Multiplicity of blaKPC Genes and pKpQIL Plasmid Plasticity in the Development of Ceftazidime-Avibactam and Meropenem Coresistance in Klebsiella pneumoniae Sequence Type 307.

In 2021, Klebsiella pneumoniae sequence type 307 (ST307) strains causing pulmonary and bloodstream infections identified in a hospital in Rome, Italy, reached high levels of resistance to ceftazidime-avibactam (CZA). One of these strains reached high levels of resistance to both CZA and carbapenems and carried two copies of blaKPC-3 and one copy of blaKPC-31 located on plasmid pKpQIL. The genomes and plasmids of CZA-resistant ST307 strains were analyzed to identify the molecular mechanisms leading to the evolution of resistance and compared with ST307 genomes at local and global levels. A complex pattern of multiple plasmids in rearranged configurations, coresident within the CZA-carbapenem-resistant K. pneumoniae strain, was observed. Characterization of these plasmids revealed recombination and segregation events explaining why K. pneumoniae isolates from the same patient had different antibiotic resistance profiles. This study illustrates the intense genetic plasticity occurring in ST307, one of the most worldwide-diffused K. pneumoniae high-risk clones.

Benefits and Safety of Empiric Antibiotic Treatment Active Against KPC-K. pneumoniae in Febrile Neutropenic Patients with Acute Leukemia Who are Colonized with KPC-K. pneumoniae. A 7-Years Retrospective Observational Cohort Study.

Purpose: To evaluate the benefits and safety of the empiric antibiotic treatment (EAT) active against KPC-K. pneumoniae in febrile neutropenic patients with acute leukaemia (AL) who are colonised by KPC-K. pneumoniae. Patients and Methods: A 7-year (2013-2019) retrospective observational cohort study was conducted at the Haematology, Sapienza Rome University (Italy) on 94 febrile neutropenia episodes (FNE) in AL patients KPC-K. pneumoniae carriers treated with active EAT. Results: Eighty-two (87%) FNE were empirically treated with antibiotic combinations [38 colistin-based and 44 ceftazidime-avibactam (CAZAVI)-based], 12 with CAZAVI monotherapy. Successful outcomes were observed in 88/94 (94%) FNE, 46/49 (94%) microbiologically documented infections, and 24/27 (89%) gram-negative bloodstream infections (GNB-BSI). Mortality due to infective causes was 4.2% (2.1% within 1 week). KPC-K. pneumoniae infections caused 28/94 FNE (30%) and KPC-K. pneumoniae-BSI was documented in 22 FNE (23.4%) (85% of GNB-BSI), in all cases patients received active EAT, and 21 survived. KPC-K.pneumoniae-BSI mortality rate was 4.5%. CAZAVI-based EAT showed better results than colistin-based EAT (55/56 vs 33/38, p = 0.037), overall and without EAT modification (41/56 vs 20/38, p = 0.02). Empirical combinations including CAZAVI were successful in 98% of cases (43/44 vs 33/38 for colistin-based EAT, p = 0.01), without modifications in 82% (36/44 vs 20/28, p = 0.02). All deaths occurred in patients treated with colistin-based EAT (4/38 vs 0/56, p = 0.02). CAZAVI-containing EAT was the only independent factor for an overall successful response (HR 0.058, CI 0.013-1.072, p = 0.058). Nephrotoxicity occurred in 3(8%) patients undergoing colistin-based EAT (none in those undergoing CAZAVI-based EAT, p = 0.02). Conclusion: KPC-K. pneumoniae infections are frequent in colonised AL patients with FNE. EAT with active antibiotics, mainly CAZAVI-based combinations, was effective, safe, and associated with low overall and KPC-K. pneumoniae-BSI-related mortality.

Reduced mortality from KPC-K.pneumoniae bloodstream infection in high-risk patients with hematological malignancies colonized by KPC-K.pneumoniae.

BACKGROUND: KPC-K.pneumoniae bloodstream infection (KPC-KpBSI) mortality rate in patients with hematological malignancies is reported about 60%. The initial treatment active against KPC-K.pneumoniae is crucial for survival and KPC-K.pneumoniae rectal colonization usually precedes KPC-KpBSI. We evaluated the impact on KPC-KpBSI mortality of the preemptive use of antibiotics active against KPC-K.pneumoniae, as opposed to inactive or standard empiric antibiotics, for the empiric treatment of febrile neutropenia episodes in patients with hematological malignancy identified as KPC-K.pneumoniae intestinal carriers. METHODS: We compared the outcomes of KPC-KpBSIs occurring in high-risk hematological patients known to be colonized with KPC-K.pneumoniae, during two time periods: March2012-December2013 (Period 1, initial approach to KPC-K.pneumoniae spread) and January2017-October2018 (Period 2, full application of the preemptive strategy). The relative importance of the various prognostic factors that could influence death rates were assessed by forward stepwise logistic regression models. RESULTS: KPC-KpBSI-related mortality in hematological patients identified as KPC-K.pneumoniae carriers dropped from 50% in Period 1 to 6% in Period 2 (p < 0.01), from 58 to 9% in acute myeloid leukemia carriers(p < 0.01). KPC-KpBSIs developed in patients identified as KPC-K.pneumoniae carriers were initially treated with active therapy in 56% and 100% of cases in Period 1 and Period 2, respectively (p < 0.01), in particular with an active antibiotic combination in 39 and 94% of cases, respectively(p < 0.01). The 61% of KPC-KpBSI observed in Period 1 developed during inactive systemic antibiotic treatment (none in Period 2, p < 0.01), fatal in the 73% of cases. Overall, KPC-KpBSI-related mortality was 88% with no initial active treatment, 11.5% with at least one initial active antibiotic (p < 0.01), 9% with initial active combination. Only the initial active treatment resulted independently associated with survival. CONCLUSIONS: In high-risk hematological patients colonized by KPC-K.pneumoniae, the empiric treatment of febrile neutropenia active against KPC-K.pneumoniae reduced KPC-KpBSI-related mortality to 6% and prevented fatal KPC-KpBSI occurrence during inactive systemic antibiotic treatment.

Carbapenem-resistant Klebsiella pneumoniae in high-risk haematological patients: factors favouring spread, risk factors and outcome of carbapenem-resistant Klebsiella pneumoniae bacteremias.

BACKGROUND: Carbapenem-resistant Klebsiella pneumoniae (CRKP) spread and infections in patients with haematological malignancies are a serious concern especially in endemic areas. Treatment failures and delay in appropriate therapy for CRKP infections are frequent and the mortality rate associated with CRKP bacteremia in neutropenic haematological patients is reported about 60%. METHODS: Haematological patients harboring CRKP hospitalized between February 2012 and May 2013 in an Italian Teaching hospital were examined. Conditions favouring CRKP spread in a haematological unit, risk factors for bacteremia in CRKP-carriers and for CRKP bacteremia-related death were evaluated in this observational retrospective study. RESULTS: CRKP was isolated in 22 patients, 14 (64%) had bacteremia. Control measures implementation, particularly the weekly rectal screening for CRKP performed in all hospitalized patients and contact precautions for CRKP-carriers and newly admitted patients until proved CRKP-negative, reduced significantly the CRKP spread (14 new carriers identified of 131 screened patients vs 5 of 242 after the intervention, p = 0.001). Fifty-eight percent of carriers developed CRKP bacteremia, and acute myeloid leukemia (AML) resulted independently associated with the bacteremia occurrence (p = 0.02). CRKP bacteremias developed mainly during neutropenia (86%) and in CRKP-carriers (79%). CRKP bacteremias were breakthrough in 10 cases (71%). Ten of 14 patient with CRKP bacteremias died (71%) and all had AML. The 70% of fatal bacteremias occurred in patients not yet recognized as CRKP-carriers and 80% were breakthrough. Initial adequate antibiotic therapy resulted the only independent factor able to protect against death (p = 0.02). CONCLUSIONS: The identification of CRKP-carriers is confirmed critical to prevent CRKP spread. AML patients colonized by CRKP resulted at high risk of CRKP-bacteremia and poor outcome and the adequacy of the initial antibiotic therapy may be effective to improve survival. To limit the increase of resistance, the extensive use of antibiotics active against CRKP should be avoided, but in the setting of high CRKP pressure and high-risk CRKP-colonized haematological patients, timely empiric antibiotic combinations active against CRKP could be suggested as treatment of febrile neutropenia.

Cytomegalovirus in bone marrow cells correlates with cytomegalovirus in peripheral blood leukocytes.

In allogeneic hematopoietic stem cell transplant recipients with bone marrow (BM) suppression, cytomegalovirus (CMV) pp65 antigenemia and DNA were detectable in peripheral blood leukocytes (PBL) and BM cells. A relationship between CMV infection of PBL and BM cells has been found.

In vitro activities of amphotericin B and AmBisome against Aspergillus isolates recovered from Italian patients treated for haematological malignancies.

Although there is evidence that liposomal amphotericin B (AmBisome) is non-inferior to amphotericin B (AmB) in terms of in vivo efficacy, in vitro data regarding the activity of AmBisome against clinical isolates of Aspergillus are rare. In this study, the susceptibilities to AmB and AmBisome of 103 Aspergillus complex isolates (48 Aspergillus flavus, 33 Aspergillus fumigatus, 13 Aspergillus terreus and 9 Aspergillus niger) recovered from haematological patients with invasive infection were compared. Minimum inhibitory concentrations (MICs) were determined by the broth microdilution (BMD) method according to the Clinical and Laboratory Standards Institute (CLSI), whilst AmB susceptibility was also determined by Etest. Using a susceptible/resistant MIC cut-off of 1mg/L, all A. fumigatus and A. niger complexes isolates were susceptible to both AmB and AmBisome. In contrast, 38.5% and 30.8% of the A. terreus complex isolates were resistant to AmB and AmBisome, respectively, with good agreement between BMD and Etest methods. With respect to A. flavus complex isolates, 43.7% and 16.7% were resistant by the BMD method to AmBisome and AmB, respectively. For isolates with discrepant results, AmB MICs obtained by Etest were higher than those obtained for AmB by the BMD method and they were closer to those obtained for AmBisome by BMD. Aspergillus flavus AmB MICs ranged from 0.5 mg/L to 2 mg/L by the BMD method and from 1 mg/L to >16 mg/L by the Etest method, and AmBisome MICs ranged from 0.06 mg/L to >16 mg/L by the BMD method. Etest appears to be superior to the CLSI BMD method using AmB in detecting AmB resistance of Aspergillus spp., although the CLSI BMD method might be a suitable procedure if AmBisome is used as the test drug.

Clinically driven diagnostic antifungal approach in neutropenic patients: a prospective feasibility study.

PURPOSE: Preemptive strategies in neutropenic patients based on serum galactomannan (GM) -guided triggering of diagnostic work-up may be time-consuming and expensive when applied to the entire population. We have assessed the feasibility of a clinically driven diagnostic strategy without GM screening. PATIENTS AND METHODS: Patients with neutropenic fever underwent a baseline diagnostic work-up (BDWU; three blood cultures and other examinations as indicated). An intensive diagnostic work-up (IDWU; GM for 3 days, chest computed tomography and other examinations as indicated) was reserved for patients with 4 days of persisting or relapsing fever or with other clinical findings possibly related to an invasive fungal diseaser (IFD). Antifungal therapy was administered to patients diagnosed with IFD and empirically (negative IDWU) only to those with persisting neutropenic fever and worsening clinical conditions. RESULTS: Of 220 neutropenia episodes, fever occurred in 159 cases and recurred in 28 cases. Overall, 49 IFDs were diagnosed (two by BDWU and 47 by IDWU) during 48 episodes (21.8%). Diagnostic-driven therapy was administered to 48 patients with IFDs; one patient with zygomycosis died without treatment. Only one patient received empirical therapy. IDWU was required in 40% of neutropenia episodes, and only 1.4 mean blood samples per neutropenia episode were tested for GM. Our strategy allowed a 43% reduction in antifungal treatments compared with a standard empirical approach. At 3-month follow-up, 63% of patients with IFD survived, and no undetected IFDs were found. CONCLUSION: A clinically driven diagnostic approach in selected neutropenia episodes offered effective antifungal control and reduced the exposure to unnecessary antifungal treatment.