Cell surface hydrophobicity and adherence to extra-cellular matrix proteins in two collections of methicillin-resistant Staphylococcus aureus

Multi-Faceted Antimicrobial Efficacy of a Quinoline-Derived Bidentate Copper(II) Ligand Complex and Its Hydrogel Encapsulated Formulation in Methicillin-Resistant Staphylococcus aureus Inhibition and Wound Management

The emergence of antimicrobial resistance, exemplified by methicillin-resistant Staphylococcus aureus (MRSA), poses a grave threat to public health globally. Over time, MRSA has evolved resistance to multiple antibiotics, challenging conventional treatment strategies. The relentless adaptability of MRSA underscores the urgent need for innovative and targeted antimicrobial approaches to combat this resilient pathogen. Ancient knowledge and practices, along with scientific evidence, have established that metallic copper, and its organic coordination complexes can act as potential antibacterial substances. In search of a smart and effective antimicrobial against MRSA, we designed, synthesized, and characterized a bidentate copper(II) ligand complex (SG-Cu) utilizing a comprehensive array of analytical techniques, including ESI-MS, elemental analysis, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy, and others. Antibacterial efficacy and mechanism of action of the complex were assessed through bacterial growth analyses, bacterial membrane perturbation assays, ROS elicitation assays, and field emission scanning electron microscopy. SG-Cu was found to maintain robust biocompatibility against the mammalian cell lines HEK-293, WI-38, and NIH/3T3. Remarkably, SG-Cu demonstrated significant biofilm disruptive tendency evidenced by the retardation of sliding motility, reduction in slime production, reduction in biofilm viability, and enhanced biofilm eradication, both in vitro and in urinary catheters. In vivo studies on murine excisional wounds, with SG-Cu impregnated in a palmitic acid conjugated NAVSIQ hexapeptide (PA-NV) hydrogel, revealed the sustained release of SG-Cu from the gel matrix, facilitating accelerated wound healing and effective wound disinfection. This multifaceted investigation highlights the potential of SG-Cu as a versatile option for combating MRSA infections and promoting wound healing, solidifying its claim to be developed into a viable therapeutic.

Synergistic Augmentation of Beta-Lactams: Exploring Quinoline-Derived Amphipathic Small Molecules as Antimicrobial Potentiators against Methicillin-Resistant Staphylococcus aureus

The escalation of bacterial resistance against existing therapeutic antimicrobials has reached a critical peak, leading to the rapid emergence of multidrug-resistant strains. Stringent pathways in novel drug discovery hinder our progress in this survival race. A promising approach to combat emerging antibiotic resistance involves enhancing conventional ineffective antimicrobials using low-toxicity small molecule adjuvants. Recent research interest lies in weak membrane-perturbing agents with unique cyclic hydrophobic components, addressing a significant gap in antimicrobial drug exploration. Our study demonstrates that quinoline-based amphipathic small molecules, SG-B-52 and SG-B-22, significantly reduce MICs of selected beta-lactam antibiotics (ampicillin and amoxicillin) against lethal methicillin-resistant Staphylococcus aureus (MRSA). Mechanistically, membrane perturbation, depolarization, and ROS generation drive cellular lysis and death. These molecules display minimal in vitro and in vivo toxicity, showcased through hemolysis assays, cell cytotoxicity analysis, and studies on albino Wistar rats. SG-B-52 exhibits impressive biofilm-clearing abilities against MRSA biofilms, proposing a strategy to enhance beta-lactam antibiosis and encouraging the development of potent antimicrobial potentiators.

Carvacrol Essential Oil: A Natural Antibiotic against Zoonotic Multidrug-Resistant Staphylococcus Species Isolated from Diseased Livestock and Humans

Staphylococcus species cause diseases in animals and humans. The prevalence and antimicrobial profiles of Staphylococcus spp. in animals and human samples in the Minya Governorate, Egypt, were determined, and resistance- and virulence-associated genes were observed in multidrug-resistant (MDR) isolates. Moreover, the antibacterial effect of carvacrol essential oil (EO) on the MDR isolates was studied. A total of 216 samples were aseptically collected from subclinically mastitic cow's milk (n = 100), sheep abscesses (n = 25) and humans (n = 91). Out of 216 samples, a total of 154 single Staphylococcus species (71.3%) were isolated. The most frequent bacterial isolates were S. aureus (43%), followed by S. schleiferi (25%), S. intermedius (12%), S. xylosus (12%), S. haemolyticus (4.5%), S. epidermidis (2%) and S. aurecularis (1%). Haemolytic activity and biofilm production were detected in 77 and 47% of isolates, respectively. Antimicrobial susceptibility testing showed a high degree of resistance to the most commonly used antimicrobials in human and veterinary practices. The mecA, vanA, vanC1 and ermC resistance genes were detected in 93, 42, 83 and 13% of isolates, respectively. Moreover, hla, icaA and icaD virulence genes were detected in 50, 75 and 78% of isolates, respectively. Carvacrol effectively inhibited the growth of all tested isolates at concentrations of 0.1, 0.05 and 0.04% while a concentration of 0.03% inhibited 75% of isolates. Interestingly, some phenotypic changes were observed upon treatment with a carvacrol oil concentration of 0.03%. All the treated MDR Staphylococcus isolates changed from multidrug resistant to either susceptible or intermediately susceptible to 2-3 antimicrobials more than parental bacterial isolates. Real-time PCR was applied for the detection of the differential expression of mecA and vanC1 genes before and after treatment with carvacrol which revealed a mild reduction in both genes' expression after treatment. Staphylococcus spp. Containing MDR genes are more likely to spread between humans and animals. From these results, carvacrol EO is a promising natural alternative to conventional antimicrobials for pathogens impacting human health and agriculture due to its potential antimicrobial effect on MDR pathogens; even in sub-lethal doses, carvacrol EO can affect their phenotypic properties and genes' expression.

Bacteria Display Differential Growth and Adhesion Characteristics on Human Hair Shafts

Apart from the skin surface, hair represents a significant tissue component with a capacity of bacterial interactions. New information can be obtained about hair function through the characterization of bacterial adherence, colonization, and responses to hair shafts per se. In this proof-of-principle study, we examine the growth kinetics of Gram-positive Staphylococcus aureus and Staphylococcus epidermidis, and Gram-negative Pseudomonas aeruginosa and Escherichia coli in the presence of human hair shafts. We explore the ability of these bacteria to adhere to and colonize hair shaft surfaces, as well as the resulting impact on the hair's surface morphology. We show that hair shafts inhibit the growth of Gram-positive S. aureus and S. epidermidis, while the growth kinetics of P. aeruginosa and E. coli remain unaffected. Scanning electron microscope analysis and steeping studies show that P. aeruginosa and E. coli to adhere to and colonize on human hair shafts without significantly affecting the hair shaft's surface morphology. P. aeruginosa produced a substantial amount of biofilm on the hair shaft surfaces, while E. coli specifically inhabited the edges of the cuticle scales. Taken together, our results demonstrate differences in bacterial responses to human hair shafts, which may provide novel insights into hair and scalp health.

Factors responsible for subclinical mastitis in cows caused by Staphylococcus chromogenes and its susceptibility to antibiotics based on bap, fnbA, eno, mecA, tetK, and ermA genes

The aim of this study was to recognize selected factors of virulence determining the adhesion of Staphylococcus chromogenes to cows' udder tissues in subclinical mastitis and to evaluate the susceptibility of this pathogen to antibiotics. The subjects of the study were 38 isolates of Staph. chromogenes from 335 samples of milk from cows with subclinical coagulase-negative staphylococci mastitis. Somatic cell count ranged between 216,000 and 568,000/mL of milk (average 356,000/mL of milk). We confirmed the ability to produce slime in 24 isolates (63.2%), and the ability to produce protease in 29 isolates (76.3%). In each slime-producing isolate, the bap gene was not found, and the fnbA and eno genes were not detected. In vitro tests showed that ceftiofur had the highest effectiveness against Staph. chromogenes (89.5% of susceptible isolates). Minimum inhibitory concentrations ranged from 0.06 to 2µg/mL for susceptible isolates. The minimum concentrations required to inhibit growth of 90 and 50% of the isolates for ceftiofur were at or below the cutoffs recommended by the Clinical and Laboratory Standards Institute (2 and 0.06µg/mL, respectively). A significant percentage of the isolates were susceptible to other β-lactam antibiotics: amoxicillin with clavulanic acid (84.2%) and ampicillin (81.6%). The lowest effectiveness among β-lactams was for penicillin (73.7% of susceptible isolates), and the minimum inhibitory concentration for penicillin ranged from <0.06 to 8µg/mL. None of the examined isolates had the mecA gene, but β-lactamase was detected in 4 isolates (10.5%). Erythromycin and oxytetracycline exhibited the lowest activity against Staph. chromogenes (71.1 and 63.2% of susceptible isolates, respectively). The genes tetK (6 isolates) and ermA (1 isolate) were also detected.

The interface between antibiotic resistance and virulence in Staphylococcus aureus and its impact upon clinical outcomes

The ability of Staphylococcus aureus to rapidly acquire antibiotic resistance in the face of antimicrobial challenge has enabled it to remain an ongoing, significant human pathogen. Mechanisms behind the evolution of resistance in S. aureus are well documented, but the effects of these phenotypes upon virulence are less clear. By exploring available clinical and experimental data, we have shown that a number of the major steps in the evolution of antibacterial resistance in S. aureus have been accompanied by alterations in virulence. This review also highlights that further experimentation is required to fully elucidate the mechanisms involved in the interface between virulence and antibiotic resistance, with the intention of identifying novel preventative or therapeutic strategies for this important human pathogen.

Melanin is an essential component for the integrity of the cell wall of Aspergillus fumigatus conidia

Background

Aspergillus fumigatus is the most common agent of invasive aspergillosis, a feared complication in severely immunocompromised patients. Despite the recent commercialisation of new antifungal drugs, the prognosis for this infection remains uncertain. Thus, there is a real need to discover new targets for therapy. Particular attention has been paid to the biochemical composition and organisation of the fungal cell wall, because it mediates the host-fungus interplay. Conidia, which are responsible for infections, have melanin as one of the cell wall components. Melanin has been established as an important virulence factor, protecting the fungus against the host's immune defences. We suggested that it might also have an indirect role in virulence, because it is required for correct assembly of the cell wall layers of the conidia.

Results

We used three A. fumigatus isolates which grew as white or brown powdery colonies, to demonstrate the role of melanin. Firstly, sequencing the genes responsible for biosynthesis of melanin (ALB1, AYG1, ARP1, ARP2, ABR1 and ABR2) showed point mutations (missense mutation, deletion or insertion) in the ALB1 gene for pigmentless isolates or in ARP2 for the brownish isolate. The isolates were then shown by scanning electron microscopy to produce numerous, typical conidial heads, except that the conidia were smooth-walled, as previously observed for laboratory mutants with mutations in the PKSP/ALB1 gene. Flow cytometry showed an increase in the fibronectin binding capacity of conidia from mutant isolates, together with a marked decrease in the binding of laminin to the conidial surface. A marked decrease in the electronegative charge of the conidia and cell surface hydrophobicity was also seen by microelectrophoresis and two-phase partitioning, respectively. Ultrastructural studies of mutant isolates detected considerable changes in the organisation of the conidial wall, with the loss of the outermost electron dense layer responsible for the ornamentations seen on the conidial surface in wild-type strains. Finally, analysis of the conidial surface of mutant isolates by atomic force microscopy demonstrated the absence of the outer cell wall rodlet layer which is composed of hydrophobins.

Conclusion

These results suggest that, in addition to a protective role against the host's immune defences, melanin is also a structural component of the conidial wall that is required for correct assembly of the cell wall layers and the expression at the conidial surface of adhesins and other virulence factors.

MRSA and the environment: implications for comprehensive control measures

Environmental contamination with methicillin-resistant Staphylococcus aureus (MRSA) is established soon after colonized or infected patients become resident. There are many studies that detail the mechanisms of spread and environmental survival of methicillin-susceptible Staphylococcus aureus (MSSA); this knowledge translates directly into the same findings for MRSA. The potential ubiquity of MRSA in a health-care setting poses challenges for decontamination. Whereas patients and medical staff are important sources for MRSA spread, the environmental burden may contribute significantly in various contexts. Effective control measures must therefore include consideration for MRSA in the environment.

Is MRSA more virulent than MSSA?

Numerous clinical studies have indicated, based on mortality rates, that methicillin-resistant Staphylococcus aureus (MRSA) strains are more virulent than methicillin-susceptible S. aureus (MSSA) strains. In contrast, quantitative laboratory examinations of the presence and magnitude of pathogenic mechanisms and virulence factors in strains of MRSA and MSSA have generated conflicting data. The most important reason for these conflicting results is probably the heterogeneic nature of the resistant population. A comparison of selected and congenic MRSA and MSSA sub-populations of the same strain is required to resolve this issue.

Firm adherence of Staphylococcus aureus and Staphylococcus epidermidis to human hair and effect of detergent treatment

Staphylococcus aureus and S. epidermidis are common pathogens in hospitals, and care should be taken not to disseminate these organisms among patients. We have focused on human hair as a source of bacterial contamination. We treated hair with culture solutions of S. aureus and S. epidermidis, and then performed scanning electron microscopy. Bacteria were detected on the surface of the cuticles of the hair, and the attached bacteria were not completely removed even by repeated washing with detergents. These results suggested that hair could be a source of bacterial contamination and indicated the importance of decontamination of hair.

Bacterial interference among nasal inhabitants: eradication of Staphylococcus aureus from nasal cavities by artificial implantation of Corynebacterium sp

To evaluate the role of normal flora in the nares in preventing Staphylococcus aureus colonization, we conducted a replacement study in vivo. Staphylococcus epidermidis (rate of colonization: 100%), various species of corynebacteria (52.5%) and S. aureus (25.%) were the major bacterial inhabitants in the nares of 156 healthy volunteers. The low incidence of S. aureus colonization in the carriers with corynebacteria (8.5%), compared to non-carriers (44. 5%) indicated the possibility of competition for survival between S. aureus and corynebacteria. To confirm this hypothesis, we artificially implanted a strain of Corynebacterium sp (API Coryne bioprofile; 5100304), denoted as Co304 into the nares of 17 S. aureus carriers. S. aureus was completely eradicated in 71% of carriers by up to 15 inoculations of Co304. However, similar doses of 0.9% NaCl or S. epidermidis into the nares of 10 volunteers did not eradicate S. aureus. No bacteriocin-like activity against S. aureus was detectable, even after mitomycin C stimulation of Co304. Thus Co304 interfered with S. aureus by a different mechanism to a bacteriocin-like activity.

[The association between human toxocariasis and pyogenic abscesses]

The association between hepatic abscesses and schistosomiasis mansoni was confirmed by clinical and experimental studies. Other parasites may cause systemic immunologic changes and local structural alterations in the affected organs that can facilitate the seeding of these areas by bacteria. Tropical pyomyositis, pyogenic liver and renal abscesses are frequent diseases in tropical areas. The visceral larva migrans syndrome is caused by the presence, in the human body, of larvae of worms that have other animals as their definitive host, most commonly being caused by Toxocara canis. The larvae migrate to various body organs leading to many inflammatory reactions in the form of granuloma and tissue necrosis. In this review we discuss the possible host-parasite-bacteria interactions that would favour the formation of abscesses in the organs involved by the larva of T. canis and present preliminary results of a clinical and experimental study undertaken during the last four years to define the role of this parasite in the pathogenesis of the abscesses.

Nasal carriage of Staphylococcus aureus: epidemiology, underlying mechanisms, and associated risks

Staphylococcus aureus has long been recognized as an important pathogen in human disease. Due to an increasing number of infections caused by methicillin-resistant S. aureus (MRSA) strains, therapy has become problematic. Therefore, prevention of staphylococcal infections has become more important. Carriage of S. aureus appears to play a key role in the epidemiology and pathogenesis of infection. The ecological niches of S. aureus are the anterior nares. In healthy subjects, over time, three patterns of carriage can be distinguished: about 20% of people are persistent carriers, 60% are intermittent carriers, and approximately 20% almost never carry S. aureus. The molecular basis of the carrier state remains to be elucidated. In patients who repeatedly puncture the skin (e.g., hemodialysis or continuous ambulatory peritoneal dialysis [CAPD] patients and intravenous drug addicts) and patients with human immunodeficiency virus (HIV) infection, increased carriage rates are found. Carriage has been identified as an important risk factor for infection in patients undergoing surgery, those on hemodialysis or CAPD, those with HIV infection and AIDS, those with intravascular devices, and those colonized with MRSA. Elimination of carriage has been found to reduce the infection rates in surgical patients and those on hemodialysis and CAPD. Elimination of carriage appears to be an attractive preventive strategy in patients at risk. Further studies are needed to optimize this strategy and to define the groups at risk.

Growth conditions influence expression of cell surface hydrophobicity of staphylococci and other wound infection pathogens

The initial adhesion of microbes to tissue and solid surfaces can be mediated by hydrophobic interaction. Expression of microbial cell surface hydrophobicity (CSH) is influenced by growth conditions, and often best expressed after growth under nutrient-poor conditions, or "starvation". In the present study, the CSH of 133 strains of Enterobacteriaceae, Staphylococcus aureus, coagulase-negative staphylococci, Enterococcus faecalis, group A streptococcus, Pseudomonas aeruginosa, Clostridium perfringens, Bacteroides fragilis, Peptococcus magnus, and of 8 Candida albicans strains was measured by the salt aggregation test after growth on hematin agar in a 5% CO2 atmosphere, or under anaerobiosis. Cells of all but 8 strains expressed pronounced or moderate CSH, i.e., they aggregated in 0.01-2 M ammonium sulfate. When the agar surface was covered by human serum (diluted 1:5) to mimic growth conditions in a wound, 94 strains expressed higher CSH, and 44 strains the same CSH as after growth without serum. The CSH of 12 strains of different species was measured after growth on blood, hematin and PDM agar, with or without serum, and in an aerobic or a 5% CO2 atmosphere. The highest CSH was expressed after growth in 5% CO2 with serum, and the lowest growth after on blood agar in aerobic atmosphere. Identical results were obtained with native and heat-inactivated (56 C, 20 min) serum. The reduced surface tension obtained in 5% CO2, as well as yet unidentified serum factors, promotes expression of CSH.