Antifungal susceptibility of Candida albicans in biofilms.

Candida albicans are the most common fungi associated with biofilm-related infections. Biofilms are defined as microbial communities encased in a matrix of extracellular polymeric substances. The most important feature of biofilm growth is the high resistance to antimicrobial agents that can be up to 1000-fold greater than that of planktonic cells. This review discusses the factors affecting antifungal resistance as well as activity of mono- and combination therapy of different antifungal classes and antifungal activity in vitro and in vivo against C. albicans biofilms.

Biofilm formation of Candida spp. isolates from patients at a cardiothoracic intensive care unit.

Invasive Candida infections in seriously ill patients are rare but associated with high mortality, while Candida colonization of the mucocuteneous surfaces is common in patients admitted to intensive care units. To investigate biofilm formation as a possible virulence factor, we analyzed the biofilm formation of 128 non-invasive isolates from long-term ICU patients and that of 106 invasive bloodstream isolates. Candida biofilms were quantified by the percent transmittance (%Tbloc) method. Crystal Violet (CV) staining was used as marker of biofilm thickness, and XTT assay was used as a marker of the metabolic activity of Candida cells. The ability of biofilm formation was 99.2% in the non-invasive isolates versus 96.2% in the bloodstream isolates (%Tbloc vs.%Tbloc not significant). However, high biofilm production (%Tbloc, ≥35) was more frequent among the non-invasive isolates compared to the bloodstream isolates (78.1 vs. 72.5, p<0.001).

Design and use of Candida scores at the intensive care unit.

Invasive Candida infections are recognised as a cause of increased morbidity and mortality in intensive care patients, particularly those with recent extensive gastroabdominal surgery. Due to the difficulties of diagnosis, several authors have analysed risk factors suggestive of invasive candidiasis to identify patients at highest risk. Such patients may be potential candidates for preemptive antifungal therapy before becoming seriously ill. The extent of body site colonisation due to Candida species was recognised to be related with consequent invasive disease. The quantification of the colonisation was expressed as the Candida colonisation index. Based on the evaluation of independent risk factors predictive of invasive Candida infections, clinically relevant scores were evaluated in the last decade. Particularly, the Candida score that combines the clinical risk factors preceding surgery, total parenteral nutrition and severe sepsis with Candida multi-site colonisation can be considered a useful bedside scoring system to discern patients with mere Candida colonisation from patients with the risk of invasive candidiasis in non-neutropaenic critically ill patient population.

Acute cardiac disease in a young patient with Campylobacter jejuni infection: a case report.

INTRODUCTION: Infectious myocarditis is a life-threatening condition because it can lead to arrhythmia, dilated cardiomyopathy and congestive heart failure. A large number of different infectious causes have been identified as leading to myocarditis, with enteroviral infections being the most common reasons. CASE PRESENTATION: We present a rare Austrian case of bacterial-induced myocarditis in a 19-year-old immunocompetent male without any cardiac risk factors. Four days prior to the onset of severe left thoracic pain the patient developed acute gastroenteritis. The initial electrocardiogram showed sinus tachycardia, strain on the right side of the heart and signs of myocardial injury. Cardiac enzyme markers creatine kinase and troponin T were elevated to maximum values of 627 U/l and 0.52 ng/ml. Stool cultures revealed the presence of Campylobacter jejuni as the only source of infection. The clinical diagnosis of bacterial-induced myocarditis was confirmed by specific radiological findings of inflammation using cardiac magnetic resonance imaging. CONCLUSION: In recent years, instead of performing endomyocardial biopsies, the clinical diagnosis of bacterial-induced myocarditis can be confirmed by specific radiological findings in combination with positive stool cultures for Enterobacteriaceae. Due to the increasing numbers of Campylobacter infections, myocarditis should be considered as a rare but relevant extraintestinal complication also in immunocompetent patients with Campylobacter jejuni gastroenteritis.

In vitro activity of antifungal combinations against Candida albicans biofilms.

OBJECTIVES: The aim of the present study was to evaluate the in vitro activity and synergism of the combinations of amphotericin B/caspofungin and amphotericin B/posaconazole against Candida albicans, grown either as planktonic cells or in biofilms. METHODS: Ten C. albicans bloodstream isolates used in this study were collected from intensive care patients admitted to the Vienna University Hospital between 2006 and 2007. Chequerboard tests were employed to determine the efficacy of the antifungal combinations amphotericin B/caspofungin and amphotericin B/posaconazole against both planktonic cells and biofilms. C. albicans biofilms were prepared using the static microtitre plate model. The activity of antifungal combination therapy was determined by visual reading for planktonic cells and using the XTT assay for biofilms. RESULTS: For Candida biofilms the median MIC was 4 mg/L for amphotericin B and caspofungin, and >256 mg/L for posaconazole. The combination amphotericin B/posaconazole yielded synergism [fractional inhibitory concentration index (FICI) <0.26], whereas amphotericin B/caspofungin yielded indifferent interaction only (FICI 0.75-1.25) against all isolates when grown in biofilms. Under planktonic conditions, synergism was demonstrable for the combination amphotericin B/caspofungin against 4 of the 10 isolates, whereas the combination of caspofungin/posaconazole was indifferent against all tested isolates. CONCLUSIONS: We showed that MICs for planktonic and biofilm forms of C. albicans were much lower when treated with an antifungal combination than when treated with single agents. The combination of amphotericin B/posaconazole yielded synergism against Candida biofilms, whereas amphotericin B/caspofungin yielded indifferent interaction.

Antifungal activity of amphotericin B, caspofungin and posaconazole on Candida albicans biofilms in intermediate and mature development phases.

The aim of this study was to examine the antifungal activity of amphotericin B, caspofungin and posaconazole on Candida albicans biofilms in the intermediate and mature development phases. Candida albicans biofilms, previously grown for either 24, 48 or 72 h in 96-well microtitre plates, were treated for 48 h with amphotericin B, caspofungin or posaconazole in increasing concentrations according to the respective minimal inhibitory concentration (MIC) determined for planktonic cells (1-128 x MIC). The biofilms were quantified using the mean optical density (OD) determined by XTT assay. Antifungal activities were expressed as percentage of reduction in OD of drug-treated biofilms compared to untreated biofilms. To test the fungicidal activity of antifungal agents, the unfixed biofilms were scraped off and seeded to Sabouraud agar. Caspofungin and amphotericin B showed higher activity against C. albicans biofilm grown for 24 h and 72 h (>or=50% reduction of OD) than biofilms grown for 48 h, whereas posaconazole showed similar, but reduced activity against all phases of C. albicans biofilm (

In vitro activity of daptomycin and tigecycline against coagulase-negative staphylococcus blood isolates from bone marrow transplant recipients.

BACKGROUND AND OBJECTIVE: Multi-resistant coagulase-negative staphylococci (CNS) may cause systemic infections in patients undergoing bone marrow transplantation. Daptomycin, a new lipopeptide, and tigecycline, a new glycylcycline, have excellent activity against Gram-positive bacteria including methicillin-resistant staphylococci. This study presents the in vitro activity of daptomycin and tigecycline compared to vancomycin and fosfomycin against 105 CNS isolated from 76 bone marrow transplant patients with symptomatic bacteremia. MATERIAL AND METHODS: Blood stream isolates of Staphylococcus epidermidis (n = 102) and Staphylococcus haemolyticus (n = 3) from bone marrow transplant patients were collected from 2000 to 2006. The susceptibility of all isolates was tested using methods of the Clinical Laboratory Standards Institute. RESULTS: The minimal inhibitory concentrations MIC(50) and MIC(90) were 0.125 microg/mL and 0.25 microg/mL for daptomycin, 0.25 and 0.5 microg/mL for tigecycline, 1 microg/mL and 2 microg/mL for vancomycin, and 8 microg/mL and >256 microg/mL for fosfomycin, respectively. MIC values of tested agents were similar for both methicillin-sensitive and methicillin-resistant S. epidermidis strains. CONCLUSIONS: All CNS isolates were susceptible to the new antistaphylococcal agents daptomycin and tigecycline. Although vancomycin had been used over the past 30 yr at our bone marrow transplant unit all CNS were still susceptible to vancomycin.

In vivo activity of a novel polymeric guanidine in experimental skin infection with methicillin-resistant Staphylococcus aureus.

The in vivo efficacy of the novel polymeric guanidine AKACID Plus was evaluated in a guinea pig model of experimental skin infection with methicillin-resistant Staphylococcus aureus (MRSA). Topical application of AKACID Plus at concentrations of > or =0.5% was as effective as mupirocin 2% cream in the treatment of superficial skin infection with MRSA.

Comparative activities of antibiotics against intracellular non-typeable Haemophilus influenzae.

INTRODUCTION: Non-typeable Haemophilus influenzae (NTHi) is a major bacterial pathogen of community-acquired respiratory tract infection and is usually found extracellularly, although studies have revealed that NTHi may possess the ability to invade human epithelial cells where it is then protected against attack by the local immune system and partly against the effect of antibiotics. The aim of the present study was to assess the ability of ampicillin, azithromycin, telithromycin, ciprofloxacin and moxifloxacin, five antibiotics in common clinical use, to kill NTHi within bronchial epithelial cells. METHODS: Confluent human bronchial epithelial cells were infected with NTHi 77, a particularly invasive clinical strain. Extracellular bacterial cells were killed with gentamicin and the intracellular bacteria were incubated with antibiotics at concentrations of 1 mg/l or 10 mg/l for 4 h or 8 h. Viable intracellular bacteria were counted after lysis of the epithelial cells. RESULTS: With the exception of ampicillin, all the antibiotics caused significant reduction of intracellular bacteria at concentrations of 10 mg/l and exposure for 4 h or at 1 mg/l for 8 h. At 1 mg/l, moxifloxacin eliminated 94% of intracellular NTHi after 4 h and 98% after 8 h; ciprofloxacin, azithromycin and telithromycin only achieved killing indices below 75 after 4 h but 86-90% killing after 8 h. At 10 mg/l, moxifloxacin, ciprofloxacin, telithromycin and azithromycin were able to achieve 99.7%, 96.3%, 86.7% and 74.7% eradication of intracellular bacteria, respectively, after exposure for 4 h. CONCLUSION: These results demonstrate the rapid antibacterial efficacy of moxifloxacin against intracellular NTHi in vitro. Moxifloxacin, which combines high extracellular and intracellular activities, could be an important tool in the treatment of recurrent respiratory tract infections.

In vitro activity and synergism of amphotericin B, azoles and cationic antimicrobials against the emerging pathogen Trichoderma spp.

OBJECTIVES: The uncommon fungal pathogen Trichoderma shows increasing medical importance particularly in immunocompromised patients. Despite systemic antifungal therapy, prognosis of Trichoderma infection is poor regardless of the type of infection and the therapy used. The aim of the present study was to evaluate the in vitro activity and synergism of double antifungal combinations including amphotericin B, voriconazole, fluconazole, chlorhexidine digluconate and Akacid plus against 15 isolates of Trichoderma longibrachiatum and 1 isolate of Trichoderma harzianum. METHODS: Individual MICs were determined by using broth microdilution method following the NCCLS M38-A guidelines with standard RPMI 1640 broth. Synergy tests were performed using the chequerboard method. RESULTS: All clinical Trichoderma strains showed reduced susceptibility to fluconazole (MICs>or=64 mg/L) and amphotericin B (MICs=2 mg/L), whereas lower MICs of 0.5-1 mg/L were detected for voriconazole. Akacid plus reached the lowest MIC values in a range of 0.06-0.5 mg/L, 4- to 32-fold higher MICs were found for chlorhexidine. No antagonism was observed for any of the antifungal combinations tested. Interaction of amphotericin B and azoles was indifferent (fractional inhibitory concentration index, FICI 2-4). The combination of one azole and one cationic biocide showed different degree of synergism (FICI 0.07-2.03). Interaction of Akacid plus and chlorhexidine resulted in synergism for each Trichoderma isolate (FICI-range 0.05-0.5). CONCLUSIONS: These results demonstrate no interaction between antifungals and some degree of synergism between azoles and cationic antimicrobials against Trichoderma spp.

Validation of AKACID plus as a room disinfectant in the hospital setting.

AKACID Plus, a novel polymeric guanidine with broad antimicrobial activity against multiantibiotic-resistant bacterial strains, was used in the present study as a room disinfectant. Disinfection of closed rooms experimentally contaminated with antibiotic-susceptible and multiresistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Escherichia coli was performed using AKACID Plus at concentrations of 0.1, 0.25, and 0.5% for 100 min. Bacterial suspensions were distributed on plastic and stainless steel plates and placed in a test room. Recovery of the test microorganisms was determined before nebulizing, 60 and 100 min after initiation, and 4 h after the end of room disinfection by a simple swab-rinse technique. The swab-rinse method demonstrated a dose- and time-dependent effectiveness of AKACID Plus in eradicating S. aureus, E. coli, and P. aeruginosa on plastic and stainless steel plates. Nebulized 0.5% AKACID Plus was successful in eliminating all hospital pathogens within 340 min. After the use of 0.25% AKACID Plus, MRSA was still detectable on microbial carrier plates. The test concentration of 0.1% AKACID Plus achieved a significant reduction of S. aureus and P. aeruginosa on plastic and stainless steel plates but was sufficient to eradicate only E. coli. These results suggest that nebulized AKACID Plus at a concentration of 0.5% is a potent substance for eradication of pathogenic organisms in the hospital setting.

Antimicrobial and toxicological profile of the new biocide Akacid plus.

OBJECTIVES: Akacid plus is a new member of the polymeric guanidine family of disinfectants. It was especially developed to enhance the antimicrobial activity of this class with significantly less toxicity. The in vitro activity of Akacid plus compared with chlorhexidine digluconate and mupirocin was tested against a total of 369 recent clinical isolates. METHODS: The organisms tested by CLSI reference methods included the following: Staphylococcus aureus (98), Staphylococcus epidermidis (9), Bacillus spp. (2), Enterococcus faecalis (32), Klebsiella spp. (45), Enterobacter spp. (20), Escherichia coli (65), Salmonella spp. (6), Shigella spp. (2), Yersinia enterocolitica (1), Acinetobacter spp. (4), Proteus spp. (7), Pseudomonas aeruginosa (59), Stenotrophomonas maltophilia (4), Candida spp. (10) and Aspergillus spp. (7). In vitro selection of resistance to Akacid plus was carried out on 24 strains. Toxicological analyses were also performed. RESULTS: All tested agents were more effective against Staphylococcus spp. and Bacillus spp. than against E. faecalis and Gram-negative bacteria. The MIC90s of chlorhexidine and mupirocin showed a 4-fold and 32-fold increase for methicillin-resistant S. aureus in comparison with methicillin-susceptible strains, while MIC values of Akacid plus were similar for antibiotic-susceptible and multiresistant strains. Bactericidal action of Akacid plus was observed at 1-2x MIC. The in vitro selection of resistance test showed no increase in MIC values of Akacid plus for any isolate after 30 passages. In addition, Akacid plus showed low oral and dermal toxicity. CONCLUSIONS: These preliminary results demonstrate the broad antimicrobial properties of Akacid plus, which makes it a promising tool for topical application in the prophylaxis and treatment of bacterial and fungal infections.