RESUMO
PURPOSE: Injectable ceftriaxone and oral cefixime are the last agents effective against Neisseria gonorrhoeae. In vitro antimicrobial-susceptibility testing (AST) is done to identify the most efficacious antibiotic needed to combat the infection in that particular individual. The objective of this study was to evaluate whether Kirby-Bauer (KB) disk-diffusion tests can detect N. gonorrhoeae isolates that have decreased susceptibility to ceftriaxone and cefixime for appropriate clinical management. METHODS: A total of 1,633 consecutive clinical isolates of N. gonorrhoeae were collected from January 1, 2013 to December 31, 2017 from seven dermatology clinics located in five provinces in China. Consistency between KB disk-diffusion tests and the agar-dilution method, as well as sensitivity of the KB test for detecting N. gonorrhoeae isolates with decreased susceptibility to ceftriaxone and cefixime, were determined using 1,306 clinical isolates that had been recovered to complete agar-dilution AST. RESULTS: The prevalence of isolates with decreased susceptibility to ceftriaxone and cefixime was 12.1% (198 of 1,633) and 12.7% (208 of 1,633), respectively, using KB disk-diffusion tests. The prevalence of isolates with decreased susceptibility was 9.9% (129 of 1,306) for ceftriaxone and 9.9% (129 of 1,305) for cefixime using agar-dilution AST. The categorical agreement of these two methods was 80.9% for both ceftriaxone and cefixime. Compared to agar-dilution AST, the sensitivity of the KB test for detecting N. gonorrhoeae isolates with decreased susceptibility was 22.5% (29 of 129) for ceftriaxone and 29.5% (38 of 129) for cefixime, and its specificity 87.3% (1,028 of 1,177) for ceftriaxone and 86.7% (1,018 of 1,176) for cefixime. CONCLUSION: Although KB tests are easy to carry out in clinical practice, their ability to detect cephalosporin-resistant gonorrhoea strains is limited. This method is not an appropriate selection for screening cephalosporin-resistant gonorrhoea strains in clinical practice in China.
RESUMO
A method for detection and genotyping of genital Chlamydia trachomatis infections based on omp1 gene amplification and sequencing was developed, and the character of omp1 gene of Chlamydia trachomatis was analysed. Urethral or endocervical specimens were collected from 323 patients attending STD clinics in Hengyang, Shanghai, Guangzhou and Jiangmen from November, 2003 to May, 2004. DNA was extracted by usual method, and an approximately 980bp fragment from the major outer membrane protein (omp1) gene of Chlamydia trachomatis was amplified by nested polymerase chain reaction (nPCR). The PCR products were purified by DNA agarose gel purification system and the sequence of the omp1 gene was determined by using an ABI PRISM 3700 Genetic Analyser, and genotyping was performed by BLAST similarity search. Multiple alignment was performed with CLUSTAL package (CLUSTAL X), and a phylogenetic tree was constructed by Mega3 software to illustrate the evolutionary relationships between clinical isolates and reference strains of C. trachomatis obtained from GenBank. All variable sequences were submitted to GenBank by Banklt programe. The overall prevalence of urogenital chlamydial infection was 29.7% (96 of 323). All the 96 C. trachomatis-positive cases were sequenced, and 10 genotypes and 28 genetic variants were detected. The most prevalent genotype was E(34.4%), followed by J(25.0%), D(12.5%), F(8.3%), G(7.3%), H(3.1%), Ba(3.1%), K(3.1%), Da (2.1% ), 1 (1.1%). The distribution of C. trachomatis genotypes in the four cities in sourth China was similar to other countries in the world. The omp1 gene was highly conserved for genotype E and F, but appeared slightly less conserved for other genotypes, where the sequences displayed one or several nucleotide substitutions relatived to the corresponding reference sequence. And a similar recombination was found between genotypes Ba and D in CD1. Phylogenetic tree showed that Chlamydia trachomatis genotypes were mainly divided into three clusters, according to previous grouping in the B, F-G, and C complexes. Clusters F-G and C were characterized by small genetic distances within each cluster, but clusters B displayed larger genetic distances. And the clinical isolates were highly related to the reference strains. It is concluded that the isolated Chlamydia trachomatis strains exhibit remarkable omp1 DNA sequence polymorphism, which can encourage for vaccine design and infection control.
