Chesdachai, Supavit

Abstract Background Despite effective therapy for methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia with anti-staphylococcal penicillins (ASP; e.g., oxacillin, nafcillin) or cefazolin, persistent bacteremia is associated with poorer clinical outcomes and increased complications. Emerging strategies, such as combination therapy with an ASP or cefazolin and ertapenem, have demonstrated the potential to accelerate microbiologic clearance in persistent MSSA bacteremia. However, despite its increasing utilization in clinical practice, data on the effectiveness of this combination regimen remains limited. We sought to describe the clinical characteristics and outcomes of patients with MSSA bacteremia receiving combination therapy. Methods We performed a single-center, retrospective study of adult patients with MSSA bacteremia who received ASP or cefazolin and ertapenem combination therapy from 2019-2023. Time to blood culture clearance, in-hospital mortality, and 90-day relapse were examined. Results A total of 57 patients were included: median age of 65 years [IQR 53-73] with 75.4% male. MSSA bacteremia complicated by infective endocarditis and cardiac implantable electronic device infection occurred in 35.1% and 12.3%, respectively. The median length-of-stay was 16 days [IQR 12-28], and 57.9% required ICU admission. Forty (70.2%) patients underwent source control interventions such as valve replacement, device extraction or surgical debridement. The median duration of bacteremia prior to combination therapy initiation was 4 days [IQR 3-6]. Blood culture clearance occurred in a median of 1 day. The median duration of combination therapy was 4 days [IQR 3-6]. In-hospital mortality was 15.8%. None of the patients surviving the hospitalization experienced relapsed bacteremia within 90 days. Conclusion This study supports growing evidence that combination therapy may offer benefits in managing persistent MSSA bacteremia, specifically with regards to time to blood culture clearance. Further investigation is warranted to determine optimal timing of combination therapy and if known benefits of combination therapy translate into superior clinical outcomes as compared to monotherapy. Disclosures All Authors: No reported disclosures

Background. Measles, mumps, and rubella (MMR) in solid organ transplant (SOT) recipients is rare. We aim to investigate the pretransplant seroprevalence, MMR infection posttransplant, and whether immediate pretransplant MMR vaccination is associated with MMR infection. Methods. We queried the TriNetX database in December 2024 to assess (1) pretransplant MMR seroprevalence, (2) characteristics and outcomes of posttransplant MMR infections, and (3) outcomes for recipients who received the MMR vaccine within 30 d pretransplant. Only US data were included. MMR infection was identified through International Classification of Diseases (ICD) codes. Results. Among 313 548 SOT recipients identified in the database (from 2009 to 2024), IgG positivity for MMR was 72%, 80%, and 78% when available (~5% each). Based on ICD codes, posttransplant MMR infections occurred in 107 (0.03%), 124 (0.04%), and 38 (0.01%) recipients, respectively. The 90-d rejection rates were 36%, 27%, and 42%, whereas mortality rates were 7%, 8%, and 5%, respectively, in patients with MMR infection. Among 114 recipients vaccinated within 30 d pretransplant, none developed posttransplant MMR infections. Conclusions. Overall, posttransplant MMR infections in adult SOT recipients were uncommon in this data set, and no vaccine-associated infections were documented among those who received the MMR vaccine within 30 d pretransplant in real-world practice. The primary limitation of this study is that most MMR infections were identified using ICD codes without confirmation through serological testing or polymerase chain reaction, and we were unable to further characterize the infections because the de-identified database lacked information on the patient’s ZIP code and transplant hospital. Our study highlights the need for improvement in MMR serology screening and pretransplant MMR vaccination.

Abstract Background Recent clinical trial evidence supports broader use of partial oral therapy (POT) for infective endocarditis (IE), yet real-world uptake in the U.S. has not been investigated. Methods Adult infectious diseases (ID) physician members of the Infectious Diseases Society of America Emerging Infections Network were surveyed in April–May 2025. A 10-item instrument captured frequency of POT, organism-specific influence, decision factors, barriers, and facilitators. Results Among 1531 members, 516 (34%) responded; 452 (88%) of them managed IE. POT was uncommon: 16% never used, 53% used in ≤10% of cases, and only 10% used in >25% of patients. Frequent POT rose with caseload (23% in physicians treating >50 IE cases year vs ≤9% in lower-volume groups, P < .001) and with fewer years in clinical practice (13% in <5 yrs vs 5% in ≥25 yrs, P = .013). Comfort with POT depended on the pathogen: 66% were comfortable switching for Streptococcus spp., 52% for Gram-negative bacilli, 19% for methicillin-resistant Staphylococcus aureus. Three quarters of those who used POT finished with a single agent. In people who inject drugs, 34% of physicians often or always considered an oral regimen. Availability of an active oral agent (75%) and the pathogen involved (69%) were the leading decision drivers; principal barriers were fear of relapse (72%), adherence concerns (53%), and insufficient evidence (48%). Respondents most desired clearer guidelines (75%) and additional data (71%). Conclusions U.S. adult ID physicians adopt POT for IE sparingly. Updated IE treatment guidelines, additional clinical trial data, and broader access to complex outpatient antimicrobial therapy services may facilitate wider adoption.

ABSTRACT Achromobacter species are Gram-negative bacilli that predominantly affect individuals with cystic fibrosis or those with immunocompromising conditions. Clinical and microbiologic data on Achromobacter species are limited due to the rarity of these organisms and challenges with species-level identification. We conducted a 10-year retrospective analysis (1 January 2013 to 14 March 2023) of all bloodstream and non-bloodstream Achromobacter isolates identified at three tertiary-care Mayo Clinic locations (Minnesota, Arizona, and Florida). Additionally, we examined clinical characteristics of adult patients with Achromobacter bloodstream isolates. A total of 1,598 Achromobacter isolates, encompassing 1,545 non-bloodstream isolates and 53 bloodstream isolates, were identified. The most frequently identified species was Achromobacter xylosoxidans , though species-level identification was not possible for many isolates. Among adult patients with Achromobacter bloodstream infection, the mean age was 58.3 years (standard deviation ± 16.7), 73.1% had a central venous catheter, and 59.6% were immunocompromised. All-cause mortality was 10.2% at 30 days and 18.4% at 90 days. Bloodstream isolates exhibited greater than 90% susceptibility to meropenem, piperacillin-tazobactam, and trimethoprim-sulfamethoxazole. The respiratory tract was the most common source of non-bloodstream isolates (57.5%). Non-bloodstream isolates showed high susceptibility to imipenem (94.6%), piperacillin-tazobactam (92.8%), trimethoprim-sulfamethoxazole (92.1%), and meropenem (87.5%) while demonstrating significant resistance to fluoroquinolones and aminoglycosides. Our findings support the use of piperacillin-tazobactam, carbapenems, or trimethoprim-sulfamethoxazole as initial therapy for Achromobacter infections. Further research is needed to better define the clinical and microbiologic characteristics of Achromobacter infections. IMPORTANCE Achromobacter is a rare but important genus of bacteria that tends to cause infection in those with cystic fibrosis, recurrent healthcare exposures, and/or an immunocompromising condition. There is limited data on the clinical profile of Achromobacter infections as well as optimal antibiotic selection for affected patients. We conducted a retrospective study to improve understanding of the microbiologic and clinical characteristics of Achromobacter . Our study consists of a 10-year survey of all Achromobacter isolates processed by three Mayo Clinic tertiary-care centers in Minnesota, Florida, and Arizona from 2013 to 2023. We report multiple findings, including the clinical characteristics of patients with Achromobacter bloodstream infection, the number of different Achromobacter species identified, and the sources of isolates not obtained from blood cultures. We additionally present antimicrobial susceptibility results for Achromobacter isolates. Our study provides guidance to clinicians treating Achromobacter infections and, it is hoped, will facilitate ongoing study of Achromobacter .

ABSTRACT Background The available risk prediction models are inadequate to identify a true low‐risk patient for developing new‐onset atrial fibrillation (AF) after typical atrial flutter (AFL) ablation. We aimed to determine whether adding markers of atrial myopathy to HATCH score ( h ypertension, a ge ≥75 years, t ransient ischemic attack/stroke, c hronic obstructive pulmonary disease, and h eart failure) can improve prediction of new‐onset AF after ablation of typical AFL. Methods The study included 208 consecutive patients who underwent successful ablation of typical AFL at Minneapolis VA Medical Center and University of Minnesota Medical Center. Patients with history of AF prior to ablation were excluded. Results Among the 208 patients, 76 (36.5%) developed new‐onset AF post AFL ablation. Mean follow‐up duration was 62 ± 31.8 months. HATCH score was not associated with new‐onset AF. When adding atrial myopathy (presence of at least one of the following: PTFV 1 > 5000 µV*ms, interatrial block determined by biphasic inferior p wave with duration >120 ms, left atrium (LA) diameter ≥44 mm, or LA index ≥3 cm/m 2 ) to HATCH score (HATCH‐A 2 ), the combination was independently associated with new‐onset AF. The AF incidence between HATCH‐A 2 score of 0–1 and ≥2 were 6.7% and 40.5%, respectively (Odds ratio 9.04, 95% confidence interval: 2.05–39.81, p = 0.004). Particularly, when HATCH‐A 2 score was 0, none of the patients developed AF. Conclusions Adding atrial myopathy to HATCH score improved predictability and could be used to delineate a true low‐risk patient of new‐onset AF after typical AFL ablation.

Abstract Antifungal susceptibility testing among 1740 Candida parapsilosis blood isolates submitted to a United States reference laboratory (2015–2024) revealed a significant increase in fluconazole resistance from 8.2% to 20.3% (odds ratio [OR] per year, 1.13 [95% confidence interval {CI}, 1.06–1.20]; P < .001), with notable acceleration since 2021. Voriconazole resistance remained stable over this period. Micafungin resistance was rare, but intermediate susceptibility significantly increased, especially after 2021 (OR per year, 1.42 [95% CI, 1.25–1.63]; P < .001). These findings highlight important recent shifts in antifungal susceptibility among C parapsilosis isolates, emphasizing the need for ongoing surveillance and stewardship.

Background: The relationship between vegetation characteristics in Staphylococcus aureus infective endocarditis (IE) and blood culture time to positivity (TTP) has not been investigated. This study evaluates the correlation between vegetation length and TTP in patients with S. aureus IE. Methods: A retrospective cohort study was conducted that included 164 definite cases S. aureus IE. Vegetation length was determined by transesophageal echocardiography (TEE), and TTP was measured in hours from the initial time of blood culture incubation to positivity. Correlations between vegetation characteristics and TTP were analyzed using Spearman’s rank correlation coefficient. Results: A modest but statistically significant negative correlation was observed between vegetation length and TTP (Spearman ρ = −0.18, p = 0.020), suggesting that larger vegetations were associated with shorter TTP. No significant correlations were found for other vegetation characteristics (e.g., vegetation mobility, location, or number) and TTP. Conclusions: Larger vegetation size in S. aureus IE was associated with shorter TTP. These findings highlight the importance of vegetation size in the pathophysiology of S. aureus IE and its role in bacteremia dynamics.

Abstract Background There is a lack of comprehensive, large cohort studies investigating the predictors for severity and hospitalization in human granulocytic anaplasmosis (HGA). Methods We conducted a retrospective cohort study including all cases of HGA identified by positive blood Anaplasma polymerase chain reaction (PCR) at the Mayo Clinic Laboratory, Rochester between 2011 and 2021. Multivariable logistic regression was performed to evaluate risk factors associated with hospitalization. Results A total of 465 cases were identified. Of those, 67% (n = 312) were managed in the outpatient setting. Hospitalized patients (n = 153, 33%) were more likely to be older (median age of 71 vs 61; P ≤ .001) and immunocompromised (17% vs 7%; P ≤ .001). The triad of leukopenia, thrombocytopenia, and transaminitis was observed in 24% of the cases, but was associated with risk of hospitalization (odds ratio [OR] 1.78, 95% confidence interval [CI]: 1.05–3.03; P ≤ .033). The presence of a coinfection did not impact mortality or hospitalization. Conclusions The risk factors for hospitalization in patients with HGA include altered mental status, higher absolute neutrophil count (ANC), advanced age, comorbidities, and immunosuppression. The classic hematological and biochemical profile may be absent in the majority of cases. Co-testing may be of higher benefit in select cases.