Strain Typing and Antimicrobial Resistance of Fluoroquinolone-Resistant Neisseria gonorrhoeae Causing a California Infection Outbreak

Abstract

Antimicrobial-resistant Neisseria gonorrhoeae is an emerging public health problem as a result of the alarming limitation in treatment options. We examined an outbreak in California of fluoroquinolone-resistant Neisseria gonorrhoeae (QRNG) by evaluation of a combination of routine isolates from the Gonococcal Isolate Surveillance Project and isolates collected by expanded surveillance performed between April 2000 and June 2002. QRNG isolates were characterized by two methods: (i) determination of a combination of antibiogram, auxotype, serovar, Lip type, and patterns of amino acid alteration in the quinolone resistance-determining region of GyrA and ParC (ASLGP) and (ii) pulsed-field gel electrophoresis (PFGE). Strain typing was used to describe the QRNG outbreak strains and the associated antimicrobial resistance profiles. Among 79 isolates that were completely characterized, we identified 20 different ASLGP strain types, and 2 of the types were considered to belong to outbreak strains that comprised 65% (51/79) of the isolates. By PFGE typing, there were 24 different strain types, and 4 of these were considered outbreak types and comprised 66% (52/79) of the isolates. The overall agreement between the typing methods in distinguishing outbreak strains and nonoutbreak strains was 84% (66/79). The most common QRNG ASLGP strain type had chromosomally mediated resistance to penicillin and tetracycline and an azithromycin MIC of 0.5 g/ml. The occurrence of an outbreak caused by QRNG strains that could fail to be eradicated by most antibiotic classes reinforces the serious problem with antimicrobial resistance in Neisseria gonorrhoeae that the public health system faces. Adherence to a regimen with the recommended antibiotics at the appropriate dose is critical, and monitoring for antimicrobial susceptibility needs to be actively maintained to adapt treatment guidelines appropriately.

Clinically Relevant Antibiotic Resistance Mechanisms Can Enhance the In Vivo Fitness of Neisseria gonorrhoeae

“…This sequence of events is consistent with data from numerous molecular epidemiologic studies (Kam et al, 2003;Morris et al, 2009;Starnino et al, 2010;Tanaka, 1992;Trees et al, 2001;Vereshchagin et al, 2004). Analyses of clinical isolates have also provided insights into the nature of mutations directly associated with fluoroquinolone resistance in N. gonorrhoeae.…”

Review and International Recommendation of Methods for Typing Neisseria gonorrhoeae Isolates and Their Implications for Improved Knowledge of Gonococcal Epidemiology, Treatment, and Biology

“…Therefore, PFGE is particularly a useful method to increase discrimination between isolates in specific situations, especially those involving extreme microepidemiology (49,54,82,135,153,172,174,178). PFGE is reproducible, and all N. gonorrhoeae isolates are typeable by this method (24,54,71,80,87,105,111,113,132,133,135,153,154,156,170,172,174,178,179,182,196,197). The distinct disadvantages of RFLP and PFGE analysis include the requirement for a high level of technical and interpretive expertise, the potentially subjective interpretation of banding patterns on gels, the time involved for typing (several days), the lack of high-throughput analysis, and high cost.…”

“…DNA sequence analysis of the amplicons further differentiates N. gonorrhoeae strains with the same number of repeats, thus subtyping Lip patterns (166). This method has been used to characterize N. gonorrhoeae strains in outbreaks of quinolone resistance (105,106,167,168) and in forensic evaluation when combined with other typing methods (30). The discriminatory ability of this method remains to be assessed.…”

“…Digestion of genomic DNA with enzymes such as SpeI and/or BglII has proven to be highly discriminatory for N. gonorrhoeae. PFGE has been used to define the gonococcal strain populations in a particular region, to identify clusters of circulating strains, including antibiotic resistant strains (3,24,49,51,54,71,80,87,105,111,113,132,133,135,153,154,156,170,172,174,179,182,196,197), and in forensic evaluations (30; M. Unemo, unpublished data). This method can distinguish subtypes within A/S classes and within genotypes determined with other highly discriminatory DNA sequence-based methods, such as full-or extended-length porB sequencing and NG-MAST.…”

Gonorrhea in Men Sex Men and Heterosexual Men

“…Other molecular technique applicable for this purpose to N. gonorrhoeae are MLST and NG-MAST with discriminatory indices exceeding 0.9 (Tazi, 2010;Morris, 2009). …”