Accuracy of antibiotyping using standard antibiograms compared with 16S-23S ribosomal spacer PCR for diagnosis of MRSA.
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Austria↗
Biomedical subjects
A M Hirschl
Publications and source records attributed to A M Hirschl.
In vitro activity of fosfomycin alone and in combination with amoxicillin, clarithromycin and metronidazole against Helicobacter pylori compared with combined clarithromycin and metronidazole.
In order to evaluate the suitability of fosfomycin in combination with other agents for the treatment of Helicobacter pylori infections, the susceptibility profiles of 65 H. pylori strains were determined against multiple antimicrobial agents and combinations thereof using the agar dilution method. For fosfomycin alone, the range of minimum inhibitory concentration (MIC) results and the MICs at which 50% and 90% of strains were inhibited were 0.5-32 microg/ml and 2 and 4 microg/ml, respectively. For the combination of fosfomycin with amoxicillin, clarithromycin or metronidazole, the means calculated for the minimum and maximum fractional inhibitory concentration index were 0.70-1.17 and 1.15-2.03, respectively, suggesting partial synergy or indifference in the majority of strains. The combination of clarithromycin and metronidazole showed synergistic activity against 14 of 28 H. pylori strains tested. The in vitro activity results suggest the combination of fosfomycin with either amoxicillin or clarithromycin may be a promising alternative for the treatment of H. pylori infection. However, the clinical efficacy of these regimens remains to be investigated.
Amoxicillin↗
Non-invasive Helicobacter pylori diagnosis: stool or breath tests?
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Antigens, Bacterial↗
Viridans streptococci in endocarditis and neutropenic sepsis: biofilm formation and effects of antibiotics.
OBJECTIVES: Viridans group streptococci (VGS) are a frequent cause of bacterial endocarditis or sepsis in patients with neutropenia. Endocarditis in particular, is associated with plaque formation on the endocardium and valve leaflets whereas VGS septicaemia in neutropenic patients is caused by the influx of oral flora bacteria through mucositic lesions. This study examined the in vitro potency for biofilm formation of clinical VGS bloodstream isolates, and the effects of antibiotics on these biofilms. METHODS: During the years 1998-2000, 40 VGS bloodstream isolates from 18 patients with endocarditis and 22 patients with severe sepsis and neutropenia were collected. The MICs of penicillin, teicoplanin and moxifloxacin were determined using the microdilution broth method according to NCCLS criteria. Biofilms were grown in microtitre plates, dyed with Crystal Violet, and the mean optical density (OD) was used for quantification. Biofilms were incubated with penicillin, teicoplanin and moxifloxacin at various concentrations starting with the MICs for the respective isolates tested. RESULTS: Isolates from eight out of 18 patients with endocarditis and six out of 22 patients with neutropenia formed biofilms (not significant). For the 14 isolates, the MIC(90)s (range) of penicillin, teicoplanin and moxifloxacin were 0.5 mg/L (0.001-0.5), 0.125 mg/L (0.025-0.125) and 0.5 mg/L (0.05-0.5), respectively. Generally, biofilms persisted although incubated with the antibiotics up to concentrations of 128 x MIC. However, the ODs of biofilms after incubation with an antibiotic were significantly lower than the ODs of biofilms without antibiotic (P<0.05). A significant decrease in the biofilms with increasing antibiotic concentrations was observed for teicoplanin and moxifloxacin, but not for penicillin G. CONCLUSIONS: VGS isolated from patients with endocarditis and patients with sepsis and neutropenia form biofilms. Biofilms persist even when exposed to antibiotics at concentrations up to 128 x MIC. Nevertheless, teicoplanin and moxifloxacin reduced the density of the biofilms at concentrations >/=16 x MIC. Thus, testing the effects of antibiotics on biofilms may supply useful information in addition to standard in vitro testing, particularly in diseases where biofilm formation is involved in the pathogenesis.
Adolescent↗
Resistance of gram-negative non-fermentative bacilli causing bloodstream infection, Vienna, 1996-2003.
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Acinetobacter↗
Helicobacter pylori in children and adolescents: increase of primary clarithromycin resistance, 1997-2000.
BACKGROUND: The authors evaluate the prevalence of Helicobacter pylori resistance in 117 children and demonstrate the changes over a 4-year period. METHODS: In 117 children and adolescents, H. pylori-positive gastritis was revealed by diagnostic upper endoscopy. Biopsies from the antrum and body of the stomach were tested by histology, urease test, and culture. H. pylori was isolated using standard culture techniques, and susceptibility to amoxicillin, clarithromycin, and metronidazole was tested using the E-test (AB-Biodisk, Sweden). RESULTS: Endoscopy revealed gastric ulcers in 2 of 117 subjects, duodenal ulcers in 6 of 117, and erosive gastritis or duodenitis in 23 of 117. Almost all patients showed antral nodularity. Histology always showed chronic gastritis with different degrees of activity. During the 4-year study period, the authors noticed an increase of primary clarithromycin-resistant H. pylori strains, from 14.3% to 27.6% (mean, 20.3%). Metronidazole resistance varied between 5% and 25%. No resistance to amoxicillin was found. CONCLUSION: Eradication of H. pylori should take place only after testing of susceptibility. The general use of clarithromycin in children should be restricted to better-defined indications. Resistance to clarithromycin of H. pylori may also become a future problem for the treatment of adults.
Adolescent↗
Antimicrobial susceptibility profiles of clinically relevant blood culture isolates from nine surgical intensive care units, 1996-2000.
In order to elucidate trends in the incidence and susceptibility profiles of causative agents of bacteremia/fungemia in nine surgical intensive care units, a total of 744 isolates obtained during a 5-year period (1996-2000) were studied. The isolates included 698 bacteria and 46 fungi obtained from 523 positive blood cultures, representing 317 episodes of bacteremia/fungemia. Methicillin-resistant Staphylococcus aureus accounted for 2.3 episodes per 1000 surgical ICU admissions in 1996, 1.6 in 1997, 0.3 in 1998, 0.6 in 1999, and 1.7 in 2000. One Enterococcus faecalis (VanA) isolate resistant to both vancomycin and teicoplanin was recovered in 1996. Ciprofloxacin resistance in Pseudomonas aeruginosa decreased from 36% in 1996 to 20% in 2000, and resistance to third-generation cephalosporins decreased from 40% in 1996 to 9% in 2000. In light of differences between these results and those found elsewhere, these findings might prove useful for making infection control policy decisions in intensive care units.
Anti-Bacterial Agents↗
[Helicobacter pylori: virulence factors, resistance and diagnosis].
Helicobacter pylori disposes of various virulence factors such as urease, vacuolating cytotoxin and the cag-pathogenicity island which--though not alone, but possibly in conjunction with host-specific factors--may explain the varying course of the infection (asymptomatic, dyspepsia, ulcer, distal gastric carcinoma). Increasing resistance to macrolide antibiotics and the lack of new therapeutic approaches makes treatment of the infection increasingly difficult. The resultant call for a strict indication for treatment is in obvious contrast to the finding that Helicobacter pylori represents the major risk factor for gastric carcinoma and eradication would therefore be absolutely desirable. Increased use of culture and susceptibility testing would be desirable for the purpose of therapy optimization but also for reasons of resistance epidemiology. The indication for diagnostic screening should be guided by the treatment indications as proposed by the guidelines of the Maastricht Consensus Conference 2-2000. In addition--and regardless of clinical picture--therapeutic follow-up primarily relying on non-invasive tests (13C urea breath test, stool antigen test) should be a matter of course.
Drug Resistance, Multiple↗
Impact of bacteria in dairy products and of the intestinal microflora on the genotoxic and carcinogenic effects of heterocyclic aromatic amines.
This article gives a short overview on the present state of knowledge of the effects of the intestinal microflora on the health hazards of heterocyclic aromatic amines (HAs). Results of single cell gel electrophoresis assays with conventional, germ free and human flora associated rats indicate that the presence of intestinal microorganisms strongly enhances the induction of DNA-damage in colon and liver cells by IQ. Furthermore, it was found that supplementation of the feed with Lactobacilli attenuates the induction of colon cancer by this same amine. These recent findings suggest that the intestinal microflora and lactic acid bacilli in dairy products strongly affect the health risks of HAs. Nevertheless, most previous experiments with HAs focused on the involvement of mammalian enzymes in the biotransformation of these compounds and only a few articles are available which concern interactions of bacteria with HAs. Some of these studies suggested that the formation of directly mutagenic hydroxy-metabolites of the amines by fecal bacteria might be an important activation pathway but it turned out that the hydroxy-derivative of IQ is not genotoxic in mammalian cells and does not cause colon cancer in laboratory rodents. There is some evidence that hydrolysis of HA-metabolites by bacterial ss-glucuronidase might play a role in the activation of HAs but experimental data are scarce and no firm conclusions can be drawn at present. The most important detoxification mechanism appears to be the direct binding of the HAs to the cell walls of certain bacterial strains contained in fermented foods. It was shown that these effects do also take place under physiologically relevant conditions. Overall, it seems that intestinal bacteria play a key role in the activation and detoxification of HAs which has been an area of research long ignored. The elucidation of these mechanisms may enable the development of biomarkers for colon cancer risk and nutritional strategies of protection.
Amines↗
Urease prevents adherence of Helicobacter pylori to Kato III gastric epithelial cells.
The role of urease in Helicobacter pylori adherence to and internalization by Kato III cells was investigated. Kato III cells were incubated with wild-type strains (N6 or P1), with isogenic mutants lacking urease (N6ureB::TnKm or P1ureA::TnMax5) or producing the inactive apoprotein (N6ureG::TnKm), and with urease-positive clones recovered after complementation of N6ureB::TnKm with ureAB. Bacteria were stained with the green fluorescent dye PKH2, and the bacteria load of cells was analyzed by flow cytometry. With mutants lacking urease, the bacteria load was considerably increased, in comparison with the corresponding parental strains (P<.001). With clone K2(3), producing larger amounts of urease than N6, a significant reduction of bacteria load was observed, in comparison with the wild type (P<.001). N6ureG::TnKm showed adherence characteristics similar to those of N6. The role of urease in internalization was not clear. Thus, urease significantly inhibits H. pylori adherence to Kato III cells by a mechanism largely independent of enzymatic activity.
Bacterial Adhesion↗
Application of blood-based polymerase chain reaction for detection of Chlamydia pneumoniae in acute respiratory tract infections.
The aim of this study was to investigate whether blood-based polymerase chain reaction could serve as a diagnostic tool to identify individuals with acute respiratory Chlamydia pneumoniae infection. Respiratory specimens and peripheral blood mononuclear cells of 58 patients were analyzed using nested polymerase chain reaction and cell culture. Fifteen patients were polymerase chain reaction-positive for Chlamydia pneumoniae. Nine patients were positive in only the respiratory specimen; two in both the respiratory and blood sample (time intervals between onset of symptoms and sample collection, 3-10 days and 3-4 weeks, respectively); and four in only the blood sample. Detection of Chlamydia pneumoniae DNA in peripheral blood mononuclear cells does not seem to be a suitable marker for acute respiratory Chlamydia pneumoniae infection.
Acute Disease↗
Dysregulation of monocyte oxidative burst in streptococcal endocarditis.
BACKGROUND: Streptococcal subacute endocarditis is characterized by low-grade systemic inflammation. Although structural cardiac defects are pivotal, phagocytic cells, i.e. monocytes and neutrophils, are involved in the induction and the course of bacterial endocarditis. Decreased production of reactive oxygen metabolites was described in long-lasting infections. We hypothesized that the oxidative burst of phagocytes induced by the infecting organism is defective in patients with streptococcal endocarditis. PATIENTS AND METHODS: The monocytes and neutrophils of 11 patients with streptococcal native valve endocarditis were challenged with the respective pathogens and two control streptococcal strains, and the oxidative burst was determined by fluorescence-activated cell sorter analysis. These experiments were done before any antibiotic therapy was administered, and repeated at least 12 months after recovery. Eight volunteers served as healthy controls. RESULTS: The monocyte response to the respective pathogens was decreased in the patient groups compared to the response to the control streptococci. After cure the monocyte response to the pathogens was not different to the response to the control strains. The monocyte response of the healthy volunteers did not show any differences between the patients' pathogens and the control strains. The neutrophil oxidative burst to the pathogens was similar to that to the control streptococci in both patient and the volunteer group. CONCLUSION: The decreased response of patient monocytes to the pathogens may contribute to the low-grade inflammatory response and to the course of streptococcal endocarditis.
Adult↗
Multicenter comparison trial of DNA extraction methods and PCR assays for detection of Chlamydia pneumoniae in endarterectomy specimens.
The reported rate of detection of Chlamydia pneumoniae DNA within atherosclerotic lesions by PCR varies between 0 and 100%. In this study, identical sets of coded experimental atheroma samples (n = 15) and spiked controls (n = 5) were analyzed by 16 test methods in nine centers by means of PCR. The positive controls were correctly identified to levels of 1, 0.1, and 0.01 inclusion bodies of C. pneumoniae/ml of tissue homogenate by 16 (100%), 11 (69%), and 3 (19%) of the test methods, respectively. Three out of 16 negative controls (19%) were rated positive. Positivity rates for atheroma samples varied between 0 and 60% for the different test methods, with the maximum concordant result for positivity being only 25% for one carotid artery sample. There was no consistent pattern of positive results among the various laboratories, and there was no correlation between the detection rates and the sensitivity of the assay used.
Arteriosclerosis↗
Purification of surface-associated urease from Helicobacter pylori.
Helicobacter pylori colonizes the human gastric mucosa and produces large amounts of urease. The enzyme was extracted from the bacteria by distilled water and purified by gel-permeation (Sephacryl S-300), anion-exchange chromatography (Mono Q) and a second gel-permeation (Superdex 200). Urease enzyme activity was detected with a spectrophotometic assay based on phenol red. The optimal pH for anion-exchange was 6.9. The recovery of urease was 55-75%, purity 93-98% and the overall protein recovery 0.8-1.4%. The urease in the final extract still had enzymatic activity and showed the typical subunits of Mr 66000 and Mr 30000 when subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
Blotting, Western↗
Isolation and continuous growth of Chlamydia pneumoniae from arterectomy specimens.
For the purpose of collecting Chlamydia pneumoniae strains of vascular origin that could be grown continuously in vitro, a cell culture system has been established. Using different types of vascular specimens obtained from 38 patients, Chlamydia pneumoniae could be isolated in three (7.9%) cases. The strains were obtained from specimens of the carotid artery, the femoral artery and an infrarenal aneurysm of the abdominal aorta of three male atherosclerosis patients. Thus, viable Chlamydia pneumoniae strains are also present in vascular regions other than those hitherto described.
Aged↗
Susceptibility testing of Candida species: comparison of NCCLS microdilution method with Fungitest.
Fungitest is a new commercially available and easy-to-perform breakpoint test system using six antifungal agents. We compared this test with a modified standard method described by the National Committee for Clinical Laboratory Standards (NCCLS). One hundred isolates of Candida species were tested with both methods. Based on the same breakpoints, the correlation of qualitative results between the reference method and Fungitest was high. Best results were obtained after incubation of Fungitest for 48 h. Overall agreement was high, an excellent correlation was given with amphotericin B and flucytosine (100% and 99%, respectively), whereas itraconazole showed only 86% concordance. When Fungitest was read after 24 h the agreement was lower ranging from 100% to 75%. Some of the breakpoints used with Fungitest differ from the breakpoints recommended by NCCLS, whereas others have not been elaborated by the NCCLS. The adaptation of Fungitest breakpoints to NCCLS and determination of further breakpoints have to be discussed before Fungitest can be recommended for routine use.
Amphotericin B↗
[Diagnosis of Helicobacter pylori infections].
Hardly any other bacterial infection can be diagnosed with a similar variety of non-invasive and invasive tests as infection with H. pylori. Efficacy and specificity of well-proven tests such as urease test in biopsy specimens, histology, culture, and 13C breath test have been uniformly evidenced in numerous studies. Novel tests include molecular microbiological procedures, providing new opportunities for rapid detection of virulence factors and resistance genes, as well as antigen detection in feces. Though some open questions still need to be clarified, the latter test will gain major importance in the future. With the availability of the breath test and antigen detection in stool the need for the use of serological tests has been reduced, all the more so as the majority of the available quick tests have been shown to be of inadequate reliability. Well defined indications for the treatment of H. pylori infections are a major prerequisite for a reasonable use of this diagnostic armory.
Biopsy↗
In vitro activities of linezolid alone and in combination with amoxicillin, clarithromycin, and metronidazole against Helicobacter pylori.
Linezolid was tested against 70 strains of Helicobacter pylori by the agar dilution method. The MIC range and MICs at which 50 and 90% of strains were inhibited were 8 to 64, 16, and 32 microgram/ml, respectively. With minimum and maximum fractional inhibitory concentration summation values of 0.31 and 2.50, respectively, the combination of linezolid with amoxicillin, clarithromycin, or metronidazole showed either partial synergy or indifference for the majority of strains.
Acetamides↗