Analysis of Porcine Model of Fecal-Induced Peritonitis Reveals the Tropism of Blood Microbiome

Recent studies have suggested the existence of a blood microbiome in the healthy host. However, changes in the blood microbiome upon bloodstream infection are not known. Here, we analyzed the dynamics of the blood microbiome in a porcine model of polymicrobial bacteremia induced by fecal peritonitis. Surprisingly, we detected bacterial populations in the bloodstream even before the infection, and these populations were maintained over time. The native blood microbiome was notably taxonomically different from the fecal microbiome that was used to induce peritonitis, reflecting microbial tropism for the blood. Although the population composition after the infection was similar to that of the native blood microbiome, new bacterial strains entered the bloodstream upon peritonitis induction as clinical symptoms relevant to sepsis developed. This indicates that the bacteria detected in the blood before peritonitis induction were derived from the blood rather than a contamination. Comparison of the functional pathways enriched in the blood and fecal microbiomes revealed that communication and stress management pathways are essential for the survival of the blood microbiome.

Complete Genome Sequence of Acinetobacter junii Strain INC8271, Isolated from a Patient with Metastatic Cancer and Bacteremia

Acinetobacter junii INC8271 was isolated from a cancer patient with polymicrobial bacteremia after biliary stent placement. The complete genome sequence consisted of a chromosome of 3,530,883 bp (GC content, 38.56%) with 3,377 genes, including those encoding 74 tRNAs and 18 rRNAs, and two intact prophage sequences. No antibiotic resistance genes were detected.

Management of enterococcal central line-associated bloodstream infections in patients with cancer

Objective Enterococcus species are the third most common organisms causing central line-associated bloodstream infections (CLABSIs). The management of enterococcal CLABSI, including the need for and timing of catheter removal, is not well defined. We therefore conducted this study to determine the optimal management of enterococcal CLABSI in cancer patients. Methods We reviewed data for 542 patients diagnosed with Enterococcus bacteremia between September 2011 to December 2018. After excluding patients without an indwelling central venous catheter (CVC), polymicrobial bacteremia or with CVC placement less than 48 h from bacteremia onset we classified the remaining 397 patients into 3 groups: Group 1 (G1) consisted of patients with CLABSI with mucosal barrier injury (MBI), Group 2 (G2) included patients with either catheter-related bloodstream infection (CRBSI) as defined in 2009 Clinical Practice Guidelines for the Diagnosis and Management of Intravascular Catheter-Related Infection by the Infectious Diseases Society of America (IDSA) or CLABSI without MBI, and Group 3 (G3) consisted of patients who did not meet the CDC criteria for CLABSI. The impact of early (< 3 days after bacteremia onset) and late (3–7 days) CVC removal was compared. The composite primary outcome included absence of microbiologic recurrence, 90-day infection-related mortality, and 90-day infection-related complications. Results Among patients in G2, CVC removal within 3 days of bacteremia onset was associated with a trend towards a better overall outcome than those whose CVCs were removed later between days 3 to 7 (success rate 88% vs 63%). However, those who had CVCs retained beyond 7 days had a similar successful outcome than those who had CVC removal < 3 days (92% vs. 88%). In G1, catheter retention (removal > 7 days) was associated with a better success rates than catheter removal between 3 and 7 days (93% vs. 67%, p = 0.003). In non-CLABSI cases (G3), CVC retention (withdrawal > 7 days) was significantly associated with a higher success rates compared to early CVC removal (< 3 days) (90% vs. 64%, p = 0.006). Conclusion Catheter management in patients with enterococcal bacteremia is challenging. When CVC removal is clinically indicated in patients with enterococcal CLABSI, earlier removal in less than 3 days may be associated with better outcomes. Based on our data, we cannot make firm conclusions about whether earlier removal (< 3 days) could be associated with better outcomes in patients with Enterococcal CLABSI whose CVC withdrawal is clinically indicated. In contrast, it seemed that catheter retention was associated to higher success outcome rates. Therefore, future studies are needed to clearly assess this aspect.

Streptococcus pyogenes Infective Endocarditis – Association with Injection Drug Use: Case Series and Review of the Literature

Background Streptococcus pyogenes, or Group A Strep (GAS), is not considered a typical cause of infective endocarditis (IE), but has anecdotally been observed in unexpectedly high rates in people who inject drugs (PWID) at our institution. Methods All cases of possible or definite GAS IE per Modified Duke Criteria in adults at an academic hospital between 11/15/2015 and 11/15/2020 were identified. Medical records were reviewed for demographics, comorbidities, treatment, and outcomes related to GAS IE. Literature on cases of GAS IE was reviewed. Results 18 cases of probable (11) or definite (7) GAS IE were identified; mean age was 38 years, and the population was predominantly female (56%) and Caucasian (67%), which is inconsistent with local population demographics. Sixteen cases were in people who inject drugs (PWID) (89%), 14 were also homeless, six were also living with HIV (33%), and two were also pregnant. Antibiotic regimens were variable due to polymicrobial bacteremia (39%). One patient underwent surgical valve replacement. Four patients (22%) died due to complications of infection. Literature review revealed 42 adult cases of GAS IE, only 17 of which were in PWID (24%). Conclusions The 16 cases of possible and definite GAS IE in PWID over a five-year period in a single institution reported nearly doubles the number of cases in PWID from all previous reports. This suggests a potential increase in GAS IE particularly in PWID and PLWH, which warrants further epidemiologic investigation.

Analysis of the blood microbiome in a porcine model of fecal-induced peritonitis

BackgroundRecent studies have proposed the existence of a blood microbiome, even in the healthy host. However, we do not know how the blood microbiome changes when a bloodstream infection (BSI) occurs. Here, we analyzed the dynamics of the blood microbiome in a porcine model of polymicrobial bacteremia induced by fecal peritonitis. Serial blood samples were taken over 12 hours post-induction of fecal peritonitis, and BSI was validated by conventional blood culture and assessment of clinical symptoms.ResultsThe bacterial populations in the blood microbiome were retained throughout the experimental period. However, there were significant taxonomic differences between the profile in the fecal and blood microbiomes, reflecting tropism for the blood environment. We also confirmed that the microbiota we detected was not contaminated by low mass bacteria in the bloodstream. However, at the same time, we noted a slight increase in Bacteroidetes, which is a major component of the gut microbiome, as sepsis developed. Comparison of the functional pathways in the blood and fecal microbiomes revealed upregulation of pathways involved in environmental interactions, and downregulation of those related to cell proliferation, in the former. Based on the enriched biological pathways, we concluded that communication and stress management pathways are essential for the survival of the blood microbiome under harsh conditions.ConclusionThis study suggests that the microbiota can be stably retained in the bloodstream over time. Although further investigation in humans is required, we suggest that the blood microbiome may be another factor to be considered in the context of BSI and subsequent sepsis.

Limited Clinical Utility of Follow-up Blood Cultures in Patients With Streptococcal Bacteremia: An Opportunity for Blood Culture Stewardship

Background The value of positive follow-up blood cultures (FUBCs) in streptococcal bacteremia has not been well defined. Therefore, we explored the frequency of and risk factors for positive FUBC in a retrospective cohort of patients with streptococcal bacteremia. Methods Adults ≥18 years of age, admitted with at least 1 positive blood culture for Streptococcus spp between 2013 and 2018 followed by at least 1 FUBC, were potentially eligible. Positive FUBCs were defined as cultures positive for the same streptococcal species drawn &gt;24 hours after the index culture. We excluded patients with polymicrobial bacteremia. We compared the characteristics of patients with and without a positive FUBC. Results In our single-center cohort, we identified 590 patients with streptococcal bacteremia, and 314 patients met inclusion criteria. Ten patients had FUBC with Streptococcus spp (3.2%), 4 (1.3%) had a contaminant identified, and 3 (1.0%) had a new pathogen isolated. Endocarditis (5 of 10 [50.0%] vs 35 of 304 [11.5%]), epidural abscess (2 of 10 [20%] vs 4 of 304 [1.3%]), and discitis or vertebral osteomyelitis (3 of 10 [30.0%] vs 14 of 304 [4.6%]) were associated with positive FUBC. Patients with positive FUBC had a longer median length of stay (12.9 vs 7.1 days, P = .004) and longer duration of antibiotic treatment (14.9 vs 43.2 days, P = .03). Conclusions Follow-up blood cultures among patients with streptococcal BSI are rarely positive. Clinicians could consider limiting follow-up blood cultures in patients at low risk for deep-seated streptococcal infections, persistent bacteremia, or endovascular infection.

Outcomes of Rapid Identification of Bacteremia in Combination with Antimicrobial Stewardship Intervention

Background: Rapid diagnostic tests designed to provide bacterial identification and detection of resistance genes directly from positive blood cultures can significantly reduce the time to definitive results, ensuring appropriate and timely antibiotic administration while simultaneously decreasing antibiotic overuse and development of antimicrobial resistance. However, their impact on in-hospital mortality and length of stay (LOS) is yet to be fully assessed. Methods: We retrospectively reviewed bacteremia cases in patients hospitalized over a 6-month period before (n = 78) and after (n = 93) the implementation of Verigene bacterial nanoparticle testing. Exclusion criteria included age >90 years, bacteremia thought to be a contaminant, polymicrobial bacteremia, or hospice admission. Verigene was performed at a central laboratory from 6 a.m. to 11 p.m. Pharmacists notified physicians of results and assisted with antibiotic modifications. Patient demographics, time to organism identification, time to effective antimicrobial therapy, and other key clinical parameters were compared. The primary outcomes were in-hospital LOS, 14-day mortality, and 30-day mortality. Secondary outcomes included time to effective antibiotic therapy and intensive care unit (ICU) LOS. Results: Organism identification was achieved more quickly (4.9 hours vs 44.5 hours; P < .001) and effective antibiotic therapy was started earlier after Verigene implementation. The mean in-hospital LOS decreased from 13.15 days to 10.02 days (P = .0071) after the Verigene intervention, despite a higher mean Charlson comorbidity index among the cases. Mortality was similar between groups. Conclusions: Rapid identification of gram-positive and gram-negative bacteremia with an antimicrobial stewardship intervention can decrease time to effective antibiotic therapy and total LOS.Funding: NoneDisclosures: None