Prevalence and Therapies of Antibiotic-Resistance in Staphylococcus aureus

The Short Lipopeptides (C10)2-KKKK-NH2 and (C12)2-KKKK-NH2 Protect HaCaT Keratinocytes from Bacterial Damage Caused by Staphylococcus aureus Infection in a Co-Culture Model

The search for new antimicrobial strategies is of major importance since there is a growing resistance of both bacteria and fungi to existing antimicrobials. Lipopeptides are promising and potent antimicrobial compounds. For translation into clinically useful molecules, effectiveness of peptide treatment against human infections must be proved in complex in vitro wound models. The aim of this study was to examine if the synthesized short lipopeptides (C₁₀)₂-KKKK-NH₂ and (C₁₂)₂-KKKK-NH₂ can protect HaCaT keratinocytes from bacterial damage caused by Staphylococcus aureus infection in a coculture model. After 1 h, 24 h, and 48 h incubation, cellular ATP level and release of the cytotoxicity marker LDH as well as the proinflammatory cytokines interleukin-6 and interleukin-1α were measured. Infection of the keratinocytes resulted in strong bacterial damage of HaCaT cells along with low cellular ATP levels and high release of LDH, IL-6, and IL-1α after 24 h and 48 h. Incubation of the infected human keratinocytes with (C₁₀)₂-KKKK-NH₂ and (C₁₂)₂-KKKK-NH₂ resulted in protection of the keratinocytes from bacterial damage caused by Staphylococcus aureus infection with ATP, LDH, IL-6, and IL-1α levels comparable to the untreated control. Hence, both synthesized lipopeptides are promising candidates with high therapeutic potential in dermatology for the treatment of topical infections.

(-)-Camphene-based derivatives as potential antibacterial agents against Staphylococcus aureus and Enterococcus spp

Aim: To evaluate the activity of (-)-camphene-based thiosemicarbazide (TSC) and 4-hydroxy-thiosemicarbazone (4-OH-TSZ), alone and in combination against Gram-positive. Material & methods: MIC were determined for Staphylococcus aureus, Enterococcus spp. reference strains and clinical isolates. Drug combination, time-kill and cytotoxicity assays were also performed. Results: TSC and 4-OH-TSZ demonstrated potent inhibitory activity against S. aureus and Enterococcus spp., including multidrug-resistant isolates (MIC ranging from 1.9 to 31.2 μg/ml), and were bactericidal for the reference strains of both Gram-positive tested. The derivatives proved to be selective for the bacteria and synergistic with oxacillin and vancomycin. Conclusion: (-)-Camphene-based derivatives can represent promising drug candidates against critical pathogens, such as S. aureus and Enterococcus spp., including MRSA and vancomycin resistance Enterococcus spp. isolates.

Pathogenic Potential and Antimicrobial Resistance Profile of Staphylococcus aureus in Milk and Beef from the Northwest and Southwest Regions of Cameroon

Staphylococcus aureus is a major foodborne pathogen and commensal of the skin and mucous membranes of animals and humans. Its virulence relies on the production of a variety of toxins resistant to denaturing conditions. Increasing reports of S. aureus food poisoning and contamination of foods of animal origin elsewhere necessitates the investigation of these foods in Cameroon, to implement safety measures. This cross-sectional study evaluated S. aureus contamination in milk and beef in the Northwest and Southwest Regions of Cameroon, where cow milk is usually not pasteurized before consumption, and beef is the main source of protein. The distribution of antibiotic-resistant isolates and those with enterotoxin-producing potential was also investigated to provide data of public health and food safety benefit. S. aureus was isolated from 39 raw milk and 250 beef samples by standard methods. Confirmation of isolates was by PCR to detect the nuc gene. S. aureus was investigated for classical staphylococcal enterotoxin (SE) genes (sea, seb, sec, sed, and see) by PCR. Their susceptibility to 9 antibiotics was tested by the disk diffusion method. The chi-square test was used to compare the contamination of samples, antibiotic resistance, and the distribution of SE genes. S. aureus was isolated from 11.1% of samples. Contamination was higher in milk (48%) than in beef (5.2%) (P < 0.001). The sea was the most frequently (90%) harboured gene. A large proportion of isolates (88%) harboured more than one virulence gene. Isolates were generally resistant to erythromycin (82%), vancomycin (80%), tetracycline (76%), and oxacillin (74%). Multidrug resistance (MDR) was common (92%). Milk and beef samples in study area were contaminated with MDR enterotoxigenic S. aureus strains and may constitute a potential hazard to consumers. Thus, the need for implementation of proper hygienic measures when handling these products and pasteurization of milk cannot be overemphasized.

Methicillin-resistant Staphylococcus aureus: epidemiology and antimicrobial susceptibility experiences from the University Hospital 'Luigi Vanvitelli' of Naples

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the important pathogens worldwide showing resistance to several widely used antibiotics. This has made the treatment of MRSA infections harder, especially due to their prevalence in the hospital setting. We evaluated the antibiotic susceptibility patterns of healthcare-associated MRSA infections with a focus on Vancomycin Intermediate S. Aureus (VISA) and macrolide-licosamide-streptogramin B (MLS_B) phenotypes. A total of 417 Staphylococcus aureus (S. aureus) cases were isolated between January 2017 and December 2018, through several clinical specimens collected from the University Hospital 'Luigi Vanvitelli' of Naples. We identified bacterial strains using Matrix-Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) and antimicrobial susceptibility using Phoenix BD (Becton Dickinson, NJ, USA). Out of the total 417 S. aureus cases, 140 were MRSA (33.6%) and of these, 50% were soft tissue infections. All MRSA and Methicillin sensible S.aureus MSSA isolates were susceptible to linezolid and daptomycin. Two MRSA cases exhibited intermediate resistance to vancomycin and were of constitutive MLS_B phenotype. Among the MRSA strains, 11.4% were constitutive and 43.6% were inducible MLS_B phenotypes and 8.6% were macrolide-streptogramin B phenotype. This study characterized the epidemiological status, antibiotic resistance patterns, and current prevalent phenotypes of healthcare-associated MRSA. This knowledge can aid clinicians in improving the antimicrobial stewardship program by adapting appropriate guidelines for the proper use of MRSA antibacterial agents.

Interaction of the surface bound antimicrobial peptides melimine and Mel4 with Staphylococcus aureus

Melimine and Mel4 are cationic antimicrobial peptides which can resist biofilm development once bound to biomaterials. The aim of the current study was to determine the mode of action of bound melimine and Mel4 against S. aureus. The peptides were covalently attached to glass using an azidobenzoic acid linker. The amount of attached peptides was confirmed by XPS and amino acid analysis and their covalent attachment by SDS extraction. The release of autolysins after interaction of S. aureus with immobilized peptides was determined in cell free supernatants. The interaction of immobilized peptides with lipoteichoic acid was confirmed by ELISA. Membrane damage by surface bound peptides was assessed using DiSC(3)-5 (membrane potential sensitive), Syto-9 (membrane permeable) and PI (membrane impermeable) dyes with fluorescence microscopy. Release of ATP and nucleic acids (DNA/RNA) was measured in the surrounding fluid. Attachment of the peptides resulted in increased N% for melimine (5.4 ± 1.8%) and for Mel4 (4.8 ± 1.8%). The concentrations of immobilised amino acids were 0.297 nmole for melimine and 0.358 nmole for Mel4. SDS extraction released < 15% of peptides from the glass. The immobilized peptides bound ≥ 4 times more LTA than control surfaces. More autolysins (8 ± 2%; p = 0.026) were released from Mel4 than melimine or control surfaces. Membrane depolarization occurred at 15 min and was associated with a reduction in bacterial viability ≥ 37% for both peptides (p < 0.001). Disruption of the membrane potential resulted in loss of ATP from melimine (0.9 ± 0.4 nM) or Mel4 (0.6 ± 0.3 nM) coated surfaces compared to control (p < 0.001). Melimine coatings yielded 27 ± 11% (p = 0.026) and Mel4 gave 17 ± 12% (p = 0.150) PI stained cells after 4 h. DNA/RNA was released only by melimine coatings (2.1 ± 0.1 times; p = 0.011) compared to process control at 6 h. Both bound peptides resulted in the release of ATP, but only melimine released DNA/RNA while Mel4-coating resulted in the release of autolysins. Since the mode of action of melimine and Mel4 relate to the cell surface, they have potential for the development of infection-resistant implants.

Naturally-Occurring Alkaloids of Plant Origin as Potential Antimicrobials against Antibiotic-Resistant Infections

Antibiotic resistance is now considered a worldwide problem that puts public health at risk. The onset of bacterial strains resistant to conventional antibiotics and the scarcity of new drugs have prompted scientific research to re-evaluate natural products as molecules with high biological and chemical potential. A class of natural compounds of significant importance is represented by alkaloids derived from higher plants. In this review, we have collected data obtained from various research groups on the antimicrobial activities of these alkaloids against conventional antibiotic-resistant strains. In addition, the structure–function relationship was described and commented on, highlighting the high potential of alkaloids as antimicrobials.

Diclofenac mitigates virulence of multidrug-resistant Staphylococcus aureus

Staphylococcus aureus is an opportunistic pathogen that has the ability to cause a wide range of diseases including superficial infection and severe invasive life threatening infections. The pathogenicity of S. aureus is mediated by a group of virulence factors that mediate the colonization and penetration. The antibiotic resistance of S. aureus has evolved due to the abuse of antibiotics rendering the cure of infection very difficult especially with the shortage in new antibiotic production. To combat this shortage, repurposing of FDA-approved drugs against the virulence factors is a new strategy. The analgesic drug Diclofenac was found to have anti-virulence activity against Pseudomonas aeruginosa and Proteus mirabilis. This study aimed to demonstrate the anti-virulence effect of diclofenac against clinical MRSA isolates phenotypically and genotypically using qRT-PCR. In this study, diclofenac showed significant reduction in biofilm formation when compared to controls, the inhibition ranged between 22.67% and 70%. Also, remarkable inhibition of hemolysin activity was found (5.4-66.34%). Additionally, diclofenac has inhibitory activity against the staphyloxanthin production (8-57.2%). The results were confirmed by qRT-PCR that showed significant down-regulation of tested virulence genes. The down-regulation ranged from 43 to 64.05% for SarA, 36.85-64.75% for AgrA, 50-63.2% for hla, 38.55-60.35% for FnbA, 46.75-61.05% for IcaA, 27.55-64% for SigB and 51.05-72.8% for CrtM. In conclusion, diclofenac can be used in combination with antibiotics as anti-virulence agent against MDR-MRSA which will enhance the ability of immune system to eradicate infection.

Systematic Review and Meta-Analysis of the Occurrence of ESKAPE Bacteria Group in Dogs, and the Related Zoonotic Risk in Animal-Assisted Therapy, and in Animal-Assisted Activity in the Health Context

Animal-assisted interventions are widely implemented in different contexts worldwide. Particularly, animal-assisted therapies and animal-assisted activities are often implemented in hospitals, rehabilitation centers, and other health facilities. These interventions bring several benefits to patients but can also expose them to the risk of infection with potentially zoonotic agents. The dog is the main animal species involved used in these interventions. Therefore, we aimed at collecting data regarding the occurrence of the pathogens ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp.) in dogs, in order to draft guidelines concerning the possible monitoring of dogs involved in animal-assisted therapies and animal-assisted activities in healthcare facilities. We performed a literature search using the PRISMA guidelines to examine three databases: PubMed, Web of Science, and Scopus. Out of 2604 records found, 52 papers were identified as eligible for inclusion in the review/meta-analysis. Sixteen papers reported data on E. faecium; 16 on S. aureus; nine on K. pneumoniae; four on A. baumannii; eight on P. aeruginosa; and six on Enterobacter spp. This work will contribute to increased awareness to the potential zoonotic risks posed by the involvement of dogs in animal-assisted therapies, and animal-assisted activities in healthcare facilities.