A multi-centre prospective evaluation of the Check-Direct ESBL Screen for BD MAX as a rapid molecular screening method for extended-spectrum beta-lactamase-producing Enterobacteriaceae rectal carriage.

OBJECTIVE: A multiplex extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) quantitative polymerase chain reaction (qPCR), performed directly on rectal swabs, was compared with a culture-based protocol to study the discrepancies between the two methods, and identify existing challenges to apply this assay in routine clinical practice. The secondary objective was to assess the performance of the qPCR. MATERIALS AND METHODS: In two Dutch teaching hospitals, 573 rectal swabs were collected prospectively. Culture with additional testing with the Check-MDR CT103XL (Check-Points) was compared with the Check-Direct ESBL Screen for BD MAX (Check-Points), which detects the presence of the ESBL gene families CTX-M1, CTX-M2, CTX-M9 and SHV2/5-ESBL. The culture-based protocol (with Brilliance agar) was considered as the gold standard to assess the performance of the qPCR. RESULTS: Of the 573 rectal swabs, 74 (12.9%) were culture-positive. Eighty-four (14.7%) were qPCR-positive. There were eight culture-positive/qPCR-negative discrepancies and 18 culture-negative/qPCR-positive discrepancies. Sensitivity and specificity of qPCR vs culture were 87.7% [95% confidence interval (CI) 79.7-95.7] and 96.3% (95% CI 94.6-98.0), respectively. CONCLUSION: The Check-Direct ESBL Screen for the BD MAX is an easy-to-perform, quick molecular diagnostic test with the potential to significantly speed up screening for rectal ESBL-E carriage. Discrepancies were observed between the culture-based protocol and the qPCR in 4.5% of tested samples. Existing challenges for implementing qPCR are its limited sensitivity, the need for thorough knowledge of the local ESBL-E genes, and interpretation of culture-negative but qPCR-positive samples. It is believed that the limited sensitivity of qPCR could be optimized by including blaTEM as a molecular target, and improving the limit of detection.

High levels of macrolide resistance-associated mutations in Mycoplasma genitalium warrant antibiotic susceptibility-guided treatment.

OBJECTIVES: Mycoplasma genitalium is a sexually transmitted pathogen, and infection with it is usually treated with macrolides. Unfortunately, emerging resistance to the macrolides has been associated with mutations in region V of the 23S rRNA gene. The aim of this retrospective study was to describe the incidence of macrolide resistance-associated mutations in M. genitalium from patients in the Netherlands. METHODS: All urogenital samples obtained from patients visiting a general practitioner or hospital in the east of the Netherlands that tested positive using the routine M. genitalium real-time PCR (February 2012-November 2014) were included. Following a PCR targeting the 23S rRNA gene, sequencing of the PCR fragments was performed to identify possible macrolide resistance-associated mutations. RESULTS: Forty-eight of the 153 samples (31.4%) included in this study contained a mutation in the 23S rRNA gene. This was reduced to 44/146 (30.1%) if only samples from unique patients were included. The predominant mutations identified were A2058G (16/44; 36.3%), A2059G (14/44; 31.8%) and a unique high proportion of A2058T (12/44; 27.3%). Treatment failure was observed in four patients initially infected with M. genitalium containing macrolide resistance-associated mutations, while in one of these patients subsequent treatment with moxifloxacin resulted in a microbiological cure. CONCLUSIONS: This study shows that macrolide resistance-associated mutations in M. genitalium occur with a high frequency. In contrast to studies from other regions, Dutch M. genitalium isolates carry the A2058T mutation at high frequency. Our data confirm the need for prospective detection of macrolide resistance-associated mutations prior to treating patients.

Recommendations for diagnosis and treatment of spondylodiscitis.

BACKGROUND: Spondylodiscitis, also known as vertebral osteomyelitis, is a destructive disease with high morbidity and mortality. Diagnosis is often delayed because of the rarity of the disease and the fact that early symptoms are often non-specific. There are currently no national guidelines on the diagnosis and treatment of spondylodiscitis in the Netherlands. METHODS: We performed a single-centre retrospective cohort study examining 49 patients over 18 years of age treated for spondylodiscitis in a six-year time period. RESULTS: Mean age of patients was 69 years (range 40-89). Most patients underwent an MRI scan to confirm diagnosis (n=30). In 39 patients a microorganism was found, most commonly Staphylococcus aureus (n=14), Streptococcus species (n=11) and Gram-negative bacteria (n=11). All patients were treated with antibiotics. Thirty-seven patients received antibiotic treatment for at least six weeks, while 17 patients were treated for 90 days or longer. In 13 patients no adequate treatment was started until culture results were available. Eleven patients underwent surgery after their diagnosis. Two patients had a recurrence. CONCLUSION: We recommend that, when considering spondylodiscitis as a possible diagnosis, all patients should undergo thorough physical examination, neurological screening, blood tests for infection and blood cultures. An MRI scan should be performed, followed by a PET-CT scan when results are inconclusive. Ideally a CT-guided biopsy is performed before treatment is started. Awaiting culture results all patients should receive broad-spectrum antibiotics. Targeting only Gram-positive microorganisms in empiric treatment will lead to a delay in adequate treatment in a substantial group of patients. A multidisciplinary approach is advocated.

New screening method to detect carriage of carbapenemase-producing Enterobacteriaceae in patients within 24 hours.

Rapid identification of patients colonized with carbapenemase-producing Enterobacteriaceae (CPE) is essential to prevent introduction and the spread of CPE in the hospital. This article presents the results of a new screening method to detect patients colonized with CPE within 24h after hospital admission. From high-risk patients rectal and throat swabs were collected and incubated overnight, after which DNA was isolated and tested for the most prevalent CPE genes (KPC, NDM, OXA-48, VIM and IMP) by a ligation-mediated real-time polymerase chain reaction. In 14 months 454 patients were screened; in six patients CPE were detected (carriage rate 1.3%).

Distribution of extended-spectrum beta-lactamase genes using a commercial DNA micro-array system.

Extended-spectrum beta-lactamase (ESBL) genes are distributed worldwide and their epidemiology is complex. Using the Check-ESBL assay, the distribution of class A ESBL genes in clinical isolates of aerobic Gram-negative bacilli from three laboratories in the East of The Netherlands was determined. Four patient categories were distinguished: (i) patients admitted to an intensive care unit (ICU); (ii) non-ICU inpatients; (iii) outpatients admitted less than a year before collection of the isolate, (<1); (iv) outpatients admitted more than one-year prior to isolate collection or who had never been hospitalized (>1). From February 2009 until March 2010, out of 491 putative ESBL-positive isolates detected by the Vitek2 or Phoenix automated sensitivity testing systems, ESBL genes were detected in 247 (50.3%) by the Check-ESBL assay. Of these, 116 were from hospitalized patients (35 ICU, 81 non-ICU) and 131 were from outpatients (43 <1, 88 >1). In all, 274 ESBL genes were identified in these 247 isolates: 153 CTX-M-1 group (predominantly in E. coli and K. pneumoniae, 70.4% and 51.6% respectively), 67 CTX-M-9 group (predominantly in E. cloacae, 57.9%), 32 SHV, 14 TEM and 8 CTX-M-2 group. ESBL-producing E. cloacae were significantly more common in hospitalized patients than in outpatients, 20.7% and 3.8% respectively (P=0.001). CTX-M-9 group ESBLs were significantly more prevalent in ICU patients (P=0.003), whereas SHV ESBLs were more common in hospitalized patients than in outpatients (P<0.001). There was no significant difference in distribution of ESBL genes between the two outpatient groups.

Rapid diagnostic testing of methicillin-resistant Staphylococcus aureus carriage at different anatomical sites: costs and benefits of less extensive screening regimens.

Multiple body site screening and pre-emptive isolation of patients at risk for methicillin-resistant Staphylococcus aureus (MRSA) carriage are considered essential for control of nosocomial spread. The relative importance of extranasal screening when using rapid diagnostic testing (RDT) is unknown. Using data from a multicentre study evaluating BD GeneOhm™ MRSA PCR (IDI), Xpert MRSA (GeneXpert) and chromogenic agar, added to conventional cultures, we determined cost-effectiveness assuming isolation measures would have been based on RDT results of different hypothetical screening regimes. Costs per isolation day avoided were calculated for regimes with single or less extensive multiple site RDT, regimes without conventional back-up cultures and when PCR would have been performed with pooling of swabs. Among 1764 patients at risk, MRSA prevalence was 3.3% (n = 59). In all scenarios the negative predictive value is above 98.4%. With back-up cultures of all sites as a reference, the costs per isolation day avoided were €15.19, €30.83 and €45.37 with 'nares only' screening using chromogenic agar, IDI and GeneXpert, respectively, as compared with €19.95, €95.77 and €125.43 per isolation day avoided when all body sites had been screened. Without back-up cultures costs per isolation day avoided using chromogenic agar would range from €9.24 to €76.18 when costs per false-negative RDT range from €5000 up to €50 000; costs for molecular screening methods would be higher in all scenarios evaluated. In conclusion, in a low endemic setting chromogenic agar screening added to multiple site conventional cultures is the most cost-effective MRSA screening strategy.

Comparison of two commercial molecular assays for simultaneous detection of respiratory viruses in clinical samples using two automatic electrophoresis detection systems.

Two molecular assays were compared with real-time RT-PCR and viral culture for simultaneous detection of common viruses from respiratory samples: a multiplex ligation-dependant probe amplification (MLPA) and a dual priming oligonucleotide system (DPO). In addition, the positive detections of MLPA and DPO were identified using two different automatic electrophoresis systems. A panel of 168 culture-positive and negative samples was tested by the molecular assays for the presence of influenza A and B virus, respiratory syncytial virus, human metapneumovirus, rhinovirus, coronaviruses, parainfluenza viruses and adenovirus. One hundred and twenty-nine (77%) samples were positive as detected by at least one method. Sixty-nine (41%) samples were positive by cell culture (excluding human metapneumovirus and coronaviruses), 116 (69%) by RT-PCR, 127 (76%) by MLPA and 100 (60%) by DPO. The MLPA yielded results in one attempt for all samples included while 12 (7.2%) samples had to be repeated by the DPO assay due to inconclusive results. The MLPA assay performed well in combination with either electrophoresis system, while the performance of the DPO assay was influenced by the electrophoresis systems. Both molecular assays are comparable with real-time RT-PCR, more sensitive than viral culture and can detect dual infections easily. Results can be obtained within 1 day.

Rapid screening of methicillin-resistant Staphylococcus aureus using PCR and chromogenic agar: a prospective study to evaluate costs and effects.

Pre-emptive isolation of suspected methicillin-resistant Staphylococcus aureus (MRSA) carriers is considered essential for controlling the spread of MRSA, but noncolonized patients will be isolated unnecessarily as a result of a delay in diagnosis of 3-5 days with conventional cultures. We determined costs per isolation day avoided, and incremental costs of rapid MRSA screening tests when added to conventional screening, but with decisions on isolation measures based on PCR results. A prospective multicentre study evaluating BD GeneOhm MRSA PCR (`IDI') (BD Diagnostics, San Diego, CA, USA), Xpert MRSA (`GeneXpert') (Cepheid, Sunnyvale, CA, USA) and chromogenic agar (MRSA-ID) (bioMérieux, Marcy-l'Etoile, France) was performed in 14 Dutch hospitals. Among 1764 patients at risk, MRSA prevalence was 3.3% (n=59). Duration of isolation was 19.7 and 16.1 h with IDI and GeneXpert, respectively, and would have been 30.0 and 76.2 h when based on chromogenic agar and conventional cultures, respectively. Negative predictive values (at a patient level) were 99.5%, 99.1% and 99.5% for IDI, GeneXpert and chromogenic agar, respectively. Numbers of isolation days were reduced by 60% and 47% with PCR-based and chromogenic agar-based screening, respectively. The cost per test was €56.22 for IDI, €69.62 for GeneXpert and €2.08 for chromogenic agar, and additional costs per extra isolation day were €26.34. Costs per isolation day avoided were €95.77 (IDI) and €125.43 (GeneXpert). PCR-based decision-making added €153.64 (IDI) and €193.84 (GeneXpert) per patient to overall costs and chromogenic testing would have saved €30.79 per patient. Rapid diagnostic testing safely reduces the number of unnecessary isolation days, but only chromogenic screening, and not PCR-based screening, can be considered as cost saving.

Prevalence, characterisation and clinical profiles of Shiga toxin-producing Escherichia coli in The Netherlands.

Detection of Shiga toxin-producing Escherichia coli (STEC) in The Netherlands is traditionally limited to serogroup O157. To assess the relative importance of STEC, including non-O157 serogroups, stool samples submitted nationwide for investigation of enteric pathogens or diarrhoea were screened with real-time PCR for the presence of the Shiga toxin genes. Patients were selected if their stool contained blood upon macroscopic examination, if they had a history of bloody diarrhoea, were diagnosed with haemolytic uraemic syndrome, or were aged <6 years (irrespective of the bloody aspect of the stool). PCR-positive stools were forwarded to a central laboratory for STEC isolation and typing. In total, 4069 stools were examined, with 68 (1.7%) positive PCR results. The highest prevalence was for stools containing macroscopic blood (3.5%), followed by stools from patients with a history of bloody diarrhoea (2.4%). Among young children, the prevalence (1.0%) was not significantly higher than among random, non-bloody, stool samples from diarrhoeal patients (1.4%). STEC strains were isolated from 25 (38%) PCR-positive stools. Eleven O-serogroups were detected, including five STEC O157 strains. As serogroup O157 represented only 20% of the STEC isolates, laboratories should be encouraged to use techniques enabling them to detect non-O157 serogroups, in parallel with culture, for isolation and subsequent characterisation of STEC strains for public health surveillance and detection of outbreaks.

Community-acquired pneumonia caused by Legionella longbeachae in an immunocompetent patient.

Reported here is the case of a previously healthy 67-year-old man who was admitted to the intensive care unit with pneumonia caused by Legionella longbeachae. The organism was identified in sputum and serum by 16S rRNA-based PCR assay and sequence-based typing. One acute serum sample produced a single elevated IgM antibody titer of 1:512 against non-pneumophila Legionella spp. The patient fully recovered following the initiation of appropriate antibiotic treatment. Since most current laboratory tests for Legionella spp. cannot detect infections caused by non-pneumophila Legionella spp., culture on Legionella-selective media or PCR should be considered when diagnosing severe pneumonia of unknown etiology.

Dyspepsia management in primary care.

BACKGROUND: Dyspepsia is common in western society. Prompt endoscopy is imperative in all patients with sinister symptoms or if symptoms first appear after the age of 50-55 years, but the optimal management of younger patients with uncomplicated dyspepsia is still open to debate. METHODS: The literature on the management of uncomplicated dyspepsia is reviewed and a personal view is presented. RESULTS: Strategies based on non-invasive detection of Helicobacter pylori are probably the most cost-effective. Currently (H. pylori prevalence 30%-40%), a 'test and treat' approach using a non-invasive test to detect H. pylori is likely to be the most efficient first step. If the patient is H. pylori-negative or if symptoms persist after successful H. pylori eradication, empirical treatment with an anti-secretory drug is justified. Endoscopy is reserved for those patients in whom this approach fails. If the prevalence of H. pylori decreases, the positive predictive value of any non-invasive H. pylori test will become too low. A 'test and scope' approach in which a positive test can be confirmed by two or more biopsy-based tests is then more appropriate. At a very low prevalence of H. pylori in the dyspeptic population, non-invasive testing for H. pylori loses its significance and empirical treatment with an antisecretory drug becomes a rational first step. CONCLUSIONS: The optimal approach to management of uncomplicated dyspepsia is dependent on the prevalence of H. pylori among the dyspeptic population. At the current prevalence rate, 'test and treat', followed by acid suppressive treatment in the case of persisting symptoms, is the most appropriate strategy.

Alterations in penicillin-binding protein 1A confer resistance to beta-lactam antibiotics in Helicobacter pylori.

Most Helicobacter pylori strains are susceptible to amoxicillin, an important component of combination therapies for H. pylori eradication. The isolation and initial characterization of the first reported stable amoxicillin-resistant clinical H. pylori isolate (the Hardenberg strain) have been published previously, but the underlying resistance mechanism was not described. Here we present evidence that the beta-lactam resistance of the Hardenberg strain results from a single amino acid substitution in HP0597, a penicillin-binding protein 1A (PBP1A) homolog of Escherichia coli. Replacement of the wild-type HP0597 (pbp1A) gene of the amoxicillin-sensitive (Amx(s)) H. pylori strain 1061 by the Hardenberg pbp1A gene resulted in a 100-fold increase in the MIC of amoxicillin. Sequence analysis of pbp1A of the Hardenberg strain, the Amx(s) H. pylori strain 1061, and four amoxicillin-resistant (Amx(r)) 1061 transformants revealed a few amino acid substitutions, of which only a single Ser(414)-->Arg substitution was involved in amoxicillin resistance. Although we cannot exclude that mutations in other genes are required for high-level amoxicillin resistance of the Hardenberg strain, this amino acid substitution in PBP1A resulted in an increased MIC of amoxicillin that was almost identical to that for the original Hardenberg strain.

Six-year follow-up after successful triple therapy for Helicobacter pylori infection in patients with peptic ulcer disease.

OBJECTIVE & DESIGN: We question whether Helicobacter pylori eradication in peptic ulcer disease patients leads to a decrease in symptoms and reduced use of anti-dyspeptic drugs. Therefore, the recurrence rate of H. pylori, upper abdominal symptoms and the use of acid-suppressive drugs were determined 6 years after successful triple therapy. METHODS: Peptic ulcer disease patients successfully treated in 1990-1993 with 'classic' triple therapy were eligible. Patients were asked about symptoms and invited for a 13C-urea breath test or endoscopy in 1997-1998. Data on the use of anti-dyspeptic drugs were obtained from the pharmacy or general practitioner. RESULTS: Of the 113 eligible patients, 90 could be included in the study. The mean follow-up time was 6 years (range 4.6-7.6 years). H. pylori infection recurred in one patient (recurrence rate: 0.19% per patient-year; 95% confidence interval: 0.01-1.1%). Moderate or severe symptoms were experienced before therapy by 79% of the patients and after therapy by 18% of the patients (P< 10(-7)). Before triple therapy, 98% of the patients used H2-receptor antagonists and 54% were on maintenance treatment. After treatment, 30% used anti-dyspeptic medication and only 13% were on maintenance treatment (P < 10(-7)). CONCLUSIONS: Six years after successful triple therapy in peptic ulcer disease patients, the recurrence rate of H. pylori infection is low and both symptoms and the use of anti-dyspeptic drugs have decreased significantly.

The importance of vacA, cagA, and iceA genotypes of Helicobacter pylori infection in peptic ulcer disease and gastroesophageal reflux disease.

OBJECTIVE: To study the relationship between the presence of H. pylori virulence factors and clinical outcome in H. pylori infected patients. METHODS: DNA was isolated from an antral biopsy sample and vacA, cagA, and iceA genotype were determined by PCR and a reverse hybridization technique in 183 patients with culture-proven H. pylori infection: 51 with peptic ulcer disease (PUD), 62 with gastroesophageal reflux disease (GERD), and 70 with a normal endoscopy (gastritis only; GO). RESULTS: Forty-four samples (24%) showed more than one allelic variant in the vacA s- or in-region and/or both iceA1 and iceA2 genotypes, indicating multiple strain infection. These were excluded from statistical analysis. vacA s1 and cagA were significantly more common in PUD than in GERD and GO. Logistic regression analysis showed that GERD patients were more often infected with strains lacking both cagA and iceA than GO patients (OR = 0.36; CI = 0.15-0.89). Trend analysis showed that GERD patients were most often infected with less virulent strains (p < 0.002). CONCLUSION: Multiple strain infection is common. H. pylori strains possessing the vacA s1 genotype and/or cagA are associated with PUD. GERD patients, infected with H. pylori, mostly carry less virulent strains possessing neither cagA nor iceA1. Our findings support the hypothesis that virulent strains protect against the development of GERD.

Changes in the vaginal flora after two percent clindamycin vaginal cream in women at high risk of spontaneous preterm birth.

OBJECTIVE: To analyse alterationS in the vaginal flora after 2% clindamycin vaginal cream or placebo administered for the prevention of preterm delivery in high risk women. DESIGN: Observational study during a randomised multicentre double-blind placebo controlled trial. SETTING: Twelve city hospitals in The Netherlands. PARTICIPANTS: One hundred and sixty-eight women were enrolled. Alterations in the vaginal flora could be analysed in one hundred and twenty-four women by comparing the Nugent score on entry to the trial and at 31 weeks' gestation. The Nugent score was classified into normal, intermediate and bacterial vaginosis. INTERVENTIONS: Two percent clindamycin vaginal cream or placebo cream administered daily for seven days at week 26 of pregnancy. MAIN OUTCOME: Changes in the vaginal flora at week 31 of pregnancy. RESULTS: The placebo group consisted of 64 women and the clindamycin group of 60 women. At week 31 the vaginal flora was similar to week 26 with placebo cream but changed from normal vaginal flora to intermediate or bacterial vaginosis with 2% clindamycin vaginal cream. CONCLUSION: Obstetricians should not prescribe 2% clindamycin vaginal cream to pregnant women with normal vaginal flora in order to reduce the incidence of preterm birth. because it has no beneficial effects and is actually harmful. 2% Clindamycin vaginal cream encourages the presence of bacterial vaginosis which is epidemiologically associated with preterm birth.

Implications of the simultaneous presence of metronidazole-susceptible and -resistant Helicobacter pylori colonies within a single biopsy specimen.

This study examined whether the simultaneous presence of metronidazole-susceptible and -resistant Helicobacter pylori colonies in a single biopsy specimen is caused by a multiple strain infection with a susceptible and a resistant strain or by two subpopulations within a single strain. Single colonies obtained from seven biopsy specimens known to harbour both susceptible and resistant Helicobacter pylori were fingerprinted by restricted fragment length polymorphism typing of the ureC gene and by the random amplified polymorphic DNA procedure. Metronidazole susceptibility was determined by the E test. The results indicated that the occurrence of metronidazole-resistant and metronidazole-susceptible bacteria within a single biopsy does not imply the presence of a multiple strain infection with one resistant and one sensitive strain.

The accuracy of the Helicobacter pylori stool antigen test in diagnosing H. pylori in treated and untreated patients.

OBJECTIVE AND DESIGN: To evaluate the performance of the Helicobacter pylori stool antigen test (HpSA test) in detecting H. pylori infection and monitoring the effect of treatment. This was done in two separate studies using either a biopsy or the 13C-urea breath test based 'gold standard' (in untreated and treated patients, respectively). SETTING: Endoscopy units of two general hospitals. PATIENTS: One hundred and twenty-eight dyspeptic patients undergoing endoscopy in the first study. Sixty-five patients receiving anti-H. pylori treatment in the second study. RESULTS: Sensitivity and specificity in untreated patients were 96.3% and 81.8%, respectively. Seven days after treatment, these figures were 20% and 95%, and 4 weeks after treatment they were 40% and 95%. CONCLUSION: The HpSA test is accurate in untreated patients but fails in monitoring treatment success.

Mechanism and clinical significance of metronidazole resistance in Helicobacter pylori.

Metronidazole was introduced in 1959 for the treatment of Trichomonas vaginalis, but was subsequently shown to be active against anaerobic and some micro-aerophilic bacteria as well. In anaerobic microorganisms with their low redox potential, metronidazole is reduced to its active metabolite by a one-electron transfer step. Metronidazole is often used in treatment regimens for Helicobacter pylori, a microaerophilic bacterium, but resistance to this drug is frequently encountered. The metabolism of metronidazole in H. pylori must differ from that in anaerobic bacteria as metabolites formed by a one-electron transfer are readily re-oxidized in the micro-aerophilic environment of H. pylori. This process is called 'futile cycling' and is accompanied by the formation of toxic oxygen radicals that are neutralized by an active scavenger system. Recently, it has been shown that in H. pylori, in contrast to the situation in anaerobes, an oxygen-insensitive nitroreductase. encoded by the rdxA gene, is responsible for the activation of metronidazole. Activation by this enzyme is by a two-electron transfer step, preventing futile cycling' and thereby enabling the activation of metronidazole in a micro-aerophilic environment. Metronidazole resistance has been shown to be associated with null mutations in the rdxA gene in most clinical isolates. However, there may be some 'background metronidazole susceptibility' in metronidazole-resistant strains caused by other (oxygen-sensitive) nitroreductases. Recently, three meta-analyses of the impact of metronidazole resistance on treatment efficacy have all shown a significant reduction in efficacy of metronidazole containing regimens in patients infected with a resistant strain. The impact of resistance proved to be dependent on the other components of the regimen and on treatment duration.

Review article: nitroimidazole resistance in Helicobacter pylori.

The efficacy of a nitroimidazole-containing regimen for the treatment of Helicobacter pylori infection is decreased by nitroimidazole resistance. Nitroimidazoles are meta- bolized by H. pylori by several nitro-reductases of which an oxygen-insensitive NADPH nitroreductase encoded by the rdxA gene is the most important. Null mutations in this gene are associated with resistance. Susceptibility testing to nitroimidazoles may give variable results. This is not only related to the slow growth under specific conditions, but also to variability in the activity of the other nitroreductases and the ability to deactivate toxic metabolites of an NI and to repair DNA damage. Moreover, co-infections with resistant and susceptible bacteria are frequently found. The presence of nitroimidazole resistance is related to the previous use of this drug. The prevalence of resistance is rising and nowadays 10-50% of the isolates are resistant. Resistance reduces the efficacy of a treatment regimen to a variable degree. This is related to efficacy of the other components of the regimen and the treatment duration. Whether a nitroimidazole is still effective in resistant strains remains unresolved. When nitroimidazole resistance is present, a nitro-imidazole-containing regimen should be avoided or a regimen with other highly effective components should be used.

Reliability of biopsy-based diagnostic tests for Helicobacter pylori after treatment aimed at its eradication.

OBJECTIVE: Recurrence of Heliobacter pylori after apparently successful treatment mostly represents resurgence of the infection, rather than a new one. Therefore, the reliability of biopsy-based tests after treatment was investigated. METHODS: Four weeks or more after treatment, antral biopsy samples were taken for culture, histology, urease test and polymerase chain reaction (PCR), and a corpus specimen for culture. Treatment failure was defined as > or = 2 tests positive. If one test was positive, a 13C-urea breath test was performed and considered conclusive. RESULTS: One hundred and ninety-seven patients were evaluated. Endoscopy was performed 53 days (27-92 days) after treatment. Twenty-one patients with missing test results and 19 patients on acid-suppressive drugs were excluded. In 140 of 156 patients (89.7%), H. pylori was eradicated. Sensitivity and specificity of culture of antrum were, respectively, 100% and 100%; culture of corpus, 100% and 100%; rapid urease test, 87% and 99%; haematoxylin/eosin stain, 94% and 95%; Giemsa stain, 81% and 99%; and PCR, 88% and 100%. CONCLUSION: Although all biopsy-based tests are reliable after treatment, culture is the biopsy-based test of first choice as it is the most accurate and gives additional information on antibiotic resistance.