Utility of an in-house mycobacteriophage-based assay for rapid detection of rifampin resistance in Mycobacterium tuberculosis clinical isolates

A rapid in-house mycobacteriophage-based assay to identify multidrug resistance by detecting the rifampin susceptibility of Mycobacterium tuberculosis in a microtiter plate format was evaluated. The sensitivity, specificity, and overall accuracy of the assay were 100%. This test is rapid to perform and suitable for widespread implementation.

Elevated serum procalcitonin values correlate with renal scarring in children with urinary tract infection

BACKGROUND

Urinary tract infection (UTI) in young children carries the risk of parenchymal damage and sequelae. The location of the infection within the urinary tract influences decisions regarding both therapeutics and follow-up. Because clinical features and laboratory markers of infection at an early age are not specific, it is difficult to make a distinction between lower UTI and acute pyelonephritis. Procalcitonin (PCT) has been studied as a marker of severe bacterial infection. The aim of this study was to test the usefulness of PCT concentration in serum to distinguish between uncomplicated UTI and severe acute pyelonephritis with renal scars.

METHODS

PCT was measured by immunoluminometric assay in serum samples from children with microbiologically documented infection. Severe renal involvement was assessed by 99mTc-dimercaptosuccinic acid gammagraphy done 5 to 6 months after the episode to check for the presence of parenchymal scars. C-reactive protein (CRP) and leukocyte count were also measured.

RESULTS

PCT at presentation showed a significant correlation (P < 0.001) with the presence of renal scars in children with UTI. Using a cutoff of 1 ng/ml for PCT and 20 mg/l for CRP, sensitivity and specificity in distinguishing between urinary tract infection with and without renal damage were 92.3 and 61.9%, respectively, for PCT and 92.3 and 34.4% for CRP. Positive and negative predictive values were 32 and 97.5%, respectively, for PCT and 23 and 95%, respectively, for CRP.

CONCLUSIONS

A low PCT value at admission indicates a low risk of long term renal scarring. Increased PCT values at admission correlate with the presence of scars. PCT values have proved to be more specific than CRP and leukocyte count for identifying patients who might develop renal damage.

Evaluation of two different cell lysis methods for releasing mycobacterial nucleic acids in the INNO-LiPA mycobacteria test

The INNO-LiPA Mycobacteria Test (Innogenetics, N.V., Belgium) is a PCR-based reverse hybridization assay for the simultaneous identification of several mycobacterial species. We evaluated two simplified lysis methods for mycobacterial DNA release for application in the INNO-LiPA Mycobacteria Test. The two methods were based on either (i) heat treatment or (ii) sonication. Both methods were performed directly on 45 positive liquid cultures (MB-BacT, BioMérieux, Marcy l'Etoile, France) containing 17 different mycobacterial species. These two simple lysis procedures demonstrated similar effectiveness (100%) to that recommended by the manufacturer. They also significantly shortened the time required for mycobacterial DNA release.

In-vitro evaluation of Perasafe compared with 2% alkaline glutaraldehyde against Mycobacterium spp

Quantitative suspension and carrier tests were used to compare the activity of Perasafe and Cidex against Mycobacterium tuberculosis, Mycobacterium avium-intracellulare, Mycobacterium fortuitum, and Mycobacterium chelonae. The interference of an organic load, and of hard water was also considered. Both agents achieved reductions exceeding 10(5)-fold within 20 and 30 min for all the strains tested. Perasafe is thus mycobactericidal and a viable alternative to Cidex for intermediate or high-level disinfection.

Usefulness of urinary antigen detection by an immunochromatographic test for diagnosis of pneumococcal pneumonia in children

We evaluated an immunochromatographic assay detecting pneumococcal antigen in urine samples from children diagnosed with pneumococcal pneumonia. The sensitivity and specificity of the immunochromatographic test with nonconcentrated urine (NCU) were 86.7 and 62.9%, respectively; with concentrated urine (CU), they were 100 and 11.7%, respectively. Pneumococcal antigen was also detected in 42.5% of NCU and 87.1% of CU samples from nasopharyngeal carriers. This is a nonspecific test for the diagnosis of pneumococcal pneumonia in children, particularly the very young.

In-use evaluation of Perasafe compared with Cidex in fibreoptic bronchoscope disinfection

The mycobactericidal activity of Perasafe (0.26% peracetic acid) was compared with that of Cidex (2% alkaline glutaraldehyde) by an in-use test. Fibreoptic bronchoscopes were artificially contaminated with Mycobacterium tuberculosis or Mycobacterium avium-intracellulare in sputum and, after manual pre-cleaning with a neutral soap, 10 and 20 min disinfection periods were tested. Perasafe was as effective as Cidex, thus requiring a 10 min disinfection period against M. tuberculosis and 20 min against M. avium-intracellulare. The results demonstrate that Perasafe is an effective disinfectant for use in reprocessing fibreoptic bronchoscopes.

Comparison of the sodium dodecyl sulfate-sodium hydroxide specimen processing method with the C18-carboxypropylbetaine specimen processing method using the MB/BacT liquid culture system

The ability of physicians to diagnose tuberculosis is impacted by the use of smear and culture techniques combined with specimen processing methods. The objective of this study was to evaluate the effects of specimen processing on smear and culture sensitivity by comparing the specimen processing method that uses C(18)-carboxypropylbetaine with the method that combines sodium dodecyl sulfate and sodium hydroxide. A total of 1,201 specimens were entered into this study. Specimens were split approximately equally such that one-half of each specimen was processed with sodium dodecyl sulfate-sodium hydroxide, while the other half was processed with C(18)-carboxypropylbetaine. All sediments were subjected to acid-fast staining and then analyzed using the MB/BacT liquid culture system (bioMérieux, France) and solid media. The sensitivity of smear following processing with sodium dodecyl sulfate-sodium hydroxide and C(18)-carboxypropylbetaine was 61.2% and 58.6% (P>0.05), respectively, while the specificities were identical (99.7%). The sensitivity of culture was 84.2% and 96.1% (P<0.05), respectively. The time to detection in the MB/BacT liquid culture system was 13.2+/-5.6 and 15.0+/-8.8 days (P>0.05), respectively, and 20.0+/-7.6 and 15.7+/-8.9 days (P<0.05), respectively, on solid media. The contamination rates in the MB/BacT system were 0.8% and 8.7%, respectively, whereas the contamination rates on solid media were 2.6% and 4.3%, respectively. C(18)-carboxypropylbetaine specimen processing was less labor-intensive than sodium dodecyl sulfate-sodium hydroxide processing and improved the ability of laboratory staff to detect the presence of mycobacteria by culture.

Catalase–peroxidase activity has no influence on virulence in a murine model of tuberculosis

The capacity to generate a chronic and persistent infection in the experimental murine model of tuberculosis induced aerogenically by a low-dose inoculum was determined in eight isoniazid-resistant clinical strains of Mycobacterium tuberculosis showing different catalase-peroxidase (C-P) activities. Determination of bacillary concentration in lung and spleen and the percentage of pulmonary parenchyma occupied by granulomas were monitored. Data showed no relation between the lack of C-P activity and the ability to develop a persistent infection, highlighting the potential of C-P negative strains to spread through the community.

Production of antibodies against glycolipids from the Mycobacterium tuberculosis cell wall in aerosol murine models of tuberculosis

Evolution of antibodies against glycolipids from the Mycobacterium tuberculosis cell wall has been studied for the first time in experimental murine models of tuberculosis induced by aerosol, in which infection, reinfection, reactivation, prophylaxis and treatment with antibiotics have been assayed. Results show a significant humoral response against these antigens, where diacyltrehaloses (DAT) and sulpholipid I (SL-I) elicited higher antibody levels than protein antigens like antigen 85 protein complex (Ag85), culture filtrate proteins (CFP) and purified protein derivative (PPD). Only immunoglobulin M (IgM) antibodies have been detected against DAT and SL-I. Their evolution has a positive correlation with bacillary concentration in tissues.

Evaluation of the VITAL (bioMérieux) automated blood culture system using blind subculture

OBJECTIVE

This study was performed to determine the ability of the VITAL system to detect and allow recovery of microorganisms that are difficult to grow, such as Brucella spp., yeasts, or anaerobes, as well as to determine the need for blind subcultures after the incubation period.

METHODS

A prospective evaluation of the system was performed, and 8247 blood culture bottles were processed. The standard was blind subculture from all the bottles after 5 days of incubation.

RESULTS

There were 3.2% false-positive and 0.6% false-negative results (72% of clinical importance). The system sensitivity for yeasts was 41%. The mean time for detection of Neisseria meningitidis was 31.9 +/- 2.8 h, for Brucella spp. 119.7 +/- 2 h, and for yeast 51.5 +/- 27.8 h.

CONCLUSIONS

The VITAL system poses has serious difficulties in the detection of N. meningitidis, Brucella spp., yeast and methicillin- and aminoglycoside-resistant Staphylococcus aureus (MARSA). The low system sensitivity for yeast detection makes the blind subculture necessary after the incubation period.

Assessment of a new test to detect Legionella urinary antigen for the diagnosis of Legionnaires' Disease

Given that the rate of mortality by Legionella pneumonia increases in incorrectly treated patients, rapid diagnosis and early antibiotic treatment are needed. We have assessed the performance of a new enzyme immunoassay (EIA) test (Bartels Inc. Trinity Biotech Company, Wicklow, Ireland) to detect Legionella pneumophila antigen in urine comparing it to Binax EIA (Binax, Portland, Maine). We also evaluated the capability of both EIAs to detect extracted soluble antigens of Legionella strains. Using nonconcentrated urine samples (NCU) the sensitivity of Bartels EIA was 74.1% (66/89) and the sensitivity of Binax EIA was 51.7% (46/89). The sensitivity of both EIA tests were 91.5% (54/59) using concentrated urine samples (CU). Specificity of both EIA tests was 100% in NCU and CU. Bartels EIA was able to detect all serogroup L. pneumophila antigens, achieving a higher sensitivity in the case of L. pneumophila serogroup 1 soluble antigen. The new EIA was found to be a useful test for the rapid diagnosis of Legionella pneumonia, being a better alternative to the Binax EIA if NCU is used.

Prospective follow-up of Epstein-Barr virus load in adult kidney transplant recipients by semiquantitative polymerase chain reaction in blood and saliva samples

The aim of the study presented here was to set up and standardize a semiquantitative polymerase chain reaction method for monitoring Epstein-Barr virus (EBV) DNA levels in blood and saliva samples from transplant recipients and to determine the value of these levels as an early marker for the development of post-transplant lymphoproliferative disorders. EBV DNA load was prospectively measured in 53 adult kidney transplant recipients. Results were correlated with clinical features and degree of immunosuppression. Healthy blood donors and patients with infectious mononucleosis were used as controls. Levels higher than 500 EBV DNA copies/75,000 peripheral blood mononuclear cells were found in all patients with infectious mononucleosis and in all patients with post-transplant lymphoproliferative disorder but in only 7.5% of transplant recipients without that complication.

Usefulness of adding multiplex nested-polymerase chain reaction assay of cerebrospinal fluid samples to routine diagnostic testing for herpesvirus encephalitis

The present study was conducted to assess the usefulness of adding the multiplex nested-polymerase chain reaction assay of cerebrospinal fluid samples to routine diagnostic testing for herpesvirus encephalitis and to monitor the efficacy of therapy. Cerebrospinal fluid samples from 45 patients with presumed herpesvirus encephalitis were tested for herpes simplex virus, varicella-zoster virus, cytomegalovirus, human herpesvirus 6, and Epstein-Barr virus. Ten of the 45 patients were positive for a virus using the polymerase chain reaction assay: herpes simplex virus (n=5), Epstein-Barr virus (n=3), and herpes simplex virus plus the Epstein-Barr virus (n=2). Cerebrospinal fluid from two patients who had undergone acyclovir therapy gave negative results. Analysis of cerebrospinal fluid by multiplex polymerase chain reaction can be useful for establishing an accurate diagnosis and as a marker of the efficacy of therapy.

Rapid detection of several mycobacterial species using a polymerase chain reaction reverse hybridisation assay

The ability of a polymerase-chain-reaction-based technique combined with a reverse hybridisation line-probe assay to detect and identify eight of the most clinically significant mycobacterial species directly from cultures in liquid medium was evaluated. The line-probe assay allows simultaneous identification of eight different mycobacterial species. Ninety-seven mycobacterial strains belonging to 22 different species were evaluated. All strains were previously inoculated into MB/BacT bottles (Organon Teknika, USA). The sensitivity and specificity of the test when applied on positive MB/BacT liquid cultures containing isolates from mycobacterial species included as specific probes on the line-probe assay strip was 100% and 100%, respectively. These results further support the potential clinical usefulness of this technique in the diagnosis of mycobacterial infections.

Towards a 'human-like' model of tuberculosis: intranasal inoculation of LPS induces intragranulomatous lung necrosis in mice infected aerogenically with Mycobacterium tuberculosis

It is well known that one of the differences between murine and human tuberculosis is the lack of intragranulomatous necrosis in the former. The aim of this study was to create a feasible and reproducible model of an experimental model of murine tuberculosis in which this necrosis should be present. Considering the Shwartzman reaction as a possible explanation for intragranulomatous necrosis in human tuberculosis, C57Bl/6 mice, infected aerogenically with a virulent strain of Mycobacterium tuberculosis, were intranasally inoculated with lipopolysaccharide (LPS) on day 19 postinfection (p.i.). Twenty-four hours later, neutrophils infiltrated the lung parenchyma in a significant level, and 10 days after necrosis could be detected in the centres of primary granulomas, that showed scanty macrophages and large amounts of collagen on an eosinophilic background. On the other hand, a significant decrease in the concentration of colony forming units (CFU) could be appreciated 24 h after the LPS inoculation. Afterwards, nonbronchogenic spreading of granulomas increased and higher levels of interferon (IFN)-gamma mRNA were detected. These results lend support to the Shwartzman reaction as the origin of the intragranulomatous necrosis in the M. tuberculosis infection, and provides a useful tool to improve experimental murine models in tuberculosis.

Detection of Streptococcus pneumoniae antigen by a rapid immunochromatographic assay in urine samples

STUDY OBJECTIVES

Evaluation of a newly available rapid (15 min) immunochromatographic membrane test (ICT) to detect Streptococcus pneumoniae in urine samples, in order to assess its utility in the diagnosis of bacteremic and nonbacteremic pneumococcal pneumonia.

DESIGN

Retrospective study.

SETTING

We studied urine samples from 51 patients with bacteremic and nonbacteremic pneumonia due to S pneumoniae diagnosed by blood culture and pneumococcal polysaccharide capsular antigen detection by counterimmunoelectrophoresis in urine samples, 16 patients with probable pneumococcal pneumonia, 71 patients with nonpneumococcal pneumonia, and 16 patients with pneumonia but no pathogen identified. Urine samples were collected and frozen at - 20 degrees C until used. The ICT test was performed following the instructions of the manufacturer.

MEASUREMENTS AND RESULTS

S. pneumoniae antigen was detected in 41 of 51 patients with pneumococcal pneumonia (80.4%); results were positive in 23 of 28 bacteremic cases (82.1%) and in 18 of 23 nonbacteremic cases (78.3%). From patients with a diagnosis of presumptive pneumococcal pneumonia, antigen was detected in seven urine samples (43.7%) and also in one case of the 16 patients with pneumonia but no pathogen identified. The specificity of the ICT test was 97.2%.

CONCLUSION

The ICT assay is a valuable tool for the diagnosis of pneumococcal pneumonia, especially for the nonbacteremic cases.

Assessment of in-vitro efficacy of 1% Virkon against bacteria, fungi, viruses and spores by means of AFNOR guidelines

Peroxygenic acid, under the brand name Virkon, has unleashed great debate following contradictory reports of its efficacy and spectrum of activity. The aim of this study was to test the biocidal activity of the compound against 10 different micro-organisms, following standard in-vitro test procedures. Bactericidal, fungicidal and sporicidal activities were determined using quantitative suspension and germ carrier tests and virucidal activity was assessed using a simple dilution suspension test, following the Association Française de Normalisation (AFNOR) guidelines. One percent Virkon demonstrated bactericidal activity against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Enterococcus hirae and Mycobacterium smegmatis in the suspension test and against P. aeruginosa, E. coli, S. aureus and E. hirae in the carrier test. One percent Virkon showed virucidal activity against poliovirus in the suspension test. However, this concentration did not comply with sporicidal and fungicidal activity guidelines. In conclusion, 1% Virkon is effective only against vegetative bacteria, yeasts and viruses, and should therefore be considered a low-level disinfectant.