Background: The Xpert MTB/RIF Ultra (Xpert Ultra) was introduced to enhance the sensitivity of tuberculosis detection, particularly in smear-negative cases, compared with its predecessor, Xpert MTB/RIF (Xpert). However, its performance in high-resource, intermediateburden settings remains unassessed. We prospectively compared the diagnostic accuracy of Xpert Ultra and Xpert for detecting Mycobacterium tuberculosis (MTB) and rifampin resistance in Korea. Methods: In total, 309 respiratory specimens were analyzed using both assays. We used two reference standards: mycobacterial culture and a composite reference standard based on clinical diagnosis and treatment decisions. Diagnostic performance, including sensitivity, specificity, and agreement between the two assays, was assessed. Spiking experiments using 13 MTB isolates with known rpoB mutations were performed to evaluate rifampin resistance detection. Results: Xpert Ultra showed increased, albeit not significantly, sensitivity (73.7% vs. 65.8% with culture; 63.8% vs. 53.2% with the composite reference standard) over Xpert. Its specificity was comparable to that of Xpert; however, a few false-positive results were observed among trace- and very low-positives. Among six culture-negative but Xpert Ultra-positive cases, two were clinically diagnosed as tuberculosis. Of the 13 rpoB mutant strains, Xpert correctly detected all mutations in the rifampin resistance-determining region, whereas Xpert Ultra yielded indeterminate results for Q432P and Q429H/L430P/H445Q. Conclusions Xpert Ultra tends to have increased sensitivity; however, it shows potential diagnostic ambiguity associated with trace- or very low-positive results. These findings highlight the importance of clinical correlation, particularly in culture-negative cases. Indeterminate results in certain rpoB mutations require cautious interpretation.

Background: The growing burden of nontuberculous mycobacteria (NTM) raises concerns regarding cross-reactivity in molecular tuberculosis (TB) diagnostics. In the current study, we evaluated whether high NTM loads affect Mycobacterium tuberculosis (MTB) detection or rifampin (RIF) resistance calls using Xpert MTB/RIF (Xpert) and Xpert MTB/RIF Ultra (Xpert Ultra). Methods: In vitro spiking experiments were performed by mixing eight NTM species (1 × 10 6 colony-forming unit [CFU]/mL) with heat-inactivated MTB (RIF-susceptible H37Rv; RIFresistant S450L) at 5 × 103 CFU/mL in pooled smear-negative sputum, before testing them in parallel using Xpert and Xpert Ultra. We also retrospectively analyzed 334 results from lower respiratory specimens, including 32 NTM-positive specimens tested using both assays, and assessed the presence of probe amplification in the NTM-confirmed specimens. Results: In spiking experiments, both assays showed no NTM-related cross-reactivity: RIFsusceptible mixes were “RIF resistance not detected,” S450L mixes were correctly resistant with preserved mutant melt peaks, and MTB-specific cycle threshold and melting peak temperature profiles were unchanged by NTM. Of the 334 clinical specimens, NTM was isolated from 32. Xpert classified all 32 as MTB-negative, and Xpert Ultra classified 31 of 32 as MTB-negative and one as “very low” positive in a patient with prior TB, consistent with residual nonviable DNA. In NTM-positive, Xpert/Xpert Ultra-negative specimens, neither assay showed probe amplification. Conclusion High-burden NTM did not compromise MTB detection or RIF-resistance determination using Xpert or Xpert Ultra. The assays demonstrated robust analytical specificity in mixed MTB–NTM contexts, supporting their use where NTM carriage is common.

Cis-AB and B(A) alleles encode an ABO enzyme with dual A and B glycosyltransferase activity. Although globally rare, the cis-AB phenotype is found relatively often in Korean, Japanese, and Chinese populations. Cases of the B(A) allele have been reported mostly in the Chinese population. Forward typing performed in a Cambodian woman with an ABO discrepancy demonstrated a strong reaction with anti-A and anti-B reagents, while there was no reaction with lectin anti-A 1. The anti-A 1 antibody was detected in reverse typing. Through ABO gene sequence analyses of exons 6 and 7, one of the alleles was identified as ABO*B.01. In contrast, the other allele harboring a c.803G＞C substitution was either ABO*cisAB.05 or ABO*BA.06 allele. The ABO*cisAB.05 and ABO*BA.06 alleles remain indistinguishable despite routine serological testing and ABO genotyping. To the best of the author’s knowledge, this is the first case report of these variants discovered in a Cambodian individual residing in Korea.

Cis-AB and B(A) alleles encode an ABO enzyme with dual A and B glycosyltransferase activity. Although globally rare, the cis-AB phenotype is found relatively often in Korean, Japanese, and Chinese populations. Cases of the B(A) allele have been reported mostly in the Chinese population. Forward typing performed in a Cambodian woman with an ABO discrepancy demonstrated a strong reaction with anti-A and anti-B reagents, while there was no reaction with lectin anti-A 1. The anti-A 1 antibody was detected in reverse typing. Through ABO gene sequence analyses of exons 6 and 7, one of the alleles was identified as ABO*B.01. In contrast, the other allele harboring a c.803G＞C substitution was either ABO*cisAB.05 or ABO*BA.06 allele. The ABO*cisAB.05 and ABO*BA.06 alleles remain indistinguishable despite routine serological testing and ABO genotyping. To the best of the author’s knowledge, this is the first case report of these variants discovered in a Cambodian individual residing in Korea.

Ocular setariases of cattle were reported but those of equine hosts have never been reported in the Republic of Korea (Korea). We found motile worms in the aqueous humor of 15 horses (Equus spp.) from 12 localities in southern parts of Korea between January 2004 and November 2017. After the affected animals were properly restrained under sedation and local anesthesia, 10 ml disposable syringe with a 16-gauge needle was inserted into the anterior chamber of the affected eye to successfully remove the parasites. The male worm that was found in 7 of the cases showed a pair of lateral appendages near the posterior terminal end of the body. The papillar arrangement was 3 pairs of precloacal, a pair of adcloacal, and 3 pairs of postcloacal papillae, plus a central papilla just in front of the cloaca. The female worms found in the eyes of 8 horses were characterized by the tapering posterior terminal end of the body with a smooth knob. Worms were all identified as Setaria digitata (von Linstow, 1906) by the morphologic characteristics using light and electron microscopic observations. This is the first blindness cases of 15 horses infected with S. digitata (Nematoda: Filarioidea) in Korea.
Anesthesia, Local ; Animals ; Anterior Chamber ; Aqueous Humor ; Blindness* ; Cattle ; Cloaca ; Female ; Horses* ; Humans ; Korea ; Male ; Needles ; Parasites ; Republic of Korea* ; Setariasis ; Syringes