BACKGROUND: Mutations in the quinolone resistance-determining regions (QRDRs) of Acinetobacter baumannii DNA gyrase (gyrA) and topoisomerase IV (parC) are linked to fluoroquinolone (FQ) resistance. We developed a mismatched PCR-restriction fragment length polymorphism (RFLP) assay to detect mutations in the gyrA and parC QRDRs associated with FQ resistance in A. baumannii. METHODS: Based on the conserved sequences of A. baumannii gyrA and parC, two primer sets were designed for mismatched PCR-RFLP to detect mutations in gyrA (codons 83 and 87) and parC (codons 80 and 84) by introducing an artificial restriction enzyme cleavage site into the PCR products. This assay was evaluated using 58 A. baumannii strains and 37 other Acinetobacter strains that have been identified by RNA polymerase β-subunit gene sequence analysis. RESULTS: PCR amplification of gyrA and parC was successful for all A. baumannii strains. In 11 FQ -susceptible strains, the gyrA and parC PCR products were digested by the selected restriction enzymes at the site containing gyrA (codons 83 and 87) and parC (codons 80 and 84). PCR products from 47 FQ-resistant strains containing mutations in gyrA and parC were not digested by the restriction enzymes at the site containing the mutation. As for the non-baumannii Acinetobacter strains, although amplification products for gyrA were obtained for 28 strains, no parC amplification product was obtained for any strain. CONCLUSIONS This assay specifically amplified gyrA and parC from A. baumannii and detected A. baumannii gyrA and parC mutations with FQ resistance.

We report a new risk stratification of invasive stage papillary thyroid carcinomas (PTCs) by combining invasive status, using extrathyroid invasion (Ex) status, and tumor growth speed using the Ki-67 labeling index (LI). Methods: We examined tumor recurrence in 167 patients with PTC who were surgically treated at the Kindai University Nara Hospital between 2010 and 2022. The patients were classified according to the degree of invasion [negative (Ex0) or positive (Ex1, Ex2, and Ex3)] and tumor growth speed expressed with Ki-67 LI, as low (<5%) or high (>5%). This study confirmed previous findings that the disease-free survival (DFS) rate in PTCs significantly differed between patients with a high and low Ki-67 index. Results: When combining Ex status (negative or positive) and Ki-67 proliferation status (low or high), the DFS rate of invasion in the negative, low Ki-67 LI group was only 1.1%, while that of invasion in the positive, high Ki-67 LI was 44.1%. This study reports for the first time that recurrence risks can be stratified accurately when combining carcinoma’s essential two features of extrathyroid invasion status and tumor growth speed. Conclusions: We believe the evidence for low tumor recurrence risk may contribute to use of more conservative treatment options for invasive-stage PTCs and help alleviate patient anxiety about tumor recurrence and death.

We report a new risk stratification of invasive stage papillary thyroid carcinomas (PTCs) by combining invasive status, using extrathyroid invasion (Ex) status, and tumor growth speed using the Ki-67 labeling index (LI). Methods: We examined tumor recurrence in 167 patients with PTC who were surgically treated at the Kindai University Nara Hospital between 2010 and 2022. The patients were classified according to the degree of invasion [negative (Ex0) or positive (Ex1, Ex2, and Ex3)] and tumor growth speed expressed with Ki-67 LI, as low (<5%) or high (>5%). This study confirmed previous findings that the disease-free survival (DFS) rate in PTCs significantly differed between patients with a high and low Ki-67 index. Results: When combining Ex status (negative or positive) and Ki-67 proliferation status (low or high), the DFS rate of invasion in the negative, low Ki-67 LI group was only 1.1%, while that of invasion in the positive, high Ki-67 LI was 44.1%. This study reports for the first time that recurrence risks can be stratified accurately when combining carcinoma’s essential two features of extrathyroid invasion status and tumor growth speed. Conclusions: We believe the evidence for low tumor recurrence risk may contribute to use of more conservative treatment options for invasive-stage PTCs and help alleviate patient anxiety about tumor recurrence and death.

We report a new risk stratification of invasive stage papillary thyroid carcinomas (PTCs) by combining invasive status, using extrathyroid invasion (Ex) status, and tumor growth speed using the Ki-67 labeling index (LI). Methods: We examined tumor recurrence in 167 patients with PTC who were surgically treated at the Kindai University Nara Hospital between 2010 and 2022. The patients were classified according to the degree of invasion [negative (Ex0) or positive (Ex1, Ex2, and Ex3)] and tumor growth speed expressed with Ki-67 LI, as low (<5%) or high (>5%). This study confirmed previous findings that the disease-free survival (DFS) rate in PTCs significantly differed between patients with a high and low Ki-67 index. Results: When combining Ex status (negative or positive) and Ki-67 proliferation status (low or high), the DFS rate of invasion in the negative, low Ki-67 LI group was only 1.1%, while that of invasion in the positive, high Ki-67 LI was 44.1%. This study reports for the first time that recurrence risks can be stratified accurately when combining carcinoma’s essential two features of extrathyroid invasion status and tumor growth speed. Conclusions: We believe the evidence for low tumor recurrence risk may contribute to use of more conservative treatment options for invasive-stage PTCs and help alleviate patient anxiety about tumor recurrence and death.