Elimination of ALX148 Interference in Pretransfusion Testing by RBC Alloadsorption: Two Case Reports / 대한수혈학회지

The anti-CD47 monoclonal antibody, one of the immune checkpoint inhibitors, can interfere with pretransfusion testing by binding to the cluster of differentiation 47 (CD47) proteins expressed on the surface of red blood cells (RBCs). We report the experience of mitigating interference in the pretransfusion test in two patients treated with ALX148, an anti-CD47 monoclonal antibody, by using multiple RBC alloadsorption. Two patients with a history of advanced head and neck squamous cell carcinoma were referred for a pretransfusion and cross-matching test. The blood group type of the two patients was B, RhD＋, but antibody screening, autocontrol, direct globulin, and cross-matching of the RBC units showed high-intensity agglutination. Medical records revealed that the patients were enrolled in an anti-CD47 monoclonal antibody clinical trial. To eliminate interference by the drug, we attempted alloadsorption using pooled O, RhD＋ RBCs, and the patient’s plasma in the ratio of 4:1. After three alloadsorption sessions using pooled allogeneic RBCs, the antibody screening and cross-matching issues of the globulin phase were resolved. The method used in this case is meaningful in that it can be easily used when drug interference occurs in a blood bank. (Korean J Blood Transfus 2023;34:26-31)

The sul1 Gene in Stenotrophomonas maltophilia With High-Level Resistance to Trimethoprim/Sulfamethoxazole

Emerging resistance to trimethoprim/sulfamethoxazole (SXT) poses a serious threat to the treatment of Stenotrophomonas maltophilia infections. We determined the prevalence and molecular characteristics of acquired SXT resistance in recent clinical S. maltophilia isolates obtained from Korea. A total of 252 clinical isolates of S. maltophilia were collected from 10 university hospitals in Korea between 2009 and 2010. Antimicrobial susceptibility was determined by using the CLSI agar dilution method. The sul1, sul2, and sul3 genes, integrons, insertion sequence common region (ISCR) elements, and dfrA genes were detected using PCR. The presence of the sul1 gene and integrons was confirmed through sequence analysis. Among the 32 SXT-resistant isolates, sul1 was detected in 23 isolates (72%), all of which demonstrated high-level resistance (> or =64 mg/L) to SXT. The sul1 gene (varying in size and structure) was linked to class 1 integrons in 15 of the 23 isolates (65%) harboring this gene. None of the SXT-susceptible isolates or the SXT-resistant isolates with a minimum inhibitory concentration of 4 and 8 mg/L were positive for sul1. Moreover, the sul2, sul3, and dfrA genes or the ISCR elements were not detected. The sul1 gene may play an important role in the high-level SXT resistance observed in S. maltophilia.

Multiplex PCR for Rapid Detection of Genes Encoding Class A Carbapenemases

In recent years, there have been increasing reports of KPC-producing Klebsiella pneumoniae in Korea. The modified Hodge test can be used as a phenotypic screening test for class A carbapenamase (CAC)-producing clinical isolates; however, it does not distinguish between carbapenemase types. The confirmation of type of CAC is important to ensure optimal therapy and to prevent transmission. This study applied a novel multiplex PCR assay to detect and differentiate CAC genes in a single reaction. Four primer pairs were designed to amplify fragments encoding 4 CAC families (SME, IMI/NMC-A, KPC, and GES). The multiplex PCR detected all genes tested for 4 CAC families that could be differentiated by fragment size according to gene type. This multiplex PCR offers a simple and useful approach for detecting and distinguishing CAC genes in carbapenem-resistant strains that are metallo-beta-lactamase nonproducers.