Airway persistence by the emerging multi‐azole‐resistant Rasamsonia argillacea complex in cystic fibrosis

Infections caused by Rasamsonia argillacea complex have been reported in various clinical settings. Cystic fibrosis (CF) is one of the main underlying conditions. An observational cohort study of CF patients with Rasamsonia in respiratory samples was conducted. Eight isolates from 6 patients were identified as R. argillacea complex and tested for antifungal susceptibility. All isolates had high MICs to voriconazole and posaconazole and low MECs to echinocandins. Four patients experienced lung function decline in the year preceding first Rasamsonia isolation. This continued in the year following first isolation in 3 out of 4 cases. Antifungal therapy was initiated in 2 patients, to which only one exhibited a clinical response. Three out of 6 patients died within 3 years of isolating Rasamsonia. Genotyping suggests that similar genotypes of Rasamsonia can persist in CF airways. Consistent with other fungi in CF, the clinical impact of airway colonisation by Rasamsonia is variable. In certain patients, Rasamsonia may be able to drive clinical decline. In others, though a clear impact on lung function may be difficult to determine, the appearance of Rasamsonia acts as a marker of disease severity. In others it does not appear to have an obvious clinical impact on disease progression.     

In vitro synergistic effects of metergoline and antifungal agents against Candida krusei

Metergoline, a serotonin receptor antagonist, was evaluated for its antifungal activity against the opportunistic human fungal pathogen Candida krusei by a broth microdilution assay. The minimal inhibitory concentration and minimal fungicidal concentration of metergoline against C. krusei were 4 and 8 μg ml^?1 respectively. Significant synergism was found in combination of metergoline with amphotericin B (fractional inhibitory concentration index: 0.375–0.5) by a chequerboard assay. Metergoline also inhibited extracellular phospholipase secretion in a dose‐dependent manner, which may be a possible action mechanism of metergoline on C. krusei.     

In vitro study of antimicrobial activity on Klebsiella Pneumoniae biofilms in endotracheal tubes

Effective treatment approaches for biofilms in endotracheal tubes (ETTs) are lacking. In this study, we evaluated the in vitro effects of five antimicrobials against biofilms formed by Klebsiella pneumoniae in ETTs. K. pneumoniae was added to minimal mucin medium prior to inoculation in microtiter plates containing ETT fragments. Biofilm susceptibility was assessed by crystal violet staining. At 24?h, the antimicrobials significantly reduced biofilm formation. At 48?h, all of the antimicrobial agents exhibited significant reductions in biofilm formation, even at concentrations above the minimum inhibitory concentration (MIC). Tigecycline and fosfomycin showed the greatest inhibition capacity, with good activity at concentrations twofold greater than the MIC. K. pneumoniae exhibited excellent biofilm formation ability, with formation in the first 24?h and significantly reduced antimicrobial activity. These results contribute to the establishment of new antibiotic breakpoints for the adequate management of infections associated with biofilm formation. Abbreviations ETT Endotracheal tube

MIC Minimum inhibitory concentration

MBIC Minimum biofilm inhibitory concentration

OD Optical density

PBS Phosphate-buffered saline

VAP Ventilator-associated pneumonia

     

Suppression of adjuvant arthritis in rats by intraperitoneal Mycobacterium butyricum

Abstract

The In Vitro activity of fluoroquinolones, including lomefloxacin, ofloxacin, ciprofloxacin, sparfloxacin, moxifloxacin and gatifloxacin, was evaluated against 55 clinical isolates of Mycobacterium tuberculosis by absolute concentration method on Lowenstein-Jensen (L-J) and Middlebrook's 7H11 media. Both ofloxacin susceptible and ofloxacin resistant strains of M. tuberculosis isolates were tested. The in vitro activities of these fluoroquinolones on the M. tuberculosis isolates were in the order: lomefloxacin相似文献   

Comparative in vitro fungicidal activity of echinocandins against Candida albicans in peritoneal dialysis fluids

The peritoneal dialysis (PD)‐associated peritonitis caused by fungi is a relatively rare, but very serious disease. PD fluids (PDFs) affect inhibitory efficacy on the microorganisms' growth, which may compromise the affectivity of some antimicrobials. The purpose of this study was to investigate in vitro the fungicidal effectiveness of echinocandins in diverse PDFs. The fungicidal efficacy of caspofungin (CAS), anidulafungin (ANA), micafungin (MYC) against five clinical isolates of Candida albicans was studied in the different PDFs using time‐kill curves. As control substance amphotericin B was used. Echinocandins showed slower and reduced killing of C. albicans in PDFs when compared with the time‐kill curves in control bouillon. At concentration of 8 × minimal inhibitory concentration (MIC) the greatest reduction in the growth of C. albicans was seen by ANA in lactate‐buffered Nutrineal PD4^® with 1.1% amino acid (2.33 ± 0.52 log₁₀ CFU ml^?1), and by CAS and MYC in lactate‐buffered Dianeal PD4^® with 1.36% glucose (2.36 ± 0.89 log₁₀ CFU ml^?1 and 2.36 ± 0.99 log₁₀ CFU ml^?1 respectively). Using high concentration of 128 × MIC echinocandins achieved fungicidal effect in all PDFs. PDFs may significantly impair the activities of echinocandins, but fungicidal activity of drugs can be achieved at high concentration of 128 × MIC.     

Pharmacokinetic/pharmacodynamic parameters for treatment optimization of infection due to antibiotic resistant bacteria: a summary for practical purposes in children and adults

In the last years, there has been a tremendous increase in the incidence of bacterial infections due to resistant strains, especially multi-drug resistant Gram-negative bacilli. In Europe, a north to south and a west to east gradient was noticed, with more than one third of the K. pneumonia isolates being resistant to carbapenems in few countries. New antibiotics are lacking and, as a consequence, pharmacokinetic/pharmacodynamic parameters, normalized to pathogen minimal inhibitory concentration, are used with increased frequency to treat infections due to difficult-to-treat pathogens. These parameters are available at least for the adult population, but sparse in many different publications. This review wants to provide a comprehensive and ‘easy to read’ text for everyday practice, briefly summarizing the presently available knowledge on pharmacokinetic/pharmacodynamic parameters (normalized for minimal inhibitory concentration values) of different class drugs, that can be applied for an effective antibacterial treatment infections due to antibiotic-resistant pathogens.     

The role of drug efflux pumps in Malassezia pachydermatis and Malassezia furfur defence against azoles

This study aims to evaluate the effect of efflux pump modulators (EPMs) on the minimal inhibitory concentration (MIC) of fluconazole (FLZ) and voriconazole (VOR) in Malassezia furfur and Malassezia pachydermatis. The in vitro efficacy of azoles, in combination with EPMs (ie haloperidol‐HAL, promethazine‐PTZ and cyclosporine A‐CYS), against 21 M. furfur from bloodstream infection patients and 14 M. pachydermatis from the skin of dogs with dermatitis, was assessed using a broth microdilution chequerboard analysis. Data were analysed using the model‐fractional inhibitory concentration index (FICI) method. The MIC of FLZ and VOR of Malassezia spp. decreased in the presence of sub‐inhibitory concentrations of HAL and/or PTZ. The synergic effect was observed only in strains with FLZ MIC≥128 μg/mL for M. furfur, FLZ MIC≥64 μg/mL for M. pachydermatis and VOR MIC≥4 μg/mL in both Malassezia spp. These results suggest that the drug efflux pumps are involved as defence mechanisms to azole drugs in Malassezia yeast. The synergism might be related to an increased expression of efflux pump genes, eventually resulting in azole resistance phenomena. Finally, the above FLZ and VOR MIC values might be considered the cut‐off to discriminate susceptible and resistant strains.     

In- Vitro Activity of Ofloxacin against Chlamydia trachomatis

Summary

The in-vitro activity of ofloxacin was evaluated against recently isolated Chlamydia trachomatis strains from patients suffering from non-gonococcal urethritis.

The minimal inhibitory concentration (MIC) proved to be 1 mg/1 against 8 of the 10 strains assayed (the MICs for the other two strains were 0.5 and 2 mg/1).

The data obtained confirm that ofloxacin is active against Chlamydia trachomatis at concentrations achievable with the routine dosage regimen. The drug may thus be regarded as potentially useful for the treatment of non-gonococcal urethritis due to Chlamydia.     

Toxic effect of heavy metals on dermatophytes

For determining the toxic effect of heavy metals on dermatophytes, eight heavy metals were tested using colony diameter method. Cadmium showed high toxicity effects on isolated fungi at minimal inhibitory concentration of 27 μg ml^?1 for Trichophyton mentagrophytes and of 20 μg ml^?1 for Epidermophyton floccosum, while iron enhanced dermatophytic growth. Other heavy metals revealed variable effect on isolated fungi. Susceptibility of E. floccosum to the activity of tested metals was greater than those of T. mentagrophytes. In conclusion, cadmium and silver are regarded to be the effective metals to prevent the development of two isolated species of dermatophytes. Growth of fungi in the presence of iron was greater than control.     

In vitro activity of colistin as single agent and in combination with antifungals against filamentous fungi occurring in patients with cystic fibrosis

Because published reports indicate that the antibiotic colistin (COL) has antifungal properties, this study investigated the antifungal in vitro activity of COL as single agent and in combination with the antifungal compounds voriconazole (VRC), caspofungin (CAS) and amphotericin B (AMB) against Scedosporium/Pseudallescheria spp., Exophiala dermatitidis and Geosmithia argillacea. In total, susceptibility was determined for 77 Scedosporium/Pseudallescheria spp., 82 E. dermatitidis and 17 G. argillacea isolates. The minimal inhibitory concentrations (MICs) of COL and the antifungals as single compound and in combination were determined with MIC test strips. Drug interactions were detected by crossing the MIC test strips at a 90º angle. The fractional inhibitory concentration index was used to categorise the drugs’ interaction. The MIC₅₀ value of COL was 12 μg ml^?1 for S. prolificans, 16 μg ml^?1 for P. apiosperma, 16 μg ml^?1 for P. boydii, 12 μg ml^?1 for E. dermatiditis and 6 μg ml^?1 for G. argillacea. VRC was the most active drug in combination without any antagonism with the exception of few P. boydii isolates. COL as single agent and in most combinations with antifungals exhibits in vitro antifungal activity against filamentous ascomycetes occurring in cystic fibrosis patients and may offer a novel therapeutic option, especially for multidrug‐resistant S. prolificans.     

Different Kinetic of Enzymatic Inactivation of Lincomycin and Clindamycin in Staphylococcus aureus

Summary

Lincosamide inactivation nucleotidylation (Lin) enzyme determined by the pBI109PGL plasmid of Staphylococcus epidermidis exhibits high level resistance to lincomycin but sensitivity to clindamycin by standard susceptibility methods. Substrate profile determination showed clindamycin to be a better substrate for the enzyme than lincomycin. In cultures of the plasmid-harboring strain, the level of clindamycin decreased below the inhibitory concentration in the first 4 hours of incubation but the level of lincomycin persisted longer. The initial extended inhibitory effect of clindamycin is due to better membrane penetrating ability, resulting in a higher intracellular concentration than that of lincomycin. Moreover, energy-dependent reduction in clindamycin uptake, probably due to active efflux of clindamycin but not of lincomycin, was observed. A therapeutic effect of clindamycin is not expected in infections caused by Lin-producer strains because the bacteriostatic effect of the drug is rapidly eliminated after administration.     

New insights on the antibacterial efficacy of miconazole in vitro

Miconazole is a broad‐spectrum antifungal used in topical preparations. In the present investigation the minimal inhibitory concentration (MIC) of miconazole for eighty wild type strains of gram‐positive and gram‐negative bacteria isolated from infected skin lesions was assessed using a modified agar dilution test (adapted to CLSI, Clinical Laboratory Standards Institute). 14 ATCC reference strains served as controls. Miconazole was found efficacious against gram‐positive aerobic bacteria (n=62 species), the MICs against Staphylococcus (S.) aureus, S. spp., Streptococcus spp. und Enterococcus spp. ranged between 0.78 and 6.25 μg/mL. Interestingly, there were no differences in susceptibility between methicillin‐susceptible (MSSA, 3) methicillin‐resistant (MRSA, 6) and fusidic acid‐resistant (FRSA, 2) S. aureus isolates. Strains of Streptococcus pyogenes (A‐streptococci) (8) were found to be slightly more sensitive (0.78‐1.563 μg/mL), while for gram‐negative bacteria, no efficacy was found within the concentrations tested (MIC >200 μg/mL). In conclusion, for the gram‐positive aerobic bacteria the MICs of miconazole were found within a range which is much lower than the concentration of miconazole used in topical preparations (2%). Thus topically applied miconazole might be a therapeutic option in skin infections especially caused by gram‐positive bacteria even by those strains which are resistant to antibiotics.     

Identification and characterisation of human pathogenic filamentous fungi and susceptibility to Thymus schimperi essential oil

Twenty‐eight clinical fungal isolates were characterised by morphological (macro‐ and micro‐features and growth response at 25, 30 and 37 °C) and molecular (nuclear rDNA‐internal transcriber spacer, calmodulin, cytochrome c oxidase 1 and the largest subunit of RNA polymerase II) analyses. The clinical fungal isolates were ascribed to the following taxa: Penicillium chrysogenum, Verticillium sp., Aspergillus tubingensis, Aspergillus minutus, Beauveria bassiana and Microsporum gypseum. In addition, in vitro susceptibility testing of the isolates to conventional antifungal agents and to two chemically well‐defined chemotypes of Thymus schimperi essential oil was performed. Most of the isolates were resistant to amphotericin B (except A. minutus), and itraconazole, while terbinafine was quite active on these fungi. T. schimperi essential oil showed antifungal activity against all of the tested fungal isolates with minimal inhibitory concentration values similar or lower than those of terbinafine. Transmission electron microscopy analyses revealed that fungal growth inhibition by essential oil was accompanied by marked morphological and cytological changes.     

Daptomycin Morphostructural Damage in Bacillus cereus Visualized by Atomic Force Microscopy

Abstract

Daptomycin is a novel, rapidly bactericidal in vitro antibiotic that is under investigation for the treatment of serious Gram-positive infections. Although daptomycin appears to disrupt membrane function, the precise mechanism of action has not been fully elucidated. Atomic force microscopy (AFM) is an innovative technique that allows high-resolution visualization and digital image manipulation of cell surface structures in 3 dimensions without the use of photons and electrons. The aim of this study was to use AFM to investigate the morphostructural changes in Bacillus cereus that occur upon daptomycin administration. The effects of daptomycin at 4x and 8x the minimal inhibitory concentration were visualized during an 8-hour incubation period. Atomic force microscopy images showed aberrant bacterial surface formations, including flattening and shrinking of cells and leakage of cytoplasm through the membrane. In addition to structural changes, the destabilization of flagella was also observed. These results support previous data suggesting that daptomycin disrupts membrane function.     

In vitro effect of subminimal inhibitory concentrations of antibiotics on the biofilm formation ability of Acinetobacter baumannii clinical isolates

The ability of A cinetobacter baumannii strains to form biofilm is one of the most important virulence factor which enables bacterial survival in a harsh environment and decreases antibiotic concentration as well. Subminimal inhibitory concentrations (subMICs) of antibiotics may change bacterial ultrastructure or have an influence on some different molecular mechanisms resulting in morphological or physiological changes in bacteria itself. The aim of this study was to determine effects of 1/2, 1/4, 1/8 and 1/16 minimal inhibitory concentrationsof imipenem, ampicillin-sulbactam, azithromycin, rifampicin and colistin on biofilm formation ability of 22 biofilm non-producing and 46 biofilm producing A. baumannii strains (30 weak producing strains and 16 moderate producing strains). Results of this study indicate that 1/2–1/16 MICs of imipenem, azithromycin, and rifampicin can reduce bacterial biofilm formation ability in moderate producing strains (p < 0.05), whereas 1/16 MIC of imipenem and 1/4–1/8 MICs of rifampicin reduce the biofilm formation in weak producing strains (p < 0.05). Statisticaly significant effect was detected among biofilm non-producing strains after their exposure to 1/16 MIC of azithromycin (p = 0.039). SubMICs of ampicillin-sulbactam and colistin did not have any significant effect on biofilm formation among tested A. baumannii strains.     

Comparison of teicoplanin and vancomycin in vitro activity on clinical isolates of Staphylococcus aureus

Abstract

Ninety-one clinical isolates of Staphylococcus aureus have been tested with the Kirby Bauer and the Etest® method to determine the susceptibility to glycopeptides in the 2007–2010 period. Five strains (5·5%) were resistant to vancomycin and nine (9·9%) to teicoplanin. Teicoplanin showed a median minimal inhibitory concentration (MIC) of 1 mg/l (range 0·125–24 mg/l), an MIC50 of 1 mg/l, and an MIC90 of 2 mg/l; vancomycin had a median MIC of 1·5 mg/l (range 0·38–4 mg/l), an MIC50 of 1·5 mg/l, and an MIC90 of 2 mg/l. More isolates were distributed on higher values of MIC for vancomycin. Inhibition halos induced by vancomycin-impregnated paper diskettes were slightly larger than those by teicoplanin. Glycopeptide resistance among methicillin-resistant Staphylococcus aureus in Italy is an underestimated phenomenon, possibly due to the described underestimation of glycopeptides MICs by the automatic broth microdilution method, when compared to agar MIC assays. A teicoplanin MIC creep, as reported for vancomycin, cannot be assumed.     

Maternal carriage of extended-spectrum beta-lactamase-producing Escherichia coli isolates in Argentina

Abstract

The aim of this study was to determine the prevalence of vaginal Escherichia coli colonization and perianal carriage of Enterobacteriaceae resistant to third generation cephalosporins in pregnant women. Vaginal and perianal samples from 259 pregnant women were studied. Vaginal swabs were inoculated onto MacConkey agar plates and perianal swabs were inoculated onto CHROMagar extended-spectrum beta-lactamase (ESBL) plates. The minimal inhibitory concentration of the isolates was determined using the Epsilometer test method. The phenotypic detection of ESBLs was performed by the combined disc method using cefotaxime versus cefotaxime plus clavulanate. The prevalence of vaginal E. coli colonization during pregnancy was 14·3%. The resistance rate to ampicillin, gentamicin, and cefotaxime was 48·6, 10·8, and 0·8%, respectively. Enterobacteriaceae resistant to third generation cephalosporins were recovered in 7·3% of all perianal specimens. Among them, 5·4% of pregnant women were colonized with E. coli ESBL-producer strains. The present study revealed that colonization with Enterobacteriaceae resistant to third generation cephalosporins is significant in pregnancy. ESBL-producing E. coli were the most prevalent organisms. Screening strategies designed to monitor for ESBL-producing E. coli could be useful in endemic areas to prevent perinatal transmission and the introduction of multiresistant strains to the maternity ward.     

In- Vitro Activity of Ciprofloxacin and Sixteen Other Antimicrobial Agents against Blood Culture Isolates

Summary

The in-vitro antibacterial activities of seventeen antimicrobial agents including ampicillin, amikacin, Augmentin, aztreonam, cefazolin, cefuroxime, cefotaxime, ceftizoxime, ceftriaxone, ciprofloxacin, cloxacillin, erythromycin, gentamicin, penicillin G, piperacillin and vancomycin were compared against 100 Gram-negative and Gram-positive strains isolated from blood culture specimens received at the King Abdulaziz University Hospital (KAUH), in Jeddah, Saudi Arabia.

The antibacterial susceptibility was determined by the minimal inhibitory concentration (MIC), using an agar dilution method. Ciprofloxacin exhibited the greatest activity, inhibiting 90% of the tested strains (MIC₉₀) at a concentration ranging from < 0.015-0.5 mg/L. Against cloxacillin resistant or susceptible strains of Staphylococcus aureus and coagulase-negative staphylococci, ciprofloxacin had similar activity with MIC₉₀, of 0.2 mg/L. Salmonella typhi and salmonella species which were resistant to ampicillin and augmentin remained sensitive to ciprofloxacin (Mid₉₀ < 0.015-0.125) mg/L.). Against gentamicin sensitive and resistant Pseudomonas aeruginosa and Pseudomonas species, ciprofloxacin MIC₉₀ was 0.5 and 1 mg/L respectively. Aminoglycosides, third generation cephalosporins, aztreonam and antipseudomonal penicillins, on the other hand, showed high MIC₉₀ well above the obtainable serum concentrations against Enterobacteriaceae and Pseudomonas species.     

Bactericidal Activity of Pistacia lentiscus Mastic Gum Against Helicobacter pylori

Abstract

In this study we evaluated the antibacterial activity of mastic gum, a resin obtained from the Pistacia lentiscus tree, against clinical isolates of Helicobacter pylori. The minimal bactericidal concentrations (MBCs) were obtained by a microdilution assay. Mastic gum killed 50% of the strains tested at a concentration of 125 μg/ml and 90% at a concentration of 500 μg/ml. The influence of sub-MBCs of mastic gum on the morphologies of H. pylori was evaluated by transmission electron microscopy. The lentiscus resin induced blebbing, morphological abnormalities and cellular fragmentation in H. pylori cells.     

Comparative In- Vitro Activity of Fourteen Antibiotics Against Clinical Isolates of Enterococci

Summary

The in-vitto antibacterial activities of fourteen antimicrobial agents, including ampicillin, amikacin, Augmentin, ceftazidime, cefotaxime, ceftriaxone, ciprofloxacin, erythromycin, gentamicin, penicillin G, piperacillin, rifampicin, streptomycin and vancomycin, were compared against 195 enterococcal strains isolated from clinical specimens received at the King Abdulaziz University Hospital in Saudi Arabia. The antibacterial susceptibility was determined by the minimal inhibitory concentration (MIC) using an agar dilution method. Ampicillin, Augmentin and vancomycin exhibited the greatest activity, inhibiting 90% of the tested strains (MIC90) at 2 μg/ml, followed by penicillin G and piperacillin with MIC90 of 4 μg/ml. Erythromycin, third generation cephalosporins, aminoglycosides and rifampicin, on the other hand, had poor activity against enterococci with MIC90s well above the obtainable serum concentrations. The clinical implications of resistance to aminoglycosides and the alternative antimicrobial therapy in serious entrococcal infections are discussed in the text.