Sabine Schubert

Burkholderia Is Highly Resistant to Human Beta-Defensin 3

ABSTRACT The bactericidal activity of the novel beta-defensin hBD-3 against 28 species and 55 strains of gram-positive cocci and gram-negative fermentative and nonfermentative rods was tested. All strains proved to be highly or intermediately susceptible to hBD-3 (minimal bactericidal concentration [MBC], ≤50 μg/ml), except for Burkholderia cepacia, for all 23 tested strains of which MBCs were >100 μg/ml.

The expression of the β-defensins hBD-2 and hBD-3 is differentially regulated by NF-κB and MAPK/AP-1 pathways in an in vitro model of Candida esophagitis

BackgroundCandida albicans resides on epithelial surfaces as part of the physiological microflora. However, under certain conditions it may cause life-threatening infections like Candida sepsis. Human β-defensins (hBDs) are critical components of host defense at mucosal surfaces and we have recently shown that hBD-2 and hBD-3 are upregulated in Candida esophagitis. We therefore studied the role of Candida te signalling pathways in order to understand the mechanisms involved in regulation of hBD-expression by C. albicans. We used the esophageal cell line OE21 and analysed the role of paracrine signals from polymorphonuclear leukocytes (PMN) in an in vitro model of esophageal candidiasis.ResultsSupernatants of C. albicans or indirect coculture with C. albicans induces upregulation of hBD-2 and hBD-3 expression. PMNs strongly amplifies C. albicans- mediated induction of hBDs. By EMSA we demonstrate that C. albicans activates NF-κB and AP-1 in OE21 cells. Inhibition of these pathways revealed that hBD-2 expression is synergistically regulated by both NF-κB and AP-1. In contrast hBD-3 expression is independent of NF-κB and relies solely on an EGFR/MAPK/AP-1-dependent pathway.ConclusionOur analysis of signal transduction events demonstrate a functional interaction of epithelial cells with PMNs in response to Candida infection involving divergent signalling events that differentially govern hBD-2 and hBD-3 expression.

Penicillin compared with other advanced broad spectrum antibiotics regarding antibacterial activity against oral pathogens isolated from odontogenic abscesses

OBJECTIVES We examined the spectrum of oral pathogens found in odontogenic abscesses and their susceptibility to penicillin as well as to amoxicillin with clavulanic acid, doxycycline, clindamycin and moxifloxacin. The in vitro results were compared with clinical observations. PATIENTS AND METHODS One hundred and eighty eight swabs were obtained from 94 patients with odontogenic abscesses. Bacterial strains were isolated for susceptibility tests. The same patients were investigated for their clinical outcome after standard therapy. RESULTS A total of 517 bacterial strains were isolated from 94 patients. Ninety eight per cent of abscesses were polymicrobial. The most prevalent bacteria were Viridans streptococci representing 54% of the aerobic/facultative anaerobic bacteria. Prevotella spp. comprised 53% of the anaerobes. No multiresistant strains were detected. Susceptibility testing revealed a sensitivity of over 99% of aerobes/facultative aerobes and 96% of anaerobes sensitivity for moxifloxacin. The corresponding values for penicillin were lowest at 61% and 79%, respectively. In the clinical collective, patients with minor abscesses and no risk of further progression received surgical treatment without antibiotics (36%). Penicillin was administered additionally in 30%. Amoxicillin with clavulanic acid was given in 18% and clindamycin in 15%. Ninety two of the 94 patients showed significant recovery with the described treatment. Only in two cases was a change to the latest broader spectrum antibiotics necessary. CONCLUSION In contrast to the moderate in vitro results, penicillin successfully treated the pathogens derived from odontogenic abscess sufficiently when adequate surgical treatment was provided. One third of the patients was treated successfully with incision and drainage only. We suggest that one good reason for its clinical efficacy is the susceptibility of the dominant aerobe/facultative aerobe and anaerobe strains to penicillin.

Mouse Beta-Defensin-14, an Antimicrobial Ortholog of Human Beta-Defensin-3

ABSTRACT Searching the database for mouse homologs of the antimicrobial peptide human beta-defensin-3 (hBD-3) revealed highest identity (69%) to mouse beta-defensin-14 (mBD-14). Recombinant mBD-14 exhibited broad-spectrum, nanomolar microbicidal activity. Treatment of keratinocytes with gamma interferon or transforming growth factor alpha increased mBD-14 gene expression. These data suggest that mBD-14 is the functional ortholog of hBD-3.

Identification of RNase 8 as a Novel Human Antimicrobial Protein

ABSTRACT The antimicrobial activity of the human RNase A superfamily member RNase 8 was evaluated. Recombinant RNase 8 exhibited broad-spectrum microbicidal activity against potential pathogenic microorganisms (including multidrug-resistant strains) at micro- to nanomolar concentrations. Thus, RNase 8 was identified as a novel antimicrobial protein and may contribute to host defense.

Effect of pH on the in Vitro Activity of and Propensity for Emergence of Resistance to Fluoroquinolones, Macrolides, and a Ketolide

Antibiotic activity against common respiratory pathogens can be affected by the pH of the medium (in vitro) or the bodily fluid (in vivo) in which bacteria are present. The ionized fraction of an antibiotic is not able to efficiently penetrate bacterial or mammalian membranes, reducing the quantity of molecules able to exert their antibacterial effect resulting in elevated MIC values This study shows that the activity of macrolide antibiotics is particularly sensitive to acidic conditions, whereas a ketolide and fluoroquinolones are much less affected. Furthermore, induction of spontaneous and multistep macrolide resistance is greatly increased in acidic medium. In contrast, telithromycin and moxifloxacin did not induce resistance at any pH. Antibiotics which are less likely to induce resistance in vitro may also be less likely to induce the development of resistance in patients with respiratory tract infections.

Duration of Fecal Shedding of Shiga Toxin–Producing Escherichia coli O104:H4 in Patients Infected During the 2011 Outbreak in Germany: A Multicenter Study

BACKGROUND In May-July 2011, Germany experienced a large food-borne outbreak of Shiga toxin 2-producing Escherichia coli (STEC O104:H4) with 3842 cases, including 855 cases with hemolytic uremic syndrome (HUS) and 53 deaths. METHODS A multicenter study was initiated in 5 university hospitals to determine pathogen shedding duration. Diagnostics comprised culture on selective media, toxin enzyme-linked immunosorbent assay, and polymerase chain reaction. Results were correlated with clinical and epidemiologic findings. Testing for pathogen excretion was continued after discharge of the patient. RESULTS A total of 321 patients (104 male, 217 female) were included (median age, 40 years [range, 1-89 days]). Median delay from onset of symptoms to hospitalization was 4 days (range, 0-17 days). Two hundred nine patients presented with HUS. The estimate for the median duration of shedding was 17-18 days. Some patients remained STEC O104:H4 positive until the end of the observation time (maximum observed shedding duration: 157 days). There was no significant influence of sex on shedding duration. Patients presenting with HUS had a significantly shortened shedding duration (median, 13-14 days) compared to non-HUS patients (median, 33-34 days). Antimicrobial treatment was also significantly associated with reduced shedding duration. Children (age≤15 years) had longer shedding durations than adults (median, 35-41 vs 14-15 days). CONCLUSIONS STEC O104:H4 is usually eliminated from the human gut after 1 month, but may sometimes be excreted for several months. Proper follow-up of infected patients is important to avoid further pathogen spread.

Urinary Pharmacokinetics and Bactericidal Activity of Finafloxacin (200 and 800 mg) in Healthy Volunteers Receiving a Single Oral Dose

Background: Finafloxacin is a novel 8-cyano-fluoroquinolone under investigation for treatment of urinary tract infection. Methods: Urinary concentrations and urinary bactericidal titers (UBT) of finafloxacin 200- and 800-mg single doses in 6 healthy volunteers were measured up to 48 h. UBT were determined for a reference strain and 9 selected clinical uropathogens at the pH of native, acidified (pH 5.5) and alkalinized (pH 8.0) urine. Results: The mean maximum urine concentrations for 200 and 800 mg finafloxacin were 69.3 mg/l (0–2 h) and 150 mg/l (4–8 h). Median UBT were between 0 and 1:>2,048 and were in general agreement with minimal inhibitory concentrations of strains and urinary pH values. UBT in alkaline urine were significantly lower than those in native or acidic urine, except for Enterococcus faecalis.Conclusions: Finafloxacin exhibited significant bactericidal activity against susceptible uropathogens. The urinary bactericidal activity of finafloxacin was enhanced in acidic urine and significantly lower in alkaline urine.

Comparative in vitro activities of the novel antibacterial finafloxacin against selected Gram positive and Gram negative bacteria tested in Mueller-Hinton Broth and synthetic urine

ABSTRACT Kill kinetics and MICs of finafloxacin and ciprofloxacin against 34 strains with defined resistance mechanisms grown in cation-adjusted Mueller-Hinton broth (CAMHB) at pH values of 7.2 and 5.8 and in synthetic urine at pH 5.8 were determined. In general, finafloxacin gained activity at low pH values in CAMHB and remained almost unchanged in artificial urine. Ciprofloxacin MICs increased and bactericidal activity decreased strain dependently in acidic CAMHB and particularly in artificial urine.

IL-1β and ADAM17 are central regulators of β-defensin expression in Candida esophagitis

Candida albicans resides on epithelial surfaces as part of the physiological microflora. However, under certain conditions, it may cause life-threatening infections, including Candida sepsis. We have recently shown that human β-defensins (hBDs) hBD-2 and hBD-3 are upregulated in Candida esophagitis and that this antifungal host response is distinctly regulated by NF-κB and MAPK/activator protein-1 (AP-1) pathways. Here, we show that C. albicans induces hBD-2 through an autocrine IL-1β loop and that activation of the epidermal growth factor receptor (EGFR) by endogenous transforming growth factor-α (TGF-α) is a crucial event in the induction of hBD-3. To further dissect upstream signaling events, we investigated expression of the central sheddases for EGFR ligands ADAM10 and ADAM17 in the healthy and infected esophagus. Next, we used pharmaceutical inhibitors and small-interfering RNA-mediated knock down of ADAM10 and ADAM17 to reveal that ADAM17-induced shedding of TGF-α is a crucial step in the induction of hBD-3 expression in response to Candida infection. In conclusion, we describe for the first time an autocrine IL-1β loop responsible for the induction of hBD-2 expression and an ADAM17-TGF-α-EGFR-MAPK/AP-1 pathway leading to hBD-3 upregulation in the course of a Candida infection of the esophagus.