Clinical, Epidemiologic, and Laboratory Aspects of Methicillin-Resistant Staphylococcus aureus Infections

Steamed panax notoginseng mitigates CA-MRSA USA300-induced necroptosis in human neutrophils

Background

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) disrupts innate immunity by inducing necroptosis in polymorphonuclear neutrophils (PMNs), a process linked to excessive inflammation and tissue damage. CA-MRSA releases virulence factors that enhance its pathogenicity by disrupting the host's innate immune response, particularly impairing the phagocytic function of PMNs. Steamed Panax notoginseng (S-PN), a traditional Chinese medicine (TCM), has demonstrated immune-regulatory and anti-inflammatory properties, showing promising therapeutic effects in alleviating the severe inflammatory responses induced by pathogenic microbial infections.

Objective

This study aims to investigate the pharmacological effects and mechanisms of S-PN alleviating CA-MRSA-induced PMN necroptosis by suppressing MRSA virulence factors and inhibiting the RIPK1/RIPK3/MLKL signaling pathway, thereby attenuating inflammatory damage.

Methods

A co-culture model of MRSA USA300 strain and PMNs isolated from healthy human blood was established to observe the changes in necroptosis marker HMGB1, PMNs counts, ROS, chemokine MCP-1 and pro-inflammatory cytokines IL-1β, IL-8, TNF-α. RNA-seq was employed to analyze the effects of S-PN on the transcriptional expression of pathogenesis-related genes of MRSA. RT-PCR was utilized to validate the expression of S-PN on MRSA virulence factors and PMNs necroptosis related genes.

Results

S-PN significantly inhibited HMGB1, ROS, MCP-1, IL-1β and IL-8 in MRSA-PMN co-cultures, the PMN count in the S-PN group was higher than that in the model group. S-PN downregulated MRSA pathogenic-associated S. aureus infection and quorum sensing signaling pathways, and significantly reduced the virulence factors PSM and PVL. S-PN suppressed the expression of genes associated with necroptosis ripk1, ripk3, and mlkl in PMNs.

Conclusion

S-PN alleviates CA-MRSA infection-induced immune damage through dual mechanisms: suppression of bacterial virulence factors (PSM and PVL) and inhibition of PMNs necroptosis. These findings underscore its potential as a complementary therapeutic strategy against CA-MRSA infections, providing a theoretical foundation for integrating TCM into adjuvant treatments for drug-resistant bacterial infections.

Restoring susceptibility to β-lactam antibiotics in methicillin-resistant Staphylococcus aureus

Infections by Staphylococcus aureus have been treated historically with β-lactam antibiotics. However, these antibiotics have become obsolete in methicillin-resistant S. aureus by acquisition of the bla and mec operons. The presence of the β-lactam antibiotic is detected by the sensor domains of BlaR and/or MecR, and the information is transmitted to the cytoplasm, resulting in derepression of the antibiotic-resistance genes. We hypothesized that inhibition of the sensor domain would shut down this response system, and β-lactam susceptibility would be restored. An in silico search of 11 million compounds led to a benzimidazole-based hit and, ultimately, to the boronate 4. The X-ray structure of 4 is covalently engaged with the active-site serine of BlaR. Compound 4 potentiates by 16- to 4,096-fold the activities of oxacillin and of meropenem against methicillin-resistant S. aureus strains. The combination of 4 with oxacillin or meropenem shows efficacy in infected mice, validating the strategy.

BTS1-knockout Saccharomyces cerevisiae with broad-spectrum antimicrobial activity through lactic acid accumulation

Bacterial infections pose significant threats to human health, and prudent antibiotic use remains a key strategy for disease treatment and control. However, a global escalation of drug resistance among pathogenic bacteria presents a formidable challenge. Probiotics have emerged as a promising approach to combating pathogenic bacterial infections. In this study, we investigated the antibacterial activity of BTS1-knockout (BTS1-KO) Saccharomyces cerevisiae. Our findings demonstrate its effective inhibition of pathogen growth as evidenced by Minimum inhibitory concentration (MIC) assays, growth curves, bacteriostatic spectrum analyses and co-culture experiments. Additionally, it significantly impedes Escherichia coli and Staphylococcus aureus biofilm formation. Moreover, BTS1-KO S. cerevisiae exhibits low haemolytic activity, acid resistance, resistance to high bile salt concentrations, high auto-aggregation capacity and high co-aggregation capacities with pathogenic bacteria. Moreover, infected larvae treated with BTS1-KO S. cerevisiae in Galleria mellonella-E. coli (in vivo) and G. mellonella-S. aureus (in vivo) infection models showed significantly prolonged survival times. Mechanistic investigations revealed that BTS1-KO S. cerevisiae primarily produced lactic acid via metabolism, thereby lowering the environmental pH and inhibiting pathogenic bacterial growth. In summary, our study underscores the probiotic potential of BTS1-KO S. cerevisiae, offering broad-spectrum antibacterial activity in vitro and in vivo with low toxicity. This highlights BTS1-KO S. cerevisiae as a promising probiotic candidate for clinical prevention and control of bacterial infection.

Molecular Identification of Etiological Agents in Fungal and Bacterial Skin Infections: United States, 2020-2024

Background/Objectives: Cutaneous infections of fungal and bacterial origins are common. An accurate diagnosis-especially concerning pathogens that are difficult to isolate on culture-can be achieved using molecular methods (PCR) with a short turnaround time. Methods: We reviewed records of skin specimens (superficial scrapings) submitted by dermatologists across the United States with a clinically suspected dermatitis. As per physician's order, specimens were tested for infections either fungal (N = 4262) or bacterial (N = 1707) in origin. All unique specimens (one per patient) were subjected to real-time PCR assays where cases suspected of a fungal etiology were tested for dermatophytes, Malassezia and Candida, and cases suspected of a bacterial etiology were tested for Streptococcus pyogenes, Staphylococcus aureus, and the mecA gene potentially conferring β-lactam resistance. Results: Fungal agents were detected in 32.8% (SD: 4.5) of the submitted specimens, with most attributed to dermatophytes (19.3% (SD: 4.9)), followed by Malassezia (8.7% (SD: 2.8)) and Candida (2.9% (SD: 1.0)). Dermatophyte detection was more common in the elderly (≥65 years) compared to young adults (18-44 years) (OR: 1.8 (95% CI: 1.5, 2.2)), whereas Malassezia was more commonly detected in younger age groups (12.1-13.6%) than the elderly (5.6%). Candida was more frequently observed in females while dermatophytes and Malassezia were more frequently observed in males. Approximately one quarter of the submitted skin specimens tested positive for S. aureus (23.6% (SD: 3.4)), of which 34.4% (SD: 9.8) exhibited concurrent detection of the mecA gene. An S. aureus detection was more frequently observed in males (OR: 1.5 (95% CI: 1.2, 1.9)) and in children (OR: 1.7 (95% CI: 1.2, 2.5)). Streptococcus pyogenes was rarely detected. Among specimens positive for dermatophytes, 12.0% (20/166) showed co-detection of S. aureus and mecA, which is in contrast to 6.8% (70/1023) detected in samples without a fungal co-detection and 6.2% (8/130) in samples positive for Malassezia. Conclusions: PCR testing, when available, can be valuable as a part of routine care for diagnosing patients with clinically suspected skin infections. Further studies are warranted to survey the prevalence of resistant S. aureus isolates in dermatology outpatients, in particular with regard to the association with dermatophyte infections.

Multiplex Digital PCR-Based Development and discussion of the Detection of Genetic Association Between Staphylococcus aureus and mecA

Methicillin-resistant Staphylococcus aureus (MRSA) is a predominant nosocomial infection-causing bacteria. The aim of this study was to develop a novel single-bacteria multiplex digital PCR assays (SMD-PCR), which is capable of simultaneously detecting and discriminating Methicillin-sensitive Staphylococcus aureus (MSSA) and MRSA. This protocol employed TaqMan probes to detect SAOUHSC_00106 and mecA genes, with the latter being linked to methicillin resistance. A total of 72 samples from various specimen types were evaluated. The accuracy rates for the sputum samples, pus samples, swab samples, ear secretion samples, and catheter samples were 94.44%, 100%, 92%, 100%, and 100%, respectively. Our results showed that the clinical practicability of SMD-PCR has applicability to the rapid detection of MRSA without DNA extraction or bacterial culture, and can be utilized for the rapid detection of Staphylococcus aureus and the timely identification of MRSA in clinical samples, thereby providing an advanced platform for the rapid diagnosis of clinical MRSA infection.

Synergistic Potential of α-Melanocyte Stimulating Hormone Based Analogues with Conventional Antibiotic against Planktonic, Biofilm-Embedded, and Systemic Infection Model of MRSA

The repotentiation of the existing antibiotics by exploiting the combinatorial potential of antimicrobial peptides (AMPs) with them is a promising approach to address the challenges of slow antibiotic development and rising antimicrobial resistance. In the current study, we explored the ability of lead second generation Ana-peptides viz. Ana-9 and Ana-10, derived from Alpha-Melanocyte Stimulating Hormone (α-MSH), to act synergistically with different classes of conventional antibiotics against methicillin-resistant Staphylococcus aureus (MRSA). The peptides exhibited prominent synergy with β-lactam antibiotics, namely, oxacillin, ampicillin, and cephalothin, against planktonic MRSA. Furthermore, the lead combination of Ana-9/Ana-10 with oxacillin provided synergistic activity against clinical MRSA isolates. Though the treatment of MRSA is complicated by biofilms, the lead combinations successfully inhibited biofilm formation and also demonstrated biofilm disruption potential. Encouragingly, the peptides alone and in combination were able to elicit in vivo anti-MRSA activity and reduce the bacterial load in the liver and kidney of immune-compromised mice. Importantly, the presence of Ana-peptides at sub-MIC doses slowed the resistance development against oxacillin in MRSA cells. Thus, this study highlights the synergistic activity of Ana-peptides with oxacillin advocating for the potential of Ana-peptides as an alternative therapeutic and could pave the way for the reintroduction of less potent conventional antibiotics into clinical use against MRSA infections.

Genetic Diversity, Antibiotic Resistance, and Virulence Gene Features of Methicillin-Resistant Staphylococcus aureus Epidemics in Guiyang, Southwest China

Purpose

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common pathogens of community- and hospital-acquired infections, and its prevalence is increasing globally. Guiyang is the capital city of Guizhou Province, Southwest China; as the transport and tourism centre of Southwest China, Guizhou Province is bordered by Yunnan, Sichuan, Chongqing, and Guangxi Provinces. Although MRSA prevalence is increasing, little is known about its aspects in the area. The purpose of this study was to analyse MRSA molecular characteristics, antimicrobial resistance, and virulence genes in Guiyang.

Methods

In total, 209 MRSA isolates from four hospitals (2019-2020) were collected and analysed by antimicrobial susceptibility testing and molecular classification by the MLST, spa, and SCCmec typing methods. Isolate antibiotic resistance rates were detected by a drug susceptibility assays. PCR amplification was used to detect the virulence gene-carrying status.

Results

Twenty-four STs, including 4 new STs (ST7346, ST7347, ST7348, and ST7247) and 3 new allelic mutations, were identified based on MLST. The major prevalent ST type and clone complex were ST59 (49.8%) and CC59 (62.7%), respectively. Spa type t437 (42.1%) and SCCmec IV (55.5%) were identified by spa and SCCmec typing methods as the most important types. Drug sensitivity data showed that the multidrug resistance rate was 79.0%. There were significant differences in multidrug resistance rates and virulence gene-carrying rates for seb, hla, hlb, cna and bap between ST59 and non-ST59 types.

Conclusion

ST59-SCCmecIV-t437 is a major epidemic clone in Guiyang that should be monitored by local medical and health institutions. The situation differs from other adjacent or middle provinces of China, which may be due to the special geographical location of the region and the trend in antibiotic use or lifestyle. This study provides empirical evidence for local medical and health departments to prevent and control the spread of MRSA.

β-Lactams against the Fortress of the Gram-Positive Staphylococcus aureus Bacterium

The biological diversity of the unicellular bacteria-whether assessed by shape, food, metabolism, or ecological niche-surely rivals (if not exceeds) that of the multicellular eukaryotes. The relationship between bacteria whose ecological niche is the eukaryote, and the eukaryote, is often symbiosis or stasis. Some bacteria, however, seek advantage in this relationship. One of the most successful-to the disadvantage of the eukaryote-is the small (less than 1 μm diameter) and nearly spherical Staphylococcus aureus bacterium. For decades, successful clinical control of its infection has been accomplished using β-lactam antibiotics such as the penicillins and the cephalosporins. Over these same decades S. aureus has perfected resistance mechanisms against these antibiotics, which are then countered by new generations of β-lactam structure. This review addresses the current breadth of biochemical and microbiological efforts to preserve the future of the β-lactam antibiotics through a better understanding of how S. aureus protects the enzyme targets of the β-lactams, the penicillin-binding proteins. The penicillin-binding proteins are essential enzyme catalysts for the biosynthesis of the cell wall, and understanding how this cell wall is integrated into the protective cell envelope of the bacterium may identify new antibacterials and new adjuvants that preserve the efficacy of the β-lactams.

Epidemiological characteristics of methicillin-resistant Staphylococcus aureus isolates from bloodstream cultures at University Hospital in the Czech Republic

The aim of this study was to trace the dynamic changes of methicillin-resistant Staphylococcus aureus (MRSA) lineages in the local hospital in both the national and international context. We describe genotypic and phenotypic characterization of 62 non-duplicate MRSA isolates collected during 2010-2016 at University Hospital in Hradec Kralove, Czech Republic. The isolates were characterized by multilocus sequence typing (MLST), spa typing, and staphylococcal cassette chromosome mec typing (SCCmec typing). Eight different genotypes were described; ST225-t003-II (32/62, 52%), ST5-t002-II (13/62, 22%), and ST225-t014-II (12/62, 21%) were constantly detected over the 7-year follow-up period. The genotypes ST225-t151-II, ST225-t1282-II, ST225-t1623-II, ST78-t2832-II, and ST225-t8799-II occurred only once in the period reported. The majority of the strains, represented by ST225, belonged to clonal complex 5 (CC5).

Phage-Mediated Molecular Detection (PMMD): A Novel Rapid Method for Phage-Specific Bacterial Detection

Bacterial infections pose a challenge to human health and burden the health care system, especially with the spread of antibiotic-resistant populations. To provide effective treatment and improved prognosis, effective diagnostic methods are of great importance. Here we present phage-mediated molecular detection (PMMD) as a novel molecular method for the detection and assessment of bacterial antibiotic resistance. This technique consists of a brief incubation, of approximately ten minutes, of the biological sample with a natural bacteriophage (phage) targeting the bacteria of interest. This is followed by total RNA extraction and RT-PCR. We applied this approach to Staphylococcus aureus (SA), a major causative agent of human bacterial infections. PMMD demonstrated a high sensitivity, rapid implementation, and specificity dependent on the phage host range. Moreover, due to the dependence of the signal on the physiological state of the bacteria, PMMD can discriminate methicillin-sensitive from methicillin-resistant SA (MSSA vs. MRSA). Finally, we extended this method to the detection and antibiotic sensitivity determination of other bacteria by proving PMMD efficacy for Bacillus anthracis.