Global impact of antibacterial resistance in patients with hematologic malignancies and hematopoietic cell transplant recipients.

Patients with hematologic malignancies and hematopoietic cell transplant (HCT) recipients are at high risk of developing bacterial infections. These patients may suffer severe consequences from these infections if they do not receive immediate effective therapies, and thus are uniquely threatened by antimicrobial-resistant bacteria. Here, we outline how the emergence of specific resistant bacteria threatens the effectiveness of established approaches to prevent and treat infections in this population. The emergence of fluoroquinolone resistance among Enterobacterales and viridans group streptococci may decrease the effectiveness of fluoroquinolone prophylaxis during neutropenia. The emergence of Enterobacterales that produce extended-spectrum ß-lactamases or carbapenemases and of increasingly resistant Pseudomonas aeruginosa may result in neutropenic patients experiencing delayed time to active antibacterial therapy, and consequently worse clinical outcomes. The ability to select targeted antibacterial therapies after the availability of susceptibility data may be limited in patients infected with metallo-ß-lactamase-producing Enterobacterales and difficult-to-treat P. aeruginosa. Vancomycin-resistant enterococci and Stenotrophomonas maltophilia can cause breakthrough infections in patients already being treated with broad-spectrum ß-lactam antibiotics. Resistance can also limit the ability to provide oral stepdown antibacterial therapy for patients who could otherwise be discharged from hospitalization. We also outline strategies that have the potential to mitigate the negative impact of antimicrobial resistance, including interventions based on active screening for colonization with resistant bacteria and the use of novel rapid diagnostic assays. Additional research is needed to better understand how these strategies can be leveraged to combat the emerging crisis of antimicrobial resistance in patients with hematologic malignancies and HCT recipients.

Impact of a Multiplex Polymerase Chain Reaction Panel on Duration of Empiric Antibiotic Therapy in Suspected Bacterial Meningitis.

BACKGROUND: Multiplex polymerase chain reaction (PCR) panels allow for rapid detection or exclusion of pathogens causing meningitis and encephalitis (ME). The clinical impact of rapid multiplex PCR ME panel results on the duration of empiric antibiotic therapy is not well characterized. METHODS: We performed a retrospective prepost study at our institution that evaluated the clinical impact of a multiplex PCR ME panel among adults with suspected bacterial meningitis who received empiric antibiotic therapy and underwent lumbar puncture in the emergency department. The primary outcome was the duration of empiric antibiotic therapy. RESULTS: The positive pathogen detection rates were similar between pre- and post-multiplex PCR ME panel periods (17.5%, 24 of 137 vs 20.3%, 14 of 69, respectively). The median duration of empiric antibiotic therapy was significantly reduced in the post-multiplex PCR ME panel period compared with the pre-multiplex PCR ME panel period (34.7 vs 12.3 hours, P = .01). At any point in time, 46% more patients in the post-multiplex PCR ME panel period had empiric antibiotic therapy discontinued or de-escalated compared with the pre-multiplex PCR ME panel period (sex- and immunosuppressant use-adjusted hazard ratio 1.46, P = .01). The median hospital length of stay was shorter in the post-multiplex PCR ME panel period (3 vs 4 days, P = .03). CONCLUSIONS: The implementation of the multiplex PCR ME panel for bacterial meningitis reduced the duration of empiric antibiotic therapy and possibly hospital length of stay compared with traditional microbiological testing methods.

Rates of ERBB2 Alterations across Melanoma Subtypes and a Complete Response to Trastuzumab Emtansine in an ERBB2-Amplified Acral Melanoma.

PURPOSE: Patients with BRAF V600 wild-type melanoma whose tumors progress on checkpoint inhibition currently have limited therapeutic options, and additional rational treatment targets are needed. ERBB2 alterations may be amenable to targeted inhibition, but the rate of ERBB2 alterations across melanoma subtypes is not well described. PATIENTS AND METHODS: All patients with nonuveal melanoma (cutaneous, acral, mucosal, and unknown primary) whose tumors underwent multigene sequencing with MSK-IMPACT at Memorial Sloan Kettering Cancer Center (New York, NY) from 2014 to 2018 were reviewed for known or likely oncogenic somatic alterations in ERBB2 and the other known canonical driver genes BRAF, NRAS, KIT, NF1, GNAQ, and GNA11. RESULTS: A patient with acral melanoma resistant to checkpoint inhibition was found to have ERBB2 amplification and achieved a durable complete response to trastuzumab emtansine. Tumor sequencing results from 732 melanoma cases were analyzed for ERBB2 and canonical driver gene alterations. ERBB2 amplifications were detected in acral (3%) and mucosal (3%) melanomas. ERBB2 mutations were found in cutaneous (1%), acral (2%), and mucosal (2%) subtypes and frequently cooccurred with NF1 alterations. Among the 140 patients whose tumors lacked canonical driver alterations, ERBB2 amplifications were detected in acral (7%) and mucosal (6%) melanomas. CONCLUSIONS: ERBB2 amplification is present in a minority of acral lentiginous and mucosal melanomas. Activating mutations in ERBB2 were identified in nonuveal melanoma subtypes and are frequently comutated with canonical drivers. HER2 could represent a therapeutically relevant target across melanoma subtypes.