A DNA-based assay quickly identifies gonorrhea infections susceptible to the antibiotic ciprofloxacin and minimizes the use of ceftriaxone in a regular clinical setting, according to findings published in the May issue of Clinical Infectious Diseases.
In 2007, the Centers for Disease Control and Prevention stopped recommending the use of ciprofloxacin to treat gonococcal infections due to increased resistance to multiple drugs. However, about 80% of infections in the United States currently remain susceptible to the antibiotic.
In this study, Lao-Tzu Allan-Blitz, a medical student at the David Geffen School of Medicine at the University of California, Los Angeles (UCLA), and his colleagues analyzed the effect of a test that identifies infections susceptible to ciprofloxacin . The test detects a single base mutation (Ser91) in the Neisseria gonorrhoeae gyrase A (gyrA) gene that makes the bacterium resistant to ciprofloxacin. In cases lacking such a mutation, ciprofloxacin remains effective.
The laboratory-developed test, using freely available methods and reagents, was put into clinical use in November 2015 in the UCLA health system. Prior to implementation, physicians were trained in the use of the test and treatment recommendations based on the test results.
The researchers compared the prescriptions of ciprofloxacin or ceftriaxone for gonorrhea between January 2015 and July 2016, comparing the periods before and after the application. The study included treatment for 283 infections among 251 patients treated at UCLA facilities.
Of all the cases, 113 (39.9%) were treated empirically on the same day as the sample collection: 58 of 130 (44.6%) cases before application and 55 of 153 (35.9%) after P = 0.14).
Among post-implementation treatises, genotyping was successful for 121 (68.8%) of the 176 infections, and 72 of them (59.5%) were susceptible to ciprofloxacin. In other words, less than half of the genotyped infections required treatment with ceftriaxone.
In addition, the genotype appears to have changed the choice of drugs. Among non-emotionally treated infections, 68 of 72 (94.4%) patients received ceftriaxone prior to the implementation of the genotype, compared to 77 of 98 (78.6%) after genotype (P = 0.004).
The mean time to treatment did not differ significantly between the cases treated non-empirically before and after the genotype, at 5.5 days versus 4.7 days, respectively.
As of May 2016, electronic alerts were sent to physicians with the results of genotyping, which increased the use of the results. Of 35 cases infected with wild-type bacteria and treated empirically, ciprofloxacin increased from 3 of 24 (12.5%) cases in the first 7 months of genotyping (prior to reminder) to 9 of 11 (81 , 8%) cases in the final 2 months after the introduction of reminders (P <0.001).
“The reintroduction of antibiotics previously considered ineffective is a novel approach that can reduce the continued emergence of resistance, made possible by rapid molecular methods for targeted therapy,” write the researchers.
Limitations of the study include participants from a single health care system, no consideration of clinical outcomes, lack of randomization, and use of a molecular assay that may not be available everywhere.