Fluoroquinolone resistance in Neisseria gonorrhoeae after cessation of ciprofloxacin usage in San Francisco: using molecular typing to investigate strain turnover.

BACKGROUND: Ciprofloxacin resistance (CipR) among gonococcal strains in San Francisco (SF) increased between 2001 and 2006 and decreased between 2007 and 2009. Molecular typing of isolates obtained from 2005 to 2009 was performed to elucidate changes in CipR prevalence. METHODS: A total of 2526 samples were collected at the SF City Clinic between 2001 and 2009. Minimum inhibitory concentrations to ciprofloxacin were obtained by agar dilution. Prevalences of CipR strains were determined, with corresponding confidence intervals (CIs). Between 2005 and 2009, 460 isolates were selected for molecular typing using Neisseria gonorrhoeae multiantigen sequence typing. RESULTS: Between 2001 and 2006, the prevalence of CipR increased from 3.4% (95% CI, 1.3%-5.4%) to 44% (95% CI, 39%-50%). However, in 2007 prevalence began to decrease, reaching 9.6% (95% CI, 6.0%-13%) by 2009. Of the 203 strain types identified between 2005 and 2009, 126 genogroups of closely related strain types were formed (varying by ≤1% at both target loci). Levels of CipR within the data set correlate with the prevalence of 3 major genogroups (G): G437, G1407, and G3112. CONCLUSIONS: Molecular typing reveals that CipR within the tested population is maintained by strain turnover between resistant genogroups. Despite early recommendation in 2002 to stop ciprofloxacin use in California, CipR in SF increased through 2006. The subsequent decrease in CipR corresponds with the 2007 national recommendation to cease ciprofloxacin treatment of gonorrhea, which suggests that national recommendations are potentially more effective at reducing CipR than regional recommendations in areas with high strain turnover.

The Multispot rapid HIV-1/HIV-2 differentiation assay is comparable with the Western blot and an immunofluorescence assay at confirming HIV infection in a prospective study in three regions of the United States.

BACKGROUND: A new HIV diagnostic algorithm has been proposed which replaces the use of the HIV-1 Western blot and HIV-1 immunofluorescence assays (IFA) as the supplemental test with an HIV-1/HIV-2 antibody differentiation assay. OBJECTIVES: To compare an FDA-approved HIV-1/HIV-2 antibody differentiation test (Multispot) as a confirmatory test with the HIV-1 Western blot and IFA. STUDY DESIGN: Participants were screened with an HIV-1/HIV-2 combination Antigen/Antibody (Ag/Ab) screening assay. Specimens with repeatedly reactive results were tested with Multispot and either Western blot or IFA. Specimens with discordant screening and confirmatory results were resolved with HIV-1 RNA testing. RESULTS: Individuals (37,876) were screened for HIV infection and 654 (1.7%) had a repeatedly reactive Ag/Ab assay result. On Multispot, 554 (84.7%) were HIV-1 reactive, 0 (0%) were HIV-2 reactive, 1 (0.2%) was reactive for both HIV-1 and HIV-2 (undifferentiated), 9 (1.4%) were HIV-1 indeterminate, and 90 (13.8%) were non-reactive. HIV-1 RNA was detected in 47/90 Multispot non-reactive (52.2%) specimens. Among specimens confirmed to have HIV infection (true positives), Multispot and Western blot detected HIV-1 antibody in a similar proportion of cases (93.7% vs. 94.4% respectively) while Multispot and IFA also detected HIV-1 antibody in a similar proportion of cases (84.5% vs. 83.4% respectively). CONCLUSIONS: In this study, Multispot confirmed HIV infections at a similar proportion to Western blot and IFA. Multispot, Western blot, and IFA, however, did not confirm all of the reactive Ag/Ab assay results and underscores the importance of HIV NAT testing to resolve discordant screening and confirmatory results.