Comparison of Clostridioides difficile nucleic acid amplification test (NAAT) results using fresh and frozen stool specimens and rectal swabs.

IMPORTANCE: Nucleic acid amplification tests (NAATs) are frequently used in Clostridioides difficile research and diagnostic testing, but the effect of freezing specimens on C. difficile NAAT performance is not well characterized. This study evaluated the concordance of NAAT results between fresh and frozen specimens (fecal and rectal swabs) and found it to be very good to excellent. The results indicate that frozen fecal and rectal swab specimens may be used for C. difficile NAAT testing in research when fresh specimens are not available.

Optimizing recovery of Haemophilus influenzae from vaginal-rectal specimens and determining carriage rates in pregnant women.

PURPOSE: Haemophilus influenzae (HINF), primarily non-typeable H. influenzae: (NTHi), is an important cause of neonatal sepsis and meningitis. The goal of this study was to investigate the point prevalence of HINF vaginal-rectal carriage in pregnant women, which could impact neonatal health. METHODS: Simulated vaginal-rectal swabs were cultured and tested to establish optimal recovery methods for HINF. These methods were then applied to vaginal-rectal swabs from a prospective cohort of pregnant women (n = 300) undergoing routine Group B Streptococcus: (GBS) screening. Both culture and PCR were used for detection of HINF. Subject demographics, reproductive history, and genitourinary test results were documented. A retrospective surveillance study was conducted to determine incidence of invasive neonatal HINF infections from 7/1/2017-6/30/2023. RESULTS: HINF was recovered from 42/42 (100%) simulated vaginal-rectal swabs at 2-45 CFU/plate via direct plating onto chocolate and chocolate + bacitracin agar. HINF was rarely recovered following LIM broth enrichment at 0-75 CFU/plate in 1/42 (2.4%) simulated swabs, but was recovered from BHI/Fildes broth enrichment in 22/42 (52%) specimens at high abundance (> 100 CFU/plate). Among pregnant women prospectively screened for HINF, the median age was 29 (IQR, 24-33) years and gestational age was 36 (IQR, 34-36) weeks. HINF was recovered in 1 of 300 prospective specimens by culture but 0/100 by PCR. A six-year retrospective analysis showed there were seven total cases of neonatal sepsis and majority of HINF was isolated from respiratory specimens followed by blood/CSF overall. CONCLUSION: This study established a sensitive culture method for recovering HINF from vaginal-rectal swab specimens and demonstrated low prevalence of HINF carriage rate in pregnant women. These findings highlight the need for further research to pinpoint the source for transmission of HINF to neonates.

MALDI-TOF mass spectrometry misidentification of Cutibacterium namnetense and Cutibacterium modestum: Implications for multiplex PCR phylotyping of Cutibacterium acnes.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) can misidentify Cutibacterium namnetense and Cutibacterium modestum as Cutibacterium acnes. We now describe how such MALDI-TOF MS misidentification explains previous reports of C. acnes isolates that could not be characterised using a multiplex PCR phylotyping assay.

Outpatient Clonal Propagation and Rapid Regional Establishment of an Emergent Carbapenem-Resistant Acinetobacter baumannnii Lineage Sequence Type 499Pas.

Eliminating carbapenem-resistant Acinetobacter baumannii (CRAb) disease requires comprehensive knowledge of how this noncommensal organism propagates among at-risk hosts. We molecularly characterized an ongoing surge of CRAb cases among patients in a Midwest US healthcare system, which coincided with sustained reductions in hospital-acquired CRAb infections and falloffs of cases associated with distinctly more resistant antibiotypes. Genome sequencing revealed surge isolates belonged to an emergent Pasteur scheme sequence type 499 and comprised multiple contemporaneous clonal clusters. Detailed query of health records revealed no consistent hospital source but instead identified various outpatient healthcare settings linked to cluster cases. We show that CRAb can rapidly establish a regional presence even without gains in breadth of antibiotic resistance and negligible contribution from sustained intrahospital transmission. As CRAb lineages may sidestep control efforts via outpatient epidemiological niches, our approach can be implemented to investigate outpatient CRAb propagation and inform subsequent local surveillance outside hospital settings.

Genomic Analyses of Longitudinal Mycobacterium abscessus Isolates in a Multicenter Cohort Reveal Parallel Signatures of In-Host Adaptation.

BACKGROUND: Nontuberculous mycobacteria (NTM) are ubiquitous in the environment and an increasingly frequent cause of opportunistic infections. Mycobacterium abscessus complex (MABC) is one of the major NTM lung pathogens that disproportionately colonize and infect the lungs of individuals with cystic fibrosis (CF). MABC infection can persist for years, and antimicrobial treatment is frequently ineffective. METHODS: We sequenced the genomes of 175 isolates longitudinally collected from 30 patients with MABC lung infection. We contextualized our cohort amidst the broader MABC phylogeny and investigated genes undergoing parallel adaptation across patients. Finally, we tested the phenotypic consequences of parallel mutations by conducting antimicrobial resistance and mercury-resistance assays. RESULTS: We identified highly related isolate pairs across hospital centers with low likelihood of transmission. We further annotated nonrandom parallel mutations in 22 genes and demonstrated altered macrolide susceptibility co-occurring with a nonsynonymous whiB1 mutation. Finally, we highlighted a 23-kb mercury-resistance plasmid whose loss during chronic infection conferred phenotypic susceptibility to organic and nonorganic mercury compounds. CONCLUSIONS: We characterized parallel genomic processes through which MABC is adapting to promote survival within the host. The within-lineage polymorphisms we observed have phenotypic effects, potentially benefiting fitness in the host at the putative detriment of environmental survival.

The Impact of Universal Glove and Gown Use on Clostridioides Difficile Acquisition: A Cluster-Randomized Trial.

BACKGROUND: Clostridioides difficile is the most common cause of healthcare-associated infections in the United States. It is unknown whether universal gown and glove use in intensive care units (ICUs) decreases acquisition of C. difficile. METHODS: This was a secondary analysis of a cluster-randomized trial in 20 medical and surgical ICUs in 20 US hospitals from 4 January 2012 to 4 October 2012. After a baseline period, ICUs were randomized to standard practice for glove and gown use versus the intervention of all healthcare workers being required to wear gloves and gowns for all patient contact and when entering any patient room (contact precautions). The primary outcome was acquisition of toxigenic C. difficile determined by surveillance cultures collected on admission and discharge from the ICU. RESULTS: A total of 21 845 patients had both admission and discharge perianal swabs cultured for toxigenic C. difficile. On admission, 9.43% (2060/21 845) of patients were colonized with toxigenic C. difficile. No significant difference was observed in the rate of toxigenic C. difficile acquisition with universal gown and glove use. Differences in acquisition rates in the study period compared with the baseline period in control ICUs were 1.49 per 100 patient-days versus 1.68 per 100 patient-days in universal gown and glove ICUs (rate difference, -0.28; generalized linear mixed model, P = .091). CONCLUSIONS: Glove and gown use for all patient contact in medical and surgical ICUs did not result in a reduction in the acquisition of C. difficile compared with usual care. CLINICAL TRIALS REGISTRATION: NCT01318213.

Comparative Evaluation of Current Biochemical-, Sequencing-, and Proteomic-Based Identification Methods for the Streptococcus bovis Group.

The Streptococcus bovis group (previously group D streptococci) consists of seven distinct species and subspecies. Definitive identification within the group is important, as certain organisms have been associated with gastrointestinal carcinoma, bacteremia, infective endocarditis, meningitis, biliary tract disease, and carcinoma, among others. Definitive identification, however, remains elusive due to limitations and inconsistencies across commonly used identification platforms in the United States. Here, we compared the performance of standard biochemical (Trek Gram-positive identification [GPID] plate, Vitek 2 GPID), sequencing (16S rDNA, sodA) databases (NCBI, RDP, CDC MicrobeNet), and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) platforms (Vitek MS, Bruker Biotyper MS) using a set of eight type strains representing all seven strains within the S. bovis group. Despite the evaluation of contemporary methods, no single platform was able to definitively identify all type strains within the S. bovis group. Vitek MS (85.7%, 7/8) provided the most accurate definitive identifications, followed by sodA sequencing (75%, 6/8). Vitek 2 and Bruker Biotyper RUO platforms performed the next best (62.5%, 5/8). All remaining platforms failed to adequately differentiate type strains within the S. bovis group (range, 0 to 37.5%). Laboratorians and clinicians should be aware of the identification limitations of routine testing algorithms and incorporate reflex testing, when appropriate, to platforms such as Vitek MS and/or sodA sequencing that are more able to definitively identify S. bovis group organisms. Further clinical evaluation was conducted using 65 clinical isolates from three geographically distinct U.S. institutions. Future improvements in identification platforms may reveal new clinical and epidemiological trends for members of the S. bovis group.

Routine Use of Anaerobic Blood Culture Bottles for Specimens Collected from Adults and Children Enhances Microorganism Recovery and Improves Time to Positivity.

The utility of anaerobic blood culture bottles remains controversial, especially for specimens from children. Data are limited on the inclusion of an anaerobic bottle as part of a blood culture "set" when using contemporary blood culture instruments and media. Here, we evaluated the clinical utility of anaerobic blood culture bottles (FN Plus) and aerobic bottles (FA Plus) for the BacT/Alert Virtuo blood culture system (bioMérieux). A total of 158,710 bottles collected between November 2018 and October 2019 were evaluated. There were 6,652 positive anaerobic bottles, of which 384 (5.8%) contained 403 obligate anaerobes. In patients <19 years old, there were 389 positive anaerobic bottles, with 15 (1.8%) containing 16 obligate anaerobes. If not for anaerobic bottles, all but 8 obligate anaerobes would have gone undetected. Furthermore, anaerobic bottles were advantageous for some facultative anaerobes. Staphylococcus aureus from anaerobic bottles demonstrated statistically significant increased recovery (1,992 anaerobic versus 1,901 aerobic bottles, P = 0.009) and faster mean time to positivity (1,138 versus 1,174 min, P = 0.027). Only 25 microorganisms had statistically significant improved recovery and/or faster time to positivity from aerobic versus anaerobic bottles, suggesting anaerobic bottles offer comparable growth for most species. Finally, if only an aerobic bottle had been collected, 2,027 fewer positive cultures would have been detected and 7,452 fewer isolates would have been reported, including cultures with S. aureus (413 isolates, 10.6% less), Pseudomonas aeruginosa (9 isolates, 3.1% less) and Escherichia coli (193 isolates, 14.0% less). Taken together, these findings support the practice of routinely including an anaerobic bottle for blood culture collection.

Stop Waiting for Tomorrow: Disk Diffusion Performed on Early Growth Is an Accurate Method for Antimicrobial Susceptibility Testing with Reduced Turnaround Time.

Disk diffusion is a slow but reliable standard method for measuring the antimicrobial susceptibility of microorganisms. Our objective was to improve the turnaround time for this method by reducing the time that cultures are incubated before setting up disk diffusion testing. For initial method development, clinical isolates (n = 13) and quality control strains (n = 8) of bacteria were inoculated on blood agar and were incubated at 35°C for either 6, 10, or 24 h before performing disk diffusion testing, in triplicate, using a panel of clinically appropriate antimicrobial agents. Disk diffusion zone sizes were interpreted using Clinical and Laboratory Standards Institute (CLSI) guidelines. Compared to standard 24 h of incubation, early 6-h growth had 1.3% major errors (MEs) and 1.9% very major errors (VMEs), whereas 10-h growth yielded 0.7% MEs and no VMEs. Categorical agreement with standard incubation was similar for both 6 h (96.7%) and 10 h (96.7%) growth. Inhibitory zone size from 6 h (r2 = 0.98) and 10 h (r2 = 0.99) growth correlated well with results from standard conditions. Based on these results, we performed disk diffusion under optimized conditions (6 h growth), using 100 additional clinical isolates, demonstrating a high level of categorical agreement (917 of 950 measurements [96.5%]; 95% confidence interval [CI], 95.2 to 97.5%), as well as no VMEs or MEs. Using early growth for disk diffusion testing is a simple and accurate method for susceptibility testing that can reduce time to results by as much as 18 h, compared to standard incubation, with no additional supply costs or equipment/instrumentation.

Time for Some Group Therapy: Update on Identification, Antimicrobial Resistance, Taxonomy, and Clinical Significance of the Bacteroides fragilis Group.

Bacteroides fragilis group (BFG) species are common members of the human microbiota that provide several benefits to healthy hosts, yet BFG are also the most common anaerobes isolated from human infections, including intra-abdominal infections, abscesses, and bloodstream infection. Compared to many other anaerobes associated with disease, members of the BFG are more likely to be resistant to commonly used antimicrobials, including penicillin (>90% resistant), carbapenems (2 to 20% resistant), and metronidazole (0.2 to 4% resistant). As a result, infection with BFG bacteria can be associated with poor clinical outcomes. Here, we discuss the role of BFG in human health and disease, proposed taxonomic reclassifications within the BFG, and updates in methods for species-level identification. The increasing availability of whole-genome sequencing (WGS) supports recent proposals that the BFG now span two families (Bacteroidaceae and "Tannerellaceae") and multiple genera (Bacteroides, Parabacteroides, and Phocaeicola) within the phylum Bacteroidota. While members of the BFG are often reported to "group" rather than "species" level in many clinical settings, new reports of species-specific trends in antimicrobial resistance profiles and improved resolution of identification tools support routine species-level reporting in clinical practice. Empirical therapy may not be adequate for treatment of serious infections with BFG, warranting susceptibility testing for serious infections. We summarize methods for antimicrobial susceptibility testing and resistance prediction for BFG, including broth microdilution, agar dilution, WGS, and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). We examine global trends in BFG antimicrobial resistance and review genomics of BFG, revealing insights into rapid activation and dissemination of numerous antimicrobial resistance mechanisms.

The Impact of Implementing the Virtuo Blood Culture System on the Characteristics and Management of Patients with Staphylococcus aureus Bacteremia.

Persistent Staphylococcus aureus bacteremia (SAB) has been associated with increased mortality. Enhanced microbial detection with new blood culture technology may improve detection of S. aureus in patients with SAB. We performed a 24-month retrospective study of hospitalized adults with SAB and an infectious diseases consult comparing two time periods pre- (January to December 2018) and postimplementation (January to December 2019) in which the VersaTREK and BacT/Alert Virtuo blood culture systems were used, respectively. Measurements included SAB duration, time to positivity, source of bacteremia, antimicrobial therapy, and mortality. A total of 416 episodes of SAB occurred during the study period: 176 (42%) pre- and 240 (58%) postimplementation. Patients in both periods had similar clinical characteristics; however, patients in the postimplementation period were more likely to have intermediate (3 to 6 days; 23% versus 40%; P < 0.001) and prolonged SAB duration (>7 days; 4% versus 14%; P < 0.001). Combination antistaphylococcal therapy was more frequent postimplementation (6.3% pre- versus 15.8% postimplementation; P = 0.003), and the median time to source control was shorter (4 versus 2 days; P = 0.02). Median time to positivity for the index blood culture was shorter postimplementation (17.8 h pre- versus 13.3 h postimplementation; P < 0.001). There was no difference in 90-day all-cause readmissions (51% versus 44%; P = 0.11) or mortality (32% versus 32%; P = 0.95). An increased frequency of prolonged SAB with increased use of combination antistaphylococcal therapy was noted with implementation of a new blood culture system, likely secondary to the blood culture media; however, no differences on adverse outcomes were noted.

Development and Validation of a Novel Anaerobic Carbapenem Inactivation Method (Ana-CIM) for the Detection of Carbapenemase Production in Bacteroides fragilis.

Antibiotic resistance, particularly to carbapenems, is of increasing concern in Bacteroides fragilis. Carbapenem resistance in B. fragilis is most often mediated by the activation of chromosomally encoded metallo-ß-lactamase cfiA by the presence of an upstream insertion sequence (IS). While traditional phenotypic susceptibility methods and molecular tests to detect carbapenem resistance in B. fragilis exist, they are not available in most clinical microbiology laboratory settings. Here, we describe the development of the anaerobic carbapenem inactivation method (Ana-CIM) for predicting carbapenemase production in B. fragilis based off the principles of the well-established modified carbapenem inactivation method (mCIM) for Enterobacterales and Pseudomonas aeruginosa. We also present the clinical validation and reproducibility of the Ana-CIM at three clinical laboratory sites (with 60 clinical isolates, 45% ertapenem resistant). Compared to ertapenem susceptibility by Etest interpreted by CLSI M100 Ed30, the Ana-CIM accurately detected carbapenem resistance in B. fragilis with categorical agreement (CA) of 87% (52/60) and 0% (0/21) very major error (VME), 11% (4/36) major error (ME), and 7% (4/60) minor error (mE) rates across all sites. Additionally, the Ana-CIM demonstrated high reproducibility with 5 clinical and 3 quality control (QC) isolates tested in triplicate with 3 commercial Mueller-Hinton media across all sites, with 93% (604/648) of replicates within a 2-mm zone size of the mode for each isolate. We conclude that the Ana-CIM can be readily deployed in clinical laboratories at a low cost for detection of carbapenemase-mediated resistance in B. fragilis.

Prevalence and Characterization of the Cefazolin Inoculum Effect in North American Methicillin-Susceptible Staphylococcus aureus Isolates.

Antistaphylococcal penicillins and cefazolin remain the primary treatments for infections with methicillin-susceptible Staphylococcus aureus (MSSA). The cefazolin inoculum effect (CzIE) causes the cefazolin MIC to be elevated in proportion to the number of bacteria in the inoculum. The objective of this multicenter study was to evaluate the prevalence of the CzIE in North American MSSA isolates. Clinical MSSA isolates from six microbiology laboratories in the United States and one microbiology laboratory in Canada were screened for the CzIE by broth microdilution at a standard inoculum (~5 × 105 CFU/mL) and a high inoculum (~5 × 107 CFU/mL). Genome sequencing was performed to further characterize the MSSA isolates. The CzIE was present in 57/305 (18.6%) MSSA isolates, ranging from 0% to 27.9% across study sites. More of the CzIE-positive isolates (29.8%) had standard inoculum cefazolin MICs of 1.0 µg/mL than the CzIE-negative isolates did (3.2%) (P < 0.0001). Conversely, more CzIE-negative isolates (39.5%) had standard inoculum MICs of 0.25 µg/mL than the CzIE positive isolates did (5.3%) (P < 0.0001). The most common BlaZ ß-lactamase types found in the CzIE-positive strains were type C (53.7%) and type A (44.4%). ST8 and ST30 were the most common sequence types among CzIE-positive isolates and correlated with BlaZ type C and A, respectively. The CzIE was present in up to a quarter of clinical MSSA isolates from North American clinical laboratories. Further studies to determine the impact of the presence of the CzIE on clinical outcomes are needed.

Potent, specific MEPicides for treatment of zoonotic staphylococci.

Coagulase-positive staphylococci, which frequently colonize the mucosal surfaces of animals, also cause a spectrum of opportunistic infections including skin and soft tissue infections, urinary tract infections, pneumonia, and bacteremia. However, recent advances in bacterial identification have revealed that these common veterinary pathogens are in fact zoonoses that cause serious infections in human patients. The global spread of multidrug-resistant zoonotic staphylococci, in particular the emergence of methicillin-resistant organisms, is now a serious threat to both animal and human welfare. Accordingly, new therapeutic targets that can be exploited to combat staphylococcal infections are urgently needed. Enzymes of the methylerythritol phosphate pathway (MEP) of isoprenoid biosynthesis represent potential targets for treating zoonotic staphylococci. Here we demonstrate that fosmidomycin (FSM) inhibits the first step of the isoprenoid biosynthetic pathway catalyzed by deoxyxylulose phosphate reductoisomerase (DXR) in staphylococci. In addition, we have both enzymatically and structurally determined the mechanism by which FSM elicits its effect. Using a forward genetic screen, the glycerol-3-phosphate transporter GlpT that facilitates FSM uptake was identified in two zoonotic staphylococci, Staphylococcus schleiferi and Staphylococcus pseudintermedius. A series of lipophilic ester prodrugs (termed MEPicides) structurally related to FSM were synthesized, and data indicate that the presence of the prodrug moiety not only substantially increased potency of the inhibitors against staphylococci but also bypassed the need for GlpT-mediated cellular transport. Collectively, our data indicate that the prodrug MEPicides selectively and robustly inhibit DXR in zoonotic staphylococci, and further, that DXR represents a promising, druggable target for future development.

The Gut Microbiome as a Reservoir for Antimicrobial Resistance.

This review will consider the gut as a reservoir for antimicrobial resistance, colonization resistance, and how disruption of the microbiome can lead to colonization by pathogenic organisms. There is a focus on the gut as a reservoir for ß-lactam and plasmid-mediated quinolone resistance. Finally, the role of functional metagenomics and long-read sequencing technologies to detect and understand antimicrobial resistance genes within the gut microbiome is discussed, along with the potential for future microbiome-directed methods to detect and prevent infection.

HOME2 Study: Household Versus Personalized Decolonization in Households of Children With Methicillin-Resistant Staphylococcus aureus Skin and Soft Tissue Infection-A Randomized Clinical Trial.

BACKGROUND: A household approach to decolonization decreases skin and soft tissue infection (SSTI) incidence, though this is burdensome and costly. As prior SSTI increases risk for SSTI, we hypothesized that the effectiveness of decolonization measures to prevent SSTI when targeted to household members with prior year SSTI would be noninferior to decolonizing all household members. METHODS: Upon completion of our 12-month observational Household Observation of Methicillin-resistant Staphylococcus aureus in the Environment (HOME) study, 102 households were enrolled in HOME2, a 12-month, randomized noninferiority trial. Pediatric index patients with community-associated methicillin-resistant Staphylococcus aureus (MRSA) SSTI, their household contacts, and pets were enrolled. Households were randomized 1:1 to the personalized (decolonization performed only by household members who experienced SSTI during the HOME study) or household (decolonization performed by all household members) approaches. The 5-day regimen included hygiene education, twice-daily intranasal mupirocin, and daily bleach-water baths. At 5 follow-up visits in participants' homes, swabs to detect S. aureus were collected from participants, environmental surfaces, and pets; incident SSTIs were ascertained. RESULTS: Noninferiority of the personalized approach was established for the primary outcome 3-month cumulative SSTI: 23 of 212 (10.8%) participants reported SSTI in household approach households, while 23 of 236 (9.7%) participants reported SSTI in personalized approach households (difference in proportions, -1.1% [95% confidence interval, -6.7% to 4.5%]). In multivariable analyses, prior year SSTI and baseline MRSA colonization were associated with cumulative SSTI. CONCLUSIONS: The personalized approach was noninferior to the household approach in preventing SSTI. Future studies should interrogate longer durations of decolonization and/or decontamination of the household environment to reduce household MRSA burden. CLINICAL TRIALS REGISTRATION: NCT01814371.

Elevated MICs of Susceptible Antipseudomonal Cephalosporins in Non-Carbapenemase-Producing, Carbapenem-Resistant Pseudomonas aeruginosa: Implications for Dose Optimization.

The present study evaluated the in vitro potency of ceftazidime and cefepime among carbapenem-resistant Pseudomonas aeruginosa isolates collected as part of a global surveillance program and assessed the pharmacodynamic implications using previously published population pharmacokinetics. When susceptible, MICs resulted at the high end of distribution for both ceftazidime and cefepime, thus 6 g/day was required to achieve optimal pharmacodynamic profiles. These findings should be considered in the clinic and for the application of CLSI susceptibility breakpoints.

Comparison of Microorganism Detection and Time to Positivity in Pediatric and Standard Media from Three Major Commercial Continuously Monitored Blood Culture Systems.

New blood culture instrumentation and medium formulations have led to improved time to positivity (TTP) for positive blood cultures. Data regarding the necessity of pediatric blood culture bottles with contemporary blood culture systems are sparse. We compared performance of three commercial blood culture systems, evaluating impact of blood volumes in standard and pediatric blood culture media across systems. Simulated blood cultures with packed red blood cells (PRBCs) and three Gram-positive, four Gram-negative, and one anaerobic organism (final concentrations ranging from 0.5 to 19 CFU/ml blood) on the Virtuo, VersaTrek, and Bactec FX instruments were evaluated with FAN Plus, Redox, and Bactec Plus media, respectively. For each medium/instrument/organism combination, 1-, 3-, 5-, and 10-ml blood volumes were evaluated in triplicate. Detection rate was not affected by blood volume. Aerobic organisms that demonstrated variable rates of detection were Kingella kingae, Haemophilus influenzae, and Neisseria meningitidis. Bacteroides fragilis was detected in 83%, 100%, and 100% of Virtuo, VersaTrek, and Bactec anaerobic bottles, respectively. The average TTP of standard medium for aerobic organisms detected on Virtuo was decreased compared to those for VersaTrek (-2.3 h) and Bactec (-4.9 h). Compared to standard medium, detection rate and TTP were unchanged on Virtuo, while TTP was reduced with pediatric medium for 2/8 organisms tested on Bactec and 7/8 organisms on VersaTrek, illustrating the potential benefit of pediatric medium on VersaTrek or Bactec when low blood volumes (<5 ml) are collected. These results demonstrate that TTP is decreased on the Virtuo compared to VersaTrek and Bactec for many microorganisms associated with bloodstream infection (BSI) but may have species-specific limitations.

Real-World Evaluation of the Impact of Implementation of the Virtuo Blood Culture System in a Tertiary Care Hospital.

The bioMérieux BacT/Alert Virtuo blood culture system used in combination with resin-containing media may enhance the growth of microorganisms. Our objective was to assess the impact of transitioning to the Virtuo system in comparison to the VersaTREK blood culture system at a tertiary care medical center. We retrospectively reviewed all blood cultures performed at a 1,250-bed academic medical center between January and December 2018 (VersaTREK) and January and December 2019 (Virtuo). Blood culture positivity rates and contamination rates were compared before and after Virtuo implementation. Of 101,438 blood cultures performed during the study period, 48,839 (48.1%) were processed preimplementation and 52,599 (51.9%) postimplementation. The blood culture positivity rate increased from 8.1% preimplementation to 11.7% postimplementation (P < 0.001). Staphylococcus aureus was the most frequently isolated species in both time periods and had a higher recovery rate postimplementation (1.5% of all blood cultures obtained preimplementation versus 3.4% postimplementation; P < 0.001). A higher recovery rate in the postimplementation period was also noted for coagulase-negative staphylococci (1.9% preimplementation versus 2.7% postimplementation; P < 0.001), as well as modest but statistically significant changes for Escherichia coli (0.8% versus 1.0%; P < 0.001), Klebsiella pneumoniae (0.4% versus 0.5%; P = 0.005), and Candida albicans. (0.1% versus 0.2%; P = 0.038). The inpatient blood culture contamination rate was higher postimplementation (1.5% preimplementation versus 1.9% postimplementation; P < 0.001). The Virtuo blood culture system was associated with a higher observed proportion of positive blood cultures than the VersaTREK system. Future studies are needed to assess whether an increased rate of positive blood cultures is associated with changes in clinical outcomes.

SARS-CoV-2 E Gene Variant Alters Analytical Sensitivity Characteristics of Viral Detection Using a Commercial Reverse Transcription-PCR Assay.

Diagnostic assays for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are essential for patient management, infection prevention, and the public health response for coronavirus disease 2019 (COVID-19). The efficacy and reliability of these assays are of paramount importance in both tracking and controlling the spread of the virus. Real-time reverse transcription-PCR (RT-PCR) assays rely on a fixed genetic sequence for primer and probe binding. Mutations can potentially alter the accuracy of these assays and lead to unpredictable analytical performance characteristics and false-negative results. Here, we identify a G-to-U transversion (nucleotide 26372) in the SARS-CoV-2 E gene in three specimens with reduced viral detection efficiency using a widely available commercial assay. Further analysis of the public GISAID repository led to the identification of 18 additional genomes with this mutation, which reflect five independent mutational events. This work supports the use of dual-target assays to reduce the number of false-negative PCR results.