Internal quality control samples for water bacteriology

A method is described for the preparation and application of a bacteriological quality control system for use with tests for plate counts and the enumeration of indicator organisms in water. Statistical limits are obtained and control charts prepared which are analagous to those used in analytical chemistry and clinical biochemistry laboratories. This approach has been applied successfully in this laboratory but needs to be tested more widely. Such numerically-based systems have seldom been attempted in microbiology, especially where multiple organisms have been included for the simultaneous control of several tests.     

The use of latex beads in external quality assurance and internal quality control for routine semen analysis

The usefulness of latex beads of defined concentration was assessed as a substitute for sperm in the performance of External Quality Assurance (EQA) and Internal Quality Control (IQC) of semen analysis. Within the EQA programme, mean±SEM bias (%) was significantly reduced in 2007 compared to 2002 for both specialist (6.0%±5.4% vs. 55.0%±5.9%) and non-specialist (18.4%±5.9% vs. 90.9%±13.4%) laboratories (both p<0.0001), indicating improved accuracy over time. Within the IQC programme, the beads were used in the appraisal of two scientists, one experienced and one inexperienced, against a known standard. Beads were also used to calibrate eleven counting chambers, resulting in one old chamber being discarded due to its poor performance. The present study has shown that the use of a defined concentration of beads is an excellent adjunct to IQC and EQA programmes enabling the performance of both people and equipment to be assessed in an objective manner.     

Evaluation of an internal positive control for Cryptosporidium and Giardia testing in water samples

AIMS: An internal positive control for Cryptosporidium and Giardia monitoring was evaluated for use in routine water monitoring quality control. The control, known as ColorSeed C&G (BTF Pty Ltd, Sydney, Australia), is a suspension containing exactly 100 Cryptosporidium oocysts and 100 Giardia cysts that have been modified by attachment of Texas Red to the cell wall, allowing them to be differentiated from unmodified oocysts and cysts. The control enables recovery efficiencies to be determined for every water sample analysed. METHODS AND RESULTS: A total of 494 water samples were seeded with ColorSeed C&G and with unlabelled Cryptosporidium and Giardia and then analysed. Additionally, the robustness of the ColorSeed labelling was challenged with various chemical treatments. Recoveries were significantly lower for the ColorSeed Texas Red labelled Cryptosporidium and Giardia than recoveries of unlabelled Cryptosporidium and Giardia. However, the differences in recoveries were small. On average ColorSeed Cryptosporidium recoveries were 3.3% lower than unlabelled Cryptosporidium, and ColorSeed Giardia recoveries were 4% lower than unlabelled Giardia. CONCLUSIONS: ColorSeed C&G is suitable for use as an internal positive control for routine monitoring of both treated and raw water samples. SIGNIFICANCE AND IMPACT OF THE STUDY: The small differences in recoveries are unlikely to limit the usefulness of ColorSeed C&G as an internal positive control. The ColorSeed labelling was found to be robust after different treatments.     

LENTICULE discs provide a homogenous format for external quality assessment samples: a comparison with freeze-dried samples for shellfish microbiology

AIMS: The aim was to compare the variability in Escherichia coli enumeration data and detection of Salmonella spp. between four samples of LENTICULE discs and freeze-dried samples for the Health Protection Agency's External Quality Assessment (EQA) scheme for shellfish microbiology. METHODS AND RESULTS: Four samples of known but undisclosed microbiological content were dispatched in both freeze-dried and LENTICULE disc formats to 57 participating laboratories in 20 countries. Participants examined samples using their routine methods for the most probable number (MPN) of E. coli per 100 g and the presence/absence of Salmonella spp. There was no significant difference between the Food and Environmental Proficiency Testing Unit and participating laboratories for E. coli and Salmonella spp. results. There were significantly less outlying results using the LENTICULE discs than freeze-dried sample format and equivalent or less variance for the former for E. coli MPN. There was no significant difference between LENTICULE discs and freeze-dried samples for the presence/absence of Salmonella spp. CONCLUSIONS: Overall the results indicated that there was equivalent or less variance in results for the LENTICULE discs than for freeze-dried samples, therefore LENTICULE discs are a homogenous and stable matrix for EQA samples. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides validation data for the replacement of freeze-dried samples by LENTICULE discs for the Health Protection Agency Shellfish EQA Scheme.     

Isotope labeled internal standards (ILIS) as a basis for quality control in clinical studies using plasma samples

For clinical proteomic studies, the quality of the biofluid samples such as human blood plasma is extremely important. In this study we have investigated the stability of human plasma samples by spiking stable isotope-labeled peptides into the plasma and monitoring their degradation under different storage conditions. FPA-1, C4A and C3f were synthesized with isotopically labeled amino acids, and used as reference peptides. The mixture of internal calibrants was spiked into plasma at the starting point of investigation, mimicking the time of collection for future biobanking efforts, and their qualitative and quantitative changes were analyzed over time by using both MALDI-MS (LTQ Orbitrap XL) and nanoLC-ESI-MS (LTQ XL ETD).We have found that all three synthetic peptides were stable in plasma at ? 20 and ? 80 °C during the examined 2-month period. However, different proteolytic degradation profiles of the peptides were observed at room temperature. We anticipate that the use of these isotope-labeled peptides as internal standards (ILIS) provides a quality control for long-term storage and proteomic plasma analysis.     

Recommendations for the routine sampling of diatoms for water quality assessments in Europe

Many methods for using diatoms for routine monitoring of water quality have been developed in Europe and, in some countries, these are being used to enforce environmental legislation. In order to facilitate their wider use, particularly with respect to European Union legislation, steps are being taken to harmonize methodology. In this paper, the principles and practice of sampling are described in relation to the main habitat types encountered in Europe. Although details of methods and sampling programmes have to be tailored to particular circumstances and the overall objectives of the monitoring, a number of generalizations can be made. Where available, rocks and other hard surfaces are the preferred substrates and methods for sampling these are described. If such substrata are not available, then introduced ('artificial') substrata have many applications. Various types of introduced substrata can be used successfully, so long as some basic precautions are described. Other types of substrata such as macrophytes and macroalgae may also be useful under certain circumstances, although there is less consensus in the literature on the most appropriate methods, and of the validity of comparisons between indices computed from epiphytic and epilithic communities. When designing surveys, it is recommended that as far as possible, extremes of non-water quality factors (e.g. shade, current speed, etc) are avoided, unless these are characteristic of the system under investigation. Detailed guidelines for sampling epilithon are described. Along with the recommendations for sampling other substrata, it is hoped that these provide a framework that can be adapted to most river types in Europe. This revised version was published online in June 2006 with corrections to the Cover Date.     

External quality assessment in water microbiology: statistical analysis of performance

H.E. TILLETT, N.F. LIGHTFOOT AND S. EATON. 1993. A UK-based scheme of water microbiology assessment requires participants to record counts of relevant organisms. Not every sample will contain the target number of organisms because of natural variation and therefore a range of results is acceptable. Results which are tail-end (i.e. at the extreme low or high end of this range) could occasionally be reported by any individual laboratory by chance. Several tail-end results might imply a laboratory problem. Statistical assessment is done in two stages. A non-parametric test of the distribution of tail-end counts amongst laboratories is performed (Cochran's Q) and, if they are not random, then observed and expected frequencies of tail-end counts are compared to identify participants who may have reported excessive numbers of low or high results.
Analyses so far have shown that laboratories find high counts no more frequently than would be expected by chance, but that significant clusters of low counts can be detected among participants. These findings have been observed both in short-term and in long-term assessments, thus allowing detection of new episodes of poor performance and intermittent problems.
The analysis relies on an objective definition of tail-end results. Working definitions are presented which should identify poor performance in terms of microbiological significance, and which allow fair comparison between membrane-filtration and multiple-tube techniques. Smaller differences between laboratories, which may be statistically significant, will not be detected. Different definitions of poor performance could be incorporated into future assessments.     

Stability test of six enzymes for internal quality control

The daily quality control for the determination of the catalytic activity concentrations of enzymes is an important aspect in clinical chemistry. Instead of the expensive, commercially available control sera, we have looked for a simple, reliable and cheap method for the quality control of enzyme determinations. Commercially available enzymes were suspended in an albumin solution and ampoules were filled with 1.0 ml of these various solutions. The ampoules were stored at 4 degrees C or -20 degrees C. Once a week, during 10 months, catalytic activities of these enzyme-albumin solutions were determined together with the same activities in freshly reconstituted control sera. Aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, creatine kinase and gamma-glutamyltransferase were determined at 30 degrees C according to well-described methods. alpha-Amylase was determined with the Phadebas method at 37 degrees C. Except for creatine kinase, the stability and reliability of these enzyme solutions are fully comparable with control sera during the experimental period. The catalytic activity concentration of creatine kinase decreased slowly during the 10 months. The enzyme solutions react in the same manner as commercial test sera on changes in the reaction conditions for the enzyme determinations. The conclusion seems justified that these enzyme solutions can be used for the daily quality control of the enzyme determinations instead of control sera.     

An aspect of microbiology research in New Zealand: the pursuit of water quality

World Journal of Microbiology and Biotechnology - The problems in monitoring and assessing water quality that must be overcome most urgently are associated with the development of appropriate,...     

An aspect of microbiology research in New Zealand: the pursuit of water quality

The problems in monitoring and assessing water quality that must be overcome most urgently are associated with the development of appropriate, simple methods for detecting living but not necessarily growing indicator and pathogenic microorganisms. These methods will allow us to assess and monitor water quality, understand the survival and distribution of microbial contaminants and truly assess the health implications of their presence in water.     

A comprehensive internal quality control system for a large cytology laboratory

The British Columbia Cervical Cytology Program is operated through the Central Laboratory at the Cancer Control Agency in Vancouver and processes all of the gynecologic Papanicolaou smears collected by 3,200 physicians throughout the province of British Columbia. The laboratory receives approximately 2,400 smears per day, and the program currently processes in excess of 500,000 smears annually. This article describes the methods that have been developed for ensuring that adequate quality control is present in the screening and interpretation of half a million smears per year, both at the cytotechnologist and at the cytopathologist level. The results of the quality control program, which was considerably modified in 1985, are also presented. The modified program shows a significant improvement in the number of undercalled and overcalled cases detected in two comparable six-month periods.     

Establishment of laboratory quality control indicators for NAT on blood donors' samples

In order to establish and screen nucleic acid test (NAT) quality control indicators for blood donor samples, C_T value of each test item were detected by NAT, internal and external quality controls, the number of unsuccessful mixed samples, the split positive rate, the rate of detection efficiency, and the equipment failure rate were collected. The "instant method" is used to establish the Levey-Jennings quality control chart, the mixed test positive rate, the rate of unqualified sample. Possion distribution is used to establish the quality control chart, and it is easily to operate and monitor NAT effectively. The results displayed that quality control charts were established, including unqualified sample Possion distribution quality control chart, the rate of equipment failure quality control chart, the failure rate of reagent batch and inefficient quality control chart, test result positive of Possion distribution quality control chart, quality control charts of NAT positive Possion distribution probability, the rate of split positive quality control charts, quality control charts of unsuccessful mixed samples, quality control chart of reagents effective rate, internal quality control chart, correctness, and NAT qualitative quality control chart. The study established quality control indicators throughout the whole NAT process, which were able to effectively improve NAT quality control and the efficacy of laboratory management.     

An update on the routine application of MALDI-TOF MS in clinical microbiology

Introduction: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has entered clinical diagnostics and is today a generally accepted and integral part of the workflow for microbial identification. MALDI-TOF MS identification systems received approval from national and international institutions, such as the USA-FDA, and are continuously improved and adopted to other fields like veterinary and industrial microbiology. The question is whether MALDI-TOF MS also has the potential to replace other conventional and molecular techniques operated in routine diagnostic laboratories.

Areas covered: We give an overview of new advancements of mass spectral analysis in the context of microbial diagnostics. In particular, the expansion of databases to increase the range of readily identifiable bacteria and fungi, the refined discrimination of species complexes, subspecies, and types, the testing for antibiotic resistance or susceptibility, progress in sample preparation including automation, and applications of other mass spectrometry techniques are discussed.

Expert opinion: Although many new approaches of MALDI-TOF MS are still in the stage of proof of principle, it is expectable that MALDI-TOF MS will expand its role in the clinical microbiology laboratory of the future. New databases, instruments and analytical software modules will continue to be developed to further improve diagnostic efficacy.     

Method for small routine laboratories for the detection of satratoxins in straw samples

A method is described for thin-layer chromatographic analysis of field samples for satratoxins G and H, theStachybotrys toxins most soluble under physiological circumstances and representing the majority ofStachybotrys atra produced toxins. Besides brine shrimp bio-assay, the conversion of these macrocyclic trichothecenes to verrucarol is used to support their identification.     

Use of the ThinPrep Imaging System for internal quality control of cervical cytology

T. Heard, A. Chandra, G. Culora, S.S. Gupta, A. Herbert and M. Morgan
Use of the ThinPrep Imaging System for internal quality control of cervical cytology Objective: To audit the use of the ThinPrep Imaging System (TIS) for internal quality control (IQC) in the place of rapid review (RR), and to compare its performance with routine primary screening. Method: During 9 months, 16 462 ThinPrep slides were processed by TIS. Slides were initially reviewed using the TIS review scope, as recommended by the manufacturer: 22 fields of view were observed and, if considered abnormal, a full microscopic review was conducted using the review scope. Different biomedical scientists (BMSs), working on each procedure in rotation, performed batches of TIS‐assisted quality control and routine primary screening independently on unmarked slides. Any slides with abnormalities detected by either method were referred to a consultant pathologist or advanced BMS practitioner for a final report. TIS results were compared with both previous records of RR and routine primary screening carried out on the same slides. We used the UK terminology in which ‘dyskaryosis’ is equivalent to squamous intraepithelial lesion (SIL) and borderline to atypical (including squamous and glandular cells). Results: TIS preview detected significantly more high‐grade dyskaryosis compared with RR during the previous 4 years: 2.0–4.2 compared with 0.1–1.8 detected per 1000 slides (P = 0.0001). TIS and routine screening were equivalent in sensitivity and specificity for the final cytology result, but BMSs were significantly more likely to classify slides as dyskaryotic rather than borderline when using TIS compared with routine screening. Referrals for potentially high‐grade abnormalities detected by TIS‐assisted IQC alone found 28 biopsies of at least cervical intraepithelial neoplasia grade 2 (CIN2+), whereas 15 CIN2+ biopsies were found on routine screening but missed using TIS. There was no significant change in the rates of inadequate tests, high‐ or low‐grade cytological abnormalities, or positive predictive value for CIN2+ when TIS was in use. Conclusions: Screening with TIS was more sensitive than RR for IQC, providing a rescreening method equivalent to routine primary screening in overall accuracy.     

VFEU water quality control in STS-95 mission.

In STS-95 Space Shuttle mission, an aquatic animal research facility, Vestibular Function Experiment Unit (VFEU), was flown to perform neurobiological experiment with marine fish, oyster toadfish. For this purpose, we have developed a sea water purification system using highly active nitrifying bacteria at low temperature. With this system, the water quality in the VFEU was maintained in sufficient condition to keep the toadfish in healthy state for 9 days of the mission. This report summarizes the efficiency of the filter system based on the results from pre-flight bacterial preparation, water analysis of samples taken during flight, and the post-flight analysis of the bacterial filter.     

An assessment of partial rescreening as an internal quality control method for cervical smears

Partial screening was performed on 10 800 cervical smears, comprising 8640 filed negative and unsatisfactory smears and 2160 newly received smears prior to conventional screening. Each slide was screened for 30 s and those considered abnormal were reviewed by standard screening. Partial screening led to the detection of 27 additional infections and 44 additional cytological abnormalities. These detection rates are better than those obtained with the traditional method of rescreening only a proportion of smears. Amongst the smears partially screened before conventional screening, partial screening detected 37-66% of infections and 22-71% of cytological abnormalities. We recommend the use of partial rescreening of all negatively reported smears as a method of internal quality control in cervical cytology laboratories.     

Application of orthogonal light scattering for routine screening of lymphocyte samples

Orthogonal and forward light-scattering properties of lymphocytes were measured from patients with different lymphocytic diseases in order to determine the potential value of light scattering as a screening device. Monitoring of orthogonal light scattering of lymphocytes of a B-cell chronic lymphocytic leukemia patient during splenic irradiation (SI) revealed the selective decrease of malignant cells and the fact that the major part of the residual lymphocytes were cytotoxic lymphocytes. By combining forward and orthogonal light scattering it was shown that lymphocytes from a patient with T gamma lymphocytosis were abnormal. Orthogonal light scattering also showed an increase in cytotoxic lymphocytes in a patient with mononucleosis infectiosa and in a splenectomized patient. Orthogonal light scattering of lymphocyte subpopulations showed that the leu8+ population of a patient with mononucleosis infectiosa was bidisperse. For elderly donors the occurrence of CD3+, CD4+, CD8+, and HNK-1+ lymphocytes with a large orthogonal light scattering varied considerably. The CD8+ lymphocytes of these donors consisted mainly of cytotoxic lymphocytes. These results show that determination of light-scattering properties of lymphocytes may yield important diagnostic information and can indicate when further investigation of the lymphocytes by means of immunofluorescence is necessary.