivity rate of Acinetobacter baumannii to tigecycline and minocycline was less than 30%, and the resistance rate to many drugs such as piperacillin, ceftazidime, and imipenem was above 60%. Extended-spectrum β-lactamases (ESBLs)-producing Klebsiella pneumoniae (ESBLs-KPN) and carbapenem-resistant Klebsiella pneumoniae (CRE-KPN), ESBLs-producing Escherichia coli (ESBLs-ECO) and carbapenem-resistant Escherichia coli (CRE-ECO), multidrug-resistant Acinetobacter baumannii (MDR-AB), multidrug-resistant Pseudomonas aeruginosa (MDR-PAE), and methicillin-resistant Staphylococcus aureus (MRSA) are all important multidrug-resistant bacteria found in our hospital. The resistance rate of ESBLs-producing Enterobacteriaceae to ceftriaxone and amcarcillin-sulbactam was above 95%. CRE Enterobacteriaceae bacteria showed the highest resistance to amcarcillin-sulbactam (97.1%), and the resistance rates of MDR-AB to cefotaxime, cefepime, and aztreonam were 100%. The resistance rates of MDR-PAE to ceftazidime, imipenem, and levofloxacin were 100%, and the sensitivity rate to polymyxin B was above 98%. The resistance rate of MRSA to oxacillin was 100%, and the sensitivity rate to linezolid and vancomycin was 100%. Conclusion. The distribution of pathogenic bacteria in different hospital departments and sample sources was markedly different. Therefore, targeted prevention and control of key pathogenic bacteria in different hospital departments is necessary, and understanding both drug resistance and multiple drug resistance of the main pathogenic bacteria may provide guidance for the rational use of antibiotics in the clinic.

WCK 4034: A promising oxazolidinone for treating gram positive infections

Increased resistance to gram positive infections have highlighted the limitations of currently available drug treatments including penicillins, macrolides and glycopeptides. As an alternative to address these challenges; Linezolid, the first antibiotic from oxazolidinone class, have shown the promising activities against such infections, although associated toxicological issues limiting the use of linezolid for prolonged treatments. In order to circumvent disadvantages allied with the marketed drugs, we herein reporting the synthesis of WCK 4034, an oxazolidinone antibiotic through our structure activity relationship (SAR) program. Through this exercise, WCK 4034, has shown competitive MIC values against Methicillin Sensitive S. aureus (MSSA, Sta-001), Methicillin Resistant S. aureus (MRSA, Sta-032), S. pneumoniae ATCC 49619 and H. influenza ATCC 35054 species as like linezolid. Although with an additional advantage; WCK 4034 has been found superior during dog PK studies as compare to Linezolid. With the preliminary studies in our hand, we herein assuming these improved pharmacokinetic values would be helpful. Moreover, WCK 4034 has successfully completed pre-clinical studies and ready to enter the clinical space, and paved the way for in house development of other oxazolidinone NCEs.

Genomics of Staphylococcus aureus Strains Isolated from Infectious and Non-Infectious Ocular Conditions

Staphylococcus aureus is a major cause of ocular infectious (corneal infection or microbial keratitis (MK) and conjunctivitis) and non-infectious corneal infiltrative events (niCIE). Despite the significant morbidity associated with these conditions, there is very little data about specific virulence factors associated with the pathogenicity of ocular isolates. A set of 25 S. aureus infectious and niCIEs strains isolated from USA and Australia were selected for whole genome sequencing. Sequence types and clonal complexes of S. aureus strains were identified by using multi-locus sequence type (MLST). The presence or absence of 128 virulence genes was determined by using the virulence finder database (VFDB). Differences between infectious (MK + conjunctivitis) and niCIE isolates from USA and Australia for possession of virulence genes were assessed using the chi-square test. The most common sequence types found among ocular isolates were ST5, ST8 while the clonal complexes were CC30 and CC1. Virulence genes involved in adhesion (ebh, clfA, clfB, cna, sdrD, sdrE), immune evasion (chp, esaD, esaE, esxB, esxC, esxD), and serine protease enzymes (splA, splD, splE, splF) were more commonly observed in infectious strains (MK + conjunctivitis) than niCIE strains (p = 0.004). Toxin genes were present in half of infectious (49%, 25/51) and niCIE (51%, 26/51) strains. USA infectious isolates were significantly more likely to possess splC, yent1, set9, set11, set36, set38, set40, lukF-PV, and lukS-PV (p < 0.05) than Australian infectious isolates. MK USA strains were more likely to possesses yent1, set9, set11 than USA conjunctivitis strains (p = 0.04). Conversely USA conjunctivitis strains were more likely to possess set36 set38, set40, lukF-PV, lukS-PV (p = 0.03) than MK USA strains. The ocular strain set was then compared to 10 fully sequenced non-ocular S. aureus strains to identify differences between ocular and non-ocular isolates. Ocular isolates were significantly more likely to possess cna (p = 0.03), icaR (p = 0.01), sea (p = 0.001), set16 (p = 0.01), and set19 (p = 0.03). In contrast non-ocular isolates were more likely to possess icaD (p = 0.007), lukF-PV, lukS-PV (p = 0.01), selq (p = 0.01), set30 (p = 0.01), set32 (p = 0.02), and set36 (p = 0.02). The clones ST5, ST8, CC30, and CC1 among ocular isolates generally reflect circulating non-ocular pathogenic S. aureus strains. The higher rates of genes in infectious and ocular isolates suggest a potential role of these virulence factors in ocular diseases.

Sulfated Cyclocarya paliurus polysaccharides improve immune function of immunosuppressed mice by modulating intestinal microbiota

The study was aimed to investigate the effect of Cyclocarya paliurus polysaccharides (CPP) and the sulfation derivative (S-CPP) on modulate intestinal mucosal immunity and intestinal microbiota in cyclophosphamide-induced mice. The results showed that CPP and S-CPP effectively alleviated intestinal villi injury, enhanced the contents of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in small intestinal tissue and serum, and upregulated IL-1β at gene levels, zonula occludens-1 (ZO-1), Occludin and Claudin-1 at gene and protein levels, thereby promoting the repair of intestinal mechanical barrier and enhancing intestinal mucosal immunity. Moreover, the beneficial modulation of CPP and S-CPP on the overall structure of intestinal microbiota was revealed by performing 16S ribosomal RNA (16S rRNA) sequencing. Sulfated modification could improve the protection of CPP on the intestinal barrier and the regulation of systemic immunity. S-CPP had a stronger potential to reduce the damage of cyclophosphamide (Cy) on immunity and intestinal microbiota.

Fluorescent dyes with multiple quaternary ammonium centers for specific image discrimination and Gram-positive antibacterial activity

Three quaternary ammonium compounds (QACs), TPQA, T2PQA, and T3PQA, were synthesized and employed in antimicrobial tests against E. coli and S. aureus. It was confirmed that they exhibit selective bacteriostasis against S. aureus. The antibacterial activities of the compounds were evaluated via determining their minimum inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) against S. aureus using the 2,3,5-triphenyltetrazolium chloride (TTC) coloration method. Notably, T2PQA exhibited far better properties than TPQA and T3PQA, with the activity found to be dependent on the structure of the QA and the exposed hydrophobic groups. All three compounds showed promising potential for killing Gram-positive bacteria, efficiently guided by fluorescence imaging.

Structural insights into DNA binding domain of vancomycin-resistance-associated response regulator in complex with its promoter DNA from Staphylococcus aureus

In Staphylococcus aureus, vancomycin-resistance-associated response regulator (VraR) is a part of the VraSR two-component system, which is responsible for activating a cell wall-stress stimulon in response to an antibiotic that inhibits cell wall formation. Two VraR-binding sites have been identified: R1 and R2 in the vraSR operon control region. However, the binding of VraR to a promoter DNA enhancing downstream gene expression remains unclear. VraR contains a conserved N-terminal receiver domain (VraRN ) connected to a C-terminal DNA binding domain (VraRC ) with a flexible linker. Here, we present the crystal structure of VraRC alone and in complex with R1-DNA in 1.87- and 2.0-Å resolution, respectively. VraRC consisting of four α-helices forms a dimer when interacting with R1-DNA. In the VraRC -DNA complex structure, Mg2+ ion is bound to Asp194. Biolayer interferometry experiments revealed that the addition of Mg2+ to VraRC enhanced its DNA binding affinity by eightfold. In addition, interpretation of NMR titrations between VraRC with R1- and R2-DNA revealed the essential residues that might play a crucial role in interacting with DNA of the vraSR operon. The structural information could help in designing and screening potential therapeutics/inhibitors to deal with antibiotic-resistant S. aureus via targeting VraR.

Optimal exposure targets for vancomycin in the treatment of neonatal coagulase-negative Staphylococcus infection: A retrospective study based on electronic medical records

BACKGROUND

The currently advocated ratio of area under the curve (AUC) over 24 h to minimum inhibitory concentration (AUC/MIC) > 400 and AUC < 600 mg h/L as the therapeutic drug monitoring (TDM) target of vancomycin is based on data from multiple observational studies in adult patients with methicillin-resistant Staphylococcus aureus (MRSA) infection. It may not be applicable to newborns with coagulase-negative Staphylococcus (CoNS) infection. We conducted a retrospective study to identify the optimal exposure targets for vancomycin in the treatment of neonatal CoNS infection.

METHODS

Based on the inclusion and exclusion criteria, serum vancomycin concentration, demographics, clinical data, and related laboratory data of newborns who received vancomycin intravenous infusion from June 1, 2016 to February 1, 2021 were collected retrospectively. The AUC was calculated using the maximum a posteriori Bayesian (MAPB) method. The vancomycin exposure threshold of AUC/MIC for efficacy and AUC for toxicity (acute kidney injury, AKI) were determined based on receiver operating characteristic (ROC) curve analysis. The correlation between vancomycin exposure and both clinical effect and nephrotoxicity was analyzed using logistic multivariate regression.

RESULTS

In total, 153 patients and 245 vancomycin concentrations (160 trough and 85 peak concentrations) were included. The ROC curve analysis showed that the exposure thresholds of AUC/MIC for clinical efficacy and AUC for nephrotoxicity were 281 and 602 mg h/L, respectively. The multivariate regression analysis showed that AUC/MIC > 280 was a predictor of efficacy (OR: 13.960, 95% CI: 1.891-103.078, P < 0.05) and AUC > 600 mg h/L was associated with AKI (OR: 9.008, 95% CI: 2.706-29.983, P < 0.05). The vancomycin AUC/MIC threshold for treating neonatal CoNS infection with vancomycin is lower than the currently advocated AUC/MIC >400.

CONCLUSION

The optimal exposure targets for vancomycin in neonatal CoNS infection were AUC/MIC > 280 and AUC < 600 mg h/L.

Recent Developments in Methicillin-Resistant Staphylococcus aureus (MRSA) Treatment: A Review

Staphylococcus aureus (S. aureus) is a Gram-positive bacterium that may cause life-threatening diseases and some minor infections in living organisms. However, it shows notorious effects when it becomes resistant to antibiotics. Strain variants of bacteria, viruses, fungi, and parasites that have become resistant to existing multiple antimicrobials are termed as superbugs. Methicillin is a semisynthetic antibiotic drug that was used to inhibit staphylococci pathogens. The S. aureus resistant to methicillin is known as methicillin-resistant Staphylococcus aureus (MRSA), which became a superbug due to its defiant activity against the antibiotics and medications most commonly used to treat major and minor infections. Successful MRSA infection management involves rapid identification of the infected site, culture and susceptibility tests, evidence-based treatment, and appropriate preventive protocols. This review describes the clinical management of MRSA pathogenesis, recent developments in rapid diagnosis, and antimicrobial treatment choices for MRSA.

Structure and role of the linker domain of the iron surface-determinant protein IsdH in heme transportation in Staphylococcus aureus

Staphylococcus aureus is a major cause of deadly nosocomial infections, a severe problem fueled by the steady increase of resistant bacteria. The iron surface determinant (Isd) system is a family of proteins that acquire nutritional iron from the host organism, helping the bacterium to proliferate during infection, and therefore represents a promising antibacterial target. In particular, the surface protein IsdH captures hemoglobin (Hb) and acquires the heme moiety containing the iron atom. Structurally, IsdH comprises three distinctive NEAr-iron Transporter (NEAT) domains connected by linker domains. The objective of this study was to characterize the linker region between NEAT2 and NEAT3 from various biophysical viewpoints and thereby advance our understanding of its role in the molecular mechanism of heme extraction. We demonstrate the linker region contributes to the stability of the bound protein, likely influencing the flexibility and orientation of the NEAT3 domain in its interaction with Hb, but only exerts a modest contribution to the affinity of IsdH for heme. Based on these data, we suggest that the flexible nature of the linker facilitates the precise positioning of NEAT3 to acquire heme. In addition, we also found that residues His45 and His89 of Hb located in the heme transfer route toward IsdH do not play a critical role in the transfer rate-determining step. In conclusion, this study clarifies key elements of the mechanism of heme extraction of human Hb by IsdH, providing key insights into the Isd system and other protein systems containing NEAT domains.

Clinical Presentation and Management of Methicillin-Resistant Staphylococcus aureus Pericarditis—Systematic Review

In the expanding era of antibiotic resistance, new strains of Staphylococcus aureus have emerged which possess resistance to traditionally used antibiotics (MRSA). Our review aimed to systematically synthesize information on previously described MRSA pericarditis cases. The only criterion for inclusion was the isolation of MRSA from the pericardial space. Our review included 30 adult and 9 pediatric patients (aged: 7 months to 78 years). Comorbid conditions were seen in most adult patients, whereas no comorbidities were noted amongst the pediatric patients. Pericardial effusion was found in 94.9% of cases, with evidence of tamponade in 83.8%. All cases isolated MRSA from pericardial fluid and 25 cases (64.1%) had positive blood cultures for MRSA. Pericardiocentesis and antibiotics were used in all patients. The mortality rate amongst adults was 20.5%, with a mean survival of 21.8 days, and attributed to multi-organ failure associated with septic shock. No mortality was observed in the pediatric population. In adult patients, there was no statistical difference in symptom duration, antibiotic duration, presence of tamponade, age, and sex in relation to survival. Conclusion: MRSA pericarditis often presents with sepsis and is associated with significant mortality. As such, a high clinical suspicion is needed to proceed with proper tests such as echocardiography and pericardiocentesis. In more than one third of the cases, MRSA pericarditis occurs even in the absence of documented bacteremia.

The Use of Antibody-Antibiotic Conjugates to Fight Bacterial Infections

The emergence of antimicrobial resistance (AMR) is rapidly increasing and it is one of the significant twenty-first century's healthcare challenges. Unfortunately, the development of effective antimicrobial agents is a much slower and complex process compared to the spread of AMR. Consequently, the current options in the treatment of AMR are limited. One of the main alternatives to conventional antibiotics is the use of antibody-antibiotic conjugates (AACs). These innovative bioengineered agents take advantage of the selectivity, favorable pharmacokinetic (PK), and safety of antibodies, allowing the administration of more potent antibiotics with less off-target effects. Although AACs' development is challenging due to the complexity of the three components, namely, the antibody, the antibiotic, and the linker, some successful examples are currently under clinical studies.

Trends of Antimicrobial Susceptibility in Clinically Significant Coagulase-Negative Staphylococci Isolated from Cerebrospinal Fluid Cultures in Neurosurgical Adults: a Nine-Year Analysis

Coagulase-negative staphylococci (CoNS) are the main pathogens in health care-associated ventriculitis and meningitis (HCAVM). This study aimed to assess antimicrobial susceptibility. Moreover, the treatment and clinical outcome were described. All neurosurgical adults admitted to one of the largest neurosurgical centers in China with clinically significant CoNS isolated from cerebrospinal fluid cultures in 2012 to 2020 were recruited. One episode was defined as one patient with one bacterial strain. Interpretive categories were applied according to the MICs. The clinical outcomes were dichotomized into poor (Glasgow Outcome Scale 1 to 3) and acceptable (Glasgow Outcome Scale 4 to 5). In total, 534 episodes involving 519 patients and 16 bacteria were analyzed. Over the 9 years, eight antimicrobial agents were used in antimicrobial susceptibility tests, including six in over 80% of CoNS. The range of resistance rates was 0.8% to 84.6%. The vancomycin resistance rate was the lowest, whereas the penicillin resistance rate was the highest. The linezolid (a vancomycin replacement) resistance rate was 3.1%. The rate of oxacillin resistance, representing methicillin-resistant staphylococci, was 70.2%. There were no significant trends of antimicrobial susceptibility over the 9 years for any agents analyzed. However, there were some apparent changes. Notably, vancomycin-resistant CoNS appeared in recent years, while linezolid-resistant CoNS appeared early and disappeared in recent years. Vancomycin (or norvancomycin), the most common treatment agent, was used in 528 (98.9%) episodes. Finally, 527 (98.7%) episodes had acceptable outcomes. It will be safe to use vancomycin to treat CoNS-related HCAVM in the immediate future, although continuous monitoring will be needed. IMPORTANCE Coagulase-negative staphylococci are the main pathogens in health care-associated ventriculitis and meningitis. There are three conclusions from the results of this study. First, according to antimicrobial susceptibility, the rates of resistance to primary antimicrobial agents are high and those to high-level agents, including vancomycin, are low. Second, the trends of resistance rates are acceptable, especially for high-level agents, although long-term and continuous monitoring is necessary. Finally, the clinical outcomes of neurosurgical adults with coagulase-negative staphylococci-related health care-associated ventriculitis and meningitis are acceptable after treatment with vancomycin. Therefore, according to the antimicrobial susceptibility and clinical practice, vancomycin will be safe to treat coagulase-negative staphylococci-related health care-associated ventriculitis and meningitis.

The Candidate Antigens to Achieving an Effective Vaccine against Staphylococcus aureus

Staphylococcus aureus (S. aureus) is an opportunistic pathogen that causes various inflammatory local infections, from those of the skin to postinfectious glomerulonephritis. These infections could result in serious threats, putting the life of the patient in danger. Antibiotic-resistant S. aureus could lead to dramatic increases in human mortality. Antibiotic resistance would explicate the failure of current antibiotic therapies. So, it is obvious that an effective vaccine against S. aureus infections would significantly reduce costs related to care in hospitals. Bacterial vaccines have important impacts on morbidity and mortality caused by several common pathogens, however, a prophylactic vaccine against staphylococci has not yet been produced. During the last decades, the efforts to develop an S. aureus vaccine have faced two major failures in clinical trials. New strategies for vaccine development against S. aureus has supported the use of multiple antigens, the inclusion of adjuvants, and the focus on various virulence mechanisms. We aimed to present a compressive review of different antigens of S. aureus and also to introduce vaccine candidates undergoing clinical trials, from which can help us to choose a suitable and effective candidate for vaccine development against S. aureus.

Pathogen Control in the Built Environment: A Probiotic-Based System as a Remedy for the Spread of Antibiotic Resistance

The high and sometimes inappropriate use of disinfectants and antibiotics has led to alarming levels of Antimicrobial Resistance (AMR) and to high water and hearth pollution, which today represent major threats for public health. Furthermore, the current SARS-CoV-2 pandemic has deeply influenced our sanitization habits, imposing the massive use of chemical disinfectants potentially exacerbating both concerns. Moreover, super-sanitation can profoundly influence the environmental microbiome, potentially resulting counterproductive when trying to stably eliminate pathogens. Instead, environmentally friendly procedures based on microbiome balance principles, similar to what applied to living organisms, may be more effective, and probiotic-based eco-friendly sanitation has been consistently reported to provide stable reduction of both pathogens and AMR in treated-environments, compared to chemical disinfectants. Here, we summarize the results of the studies performed in healthcare settings, suggesting that such an approach may be applied successfully also to non-healthcare environments, including the domestic ones, based on its effectiveness, safety, and negligible environmental impact.

Galangin as a direct inhibitor of vWbp protects mice from Staphylococcus aureus-induced pneumonia

The surge in multidrug resistance in Staphylococcus aureus (S. aureus) and the lag in antibiotic discovery necessitate the development of new anti‐infective strategies to reduce S. aureus infections. In S. aureus, von Willebrand factor‐binding protein (vWbp) is not only the main coagulase that triggers host prothrombin activation and formation of fibrin cables but also bridges the bacterial cell wall and von Willebrand factor, thereby allowing S. aureus to bind to platelets and endothelial cells, playing a vital role in pathogenesis of S. aureus infections. Here, we have identified that galangin, a bioactive compound found in honey and Alpinia officinarum Hance, is a potent and direct inhibitor of vWbp by coagulation activity inhibition assay, thermal shift assay and biolayer interferometry assay. Molecular dynamic simulations and verification experiments revealed that the Trp‐64 and Leu‐69 residues are necessary for the binding of galangin to vWbp. Significantly, galangin attenuated S. aureus virulence in a mouse S. aureus‐induced pneumonia model. In addition, we also identified that galangin can enhance the therapeutic effect of latamoxef on S. aureus‐induced pneumonia. Taken together, the results suggest that galangin may be used for the development of therapeutic drugs or utilized as adjuvants to combine with antibiotics to combat S. aureus‐related infections.

Inducible Clindamycin Resistance and Biofilm Production among Staphylococci Isolated from Tertiary Care Hospitals in Nepal

Resistance to antibiotics, biofilm formation and the presence of virulence factors play important roles in increased mortality associated with infection by staphylococci. The macrolide lincosamide streptogramin B (MLS_B) family of antibiotics is commonly used to treat infections by methicillin-resistant isolates. Clinical failure of clindamycin therapy has been reported due to multiple mechanisms that confer resistance to MLS_B. This study aims to find the incidence of different phenotypes of MLS_B resistance and biofilm production among staphylococci. A total of 375 staphylococci were isolated from different clinical samples, received from two tertiary care hospitals in Nepal. Methicillin resistance was detected by cefoxitin disc diffusion method and inducible clindamycin resistance by D test, according to CLSI guidelines. Biofilm formation was detected by the tissue culture plate method and PCR was used to detect ica genes. Of the total staphylococci isolates, 161 (42.9%) were Staphylococcus aureus, with 131 (81.4%) methicillin-resistant strains, and 214 (57.1%) isolates were coagulase-negative staphylococci, with 143 (66.8%) methicillin-resistant strains. The overall prevalence of constitutive MLS_B (cMLS_B) and inducible MLS_B (iMLS_B) phenotypes was 77 (20.5%) and 87 (23.2%), respectively. Both iMLS_B and cMLS_B phenotypes predominated in methicillin-resistant isolates. The tissue culture plate method detected biofilm formation in 174 (46.4%) isolates and ica genes in 86 (22.9%) isolates. Among biofilm producing isolates, cMLS_B and iMLS_B phenotypes were 35 (20.1%) and 27 (15.5%), respectively. The cMLS_B and iMLS_B were 11 (12.8%) and 19 (22.1%), respectively, in isolates possessing ica genes. Clindamycin resistance in the form of cMLS_B and iMLS_B, especially among MRSA, emphasizes the need for routine D tests to be performed in the lab.

Three Lipid Emulsions Reduce Staphylococcus aureus-Stimulated Phagocytosis in Mouse RAW264.7 Cells

Soybean oil (SO)-, SO medium-chain triglyceride (MCT)-, olive oil (OO)-, and fish oil (FO)-based lipid emulsions are generally applied in clinical practice via intravenous injection for patients with nutritional requirements. The function of lipid emulsions on immune modulation remains inconsistent, and their effects on macrophages are limited. In the present study, we used a model of S. aureus-infected mouse RAW264.7 macrophages to determine the influence of three different compositions of lipid emulsions (Lipofundin, ClinOleic, and Omegaven) on reactive oxygen species (ROS) production, phagocytosis, and bacterial survival. The three individual lipid emulsions similarly enhanced bacterial survival but reduced S. aureus-stimulated ROS, phagocytosis of S. aureus bioparticles conjugate, polymerization of F-actin, and phosphorylation of AKT, JNK, and ERK. Compared with the JNK and ERK inhibitors, the PI3K inhibitor markedly suppressed the phagocytosis of S. aureus bioparticles conjugate and the polymerization of F-actin, whereas it significantly increased the bacterial survival. These results suggest that the three lipid emulsions diminished ROS production and phagocytosis, resulting in increased bacterial survival. PI3K predominantly mediated the inhibitory effects of the lipid emulsions on the phagocytosis of mouse RAW264.7 macrophages.

Photodynamic antimicrobial chemotherapy coupled with the use of the photosensitizers methylene blue and temoporfin as a potential novel treatment for Staphylococcus aureus in burn infections

Photodynamic antimicrobial chemotherapy (PACT) is a novel alternative antimicrobial therapy that elicits a broad mechanism of action and therefore has a low probability of generating resistance. Such properties make PACT ideally suited for utilization in localized applications such as burn wounds. The aim of this study was to determine the antimicrobial activity of MB and temoporfin against both a S. aureus isolate and a P. aeruginosa isolate in light (640 nm) and dark conditions at a range of time points (0–20 min). A Staphylococcus aureus isolate and a Pseudomonas aeruginosa isolate were treated in vitro with methylene blue (MB) and temoporfin under different conditions following exposure to light at 640 nm and in no-light (dark) conditions. Bacterial cell viability [colony-forming units (c.f.u.) ml⁻¹] was then calculated. Against P. aeruginosa, when MB was used as the photosensitizer, no phototoxic effect was observed in either light or dark conditions. After treatment with temoporfin, a reduction of less than one log (7.00×10⁷ c.f.u. ml⁻¹) was observed in the light after 20 min of exposure. However, temoporfin completely eradicated S. aureus in both light and dark conditions after 1 min (where a seven log reduction in c.f.u. ml⁻¹ was observed). Methylene blue resulted in a loss of S. aureus viability, with a two log reduction in bacterial viability (c.f.u. ml⁻¹) reported in both light and dark conditions after 20 min exposure time. Temoporfin demonstrated greater antimicrobial efficacy than MB against both the S. aureus and P. aeruginosa isolates tested. At 12.5 µM temoporfin resulted in complete eradication of S. aureus. In light of this study, further research into the validity of PACT, coupled with the photosensitizers (such as temoporfin), should be conducted in order to potentially develop alternative antimicrobial treatment regimes for burn wounds.

Disinfectant and Antimicrobial Susceptibility Studies of Staphylococcus aureus Strains and ST398-MRSA and ST5-MRSA Strains from Swine Mandibular Lymph Node Tissue, Commercial Pork Sausage Meat and Swine Feces

Staphylococcus aureus (S. aureus) causes gastrointestinal illness worldwide. Disinfectants are used throughout the food chain for pathogenic bacteria control. We investigated S. aureus bioavailability in swine Mandibular lymph node tissue (MLT) and pork sausage meat (PSM), established susceptibility values for S. aureus to disinfectants, and determined the multilocus sequence type of MRSA strains. Antimicrobial and disinfectant susceptibility profiles were determined for 164 S. aureus strains isolated from swine feces (n = 63), MLT (n = 49) and PSM (n = 52). No antimicrobial resistance (AMR) was detected to daptomycin, nitrofurantoin, linezolid, and tigecycline, while high AMR prevalence was determined to erythromycin (50.6%), tylosin tartrate (42.7%), penicillin (72%), and tetracycline (68.9%). Methicillin-resistant S. aureus (MRSA) strains, ST398 (n = 6) and ST5 (n = 1), were found in the MLT and PSM, 4 MRSA in MLT and 3 MRSA strains in the PSM. About 17.5% of feces strains and 41.6% of MLT and PSM strains were resistant to chlorhexidine. All strains were susceptible to triclosan and benzalkonium chloride, with no cross-resistance between antimicrobials and disinfectants. Six MRSA strains had elevated susceptibilities to 18 disinfectants. The use of formaldehyde and tris(hydroxylmethyl)nitromethane in DC&R was not effective, which can add chemicals to the environment. Didecyldimethylammonium chloride and benzyldimethylhexadecylammonium chloride were equally effective disinfectants. ST398 and ST5 MRSA strains had elevated susceptibilities to 75% of the disinfectants tested. This study establishes susceptibility values for S. aureus strains from swine feces, mandibular lymph node tissue, and commercial pork sausage against 24 disinfectants. Since it was demonstrated that S. aureus and MRSA strains can be found deep within swine lymph node tissue, it may be beneficial for the consumer if raw swine lymph node tissue is not used in uncooked food products and pork sausage.

New Perspectives on Old and New Therapies of Staphylococcal Skin Infections: The Role of Biofilm Targeting in Wound Healing

Among the most common complications of both chronic wound and surgical sites are staphylococcal skin infections, which slow down the wound healing process due to various virulence factors, including the ability to produce biofilms. Furthermore, staphylococcal skin infections are often caused by methicillin-resistant Staphylococcus aureus (MRSA) and become a therapeutic challenge. The aim of this narrative review is to collect the latest evidence on old and new anti-staphylococcal therapies, assessing their anti-biofilm properties and their effect on skin wound healing. We considered antibiotics, quorum sensing inhibitors, antimicrobial peptides, topical dressings, and antimicrobial photo-dynamic therapy. According to our review of the literature, targeting of biofilm is an important therapeutic choice in acute and chronic infected skin wounds both to overcome antibiotic resistance and to achieve better wound healing.

Ginsenoside 20(S)-Rh2 promotes cellular pharmacokinetics and intracellular antibacterial activity of levofloxacin against Staphylococcus aureus through drug efflux inhibition and subcellular stabilization

Intracellular Staphylococcus aureus (S. aureus) often causes clinical failure and relapse after antibiotic treatment. We previously found that 20(S)-ginsenoside Rh2 [20(S)-Rh2] enhanced the therapeutic effect of quinolones in a mouse model of peritonitis, which we attributed to the increased concentrations of quinolones within bacteria. In this study, we investigated the enhancing effect of 20(S)-Rh2 on levofloxacin (LVF) from a perspective of intracellular bacteria. In S. aureus 25923-infected mice, coadministration of LVF (1.5 mg/kg, i.v.) and 20(S)-Rh2 (25, 50 mg/kg, i.g.) markedly increased the survival rate, and decreased intracellular bacteria counts accompanied by increased accumulation of LVF in peritoneal macrophages. In addition, 20(S)-Rh2 (1, 5, 10 μM) dose-dependently increased the uptake and accumulation of LVF in peritoneal macrophages from infected mice without drug treatment. In a model of S. aureus 25923-infected THP-1 macrophages, we showed that 20(S)-Rh2 (1, 5, 10 μM) dose-dependently enhanced the intracellular antibacterial activity of LVF. At the cellular level, 20(S)-Rh2 increased the intracellular accumulation of LVF by inhibiting P-gp and BCRP. PK-PD modeling revealed that 20(S)-Rh2 altered the properties of the cell but not LVF. At the subcellular level, 20(S)-Rh2 did not increase the distribution of LVF in lysosomes but exhibited a stronger sensitizing effect in acidic environments. Molecular dynamics (MD) simulations showed that 20(S)-Rh2 improved the stability of the DNA gyrase-LVF complex in lysosome-like acidic conditions. In conclusion, 20(S)-Rh2 promotes the cellular pharmacokinetics and intracellular antibacterial activities of LVF against S. aureus through efflux transporter inhibition and subcellular stabilization, which is beneficial for infection treatment.

Recombinant expression and coexpression of oyster defensin and proline-rich peptide in Komagataella phaffii

Proline-rich peptide (CgPrp) and defensin (CgDef), oyster (Crassostrea gigas)-originated antimicrobial peptides (AMPs), were produced by the recombinant technique in Komagataella phaffii GS115 cells. For this purpose, the nucleotide sequences encoding the CgPrp and CgDef peptides were synthesized by the recursive PCR technique, and ligated in pPICZaA expression vector. Additionally, the expression cassettes of pPICZαA-CgDef and pPICZαA-CgPrp were combined using in vitro multimer ligation strategy to construct the coexpression vector pPICZaA-CgPrp-CgDef. The expression and coexpression vectors transformed into K. phaffii GS115 cells by electroporation. At the end of the 0.5% methanol-induced expression stage for 96 h, the recombinant peptides were purified from the culture medium. The concentrations of purified peptides were changed between 1.05 and 1.21 mg/L. The recombinant peptides successfully inhibited the growth of tested Gram-positive bacterial strains belonging to Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Listeria monocytogenes, and Bacillus cereus. The minimum inhibitory concentrations (MIC) of recombinant CgPrp, CgDef, and CgPrp-CgDef peptides against tested bacteria were in the range of 12.50-25.00, 18.75-75.00, and 5.80-11.60 pg/μl, respectively. The results of the study proved that the recombinant CgPrp, CgDef, and CgPrp-CgDef peptides expressed in K. phaffii might have good potential for the inhibition of common Gram-positive pathogenic bacteria, including drug-resistant MRSA.

Chemical Biology of Sortase A Inhibition: A Gateway to Anti-infective Therapeutic Agents

Staphylococcus aureus is the leading cause of hospital-acquired infections. The enzyme sortase A, present on the cell surface of S. aureus, plays a key role in bacterial virulence without affecting the bacterial viability. Inhibition of sortase A activity offers a powerful but clinically less explored therapeutic strategy, as it offers the possibility of not inducing any selective pressure on the bacteria to evolve drug-resistant strains. In this Perspective, we offer a chemical space narrative for the design of sortase A inhibitors, as delineated into three broad domains: peptidomimetics, natural products, and synthetic small molecules. This provides immense opportunities for medicinal chemists to alleviate the ever-growing crisis of antibiotic resistance.

Integrated Multi-omics, Virtual Screening and Molecular Docking Analysis of Methicillin-Resistant Staphylococcus aureus USA300 for the Identification of Potential Therapeutic Targets: An In-Silico Approach

Staphylococcus aureus infection is a leading cause of mortality and morbidity in community, hospital and live-stock sectors, especially with the widespread emergence of methicillin-resistant S. aureus (MRSA) strains. To identify new drug molecules to treat MRSA patients, we have undertaken to search essential proteins that are indispensable for their survival but non-homologous to human host proteins. The current study utilizes a subtractive genome and proteome approach to screen the possible therapeutic targets against S. aureus USA300. Bacterial essential genes are obtained from the DEG database and are compared to avoid cross-reactivity with human host genes. In silico analysis shows 198 proteins that may be considered as therapeutic candidates. Depending on their sub-cellular localization, proteins are grouped as either vaccine or drug targets or both. Extracellular proteins such as cell division proteins (Q2FZ91, Q2FZ95), penicillin-binding proteins (Q2FZ94, Q2FYI0) of the bacterial cell wall, phosphoglucomutase (Q2FE11) and lipoteichoic acid synthase (Q2FIS2) are considered as vaccine targets, and their epitopes have been mapped. Altogether, 53 drug targets are identified, which have shown similarity with the drug targets available in the DrugBank database. Predicted drug targets belong to the common metabolic pathways of MRSA, such as fatty acid biosynthesis, folate biosynthesis, peptidoglycan biosynthesis, ribosome, etc. Protein-protein interaction analysis emphasizing peptidoglycan biosynthesis reveals the connection between penicillin-binding proteins, mur-family proteins and FemXAB proteins. In this study, staphylococcal FemA protein (P0A0A5) is subjected to structure-based virtual screening for the drug repurposing approach. There are 20 residues missing in the crystal structure of FemA, and 12 of these residues are located at the catalytic site. The missing residues are modelled, and stereochemistry is checked. FDA approved drugs available in the DrugBank database have been used in virtual screening with FemA in search of potential repurposed molecules. This approach provides us with 10 drugs that may be used in the treatment of methicillin-resistant staphylococcal mediated diseases. AutoDock 4.2 is used for in silico screening and shows a comparable inhibition constant (Ki) for all 10 FDA-approved drugs towards FemA. Most of these drugs are used in the treatment of various cancers, migraines and leukaemia. Protein-drug interaction analysis shows that the drugs mostly interact with hydrophobic residues of FemA. Moreover, Tyr328 and Lys383 contribute largely to hydrogen bondings during interactions. All interacting amino acids that bind to the drugs are part of the active site cavity of FemA.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10989-021-10287-9.

Characterizing a novel SCCmec with a composite structure from a clinical strain of Staphylococcus hominis, C34847

Staphylococcal cassette chromosome mec (SCCmec) has predominantly been described in methicillin-resistant Staphylococcus aureus. However, studies have indicated that coagulase-negative staphylococci (CoNS) carry a larger diversity of SCC elements. We characterized a composite SCCmec element carrying an uncharacterized ccr1 and type A mec gene combination, in conjunction with a secondary element bearing ccr4, from a clinical strain of S. hominis. The element's complex structure points to a high degree of recombination occurring in SCCmec in CoNS.

Coagulase-Negative Staphylococci Clones Are Widely Distributed in the Hospital and Community

Coagulase-negative staphylococci (CoNS) may be considered contaminants when isolated from clinical specimens but may also be a cause of true infection. This study aimed to compare the clonality and SCCmec type of a collection of CoNS isolated from blood cultures of inpatients, nasal swabs of healthy individuals, and patients with chronic wounds, all from the same community, using SCCmec typing, pulsed-field gel electrophoresis (PFGE), and MLST. Staphylococcus epidermidis, exhibited high clonal diversity, but hospital and community clusters were observed. Nosocomial S. epidermidis clones belonged to sequence types ST2, ST6, and ST23. Some Staphylococcus haemolyticus clones were found to circulate in the hospital and community, while Staphylococcus saprophyticus exhibited very high clonal diversity. Staphylococcus lugdunensis, Staphylococcus warneri, and Staphylococcus capitis revealed several isolates belonging to the same clone in the hospital and community. The detection of different SCCmec types within the same cluster indicated high diversity. S. epidermidis was associated with SCCmec I and III, S. haemolyticus with I and II, S. capitis with type V, Staphylococcus hominis with mec complex type A and ccr1, and S. warneri and S. saprophyticus with SCCmec I. The generation of elements and new combinations of cassette genes were highly associated with CoNS isolates, suggesting that SCCmec may not be a good marker of clonality in these bacteria.

An overview of research of essential oils by self-organizing maps: A novel approach for meta-analysis study

Essential oils (EOs) are commercially important products, sources of compounds with antioxidant and antimicrobial activities considered indispensable for several fields, such as the food industry, cosmetics, perfumes, pharmaceuticals, sanitary and agricultural industries. In this context, this systematic review and meta-analysis, a novel approach will be presented using chemometric tools to verify and recognize patterns of antioxidant, antibacterial, and antifungal activities of EOs according to their geographic, botanical, chemical, and microbiological distribution. Scientific papers were selected following the Preferred Reporting Items for Systematic Review and Meta-Analyses statement flow diagram, and the data were evaluated by the self-organizing map and hierarchical cluster analysis. Overall, this novel approach allowed us to draw an overview of antioxidants and antimicrobials activities of EOs reported in 2019, through 585 articles evaluated, obtaining a dataset with more than 10,000 data, distributed in more than 80 countries, 290 plant genera, 150 chemical compounds, 30 genera of bacteria, and 10 genera of fungi. The networks for geographic, botanical, chemical, and microbiological distribution indicated that Brazil, Asia, the botanical genus Thymus, species Thymus vulgaris L. "thyme," the Lamiaceae family, limonene, and the oxygenated monoterpene class were the most representative in the dataset, while the species Escherichia coli and Candida albicans were the most used to assess the antimicrobial activity of EOs. This work can be seen as a guide for the processing of metadata using a novel approach with non-conventional statistical methods. However, this preliminary approach with EOs can be extended to other sources or areas of food science.

Methicillin-Resistant Staphylococcus Aureus Bacteremia: Epidemiology, Clinical Characteristics, Risk Factors, and Outcomes in a Tertiary Care Center in Riyadh, Saudi Arabia

Background

Methicillin-resistant Staphylococcus aureus (MRSA) has become increasingly common in hospitals worldwide. In an era of pandemics, it is important to understand all types of infectious diseases in order to control its outcome and reduce mortality rates related to it. This study aims to identify the epidemiology of MRSA bloodstream infection, risk factors, and mortality in King Abdulaziz Medical City in Riyadh.

Methods

This is a retrospective chart review study from January 2013 to June 2017. All patients with positive blood culture for MRSA at King Abdulaziz Medical City (KAMC), which is a tertiary care center in Riyadh, Saudi Arabia, were included. Data were extracted from electronic and paper medical records for patients who had a positive blood culture for MRSA. Data collected included demographics, microbiological details, risk factors, and 30-day mortality.

Results

From 2013 through June 2017, 633 Staphylococcus aureus bacteremia were reported in KAMC, of which 184 (29.1%) were MRSA with a mean age of 60±19 years. Almost all of our isolates were susceptible to vancomycin, linezolid, and tigecycline. The most common infectious syndrome these patients presented with was an endovascular infection which accounts for 30.4% while 19.9% presented as a case of pneumonia. The mortality within 30 days of collection of the positive blood culture was 20.65%. Male gender (OR = 2.33; 95% CI = 1.34-4.05; P-value = 0.003) and patients with history of recent hospital (OR = 2.34; 95% CI = 1.27-4.34; P-value = 0.007) or ICU (OR = 1.66; 95% CI = 1.09-2.52; P-value = 0.018) admissions were more likely to acquire MRSA.

Conclusions

The incidence of MRSA bacteremia at King Abdulaziz Medical City is high and increasing in conjunction with incidence rate posing a significantly high rate of mortality. Recent history of hospital admission, ICU admission and males were found to be significantly associated with higher rates of MRSA infection. Some modifiable risk factors that could be used to facilitate the reduction of MRSA acquisition rates is to avoid unnecessary hospital and ICU admissions.

Recent Advances in Peptide Nucleic Acids as Antibacterial Agents

The emergence of antibiotic-resistant bacteria and the slow progress in searching for new antimicrobial agents makes it hard to treat bacterial infections and cause problems for the healthcare system worldwide, including high costs, prolonged hospitalizations, and increased mortality. Therefore, the discovery of effective antibacterial agents is of great importance. One attractive alternative is antisense peptide nucleic acid (PNA), which inhibits or eliminates gene expression by binding to the complementary messenger RNA (mRNA) sequence of essential genes or the accessible and functionally important regions of the ribosomal RNA (rRNA). Following 30 years of development, PNAs have played an extremely important role in the treatment of Gram-positive, Gram-negative, and acidfast bacteria due to their desirable stability of hybrid complex with target RNA, the strong affinity for target mRNA/rRNA, and the stability against nucleases. PNA-based antisense antibiotics can strongly inhibit the growth of pathogenic and antibiotic-resistant bacteria in a sequence-specific and dose-dependent manner at micromolar concentrations. However, several fundamental challenges, such as intracellular delivery, solubility, physiological stability, and clearance still need to be addressed before PNAs become broadly applicable in clinical settings. In this review, we summarize the recent advances in PNAs as antibacterial agents and the challenges that need to be overcome in the future.