Contact-free cold atmospheric plasma treatment of Deinococcus radiodurans

In this study we investigated the sensitivity of Deinococcus radiodurans to contact-free cold atmospheric plasma treatment as part of a project to establish new efficient procedures for disinfection of inanimate surfaces. The Gram-positive D.?radiodurans is one of the most resistant microorganisms worldwide. Stationary phases of D.?radiodurans were exposed to cold atmospheric plasma for different time intervals or to ultraviolet?C (UVC) radiation at dose rates of 0.001-0.0656?J?cm(-2), respectively. A methicillin-resistant Staphylococcus aureus strain (MRSA) served as control for Gram-positive bacteria. The surface microdischarge plasma technology was used for generation of cold atmospheric plasma. A plasma discharge was ignited using ambient air. Surprisingly, D.?radiodurans was sensitive to the cold atmospheric plasma treatment in the same range as the MRSA strain. Survival of both bacteria decreased with increasing plasma exposure times up to 6 log(10) cycles (>99.999?%) within 20?s of plasma treatment. In contrast, UVC radiation of both bacteria demonstrated that D.?radiodurans was more resistant to UVC treatment than MRSA. Cold atmospheric plasma seems to be a promising tool for industrial and clinical purposes where time-saving is a critical point to achieve efficient disinfection of inanimate surfaces and where protection from corrosive materials is needed.     

Selective inactivation of heterokaryons of Candida albicans by anaerobiosis

Heterokaryons (hets), but not monokaryons of Candida albicans die when grown anaerobically on minimal medium. Their rates of inactivation increase with decreases in growth temperatures from 37°C to 25°C. At 10°C, however, anaerobiosis is not lethal and suppresses the inactivation which normally occurs among hets cultured aerobically at that temperature. Killing of hets by anaerobiosis can be altered significantly by certain exogenously provided amino acids or intermediates of oxidative respiration. Aspartic acid alone promotes inactivation whereas alanine, glutamic acid or lysine individually have no effects. However, glutamate and lysine combined afford slight protection against inactivation while aspartate and glutamate combined, with or without lysine, are highly protective: the activity of the aspartate-glutamate combination is completely negated by the addition of alanine. Other common amino acids have no effects on het responses to anaerobiosis other than the ability, when combined, to relieve the antagonism of alanine for the aspartate-glutamate combination. Anaerobic survivals are also enhanced by oxalacetic acid or -ketoglutaric acid, and even more so by a combination of these two intermediates. The resistances to inactivation elicited by the oxalacetate -ketoglutarate or aspartate-glutamate combinations are not additive. These relationships are interpreted to signify that inactivation of hets by anaerobic growth is largely, if not exclusively, due to depletion of their oxalacetic acid and -ketoglutaric acid contents for amino acid biosyntheses, and the unique inability of het cells to replenish those keto acids upon subsequent return to aerobic conditions. The observations are consistent with previous indications that mitochondria formed by hets are functionally abnormal.     

Candida albicans biofilms: more than filamentation

Candida albicans is the fungal species most commonly associated with biofilm formation in immunosuppressed patients. Recent work offers a fresh new look at the role of filamentation in C. albicans biofilm formation, and describes the application of a powerful tool for the molecular dissection of these important developmental processes.     

白念珠菌生物膜的研究

细菌生物膜相关感染发病率不断上升,且治疗困难,已受到广泛的关注。对于真菌,生物膜以及生物膜在真菌感染与耐药性产生过程中的作用只是近年来才受到国内外学者与临床专家的关注,目前的研究多集中在念珠菌属。本文综述了白念珠菌生物膜的形成与特征、影响因素、耐药性的分子机制等几方面内容。     

白念珠菌生物被膜基质研究进展

近年来,白念珠菌耐药性备受关注,其耐药机制之一是形成生物被膜(biofilm).生物被膜主要由大量菌细胞及其所分泌的细胞外多聚基质( matrix)将其包裹所构成,基质含有多糖、蛋白、核酸等成分,不仅参与生物被膜的结构组成,也与耐药性密切相关.本文综述了白念珠菌生物被膜基质的组成特点、功能、影响因素、基因调控和药物干预的最新进展,并展望其在生物被膜感染方面作为诊断标志及治疗靶点的潜在应用前景.     

大蒜素体外抗白念珠菌生物膜作用的初步研究

目的研究大蒜素对体外白念珠菌生物膜的影响。方法 MTT法评价大蒜素对白念珠菌生物膜形成及细胞黏附的影响;血清芽管计数法评价大蒜素对白念珠菌芽管形成的影响。结果低浓度(4μg/mL)和高浓度(64μg/mL)大蒜素对白念珠菌生物膜形成的抑制率分别为(23.0±1.1)%和(95.6±0.3)%;32μg/mL大蒜素对早期(0h)、中期(12h)及成熟期(48h)生物膜的抑制率分别为(88.5±0.5)%、(63.3±0.8)%和(52.3±1.1)%;与空白对照组相比,不同浓度大蒜素(4～32μg/mL)对培养30min、60min、90min、120min的白念珠菌细胞黏附均有显著抑制作用(P0.05);空白对照组芽管形成率为(91.2±1.6)%,64μg/mL大蒜素组为(2.2±1.2)%。结论大蒜素对体外白念珠菌生物膜有较明显的抑制作用。     

穿心莲内酯体外抗白念珠菌生物膜作用的初步研究

目的研究穿心莲内酯对体外白念珠菌生物膜的影响。方法采用XTT减低法评价穿心莲内酯对白念珠菌生物膜及其黏附性的影响;镜下观察该药对白念珠菌生物膜的形态学影响;细胞毒性试验检测该药的毒副作用。结果穿心莲内酯对白念珠菌生物膜的SMIC50、SMIC80分别是250、1000μg/ml;1000μg/ml及100μg/ml时对白念珠菌的早期黏附及菌丝生长有抑制作用;对人细胞毒性较弱。结论穿心莲内酯对体外白念珠菌生物膜有显著的抑制作用。     

Sensitization of Candida albicans biofilms to various antifungal drugs by cyclosporine A

Background

Biofilms formed by Candida albicans are resistant towards most of the available antifungal drugs. Therefore, infections associated with Candida biofilms are considered as a threat to immunocompromised patients. Combinatorial drug therapy may be a good strategy to combat C. albicans biofilms.

Methods

Combinations of five antifungal drugs- fluconazole (FLC), voriconazole (VOR), caspofungin (CSP), amphotericin B (AmB) and nystatin (NYT) with cyclosporine A (CSA) were tested in vitro against planktonic and biofilm growth of C. albicans. Standard broth micro dilution method was used to study planktonic growth, while biofilms were studied in an in vitro biofilm model. A chequerboard format was used to determine fractional inhibitory concentration indices (FICI) of combination effects. Biofilm growth was analyzed using XTT-metabolic assay.

Results

MICs of various antifungal drugs for planktonic growth of C. albicans were lowered in combination with CSA by 2 to 16 fold. Activity against biofilm development with FIC indices of 0.26, 0.28, 0.31 and 0.25 indicated synergistic interactions between FLC-CSA, VOR-CSA, CSP-CSA and AmB-CSA, respectively. Increase in efficacy of the drugs FLC, VOR and CSP against mature biofilms after addition of 62.5 μg/ml of CSA was evident with FIC indices 0.06, 0.14 and 0.37, respectively.

Conclusions

The combinations with CSA resulted in increased susceptibility of biofilms to antifungal drugs. Combination of antifungal drugs with CSA would be an effective prophylactic and therapeutic strategy against biofilm associated C. albicans infections.     

Photodynamic inactivation for controlling Candida albicans infections

Antimicrobial photodynamic therapy (APDT) combines a non-toxic dye, termed photosensitizer, which is activated by visible light of appropriate wavelength which will produce reactive oxygen species (ROS). These ROS will react with cellular components inducing oxidative processes, leading to cell death. A wide range of microorganisms, have already showed susceptibility to APDT. Therefore, this treatment might consist in an alternative for the management of fungal infections that is mainly caused by biofilms, since they respond poorly to conventional antibiotics and may play a role in persistent infections. Biofilms are the leading cause of microbial infections in humans, thus representing a serious problem in health care. Candida albicans is the main type of fungi able to form biofilms, which cause superficial skin and mucous membrane infections as well as deep-seated mycoses, particularly in immunocompromised patients. In these patients, invasive infections are often associated with high morbidity and mortality. Furthermore, the increase in antifungal resistance has decreased the efficacy of conventional therapies. Treatments are time-consuming and thus demanding on health care budgets. Additionally, current antifungal drugs only have a limited spectrum of action and toxicity. The use of APDT as an antimicrobial topical agent against superficial and cutaneous diseases represents an effective method for eliminating microorganisms.     

APNP对白念珠菌杀菌效果研究

目的 研究常压低温等离子体(APNP)喷流对白念珠菌的杀灭作用,并初步探讨其杀菌机制.方法 观察白念珠菌标准株经不同放电气体流量、作用时间及作用距离的APNP喷流处理后的菌落生长情况,并利用扫描电镜与透射电镜观察处理后念珠菌细胞内外超微结构的变化.结果 经APNP处理后的菌株生长明显被抑制,通入的放电气体He/O2以2/0.06 L/min的抑制作用比2/0.02 L/min明显,处理时间10 min明显优于2 min,作用距离1 cm优于2 cm.扫描电镜观察APNP处理后的菌体细胞壁有不同程度的破裂,菌体干瘪,透射电镜下可见菌体细胞壁、细胞膜破裂,胞内物质外漏,细胞内物质稀疏.结论 APNP喷流对白念珠菌有明显的杀灭效果,且放电气体中氧气含量相对越大,处理时间越长,作用距离越短,杀菌效果也越明显.其主要杀菌机制可能与APNP中活性粒子导致微生物细胞壁、细胞膜的破裂有关.     

Destruction of oral biofilms formed in situ on machined titanium (Ti) surfaces by cold atmospheric plasma

The decontamination of implant surfaces represents the basic procedure in the management of peri-implant diseases, but it is still a challenge. The study aimed to evaluate the degradation of oral biofilms grown in situ on machined titanium (Ti) discs by cold atmospheric plasma (CAP). ～ 200 Ti discs were exposed to the oral cavities of five healthy human volunteers for 72?h. The resulting biofilms were divided randomly between the following treatments: CAP (which varied in mean power, treatment duration, and/or the gas mixture), and untreated and treated controls (diode laser, air-abrasion, chlorhexidine). The viability, quantity, and morphology of the biofilms were determined by live/dead staining, inoculation onto blood agar, quantification of the total protein content, and scanning electron microscopy. Exposure to CAP significantly reduced the viability and quantity of biofilms compared with the positive control treatments. The efficacy of treatment with CAP correlated with the treatment duration and plasma power. No single method achieved complete biofilm removal; however, CAP may provide an effective support to established decontamination techniques for treatment of peri-implant diseases.     

On-demand release of Candida albicans biofilms from urinary catheters by mechanical surface deformation

Abstract

Candida albicans is a leading cause of catheter-associated urinary tract infections and elimination of these biofilm-based infections without antifungal agents would constitute a significant medical advance. A novel urinary catheter prototype that utilizes on-demand surface deformation is effective at eliminating bacterial biofilms and here the broader applicability of this prototype to remove fungal biofilms has been demonstrated. C. albicans biofilms were debonded from prototypes by selectively inflating four additional intralumens surrounding the main lumen of the catheters to provide the necessary surface strain to remove the adhered biofilm. Deformable catheters eliminated significantly more biofilm than the controls (>90% eliminated vs 10% control; p < 0.001). Mechanical testing revealed that fungal biofilms have an elastic modulus of 45 ± 6.7 kPa with a fracture energy of 0.4–2 J m^?2. This study underscores the potential of mechanical disruption as a materials design strategy to combat fungal device-associated infections.     

胡桃楸提取物对体外白念珠菌生物膜形成的影响

目的研究胡桃楸提取物对白念珠菌生物膜形成的影响。方法采用甲基四氮盐（XTT）还原法评价胡桃楸提取物对白念珠菌的生物膜形成及黏附性的影响。镜下观察胡桃楸提取物对白念珠菌生物膜的形态学影响。结果胡桃楸提取物抑制白念珠菌生物膜50％及90％的最小抑制药物浓度（SMIC50、SMIC90）分别为15．2μg、23．4μg。胡桃楸提取物作用浓度大于20μg时对该菌细胞黏附有抑制作用。30μg胡桃楸提取物可完全抑制白念珠菌生物膜的形成。结论胡桃楸提取物对体外白念珠菌生物的膜形成有较强的抑制作用。     

Interactions of Candida albicans with other Candida spp. and bacteria in the biofilms

AIMS: To study the interactions between Candida albicans and 12 other species of Candida and bacteria in biofilms. METHODS AND RESULTS: The number of cells within growing biofilms in a polystyrene tube model was measured after adding C. albicans to preformed biofilms of other micro-organisms and vice versa. It was also measured after simultaneous biofilm formation of C. albicans and other micro-organisms. The number of cells of C. albicans within the growing biofilms decreased significantly (P < 0.05) when the fungus was added to preformed biofilms of Candida spp. and bacteria except, with C. parapsilosis, Torulopsis glabrata and the glycocalyx producer Pseudomonas aeruginosa. When C. parapsilosis, Staphylococcus epidermidis (nonglycocalyx producer) or Serratia marcescens was added to preformed biofilms of C. albicans, the number of cells of these micro-organisms increased in the growing biofilms. CONCLUSIONS: Biofilms of C. albicans are capable of holding other micro-organisms and more likely to be heterogeneous with other bacteria and fungi in the environment and on medical devices. SIGNIFICANCE AND IMPACT OF THE STUDY: Recognition of the heterogeneity of biofilm-associated organisms can influence treatment decisions, particularly in patients who do not respond to initial appropriate therapy.