Christina Kratzer

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.

In vitro activity of antifungal combinations against Candida albicans biofilms.

OBJECTIVESnThe 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.nnnMETHODSnTen 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.nnnRESULTSnFor 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.nnnCONCLUSIONSnWe 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 72u2003h in 96‐well microtitre plates, were treated for 48u2003h with amphotericin B, caspofungin or posaconazole in increasing concentrations according to the respective minimal inhibitory concentration (MIC) determined for planktonic cells (1–128u2003×u2003MIC). 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 24u2003h and 72u2003h (≥50% reduction of OD) than biofilms grown for 48u2003h, whereas posaconazole showed similar, but reduced activity against all phases of C. albicans biofilm (≤50% reduction of OD). Caspofungin at 1–4u2003×u2003MIC achieved the greatest decrease in the biofilm OD grown for 24, 48 and 72u2003h, whereas amphotericin B showed dose‐dependent activity. However, all tested antifungals failed to reach fungicidal activity in all biofilm development phases.

Azole-resistant Candida spp. – emerging pathogens?

Invasive fungal infections cause significant morbidity and mortality in immunocompromised patients. Azoles, and fluconazole in particular, are very active against Candida albicans, and are used widely because of their good tolerability. However, the increasing use of azole antifungals for the treatment of mucosal and systemic Candida infections has resulted in the selection and/or emergence of resistant Candida strains. The main mechanisms of azole resistance among Candida species are the development of bypass pathways, alterations in the ERG 11 gene encoding the azole target enzyme, and the up‐regulation of genes encoding efflux pumps. A better understanding of the mechanisms and clinical impact of antifungal resistance is essential to prompt and efficient treatment of patients with invasive mycoses and to improve the outcome of such infections.

Comparative in vitro antimicrobial activity of vancomycin, teicoplanin, daptomycin and ceftobiprole in four different peritoneal dialysis fluids

Peritoneal dialysis used in the treatment of patients with end-stage renal failure is often complicated by peritonitis. Staphylococcus aureus peritonitis is severe, particularly if caused by a methicillin-resistant strain (MRSA). Intraperitoneal administration of drugs for treatment of peritonitis is preferable to intravenous or oral routes because of the resulting higher local antibiotic concentrations. However, peritoneal dialysis fluids (PDFs) have a bacteriostatic effect, which may compromise the efficacy of antibiotics. The bactericidal efficacy of vancomycin, teicoplanin, daptomycin and ceftobiprole was studied in the PDFs Dianeal PD4® (glucose 1.36%), Physioneal 40® (glucose 1.36%), Extraneal® (7.5% icodextrin), and Nutrineal PD4® (1.1% amino acid) using time-kill curves. To simulate in vivo conditions, human serum albumin was added at a final concentration of 2xa0g/l. All four PDFs had a bacteriostatic effect on the growth of the MRSA test isolate. All antibiotics showed less activity in PDFs compared to control broth. Vancomycin and teicoplanin achieved the greatest reduction in bacterial numbers in the amino-acid containing PDF Nutrineal PD4®. Daptomycin showed its highest activity in Extraneal® and better overall efficacy than the other tested antibiotics. Ceftobiprole showed no killing activities in any of the four PDFs. Based on these in vitro data we conclude that the choice of PDFs for intraperitoneal administration is not trivial and could be crucial for therapy outcome.

In Vivo Activity of a Novel Polymeric Guanidine in Experimental Skin Infection with Methicillin-Resistant Staphylococcus aureus

ABSTRACT 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 ≥0.5% was as effective as mupirocin 2% cream in the treatment of superficial skin infection with MRSA.

Validation of AKACID Plus as a Room Disinfectant in the Hospital Setting

ABSTRACT 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.

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

Background and objective:u2002 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.

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

ZusammenfassungEINLEITUNG: Nicht-typisierbarer Haemophilus influenzae (NTHi) ist ein wichtiger bakterieller Erreger ambulant erworbener Infektionen der Atemwege und ist in der Regel extrazellulär zu finden. Studien haben jedoch gezeigt, dass NTHi die Fähigkeit besitzt in menschliche Epithelzellen einzudringen, wo er sowohl vor den Angriffen des lokalen Immunsystems als auch zum Teil vor der Abtötung durch Antibiotika geschützt ist. Ziel der vorliegenden Studie war es, die Fähigkeit der 5 klinisch häufig eingesetzten Antibiotika Ampicillin, Azithromycin, Telithromycin, Ciprofloxacin und Moxifloxacin zu bewerten, NTHi innerhalb von bronchialen Epithelzellen abzutöten. METHODEN: Konfluierende humane bronchiale Epithelzellen wurden mit NTHi 77, einem besonders invasiven klinischen Stamm infiziert. Die extrazellulären Bakterien wurden mittels Gentamicin abgetötet. Die intrazellulären Bakterien wurden mit Antibiotika in einer Konzentration von 1 mg/l oder 10 mg/l für 4 h oder 8 h behandelt. Lebensfähige intrazelluläre Bakterien wurden nach Lyse der Epithelzellen gezählt. ERGEBNISSE: Mit Ausnahme von Ampicillin erreichten alle Antibiotika eine signifikante Reduktion der intrazellulären Bakterien in einer Konzentration von 10 mg/l und einer Expositionszeit für 4 h sowie bei 1 mg/l für 8 h. Bei einer Konzentration von 1 mg/l eliminierte Moxifloxacin 94% der intrazellulären NTHi nach 4 h und 98% nach 8 h. Ciprofloxacin, Azithromycin und Telithromycin erreichten nur Killing-Indices < 75 nach 4 h, jedoch eine 86–90%ige Abtötung nach 8 h. Bei 10 mg/l erreichten Moxifloxacin, Ciprofloxacin, Telithromycin and Azithromycin nach einer Expositionszeit von 4 h eine 99,7%, 96,3%, 86,7% und 74,7%ige Eradikation der intrazellulären Bakterien. SCHLUSSFOLGERUNG: Die Ergebnisse demonstrieren die rasche antibakterielle Effektivität von Moxifloxacin gegenüber intrazellulärem NTHi in vitro. Moxifloxacin, welches hohe extrazelluläre und intrazelluläre Wirksamkeit kombiniert, könnte eine vorteilhafte Substanz in der Behandlung von rezidivierenden Atemwegsinfektionen darstellen.SummaryINTRODUCTION: 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.

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

ZusammenfassungEINLEITUNG: Die infektiöse Myokarditis stellt einen lebensbedrohlichen Zustand dar, der zu Herzrhythmusstörungen, dilatativer Cardiomyopathie und Herzversagen führen kann. Eine Myokarditis kann durch eine Vielzahl an unterschiedlichen Ursachen infektiöser Genese ausgelöst werden, wobei eine Infektion mit Enteroviren die häufigste Ursache darstellt. FALLPRÄSENTATION: Wir präsentieren einen selten österreichischen Fall einer bakteriell induzierten Myokarditis bei einem 19. jährigen immunkompetenten Mann ohne kardiale Risikofaktoren. Vier Tage vor Beginn der kardialen Symptomatik mit heftigem linksseitigen Thoraxschmerz hatte der Patient eine akute Gastroenteritis entwickelt. Das initiale Elektrokardiogramm zeigte eine Sinustachykardie, Rechtsherzbelastung und Zeichen eines Myokardschadens. Herzenzyme Kreatinkinase und Troponin T waren zu Maximumwerten von 627 U/l und 0,52 ng/ml erhöht. Stuhlkulturen enthüllten das Vorliegen von Campylobacter jejuni als einzige Infektionsquelle. Die klinische Diagnose einer bakteriell induzierten Myokarditis wurde durch spezifische radiologische Zeichen der Inflammation mittels kardialer Magnetresonanztomographie bestätigt. SCHLUSSFOLGERUNG: In den letzten Jahren, anstelle der Durchführung von Myokardbiopsien, kann die klinische Diagnose einer bakteriell-induzierten Myokarditis durch spezifische radiologische Befunde in Kombination mit positiven Stuhlkulturen auf Enterobacteriaceae bestätigt werden. Aufgrund der ansteigenden Zahl von Campylobacter Infektionen, sollte die Myokarditis zwar als seltene aber relevante extraintestinale Komplikation auch bei immunkompetenten Patienten mit Campylobacter jejuni Gastroenteritis angesehen werden.SummaryINTRODUCTION: 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.