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Biomedical subjects

N Lehn

Publications and source records attributed to N Lehn.

At least 19 recordsLinked to original sources
PubMed2003

Rapid and standardized detection of Chlamydia pneumoniae using LightCycler real-time fluorescence PCR.

In order to meet the need of many microbiological laboratories for a standardized system for detecting Chlamydia pneumoniae in respiratory specimens, a hybridization probe-based LightCycler (Roche Diagnostics, Germany) PCR assay was developed. The assay's analytical sensitivity and specificity were evaluated according to the recommendations of the Centers for Disease Control and Prevention (USA) and Laboratory Centre for Disease Control (Canada). Seventy-four bacterial species other than Chlamydia pneumoniae, including strains of Chlamydia trachomatis, Chlamydia psittaci, and Chlamydia pecorum, tested negative. Six of six representative Chlamydia pneumoniae strains tested positive. An analytical sensitivity of 1 inclusion forming unit per ml of bronchoalveolar lavage fluid, corresponding to 0.02 inclusion forming units per PCR reaction, was observed. The assay showed 100% specificity and sensitivity for Chlamydia pneumoniae when testing DNA preparations from 12 specimens of patients with known pulmonary Chlamydia pneumoniae infection and from 78 specimens of patients with respiratory tract disease of other origin. The newly developed LightCycler assay may contribute to the urgently needed standardization of laboratory diagnosis of Chlamydia pneumoniae.

Bacteriological Techniques↗
PubMed2002

[Diagnosis and therapy of necrotizing fasciitis].

Necrotizing fasciitis is a soft tissue infection with a lethality ranging up to 80%. Infection causes the activation of interleukin, tumor necrosis factor alpha, and gamma-interferon through a triggering mechanism. This results in a capillary thrombosis with necrosis of the fascia, cutis, and subcutis. The patient's history often reveals a triggering event in the form of a recent minimal trauma or operative procedure. In a fulminant necrotizing fasciitis, the development of sepsis with consecutive multiple-organ failure mainly determines the outcome of the disease. Diagnosis is made initially upon clinical findings with a rapid progression of the disease and confirmed later by histologic and microbiologic findings. Radical surgical debridement within the first 24 h with postoperative treatment in an intensive care unit represents the cornerstone of therapy. Between January 1992 and March 2001, we treated 15 patients with necrotizing fasciitis. Lethality was 33%. There was a significant correlation between risk factors (present in 86% of the patients) and morbidity. Diagnosis and therapy should be performed by an experienced surgeon. In this contribution, we discuss the most important criteria that lead to the diagnosis and the therapeutic consequences.

Adult↗
PubMed2002

Fluorescence in situ hybridization vs. epsilometer test for detection of clarithromycin-susceptible and clarithromycin-resistant Helicobacter pylori strains in gastric biopsies from children.

AIM: To compare the results of culture and epsilometer test with fluorescence in situ hybridization for the detection of Helicobacter pylori and the presence of clarithromycin-susceptible and clarithromycin-resistant strains in antral biopsies from children. METHODS: Antral biopsies from 149 unselected children were investigated prospectively; 15 had previously received anti-H. pylori therapy. H. pylori status was defined by histology, rapid urease test and 13C-urea breath test. Fluorescence in situ hybridization was applied on fresh tissue with probes specific for the clarithromycin-susceptible wild type and three clarithromycin-resistant mutants. Susceptibility to clarithromycin was tested by epsilometer test in two laboratories. RESULTS: Culture and fluorescence in situ hybridization gave negative results in all 66 H. pylori-negative children (specificity, 100%). Of 83 infected children, cultures were successful in 75 (90%), epsilometer test in 71 (86%) and fluorescence in situ hybridization in 77 (93%). Eleven children (13%) showed discrepant results between the applied methods, indicating mixed infection. Clarithromycin-resistant isolates were identified in 16 of 73 previously untreated children. CONCLUSIONS: Primary resistance to clarithromycin is common (22%) in H. pylori isolates from children living in Germany. Fluorescence in situ hybridization is an excellent, fast method for the detection of H. pylori and clarithromycin-resistant mutants in gastric biopsies. Multiple biopsies identify mixed infections, indicating that clarithromycin-resistant and clarithromycin- susceptible strains are not evenly distributed within the stomach.

Adolescent↗
PubMed2001

In vitro activity of linezolid against Gram-positive uropathogens of hospitalized patients with complicated urinary tract infections.

The antimicrobial activity of linezolid, a recently developed antibiotic agent active against Gram-positive bacteria, was tested against pathogens from three different collections. (1) Uropathogens from hospitalized urological patients (1990/1991) with complicated and/or hospital-acquired UTIs; Urologic Clinic, Hospital St. Elisabeth, Straubing. (2) Uropathogens from a multi-centre study (1995/1996) comprising 37 urological centres throughout Germany. (3) MRSA isolates of patients and staff (1999/2000) within the Hospital St. Elisabeth, Straubing. Genotyping of the latter isolates was performed by pulsed-field-electrophoresis. The minimal inhibitory concentrations (MIC) of linezolid determined by an agar (Isosensitest) dilution method using a multipoint inoculator and an inoculum of 10(4) cfu per point ranged for methicillin susceptible Staphylococcus aureus (MSSA) (n=27) between 2 and 4 mg/l, for methicillin resistant S. aureus (MRSA) (n=35) between 1 and 2 mg/l, for methicillin susceptible coagulase-negative staphylococci (CNS) (MSSE) (n=67) between 0.5 and 4 mg/l, for methicillin resistant CNS (MRSE) (n=19) between 0.25 and 2 mg/l, for Enterococcus. faecalis (n=184) between 0.5 and 4 mg/l, for E. faecium (n=3) 2 mg/l and for Streptococcus spp. (n=4) between 0.25 and 1 mg/l, indicating that all strains were susceptible. According to the in vitro activity, linezolid may be considered a promising antibacterial agent for the treatment of complicated UTI caused by Gram-positive uropathogens. Thus, linezolid should be evaluated in a clinical study.

Acetamides↗
PubMed2001

In vitro activities of six quinolones and mechanisms of resistance in Staphylococcus aureus and coagulase-negative staphylococci.

Of 94 clinical isolates of Staphylococcus aureus (n = 51) and coagulase-negative staphylococci (CNS) (n = 43), mutations in the quinolone resistance-determining region of topoisomerases GrlA, GrlB, GyrA, and GyrB together with MICs of six quinolones were analyzed. Amino acid substitutions at identical residues (GrlA residues 80 and 84; GyrA residues 84 and 88) were found in S. aureus and CNS. Active efflux, as suggested by blocking by reserpine, contributed substantially to the resistance phenotype in some strains. Among ciprofloxacin, clinafloxacin, levofloxacin, nalidixic acid, trovafloxacin, and sparfloxacin, a 0.5-microg/ml concentration of sparfloxacin discriminated best between strains with two or three mutations and those with no mutations.

4-Quinolones↗
PubMed2001

Tumor necrosis factor-dependent adhesions as a major protective mechanism early in septic peritonitis in mice.

The occurrence of peritoneal adhesions in surgical patients is positively correlated with tumor necrosis factor (TNF) levels. In a model of septic peritonitis-cecal ligation and puncture-TNF neutralization prevented formation of peritoneal adhesions and increased mortality, most likely because localization of the septic focus was prevented. To discriminate between the coagulation-independent protective TNF effect and a potential protective procoagulant TNF effect, formation of peritoneal adhesions after CLP was inhibited with heparin, hirudin, or urokinase. Each treatment increased mortality and increased the number of bacteria in the peritoneal lavage fluid, kidney, and liver to various degrees. Under these experimental conditions, antibiotics prevented death. In coagulation-compromised mice, lethality was further enhanced by additional TNF neutralization. These findings demonstrate that peritoneal adhesions early in septic peritonitis are an important mechanism of innate immunity that prevents increased spread of bacteria and reduces mortality.

Animals↗
PubMed2001

Frequency of rpoB mutations inside and outside the cluster I region in rifampin-resistant clinical Mycobacterium tuberculosis isolates.

The prevalence of recently described mutation V176F, located in the beginning of the rpoB gene and associated with rifampin resistance and the wild-type cluster I sequence, was determined by analyzing the distribution of rpoB mutations among 80 rifampin (RIF)-resistant Mycobacterium tuberculosis strains isolated in Germany during 1997. The most frequent rpoB mutations were changes in codon 456 (52 isolates, 65%), followed by changes in codon 441 (13 isolates, 16%) and codon 451 (11 isolates, 14%). The V176F mutation was detected in one isolate of the study population and in 5 of 18 RIF-resistant strains with no cluster I mutation from six previously published studies. In three isolates, a mixture of resistant and susceptible subpopulations (heteroresistance) prohibited the detection of rpoB mutations in the initial analysis; however, in these isolates, cluster I mutations could be verified after a passage on RIF-containing medium. IS6110 DNA fingerprinting of 76 strains revealed eight clusters comprising 27 strains with identical restriction fragment length polymorphism patterns that mainly also show identical rpoB mutations and identical or similar drug resistance patterns. In conclusion, our results indicate that the V176F mutation should be included in molecular tests for prediction of RIF resistance in M. tuberculosis. We further demonstrated that heteroresistance caused by a mixture of mycobacterial subpopulations with different susceptibilities to RIF may influence the sensitivity of molecular tests for detection of resistance.

Adult↗
PubMed2001

Evaluation of two commercial enzyme immunoassays, testing immunoglobulin G (IgG) and IgA responses, for diagnosis of Helicobacter pylori infection in children.

Serological testing to diagnose Helicobacter pylori infection in children is still controversial, although commonly used in clinical practice. We compared the immunoglobulin G (IgG) and IgA results of two commercially available enzyme immunoassays (EIAs) (Pyloriset IgG and IgA and Enzygnost II IgG and IgA) for 175 children with abdominal symptoms divided into three age groups (0 to < or =6 years, n = 47; >6 to < or =12 years, n = 77; >12 years, n = 51). A child was considered H. pylori infected if at least two of three tests (histology, rapid urease test, 13C-urea breath test) or culture were positive and noninfected if all results were concordantly negative. Of 175 children, 93 (53%) were H. pylori negative and 82 were H. pylori positive. With the recommended cutoff values, the overall specificity was excellent for all four EIAs (95.7 to 97.8%) regardless of age. Sensitivity varied markedly between tests and was 92.7, 70.7, 47.5, and 24.4% for Enzygnost II IgG, Pyloriset IgG, Enzygnost II IgA, and Pyloriset IgA, respectively. Sensitivity was low in the youngest age group (25 to 33.3%), except for Enzygnost II IgG (91.6%). Receiver-operating curve analyses revealed that lower cutoff values would improve the accuracy of all of the tests except Enzygnost II IgG. Measurement of specific IgA, in addition to IgG, antibodies hardly improved the sensitivity. The specificity of commercial serological tests is high in children when the cutoff values obtained from adults are used. In contrast, sensitivity is variable, with a strong age dependence in some, but not all, tests. We speculate that young children may have a different immune response to H. pylori, with preferable responses to certain antigens, as well as lower titers than adults. The Pyloriset test may fail to recognize these specific antibodies.

Adolescent↗
PubMed2001

Real-time PCR assay targeting IS481 of Bordetella pertussis and molecular basis for detecting Bordetella holmesii.

Detection of Bordetella holmesii by a real-time PCR assay targeting IS481 of Bordetella pertussis is reported. Sequencing of IS481-specific PCR products from B. pertussis and B. holmesii isolates revealed sequence homology. Restriction fragment length polymorphism demonstrated a low copy number of IS481-like sequences in B. holmesii. These results, and culture of B. holmesii from patients with cough, suggest that the specificity and predictive value of IS481-based PCR assays for pertussis may be compromised.

Bordetella↗
PubMed2000

The Helicobacter pylori vacA s1, m1 genotype and cagA is associated with gastric carcinoma in Germany.

BACKGROUND: The H. pylori vacuolating cytotoxin encoded by vacA and the cytotoxin-associated protein encoded by cagA are considered to be important virulence determinants that have been implicated in the development of peptic ulcers and gastric carcinoma. However, conflicting results regarding the association between these virulence factors and clinical disease have been reported from different geographic regions. AIMS: To determine the frequency of vacA genotypes, vacuolating cytotoxin activity, and cagA in H. pylori isolates obtained from patients with gastric cancer in Germany. METHODS: H. pylori isolates were obtained from 34 patients with gastric cancer and from 35 subjects with asymptomatic H. pylori gastritis. vacA genotypes and cagA were identified by PCR. Cytotoxic activity was determined by HeLa cell assays. Gastritis was assessed according to the updated Sydney System. RESULTS: The H. pylori vacA s1,m1 genotype was significantly more frequent in patients with gastric cancer (24/34, 70.6%) as compared with controls (12/35, 34. 3%) (p = 0.005). Cytotoxic activity was detected in 24 (70.6%) and 15 (42.9%) H. pylori isolates from gastric cancer patients and controls, respectively (p = 0.03). The cagA gene was identified in 30 (88.2%) and 21 (60%) H. pylori isolates in the respective groups (p = 0.01). CONCLUSIONS: Our study suggests a significant association between the H. pylori vacA s1,m1 genotype, cytotoxic activity, cagA, and gastric cancer. Detection of H. pylori possessing these virulence determinants may help to identify patients being at an increased risk to develop gastric cancer in our population.

Adenocarcinoma↗
PubMed2000

[Effects of restrictions on use of vancomycin in a German university hospital].

BACKGROUND: Recently, increasing antibiotic resistance has been observed among gram-positive bacteria. However, only few isolates were found to be resistant against glycopeptides. Therefore, internationally accepted guidelines recommend a restricted use of vancomycin and other glycopeptide antibiotics in order to prevent the development of resistance against these clinically important antibiotics. In many countries, the hospital pharmacies play a key role in control and reinforcement of antibiotic formulary restrictions. In Germany, however, the hospital pharmacies usually do not take over such control functions, and most wards keep a stock of regularly used drugs including antibiotics, which makes reinforcement of restrictions difficult. METHODS: In an attempt to achieve a restriction of vancomycin use, the pharmacy of our university hospital was advised to deliver vancomycin to the wards only on request with a special order form signed by an attending, individually for every patient who should receive vancomycin. The efficacy of this restriction measure was evaluated in 3-month periods before and after the restriction became effective. RESULTS: Hospitalwide, this led to a 20.1% reduction of i.v. vancomycin and an 85.7% reduction of oral vancomycin use per 1000 patient days. If the hematology/oncology units were not considered, the reduction of i.v. vancomycin use was 41.8%, and the total use after the restriction 24.2 g per 1000 patient days. Microbiology results which justified the use of vancomycin decreased by 8.3% (10.9% hematology/oncology units not considered) between the 2 observation periods. Assuming a 7-day mean course of i.v. vancomycin therapy, the empirical use of i.v. vancomycin decreased from 39.9% to 8% after the restriction had been instituted. CONCLUSION: Allowing only experienced physicians (attendings) to decide on the use of vancomycin therapy, proved in our experience to be an effective measure to reduce unnecessary vancomycin use.

Drug Utilization↗
PubMed2000

Secondary resistance among 554 isolates of Helicobacter pylori after failure of therapy.

In a study to determine secondary resistance among Helicobacter pylori isolates, gastroenterologists from several German cities submitted over a 3-year period to centre A (Regensburg) or centre B (Freiburg) gastric biopsies from patients in whom one or more therapies to eradicate Helicobacter pylori had failed. Rates of resistance among the collections of 302 (centre A) and 252 (centre B) isolates were, respectively, as follows: to metronidazole, 75% and 66%; to clarithromycin, 58% and 49%; to amoxicillin, 0%; to ciprofloxacin, 9%; to doxycycline, 0%; and to rifampin, 0%. Resistance to clarithromycin was associated with metronidazole resistance in 89% and 85% of the isolates in centre A and centre B, respectively.

Amoxicillin↗
PubMed2000

Helicobacter heilmannii-associated primary gastric low-grade MALT lymphoma: complete remission after curing the infection.

BACKGROUND & AIMS: Cure of Helicobacter pylori infection may lead to complete remission of associated low-grade mucosa-associated lymphoid tissue (MALT) lymphoma in stage EI. This study investigated whether Helicobacter heilmannii infection-associated primary gastric MALT lymphoma will regress after cure of the infection. METHODS: H. heilmannii-induced gastritis was diagnosed histologically, by a new specific immunoglobulin G enzyme-linked immunosorbent assay, and with 16S ribosomal RNA amplification and sequencing in 5 consecutive patients with primary gastric MALT lymphoma clinical stage EI. Patients received 40 mg omeprazole and 750 mg amoxicillin 3 times per day for 14 days. Polymerase chain reaction (PCR) was used to detect rearrangement of immunoglobulin heavy-chain genes before treatment and during follow-up. RESULTS: Five patients (3 men, 2 women; mean age, 65 years; range, 42-79 years) were studied. H. pylori was not detected by culture, histology, serology, or PCR. Treatment resulted in the cure of H. heilmannii infection in each case and complete histological and endoscopic remission of the tumors. Three of 5 patients showed monoclonal B cells before treatment, 2 of whom remained PCR positive. Within a median follow-up period of 24 months, no relapse of the lymphoma or reinfection with H. heilmannii occurred. CONCLUSIONS: These data suggest that gastric MALT lymphoma may arise in patients with H. heilmannii infection. Cure of this infection may lead to complete remission of the MALT lymphoma.

Adult↗
PubMed2000

Influence of a prophylactic single dose of ciprofloxacin on the level of resistance of Escherichia coli to fluoroquinolones in urology.

During the years 1991-1996 an increase in fluoroquinolone-resistant Escherichia coli was observed at the Urological Department of the Municipal Hospital in Straubing, Germany. A prospective study was undertaken to investigate the influence of single-dose prophylaxis (SDP) using 500 mg ciprofloxacin orally on the level of resistance to ciprofloxacin of faecal E. coli. One hundred and five patients were recruited to the study: E. coli resistance to ciprofloxacin before prophylaxis was 3% (3/91) in contrast to 12% (5/42) after prophylaxis (P = 0.052). In 31 isolates no major change in the low MIC values before and after SDP was observed. PFGE showed clonal diversity in about half of the cases. Three isolates showed low-level resistance and three isolates high-level resistance to ciprofloxacin both before and after SDP. PFGE showed clonal identity in all cases. All patients had previously been treated with fluoroquinolones (FQ). In two isolates emergence of high-level resistance to ciprofloxacin after SDP occurred. PFGE showed clonal diversity in both cases. We conclude that after SDP with 500 mg ciprofloxacin there is a shift to gram-positive bacteria in the faeces and an increase in the rate of FQ resistance. Since selection of highly resistant E. coli is possible, a careful risk-benefit evaluation of prophylaxis with FQ is indicated.

Anti-Infective Agents↗
PubMed2000

Rifabutin-based triple therapy after failure of Helicobacter pylori eradication treatment: preliminary experience.

Despite continuous improvement of Helicobacter pylori (Hp) eradication therapy, new treatment regimens are necessary if established first-line treatments fail. In the present pilot study, a recently described rifabutin-based triple therapy was evaluated after preceding failure of triple therapy. Rifabutin (150 mg), amoxicillin (1 g), and lansoprazole (30 mg) were administered twice daily for 1 week to 25 patients infected with Hp who had previously failed to respond to eradication treatment and/or who had developed resistance to macrolides and nitroimidazoles. Four patients were lost to follow-up. Eradication rate of rifabutin-based triple therapy was 86% (18/21; per protocol) and 72% (18/25; intention-to-treat). Side effects were minimal. It is concluded that this new drug combination is an effective therapy for Hp strains resistant to clarithromycin or metronidazole; however, rifabutin-based treatment regimens for Hp eradication should be restricted to patients infected with resistant strains.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2000

Mutations in the beginning of the rpoB gene can induce resistance to rifamycins in both Helicobacter pylori and Mycobacterium tuberculosis.

A clinical isolate of Helicobacter pylori that developed resistance to rifabutin during therapy carried an rpoB gene that retained a wild-type cluster region sequence but had acquired a novel codon 149 (V149F) mutation. In transformation experiments, the mutation was shown to confer high-level rifabutin resistance. The equivalent mutation (V176F) was present in several resistant isolates of Mycobacterium tuberculosis.

Amino Acid Sequence↗