The deployment of mobile diagnostic laboratories for Ebola virus disease diagnostics in Sierra Leone and Guinea.

BACKGROUND: Ebola virus emerged in West Africa in December 2013. The ease of mobility, porous borders, and lack of public health infrastructure led to the largest Ebola virus disease (EVD) outbreak to date. INTERVENTION: The 2013 EVD outbreak signalled the need for laboratory diagnostic capabilities in areas without strong public health systems. As part of the United States' Department of Defense response, MRIGlobal was contracted to design, fabricate, equip, deploy, and operate two mobile diagnostic laboratories (MDLs). The first laboratory analysed blood samples from patients in an adjacent Ebola Treatment Centre (ETC) and buccal swabs from the deceased in the community in Moyamba, Sierra Leone. The second laboratory was deployed to support an ETC in Conakry, Guinea. The Department of Defense provided real-time quantitative reverse transcription polymerase chain reaction assays that were deployed and validated on-site. LESSONS LEARNT: Prompt and accurate molecular diagnostics reduced sample turn-around times from over 24 h to under 4 h. Experienced laboratory staff tested up to 110 samples per day and on-site engineering proved necessary for MDL setup and operation. As the Ebola response slowed, the sustainment of the MDLs' operations was prioritised, including staff training and the transition of the MDLs to local governments. Training programmes for local staff were prepared in Sierra Leone and Guinea. RECOMMENDATIONS: The MRIGlobal MDL team significantly contributed to establishing increased laboratory capacity during the EVD outbreak in West Africa. Using the MDLs for molecular diagnosis is highly recommended until more sustainable solutions can be provided.

The effects of MDR/RR-TB treatment on HIV disease: A systematic review of literature.

BACKGROUND: Multidrug-resistant or rifampicin-resistant tuberculosis (MDR/RR-TB) and human immunodeficiency virus (HIV) co-infection are a deadly combination. While evidence on the effects of HIV co-infection on MDR/RR-TB treatment outcomes is well-documented, little published evidence describes the effects of MDR/RR-TB treatment on HIV disease. METHODS: We conducted a review of literature published prior to June 2020. We searched Pubmed, CINAHL, and EMBASE using variations of the terms "multidrug-resistant tuberculosis," "HIV," and either "CD4" or "viral load." Two reviewers independently completed title and abstract screening, full-text screening, article evaluation, and data extraction. We also included five published articles evaluated as evidence by the World Health Organization (WHO) in preparation for the 2019 MDR/RR-TB treatment guideline update. RESULTS: A total of 459 references were returned, with 362 remaining after duplicate removal. Following article screening, six manuscripts were included. Articles reported CD4 count and/or viral load results for MDR/RR-TB and HIV co-infected patients during and/or after MDR/RR-TB treatment. The additional five references identified from the WHO guideline revision did not report HIV disease indicators after MDR/RR-TB initiation. CONCLUSION: There is a paucity of evidence on HIV disease indicators following MDR/RR-TB treatment. Researchers should report longitudinal HIV disease indicators in co-infected patients in publications.

Preparing the healthcare workforce in South Africa for short-course rifampicin-resistant TB treatment: inter-professional training and task-sharing considerations.

BACKGROUND: Treatment for rifampicin-resistant Mycobacterium tuberculosis (RR-TB) is complex, however, shorter treatment, with newer antimicrobials are improving treatment outcomes. The South African National Department of Health (NDoH) recently accelerated the rollout of 9-month, all-oral, RR-TB short-course regimens. We sought to evaluate an inter-professional training program using pre-test and post-test performance of Professional Nurses (PNs), Advanced Practice Professional Nurses (APPNs) and Medical Officers (MOs) to inform: (a) training needs across cadres; (b) knowledge performance, by cadres; and (c) training differences in knowledge by nurse type. METHODS: A 4-day didactic and case-based clinical decision support course for RR-TB regimens in South Africa (SA) was developed, reviewed and nationally accredited. Between February 2017 and July 2018, 12 training events were held. Clinicians who may initiate RR-TB treatment, specifically MOs and PN/APPNs with matched pre-post tests and demographic surveys were analyzed. Descriptive statistics are provided. Pre-post test evaluations included 25 evidence-based clinically related questions about RR-TB diagnosis, treatment, and care. RESULTS: Participants (N = 842) participated in testing, and matched evaluations were received for 800 (95.0%) training participants. Demographic data were available for 793 (99.13%) participants, of whom 762 (96.1%) were MOs, or nurses, either PN or APPNs. Average correct response pre-test and post-test scores were 61.7% (range 7-24 correct responses) and 85.9% (range 12-25), respectively. Overall, 95.8% (730/762) of participants demonstrated improved knowledge. PNs improved on average 25% (6.22 points), whereas MOs improved 10% (2.89 points) with better mean test scores on both pre- and post-test (p < 0.000). APPNs performed the same as the MOs on post-test scores (p = NS). CONCLUSIONS: The inter-professional training program in short-course RR-TB treatment improved knowledge for participants. MOs had significantly greater pre-test scores. Of the nurses, APPNs outperformed other PNs, and performed equally to MOs on post-test scores, suggesting this advanced cadre of nurses might be the most appropriate to initiate and monitor treatment in close collaboration with MOs. All cadres of nurse reported the need for additional clinical training and mentoring prior to managing such patients.

Multicenter Evaluation of the Accelerate PhenoTest BC Kit for Rapid Identification and Phenotypic Antimicrobial Susceptibility Testing Using Morphokinetic Cellular Analysis.

We describe results from a multicenter study evaluating the Accelerate Pheno system, a first of its kind diagnostic system that rapidly identifies common bloodstream pathogens from positive blood cultures within 90 min and determines bacterial phenotypic antimicrobial susceptibility testing (AST) results within ∼7 h. A combination of fresh clinical and seeded blood cultures were tested, and results from the Accelerate Pheno system were compared to Vitek 2 results for identification (ID) and broth microdilution or disk diffusion for AST. The Accelerate Pheno system accurately identified 14 common bacterial pathogens and two Candida spp. with sensitivities ranging from 94.6 to 100%. Of fresh positive blood cultures, 89% received a monomicrobial call with a positive predictive value of 97.3%. Six common Gram-positive cocci were evaluated for ID. Five were tested against eight antibiotics, two resistance phenotypes (methicillin-resistant Staphylococcus aureus and Staphylococcus spp. [MRSA/MRS]), and inducible clindamycin resistance (MLSb). From the 4,142 AST results, the overall essential agreement (EA) and categorical agreement (CA) were 97.6% and 97.9%, respectively. Overall very major error (VME), major error (ME), and minor error (mE) rates were 1.0%, 0.7%, and 1.3%, respectively. Eight species of Gram-negative rods were evaluated against 15 antibiotics. From the 6,331 AST results, overall EA and CA were 95.4% and 94.3%, respectively. Overall VME, ME, and mE rates were 0.5%, 0.9%, and 4.8%, respectively. The Accelerate Pheno system has the unique ability to identify and provide phenotypic MIC and categorical AST results in a few hours directly from positive blood culture bottles and support accurate antimicrobial adjustment.

National Laboratory Planning: Developing Sustainable Biocontainment Laboratories in Limited Resource Areas.

Strategic laboratory planning in limited resource areas is essential for addressing global health security issues. Establishing a national reference laboratory, especially one with BSL-3 or -4 biocontainment facilities, requires a heavy investment of resources, a multisectoral approach, and commitments from multiple stakeholders. We make the case for donor organizations and recipient partners to develop a comprehensive laboratory operations roadmap that addresses factors such as mission and roles, engaging national and political support, securing financial support, defining stakeholder involvement, fostering partnerships, and building trust. Successful development occurred with projects in African countries and in Azerbaijan, where strong leadership and a clear management framework have been key to success. A clearly identified and agreed management framework facilitate identifying the responsibility for developing laboratory capabilities and support services, including biosafety and biosecurity, quality assurance, equipment maintenance, supply chain establishment, staff certification and training, retention of human resources, and sustainable operating revenue. These capabilities and support services pose rate-limiting yet necessary challenges. Laboratory capabilities depend on mission and role, as determined by all stakeholders, and demonstrate the need for relevant metrics to monitor the success of the laboratory, including support for internal and external audits. Our analysis concludes that alternative frameworks for success exist for developing and implementing capabilities at regional and national levels in limited resource areas. Thus, achieving a balance for standardizing practices between local procedures and accepted international standards is a prerequisite for integrating new facilities into a country's existing public health infrastructure and into the overall international scientific community.

Clinical Features of and Risk Factors for Fatal Ebola Virus Disease, Moyamba District, Sierra Leone, December 2014-February 2015.

The 2013-2016 outbreak of Ebola virus disease (EVD) in West Africa infected >28,000 people, including >11,000 who died, and disrupted social life in the region. We retrospectively studied clinical signs and symptoms and risk factors for fatal outcome among 31 Ebola virus-positive patients admitted to the Ebola Treatment Center in Moyamba District, Sierra Leone. We found a higher rate of bleeding manifestations than reported elsewhere during the outbreak. Significant predictors for death were shorter time from symptom onset to admission, male sex, high viral load on initial laboratory testing, severe pain, diarrhea, bloody feces, and development of other bleeding manifestations during hospitalization. These risk factors for death could be used to identify patients in need of more intensive medical support. The lack of fever in as many as one third of EVD cases may have implications for temperature-screening practices and case definitions.

Clinical features of suspected Ebola cases referred to the Moyamba ETC, Sierra Leone: challenges in the later stages of the 2014 outbreak.

BACKGROUND: The last ebola virus disease (EVD) outbreak has been the most important since 1976. EVD cases decreased drastically in Sierra Leone at the beginning of 2015. We aim to determine the clinical findings and evolution of patients admitted to an Ebola treatment center (ETC) during the epidemic's late phase. METHODS: We analyze retrospectively data of patients admitted to the Moyamba ETC (December 2014-March 2015). Patients were classified in EVD or non-EVD patients according to the results of Ebola virus real-time reverse transcription polymerase chain reaction (ZAIRE-RT-PCR). RESULTS: Seventy-five patients were included, 41.3 % were positive for ZAIRE-RT-PCR. More women (68 % vs 28 %, p = 0.001) were EVD-positive. More EVD patients had previous contact with an Ebola patient (74.2 % vs 36.3 %, p < 0.001). At admission, EVD patients were more likely to have fatigue (96.7 %, p < 0.001), diarrhea (67.7 %, p = 0.002), and muscle pain (61.3 %, p = 0.009); but only objective fevers in 35.5 % of EVD patients. The most reliable criteria for diagnosis were: contact with an Ebola patient plus three WHO symptoms (LR + =3.7, 95 % CI = 1.9-7.3), and positive contact (LR + =2.3, 95 % CI = 1.15-4.20). Only 45.2 % of EVD patients developed fevers during stay, but 75 % developed gastrointestinal symptoms. Non-EVD patients had gastrointestinal problems (33 %), respiratory conditions (26.6 %), and others such as malaria, HIV or tuberculosis with a mortality rate of 11.4 %. vs 58 % in EVD group (p < 0.001). CONCLUSIONS: More non-EVD patients were admitted in the outbreak's late phases. The low percentage of initial fever highlights the need to emphasize the epidemiological information. EVD patients presented new symptoms getting worse and requiring closer follow-up. Diagnoses of non-EVD patients were diverse with a remarkable mortality, presenting a challenge for the health system.

Comparison of five chromogenic media for recovery of vancomycin-resistant enterococci from fecal samples.

Five chromogenic agars, evaluated using 400 stool specimens, were found to be superior in sensitivity (range, 89.9 to 93.9%) to bile esculin azide agar with vancomycin (BEAV) agar (84.8%) for detecting vancomycin-resistant enterococci (VRE), and the results were available 24 to 48 h sooner. The time to detection, need for supplemental testing, color distinction, and breakthrough of non-VRE organisms vary among the chromogenic media tested and may factor into the decision to use a particular medium.

Multicenter evaluation of the Verigene Clostridium difficile nucleic acid assay.

The Verigene Clostridium difficile Nucleic Acid test (Verigene CDF test) (Nanosphere, Northbrook, IL) is a multiplex qualitative PCR assay that utilizes a nanoparticle-based array hybridization method to detect C. difficile tcdA and tcdB in fecal specimens. In addition, the assay detects binary toxin gene sequences and the single base pair deletion at nucleotide 117 (Δ 117) in tcdC to provide a presumptive identification of the epidemic strain 027/NAP1/BI (referred to here as ribotype 027). This study compared the Verigene CDF test with anaerobic direct and enriched toxigenic culture on stool specimens from symptomatic patients among five geographically diverse laboratories within the United States. The Verigene CDF test was performed according to the manufacturer's instructions, and the reference methods performed by a central laboratory included direct culture onto cycloserine cefoxitin fructose agar (CCFA) and enriched culture using cycloserine cefoxitin mannitol broth with taurocholate and lysozyme. Recovered isolates were identified as C. difficile using gas liquid chromatography and were tested for toxin using a cell culture cytotoxicity neutralization assay. Strains belonging to ribotype 027 were determined by PCR ribotyping and bidirectional sequencing for Δ 117 in tcdC. A total of 1,875 specimens were evaluable. Of these, 275 specimens (14.7%) were culture positive by either direct or enriched culture methods. Compared to direct culture alone, the overall sensitivity, specificity, positive predictive value, and negative predictive value for the Verigene CDF test were 98.7%, 87.5%, 42%, and 99.9%, respectively. Compared to combined direct and enriched culture results, the sensitivity, specificity, positive predictive value, and negative predictive values of the Verigene CDF test were 90.9%, 92.5%, 67.6%, and 98.3%, respectively. Of the 250 concordantly culture-positive specimens, 59 (23.6%) were flagged as "hypervirulent"; 53 were confirmed as ribotype 027, and all 59 possessed Δ 117 in tcdC. Time to results was approximately 2.5 h per specimen. The Verigene CDF test is a novel nucleic acid microarray that reliably detects both C. difficile toxins A and B in unformed stool specimens and appears to adequately identify ribotype 027 isolates.

Development of a simple, low-density array to detect methicillin-resistant Staphylococcus aureus and mecA dropouts in nasal swabs.

Detection of methicillin-resistant Staphylococcus aureus (MRSA) is important for prevention and control of MRSA infections, but the discovery of mecA dropouts and SCCmec junction sequences with homology to coagulase-negative staphylococci (CoNS) has challenged several real-time PCR tests. The objective of this study was to develop a user-friendly, gel element microarray test for MRSA detection, to estimate the analytical performance characteristics of the test on bacterial isolates, and to perform an initial evaluation of the test on nasopharyngeal swabs from patients known to have a high prevalence of S. aureus containing mecA dropouts. The assay limit of detection for the test was 250 fg (or less) of genomic DNA per amplification reaction (approximately 80 cell equivalents) and MRSA was consistently detected at a ratio of 1:12,000 in a non-target background. Of 87 bacterial isolates, the test accurately classified 86 (98.8%) overall, and correctly identified 14 mecA dropout specimens that were falsely positive in the BD GeneOhm MRSA test or BD GeneOhm StaphSR test. A retrospective analysis of 246 nasal swab samples acquired from a high-risk patient population (overall prevalence=10.8% by culture) resulted in 80.5% sensitivity (95% CI=68.4%, 92.6%) and 96.6% specificity. Of these 246 samples, 174 (71%) were positive for mecA, 86 (35%) were positive for S. aureus tufA and 46 (19%) were positive for a SCCmec junction sequence. To estimate method repeatability, 48 samples representing the full range of phenotypes, genotypes and microarray probe SNR values were tested in triplicate, with three discordant results for a concordance rate of 97.9% (141/144 tests). These data demonstrate that a very simple microarray test can identify mecA dropouts with high specificity in either cultured isolates or nasal swabs from a high-prevalence, high-risk patient population. However, the clinical sensitivity of the test will likely depend on local microbial ecology and the prevalence of mecA positive CoNS in any given patient population.

Genotypic and phenotypic characterization of methicillin-susceptible Staphylococcus aureus isolates misidentified as methicillin-resistant Staphylococcus aureus by the BD GeneOhm MRSA assay.

Twenty-three nasal swab samples that tested positive for methicillin-resistant Staphylococcus aureus (MRSA) on initial testing by the BD GeneOhm MRSA assay (BD-MRSA PCR; BD GeneOhm, San Diego, CA) were culture positive only for methicillin-susceptible S. aureus (MSSA) from an enrichment broth. The 23 recovered isolates were confirmed as MSSA by a variety of phenotypic methods, including the BD Phoenix automated microbiology system (BD Diagnostics, Sparks, MD), oxacillin screening agar (BD Diagnostics), BBL CHROMagar MRSA (BD Diagnostics), and a PBP2' assay (Denka Seiken Co., Tokyo, Japan); susceptibilities were determined by using Mueller-Hinton agar with oxacillin. All were positive by nuc PCR, specific for S. aureus, but negative for mecA with one exception. Isolates were characterized by using multiplex PCR methodology to determine structural types and variants (SCCmec typing); additional PCRs were performed for the detection of the ccr and mec complexes, the junkyard regions as well as the Panton-Valentine leukocidin. Pulsed-field gel electrophoresis was used to determine clonality. One phenotypic MSSA isolate contained an intact SCCmec. Twelve MSSA isolates tested positive for MRSA by the BD-MRSA PCR because of amplification of the mec priming site flanking the SCC insertion point, although these isolates lacked mecA. The 10 remaining isolates were not MRSA and tested as MSSA by phenotypic and genotypic assays. In our patient population, diagnostic and surveillance testing and subsequent infection control practices may be impacted by the frequency of these excision events when using the BD-MRSA PCR for MRSA detection.

Comparison of BD Bactec Plus Aerobic/F medium to VersaTREK Redox 1 blood culture medium for detection of Candida spp. in seeded blood culture specimens containing therapeutic levels of antifungal agents.

Recovery of Candida spp. using the BD Bactec FX blood culture (BC) system (Bactec Plus Aerobic/F medium) and the VersaTREK system (aerobic Redox medium) was evaluated using seeded BC bottles with and without the addition of commonly used antifungal agents. BC bottles (n = 1,442) were each inoculated with 10 ml human whole blood and 0.1 ml of suspensions of Candida spp., with or without antifungal agents. BC bottles were incubated in the corresponding system for a maximum of 5 days. In the absence of antifungal agents, Bactec FX recovered 97.4% of Candida spp., and VersaTREK recovered 99.1% (P = 0.154). With regard to length of time to detection (LTD) and overall recovery, both systems had various levels of effectiveness in recovering C. glabrata. In bottles containing antifungal agents, Bactec FX recovered 83.1% of isolates, whereas VersaTREK recovered 50.7% of Candida spp. (P < 0.001). For BC bottles without the addition of antifungal agents, the median LTD for VersaTREK was 2.2 h faster than that of Bactec FX (P < 0.001). In the presence of antifungal agents, the Bactec FX recovery time was significantly faster than that of VersaTREK (median difference of 10.8 h, P < 0.001). We conclude that both systems have comparable abilities to recover Candida spp. from seeded blood cultures in the absence of antifungal agents. In the presence of therapeutic levels of commonly used antifungal agents, the Bactec FX system demonstrated a significantly greater recovery of various Candida spp., as well as a shorter LTD.

Evaluation of BBL CHROMagar VanRE for detection of vancomycin-resistant Enterococci in rectal swab specimens.

A study was performed on 517 surveillance rectal swabs to evaluate a selective and differential chromogenic medium, the BBL CHROMagar VanRE (CVRE), which enables recovery and identification of VanA- and VanB-containing Enterococcus faecium (ENFM) and Enterococcus faecalis (ENFS) isolates. Compared to BBL Enterococcosel agar, a bile-esculin-azide-vancomycin (BEAV) agar, the initial overall sensitivity, specificity, and positive and negative predictive values of CVRE for the detection of vancomycin-resistant ENFM and ENFS were 99.1% and 94.8% and 84.2% and 99.7%, respectively. Among our patient population, more vancomycin-resistant enterococci (VRE) were recovered with CVRE than BEAV.

Evaluation of Bio-Rad MRSASelect agar for detection of methicillin-resistant Staphylococcus aureus directly from blood cultures.

MRSASelect agar (Bio-Rad, Redmond, WA) was evaluated for its performance in detecting MRSA directly from positive blood cultures containing Gram-positive cocci in clusters. Agar plates were evaluated for the presence of pink colonies at 18 to 24 h. Results were compared to organism identification by using standard laboratory methods. Confirming coagulase on pink isolates, the sensitivity and specificity were both 99%.

Evaluation of a new commercial TaqMan PCR assay for direct detection of the clostridium difficile toxin B gene in clinical stool specimens.

The ProGastro Cd assay (Prodesse, Inc., Waukesha, WI) is a new commercial TaqMan PCR assay that detects tcdB. The ProGastro Cd assay was compared to the Wampole Clostridium difficile toxin B test (TOX-B test; TechLab, Blacksburg, VA), a cell culture cytotoxicity neutralization assay (CCCNA), and to anaerobic toxigenic bacterial culture, as the "gold standard," for 285 clinical stool specimens. Assays were independently performed according to manufacturers' directions. A 1.0-ml sample was removed from the stool specimen, of which 20 microl was used for extraction on the NucliSENS easyMAG platform (bioMérieux, Inc., Durham, NC) for the Prodesse ProGastro Cd assay and 200 microl of the stool filtrate was used for the TOX-B CCCNA. Anaerobic toxigenic culture was done by heating an additional 1.0 ml of the stool sample to 80 degrees C for 10 min before inoculation onto modified cycloserine, cefoxitin, and fructose agar with horse blood (Remel, Lenexa, KS) and into a prereduced chopped meat glucose broth (BBL, BD Diagnostics, Sparks, MD). The prevalence of toxin-producing strains of C. difficile was 15.7% (n = 44) as determined by anaerobic toxigenic culture. The sensitivity, specificity, and positive and negative predictive values of the Prodesse ProGastro Cd assay compared to the TOX-B test were 83.3%, 95.6%, 69.4%, and 98%, respectively. Compared to toxigenic culture, the sensitivity, specificity, and positive and negative predictive values of the Prodesse ProGastro Cd assay were 77.3%, 99.2%, 94.4%, and 95.9%, respectively, and those of the TOX-B test were 63.6%, 99.2%, 93.3%, and 93.6%, respectively. Although no statistical difference (Fisher's exact test) was detected (P = 0.242) between the sensitivities of the Prodesse ProGastro Cd assay and a standard CCCNA compared to anaerobic culture for the detection of toxigenic C. difficile, the Prodesse ProGastro Cd assay did detect more toxigenic C. difficile isolates than the CCCNA.

Performance of the Phoenix bacterial identification system compared with disc diffusion methods for identifying extended-spectrum beta-lactamase, AmpC and KPC producers.

Phenotypic identification of AmpC, KPC and extended-spectrum beta-lactamases (ESBLs) among members of the Enterobacteriaceae remains challenging. This study compared the Phoenix Automated Microbiology System (BD Diagnostics) with the Clinical and Laboratory Standards Institute confirmatory method to identify ESBL production among 200 Escherichia coli and Klebsiella pneumoniae clinical isolates. The Phoenix system misclassified nearly half of the isolates as ESBL-positive, requiring manual testing for confirmation. Inclusion of aztreonam +/- clavulanic acid (CA) and cefpodoxime +/- CA in the testing algorithm increased the ESBL detection rate by 6 %. Boronic acid-based screening identified 24 isolates as AmpC(+), but in a subset of genotypically characterized isolates, appeared to have a high false-positivity rate. PCR screening revealed eight KPC(+) isolates, all of which tested as ESBL(+) or ESBL(+) AmpC(+) by phenotypic methods, but half were reported as carbapenem-susceptible by the Phoenix system. Overall, these results indicate that laboratories should use the Phoenix ESBL results only as an initial screen followed by confirmation with an alternative method.

Comparison of the Bactec 9240 and BacT/Alert blood culture systems for evaluation of placental cord blood for transfusion in neonates.

The Bactec 9240 and the BacT/Alert blood culture systems were compared as a means for detection of bacterial contaminants in whole blood, concentrated red cells, and plasma preparations prepared from umbilical cord blood (UCB) samples. Ninety-two UCB units seeded with low levels of various bacteria were evaluated. In more than 50% of cases, growth was not detected in plasma using either system (P < 0.001). When concentrated red cells and whole blood were compared, the Bactec system detected bacterial growth consistently sooner than the BacT/Alert system in all seeded bacteria except Staphylococcus species in whole blood. The median lengths of time to detection (LTD) for whole blood and concentrated cells in BacT/Alert were 18.7 h and 18.5 h, respectively. The median LTD for the same blood fractions using the Bactec system were 16.05 h and 15.64 h. These differences in LTD by blood culture system and sample type were statistically significant (whole blood, P = 0.0449; concentrated cells, P = 0.0037). Based on the results of our study, we recommend the use of either concentrated red cells or whole blood for sterility testing in UCB samples. In our laboratory, the Bactec system compared to the BacT/Alert system was the superior method for rapid detection of bacterial contaminants in cord blood.

Comparison of a commercial real-time PCR assay for tcdB detection to a cell culture cytotoxicity assay and toxigenic culture for direct detection of toxin-producing Clostridium difficile in clinical samples.

Rapid detection of toxin-producing strains of Clostridium difficile is essential for optimal management of patients with C. difficile infection. The BD GeneOhm (San Diego, CA) Cdiff assay, a real-time PCR assay that amplifies tcdB, was compared to a cell culture neutralization assay (Wampole C. difficile Toxin B [TOX-B] test; TechLab, Blacksburg, VA) and to toxigenic culture. Using liquid (n = 273) and soft (n = 131) stool specimens from 377 symptomatic patients, all testing was performed on the same day by independent laboratory staff according to the manufacturers' protocols. Toxigenic bacterial culture was performed as follows. A 0.5-ml aliquot of stool was heated to 80 degrees C for 10 min, followed by inoculation onto modified cycloserine cefoxitin fructose agar with and without horse blood (Remel, Lenexa, KS) and into prereduced chopped-meat broth. Of the 404 stool specimens tested, 340 were negative and 40 were positive (10.0% prevalence) both by PCR for tcdB and by cytotoxin production. The overall agreement between the BD GeneOhm Cdiff assay and the TOX-B test was 94.8% (380/401). When the TOX-B test was used as the reference method, the initial sensitivity, specificity, and positive and negative predictive values of the BD GeneOhm Cdiff assay were 90.9% (40/44), 95.2% (340/357), 70.2% (40/57), and 98.8% (340/344), respectively. When toxigenic culture was used as the "gold standard," the sensitivity, specificity, and positive and negative predictive values of the BD GeneOhm Cdiff assay were 83.6%, 98.2%, 89.5%, and 97.1%, respectively, and those of the TOX-B test were 67.2%, 99.1%, 93.2%, and 94.4%, respectively. PCRs for three samples were inhibited upon initial testing; one sample was resolved upon retesting. One sample produced nonspecific cytotoxin results. The BD GeneOhm Cdiff assay performed well compared to a standard cell culture neutralization assay and to toxigenic culture for the detection of toxigenic C. difficile directly from fecal specimens.

Timing of specimen collection for blood cultures from febrile patients with bacteremia.

Bloodstream infections are an important cause of morbidity and mortality. Physician orders for blood cultures often specify that blood specimens be collected at or around the time of a temperature elevation, presumably as a means of enhancing the likelihood of detecting significant bacteremia. In a multicenter study, which utilized retrospective patient chart reviews as a means of collecting data, we evaluated the timing of blood culture collection in relation to temperature elevations in 1,436 patients with bacteremia and fungemia. The likelihood of documenting bloodstream infections was not significantly enhanced by collecting blood specimens for culture at the time that patients experienced temperature spikes. A subset analysis based on patient age, gender, white blood cell count and specific cause of bacteremia generally also failed to reveal any associations.

Comparison of the BD GeneOhm methicillin-resistant Staphylococcus aureus (MRSA) PCR assay to culture by use of BBL CHROMagar MRSA for detection of MRSA in nasal surveillance cultures from an at-risk community population.

We compared the BD GeneOhm methicillin-resistant Staphylococcus aureus (MRSA) PCR assay to culture with BBL CHROMagar MRSA for nasal surveillance among 602 arrestees from the Baltimore City Jail. The sensitivity and specificity were 88.5% and 91.0%, respectively, and after secondary analysis using enrichment broth, they were 89.0% and 91.7%, respectively. Twenty-three of 42 false-positive PCR lysates contained methicillin-susceptible S. aureus.