Antimicrobial resistance of Neisseria gonorrhoeae in the municipality of Morón, Cuba: emergence of isolates with intermediate resistance to fluoroquinolones

Retrospective analysis of antimicrobial susceptibility trends (2000-2009) in Neisseria gonorrhoeae isolates from countries in Latin America and the Caribbean shows evolving resistance to ciprofloxacin, azithromycin and decreased susceptibility to ceftriaxone

BACKGROUND

The emergence of resistance and treatment failures to third generation cephalosporins prompted the revitalization of the global Gonococcal Antimicrobial Surveillance Program (GASP) to ensure that information regarding trends of the antimicrobial susceptibility of Neisseria gonorrhoeae isolates is up-to-date. Accordingly, former and potential GASP participants in Latin America and the Caribbean were contacted to reinitiate the GASP network in the region and to undertake a retrospective analysis of the antimicrobial susceptibility of N. gonorrhoeae isolates between 2000 and 2009.

METHODS

Eleven countries participated in this retrospective analysis reporting on the susceptibility of N. gonorrhoeae isolates to up to 6 antibiotics as well as national treatment guidelines over the period. Antimicrobial susceptibility determination was carried out using combination of agar dilution and disk diffusion (Clinical Laboratory and Standards Institute) or Etest. Antimicrobial susceptibility data from each country were aggregated and analyzed for antimicrobial resistance trends in the region.

RESULTS

More than 11,400 N. gonorrhoeae isolates were tested for antimicrobial susceptibility: 6 countries tested N. gonorrhoeae over the entire period and 5 countries tested sporadically. Decreased susceptibility to ceftriaxone was reported from 1 country (7 isolates, MICs >0.25 μg/ml) in 2007. No resistance to spectinomycin was reported. From 2000 to 2009, aggregated ciprofloxacin resistance increased from 2% (19/784) to 31% (311/1015) in 9 countries and azithromycin resistance increased from 6% (39/646) to 23% (225/962) in 4/6 reporting countries. Overall, resistance to penicillin and tetracycline decreased from 35% (441/1241) to 26% (258/975) and from 60% (476/792) to 35% (323/931), respectively.In 2009, resistance to gentamicin (3%, 4/122), chloramphenicol (5%, 6/120), and ofloxacin (2%, 6/120) was reported from 1 country.

CONCLUSIONS

The report of ceftriaxone-resistant isolates coupled with the emergence and spread of resistance to ciprofloxacin and azithromycin in Latin America and the Caribbean in the 2000s indicates the importance of active surveillance of N. gonorrhoeae antimicrobial susceptibility to determine antimicrobial resistance emerging trends so as to promptly inform and guide the development of effective treatment options for gonococcal infections.

Evaluation of the BIOCEN GC agar medium base in antimicrobial susceptibility testing of Neisseria gonorrhoeae

BACKGROUND

Since 1995, the Cuban Reference Laboratory for Neisseria has been monitoring the antibiotic susceptibility of gonococci, following the methodology of the National Committee for Clinical Laboratory Standards, which uses GC agar medium base supplemented with 1% Vitox. We evaluated three lots of GC agar medium base produced by BIOCEN, Cuba, in antibiotic susceptibility testing of reference and wild strains of gonococci.

METHODS

The susceptibilities to five antibiotics were evaluated five times on three lots of GC agar medium base from BIOCEN. Four and one gonococcal reference strains were tested by MIC dilution and disc diffusion methods, respectively. Later, the antimicrobial susceptibilities of ten wild Neisseria gonorrhoeae strains were tested in triplicate. As internal control, a GC agar medium from Difco was used.

RESULTS

All antibiotic MICs obtained on four lots of GC agar medium from different manufacturers fell within the proposed quality control limits for reference strains analyzed. The disc diffusion data for the reference strain of N. gonorrhoeae ATCC 49226 to five antibiotics provided essentially identical results in all lots of GC agar medium base. For wild strains of gonococci, identical modal MIC values and zone size diameters within a 3-mm range were observed in all the antibiotics tested.

CONCLUSIONS

Excellent agreement in susceptibility testing methods among different lots of GC agar medium base from BIOCEN and Difco was obtained for all reference and wild gonococcal strains and antibiotics tested. We proposed that GC medium from BIOCEN can be used in antimicrobial susceptibility testing of N. gonorrhoeae by MIC dilution and disc diffusion tests.

The use of fluoroquinolones in gonorrhoea: the increasing problem of resistance

The recent re-emergence of gonorrhoea in developed countries has been accompanied by the rise and spread of gonococcal resistance to the fluoroquinolones. In the 1980s fluoroquinolones were considered an important addition to the arsenal of agents used to treat gonorrhoea. They proved to be excellent drugs for this indication, including infections caused by penicillinase-producing and tetracycline-resistant strains of Neisseria gonorrhoeae. However, as gonococci have a well-recognised potential to develop resistance to antibiotics, the first reports of reduced susceptibility to fluoroquinolones appeared a few years after their introduction. Gonococcal resistance to fluoroquinolones is now well-established in the Far East, from where it has spread to Australia, Hawaii, California and Europe. In Africa and Latin America, gonococci continue to be susceptible to fluoroquinolones.

High percentages of resistance to tetracycline and penicillin and reduced susceptibility to azithromycin characterize the majority of strain types of Neisseria gonorrhoeae isolates in Cuba, 1995-1998

BACKGROUND

In many regions the susceptibility of Neisseria gonorrhoeae isolates to antimicrobial agents is rarely tested. The Gonococcal Antimicrobial Surveillance Program (GASP) in Cuba was established as part of a larger regional GASP program to facilitate the collection and reporting of antimicrobial susceptibility data for N gonorrhoeae isolates.

GOAL

The goal was to retrospectively determine the antimicrobial susceptibility and molecular epidemiology of 91 isolates of N gonorrhoeae isolated from 11 centers in Cuba.

STUDY DESIGN

Isolates of N gonorrhoeae were collected and presumptively identified from 11 Cuban provincial health centers. They were then forwarded to the National Laboratory of Pathogenic Neisseria Havana for confirmatory identification and were subsequently analyzed at the Center for GASP in Ottawa. Isolates were tested for susceptibility to penicillin, tetracycline, spectinomycin, ceftriaxone, ciprofloxacin, and azithromycin by the agar dilution method. To establish baseline data for molecular epidemiologic profiles, the auxotype (A), serovar (S), plasmid content (P), and TetM type of the isolates were determined. Certain A/S/P classes were further analyzed by pulsed field gel electrophoresis (PFGE).

RESULTS

High percentages of the 91 N gonorrhoeae isolates were resistant to penicillin (68%) and tetracycline (83.5%), with 56% being penicillinase-producing (PPNG) and 64% carrying plasmid-mediated tetracycline resistance (TRNG; 50% were PP/TRNG). An additional 14% of the isolates carried chromosomal resistance (CMRNG) to either tetracycline or penicillin or both antibiotics. All isolates were susceptible to spectinomycin, ceftriaxone, and ciprofloxacin. However, nine isolates were resistant to azithromycin (MIC, > or = 1.0 microgram/ml), and 43 other isolates displayed reduced susceptibility to this antibiotic (MIC, 0.25-0.5 microgram/ml). Although a total of 21 different A/S classes were identified, most of the isolates (61) belonged to three A/S classes: NR/IA-6 (35 isolates), NR/IB-1 (15 isolates), and P/IA-6 (11 isolates). Thirty-two of 45 PP/TRNG were A/S class NR/IA-6, and nine of the P/IA-6 isolates were TRNG. By contrast, most of A/S class NR/IB-1 (8) were CMRNG. PFGE analysis following digestion with NheI or SpeI further clustered the isolates into separate groups.

CONCLUSIONS

This study demonstrates high percentages of N gonorrhoeae isolates with penicillin and tetracycline resistance in Cuba. As has been noted in other studies in the Caribbean region and Latin America, resistance and reduced susceptibility to azithromycin are developing as emerging problems. Since penicillin and tetracycline continue to be widely used for the treatment of gonococcal infections in Cuba, this study indicates the importance of antimicrobial susceptibility surveillance so that effective antibiotics may be recommended for treatment of gonococcal infections.