Few studies have evaluated the efficacy of ceftazidime–avibactam (CA) for Klebsiella pneumoniae carbapenemase-producing Enterobacterales bacteremia (KPC-PEB) in high-risk neutropenic patients. This is a prospective multicenter observational study in high-risk neutropenic patients with multi-drug resistant Enterobacterales bacteremia. They were compared according to the resistance mechanism and definitive treatment provided: KPC-CPE treated with CA (G1), KPC-CPE treated with other antibiotics (G2), and patients with ESBL-producing Enterobacterales bacteremia who received appropriate definitive therapy (G3). Thirty-day mortality was evaluated using a logistic regression model, and survival was analyzed with Kaplan–Meier curves. A total of 238 patients were included: 18 (G1), 52 (G2), and 168 (G3). Klebsiella spp. (60.9%) and Escherichia coli (26.4%) were the Enterobacterales most frequently isolated, and 71% of the bacteremias had a clinical source. The resistance profile between G1 and G2 was colistin 35.3% vs. 36.5%, amikacin 16.7% vs. 40.4%, and tigeclycline 11.1% vs. 19.2%. The antibiotics prescribed in combination with G2 were carbapenems, colistin, amikacin, fosfomycin, tigecycline, and fluoroquinolones. Seven-day clinical response in G1 vs. G2 vs. G3 was 94.4% vs. 42.3% vs. 82.7%, respectively (p < 0.001). Thirty-day overall mortality in G1 vs. G2 vs. G3 was 22.2% vs. 53.8% vs. 11.9%, respectively (p < 0.001), and infection-related mortality was 5.5% vs. 51.9% vs. 7.7% (p < 0.001). The independent risk factors for mortality were Pitt score > 4: OR 3.63, 95% CI, 1.18–11.14 (p = 0.025) and KPC-PEB treated with other antibiotics: OR 8.85, 95% CI, 2.58–30.33 (p = 0.001), while 7-day clinical response was a protective factor for survival: OR 0.02, 95% CI, 0.01–0.08 (p < 0.001). High-risk neutropenic patients with KPC-CPE treated with CA had an outcome similar to those treated for ESBL-producing Enterobacterales, with higher 7-day clinical response and lower overall and infection-related mortality than those treated with other antibiotics. In view of these data, CA may be considered the preferred therapeutic option for KPC-PEB in high-risk neutropenic patients.

Identifying the risk factors for carbapenem-resistant Enterobacterales (CRE) bacteremia in cancer and hematopoietic stem cell transplantation (HSCT) patients would allow earlier initiation of an appropriate empirical antibiotic treatment. This is a prospective multicenter observational study in patients from 12 centers in Argentina, who presented with cancer or hematopoietic stem-cell transplant and developed Enterobacterales bacteremia. A multiple logistic regression model identified risk factors for CRE bacteremia, and a score was developed according to the regression coefficient. This was validated by the bootstrap resampling technique. Four hundred and forty-three patients with Enterobacterales bacteremia were included: 59 with CRE and 384 with carbapenem-susceptible Enterobacterales (CSE). The risk factors that were identified and the points assigned to each of them were: ≥10 days of hospitalization until bacteremia: OR 4.03, 95% CI 1.88–8.66 (2 points); previous antibiotics > 7 days: OR 4.65, 95% CI 2.29–9.46 (2 points); current colonization with KPC-carbapenemase-producing Enterobacterales: 33.08, 95% CI 11.74–93.25 (5 points). With a cut-off of 7 points, a sensitivity of 35.59%, specificity of 98.43%, PPV of 77.7%, and NPV of 90.9% were obtained. The overall performance of the score was satisfactory (AUROC of 0.85, 95% CI 0.80–0.91). Finally, the post-test probability of CRE occurrence in patients with none of the risk factors was 1.9%, which would virtually rule out the presence of CRE bacteremia.

The epidemiology of bacteremia and the antibiotic resistance profile (ARP) of Gram-negative bacilli (GNB) in hematological malignancies (HM) and hematopoietic stem cell transplant (HSCT) patients may differ according to geographic region. In addition, multidrug-resistant organisms (MDROs) may impact mortality. This is a prospective, observational, and multicenter study. The first episodes of bacteremia in adult patients with HM or HSCT were included. The risk factors for 30-day mortality were identified. One thousand two hundred and seventy-seven episodes were included (HM: 920; HSCT: 357). GNB were isolated in 60.3% of episodes, with Enterobacterales (46.9%) and P. aeruginosa (8.5%) being the most frequent. Gram-positive cocci were isolated in 41.9% of episodes, with coagulase-negative staphylococci (19.8%) and S. aureus (10.4%) being the most frequent. MDROs were isolated in 40.2% (24.4% GNB). The ARP of GNB in patients with HM vs. HSCT was cefepime: 36.8% vs. 45.7% (p = 0.026); piperacillin–tazobactam: 31.05% vs. 45.2% (p < 0.0001); carbapenems: 18.9% vs. 27.3% (p = 0.012); and aminoglycosides: 9.3% vs. 15.4% (p = 0.017), respectively. Overall mortality between patients with HM and HSCT was 17.5% vs. 17.6% (p = 0.951), respectively. The risk factors for mortality were relapsed and refractory underlying disease, corticosteroids use, respiratory source, septic shock, and GNB resistant to meropenem, while 7-day clinical response was a protective factor for survival. Bacteremia was frequently caused by GNB, with a large proportion of MDROs and a high level of antibiotic resistance, especially in patients with HSCT. Carbapenem-resistant GNB bacteremia was associated with a significant increase in mortality.

Data about short courses of antibiotic therapy for Gram-negative bacilli (GNB) bacteremia in immunosuppressed patients are limited. This is a prospective observational study performed on adult patients with cancer and hematopoietic stem cell transplant (HSCT) who developed GNB bacteremia and received appropriate empirical antibiotic therapy (EAT), had a clinical response within 7 days and survived 48 h after the end of therapy. They received antibiotic therapy in the range of 7–15 days and were divided into short course, with a median of 7 days (SC), or long course, with a median of 14 days (LC). Seventy-four patients were included (SC: 36 and LC: 38). No differences were observed in baseline characteristics or in the presence of neutropenia: 58.3% vs. 60.5% (p = 0.84). Clinical presentation and microbiological characteristics were similar in SC and LC, respectively: clinical source of bacteremia 72.2% vs. 76.3% (p = 0.68); shock 2.8% vs. 10.5% (p = 0.35) and multidrug-resistant GNB 27.8% vs. 21.1% (p = 0.50). Overall, mortality was 2.8% vs. 7.9% (p = 0.61), and bacteremia relapse was 2.8% vs. 0 (p = 0.30). The length of hospitalization since bacteremia was 7 days (interquartile range (IQR), 6–15) for SC and 12 days (IQR, 7–19) (p = 0.021) for LC. In the case of patients with cancer or HSCT and GNB bacteremia who receive appropriate EAT with clinical response, 7 days of antibiotic therapy might be adequate.

Ceftazidime-avibactam (CA) and CA plus aztreonam (ATM) are the preferred treatment options for KPC and MBL carbapenemase-producing Enterobacterales infections (CPEis). All episodes of monomicrobial CPEis in immunosuppressed patients (IPs) admitted from May 2019 to November 2024, who received definitive antibiotic therapy (AT) with CA or CA + ATM for at least 72 h, were prospectively included. Bacteremic episodes (BEs) and non-bacteremic episodes (NBEs) were compared. Logistic regressions adjusted by propensity score were used to identify variables associated with 30-day overall mortality. In total, 82 CPEis were included (38 NBEs and 44 BEs). BEs more frequently occurred in hematological malignancies (52.3% vs. 15.8%, p = 0.0006), while NBEs were more commonly observed in solid organ transplantation (73.7% vs. 34.1%, p = 0.001). K. pneumoniae was the main isolated microorganism; KPC-CPE was the most common resistance mechanism in both groups, followed by MBL-CPE. The 7-day clinical response, 30-day overall and infection-related mortality between NBEs and BEs were 92.1% vs. 88.6%, p = 0.59, 10.5% vs. 27.3%, p = 0.09, and 2.6% vs. 13.6%, p = 0.11. Septic shock, OR 6.5, 95% CI, 1.58–26.72 (p = 0.01), and refractory malignancy, OR 5.6, 95% CI, 1.03–30.14 (p = 0.046), were associated with 30-day mortality, whereas BEs were not, OR 1.5, 95% CI, 0.36–6.2 (p = 0.56). CPEis in both NBE and BE IPs who received definitive AT with CA or CA + ATM correlated with a high rate of 7-day clinical response and low 30-day infection-related mortality. Underlying malignancy and disease severity were associated with 30-day overall mortality. Regional knowledge of bacterial antibiotic resistance enables the implementation of individualized AT to improve patient survival.

Introducción: Staphylococcus aureus resistente a meticilina adquirido en la comunidad (SARM) es un colonizador de la piel y las mucosas humanas, y esta colonización es un factor de riesgo para las infecciones causadas por este microorganismo. Se desconoce el papel que desempeñan los caninos y felinos domésticos (CF) en la colonización humana. El objetivo de este estudio fue demostrar la asociación entre el aislamiento de SARM en muestras clínicas de infecciones de piel y tejidos blandos (IPPB) en adultos que conviven con CF. Material y métodos: Se utilizó un modelo retrospectivo de casos (IPPB con aislamiento de SARM) y controles (IPPB sin aislamiento de SARM). Se incluyeron 166 episodios de IPPB tratados en dos hospitales de Buenos Aires, Argentina, entre octubre de 2014 y enero de 2018. Las muestras se obtuvieron mediante punción a través de piel sana y el material obtenido se sembró en medios de cultivo habituales. Para la identificación bacteriana se utilizaron espectrometría de masas y nefelometría automatizada. La resistencia a la meticilina se confirmó mediante difusión con discos de cefoxitina. Se recopilaron datos sobre los hábitos de convivencia con CF y los factores de riesgo clásicos para IPPB causadas por SARM. Resultados: Los pacientes con IPPB debidas a SARM conviven más con CF (OR bruto 1.9; [1.1-3.7] p<0.05) y tienden a tener una convivencia más cercana con ellos (OR bruto 1.8; [0.99-3.43] p=0.08). En el análisis multivariable, aquellos que conviven estrechamente con CF tienen 1.3 veces más probabilidades de sufrir IPPB debidas a SARM (OR ajustado 2.32; [1.12-4.78] p<0.02). Conclusiones: Concluimos que existe una asociación entre las IPPB por SARM en humanos y la convivencia con CF.