Accuracy of quantitative viral secondary standards: a re-examination

Interlaboratory agreement of viral load assays depends on the accuracy and uniformity of quantitative calibrators. Previous work demonstrated poor agreement of secondary cytomegalovirus (CMV) standards with nominal values. This study re-evaluated this issue among commercially produced secondary standards for both BK virus (BKV) and CMV, using digital polymerase chain reaction (dPCR) to compare the materials from three different manufacturers. Overall, standards showed an improved agreement compared to prior work, against nominal values in both log10 copies/mL and log10 international unit (IU)/mL, with bias from manufacturer-assigned nominal values of 0.0-0.9 log10 units (either copies or IU)/mL. Standards normalized to IU and those values assigned by dPCR rather than by real-time PCR (qPCR) showed better agreement with nominal values. The latter reinforces prior conclusions regarding the utility of using such methods for quantitative value assignment in reference materials. Quantitative standards have improved over the last several years, and the remaining bias from nominal values might be further reduced by universal implementation of dPCR methods for value assignment, normalized to IU.

IMPORTANCE

Interlaboratory agreement of viral load assays depends on accuracy and uniformity of quantitative calibrators. Previous work, published in JCM several years ago, demonstrated poor agreement of secondary cytomegalovirus (CMV) standards with nominal values. This study re-evaluated this issue among commercially produced secondary standards for both BK virus (BKV) and CMV, using digital polymerase chain reaction (dPCR) to compare the materials from three different manufacturers. Overall, standards showed an improved agreement compared to prior work, against nominal values, indicating a substantial improvement in the production of accurate secondary viral standards, while supporting the need for further work in this area and for the broad adaption of international unit (IU) as a reporting standard for quantitative viral load results.

A prospective bacterial whole-genome-sequencing-based surveillance programme for comprehensive early detection of healthcare-associated infection transmission in paediatric oncology patients

BACKGROUND

Bacterial whole-genome sequencing (WGS) and determination of genetic relatedness is an important tool for investigation of epidemiologically suspected outbreaks.

AIM

This prospective cohort study evaluated a comprehensive, prospective bacterial WGS-based surveillance programme for early detection of transmission of most bacterial pathogens among patients at a paediatric oncology hospital.

METHODS

Cultured bacterial isolates from clinical diagnostic specimens collected prospectively from both inpatient and outpatient encounters between January 2019 and December 2021 underwent routine WGS and core genome multi-locus sequence typing to determine isolates' relatedness. Previously collected isolates from January to December 2018 were retrospectively analysed for identification of prior or ongoing transmission. Multi-patient clusters were investigated to identify potential transmission events based on temporal and spatial epidemiological links and interventions were introduced.

FINDINGS

A total of 1497 bacterial isolates from 1025 patients underwent WGS. A total of 259 genetically related clusters were detected, of which 18 (6.9%) multi-patient clusters involving 38 (3.7%) patients were identified. Sixteen clusters involved two patients each, and two clusters involved three patients. Following investigation, epidemiologically plausible transmission links were identified in five (27.8%) multi-patient clusters. None of the multi-patient clusters were suspected by conventional epidemiological surveillance.

CONCLUSION

Bacterial WGS-based surveillance for early detection of hospital transmission detected several limited multi-patient clusters that were unrecognized by conventional epidemiological methods. Genomic surveillance helped efficiently focus interventions while reducing unnecessary investigations.

Matrix Matters: Assessment of Commutability among BK Virus Assays and Standards

Quantitative testing of BK virus (BKPyV) nucleic acid has become the standard of care in transplant patients. While the relationship between interassay harmonization and commutability has been well characterized for other transplant-related viruses, it has been less well studied for BKPyV, particularly regarding differences in commutability between matrices. Here, interassay agreement was evaluated among six real-time nucleic acid amplification tests (NAATs) and one digital PCR (dPCR) BKPyV assay. Differences in the commutability of three quantitative standards was examined across all assays using a variety of statistical approaches. Panels, including 40 samples each of plasma and urine samples previously positive for BKPyV, together with one previously negative plasma sample and four previously negative urine samples, were tested using all assays, with each real-time NAAT utilizing its usual quantitative calibrators. Serial dilutions of WHO, National Institute for Standards and Technology (NIST), and commercially produced (Exact/Bio-Rad) reference materials were also run by each assay as unknowns. The agreement of the clinical sample values was assessed as a group and in a pairwise manner. The commutability was estimated using both relativistic and quantitative means. The quantitative agreement across assays in the urine samples was within a single log10 unit across all assays, while the results from the plasma samples varied by 2 to 3 log10 IU/mL. The commutability showed a similar disparity between the matrices. Recalibration using international standards diminished the resulting discrepancies in some but not all cases. Differences in the sample matrix can affect the commutability and interassay agreement of quantitative BKPyV assays. Differences in commutability between matrices may largely be due to factors other than those such as amplicon size, previously described as important in the case of cytomegalovirus. Continued efforts to standardize viral load measurements must address multiple sources of variability and account for differences in assay systems, quantitative standards, and sample matrices.

Accuracy of Broad-Panel PCR-Based Bacterial Identification for Blood Cultures in a Pediatric Oncology Population

Bloodstream infections are a major cause of morbidity and mortality and result in significant costs to health care systems. Rapid identification of the causative agent of bloodstream infections is critical for patient treatment and improved outcomes. Multiplex PCR systems that provide bacterial identification directly from the blood culture bottle allow for earlier detection of pathogens. The GenMark Dx ePlex blood culture identification (BCID) panels have an expanded number of targets for both identification and genotypic markers of antimicrobial resistance. The performance of the ePlex BCID Gram-negative (GN) and Gram-positive (GP) panels were evaluated in a predominantly pediatric oncology population. A total of 112 blood cultures were tested by the ePlex BCID GN and GP panels and results were compared to those from standard-of-care testing. Accuracy for on-panel organisms was 89% (CI, 76% to 95%) for the Gram-positive panel, with four misidentifications and one not detected, and 93% (CI, 82% to 98%) for the Gram-negative panel, with two misidentifications and one not detected. The results showed good overall performance of these panels for rapid, accurate detection of bloodstream pathogens in this high-risk population. IMPORTANCE Bloodstream infections are a major cause of morbidity and mortality and result in significant costs to health care systems. Rapid identification of the causative agent of bloodstream infections is critical for patient treatment and improved outcomes. Multiplex PCR systems that provide bacterial identification directly from the blood culture bottle allow for earlier characterization of pathogens. The GenMark Dx ePlex blood culture identification (BCID) panels, recently cleared by the FDA, have an expanded number of targets for both identification and resistance, much larger than other, automated, broad-panel PCR assays. The performance of the ePlex BCID Gram-negative and Gram-positive panels was evaluated in a predominantly pediatric oncology population, providing a unique look at its performance in a high-risk group, where rapid diagnostic information for bloodstream infections could be of particular value for clinical care providers.

Infection-related complications during treatment for childhood acute lymphoblastic leukemia

Background

Comprehensive studies on neutropenia and infection-related complications in patients with acute lymphoblastic leukemia (ALL) are lacking.

Patients and methods

We evaluated infection-related complications that were grade ≥3 on National Cancer Institute's Common Terminology Criteria for Adverse Events (version 3.0) and their risk factors in 409 children with newly diagnosed ALL throughout the treatment period.

Results

Of the 2420 infection episodes, febrile neutropenia and clinically or microbiologically documented infection were seen in 1107 and 1313 episodes, respectively. Among documented infection episodes, upper respiratory tract was the most common site (n = 389), followed by ear (n = 151), bloodstream (n = 147), and gastrointestinal tract (n = 145) infections. These episodes were more common during intensified therapy phases such as remission induction and reinduction, but respiratory and ear infections, presumably viral in origin, also occurred during continuation phases. The 3-year cumulative incidence of infection-related death was low (1.0±0.9%, n = 4), including 2 from Bacillus cereus bacteremia. There was no fungal infection-related mortality. Age 1-9.9 years at diagnosis was associated with febrile neutropenia (P = 0.002) during induction and febrile neutropenia and documented infection (both P < 0.001) during later continuation. White race was associated with documented infection (P = 0.034) during induction. Compared with low-risk patients, standard- and high-risk patients received more intensive therapy during early continuation and had higher incidences of febrile neutropenia (P < 0.001) and documented infections (P = 0.043). Furthermore, poor neutrophil surge after dexamethasone pulses during continuation, which can reflect the poor bone marrow reserve, was associated with infections (P < 0.001).

Conclusions

The incidence of infection-related death was low. However, young age, white race, intensive chemotherapy, and lack of neutrophil surge after dexamethasone treatment were associated with infection-related complications. Close monitoring for prompt administration of antibiotics and modification of chemotherapy should be considered in these patients.

Risk factors for hemorrhagic cystitis in pediatric allogeneic hematopoietic stem cell transplant recipients

BACKGROUND

Hemorrhagic cystitis (HC) results in significant morbidity among hematopoietic stem cell transplant (HSCT) recipients. Several potential causes for HC have been postulated, including viral infection, but definitive evidence is lacking, particularly in pediatric HSCT patients.

METHODS

Ninety pediatric HSCT recipients were prospectively tested on a weekly basis for adenovirus (ADV) and BK virus (BKV) by quantitative real-time polymerase chain reaction in blood and urine samples. Results were correlated with the occurrence of grade II-IV HC. The odds ratio (OR) of HC (95% confidence interval) for BKV ≥1 × 10(9) copies/mL of urine was 7.39 (1.52, 35.99), with a P-value of 0.013. Those with acute graft-versus-host disease (aGVHD) also had higher odds of developing HC, with an OR of 5.34. Given a 20% prevalence rate of HC, positive and negative predictive values of 29% and 95% were seen with a cutoff of 10(9) copies/mL.

RESULTS

BK viremia did not reach significance as a risk factor for development of HC (P = 0.06). Only 8 patients showed ADV viruria and 7 showed ADV viremia; all had low viral loads and 4 had no evidence of HC.

CONCLUSION

HC in pediatric HSCT is correlated most strongly to elevated urinary viral load of BKV and to aGVHD, but less strongly to BK viremia.

Early infections after autologous hematopoietic stem cell transplantation in children and adolescents: the St. Jude experience

INTRODUCTION

Advances in autologous hematopoietic stem cell transplantation (HSCT) over the past 20 years may have had an impact on the morbidity and mortality associated with infections post transplant.

PATIENTS AND METHODS

We sought to retrospectively analyze the epidemiology of the first episode of bacterial, fungal, viral, or parasitic infections 0-30 days post transplant in a cohort of 320 children and adolescents who underwent autologous HSCT in a single institution, between 1990 and 2009 for solid tumors or lymphoma, and in 65 children transplanted for acute leukemia during the same period.

RESULTS

Infections occurred in 66 (21%) patients with solid tumors or lymphoma. Bacterial infections occurred in 33 (10%) including bacteremia in 23 (7%), and viral infections in 34 (11%) patients. Gram-positive bacterial infections were more prevalent than gram-negative bacterial infections (P = 0.03). Infections caused by fungal or parasitic pathogens were uncommon. The decade when transplant was performed (1990-1999 vs. 2000-2009) had no impact on the incidence of bacterial (P = 0.41) or viral (P = 0.47) infection. Between 1990 and 1999, a total of 60 (92%) children were transplanted for leukemia, and 5 (8%) in the 2000-2009 period (P < 0.0001). Infections occurred in 32 (49%) patients. Bacterial (P = 0.004), candidal (P = 0.003), and herpes simplex viral (P = 0.03) infections were more common in patients transplanted for leukemia. In patients transplanted for leukemia, 3 deaths occurred attributed to infection, all before 2000.

CONCLUSION

Changes in epidemiology of infection are likely a result of decline in autologous transplantation for childhood leukemia in the recent era. Autologous transplantation for solid tumors or lymphoma was not associated with mortality from early infections at our institution.

Inhibition of primary clinical isolates of human parainfluenza virus by DAS181 in cell culture and in a cotton rat model

DAS181 is a novel drug in development for the treatment of influenza as well as human parainfluenza viruses (hPIVs). Previous studies demonstrated that DAS181 inhibited laboratory strains of hPIV, but no tests were conducted with primary clinical isolates of hPIV. To fill this gap, we studied six primary isolates including hPIV-2 and hPIV-3. First tests showed that the amplification of all viruses in vitro was reproducibly inhibited with DAS181 drug concentrations ranging between 0.1 and 1nM. An hPIV-3 primary clinical isolate was then tested in a cotton rat model for sensitivity to 0.3-1mg/kg drug treatments. Results showed that virus amplification in the lower respiratory tract was significantly and reproducibly inhibited by drug. Together, experiments demonstrated that DAS181 inhibited primary clinical isolates of hPIV in vitro and in vivo at doses similar to those previously described for inhibition of laboratory hPIV and influenza virus isolates.

Efficacy of intravascular catheter lock solutions containing preservatives in the prevention of microbial colonization

There is little published evidence regarding whether heparin lock solutions containing preservatives prevent catheter-related infections. However, adverse effects from preservative-containing flushes have been documented in neonates, leading many hospitals to avoid their use altogether. Infection control records from 1982 to 2008 at St. Jude Children's Research Hospital (SJCRH) were reviewed regarding the incidence of catheter-related infections and the use of preservative-containing intravenous locks. In addition, the antimicrobial activities of heparin lock solution containing the preservatives parabens (0.165%) or benzyl alcohol (0.9%), and 70% ethanol were examined against Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, Bacillus cereus, Pseudomonas aeruginosa and Candida albicans, and compared with preservative-free saline with and without heparin. Growth was assessed after exposure to test solutions for 0, 2, 4 and 24h at 35 °C. The activities of preservatives were assessed against both planktonic (free-floating) and sessile (biofilm-embedded) micro-organisms using the MBEC Assay. Infection control records revealed two periods of increased catheter-related infections, corresponding with two intervals when preservative-free heparin was used at SJCRH. Heparin solution containing preservatives demonstrated significant antimicrobial activity against both planktonic and sessile forms of all six microbial species. Ethanol demonstrated the greatest antimicrobial activity, especially following short incubation periods. Heparin lock solutions containing the preservatives parabens or benzyl alcohol, and 70% ethanol demonstrated significant antimicrobial activity against both planktonic and sessile micro-organisms commonly responsible for catheter-related infections. These findings, together with the authors' historical infection control experience, support the use of preservatives in intravenous lock solutions to reduce catheter related infections in patients beyond the neonatal period.

Comparison of various blood compartments and reporting units for the detection and quantification of Epstein-Barr virus in peripheral blood

Epstein-Barr virus (EBV) infection is associated with a broad spectrum of disease. While quantification of EBV nucleic acid in the peripheral blood has been demonstrated to be useful for diagnosis and patient care, the optimal sample type and reporting format for such testing remain uncertain. Using quantitative real-time PCR (QRT-PCR), we evaluated EBV in whole blood (WB), peripheral blood mononuclear cells (PBMC), and plasma in 249 samples from 122 patients. In WB and PBMC, results were reported both in viral copies/ml and in copies/microg of total DNA. Trendings of quantitative values over time among the different sample types were compared. The sensitivities of QRT-PCR using WB and that using PBMC did not differ significantly (P = 0.33), and both were more sensitive than plasma alone (P < 0.0001). EBV viral load results from WB and PBMC paired sample types also showed a significant correlation (P < 0.05), as did results reported in copies/ml and copies/microg DNA for both WB and PBMC (R2 > 0.93). EBV viral loads detected using WB and PBMC trended very closely for the few patients who had multiple positive samples available for analysis. WB and PBMC show comparable sensitivities and a close quantitative correlation when assayed for EBV by QRT-PCR. The close correlation between copies/ml and copies/microg DNA also suggests that normalization to cell number or genomic DNA in cellular specimens may not be necessary.

Association between tea ingestion and invasive Bacillus cereus infection among children with cancer

Bacillus cereus is an emerging pathogen that causes invasive disease in immunocompromised hosts. A case-control study, prompted by a clinical case, demonstrated an association between dietary tea ingestion and B. cereus bacteremia. Policies designed to interrupt transmission of this pathogen to susceptible patients should be considered.

Multiplexed, real-time PCR for quantitative detection of human adenovirus

Adenovirus infection is becoming increasingly recognized as a cause of morbidity and mortality in the immunosuppressed patient population. While early detection and quantitation of adenovirus in peripheral blood has been suggested as a means of directing and monitoring antiviral therapy in these patients, few methods have been published, particularly with respect to viral quantitation. A multiplexed real-time PCR assay was developed that can quantitatively detect a wide range of known serotypes of human adenovirus, including all of subgroups A to C. This assay was compared to a qualitative, Southern blot-based PCR assay by using 45 peripheral blood specimens from 16 patients. There was 100% concordance between the two tests in terms of qualitative results. The real-time assay detected adenovirus in patient samples at levels from <200 to 266,681 copies/ml of blood. By using control viral samples, sensitivity was demonstrated to less than 10 copies of viral genome per reaction and quantitative linearity was demonstrated from 10 to 10(6) copies of input viral DNA. Equivalent sensitivity and linearity were demonstrated for 15 different reference serotypes of adenovirus. Eleven other viral serotypes have complete target region sequence homology to one or more of the strains tested. No cross-reactivity was noted with other commonly isolated viral species. Sequence analysis showed no significant homology with any other human pathogens (bacterial or viral). This assay allows rapid, sensitive, and specific quantitation of adenovirus and may have a significant impact on the care of immunocompromised patients at risk for disseminated viral infection.

In situ hybridization for the differentiation of Aspergillus, Fusarium, and Pseudallescheria species in tissue section

Identification of fungi in tissue sections can be difficult. In particular, species of Aspergillus, Fusarium, and Pseudallescheria all appear as septate, branched hyphae. However, their differentiation can have significant clinical implications, as the latter two groups are often resistant to commonly used antifungal agents. In situ hybridization may assist in rapidly distinguishing these organisms in the absence of available culture. Oligonucleotide DNA probes were directed against the 5S, 18S, or 28S rRNA sequences of three groups of fungi with a high degree of specificity for each. Probes were tested on 26 formalin-fixed, paraffin-embedded tissue specimens, each with culture-proven involvement by one of these organisms: Fusarium species, n = 12; Pseudallescheria boydii, n = 5; Aspergillus species, n = 9 ( probe set validated in an earlier study). Accuracy of both ISH and morphology was compared with culture. Morphologic examination (GMS and PAS) showed a greater sensitivity in detecting fungi (100%) as compared with in situ hybridization (84.6%). When detected, however, DNA probes allowed definitive identification of organisms. While there was no ability to distinguish between the three groups of organisms by morphologic features, ISH probes showed 100% positive predictive value (PPV, 19/19 organisms identified correctly). No cross-reactivity was observed when the probes were tested against other genera (100% specificity). Furthermore, the use of ISH allowed the detection of mixed fungal infections involving multiple organism types in two cases, demonstrating another advantage over morphology. In situ hybridization, directed against rRNA sequences, provides a rapid and accurate technique for distinguishing commonly encountered, nonpigmented filamentous fungi in histologic sections. While less sensitive than morphology, ISH is highly accurate and may help to distinguish between organisms that have similar or identical morphologic features by light microscopy.

In situ hybridization for the identification of filamentous fungi in tissue section

Identification of fungi in tissue sections can be difficult because of limited biopsy tissue with only a few organisms present, or mycelial elements may be the only forms present, rendering common organism types indistinguishable from one another. In situ hybridization may assist in the rapid and accurate identification of such fungi. In this study, DNA probes were directed against the 5S or 18S ribosomal RNA sequences of three groups of fungi with a high degree of specificity for each. Two of the three, Aspergillus and Zygomycetes species, are usually seen in tissue purely in their hyphal forms. The third, Candida species is seen less commonly as predominantly mycelial elements. Probes were tested on 61 formalin-fixed, paraffin-embedded tissue specimens, each with culture-proven involvement by one of these organisms (Candida species, n = 21; Aspergillus species, n = 27; Zygomycetes, n = 13). Accuracy of both in situ hybridization (ISH) and morphology, based on the examination of Grocott methanamine silver (GMS)- and periodic acid-Schiff (PAS)-stained slides, was compared with culture. The results showed that morphologic examination (GMS and PAS) showed a slightly greater sensitivity in detecting the presence of fungi (98%) compared with in situ hybridization (95%). DNA probes, however, were more accurate in correctly identifying those organisms present. Although ISH specific probes showed 97% positive predictive value (PPV), examination of GMS-and PAS-stained slides had an 86% PPV when compared with culture-based identification methods. These results show that ISH, directed against ribosomal RNA, provides a rapid and accurate technique for the identification of mycelial fungal organisms in histologic tissue sections. Its primary use lies in the ability to accurately distinguish between organisms that have similar or identical morphologic features by light microscopy.

Direct detection of Legionella species from bronchoalveolar lavage and open lung biopsy specimens: comparison of LightCycler PCR, in situ hybridization, direct fluorescence antigen detection, and culture

We developed a rapid thermocycling, real-time detection (also known as real-time PCR) method for the detection of Legionella species directly from clinical specimens. This method uses the LightCycler (Roche Molecular Biochemicals, Indianapolis, Ind.) and requires approximately 1 to 2 h to perform. Both a Legionella genus PCR assay and Legionella pneumophila species-specific PCR assay were designed. A total of 43 archived specimens from 35 patients were evaluated, including 19 bronchoalveolar lavage (BAL) specimens and 24 formalin-fixed, paraffin-embedded open lung biopsy specimens. Twenty-five of the specimens were culture-positive for Legionella (9 BAL specimens and 16 tissue specimens). BAL specimens were tested by LightCycler PCR (LC-PCR) methods and by a direct fluorescent antibody (DFA) assay, which detects L. pneumophila serogroups 1 to 6 and several other Legionella species. Tissue sections were tested by the two LC-PCR methods, by DFA, by an in situ hybridization (ISH) assay, specifically designed to detect L. pneumophila, and by Warthin-Starry (WS) staining. The results were compared to the "gold standard" method of bacterial culture. With BAL specimens the following assays yielded the indicated sensitivities and specificities, respectively: Legionella genus detection by Legionella genus LC-PCR, 100 and 100%; Legionella genus detection by DFA assay, 33 and 100%; and L. pneumophila detection by L. pneumophila species-specific LC-PCR, 100 and 100%. With open lung biopsy specimens the following assays yielded the indicated sensitivities and specificities, respectively: Legionella genus detection by LC-PCR 68.8 and 100%; Legionella genus detection by DFA assay, 44 and 100%; Legionella genus detection by WS staining, 63 and 100%; L. pneumophila species-specific detection by LC-PCR, 17 and 100%; and L. pneumophila species-specific detection by ISH, 100 and 100%. The analytical sensitivity of both LC-PCR assays was <10 CFU/reaction. LC-PCR is a reliable method for the direct detection of Legionella species from BAL specimens. The Legionella genus LC-PCR assay could be performed initially; if positive, L. pneumophila species-specific LC-PCR could then be performed (if species differentiation is desired). The speed with which the LC-PCR procedure can be performed offers significant advantages over both culture-based methods and conventional PCR techniques. In contrast, for the methods evaluated, culture was the best for detecting multiple Legionella species in lung tissue. WS staining, Legionella genus LC-PCR, and L. pneumophila species-specific ISH were useful as rapid tests with lung tissue.

In situ hybridization for the identification of yeastlike organisms in tissue section

The identification of yeast and yeastlike organisms in tissue sections can be very difficult. Biopsy tissues may be limited, with only occasional organisms present. In addition, several common species have overlapping histologic features. Deoxyribonucleic acid probes were designed to detect both the 18S and 28S ribosomal ribonucleic acid sequences of five fungal organisms with a high degree of specificity for each fungus. Each of these organisms--Blastomyces dermatitidis, Coccidioides immitis, Cryptococcus neoformans, Histoplasma capsulatum, and Sporothrix schenckii--can be manifested histologically as round, yeastlike structures, often within a similar size range. Probes were tested against 98 archived, formalin-fixed, paraffin-embedded tissue specimens, each of which had culture-proved involvement by one of these organisms. Assessment of accuracy was based on the presence of yeastlike organisms in consecutive Grocott's methanemine silver (GMS)-stained tissue sections, and agreement with culture results. The results indicated that GMS had a greater overall sensitivity in detecting fungal organisms (95.9%) compared with in situ hybridization (ISH; 82.7%). ISH with oligonucleotide deoxyribonucleic acid probes, however, was more specific, with all species-specific probes yielding 100% specificity (compared with 96.2-100% specificity based on morphology alone). ISH also had a higher positive predictive value (100% in all cases) compared with GMS (83.3-100%). In addition, four cases with rare organisms present (4.1% of cases tested) were detected by ISH but not by GMS staining. These results show that ISH, directed against ribosomal ribonucleic acid, provides a rapid, accurate technique for the identification of yeastlike organisms in histologic tissue sections. Its primary strength lies in the ability to speciate organisms accurately that are too few or atypical to identify based solely on morphologic features.

Characterization of culture-derived spiral bacteria by 16S ribosomal RNA gene sequence analysis

Broad range amplification and sequence analysis of the 16S ribosomal RNA gene was used to identify three spiral-form organisms. The agents were identified as Campylobacter fetus, "Flexispira rappini", and Borrelia burgdorferi, respectively, using either proprietary or public sequence databases. In each case, the rDNA sequence showed 99-100% homology with known sequence data. Sequence-based analysis for each isolate required only 2-3 days, whereas traditional means of identification took 8-12 days to complete. The identification of spirochetes and vibrio-like agents from human clinical samples is often time consuming and results may be difficult to interpret, sometimes due to atypical phenotypic characteristics. Analysis of 16S rDNA or other molecular targets may provide a way to accurately and rapidly characterize isolates that are recalcitrant to speciation.

More laboratory testing: greater cost but not necessarily better

BACKGROUND

The bacterial latex agglutination assay is ordered predominantly on the pediatric population, for rapid screening for bacterial surface antigens in cerebrospinal fluid (CSF) or urine specimens. The high cost of this assay and questions raised in the literature regarding its accuracy led to a retrospective review of the use of this assay at a medium-sized midwest teaching hospital. The results of 6,370 bacterial latex agglutination tests performed between May, 1995, and November, 1996, and charts of patients being tested were reviewed.

RESULTS

This study demonstrated a sensitivity and specificity of 28.6% and 86.7% for urine specimens and 70.0% and 99.4% for CSF specimens. A total of 11 pathogens were accurately detected (7 CSF and 4 urine). There were 13 false negatives and 59 false positives. None of the true positives had a discernible effect on either treatment or hospital course; however, several of the erroneous tests resulted in delayed or unnecessary treatment and workup of the involved patients. The annual billed cost of this test at this institution (fiscal years 1995 to 1997) averaged $167,000 per annum. This does not include indirect costs associated with increased length of hospital stay, overutilization of antibiotics and excess laboratory tests ordered as a result of false positives.

CONCLUSIONS

Bacterial antigen latex agglutination testing is neither sufficiently sensitive nor specific to be used as a screening test. Accurate results have no demonstrable clinical impact, whereas numerous inaccurate results are often generated at great cost. The continued use of the latex agglutination assay should be seriously questioned in an era when cost containment and clinical efficiency are becoming increasingly important.

Optimizing detection of microbial sepsis: a comparison of culture systems using packaged sets with directions for blood collection

Detection of microbial sepsis is an important aspect of medical practice. To facilitate the recovery of bacteria and fungi we evaluated 10,933 complete blood culture sets integrating the automated ESP system (Difco) with a manual system using the Isolator (Wampole) and Thiol broth bottle (Difco). To improve compliance with the recommended procedure for submitting specimens, we packaged the three components as a unit that included brief instructional material. A three-component (one ESP bottle, one Thiol bottle, and one Isolator tube) package containing specific instructions was used. The aerobic ESP performance was compared with the Isolator, and the anaerobic ESP with the Thiol bottle. A hypothetical assessment involving all three components was also made. The cultures were processed under routine laboratory conditions. Charts were reviewed from specimens with discrepant results to ascertain true positives versus contaminant cultures in the discordant culture sets. There were 896 organisms recovered from 393 patients. Of these, 421 were in the aerobic compared with 475 in the anaerobic portion of the study. ESP enhanced the recovery of Streptococcus pneumoniae (P < .05). The Isolator was superior for the recovery of yeasts (.05 < P < .1). Using the packaged system, the compliance rate for complete three-component culture sets was 95.2%, with a 34.4% resultant increase in positive blood cultures from only a 5.7% increase in sets. Packaged culture media including instructions enhance appropriate collection of complete sets, increase the number of recovered organisms, and improve medical practice.

Multilocular prostatic cystadenoma presenting as a large complex pelvic cystic mass

Symptomatic prostatic cysts are not common. We report a case of a large complex cystic pelvic mass encountered in a Jordanian man that proved to be a huge midline prostatic cyst with seminal vesicle contained within the wall. This finding represents a variation of the newly proposed diagnosis, multilocular prostatic cystadenoma.