Citations

Plazomicin was tested against 697 recently acquired carbapenem-resistant Klebsiella pneumoniae isolates from the Great Lakes region of the United States. Plazomicin MIC 50 and MIC 90 values were 0.25 and 1 mg/liter, respectively; 680 isolates (97.6%) were susceptible (MICs of ≤2 mg/liter), 9 (1.3%) intermediate (MICs of 4 mg/liter), and 8 (1.1%) resistant (MICs of >32 mg/liter). Resistance was associated with rmtF -, rmtB -, or armA -encoded 16S rRNA methyltransferases in all except 1 isolate.

AbstractBackgroundCurrent approaches in tracking Clostridioides difficile infection (CDI) and individualizing patient management are incompletely defined.MethodsWe recruited 468 subjects with CDI at Mayo Clinic Rochester between May and December 2016 and performed whole-genome sequencing (WGS) on C. difficile isolates from 397. WGS was also performed on isolates from a subset of the subjects at the time of a recurrence of infection. The sequence data were analyzed by determining core genome multilocus sequence type (cgMLST), with isolates grouped by allelic differences and the predicted ribotype.ResultsThere were no correlations between C. difficile isolates based either on cgMLST or ribotype groupings and CDI outcome. An epidemiologic assessment of hospitalized subjects harboring C. difficile isolates with ≤2 allelic differences, based on standard infection prevention and control assessment, revealed no evidence of person-to-person transmission. Interestingly, community-acquired CDI subjects in 40% of groups with ≤2 allelic differences resided within the same zip code. Among 18 subjects clinically classified as having recurrent CDI, WGS revealed 14 with initial and subsequent isolates differing by ≤2 allelic differences, suggesting a relapse of infection with the same initial strain, and 4 with isolates differing by >50 allelic differences, suggesting reinfection. Among the 5 subjects classified as having a reinfection based on the timing of recurrence, 3 had isolates with ≤2 allelic differences between them, suggesting a relapse, and 2 had isolates differing by >50 allelic differences, suggesting reinfection.ConclusionsOur findings point to potential transmission of C. difficile in the community. WGS better differentiates relapse from reinfection than do definitions based on the timing of recurrence.

Introduction. Post-operative meningitis (POM) is a life-threatening complication of neurosurgery. Diagnosis is often difficult due to pre-existing inflammation and antecedent antimicrobial use. Bacterial cerebrospinal fluid (CSF) cultures may reveal no growth, but empiric antibiotics are typically given due to the high morbidity and mortality associated with POM. 16S rRNA gene PCR/sequencing is a molecular methodology that can identify the presence of bacteria regardless of viability for culture. Case Presentation. A patient presented with a rapid onset of fever associated with headache, neck pain, nausea and altered mental status 11 days after undergoing laser interstitial thermal therapy for treatment of recurrent astrocytoma at another hospital. Based on clinical presentation and imaging, POM was suspected, and empiric antibacterial therapy was started. Microbiological stains and cultures of CSF were negative. Due to persistent fevers, 16S rRNA gene PCR/sequencing was done on CSF; it detected a member of the order Enterobacteriales most closely resembling Serratia species. All antimicrobials were stopped except for cefepime, which was given for 2 weeks. The patient’s mental status fully recovered. Conclusion. The application of 16S rRNA gene PCR/sequencing in the setting of POM is of value by improving the quality of patient care and decreasing costs by antimicrobial de-escalation. Further studies regarding the positive and negative predictive values of this test are required.

AbstractBackgroundPlasma ammonia is commonly measured in the diagnostic evaluation of hospitalized newborns, but reference values are not well defined.MethodsWe prospectively enrolled newborns admitted to the level III/IV neonatal intensive care unit and level II intermediate special care nursery from January 2017 to January 2018. Infants with inborn errors of metabolism or liver disease were excluded. Plasma ammonia concentrations were measured once within the first week of life and evaluated by sex, gestational age, timing of the draw, blood collection method, and type of nutrition. Reference intervals were calculated.Results127 neonates were included; one third (34%) were term infants born at ≥37 weeks gestation, and two thirds (66%) were born preterm at <37 weeks gestation. Median plasma ammonia concentrations were 32 μmol/L (range <10 to 86 μmol/L). Median ammonia concentrations were higher among preterm compared to term infants (35 vs. 28 μmol/L, p = 0.0119), and term female compared to term male infants (34 vs. 26 μmol/L, p = 0.0228). There was no difference in median ammonia concentrations between female and male preterm infants, based on gestational age within the preterm group, timing of the blood draw, presence of hyperbilirubinemia, blood collection method, or type of nutritional intake.ConclusionsPlasma ammonia concentrations among newborns are higher than the expected adult concentrations and may vary by gestational age and sex. Blood collection method, type of nutrition, hyperbilirubinemia, and timing of the draw do not impact concentrations. We propose a reference limit of ≤82 μmol/L for newborns less than one week of age.

The antibiofilm activity of a hydrogen peroxide-generating electrochemical scaffold (e-scaffold) was determined against mono- and trispecies biofilms of methicillin-resistant Staphylococcus aureus , multidrug-resistant Pseudomonas aeruginosa , and Candida albicans . Significant time-dependent decreases were found in the overall CFU of biofilms of all three monospecies and the trispecies forms. Confocal laser scanning microscopy showed dramatic reductions in fluorescence intensities of biofilm matrix protein and polysaccharide components of e-scaffold-treated biofilms.

An evaluation was undertaken to determine the optimal method for testing the susceptibilities of 100 clinical isolates and two reference strains of Enterococcus spp. to vancomycin in vitro. Six testing methods were studied by using the following media and incubation times: agar screen with the Synergy Quad Plate (Remel, Lenexa, Kans.), an in-house-prepared brain heart infusion (BHI) agar plate, and an in-house-prepared Mueller-Hinton (MH) agar plate, all incubated for 24 or 48 h; broth microdilution (Sensititre Just One Strip; AccuMed International, Inc., West Lake, Ohio) with BHI or cation-adjusted MH broth incubated for 24 or 48 h; agar dilution with BHI or MH agar incubated for 24 or 48 h; epsilometer test (E test; AB BioDisk, Solna, Sweden) with BHI or MH agar incubated for 24 or 48 h; disk diffusion with BHI or MH agar incubated for 24 or 48 h; and the automated Vitek method with the gram-positive susceptibility Staphylococcus aureus card and R02.03 software (bioMerieux, Inc., Hazelwood, Mo.). Growth failures occurred with MH media (n = 6) but not with BHI media. One growth failure occurred with the Vitek method. Results for each testing method for each Enterococcus strain were interpreted as susceptible, intermediate, or resistant according to current National Committee for Clinical Laboratory Standards (NCCLS) criteria and compared to the vancomycin resistance genotype (i.e., vanA, vanB, vanC-1, or vanC-2/3). For all methods, extension of the incubation time from 24 h to 48 h either produced no difference in the results or gave poorer results. The following methods produced no very major or major interpretive errors: broth microdilution with BHI media incubated for 24 h, agar dilution with BHI media incubated for 24 or 48 h, and E test with BHI media incubated for 24 or 48 h. Unacceptable frequencies of very major errors (> 1%) occurred with all methods for which MH media were used. Minor interpretive errors were frequent with all methods. These minor interpretive errors also occurred most frequently with Enterococcus strains with vanC genes, which encoded low-level vancomycin resistance (MIC < or = 8 microg/ml), as opposed to Enterococcus strains which possessed vanA or vanB genes, which encoded higher-level vancomycin resistance (MIC > or = 64 microg/ml). Modification of NCCLS breakpoints, especially for motile Enterococcus spp. (E. casseliflavus, E. flavescens, and E. gallinarum), may resolve this problem; however, in the current study, one E. faecalis strain and one E. faecium strain carried only the vanC gene. The agar screen method may also require reformulation. The current agar screen plate contains 6 microg of vancomycin per ml, which may not detect all low-level resistance associated with vanC genotypes. Nevertheless, the clinical significance of this low-level vancomycin resistance remains unknown.

Reliable nucleic acid extraction techniques for blood specimens are required for the sensitive detection of viral DNA. Standardized procedures for processing blood specimens for the molecular detection of herpesviruses (cytomegalovirus [CMV], herpes simplex virus, varicella-zoster virus, and Epstein-Barr virus [EBV]) have not been established. Three methods were used to extract DNA from blood specimens from healthy donors and asymptomatic immunocompromised patients: (i) IsoQuick treatment of whole blood, (ii) extraction of the peripheral blood leukocytes by lysis (lysis buffer and proteinase K), and (iii) extraction of peripheral blood leukocytes with phenol-chloroform (sodium docecyl sulfate solution and proteinase K). All blood specimens from 25 healthy blood donors were negative for CMV, herpes simplex virus and varicella-zoster virus nucleic acid sequences, regardless of the extraction method, while three samples (12%) extracted by the lysis technique were positive for EBV DNA. Of 25 blood samples from asymptomatic immunocompromised patients, CMV and EBV each were detected in nine specimens by lysis extraction, four each by IsoQuick and four (CMV) and six (EBV) by the phenol-chloroform method. Our results indicate that the lysis method is optimal for the detection of CMV and EBV DNA sequences by PCR from the leukocytic fraction of blood specimens. DNA of these viruses is frequently present in blood specimens from asymptomatic immunocompromised patients and occasionally from healthy donors.

Cytomegalovirus (CMV) viremia is a widely used laboratory marker of CMV disease following transplantation and is additionally used to trigger preemptive antiviral therapy. Despite this, the optimal method for diagnosing CMV viremia in transplantation recipients remains unknown. To determine the sampling frequency and blood volume required for the optimal diagnosis of viremia by shell vial assay, a prospective study of 46 viremic transplantation recipients was conducted. Blood specimens (2.5 and 5 ml) were collected twice, 3 h apart, at a median of 1.4 days (range, 1 to 3 days) after the triggering shell vial-positive blood had been collected. Considering a single 2.5-ml specimen, an average of only 40% of previously viremic patients had documented CMV in their blood: this increased to 50% when a second 2.5-ml sample of blood was collected 3 h later. The yields of two 2.5-ml versus two 5-ml samples were 50 versus 61%, respectively. Viremia as detected by shell vial assay is intermittent, and increasing the frequency and volume of blood sampling increases its diagnosis. These results have implications in diagnosis of CMV infection and its preemptive therapy.

Vancomycin-resistant enterococci (VRE) are increasingly isolated from clinical specimens. One hundred clinical isolates of enterococci (E. casseliflavus/E. flavescens [n = 10], E. faecalis [n = 34], E. faecium [n = 43], E. avium [n = 1], E. gallinarum [n = 11], and E. raffinosus [n = 1]) were examined for the presence of vanA, vanB, vanC-1, and vanC-2/3 genes by a single multiplex PCR performed directly with colonies from blood agar plates. Six previously characterized VRE strains which carry either vanA, vanB, vanC-1, or vanC-2 genes were used as controls. To discriminate among van genes, the PCR amplicons were digested with MspI and were electrophoresed on agarose gels. Because of significant sequence homology between vanC-2 and vanC-3 genes, this assay is unable to discriminate these genes from each other; therefore, these are referred to as vanC-2/3 genes. PCR products were detected in 63 of the 100 clinical isolates. The restriction fragment length patterns were consistent with vanA for 10 strains, vanB for 30 strains, vanC-1 for 12 strains, vanC-2 for 6 strains, and vanA and vanC-1 for 1 strain. The vancomycin MICs for the isolates with restriction fragment length patterns consistent with vanA and vanB were all > and = 64 micrograms/ml. The vancomycin MICs for the isolates with restriction fragment length patterns consistent with vanC-1 or vanC-2 were 4 to 8 micrograms/ml. The vancomycin MICs for the isolates from which no PCR amplicons were produced were 2 to 4 micrograms/ml. A PCR product was produced in four isolates (vancomycin MICs, 4 to > 256 micrograms/ml) with restriction fragment length patterns differing from those for the control vanA, vanB, vanC-1, and vanC-2 isolates. DNA sequencing of these amplicons revealed that two of the four isolates had nucleic acid sequences which were closely related to the published sequence for the vanB gene and two had nucleic acid sequences which were closely related to the published sequence for the vanC-2 and vanC-3 genes. Multiplex PCR-restriction fragment length polymorphism appears to be a useful and convenient method for rapidly detecting and discriminating genotypes for vancomycin-resistant Enterococcus spp. in the clinical laboratory. In instances in which unusual restriction fragment patterns of PCR amplicons occur, DNA sequencing can be performed to discriminate van genotypes.

We prospectively studied the utility of the amplification of cytomegalovirus (CMV) DNA in the sera of liver transplant recipients in order to predict symptomatic CMV infection, thus enabling preemptive therapy with antiviral agents. Serum samples obtained at biweekly intervals from 20 sequential liver transplant recipients for at least 8 weeks following transplantation were tested by the PCR amplification procedure. Results were correlated with blood and urine cultures, histopathological findings from infected organs, and clinical manifestations. Six patients (30%) developed symptomatic CMV infection; in five (83%) of these patients, CMV DNA was detected prior to symptomatic CMV infection, and in one (17%) of these patients, CMV DNA was detected at the time of symptomatic CMV infection. CMV DNA was detected a mean of 13 days (range, 0 to 23 days) prior to the onset of symptomatic CMV infection. In addition, CMV DNA was detected in the sera of four of five patients with asymptomatic viremia and two patients with asymptomatic viruria. Lastly, the PCR was negative for sera from seven patients with no evidence of CMV infection. We found that PCR was able to detect the presence of CMV DNA in the sera of liver transplant recipients at a sensitivity of 92% and a specificity of 100% for CMV infection, while the sensitivity and specificity for symptomatic infection were 100 and 57%, respectively.