Evaluation of the INNO-LiPA Rif. TB assay, a reverse hybridization assay for the simultaneous detection of Mycobacterium tuberculosis complex and its resistance to rifampin

Mycobacterium tuberculosis resistance to rifampin results from nucleotide changes in the gene encoding the beta-subunit of the RNA polymerase (rpoB). We developed a reverse hybridization-based line probe assay (LiPA; the INNO-LiPA Rif. TB) carrying one oligonucleotide probe for the detection of M. tuberculosis complex strains and nine probes designed to detect nucleotide changes in the relevant part of rpoB. This assay was evaluated with 107 M. tuberculosis isolates with known rpoB sequences, 52 non-M. tuberculosis complex strains, and 61 and 203 clinical isolates found to be sensitive and resistant, respectively, by in vitro testing. The results indicated that (i) the M. tuberculosis complex probe was 100% specific, (ii) when compared to the results of nucleotide sequencing, no discrepancies with the results of INNO-LiPA Rif. TB were observed, (iii) all strains sensitive by in vitro susceptibility testing were correctly identified, and (iv) among the strains resistant by in vitro susceptibility testing, only 4 (2%) yielded conflicting results. The INNO-LiPA Rif. TB is therefore a reliable and widely applicable assay and a valuable tool for routine diagnostic use, given its simplicity and rapid performance.

Rapid detection of rifampicin resistance in sputum and biopsy specimens from tuberculosis patients by PCR and line probe assay

SETTING

Multidrug resistant Mycobacterium tuberculosis strains are threatening TB control in the world. Rapid diagnosis of resistance is essential for adequate treatment and optimal control of the disease.

OBJECTIVE

Evaluation of a new technique (Line Probe Assay, LiPA) for easy and rapid detection of Rifampicin resistance (RMPR) of M. tuberculosis.

DESIGN

After amplification of the region of the RNA polymerase, involved in RMPR, the amplified product is hybridized with a set of 10 oligonucleotides immobilized onto a membrane strip. From the pattern obtained the presence or absence of RMPR M. tuberculosis can be assessed. 67 clinical samples positive in culture for M. tuberculosis were analyzed with LiPA and results were compared with classical susceptibility testing.

RESULTS

In vitro drug sensitivity testing identified 46 rifampicin sensitive and 21 resistant strains. In 65 of the 67 specimens LiPA results matched classical testing. In two RMPR cases LiPA showed a sensitive pattern.

CONCLUSION

In contrast to culture and sensitivity testing, where results take on average 6 weeks, LiPA testing is an easy and rapid (< 48 h) method of detecting RMPR M. tuberculosis in clinical samples. Results correlated in 97% of the samples. In the two RMPR samples with a sensitive LiPA pattern another mechanism of resistance is suspected.

Identification of Mycobacterium species by using amplified ribosomal DNA restriction analysis

A rapid procedure for the identification of cultured Mycobacterium isolates, based on the combination of enzymatic amplification and restriction analysis, is described. The 16S rRNA genes (rDNA) of 99 strains belonging to 18 different species of the genus Mycobacterium were enzymatically amplified. Amplified rDNA restriction analysis with the enzymes CfoI, MboI, and RsaI was carried out. The combination of the amplified rDNA restriction analysis patterns obtained after restriction with CfoI and MboI enabled differentiation between Mycobacterium asiaticum (number of strains = 4), M. avium (n = 22), M. chelonae (n = 5), M. flavescens (n = 1), M. fortuitum (n = 6), M. gordonae (n = 6), M. intracellulare (n = 13), M. marinum (n = 7), M. nonchromogenicum (n = 1), M. simiae (n = 5), M. terrae (n = 5), the M. tuberculosis complex (n = 11), and 2 of 4 strains of M. xenopi. Further restriction with RsaI was necessary to differentiate between the species M. kansasii (n = 5), M. scrofulaceum (n = 4), and the 2 other M. xenopi strains. The M. avium-M. intracellulare complex was characterized by a specific MboI pattern, and M. avium and M. intracellulare strains could further be differentiated by restriction with CfoI. The whole procedure, including sample preparation prior to the polymerase chain reaction, can be carried out within 8 h, starting from a pure culture.

Polyclonal emergence and importation of community-acquired methicillin-resistant Staphylococcus aureus strains harbouring Panton-Valentine leucocidin genes in Belgium

OBJECTIVES

Worldwide spread of a limited number of Panton-Valentine leucocidin (PVL) -producing methicillin-resistant Staphylococcus aureus (MRSA) clones has been reported in various communities. The objective of this study was to describe the molecular characteristics of the first PVL-positive MRSA strains isolated in Belgium.

METHODS

Clinical MRSA isolates (n = 41) collected from 2002 to 2004 from Belgian patients were investigated for the PVL gene by PCR. PVL-positive isolates were genotyped by PFGE, staphylococcal cassette chromosome mec (SCCmec) typing, spa sequence typing, accessory gene regulator (agr) polymorphism and multi-locus sequence typing (MLST). Susceptibility to 14 antimicrobials was determined by the disc diffusion method. Genes encoding resistance to tetracyclines, aminoglycosides and macrolide-lincosamide-streptogramin were determined by PCR.

RESULTS

Sixteen isolates carried lukS-lukF genes that encode the PVL toxin. All but one isolate were community-acquired. Three patients reported recent travel to North Africa and South America. They were associated with skin or soft tissue infections, bacteraemia and peritonitis. By molecular typing, they belonged to five genotypes: ST80-SCCmec IV, ST8-SCCmec IV, ST30-SCCmec IV, ST153-SCCmec IV and ST88-SCCmec IV. They belonged to the agr type 3 except for ST8 strains, which showed agr type 1. All isolates were susceptible to fluoroquinolones. Approximately, half of them were resistant to tetracycline, fusidic acid and kanamycin. Tetracycline-resistant strains harboured the tet(K) gene and resistance to kanamycin was associated with the aph3'-IIIa gene. The single erythromycin-resistant isolate harboured msr(A/B) genes conferring the M resistance phenotype.

CONCLUSIONS

These results indicate the recent emergence and sporadic importation into Belgium of PVL-positive community-associated MRSA strains belonging to five distinct clones.

Variability in 3' end of 16S rRNA sequence of Mycobacterium ulcerans is related to geographic origin of isolates

Mycobacterium ulcerans causes extensive ulcers (Buruli ulcers) in the skin of humans. Analysis of the 3'-terminal region of the 16S rRNA gene sequence of 17 strains of M. ulcerans from Africa, the Americas, and Australia revealed three subgroups corresponding to the continent of origin, and some variable phenotypic characteristics. This sequence is useful for the rapid detection of M. ulcerans and discriminates M. marinum and M. shinshuense from M. ulcerans.

Hepatitis C virus in a hemodialysis unit: molecular evidence for nosocomial transmission

Between February 1991 and January 1992, elevated alanine aminotransferase (ALT) levels were observed in several hemodialysis patients in a dialysis center in Dendermonde, Belgium. By the end of 1992, 25 out of 68 patients had seroconverted for HCV antibodies. The HCV strains from 23 of these seroconverters were genotyped and classified as genotype 1b. Sequence analysis of the HCV Core region was carried out in 12 patients, 9 of whom were infected with a strain bearing a unique sequence motif as compared with the currently known HCV 1b strains. A new 5' UR/Core line probe assay was designed to screen for such variations. Twenty patients tested positively for this special sequence motif, while the other 3 showed the regular subtype 1b sequence. Phylogenetic analysis of the Core sequences further revealed that the latter three were neither related to the main special strain of the infection, nor to each other. These three strains could be traced to two patients already infected at the time of residence in other dialysis units and to one patient who already showed ALT elevations in 1989. Epidemiological studies revealed no traceable source for this outbreak. In conclusion, molecular analysis demonstrates nosocomial transmissions by a peculiar genotype 1b strain in a dialysis center. Three other genotype 1b strains were also present in the unit, but were not responsible for the outbreak.

Direct detection and identification of Mycobacterium ulcerans in clinical specimens by PCR and oligonucleotide-specific capture plate hybridization

We compared various diagnostic tests for their abilities to detect Mycobacterium ulcerans infection in specimens from patients with clinically active disease. Specimens from 10 patients from the area of Zangnanado (Department of Zou, Benin) with advanced, ulcerated active M. ulcerans infections were studied by direct smear, histopathology, culture, PCR, and oligonucleotide-specific capture plate hybridization (OSCPH). A total of 27 specimens, including 12 swabs of exudate collected before debridement and 15 fragments of tissue obtained during debridement, were submitted to bacteriologic and histopathologic analysis. The histopathologic evaluation of tissues from all six patients so tested revealed changes typical of those caused by M. ulcerans infection. Five specimens were contaminated, and M. ulcerans was cultivated on Löwenstein-Jensen medium from 12 of the remaining 22 (54.5%) specimens. Detection of mycobacteria was performed by PCR, and M. ulcerans was detected by OSCPH with a new probe (5'-CACGGGATTCATGTCCTGT-3') reacting with M. ulcerans and Mycobacterium marinum. In 10 of 22 (45.5%) specimens, M. ulcerans was identified by PCR-OSCPH. There was no statistically significant difference between the detection of M. ulcerans by culture and by PCR-OSCPH (P > 0.05). This is the first demonstration of an amplification system (PCR-OSCPH) with a sensitivity similar to that of culture for the direct and rapid recognition of M. ulcerans in clinical specimens. This system is capable of identifying M. ulcerans, even in paucibacillary lesions. Our findings suggest that PCR-OSCPH should be used in the quest for the elusive environmental reservoir(s) of M. ulcerans.

Detection and identification of mycobacteria by DNA amplification and oligonucleotide-specific capture plate hybridization

We have developed an easy and rapid detection and identification system for the diagnosis of mycobacterial diseases. The system is based on selective amplification by PCR of mycobacteria with primers based on the genes coding for 16S rRNA. During PCR, a label (digoxigenin-11-dUTP) is incorporated with biotinylated species-specific oligonucleotides (oligonucleotide-specific capture plate hybridization [OSCPH]. One oligonucleotide specific for the genus Mycobacterium and seven species-specific (Mycobacterium tuberculosis, M. avium, M. intracellulare, M. scrofulaceum, M. xenopi, M. genavense, and M. chelonae) oligonucleotides were designed as capturing probes. After specific hybridization, an enzyme immunoassay reveals the specifically bound complexes and thus permits identification of the mycobacterium. A total of 70 mycobacterial strains were tested. For 69 strains, results concordant with conventional identification were obtained. One M. chelonae strain was negative with the M. chelonae probe and was later reidentified as M. fortuitum. Moreover, for 15 clinical samples suspected of harboring nontuberculous mycobacteria, OSCPH was able to confirm all culture results and could identify one M. genavense infection for which standard culture results were negative. PCR-OSCPH is easily applicable and much faster than culture. It could become a valuable alternative approach for the diagnosis of mycobacterial infections.

Design and evaluation of new, highly sensitive and specific primers for polymerase chain reaction detection of HIV-1 infected primary lymphocytes

Primer pairs in the HIV-1 POL and ENV genes were evaluated by performing a PCR on lysed peripheral blood mononuclear cells (PBMCs) from 96 HIV-1 seropositive and 40 seronegative individuals originating from 16 different geographical localities in Africa, Europe and Haiti. A single PCR using primer pairs to the LTR, GAG and ENV regions and detection by radioactively labelled oligonucleotide probes was compared to a nested PCR scheme using newly designed POL and ENV primers which used ethidium-bromide staining of the amplified product on agarose gel. The newly designed POL nested primer pair was shown to be highly sensitive (93%) and specific (100%) for the detection of HIV-1 proviral DNA of very diverse geographical and genetic origin, including highly aberrant HIV-1 isolates. The sensitivity of the newly designed ENV primers was 68.7%, which does not differ significantly from the sensitivity of the classical primers, SK 68/69. Both ENV primers were unable to amplify two SIVcpz isolates from naturally infected chimpanzees.

Detection of human immunodeficiency virus type 1 (HIV-1) in heel prick blood on filter paper from children born to HIV-1-seropositive mothers

The human immunodeficiency virus type 1 (HIV-1) DNA PCR results of 94 dried blood spot (DBS) samples on filter paper and corresponding venous blood in EDTA obtained from infants born to HIV-1-seropositive mothers were compared. In addition, the results of HIV-1 DNA PCR on DBS and the HIV-1 RNA PCR from plasma of 70 paired samples were compared. A 100% specificity and a 95% sensitivity for HIV-1 DNA PCR on DBS compared with results for venous blood were observed for the 94 paired samples. The results of the DBS HIV-1 DNA PCR and HIV-1 RNA PCR of 70 corresponding plasma samples correlated perfectly (100%). The DBS HIV-1 DNA PCR method proved reliable for HIV-1 detection.

Monitoring of herpes simplex virus in the lower respiratory tract of critically ill patients using real-time PCR: a prospective study

Herpes simplex virus (HSV) has increasingly been associated with pulmonary disease in critically ill patients. However, the clinical relevance of HSV is still a topic of debate. Monitoring of HSV in a quantitative way could potentially give relevant information on its role in the pathogenesis of lower respiratory tract infection. A fast and reliable quantitative real-time PCR (Q-PCR) for the quantitative detection of HSV-1 and HSV-2 DNA was developed. A prospective observational study was performed in an intensive-care unit (ICU) to monitor the HSV viral load in lower respiratory tract aspirates of long-term mechanically ventilated patients. HSV was common in the lower respiratory tract (LRT) of critically ill patients with mechanical ventilation for at least 48 h (62%, n = 65/105). Detection of HSV was significantly associated with prolonged mechanical ventilation (p <0.01), prolonged ICU stay (p <0.01), and development of ventilator-associated pneumonia (p = 0.02). Corticosteroid administration (p <0.01) in the ICU and anti-HSV IgG seropositivity (p <0.01) were risk factors for the occurrence of HSV in the LRT. The fact that no HSV-seronegative patient became positive suggests that all HSV DNA-positive patients had HSV reactivations. Monitoring the HSV viral load in the LRT of critically ill patients showed a typical homogeneous pattern of HSV kinetics. HSV emerged in tracheal and bronchial aspirates after a median of 7 days of intubation (5-11 days), and this was followed by an exponential increase (c. 1 log copies/mL/day) to reach very high HSV peaks (10(6)-10(10) copies/mL) in 78% of the HSV DNA-positive patients.

Use of a multiplex real-time PCR to study the incidence of human metapneumovirus and human respiratory syncytial virus infections during two winter seasons in a Belgian paediatric hospital

Viruses are an important cause of acute respiratory tract infection (ARTI) in children. This study aimed to develop and evaluate a rapid molecular diagnostic test (duplex real-time PCR) for human respiratory syncytial virus (hRSV) and human metapneumovirus (hMPV), and to determine the frequency of these two viruses as causative agents of ARTI in Belgium. Nasopharyngeal aspirates were collected over two winter and spring seasons (November 2003 to May 2004 and November 2004 to May 2005) from children aged <5 years with ARTI (n = 778). The duplex real-time PCR showed a linear range of 10⁴–10¹⁰ copies/mL for both hMPV and hRSV. Analysis of the stability of the hRSV and hMPV genomes revealed that nasopharyngeal aspirates could be stored at room temperature for up to 1 month without significant loss of detection. hRSV was detected by antigen testing and by real-time PCR; hMPV was detected by real-time PCR only. The hRSV antigen test was less sensitive than PCR, and failed to detect one-third of the hRSV infections. Overall, 54 (6.9%) and 306 (39.3%) of the 778 samples were positive for hMPV and hRSV, respectively. Both viruses infected young infants, but the mean age of infants infected by hRSV was lower than that of infants infected by hMPV (12 months vs. 17 months, respectively).

Pathogens in Early-Onset and Late-Onset Intensive Care Unit–Acquired Pneumonia

Objectives.

To compare the type of pathogens isolated from patients with early-onset intensive care unit (ICU)-acquired pneumonia with those isolated from patients with late-onset ICU-acquired pneumonia and to study risk factors for the isolation of pathogens that are potentially resistant to multiple drugs.

Design.

Prospective cohort study.

Setting.

Patients admitted to the ICU of a 677-bed, university-affiliated teaching hospital in Belgium during 1997-2002.

Methods.

ICU-acquired pneumonia was defined as a case of pneumonia that occurred 2 days or more after admission to the ICU in combination with a positive results of radiologic analysis, clinical signs and symptoms, and a positive culture result. All cases of pneumonia were categorized as either early onset (within 7 days after admission) and late onset (7 days or more after admission), with or without previous antibiotic treatment, and the corresponding pathogens were analyzed. Risk factors for the isolation of pathogens potentially resistant to multiple drugs (ie, Pseudomonas aeruginosa, Serratia marcescens, Enterobacter species, Morganella morganii, methicillin-resistant Stapylococcus aureus, Citrobacter species, Acinetobacter species, Burkholderia species, extended-spectrum β-lactamase–producing pathogens, and Stenotrophomonas maltophilia) were analyzed using logistic regression analysis.

Results.

A total of 4,200 patients stayed at the ICU for 2 or more days, 298 of whom developed ICU-acquired pneumonia, for an overall incidence of 13 cases (95% confidence interval [CI], 11-14 cases) per 1,000 ICU-days. Pathogens potentially resistant to multiple drugs were isolated from 52% of patients with early-onset pneumonia. Risk factors for the isolation of these pathogens were greater age and previous receipt of antibiotic prophylaxis (adjusted odds ratio [aOR], 4.6 [95% CI, 1.6-13.0]) or antibiotic therapy (aOR, 8.2 [95% CI, 2.8-23.8]). The length of ICU admission and hospital stay were weaker risk factors for the isolation of these pathogens.

Conclusions.

Pathogens potentially resistant to multiple drugs were isolated in 52% of cases of early-onset ICU-acquired pneumonia. Previous antibiotic use (both prophylactic and therapeutic) is the main risk factor for the isolation of these pathogens.

Quantification of human immunodeficiency virus in plasma by RNA PCR, viral culture, and p24 antigen detection

A semiquantitative PCR technique for detecting human immunodeficiency virus type 1 (HIV-1) RNA in plasma was compared with quantitative viral culture and p24 antigen detection in plasma. Ninety-three samples from 20 symptomatic, 10 asymptomatic, and 10 seronegative individuals were tested. For most of the seropositive patients, consecutives samples were examined. Viral RNA was extracted from plasma by the method described by Boom et al. (R. Boom, C.J. A. Sol, M. M. M. Salimans, C.L. Jansen, P. M. E. Wertheim-van Dillen, and J. van der Noordaa, J. Clin. Microbiol. 28:495-503, 1990). The RNA PCR was the most sensitive method (100 and 74% sensitivity for symptomatic and asymptomatic patients, respectively) and produced less divergent results with the consecutive samples from individual patients compared with the other techniques. All samples positive by viral culture or p24 antigen assay were also positive in the RNA PCR. For each of the three assays, the number of positive results obtained correlated with the disease stage. The estimated mean number of HIV-1 RNA copies was significantly higher in symptomatic patients (22,750 copies per ml) than in asymptomatic patients (1,820 copies per ml). It was also higher in samples positive for viral culture than in culture-negative samples. No close correlation was found between the amount of HIV-1 RNA and the amount of p24 antigen or the titer of infectious virus in plasma or between this titer and the level of p24 antigen. The plasma RNA PCR may be a useful additional marker of disease progression and may be valuable for monitoring the effects of antiviral therapy.

Simultaneous detection of human bocavirus and adenovirus by multiplex real-time PCR in a Belgian paediatric population

Since the discovery of human bocavirus (hBoV), the virus has been detected worldwide in respiratory tract samples from young children by various polymerase chain reaction (PCR) assays and real-time PCRs (Q-PCR). Until now, no data have been reported on the presence of hBoV in Belgium and the detection of hBoV in a multiplex Q-PCR setting has not been described. The aim of this study was to develop a fast and reliable multiplex Q-PCR for the simultaneous detection of hBoV DNA and adenovirus (AdV) DNA. During the winter of 2004–2005, 445 nasopharyngeal aspirates (NPAs) were analysed from 404 Belgian children up to 5 years old with acute respiratory tract infections (ARTIs). (Co)infections with hBoV, AdV, respiratory syncytial virus (RSV), human metapneumovirus (hMPV) and influenza A virus were investigated. A viral agent was detected in 61% (n = 272/445) of the NPAs. Multiplex Q-PCR found a prevalence of 11% (n = 51/445) hBoV and 13% (n = 58/445) AdV. Coinfections were more frequently found with AdV (62%; n = 36/58) than with hBoV (49%; n = 25/51). Follow-up samples were available from 22 patients with ARTIs. In three patients, hBoV DNA persisted for one month. Multiplex Q-PCR may help in closing the diagnostic gap by addressing a broader range of potential respiratory pathogens.

Cervical lymphadenitis caused by a fastidious mycobacterium closely related to Mycobacterium genavense in an apparently immunocompetent woman: diagnosis by culture-free microbiological methods

Fastidious mycobacteria usually infect immunocompromised hosts (human immunodeficiency virus-infected or otherwise immunosuppressed patients). We here describe severe lymphadenitis, caused by a fastidious mycobacterium closely related to Mycobacterium genavense, in an apparently immunocompetent woman, whose brother had died from an unidentified mycobacterial infection in 1969. A variety of techniques, including inoculation of nude mice, histopathology, electron microscopy, lipid analysis, ATP measurements, and molecular biology, were used to characterize this mycobacterium. All attempts to culture the etiological agent on many different media failed. The organism multiplied only in congenitally athymic nude mice. Although phenotypically similar to M. genavense, the mycobacterium differs from M. genavense by three nucleotides of the 16S rRNA gene sequence. Various antimycobacterial drugs were administered, including gamma interferon, but multiple relapses occurred. Finally, therapy with a combined regimen of clarithromycin, clofazimine, rifabutin, and ethambutol was curative. To our knowledge, this is the first report of lymphadenitis in an apparently immunocompetent patient, caused by a noncultivable Mycobacterium sp. closely related to M. genavense. This study emphasizes the importance of employing a variety of diagnostic approaches such as the inoculation of laboratory animals, histopathology, electron microscopy, lipid analysis, ATP measurements, and molecular biology to characterize novel microorganisms that cannot be cultured in vitro.

Atypical pneumonia due to Chlamydophila psittaci: 3 case reports and review of literature

Chlamydophila psittaci is the causative agent of psittacosis or ornithosis. The disease is transmitted to men predominantly from birds. Most commonly noted symptoms are fever, headache and cough, but a number of other symptoms or complications may arise such as renal impairment, hepatitis or neurological symptoms. In this article 3 cases of psittacosis are presented, with a review of the literature with emphasis on laboratory diagnosis.

A pilot study of the prevalence of hepatitis C virus antibodies and hepatitis C virus RNA in southern Cameroon

Information is lacking on the prevalence of hepatitis C virus (HCV) infection in most African countries. An algorithm based on a combination of enzyme immunoassays (EIAs) with different formats (a commercial test, an HCV antibody [Ab] III test, and an HCV core Ab EIA) was used to estimate the prevalence of HCV infection in different population groups from southern Cameroon. An overall high prevalence was observed, with a significant increasing trend for both sexes with respect to age. A high proportion (67.4%) of HCV-positive sera were viremic as demonstrated by the reverse transcription-polymerase chain reaction. We conclude that the prevalence of HCV is high in southern Cameroon and increases linearly with age.

Association of hepatitis C virus carrier state with the occurrence of hepatitis C virus core antibodies

An enzyme immunoassay (EIA) was developed for the determination of antibodies against the "putative" core protein of hepatitis C virus (HCV). Antigens used were recombinant fragments (amino acids 6-77 or 6-143) of the HCV core protein, produced in Escherichia coli with truncated hepatitis B core (HBc) as fusion protein. Evaluation of 385 sera positive for HCV antibodies by first generation EIA, revealed 98 (25.4%) with HCV core antibodies. HCV-RNA, determined by the polymerase chain reaction (PCR), was exclusively found in the sera positive for HCV core antibodies (89 PCR positives). In random screening of 3,708 sera, 3 sera with HCV core antibodies were found PCR positive. Only 2 of these sera were positive in the first generation EIA. It is concluded that HCV core antibody determination is a reliable test for identifying HCV carriers among blood donors.

Confirmation of hepatitis C virus positive blood donors by immunoblotting and polymerase chain reaction

In a series of 385 sera obtained from volunteer blood donors positive for the first-generation hepatitis C virus assay (Ortho), the viral genome was detected by polymerase chain reaction (PCR) in 89 sera (23%). Most PCR-positive sera were found positive with the c100-3 neutralisation assay (Abbott) and by two second-generation enzyme immunoassays (Abbott, Ortho). However overall specificity of these assays was rather low. By immunoblotting (Innogenetics and Chiron/Ortho) the specificity could be considerably improved and the best correlation with carrier state was obtained when analysing the results for lane-specific reaction: all 89 viral carriers and only 9 other donors had antibodies against structural 'core' epitopes. From the present data we can conclude that in screening a volunteer blood donor population the confirmation of antibodies against 'core' epitopes by immunoblotting is strongly associated with viral carriage.

Comparison of five SARS-CoV-2 rapid antigen detection tests in a hospital setting and performance of one antigen assay in routine practice: a useful tool to guide isolation precautions?

BACKGROUND

In a hospital setting, there is a need for rapid detection of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) to guide isolation measures and targeted admission.

AIM

To evaluate the diagnostic performance of five SARS-CoV-2 rapid nucleocapsid protein antigen detection (RAD) assays (Biosynex, Biotical, Orient Gene, Panbio and SD Biosensor), and describe the performance and impact of implementation of the SD Biosensor assay in an emergency department.

METHODS

Sensitivity and specificity of the five RAD assays were analysed on 100 respiratory samples: 60 real-time reverse transcriptase polymerase chain reaction (rRT-PCR)-confirmed SARS-CoV-2-positive samples, 24 SARS-CoV-2 RNA-negative samples and 16 samples positive for other respiratory pathogens. The manufacturer's protocol was adapted to validate the antigen tests on transport media used for rRT-PCR in the authors' routine practice. The SD Biosensor RAD assay was implemented as a screening method for rapid diagnosis and targeted admission.

FINDINGS

Sensitivity of the five RAD assays ranged from 88.9% to 100% for samples with cycle threshold values <26, and specificity ranged from 46.2% to 100%. During the implementation period, 4195 RAD tests were performed. Due to the rapid RAD result, 157 patients were transferred directly to the coronavirus disease 2019 (COVID-19) cohort ward instead of the regular ward (N=47) or the temporary COVID-19 ward (N=110).

CONCLUSION

The SD Biosensor, Biotical and Panbio SARS-CoV-2 antigen tests showed acceptable overall performance, and identified the majority of contagious patients. In the context of high prevalence of SARS-CoV-2, RAD tests can be used as a rapid screening tool to guide infection prevention measures and aid targeted admission.

Detection of fastidious mycobacteria in human intestines by the polymerase chain reaction

The aim of this study was to determine whether difficult-to-grow mycobacteria are present in human intestines. Intestinal tissue samples were subjected to both mycobacterial culture and a polymerase chain reaction (PCR) assay. After detection by PCR, species identity was determined by hybridizing the amplified 16S rRNA gene fragments with species-specific oligonucleotides. Intestinal biopsies from 63 patients with noninflammatory bowel diseases (n = 22), Crohn's disease (n = 31), or ulcerative colitis (n = 10) were analyzed. Culture and PCR revealed mycobacteria in four (6%) and 25 (40%) samples, respectively. Samples positive by PCR were negative with all probes specific to nine common cultivable species but were positive with Mycobacterium genavense-specific probe in 68% of cases. Mycobacterial isolates were identified as Mycobacterium gordonae and Mycobacterium chelonae. Findings were similar in Crohn's disease samples compared to non-Chron's disease samples. This study shows that difficult-to-grow mycobacteria can be detected by PCR in large and similar proportions of inflamed intestinal tissue from patients with inflammatory bowel disease and intestinal tissue that appears normal from patients with noninflammatory bowel disease.

Ten years phage-typing of Belgian clinical methicillin-resistant Staphylococcus aureus isolates (1992–2001)

Gradual changes have been observed in the phage-types of methicillin-resistant Staphylococcus aureus (MRSA) isolates from Belgian hospitals. A total of 6551 isolates, collected in 93 Belgian hospitals over 10 years (1992-2001), was examined. A decreasing incidence of the main early Belgian epidemic phage-types ([A], [B], [H]*, Jo*) was observed. Since 1997 and 2000, a new series of phage-types ([Hv]*, [J]*, [O]*), which were likely related to the previous group [H]*, have been noted. The general trends were confirmed in two particular hospitals. Local epidemic and/or endemic phage-types were also encountered.