pathogens Article Pseudomonas aeruginosa Bloodstream Infections in Patients with Cancer: Differences between Patients with Hematological Malignancies and Solid Tumors Cristina Royo-Cebrecos 1 , Julia Laporte-Amargós 2,3 , Marta Peña 4 , Isabel Ruiz-Camps 5 , Pedro Puerta-Alcalde 6 , Edson Abdala 7 , Chiara Oltolini 8 , Murat Akova 9 , Miguel Montejo 10 , Malgorzata Mikulska 11 , Pilar Martín-Dávila 12 , Fabian Herrera 13 , Oriol Gasch 14 , Lubos Drgona 15 , Hugo Manuel Paz Morales 16 , Anne-Sophie Brunel 17 , Estefanía García 18 , Burcu Isler 19 , Winfried V. Kern 20 , Zaira R. Palacios-Baena 21 , Guillermo Maestro de la Calle 22 , Maria Milagro Montero 23 , Souha S. Kanj 24 , Oguz R. Sipahi 25 , Sebnem Calik 26 , Ignacio Márquez-Gómez 27 , Jorge I. Marin 28 , Marisa Z. R. Gomes 29 , Philipp Hemmatti 30 , Rafael Araos 31 , Maddalena Peghin 32 , José Luis del Pozo 33 , Lucrecia Yáñez 34 , Robert Tilley 35 , Adriana Manzur 36 , Andrés Novo 37 , Jordi Carratalà 2,38,39 and Carlota Gudiol 2,3,38,39, *,† on behalf of the IRONIC study group 1 Internal Medicine Department, Hospital Nostra Senyora de Meritxell, Andorra Health Services (SAAS), AD700 Escaldes-Engordany, Andorra 2 Infectious Diseases Department, Bellvitge University Hospital, IDIBELL, University of Barcelona, 08907 Barcelona, Spain 3 Institut Català d’Oncologia (ICO), Hospital Duran i Reynals, IDIBELL, 08907 Barcelona, Spain 4 Hematology Department, Institut Català d’Oncologia (ICO)–Hospital Duran i Reynals, IDIBELL, Citation: Royo-Cebrecos, C.; Laporte-Amargós, J.; Peña, M.; 08907 Barcelona, Spain 5 Infectious Diseases Department, Vall d’Hebron University Hospital, 08035 Barcelona, Spain Ruiz-Camps, I.; Puerta-Alcalde, P.; 6 Infectious Diseases Department, Hospital Clínic i Provincial, 08035 Barcelona, Spain Abdala, E.; Oltolini, C.; Akova, M.; 7 Instituto do Câncer do Estado de São Paulo, Faculty of Medicine, Univesity of São Paulo, Montejo, M.; Mikulska, M.; et al. Sao Paulo 01246, Brazil Pseudomonas aeruginosa Bloodstream 8 Unit of Infectious and Tropical Diseases, IRCCS San Raffaele Scientific Institute, 20132 Milan, Italy Infections in Patients with Cancer: 9 Department of Infectious Diseases, Hacettepe University School of Medicine, 06230 Ankara, Turkey Differences between Patients with 10 Infectious Diseases Unit, Cruces University Hospital, 48903 Bilbao, Spain Hematological Malignancies and 11 Division of Infectious Diseases, University of Genoa (DISSAL) and Ospedale Policlinico San Martino, Solid Tumors. Pathogens 2022, 11, 16132 Genoa, Italy 12 Infectious Diseases Department, Ramon y Cajal Hospital, 28034 Madrid, Spain 1132. https://doi.org/10.3390/ 13 Infectious Diseases Section, Department of Medicine, Centro de Educación Médica e Investigaciones pathogens11101132 Clínicas (CEMIC), Buenos Aires C1430EFA, Argentina Academic Editors: Natalia Kirienko 14 Infectious Diseases Department, Parc Taulí University Hospital, 08208 Sabadell, Spain 15 Oncohematology Department, Comenius University and National Cancer Institute, 81499 Bratislava, Slovakia and Carolyn Cannon 16 Infectious Diseases Department, Hospital Erasto Gaertner, Curitiba 81520-060, Brazil Received: 21 July 2022 17 Infectious Diseases Department, Department of Medicine, Lausanne University Hospital, (CHUV), Accepted: 23 September 2022 1011 Lausanne, Switzerland 18 Hematology Department, Reina Sofía University Hospital-IMIBIC-UCO, Córdoba 14004, Argentina Published: 30 September 2022 19 Department of Infectious Diseases and Clinical Microbiology, Istanbul Education and Research Hospital, Publisher’s Note: MDPI stays neutral 34668 Istanbul, Turkey with regard to jurisdictional claims in 20 Division of Infectious Diseases, Department of Medicine II, University of Freiburg Medical Center and published maps and institutional affil- Faculty of Medicine, 79106 Freiburg, Germany 21 Unit of Infectious Diseases and Clinical Microbiology, Virgen Macarena University Hospital, Institute of iations. Biomedicine of Seville (IBIS), 41013 Seville, Spain 22 Infectious Diseases Unit, Instituto de Investigación Hospital “12 de Octubre” (i+12), “12 de Octubre”, University Hospital, School of Medicine, Universidad Complutense, 28041 Madrid, Spain 23 Infectious Diseases Service, Hospital del Mar, Infectious Pathology and Antimicrobials Research Copyright: © 2022 by the authors. Group (IPAR), Institut Hospital del Mar d’Investigations Mèdiques (IMIM), Universitat Autònoma de Licensee MDPI, Basel, Switzerland. Barcelona (UAB), CEXS-Universitat Pompeu Fabra, 08003 Barcelona, Spain This article is an open access article 24 Infectious Diseases Division, American University of Beirut Medical Center, Beirut 1107 2020, Lebanon distributed under the terms and 25 Faculty of Medicine, Ege University, 35040 Izmir, Turkey conditions of the Creative Commons 26 University of Health Science Izmir Bozyaka Training and Research Hospital, 35170 Izmir, Turkey Attribution (CC BY) license (https:// 27 Infectious Diseases Department, Hospital Regional de Málaga, 29010 Málaga, Spain 28 Infectious Diseases and Clinical Microbiology Department, Clínica Maraya, Pereira, Colombia. Critical Care creativecommons.org/licenses/by/ 4.0/). and Clinical Microbiology Department, Manizales 170001-17, Colombia Pathogens 2022, 11, 1132. https://doi.org/10.3390/pathogens11101132 https://www.mdpi.com/journal/pathogens Pathogens 2022, 11, 1132 2 of 12 29 Hospital Federal dos Servidores do Estado, and Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Ministério da Saúde, Rio de Janeiro 20221-161, Brazil 30 Department of Hematology, Oncology and Palliative Care, Klinikum Ernst von Bergmann, Academic Teaching Hospital, Charité University Medical School, 10117 Berlin, Germany 31 Instituto de Ciencias e Innovación en Medicina, Facultad de Medicina Clínica Alemana Universidad del Desarrollo, Santiago de Chile 12461, Chile, and Millennium Initiative for Collaborative Research on Bacterial Resistance (MICROB-R) 32 Infectious Diseases Clinic, Department of Medicine, University of Udine and Azienda Sanitaria Universitaria Integrata in Udine, and Infectious and Tropical Diseases Unit, Department of Medicine and Surgery, University of Insubria-ASST-Sette Laghi, 33100 Udine, Italy 33 Infectious Diseases and Microbiology Unit, Navarra University Clinic, 31008 Pamplona, Spain 34 Hematology Department, Marqués de Valdecilla University Hospital, 39008 Santander, Spain 35 Microbiology Department, University Hospitals Plymouth NHS Trust, Plymouth PL6 8DH, UK 36 Infectious Diseases, Hospital Rawson, San Juan J5400, Argentina 37 Hematology Department, Son Espases University Hospital, 07120 Palma de Mallorca, Spain 38 University of Barcelona, 08007 Barcelona, Spain 39 Centro de Investigación Biomédica en Red de Enfermedades Infecciosas (CIBERINFEC), Instituto de Salud Carlos III, 28029 Madrid, Spain * Correspondence: cgudiol@iconcologia.net; Tel.: +34-932607625; Fax: +34-932607637 † Membership of the IRONIC Study Group is provided in the Appendix A. Abstract: Objectives: To assess the clinical features and outcomes of Pseudomonas aeruginosa blood- stream infection (PA BSI) in neutropenic patients with hematological malignancies (HM) and with solid tumors (ST), and identify the risk factors for 30-day mortality. Methods: We performed a large multicenter, retrospective cohort study including onco-hematological neutropenic patients with PA BSI conducted across 34 centers in 12 countries (January 2006–May 2018). Episodes occurring in hematologic patients were compared to those developing in patients with ST. Risk factors associ- ated with 30-day mortality were investigated in both groups. Results: Of 1217 episodes of PA BSI, 917 occurred in patients with HM and 300 in patients with ST. Hematological patients had more commonly profound neutropenia (0.1 × 109 cells/mm) (67% vs. 44.6%; p < 0.001), and a high risk Multinational Association for Supportive Care in Cancer (MASCC) index score (32.2% vs. 26.7%; p = 0.05). Catheter-infection (10.7% vs. 4.7%; p = 0.001), mucositis (2.4% vs. 0.7%; p = 0.042), and perianal infection (3.6% vs. 0.3%; p = 0.001) predominated as BSI sources in the hematological pa- tients, whereas pneumonia (22.9% vs. 33.7%; p < 0.001) and other abdominal sites (2.8% vs. 6.3%; p = 0.006) were more common in patients with ST. Hematological patients had more frequent BSI due to multidrug-resistant P. aeruginosa (MDRPA) (23.2% vs. 7.7%; p < 0.001), and were more likely to receive inadequate initial antibiotic therapy (IEAT) (20.1% vs. 12%; p < 0.001). Patients with ST pre- sented more frequently with septic shock (45.8% vs. 30%; p < 0.001), and presented worse outcomes, with increased 7-day (38% vs. 24.2%; p < 0.001) and 30-day (49% vs. 37.3%; p < 0.001) case-fatality rates. Risk factors for 30-day mortality in hematologic patients were high risk MASCC index score, IEAT, pneumonia, infection due to MDRPA, and septic shock. Risk factors for 30-day mortality in patients with ST were high risk MASCC index score, IEAT, persistent BSI, and septic shock. Therapy with granulocyte colony-stimulating factor was associated with survival in both groups. Conclusions: The clinical features and outcomes of PA BSI in neutropenic cancer patients showed some differences depending on the underlying malignancy. Considering these differences and the risk factors for mortality may be useful to optimize their therapeutic management. Among the risk factors associated with overall mortality, IEAT and the administration of granulocyte colony-stimulating factor were the only modifiable variables. Keywords: Pseudomonas aeruginosa; bacteremia; bloodstream infection; cancer; solid tumor; hemato- logic malignancy Pathogens 2022, 11, 1132 3 of 12 1. Introduction Bloodstream infection (BSI) is a major cause of morbidity and mortality in neutropenic cancer patients. A shift in the etiology of BSI to Gram-negative bacilli (GNB) as well as an increase in antibiotic resistance among them have been reported in cancer patients in the last decades [1–4]. Pseudomonas aeruginosa (PA) has historically been one of the major causes of severe sepsis and high mortality in cancer patients with neutropenia [5–8]. Thus, the emergence of antimicrobial resistance in PA is of special concern, since initial inadequate empirical antibiotic therapy (IEAT) is associated with increased mortality in this setting [9–12]. We recently published the results of a large international cohort study (the IRONIC study) in which we found a significant increase in BSI due to multidrug-resistant PA (MDRPA) in neutropenic cancer patients throughout the study period (2006–2018) [13]. In this study, we provided a predictive model for multidrug resistance that can be easily calcu- lated using a web-based calculator (Risk of Multidrug resistance Pseudomonas aeruginosa Bloodstream Infection (MDR-PA BSI). Available online: http://ubidi.shinyapps.io/ironic, accessed on 20 July 2022) and allows for the identification of the patients who may benefit from the early administration of broad-spectrum antibiotic coverage against MDR strains according to the local susceptibility patterns. The cohort of patients consisted of patients with hematologic malignancies (HM) including hematopoietic stem cell transplant (HSCT) recipients, along with patients with solid tumors (ST). Patients with HM and with ST are often considered as a single group of patients when it comes to providing recommenda- tions on the management of febrile neutropenia [14,15]. Nevertheless, these two groups of patients present significant differences in the etiology, clinical presentation, and outcomes of BSI during neutropenia [16]. In fact, the risk factors associated with mortality in patients with BSI also appear to be different, depending on the underlying malignant condition [17]. The available literature on Pseudomonas aeruginosa bloodstream infection (PA BSI) usually focuses on hematologic patients [6–8,11,18], and there is no available information specifically on patients with ST, who indeed, appeared to be more susceptible to PA BSI than the hematologic patients in the above-mentioned study [13]. The knowledge of the potential differences between patients with HM and ST presenting with PA BSI could be useful in order to improve their management during febrile neutropenia. Thus, the aim of this study was to identify the differences in the clinical presentation, rates of multidrug resistance, source of infection, outcomes, and risk factors for the 30-day mortality of BSI due to PA in patients with HM compared to patients with ST, analyzing the large cohort of neutropenic patients with PA BSI (the IRONIC cohort). 2. Material and Methods 2.1. Study Design and Setting This study is part of the IRONIC project: a large multicenter, international, retrospec- tive cohort study conducted from 1 January 2006 to 31 May 2018 at 34 centers in 12 countries. The number of participating centers and the number of patients recruited at each one has previously been published (IRONIC) [13]. 2.2. Participants All adult (≥18 years) onco-hematological neutropenic patients including hematopoi- etic stem cell transplant (HSCT) recipients were eligible for the study if they were diagnosed with at least one episode of PA BSI during the study period. Subsequent episodes caused by PA occurring in the same patient were included in the study if they occurred at intervals of more than one month. The follow-up period was 30 days from BSI onset. 2.3. Variables Data regarding the baseline characteristics, clinical and microbiological features, and the endpoints were collected. Empirical antibiotic therapy was considered when the antibi- otic was administered before the reception of definitive susceptibility results. Adequate Pathogens 2022, 11, 1132 4 of 12 initial empirical antibiotic therapy was defined when patients received at least one in vitro active antibiotic against the PA strain. Initial IEAT was considered when the patient did not receive any empirical antibiotic with in vitro activity, or an empirical antibiotic therapy was lacking. The antipseudomonal β-lactams were uniformly administered at the current stan- dard doses for the treatment of febrile neutropenia [14,15]. In the case of renal impairment, the dosing was adjusted accordingly. 2.4. Outcomes Episodes of PA BSI occurring in HM patients were compared to those developing in patients with ST. Risk factors associated with 30-day mortality were investigated in both groups. 2.5. Microbiological Studies Clinical samples were processed at the microbiology laboratories of each participating center in accordance with the standard operating procedures. PA was identified using standard microbiological techniques at each center. In vitro susceptibility was determined according to the EUCAST recommendations [19], except at a center in Lebanon and at one center in Argentina, where the CLSI breakpoints were used, and at the center in the UK where the BSAC recommendations were used before 2016 [20]. PA isolate phenotypes were stratified in accordance with recent standard definitions; multidrug-resistant (MDR) was defined as acquired non-susceptibility to at least one agent in three or more antimicrobial categories; extensively drug-resistant (XDR) was defined as non-susceptibility to at least one agent in all but two or fewer antimicrobial categories, as previously described [21]. 2.6. Definitions Neutropenia and profound neutropenia were defined as an absolute neutrophil count below 0.5 × 109 cells/mm and 0.1 × 109 cells/mm, respectively [14]. The Multinational Association for Supportive Care in Cancer (MASCC) score was calculated as described elsewhere [22]. Previous corticosteroid treatment was defined as the administration of ≥20 mg of prednisone, or equivalent dosing, for at least four weeks within 30 days of BSI onset. Bacteremic PA pneumonia was defined as the presence of an acute respiratory illness and a new pulmonary infiltrate on a chest radiograph and/or chest tomography in association with concurrent PA BSI. Other BSI sources were established using standard U.S. Centers for Disease Control and Prevention criteria for secondary BSI [23]. In addition, the source of BSI was defined as unknown or endogenous in patients in whom no other sources were identified. Septic shock was defined as a systolic blood pressure <90 mmHg that was unresponsive to fluid treatment or required vasoactive drug therapy [24]. Mucositis was considered in patients with ulcerative lesions involving only the oral cavity. Comorbidities were defined as the presence of one or more of the following diseases: chronic obstructive pulmonary disease (COPD), chronic heart disease, chronic hepatic disease, diabetes mellitus, chronic renal disease, and cerebrovascular disease. Persistent BSI was considered if the blood cultures were positive after 48 h of adequate antibiotic therapy. The 7-day and 30-day case-fatality rates were defined as death from any cause within 7 days and 30 days of BSI onset, respectively. 2.7. Statistical Analysis To define the cohort characteristics, categorical variables were presented as the number of cases and percentages, while continuous variables were presented as the mean and standard deviation (SD) or median and interquartile range (IQR). Continuous variables were compared using the Student’s t-test or the Mann–Whitney U test where appropriate. Fisher’s exact test or Pearson’s χ2 test were applied to assess the relationship between categorical variables. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. A p value of <0.05 was considered statistically significant. The analysis was performed with Pathogens 2022, 11, 1132 5 of 12 the stepwise logistic-regression model of the SPSS software package version 19.0 (SPSS Inc., Chicago, IL, USA). 2.8. Ethics The study was approved by the Institutional Review Board at Bellvitge University Hospital (local reference number PR408/17) and by the local Research Ethics Committees at the participating centers. It was conducted in accordance with the guidelines of the Declaration of Helsinki. The need for informed consent was waived by the Clinical Research Ethics Committee due to the retrospective design. 3. Results 3.1. Clinical Characteristics Of the 1217 episodes of PA BSI, 917 occurred in patients with HM and 300 in patients with ST. In hematological patients, the most frequent malignancies were acute leukemia 312 (34%), non-Hodgkin lymphoma 271 (29.6%), and acute lymphoblastic leukemia 97 (10.6%), and among them, 289 (31.5%) received a hematopoietic stem cell transplant. The most common malignancies among patients with solid tumors were lung cancer 89 (29.7%), lower gastrointestinal cancer 30 (10%), urinary cancer 29 (9.7%), breast cancer 28 (9.3%) and head and neck cancer 26 (8.7%). Baseline characteristics of the patients included in the study are detailed in Table 1. Patients with HM were significantly younger, had more frequent profound neutropenia, a higher MASCC index score and severe mucositis. They also more often received previous biological therapies, corticosteroids, and antibiotics. Patients with ST were more likely to have comorbidities than patients with HM, especially COPD, and had received more frequent previous chemotherapy. Catheter-related infection, mucositis, and perineal infection were more common in patients with HM, whereas pneumonia and other abdominal sources were more frequent in ST patients. Table 1. The epidemiological and clinical characteristics of episodes of Pseudomonas aeruginosa bloodstream infection in patients with hematological malignancies and solid tumors. Overall Hematological Malignancies Solid Tumors Characteristics p-Value n = 1217 n = 917 (%) n = 300 (%) Age (years, median, range) 60 (IQR 20) 59 (IQR 21) 64 (IQR 17) <0.001 Male sex 751 559 (61.0) 192 (64.0) 0.192 Comorbidities 586 426 (48.4) 160 (57.1) 0.007 Chronic heart disease 149 120 (13.1) 29 (9.7) 0.069 Chronic obstructive pulmonary disease 100 54 (5.9) 46 (15.3) <0.001 Diabetes mellitus 86 60 (6.5) 26 (8.7) 0.144 Chronic liver disease 68 52 (5.7) 16 (5.3) 0.478 Other comorbidities * 183 140 (15.3) 43 (14.3) 0.386 High risk MASCC * index score 341 269 (32.2) 72 (26.7) 0.050 Profound neutropenia (0.1 × 109 cells/mm) 728 600 (67.0) 128 (44.6) <0.001 Previous chemotherapy (1 month) 1037 764 (83.6) 273 (91.3) <0.001 Previous biological therapies (3 months) 186 172 (19.2) 14 (4.8) <0.001 Pathogens 2022, 11, 1132 6 of 12 Table 1. Cont. Overall Hematological Malignancies Solid Tumors Characteristics p-Value n = 1217 n = 917 (%) n = 300 (%) Previous hospital admission (3 months) 744 574 (63.1) 170 (57.8) 0.062 Severe mucositis (grade III-IV) 169 142 (15.7) 27 (9.1) 0.002 Corticosteroid therapy (1 month) 832 727 (58.3) 105 (36.4) <0.001 Previous antibiotic therapy (1 month) 665 591 (65.4) 74 (25.3) <0.001 Prior quinolone prophylaxis 195 186 (20.5) 9 (3.0) <0.001 Intravenous vascular catheter 908 756 (82.5) 152 (50.7) <0.001 Urinary catheter 206 162 (18.1) 44 (15.1) 0.132 Nosocomial acquisition 694 620 (67.6) 74 (24.7) <0.001 Source of bloodstream infection Endogenous source 751 348 (37.9) 107 (35.7) 0.261 Pneumonia 586 210 (22.9) 101 (33.7) <0.001 Urinary tract 311 34 (3.7) 17 (5.7) 0.099 Catheter-related infection 112 98 (10.7) 14 (4.7) 0.001 Other abdominal * 112 26 (2.8) 19 (6.3) 0.006 Neutropenic enterocolitis 71 57 (6.2) 14 (4.7) 0.199 Mucositis 71 22 (2.4) 2 (0.7) 0.042 Skin and soft tissue infection 70 57 (6.2) 13 (4.3) 0.141 Unknown origin 70 13 (1.4) 2 (0.7) 0.244 Perineal infection 51 3 (3.6) 1 (0.3) 0.001 Septic shock at presentation 411 274 (30.0) 137 (45.8) <0.001 Septic metastases 88 78 (8.9) 10 (3.4) <0.001 Gangrenous ecthyma 51 50 (5.5) 1 (0.3) <0.001 * Other comorbidities included chronic renal disease and cerebrovascular disease. MASCC (Multinational Association for Supportive Care in Cancer). Other abdominal sources included cholangitis, peritonitis, and intraabdominal abscesses. 3.2. Etiology and Antibiotic Resistance Hematological patients frequently had more BSI due to MDRPA (23.2% vs. 7.7%; p < 0.001) and XDRPA (17.2% vs. 5.3%; p < 0.001). The rate of polymicrobial infection did not differ between groups (17.9% vs. 17.7%). 3.3. Empirical Antibiotic Therapy and Clinical Outcomes Empirical antibiotic therapy and clinical outcomes are described in Table 2. Patients with ST frequently received more monotherapy (73.6% vs. 57.5%; p < 0.001) whereas patients with HM were more likely to receive IEAT (20.1% vs. 12%; p < 0.001). Patients with ST presented more frequently with septic shock (45.8% vs. 30%; p < 0.001), and also presented worse outcomes, with increased 7-day (38% vs. 24.2%; p < 0.001) and 30-day (49% vs. 37.3%; p < 0.001) case-fatality rates. Pathogens 2022, 11, 1132 7 of 12 Table 2. The empirical antibiotic therapy and clinical outcomes of Pseudomonas aeruginosa bloodstream infection compared by groups. Hematological Malignancies Solid Tumors Characteristics p-Value n = 917 (%) n = 300 (%) Empirical Antibiotic Therapy Monotherapy 519 (57.5) 218 (73.6) 0.000 Combination therapy 383 (42.5) 78 (26.4) <0.001 β-lactam + aminoglycoside 209 (23.2) 51 (17.2) 0.031 β-lactam + non-aminoglycoside 55 (6.1) 17 (5.7) 0.821 Initial inadequate empirical antibiotic therapy 184 (20.1) 36 (12.0) <0.001 Carbapenems 89 10 Piperacillin-tazobactam 52 13 Glycopeptides 35 7 Aminoglycosides 18 1 Broad-spectrum cephalosporins 15 1 Quinolones 11 1 Other 42 17 Granulocyte colony-stimulating factor 490 (54) 136 (45.9) 0.009 Clinical Outcomes Intensive care unit admission 285 (31.1) 103 (34.3) 0.164 Invasive mechanical ventilation 187 (20.4) 59 (19.7) 0.422 Persistent bloodstream infection 111 (12.3) 23 (7.9) 0.024 Early case-fatality rate (7 days) 222 (24.2) 114 (38.0) <0.001 Overall case-fatality rate (30 days) 342 (37.3) 147 (49.0) <0.001 3.4. Risk Factors for Overall Case-Fatality Rate Risk factors for 30-day mortality are described in Tables 3 and 4. High risk MASCC index score, IEAT, pneumonia, infection due to MDRPA and septic shock were associated with 30-day case fatality rate in hematologic patients (Table 3). A high risk MASCC index score, IEAT, persistent BSI, and septic shock were associated with the 30-day case fatality rate in patients with ST (Table 4). Therapy with the granulocyte colony-stimulating factor was associated with survival in both groups. Table 3. The risk factors for the overall case-fatality rate in hematological patients by univariate and multivariate analysis. Adjusted OR Characteristics n p-Value (95% CI) Age 1.01 (0.99–1.02) 0.088 Male sex 559 (61.0) 0.74 (0.51–1.08) 0.126 High risk MASCC index score 269 (32.2) 2.53 (1.63–3.95) <0.001 Initial inadequate empirical antibiotic therapy 184 (20.1) 3.45 (1.09–10.92) <0.035 Persistent bloodstream infection 111 (12.3) 1.43 (0.83–2.47) 0.195 Granulocyte colony-stimulating factor 490 (54) 0.53 (0.36–0.76) 0.001 Pneumonia 210 (22.9) 2.23 (1.47–3.38) <0.001 MDRPA 157 (17.2) 2.22 (1.44–3.41) <0.001 Septic shock 274 (30.0) 7.12 (4.78–10.60) <0.001 MDRPA: Multidrug-resistant Pseudomonas aeruginosa. Pathogens 2022, 11, 1132 8 of 12 Table 4. The risk factors for the overall case-fatality rate in patients with solid tumors by univariate and multivariate analysis. Adjusted OR (95% Characteristics n p-Value CI) Age 1.01 (0.98–1.03) 0.329 Male sex 192 (64.0) 0.98 (0.52–1.83) 0.949 High risk MASCC index score 72 (26.7) 2.68 (1.21–5.94) 0.015 Inadequate initial empirical antibiotic therapy 36 (12.0) 2.84 (1.10–7.35) 0.031 Persistent bloodstream infection 23 (7.9) 9.92 (2.08–47.20) 0.004 Granulocyte colony-stimulating factor 136 (45.9) 0.26 (0.14–0.48) <0.001 Septic shock 137 (45.8) 3.97 (2.10–7.51) <0.001 3.5. Discussion This large, multicenter, international cohort study of high-risk neutropenic cancer patients identified several differences between hematological patients and those with solid tumors with PA BSI that can be useful to optimize their therapeutic management. Hemato- logical patients frequently had more profound neutropenia and BSI from an endogenous source and from the catheter, and were more likely to receive IEAT due to higher rates of multidrug resistance among the PA isolates. Conversely, patients with solid tumors frequently had more COPD and pneumonia, and presented poorer outcomes, with higher rates of septic shock at presentation and higher case-fatality rates. Of note, pneumonia was the second cause of PA BSI in both groups of patients, but it was significantly more frequent in patients with solid tumors. This is probably due to the fact that the latter group of patients often had COPD as a relevant comorbidity and lung cancer as the underlying disease. The presence of dysfunctional malignant cells in the lung tissue predisposes to invasive disease in these patients, who are often colonized by Pseudomonas aeruginosa [25]. In contrast, PA BSI in hematological patients was mainly associated with the administration of myeloablative chemotherapy and its consequences such as the presence of profound neutropenia and mucositis and the infection of long-term central venous catheters. Even though Gram-positives still remain the leading cause of catheter-related BSI, an increase in Gram-negatives has been described in the last decades [26–28]. An important finding of our study is that hematological patients frequently had more infections due to MDRPA and XDRPA and were more likely to receive IEAT. This is probably a consequence of the increased rates of previous antibiotic exposure in this group of patients as well as the use of quinolone prophylaxis [1,29,30]. Even though the reduction of antibiotic consumption is one of the major cornerstones in the fight against antibacterial resistance, this strategy may be difficult to accomplish in these high-risk patients. Nevertheless, in light of numerous studies that have identified the use of quinolone prophylaxis as a major risk factor for multidrug resistance, the universal use of this preventive strategy is no longer recommended, particularly when the rates of quinolone resistance among Gram-negatives are high in some centers [13,31,32]. Importantly, carbapenems and piperacillin-tazobactam were the most common in- adequate empirical agents used in both groups. This finding is of special concern in the current era of widespread antimicrobial resistance and emerging resistance to carbapenems. Thus, the administration of combined empirical therapy and the prompt use of the recently available antibiotics in febrile cancer patients should be seriously considered [33–37]. As observed in other series of hematological patients with PA BSI, the early and overall case-fatality rates of the whole cohort were high [6,8–12]. Of note, outcomes were better in patients with hematological malignancies in spite of more frequently presenting persistent BSI and receiving IEAT more often. One plausible explanation is that solid tumor patients Pathogens 2022, 11, 1132 9 of 12 were older, with more comorbidities, more frequent advanced neoplasm, more septic shock at presentation, and pneumonia as the source of BSI. Finally, a high MASCC index score, septic shock, and IEAT were all identified as risk factors for 30-day case fatality rates in both groups, whereas receiving therapy with granulocyte colony-stimulating factor (G-CSF) was associated with improved survival. It is noteworthy that the improvement in the empirical treatment and the administration of G-CSF were the only modifiable factors associated with mortality in our study. The main strength of this study is that it is based on one of the largest cohorts of neutropenic cancer patients with PA BSI, with a multicenter international design that allows for generalization of the results. Nevertheless, this study also has some limitations that should be acknowledged. First, this is a retrospective study, so the main limitation of the data is related to the potential effects of unmeasured variables and residual confounding. Second, this was not a randomized clinical trial; thus, the choice of therapy may have been influenced by patient-related variables and by the clinical presentation. Finally, it was a relatively long period, and it is not possible to rule out a certain calendar effect in some variables such as mortality. In conclusion, we identified significant differences between patients with hematologi- cal malignancies and solid tumors with PA BSI that should be considered when approaching cancer patients with suspected PA infection. Among the risk factors associated with overall mortality, IEAT and the administration of G-CSF were the only modifiable variables. Author Contributions: Conceptualization, C.G.; methodology, C.R.-C., C.G.; software, J.C.; valida- tion, C.R.-C., J.L.-A., M.P. (Marta Peña), I.R.-C., P.P.-A., E.A., C.O., M.A., M.M. (Miguel Montejo), M.M. (Malgorzata Mikulska), P.M.-D., F.H., O.G., L.D., H.M.P.M., A.-S.B., E.G., B.I., W.V.K., Z.R.P.-B., G.M.d.l.C., M.M.M., S.S.K., O.R.S., S.C., I.M.-G., J.I.M., M.Z.R.G., P.H., R.A., M.P. (Marta Peña), J.L.d.P., L.Y., R.T., A.M., A.N., J.C., C.G.; formal analysis, C.R.-C., C.G.; investigation, C.R.-C., C.G.; resources, C.G.; data curation, C.R.-C., J.L.-A., M.P. (Marta Peña), I.R.-C., P.P.-A., E.A., C.O., M.A., M.M. (Miguel Montejo), M.M. (Malgorzata Mikulska), P.M.-D., F.H., O.G., L.D., H.M.P.M., A.-S.B., E.G., B.I., W.V.K., Z.R.P.-B., G.M.d.l.C., M.M.M., S.S.K., O.R.S., S.C., I.M.-G., J.I.M., M.Z.R.G., P.H., R.A., M.P. (Maddalena Peghin), J.L.d.P., L.Y., R.T., A.M., A.N., J.C., C.G.; writing—original draft preparation, C.R.-C.; writing—review and editing, C.G.; visualization, C.R.-C., J.L.-A., M.P. (Marta Peña), I.R.-C., P.P.-A., E.A., C.O., M.A., M.M. (Miguel Montejo), M.M. (Malgorzata Mikulska), P.M.-D., F.H., O.G., L.D., H.M.P.M., A.-S.B., E.G., B.I., W.V.K., Z.R.P.-B., G.M.d.l.C., M.M.M., S.S.K., O.R.S., S.C., I.M.-G., J.I.M., M.Z.R.G., P.H., R.A., M.P. (Maddalena Peghin), J.L.d.P., L.Y., R.T., A.M., A.N., J.C., C.G.; supervisión, C.G.; project administration, C.G.; funding acquisition, C.G., J.C. All authors have read and agreed to the published version of the manuscript. Funding: This study was supported by the Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Economía, Industria y Compet- itividad, Centro de Investigación Biomédica en Red de Enfermedades Infecciosas (CIBERINFEC) (CB21/13/00009; CB21/13/00079; CB21/13/00054; CB21/13/00086), Madrid, Spain. Institutional Review Board Statement: The study was approved by the Institutional Review Board at Bellvitge University Hospital (local reference number PR408/17) and by the local Research Ethics Committees at the participating centers. It was conducted in accordance with the guidelines of the Declaration of Helsinki. Informed Consent Statement: The need for informed consent was waived by the Clinical Research Ethics Committee due to the retrospective design of the study. Data Availability Statement: The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request. Acknowledgments: We thank the ESCMID Study Group for Bloodstream Infections, Endocarditis, and Sepsis (ESGBIES) and the ESCMID Study Group for Immunocompromised Hosts (ESGICH) for supporting the study. We thank the Centres de Recerca de Catalunya (CERCA) Program and Generalitat de Catalunya for the institutional support. We thank the Spanish Network for Research in Infectious Diseases and the Río Hortega program of the Instituto de Salud Carlos III for the financial support of pre-doctoral student J. Laporte-Amargós and A. Bergas. Pathogens 2022, 11, 1132 10 of 12 Conflicts of Interest: FH received speaker’s fees from Merck and Pfizer and research and educational grants from Pfizer. SSK receives honoraria from Pfizer, Merck, Gilead, and Menarini for speaker bureau and advisory boards. CG received speaker’s fees from MSD, Pfizer, and Gilead and research and grants from Pfizer and Merck. All the other authors declare no conflict of interests. Appendix A Ironic Study Investigators: Alba Bergas and Enric Sastre, Infectious Diseases De- partment, Bellvitge University Hospital, IDIBELL, Barcelona, Spain. Marisol Rodríguez Arias, Oncology Department, Institut Català d’Oncologia (ICO)—Hospital Duran i Reynals, IDIBELL, Barcelona, Spain. Juan Aguilar-Company, Oncology Department, and Nieves Larrosa, Microbiology Department, Vall d’Hebron University Hospital, Barcelona, Spain. Celia Cardozo and Carolina Garcia-Vidal, Infectious Diseases Department, Hospital Clínic i Provincial, Barcelona, Spain. Ibrahim Karim-Yaqub, Instituto do Câncer do Estado de São Paulo da Faculdade de Medicina da Universidade de São Paulo, Brazil. Raffaella Greco, Hematology and Bone Marrow Transplantation Unit, and Paola Cichero, Microbiology and Virology Laboratory, IRCCS San Raffaele Scientific Institute, Milan, Italy. Caglayan Merve Ayaz, Infectious Diseases Department, Hacettepe University School of Medicine, Ankara, Turkey. Roberto Céspedes, Hematology Department, and Leire López-Soria, Microbiol- ogy Department, Cruces University Hospital, Bilbao, Spain. Laura Magnasco, Division of Infectious Diseases, University of Genoa (DISSAL) and Ospedale Policlinico San Mar- tino, Genoa, Italy. Jesús Fortún, Infectious Diseases Department, Ramón y Cajal Hospital, Madrid, Spain. Diego Torres, Infectious Diseases Section, Department of Medicine, Centro de Educación Médica e Investigaciones Clínicas (CEMIC), Buenos Aires, Argentina. Anna Boté, Infectious Diseases Department, and Mateu Espasa, Microbiology Department, Parc Taulí University Hospital, Sabadell, Barcelona, Spain. Mia Hold Montaguti, Infectious Diseases Department, Hospital Erasto Gaertner, Curitiba, Brazil. Pierre-Yves Bochud, Infec- tious Diseases Department, Lausanne University Hospital (CHUV), Lausanne, Switzerland. Salvador Tabares Carrasco and Josefina Serrano López, Hematology Department, Reina Sofía University Hospital-IMIBIC-UCO, Córdoba. Hartmut Bertz, Hematology-Oncology Department, and Siegbert Rieg, Division of Infectious Diseases, Department of Medicine II, University of Freiburg Medical Center and Faculty of Medicine, Freiburg, Germany. Marina de Cueto, Clinical Unit of Infectious Diseases, Microbiology and Preventive Medicine, Uni- versity Hospitals Virgen Macarena and Virgen del Rocío—IBiS; Departament of Medicine, University of Seville, Seville, Spain. José María Aguado, Infectious Diseases Unit, 12 de Octubre University Hospital, Madrid Spain. Juan Pablo Horcajada, Infectious Diseases Service, Hospital del Mar, Infectious Pathology and Antimicrobials Research Group (IPAR), Institut Hospital del Mar d’Investigations Mèdiques (IMIM), Universitat Autònoma de Barcelona (UAB), CEXS-Universitat Pompeu Fabra, Barcelona, Spain. Saeed El Zein and Jean-Francois Jabbour, Infectious Diseases Division, American University of Beirut Medical Center, Beirut, Lebanon. Ayse Uyan-Onal Department of Infectious Diseases and Clinical Microbiology, Ege University Faculty of Medicine, Izmir Turkey. Arzu Nazli-Zeka Depart- ment of Infectious Diseases and Clinical Microbiology, Dokuz Eylul University Faculty of Medicine, Izmir Turkey. Begoña Palop, Microbiology Department, Hospital Regional de Málaga, Málaga, Spain. Lina Clemencia Correa, Clinica Maraya, Pereira, Colombia. Amanda Aparecida da Silva Machado and Vitória Pinson Ruggi Dutra, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil. Georg Maschmeyer, Department of Hematology, Oncology and Palliative Care, Klinikum Ernst von Bergmann, Academic Teaching Hospital of Charité University Medical School, Berlin, Germany. Jose Munita, Instituto de Ciencias e Innovación en Medicina, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago de Chile, Chile, and Millennium Initiative for Collab- orative Research on Bacterial Resistance (MICROB-R). 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