Shannon, Samantha

Abstract Antibiotics are critical complements to the immune response in combatting infection. Anaerobic bacteria are increasingly common causes of infection, and antibiotic resistance of anaerobes has been rising. Most laboratories do not perform antimicrobial susceptibility testing of anaerobes, and even fewer have compiled antibiogram data. Here we investigated antimicrobial susceptibility results of anaerobes from January 2012 to December 2021 obtained from inpatients at Mayo Clinic using reference agar dilution testing. Actinomyces (60–70 isolates annually), Bacteroides fragilis (30–80), Finegoldia magna (40–60), and Cutibacterium acnes (70–110) were included. Penicillin, clindamycin, metronidazole, ertapenem, piperacillin-tazobactam, and moxifloxacin were tested. Clinical and Laboratory Standards (CLSI) breakpoints were followed. B. fragilis showed ≥90% and Actinomyces 100% susceptibility to piperacillin-tazobactam and ertapenem. All F. magna and >95% B. fragilis were susceptible to metronidazole. The most striking fluctuations in percent susceptibility from year to year were observed for clindamycin, with Actinomyces ranging from 66–79%, B. fragilis 34–67%, and F. magna 47–85%. In the absence of local anaerobe antibiograms, providers may refer to such antibiogram data to guide empiric anti-anaerobic therapy at their institutions. In conclusion, anaerobe antibiotic susceptibility patterns must be monitored to ensure appropriate antibiotic empiric therapy and stewardship.

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-β-lactamase cfiA by the presence of an upstream insertion sequence (IS).

Abstract Introduction/Objective Matrix-assisted laser desorption ionization/ time-of-flight mass spectrometry (MALDI-TOF MS) direct from positive blood culture bottles has facilitated drastic drops in turn-around times for microorganism identification but has been poorly studied for anaerobes. We investigated the ability of MALDI-TOF to provide early anaerobe identification at 4 hours and 18-24 hours of growth on agar from anaerobic blood culture bottles. Additionally, we reviewed medical records of such patients to ascertain impact of early identification on antimicrobial treatment. Methods Over 9 months, we ran MALDI-TOF on early growth from blood cultures positive for growth in BACTEC™ Lytic/ 10 Anaerobic/F bottles. Broth from each bottle was subbed to sheep blood agar (4 hours, 5% CO2) and 2 CDC (BD-BBL™) anaerobic blood agar plates (examined 18-24 hours and 48 hours). Bruker Biotyper® RUO v7854 and Mayo Clinic Custom MALDI-TOF MS libraries were used for identification. Results 144/184 (78%) bottles resulted in growth of aerobic bacteria. Of the remaining bottles with growth of anaerobes, 38 were assessed by early MALDI-TOF. Early MALDI-TOF at 4 hours identified 3 Clostridium perfringens (8%) and an additional 26/38 (68%) isolates at 18-24 hours (both Gram-positive and –negative). Routine 48 hour identification was required for 9 (24%) isolates. In 7 cases, early MALDI-TOF resulted in a change to more appropriate antimicrobial therapy, most often for Bacteroides. Conclusion 29/38 (76%) of anaerobes from blood culture bottles were identified by early MALDI-TOF and reported to the clinician at least 24 hours before routine review of anaerobic sub plates for growth. All C. perfringens and Bacteroides were identified by 4 and 24 hours, respectively. Although early MALDI-TOF resulted in antimicrobial therapy adjustments in a minority of cases, it may allow for more targeted and earlier antimicrobial therapy. Early MALDI-TOF from anaerobic blood culture bottles should be considered for improved patient care and antimicrobial stewardship.

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.

ABSTRACT Culture of periprosthetic tissue specimens in blood culture bottles is more sensitive than conventional techniques, but the impact on laboratory workflow has yet to be addressed. Herein, we examined the impact of culture of periprosthetic tissues in blood culture bottles on laboratory workflow and cost. The workflow was process mapped, decision tree models were constructed using probabilities of positive and negative cultures drawn from our published study (T. N. Peel, B. L. Dylla, J. G. Hughes, D. T. Lynch, K. E. Greenwood-Quaintance, A. C. Cheng, J. N. Mandrekar, and R. Patel, mBio 7:e01776-15, 2016, https://doi.org/10.1128/mBio.01776-15 ), and the processing times and resource costs from the laboratory staff time viewpoint were used to compare periprosthetic tissues culture processes using conventional techniques with culture in blood culture bottles. Sensitivity analysis was performed using various rates of positive cultures. Annualized labor savings were estimated based on salary costs from the U.S. Labor Bureau for Laboratory staff. The model demonstrated a 60.1% reduction in mean total staff time with the adoption of tissue inoculation into blood culture bottles compared to conventional techniques (mean ± standard deviation, 30.7 ± 27.6 versus 77.0 ± 35.3 h per month, respectively; P < 0.001). The estimated annualized labor cost savings of culture using blood culture bottles was $10,876.83 (±$337.16). Sensitivity analysis was performed using various rates of culture positivity (5 to 50%). Culture in blood culture bottles was cost-effective, based on the estimated labor cost savings of $2,132.71 for each percent increase in test accuracy. In conclusion, culture of periprosthetic tissue in blood culture bottles is not only more accurate than but is also cost-saving compared to conventional culture methods.