Mupirocin at Subinhibitory Concentrations Induces Biofilm Formation in Staphylococcus aureus

Sub-inhibitory concentrations of ceftriaxone induce morphological alterations and PIA-independent biofilm formation in Staphylococcus aureus

The exposure of bacteria to sub-inhibitory concentrations of antibiotics is of biological significance since it can occur in vivo under many circumstances, including low-dose treatment, poor adherence to a regimen, poor drug penetration, drug-drug interactions, and antibiotic resistance of the pathogen. In this study, we investigated the effects of subinhibitory concentrations of four antibiotics: ampicillin, ceftriaxone, gentamicin, and norfloxacin, which are commonly used in clinical settings and on cell morphology and biofilm formation in Staphylococcus aureus as one of the leading causes of nosocomial and biofilm-associated infections. Nine clinical S. aureus biofilm-producing isolates and two known biofilm-producing reference strains, S. aureus ATCC 29213 and S. aureus ATCC 6538, were used in this study. Sub-MICs of beta-lactam antibiotics (ampicillin and ceftriaxone) significantly induced biofilm formation in S. aureus ATCC 29213 and S. aureus ATCC 6538 and in six clinical isolates out of the nine selected isolates when compared with the antibiotic-free control group (P < 0.05), with an approximately 2- to 2.5-fold increase. Gentamicin and norfloxacin induced biofilms in S. aureus ATCC 29213 and S. aureus ATCC 6538, while gentamicin and norfloxacin induced biofilms only in three and two of the nine tested isolates, respectively (P < 0.05). The chemical nature of the biofilm matrix produced by half the MIC of ceftriaxone in the six isolates that showed increased biofilm was all non-polysaccharide in composition (PIA-independent). Gene expression of biofilm-encoding genes atl and sarA in biofilms of the two tested strains (S. aureus ATCC 6538) and clinical strain (S. aureus 16) showed a significant upregulation after exposure to half MIC of ceftriaxone. Additionally, the bacterial cell morphological changes in planktonic cells caused by half MIC of ceftriaxone were evaluated by scanning electron microscopy, which demonstrated a significant cell enlargement when compared with the antibiotic-free control (P < 0.05), and some deformed cells were also noticed. In S. aureus clinical isolates, sub-MICs of ampicillin, ceftriaxone, gentamicin, and norfloxacin may stimulate substantial production of biofilm, which could have important clinical significance and make infection treatment challenges. Further, in vivo research is needed to fully comprehend how sub-MIC of antibiotics can affect biofilm formation in clinical settings. Additionally, more research is required to reveal the clinical implications of the morphological alterations in S. aureus brought on by exposure to ceftriaxone at concentrations below its MIC.

RelQ-mediated alarmone signaling regulates growth, sporulation, and stress-induced biofilm formation in Clostridioides difficile

The bacterial stringent response (SR) is a conserved transcriptional reprogramming pathway mediated by the nucleotide signaling alarmones, (pp)pGpp. The SR has been implicated in antibiotic survival in Clostridioides difficile, a biofilm- and spore-forming pathogen that causes resilient, highly recurrent C. difficile infections. The role of the SR in other processes and the effectors by which it regulates C. difficile physiology are unknown. C. difficile RelQ is a clostridial alarmone synthetase. Deletion of relQ dysregulates C. difficile growth in unstressed conditions, affects susceptibility to antibiotic and oxidative stressors, and drastically reduces biofilm formation. While wild-type C. difficile displays increased biofilm formation in the presence of sub-lethal stress, the ΔrelQ strain cannot upregulate biofilm production in response to stress. Deletion of relQ slows spore accumulation in planktonic cultures but accelerates it in biofilms. This work establishes biofilm formation and sporulation as alarmone-mediated processes in C. difficile and reveals the importance of RelQ in stress-induced biofilm regulation.

Synergistic antibacterial effects of exopolysaccharides/nickel-nanoparticles composites against multidrug-resistant bacteria

The need for an alternative treatment to fight infectious diseases caused by antibiotic-resistant bacteria is increasing. A possible way to overcome bacterial resistance to antibiotics is by reintroducing commonly used antibiotics with a sensitizer capable of enhancing their antimicrobial effect in resistant bacteria. Here, we use a composite composed of exopolysaccharide capped-NiO NPs, with antimicrobial effects against antibiotic-resistant Gram-positive and Gram-negative bacteria. It potentiated the antimicrobial effects of four different antibiotics (ampicillin, kanamycin, chloramphenicol, and ciprofloxacin) at lower concentrations than their minimal inhibitory concentrations. We observed that the Ni-composite synergistically enhanced, fourfold, the antibacterial effect of kanamycin and chloramphenicol against multidrug-resistant Staphylococcus aureus and Pseudomonas aeruginosa, as well as ampicillin against multidrug-resistant Staphylococcus aureus, and ciprofloxacin against multidrug-resistant Pseudomonas aeruginosa by eightfold. We also found that Ni-composite could not inhibit biofilm synthesis on the tested bacterial strains. Our results demonstrated the possibility of using metal nanoparticles, like NiO, as a sensitizer to overcome bacterial antibiotic resistance.

Antibacterial and Disinfecting Effects of Standardised Tea Extracts on More than 100 Clinical Isolates of Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) infections are still a major problem in hospitals. The excellent safety profile, accessibility and anti-infective activity of tea extracts make them promising agents for the treatment of infected wounds. To investigate the possibility of sterilising MRSA-infected surfaces, including skin with tea extracts, we determined the MICs for different extracts from green and black tea (Camellia sinensis), including epigallocatechin gallate (EGCG), on a large number of clinical isolates of MRSA, selected to represent a high genetic diversity. The extracts were prepared to achieve the maximal extraction of EGCG from tea and were used as stable lyophilisate with a defined EGCG content. All extracts showed a complete inhibition of cell growth at a concentration of approx. 80 µg/mL of EGCG after a contact time of 24 h. Time-kill plots were recorded for the extract with the highest amount of EGCG. The reduction factor (RF) was 5 after a contact time of 240 min. EGCG and tea extracts showed an RF of 2 in methicillin-sensitive S. aureus. Extracts from green and black tea showed lower MICs than an aqueous solution with the same concentration of pure EGCG. To the best of our knowledge, we are the first to show a reduction of 99.999% of clinically isolated MRSA by green tea extract within 4 h.

Effective decolonization strategy for mupirocin-resistant Staphylococcus aureus by TPGS-modified mupirocin-silver complex

The widespread utilization of mupirocin to treat methicillin-resistant Staphylococcus aureus (MRSA)-caused infectious diseases has led to the emergence of mupirocin-resistant Staphylococcus aureus (MuRSA), posing a serious global medical threat. In order to counteract MuRSA, we develop a d-α-tocopherol polyethylene glycol 1000 succinate (TPGS) modified mupirocin and silver complex (TPGS/Mup-Ag) to combat MuRSA. The surfactivity of TPGS endows Mup-Ag with a homogeneous and small particle size (∼16 ​nm), which significantly enhances bacterial internalization. Silver ions are released from the mupirocin-Ag complex (Mup-Ag) to exert a synergistic antibacterial activity with mupirocin. Results manifest that our strategy reduces the concentration of mupirocin that induces 50% bacterial death from about 1000 ​μmol/mL to about 16 ​μmol/mL. In vitro bacterial infection model suggests that TPGS/Mup-Ag can not only eliminate both intracellular and inhibit bacterial adhesion, but also living cells are not affected. Results of in vivo experiments demonstrate that TPGS/Mup-Ag can effectively inhibit the progression of skin infection and accelerate wound healing, as well as alleviate systemic inflammation in both the subcutaneous infection model and the wound infection model. Furthermore, this study may contribute to the development of therapeutic agents for antibiotic-resistant bacteria and offer ideas for silver-based bactericides.

Distribution of Biocide Resistance Genes and Association with Clonal Complex Genotypes in Staphylococcus aureus Isolated from School-Age Children in Guangzhou

Purpose

Chlorhexidine and mupirocin are often prescribed to children in affected communities to prevent colonization and transmission of Staphylococcus aureus, but this has led to an increasing rate of biocide resistance. In this study, we aimed to determine the distribution of biocide resistance genes among S. aureus isolates from school-age children in Guangzhou, investigate chlorhexidine gluconate and mupirocin susceptibility and clonal complex (CC) genotypes in strains carrying biocide-resistance genes, and further explore the role of biofilms in this resistance.

Patients and Methods

Antibiotic resistance and multilocus sequence genotyping were performed on 722 S. aureus isolates from previous study. The distribution of nine biocide genes (qacA/B, mupA, mepA, sepA, norA, lmrS, smr, mupB, qacG) was determined by PCR. Isolates carrying qacA/B or mupA genes were further tested for susceptibility to chlorhexidine gluconate (CHG) and mupirocin and biofilm formation abilities.

Results

The most prevalent of the nine biocide resistance genes were mepA (95.57%), followed by norA (78.81%), lmrS (77.01%), and sepA (58.17%). The qacG gene was not detected. Distribution of sepA was significantly decreased in CC30 and CC45 genotypes, and presence of sepA was associated with resistance to antibiotics such as CLI, ERY, TCY, SXT, CIP, and LVX. In addition, 64 (94.1%, n=68) qacA/B+ isolates showed CHG resistance, 12 (100.0%, n=12) mupA+ isolates were mupirocin resistant, and 4 (80%, n=5) and 5 (100%, n=5) qacA/B+mupA+ isolates were CHG and mupirocin resistant, respectively. Of these 85 isolates, 98.8% (n=84) had different degrees of biofilm-forming abilities, which were positively associated with CHG and mupirocin resistance.

Conclusion

The distribution of biocide resistance genes was associated with special CCs. The qacA/B and mupA genes are highly associated with resistance to CHG and mupirocin, and biofilm formation was found to contribute to this biocide resistance.

Strong Biofilm Formation and Low Cloxacillin Susceptibility in Biofilm-Growing CC398 Staphylococcus aureus Responsible for Bacteremia in French Intensive Care Units, 2021

A prospective 3-month study carried out in 267 ICUs revealed an S. aureus nosocomial bacteremia in one admitted patient out of 110 in adult and pediatric sectors, and in one out of 230 newborns; 242 S. aureus bacteremias occurred during the study, including 7.9% MRSA-bacteremias. In one ICU out of ten, the molecular characteristics, antimicrobial susceptibility profiles and biofilm production of the strains responsible for S. aureus bacteremia were studied. Of the 53 strains studied, 9.4% were MRSA and 52.8% were resistant to erythromycin. MLST showed the predominance of CC398 (37.7% of the strains) followed by CC8 (17.0%), CC45 (13.2%) and CC30 (9.4%). The lukF/S genes were absent from our isolates and tst-1 was found in 9.4% of the strains. Under static conditions and without exposure to glucose, biofilm production was rare (9.4% of the strains, without any CC398). The percentage increased to 62.3% for strains grown in broth supplemented with 1% glucose (including 7 out of 9 CC8 and 17 out of the 20 CC398). Further study of the CC398, including whole genome sequencing, revealed (1) highly frequent patient death within seven days after CC398 bacteremia diagnosis (47.4%), (2) 95.0% of the strains producing biofilm when exposed to sub-inhibitory concentrations of cloxacillin, (3) a stronger biofilm production following exposure to cloxacillin than that observed in broth supplemented with glucose only (p < 0.001), (4) a high minimum biofilm eradication concentration of cloxacillin (128 mg/L) indicating a low cloxacillin susceptibility of biofilm-growing CC398, (5) 95.0% of the strains carrying a ϕSa-3 like prophage and its particular evasion cluster (i.e., yielding chp and scin genes), and (6) 30.0% of the strains carrying a ϕMR11-like prophage and yielding a higher ability to produce biofilm. Our results provide evidence that active surveillance is required to avoid spreading of this virulent staphylococcal clone.

Efficiency of Multifunctional Antibacterial Hydrogels for Chronic Wound Healing in Diabetes: A Comprehensive Review

Diabetic chronic wounds or amputation, which are complications of diabetes mellitus (DM), are a cause of great suffering for diabetics. In addition to the lack of oxygen, elevated reactive oxygen species (ROS) and reduced vascularization, microbial invasion is also a critical factor that induces non-healing chronic diabetic wounds, ie, wounds still remaining in the stage of inflammation, after which the wound tissue begins to age and becomes necrotic. To clear up the infection, alleviate the inflammation in the wound and prevent necrosis, many kinds of hydrogel have been fabricated to eliminate infections with pathogens. The unique properties of hydrogels make them ideally suited to wound dressings because they provide a moist environment for wound healing and act as a barrier against bacteria. This review article will mainly cover the recent developments and innovations of antibacterial hydrogels for diabetic chronic wound healing.

Flavaspidic acid BB combined with mupirocin improves its anti-bacterial and anti-biofilm activities against Staphylococcus epidermidis

BACKGROUND

The increase in drug-resistant opportunistic pathogenic bacteria, especially of antibiotic-resistant Staphylococcus epidermidis (S. epidermidis), has led to difficulties in the treatment of skin and soft tissue infections (SSTI). The major reason for bacterial resistance is the formation of bacterial biofilm. Here, we report a promising combination therapy of flavaspidic acid BB (BB) and mupirocin, which can effectively eradicate the biofilm of S. epidermidis and eliminate its drug resistance.

RESULT

The susceptibility test showed that the combination of BB and mupirocin has good antibacterial and antibiofilm activities, and the fractional inhibitory concentration index (FICI) of BB combined with mupirocin was 0.51 ± 0.00 ~ 0.75 ± 0.05, showing synergistic effect. Moreover, the time-kill curve assay results indicated that the combination of drugs can effectively inhibit the planktonic S. epidermidis. After drugs treatment, the drug-combination showed significantly inhibitory effects on the metabolic activity and total biomass in each stage of biofilm formation. The synergistic effect is likely related to the adhesion between bacteria, which is confirmed by field emission scanning electron microscope. And the expression level of aap, sarA and agrA genes were detected by real-time quantitative PCR (qRT-PCR).

CONCLUSION

Our study provides the experimental data for the use of BB for the clinical treatment of skin infections and further demonstrate the potential of BB as a novel biofilm inhibitor.

Efficacy of antimicrobial peptide LL-37 against biofilm forming Staphylococcus aureus strains obtained from chronic wound infections

The antimicrobial peptide LL-37 showed inhibitory effects against Staphylococcus aureus strains, which often responsible for wound infections. Understanding the molecular mechanisms of biofilm-containing wound infections is important. Thus, this study aimed to investigate both the antimicrobial and biofilm efficacy of LL-37 against biofilm-positive methicillin-susceptible S. aureus (MSSA) strains and biofilm-positive methicillin-resistant S. aureus (MRSA) strains obtained from chronic wound infections and its effect on different quorum sensing and virulence genes at suboptimal concentrations. Fifteen biofilm-forming MRSA and 15 biofilm-forming MSSA strains were included in this study. The minimum inhibitory concentration (MIC) values and biofilm formation were tested by microdilution methods. Real-time PCR was performed to determine gene expression levels. MIC values for LL-37 were 89.6 mg/L and 132.3 mg/L for MSSA and MRSA strains, respectively. No statistically significant difference was found between MRSA and MSSA strains in terms of the effect of LL-37 on biofilm formation. A statistically significant difference was found between MRSA and MSSA strains for atlA, RNAIII, and agrA gene expression levels following exposure to a suboptimal concentration of LL-37. Ultimately, the required LL-37 antimicrobial concentration was quite high; however, LL-37 antibiofilm concentration may be acceptable for use in humans against biofilm-forming MRSA and MSSA strains. This is the first study to investigate to effect of a suboptimal LL-37 concentration on gene expression levels of biofilm-forming MSSA and MRSA strains. LL-37 affected quorum sensing and biofilm producing mechanisms, even at suboptimal MIC concentrations.

Efficacy of a novel antimicrobial hydrogel for eradication of Staphylococcus epidermidis, Staphylococcus aureus and Cutibacterium acnes from preformed biofilm and treatment performance in an in vivo MRSA wound model

BACKGROUND

Bacterial biofilm formation is a complicating factor in the antimicrobial treatment of bacterial infections.

OBJECTIVES

In this study, we assessed the impact of a novel hydrogel with the active antimicrobial compound JBC 1847 on eradication of preformed biofilms of Staphylococcus epidermidis, Cutibacterium acnes and MRSA in vitro, and evaluated the in vivo efficacy of MRSA wound treatment.

METHODS

Biofilms were exposed to JBC 1847 for 24 h and subsequently the treatments were neutralized and surviving biofilm-associated bacteria recovered and enumerated. The efficacy of the hydrogel on post-treatment load of MRSA was determined in a murine model of MRSA wound infection, and skin samples of the infected mice were examined histologically to evaluate the degree of healing.

RESULTS

A concentration-dependent eradication of biofilm-embedded bacteria by JBC 1847 was observed for all three pathogens, and the hydrogel caused a greater than four log reduction of cfu in all cases. In the mouse model, treatment with the hydrogel significantly reduced the cfu/mL of MRSA compared with treatment of MRSA-infected wounds with pure hydrogel. Histopathological analysis of the wounds showed that the JBC 1847 treatment group had a lower grade of inflammation, a higher mean score of re-epithelization and higher mean scores of parameters assessing the maturity of the newly formed epidermis, compared with both the fusidic acid 2% and vehicle treatment groups.

CONCLUSIONS

The novel hydrogel shows promising results as a candidate for future wound treatment, likely to be highly effective even in the case of biofilm-complicating infected wounds.

Virulence alterations in staphylococcus aureus upon treatment with the sub-inhibitory concentrations of antibiotics

Background

The treatment of patients with Staphylococcus aureus infections mainly relies on antistaphylococcal regimens that are established with effective antibiotics. In antibiotic therapy or while living in nature, pathogens often face the sub-inhibitory concentrations (sub-MICs) of antibiotics due to drug pharmacokinetics, diffusion barriers, waste emission, resistant organism formation, and farming application. Different categories of antibiotics at sub-MICs have diverse effects on the physiological and chemical properties of microorganisms. These effects can result in virulence alterations. However, the mechanisms underlying the actions of antibiotics at sub-MICs on S. aureus virulence are obscure.

Aim of review

In this review, we focus on the effects of sub-MICs of antibiotics on S. aureus virulence from the aspects of cell morphological change, virulence factor expression, bacterial adherence and invasion, staphylococcal biofilm formation, and small-colony variant (SCV) production. The possible mechanisms of antibiotic-induced S. aureus virulence alterations are also addressed.

Key scientific concepts of review

Five main aspects of bacterial virulence can be changed in S. aureus exposure to the sub-MIC levels of antibiotics, resulting in deformed bacterial cells to stimulate abnormal host immune responses, abnormally expressed virulence factors to alter disease development, changed bacterial adhesion and invasion abilities to affect colonization and diffusion, altered biofilm formation to potentate material-related infections, and increased SCV formation to achieve persistent infection and recurrence. These advanced findings expand our knowledge to rethink the molecular signaling roles of antibiotics beyond their actions as antimicrobial agents.

Small Alarmone Synthetases RelP and RelQ of Staphylococcus aureus Are Involved in Biofilm Formation and Maintenance Under Cell Wall Stress Conditions

The stringent response is characterized by the synthesis of the alarmone (p)ppGpp. The phenotypic consequences resulting from (p)ppGpp accumulation vary among species, and for several pathogenic bacteria, it has been shown that the activation of the stringent response strongly affects biofilm formation and maintenance. In Staphylococcus aureus, (p)ppGpp can be synthesized by the RelA/SpoT homolog Rel upon amino acid deprivation or by the two small alarmone synthetases RelP and RelQ under cell wall stress. We found that relP and relQ increase biofilm formation under cell wall stress conditions induced by a subinhibitory vancomycin concentration. However, the effect of (p)ppGpp on biofilm formation is independent of the regulators CodY and Agr. Biofilms formed by the strain HG001 or its (p)ppGpp-defective mutants are mainly composed of extracellular DNA and proteins. Furthermore, the induction of the RelPQ-mediated stringent response contributes to biofilm-related antibiotic tolerance. The proposed (p)ppGpp-inhibiting peptide DJK-5 shows bactericidal and biofilm-inhibitory activity. However, a non-(p)ppGpp-producing strain is even more vulnerable to DJK-5. This strongly argues against the assumption that DJK-5 acts via (p)ppGpp inhibition. In summary, RelP and RelQ play a major role in biofilm formation and maintenance under cell wall stress conditions.

Effects of subinhibitory concentrations of chlorhexidine and mupirocin on biofilm formation in clinical meticillin-resistant Staphylococcus aureus

BACKGROUND

The effects of subinhibitory concentrations (sub-MICs) of antibacterial agents on the biofilm-forming ability of Staphylococcus aureus require further study.

AIM

To investigate the effects of sub-MICs of chlorhexidine and mupirocin on biofilm formation in clinical meticillin-resistant Staphylococcus aureus (MRSA) isolates.

METHODS

MRSA isolates were collected from patients with bloodstream infections at a tertiary care hospital. The basal level of biofilm formation and biofilm induction by sub-MICs of chlorhexidine and mupirocin were evaluated by measuring biofilm mass stained with Crystal Violet.

FINDINGS

Of the 112 MRSA isolates tested, 63 (56.3%) and 44 (39.3%) belonged to sequence type (ST)5 and ST72 lineages, respectively, which are the predominant healthcare- and community-associated clones in South Korea. ST5 isolates were more likely to have chlorhexidine MIC ≥4 (73.0% vs 29.5%), resistance to mupirocin (23.8% vs 0%), agr dysfunction (73.0% vs 9.1%), and qacA/B gene (58.7% vs 2.3%) compared to ST72 isolates. The basal level of biofilm formation ability was frequently stronger in ST72 isolates compared to ST5 isolates (77.3% vs 12.7%). Sub-MICs of chlorhexidine and mupirocin promoted biofilm formation in 56.3% and 53.6%, respectively, of all isolates. Biofilm induction was more prevalent in ST5 isolates (85.7% for chlorhexidine, 69.8% for mupirocin) than in ST72 isolates (15.9% for chlorhexidine, 27.3% for mupirocin).

CONCLUSION

Sub-MICs of chlorhexidine and mupirocin promoted biofilm formation in half of the clinical MRSA isolates. Our results suggest that ST5 MRSA biofilm can be induced together with some other bacterial virulent factors following exposure to chlorhexidine, which might confer a survival advantage to this clone in the healthcare environment.

Relationship between biofilm gene expression with antimicrobial resistance pattern and clinical specimen type based on sequence types (STs) of methicillin-resistant S. aureus

The ica genes in methicillin-resistant Staphylococcus aureus (MRSA) play an important role in biofilm formation. The aim of this study is to define effect of antibiotic resistance and clinical specimens to the expression of ica genes based on their sequence types (STs) and clonal complex (CC). One-hundred (100) S. aureus strain were collected from two teaching therapeutic centers in Hamedan, Iran. Then, the PCR, qPCR, and MLST were used to characterize strains. The results indicated that 29 (29%), 15 (15%), and 5 (5%) strain were strong, mediate, weak biofilm producer, respectively, and the icaA (17%) and icaC (14%) genes were the most abundant. However, two unique STs (3667, 491) in Iran were reported and ST30 and ST11 were the most abundant STs and CC30 and CC5 were observed among MRSA and MSSA strains. High activity in ica locus was observed among strains collected from wound and catheter strains. Also, expression level of icaA gene increased in all strains except ST30 and ST491. Moreover, the highest expression level was observed in CC1, CC7, and CC11. Likewise, activity of the icaC gene was only observed in CC5. Furthermore, the expression of all ica genes in CC5 was significantly correlated with the type of biofilm and the clinical sample. In this study demonstrated that the frequency distribution of STs and CCs in different strains of MRSA was higher than methicillin-sensitive strains. Also, the type of clinical specimen and expression of ica genes played an important role in this abundance.

Anti-biofilm activity of garlic extract loaded nanoparticles

The emergence and widespread distribution of multi-drug resistant bacteria are considered as a major public health concern. The inabilities to curb severe infections due to antibiotic resistance have increased healthcare costs as well as patient morbidity and mortality. Bacterial biofilms formed by drug-resistant bacteria add additional challenges to treatment. This study describes a solgel based nanoparticle system loaded with garlic extract (GE-np) that exhibits: i) slow and sustained release of garlic components; ii) stabilization of the active components; and iii) significant enhancement of antimicrobial and antibiofilm activity relative to the free garlic extract. Also, GE-np were efficient in penetrating and disrupting the well-established methicillin-resistant Staphylococcus aureus (MRSA) biofilms. Overall, the study suggests that GE-np might be a promising candidate for the treatment of chronic infections due to biofilm forming drug-resistant bacteria.

The Effect of Subinhibitory Concentrations of trans-Anethole on Antibacterial and Antibiofilm Activity of Mupirocin Against Mupirocin-Resistant Staphylococcus aureus Strains

Aim: The aim of this study was to evaluate the effect of subinhibitory concentrations of trans-anethole on antibacterial and antibiofilm properties of mupirocin against mupirocin-resistant Staphylococcus aureus strains. Methods: Following parameters were examined: isolates susceptibility to antibiotics, minimum inhibitory concentration (MIC) of trans-anethole, antibacterial activity of mupirocin/trans-anethole combination, detection of ileS2 gene, genotypic relativity of isolates using pulsed-field gel electrophoresis method, and the influence of mupirocin/trans-anethole combination on S. aureus biofilm formation. Results: Our study revealed that trans-anethole combined with mupirocin increased the growth inhibition zone diameter around the mupirocin disk, independently on S. aureus strains susceptibility to this antibiotic. Moreover, combination of subinhibitory (MIC₅₀) concentration of mupirocin and trans-anethole significantly decreased biofilm biomass. Conclusions: trans-Anethole appeared efficient in increasing susceptibility to mupirocin and decreasing biofilm formation in S. aureus strains used in this study. Reduction of biofilm formation can potentially protect against S. aureus recolonization. Moreover, use of trans-anethole in combination with mupirocin can increase the mupirocin activity against methicillin-resistant and mupirocin-resistant S. aureus strains.

Morphological and Biological Characteristics of Staphylococcus aureus Biofilm Formed in the Presence of Plasma

Characteristics of Staphylococcus aureus infections include biofilm formation, leading to the spread of bacteria to the bloodstream causing sepsis and metastatic infections. In particular, in methicillin-resistant S. aureus (MRSA) infections, biofilm formation critically hampers treatment and causes poor prognosis. We explored the biofilm formation of MRSA in the presence or absence of plasma and compared morphological characteristics, accumulation of antibiotics, and resistance to bactericidal activity, using continuous optimizing confocal reflection microscopy. Addition of plasma significantly increased biofilm formation, which is characterized by an uneven surface and aggregation of bacteria (hereafter plasma biofilm). The flow-cell system, which enabled a continuous supply of plasma, accelerated biofilm formation in both the tested strains of MRSA (BAA1556 and N315). Accumulation of green fluorescence-labeled vancomycin was observed within 5 minutes in the plasma-free biofilm, but not in the plasma biofilm. Delay of accumulation was also observed for daptomycin in plasma biofilm. Plasma biofilm bacteria were more resistant to anti-MRSA antibiotics than plasma-free biofilm bacteria. These data demonstrate that the plasma biofilm of S. aureus is substantially different from the plasma-free biofilm. Plasma biofilm, especially in the flow-cell system, could be a clinically relevant model to analyze MRSA infections and treatment.

Comparison of structures and cytotoxicity of mupirocin and batumin against melanoma and several other cancer cell lines

Aim: To determine the computer-predicted anticancer activity of mupirocin and to compare its activities with those determined for another polyene antibiotic, batumin. Materials & methods: Molecular docking, cytotoxicity assays, cell microscopy and cell cycle progression were studied in cancer and nontumorigenic cell lines. Results & conclusion: Cytotoxicity of mupirocin against several cancerous cell lines was detected with the highest one (IC₅₀ = 5.4 μg/ml) against melanoma cell line. The profile of cytotoxicity of mupirocin was similar to that reported for batumin. Nevertheless, the morphology of cells treated with these antibiotics and alterations in cell cycle progression suggested possible dissimilarity in their mechanisms of action. Selective cytotoxicity of mupirocin against melanoma cells potentiates further studies to discover nontoxic drugs for melanoma prevention.