A clinical isolate of Neisseria gonorrhoeae with in vitro resistance to erythromycin and decreased susceptibility to azithromycin

Genetic Characterization and Enhanced Surveillance of Ceftriaxone-Resistant Neisseria gonorrhoeae Strain, Alberta, Canada, 2018

In July 2018, a case of Neisseria gonorrhoeae associated with ceftriaxone treatment failure was identified in Alberta, Canada. We identified the isolate and nucleic acid amplification testing (NAAT) specimen as the ceftriaxone-resistant strain multilocus sequence type 1903/NG-MAST 3435/NG-STAR 233, originally identified in Japan (FC428), with the same penA 60.001 mosaic allele and genetic resistance determinants. Core single-nucleotide variant (SNV) analysis identified 13 SNVs between this isolate and FC428. Culture-independent surveillance by PCR for the A311V mutation in the penA allele and N. gonorrhoeae multiantigen sequence typing directly from NAAT transport media positive for N. gonorrhoeae by NAAT did not detect spread of the strain. We identified multiple sequence types not previously detected in Alberta by routine surveillance. This case demonstrates the benefit of using culture-independent methods to enhance detection, public health investigations, and surveillance to address this global threat.

Multidrug-resistant and extensively drug-resistant Neisseria gonorrhoeae in Canada, 2012-2016

BACKGROUND

Neisseria gonorrhoeae have acquired resistance to many antimicrobials, including third generation cephalosporins and azithromycin, which are the current gonococcal combination therapy recommended by the Canadian Guidelines on Sexually Transmitted Infections.

OBJECTIVE

To describe antimicrobial susceptibilities for N. gonorrhoeae circulating in Canada between 2012 and 2016.

METHODS

Antimicrobial resistance profiles were determined using agar dilution of N. gonorrhoeae isolated in Canada 2012-2016 (n=10,167) following Clinical Laboratory Standards Institute guidelines. Data were analyzed by applying multidrug-resistant gonococci (MDR-GC) and extensively drug-resistant gonococci (XDR-GC) definitions.

RESULTS

Between 2012 and 2016, the proportion of MDR-GC increased from 6.2% to 8.9% and a total of 19 cases of XDR-GC were identified in Canada (0.1%, 19/18,768). The proportion of isolates with decreased susceptibility to cephalosporins declined between 2012 and 2016 from 5.9% to 2.0% while azithromycin resistance increased from 0.8% to 7.2% in the same period.

CONCLUSION

While XDR-GC are currently rare in Canada, MDR-GC have increased over the last five years. Azithromycin resistance in N. gonorrhoeae is established and spreading in Canada, exceeding the 5% level at which the World Health Organization states an antimicrobial should be reviewed as an appropriate treatment. Continued surveillance of antimicrobial susceptibilities of N. gonorrhoeae is necessary to inform treatment guidelines and mitigate the impact of resistant gonorrhea.

Quality assurance for antimicrobial susceptibility testing of Neisseria gonorrhoeae in Latin American and Caribbean countries, 2013-2015

OBJECTIVES

A Neisseria gonorrhoeae antimicrobial susceptibility quality control comparison programme was re-established in Latin America and the Caribbean to ensure antimicrobial susceptibility data produced from the region are comparable nationally and internationally.

METHODS

Three panels, consisting of N. gonorrhoeae isolates comprising reference strains and other characterised isolates were sent to 11 participating laboratories between 2013 and 2015. Antimicrobial susceptibilities for these isolates were determined using agar dilution, Etest or disc diffusion methods. Modal minimum inhibitory concentrations (MICs) for each panel isolate/antibiotic combination were calculated. The guidelines of the Clinical and Laboratory Standards Institute were used for interpretations of antimicrobial susceptibility. The agreement of MICs with the modal MICs was determined for each of the participating laboratories as well as for each of the antibiotics tested.

RESULTS

Five of 11 laboratories that participated in at least one panel had an overall average agreement between participants' MIC results and modal MICs of >90%. For other laboratories, agreements ranged from 60.0% to 82.4%. The proportion of agreement between interpretations for all the antibiotics, except penicillin and tetracycline, was >90%. The percentages of agreement between MIC results and their modes for erythromycin, spectinomycin, cefixime and azithromycin were >90%. Tetracycline, ceftriaxone and ciprofloxacin agreement ranged from 84.5% to 89.1%, while penicillin had 78.8% agreement between MICs and modal MICs.

CONCLUSIONS

The participating laboratories had acceptable results, similar to other international quality assurance programmes. It is important to ensure continuation of the International Gonococcal Antimicrobial Susceptibility Quality Control Comparison Programme to ensure that participants can identify and correct any problems in antimicrobial susceptibility testing for N. gonorrhoeae as they arise and continue to generate reproducible and reliable data.

Antimicrobial Susceptibility of Neisseria gonorrhoeae in Japan from 2000 to 2015

BACKGROUND

Gonococcal infections are difficult to treat because of their multidrug antimicrobial resistance. The outbreak of antimicrobial-resistant Neisseria gonorrhoeae has begun in Asia and particularly in Japan. Therefore, it is very important that we understand the trend of antimicrobial resistance of N. gonorrhoeae in Asia including Japan. Our surveillance of the antimicrobial susceptibility of N. gonorrhoeae began in 2000 under the guidance of the Department of Urology, Gifu University. We report our surveillance data from 2000 to 2015.

METHODS

We collected N. gonorrhoeae strains isolated from patients with gonococcal infections who visited our cooperating medical institutions in Japan from 2000 to 2015. MICs of penicillin G, cefixime, ceftriaxone, tetracycline, spectinomycin, azithromycin, and levofloxacin were determined by the agar dilution method approved by the Clinical and Laboratory Standards Institute.

RESULTS

From 2000 to 2015, 2471 isolates of N. gonorrhoeae were collected in Japan. High rates of nonsusceptibility to penicillin, tetracycline, levofloxacin, cefixime, and azithromycin were shown. Around 5% to 10% of the strains isolated had a 0.25-mg/L MIC of ceftriaxone in each year, and 6 strains (0.24%) with a 0.5-mg/L MIC of ceftriaxone were isolated throughout the study period. Approximately 5% to 10% of the strains were resistant to each of ceftriaxone, azithromycin, and levofloxacin according to European Committee on Antimicrobial Susceptibility Testing breakpoints, and the rate has not increased significantly.

CONCLUSIONS

From this study and previous pharmacodynamic analyses, a single 1-g dose of ceftriaxone is recommended to treat gonorrhea. As strains with high-level ceftriaxone resistance continue to spread, higher doses of ceftriaxone in monotherapy or multiple doses of ceftriaxone should be considered.

Quality Assurance for Antimicrobial Susceptibility Testing of Neisseria gonorrhoeae in Canada, 2003 to 2012

Data from the Canadian National Gonococcal Antimicrobial Susceptibility Comparison Program, including results from 25 proficiency panels distributed between 2003 and 2012, were analyzed. The average MIC agreement between the participating laboratories ranged from 85.6% to 98.8% over the 10-year period, with the interpretation agreement ranging from 85.7% to 98.1%.

Antimicrobial resistance to Neisseria gonorrhoeae in Canada: 2009-2013

Background

Gonorrhea is on the rise in Canada. Treatment has been complicated by the fact that Neisseria gonorrhoeae has acquired resistance to many antibiotics, including penicillin, tetracycline, erythromycin and ciprofloxacin. The emergence of isolates with decreased susceptibilities to the third generation cephalosporins and reports of treatment failures in Canada and around the world are cause for concern.

Objective

To assess the resistance levels of common antibiotics to N. gonorrhoeae and to observe trends in resistance and/or decreased susceptibility to ciprofloxacin, third generation cephalosporins and azithromycin.

Methods

Laboratory surveillance data for N. gonorrhoeae isolates submitted by provincial microbiology laboratories to the National Microbiology Laboratory (NML) from 2009-2013 were compared.

Results

Since 2009, there has been an overall rise in antibiotic-resistant N. gonorrhoeae. In 2013, 24.3% of the isolates were resistant to erythromycin, 18.9% were resistant to penicillin, 33.0% were resistant to tetracycline, and 29.3% were resistant to ciprofloxacin. The percentage of isolates with decreased susceptibility to ceftriaxone (≥0.125 mg/L) and/or cefixime (≥0.25 mg/L) was 3.9% in 2013. This number represents a decrease from 5.9% in 2012 and 7.6% in 2011. The proportion of azithromycin resistant (MIC ≥2 mg/L) N. gonorrhoeae isolates increased from 0.4% in 2009 to 1.2% in 2013.

Conclusion

Resistance to erythromycin, penicillin, tetracycline and ciprofloxacin is common. Decreased susceptibility to ceftriaxone and/or cefixime is now almost 4% and azithromycin resistance is emerging but remains low at 1.2%. These results have informed the gonococcal infection treatment recommendations in the Canadian Guidelines on Sexually Transmitted Infections.

Whole-genome phylogenomic heterogeneity of Neisseria gonorrhoeae isolates with decreased cephalosporin susceptibility collected in Canada between 1989 and 2013

A large-scale, whole-genome comparison of Canadian Neisseria gonorrhoeae isolates with high-level cephalosporin MICs was used to demonstrate a genomic epidemiology approach to investigate strain relatedness and dynamics. Although current typing methods have been very successful in tracing short-chain transmission of gonorrheal disease, investigating the temporal evolutionary relationships and geographical dissemination of highly clonal lineages requires enhanced resolution only available through whole-genome sequencing (WGS). Phylogenomic cluster analysis grouped 169 Canadian strains into 12 distinct clades. While some N. gonorrhoeae multiantigen sequence types (NG-MAST) agreed with specific phylogenomic clades or subclades, other sequence types (ST) and closely related groups of ST were widely distributed among clades. Decreased susceptibility to extended-spectrum cephalosporins (ESC-DS) emerged among a group of diverse strains in Canada during the 1990s with a variety of nonmosaic penA alleles, followed in 2000/2001 with the penA mosaic X allele and then in 2007 with ST1407 strains with the penA mosaic XXXIV allele. Five genetically distinct ESC-DS lineages were associated with penA mosaic X, XXXV, and XXXIV alleles and nonmosaic XII and XIII alleles. ESC-DS with coresistance to azithromycin was observed in 5 strains with 23S rRNA C2599T or A2143G mutations. As the costs associated with WGS decline and analysis tools are streamlined, WGS can provide a more thorough understanding of strain dynamics, facilitate epidemiological studies to better resolve social networks, and improve surveillance to optimize treatment for gonorrheal infections.

The role of core groups in the emergence and dissemination of antimicrobial-resistant N gonorrhoeae

Core groups contain individuals who are regularly infected with Neisseria gonorrhoeae and are able to transmit their infection to a large number of sexual partners. Classical core groups, such as sex workers and their male partners, or men who have sex with men (MSM), have contributed to the emergence and spread of antimicrobial-resistant N gonorrhoeae over many years. Sex workers and their clients were the most important core group driving the dissemination of penicillinase-producing N gonorrhoeae in the 1970s. Such individuals have continued to contribute to penicillinase-producing N gonorrhoeae outbreaks as well as to the subsequent emergence of gonococcal resistance to fluoroquinolones, macrolides, spectinomycin and cephalosporins in various settings. MSM have been a very important core group since the 1980s, first with the spread of TetM-expressing N gonorrhoeae and, second, with the dissemination of fluoroquinolone-resistant N gonorrhoeae. MSM-associated sexual networks have most recently been critical to the spread of gonococci resistant to third generation extended spectrum cephalosporins, including cefixime and ceftriaxone. Individuals within other core groups have also been linked to the transmission of antimicrobial-resistant gonorrhoea, such as military personnel, travellers, drug users, young adults, older men and members of street gangs. Understanding core behaviours and their geospatial clustering is essential for an optimal public health response to the rising prevalence of antimicrobial-resistant gonorrhoea. Furthermore, rapid and effective treatment of N gonorrhoeae infections in core individuals and their sexual partners should be a priority for gonorrhoea control programmes.

Antimicrobial susceptibilities and distribution of sequence types of Neisseria gonorrhoeae isolates in Canada: 2010

The monitoring of antimicrobial susceptibilities in Neisseria gonorrhoeae isolates and characterization of N. gonorrhoeae multiantigen sequence types (NG-MAST, ST) provide important surveillance data as resistance rates continue to rise. A total of 2970 N. gonorrhoeae isolates were collected by Canadian provincial public health laboratories in 2010, and 1233 were submitted to the National Microbiology Laboratory for testing. The NG-MAST and minimum inhibitory concentration (MIC) by agar dilution were determined for each isolate. Of the 2970 isolates, 25.1% were resistant to penicillin, 34.6% resistant to tetracycline, 31.5% resistant to erythromycin, 35.9% resistant to ciprofloxacin, and 1.2% resistant to azithromycin. Decreased susceptibility to cefixime (MIC ≥ 0.25 mg/L) and ceftriaxone (MIC ≥ 0.125 mg/L) was identified in 3.2% and 7.3% of the isolates, respectively. The most common STs found in Canada were ST1407 (13.3%), ST3150 (11.3%), and ST3158 (9.0%), with 249 different STs identified among the isolates. Within the ST1407 group, 19.5% and 43.3% isolates have decreased susceptibility to cefixime and ceftriaxone, respectively. ST1407, the most prevalent NG-MAST in Canada in 2010, has been associated with high-level ceftriaxone MICs and with cefixime treatment failure cases worldwide. Identification and monitoring of STs and corresponding antimicrobial resistance profiles may be useful in surveillance programs and be used to inform public health actions.

Trends in antimicrobial resistance in Neisseria gonorrhoeae isolated in Canada: 2000-2009

BACKGROUND

Canada conducts surveillance of penicillin, tetracycline, erythromycin, spectinomycin, ciprofloxacin, cefixime, and ceftriaxone susceptibilities in Neisseria gonorrhoeae isolates to support development of national treatment guidelines for sexually transmitted infections.

METHODS

N. gonorrhoeae isolates were collected by Canadian provincial public health laboratories and included isolates from males and females ranging in age from 1 to 86 years. Minimum inhibitory concentrations (MICs) were determined by agar dilution at the National Microbiology Laboratory, Public Health Agency of Canada, and MIC interpretations were based on the criteria of the Clinical Laboratory Standards Institute.

RESULTS

From 2000 to 2009, 40,875 isolates of N. gonorrhoeae were tested by provincial laboratories and 10,993 of these were characterized by the Public Health Agency of Canada. There was an increasing incidence of N. gonorrhoeae isolates that were chromosomally resistant to penicillin, tetracycline, and erythromycin while the plasmid-mediated resistance strains (penicillinase-producing N. gonorrhoeae, tetracycline-resistant N. gonorrhoeae, and PP/tetracycline-resistant N. gonorrhoeae strain all had a declining trend. The percentage of isolates resistant to ciprofloxacin significantly increased from 1.3% in 2000 to 25.5% in 2009. Only 0.17% of isolates tested were azithromycin resistant. Between 2000 and 2009, the modal MICs for ceftriaxone increased from 0.016 μg/mL to 0.063 μg/mL.

CONCLUSIONS

Ciprofloxacin resistance in N. gonorrhoeae within Canada has increased to a level where quinolones are no longer the preferred drugs for the treatment of gonococcal infections and the modal MICs for the third-generation cephalosporins have increased over time. Close monitoring of antibiotic susceptibilities are required to inform treatment options.

The laboratory diagnosis of Neisseria gonorrhoeae

The present article describes the laboratory diagnosis of Neisseria gonorrhoeae by culturing of the organism from different types of clinical specimens followed by confirmatory tests. The success of culture methods requires good quality collection and transport of clinical specimens. The present guide describes the media requirements and cultural conditions for N gonorrhoeae growth and the characteristics for a presumptive identification of N gonorrhoeae. Confirmatory tests include biochemical tests, chromogenic enzyme substrate tests, immunoassays and nucleic acid methods. Nucleic acid detection methods include either amplification-based methods or nonamplification tests, and are increasingly used in clinical laboratories where a viable culture is not possible to obtain. Nucleic acid methods can also be used to detect the presence of low numbers in a specimen. Nucleic acid detection methods need confirmation with another amplification method or gene target. Controls must be included to ensure true positive and negative results, and to rule out nucleic acid contamination. Monitoring of antimicrobial susceptibilities of N gonorrhoeae is important to investigate treatment failure and to evaluate the efficacy of currently recommended therapies. Many methods for the characterization of N gonorrhoeae require cultures. The useful typing methods for determining strain relatedness include auxotyping, serotyping, plasmid profile analysis, DNA sequencing of the porB gene and pulsed-field gel electrophoresis. Quality assurance programs for diagnostic testing and antimicrobial susceptibility testing is reviewed.

Emerging resistance in Neisseria meningitidis and Neisseria gonorrhoeae

The value of monitoring antimicrobial resistance is particularly significant for Neisseria meningitidis and Neisseria gonorrhoeae diseases, even if it is for different reasons. Although there is no global alert for the spread of resistant meningococcal strains, the emergence of resistance is correlated to the outcome of treatment and the successful prophylaxis of close contacts. Few cases of resistance among meningococci have been recorded worldwide; it remains unclear what intriguing mechanism is responsible for maintaining resistance in these cases in the absence of significant antibiotic selective pressure, as in the case of penicillin; on the contrary, although rifampicin is the antibiotic of choice in the prophylaxis of close contacts, there is a very low rate of resistance. The emergence of multidrug-resistant N. gonorrhoeae is a great challenge in controlling gonorrhea as one of the main sexually transmitted bacterial diseases. International surveillance programs permit the monitoring of the susceptibility of the pathogen and allow the revision of the standardized treatment regimen when the situation changes.

Emergence of quinolone resistance and cephalosporin MIC creep in Neisseria gonorrhoeae isolates from a cohort of young men in Kisumu, Kenya, 2002 to 2009

We evaluated antimicrobial resistance in Neisseria gonorrhoeae isolated from men enrolled in a randomized trial of male circumcision to prevent HIV. Urethral specimens from men with discharge were cultured for N. gonorrhoeae. MICs were determined by agar dilution. Clinical and Laboratory Standards Institute (CLSI) criteria defined resistance: penicillin, tetracycline, and azithromycin MICs of ≥2.0 μg/ml; a ciprofloxacin MIC of ≥1.0 μg/ml; and a spectinomycin MIC of ≥128.0 μg/ml. Susceptibility to ceftriaxone and cefixime was shown by an MIC of ≤0.25 μg/ml. Additionally, PCR amplification identified mutations in parC and gyrA genes in selected isolates. From 2002 to 2009, 168 N. gonorrhoeae isolates were obtained from 142 men. Plasmid-mediated penicillin resistance was found in 65%, plasmid-mediated tetracycline resistance in 97%, and 11% were ciprofloxacin resistant (quinolone-resistant N. gonorrhoeae [QRNG]). QRNG appeared in November 2007, increasing from 9.5% in 2007 to 50% in 2009. Resistance was not detected for spectinomycin, cefixime, ceftriaxone, or azithromycin, but MICs of cefixime (P = 0.018), ceftriaxone (P < 0.001), and azithromycin (P = 0.097) increased over time. In a random sample of 51 men, gentamicin MICs were as follows: 4 μg/ml (n = 1), 8 μg/ml (n = 49), and 16 μg/ml (n = 1). QRNG increased rapidly and alternative regimens are required for N. gonorrhoeae treatment in this area. Amid emerging multidrug-resistant N. gonorrhoeae, antimicrobial resistance surveillance is essential for effective drug choice. High levels of plasmid-mediated resistance and increasing MICs for cephalosporins suggest that selective pressure from antibiotic use is a strong driver of resistance emergence.

Prevalence of and risk factors for quinolone-resistant Neisseria gonorrhoeae infection in Ontario

BACKGROUND

Quinolone-resistant Neisseria gonorrhoeae has swiftly emerged in Canada. We sought to determine its prevalence in the province of Ontario and to investigate risk factors for quinolone-resistant N. gonorrhoeae infection in a Canadian setting.

METHODS

We used records from the Public Health Laboratory of the Ontario Agency for Health Protection and Promotion in Toronto, Ontario, and the National Microbiology Laboratory in Winnipeg, Manitoba, to generate epidemic curves for N. gonorrhoeae infection. We extracted limited demographic data from 2006 quinolone-resistant N. gonorrhoeae isolates and from a random sample of quinolone-susceptible isolates. We also extracted minimum inhibitory concentrations for commonly tested antibiotics.

RESULTS

Between 2002 and 2006, the number of N. gonorrhoeae infections detected by culture decreased by 26% and the number of cases detected by nucleic acid amplification testing increased 6-fold. The proportion of N. gonorrhoeae isolates with resistance to quinolones increased from 4% to 28% over the same period. Analysis of 695 quinolone-resistant N. gonorrhoeae isolates and 688 quinolone-susceptible control isolates from 2006 showed a higher proportion of men (odds ratio [OR] 3.1, 95% confidence interval [CI] 2.3-4.1) and patients over 30 years of age (OR 3.1, 95% CI 2.4-3.8) in the quinolone-resistant group. The proportion of men who have sex with men appeared to be relatively similar in both groups (OR 1.4, 95% CI 1.1-1.8). Quinolone-resistant strains were more resistant to penicillin (p < 0.001), tetracycline (p < 0.001) and erythromycin (p < 0.001). All isolates were susceptible to cefixime, ceftriaxone, azithromycin and spectinomycin.

INTERPRETATION

During 2006 in Ontario, 28% of N. gonorrhoeae isolates were resistant to quinolones. Infections in heterosexual men appear to have contributed significantly to the quinolone resistance rate. Medical practitioners should be aware of the widespread prevalence of quinolone-resistant N. gonorrhoeae and avoid quinolone use for empiric therapy.

Update on the management of gonorrhea in adults in the United States

Gonorrhea, the second most commonly reported notifiable disease, is an important cause of cervicitis, urethritis, and pelvic inflammatory disease. The selection of appropriate therapy for gonorrhea (i.e., safe, highly effective, single dose, and affordable) is complicated by the ability of Neisseria gonorrhoeae to develop resistance to antimicrobial therapies. This article reviews the key questions and data that informed the 2006 gonorrhea treatment recommendations of the Centers for Disease Control and Prevention. Key areas addressed include the criteria used to select effective treatment for gonorrhea, the level of antimicrobial resistance at which changing treatment regimens is recommended, the epidemiology of resistance, and the use of quinolones, cephalosporins, and other classes of antimicrobials for the treatment of uncomplicated gonorrhea.

Characterization of proline, citrulline, and uracil auxotrophic plasmid-carrying Neisseria gonorrhoeae strains in Canada, 1993-2003

BACKGROUND AND OBJECTIVE

Proline, citrulline, and uracil (PCU) Neisseria gonorrhoeae is a common auxotroph in Canada and resistance to antibiotics in this auxotroph is rare.

GOAL

The goal of this study was to determine the characteristics of the PCU strains that have plasmids.

STUDY DESIGN

PCU strains sent between 1993 and 2003 for reference work to the National Microbiology Laboratory were analyzed for their plasmid profiles and antimicrobial susceptibilities. PCU strains containing plasmids and/or antimicrobial resistant were serotyped, and por and tbpB genes were sequenced to determine their antigenic types.

RESULTS

Forty strains containing plasmids were identified; serotype IB-11 and por/tbpB sequence type 2 was the most common pattern (28 of 40 strains [70%]). One strain had plasmids that conferred resistance to penicillin and tetracycline and 4 plasmidless strains were resistant to tetracycline.

CONCLUSION

PCU auxotrophic N. gonorrhoeae carrying plasmids and/or that have chromosomal genes mutated to resist antimicrobials have been identified in Canada. This shows the competency of this pathogen to survive under antimicrobial pressure and the importance of continuous surveillance.

Fluoroquinolone-resistant Neisseria gonorrhoeae: the inevitable epidemic

The worldwide incidence of fluoroquinolone-resistant Neisseria gonorrhoeae has increased dramatically in the last few years. Single doses of fluoroquinolones can no longer be used to treat N gonorrhoeae infections acquired in the Far East, parts of the Middle East, the Pacific Islands, and parts of Western Europe and the United States. Although California and Hawaii account for most of the current United States cases, the increased incidence of FQR in some high-risk groups independent of geography heralds an imminent spread of drug-resistant strains throughout the rest of the population. The use of molecular tests has revolutionized the diagnostic field in STIs. The main limitation of their application in N gonorrhoeae testing has been the loss of culture specimens that allow antimicrobial sensitivity testing. New molecular methods have made it possible to detect antimicrobial resistance without the use of live organisms. These tests hold the promise of improving epidemiologic tracking of N gonorrhoeae drug resistance, leading to better patient management at the local level. The loss of fluoroquinolones limits available oral regimens to a single CDC-recommended antibiotic, cefixime. Oral, inexpensive, single-dose alternatives are needed to ensure continued therapeutic success.

Trends of Chromosomally Mediated Antimicrobial Resistance in Neisseria gonorrhoeae in Canada: 1994–1999

BACKGROUND AND OBJECTIVES

We monitored the trends of chromosomally mediated resistant Neisseria gonorrhoeae (CMRNG) in Canada. Chromosomally resistant N. gonorrhoeae (CMRNG) were defined as having resistance to 3 antibiotics: penicillin (minimum inhibitory concentration [MIC] > or =2.0 mg/L), tetracycline (MIC > or =2.0 mg/L and < or =8.0 mg/L), and erythromycin (MIC > or =2.0 mg/L).

GOAL

The goal was to provide surveillance data for public health interventions for the control of gonococcal infections.

STUDY DESIGN

Antibiotic susceptibility tests were performed on N. gonorrhoeae isolates obtained from 1994 to 1999 in Canada. Strains were further characterized by auxotype (A), serovar (S), and plasmid profile (P).

RESULTS

Between 1994 and 1999, 19.2% of strains were CMRNG, 12.9% had a combined resistance to tetracycline and erythromycin, and 4.7% were resistant to tetracycline. The incidence of ciprofloxacin resistance and azithromycin resistance was 2.3% and 0.8%, respectively.

CONCLUSION

This survey of N. gonorrhoeae provides strain characterization data and temporal trends of strains in the Canadian population. CMRNG strains are on the rise, and the continual monitoring and characterization of these strains is important for the evaluation of current recommended antibiotic therapies used in Canada.

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.

Antimicrobial susceptibility of Neisseria gonorrhoeae in Cuba (1995-1999): implications for treatment of gonorrhea

BACKGROUND

Antibiotic-resistant strains of Neisseria gonorrhoeae, especially those resistant to penicillin and tetracycline, have spread with remarkable rapidity in many Caribbean countries.

GOAL

The goal of the study was to survey the antibiotic susceptibilities of N gonorrhoeae strains isolated from 1995 to 1999 in Cuba and to discuss the impact of antimicrobial resistance on the management of gonorrhea in the country.

STUDY DESIGN

Susceptibility of the strains to penicillin, tetracycline, cefuroxime, ceftriaxone, ciprofloxacin, spectinomycin, and azithromycin were determined by an agar dilution method.

RESULTS

Penicillin and tetracycline resistance was noted in 60.8% and 54.2%, respectively, of the N gonorrhoeae strains tested. A total of 63.35 (76/120) of the N gonorrhoeae strains exhibited plasmid-mediated resistance to penicillin, tetracycline, or both. Strains with chromosomally mediated resistance to these antibiotics accounted for 10% (12/120) of the strains. The strains were susceptible to ceftriaxone, cefuroxime, spectinomycin, and ciprofloxacin. One strain's ciprofloxacin MIC was 0.125 mircog/ml. Of the 52 strains tested, 23.1% displayed intermediate resistance to azithromycin.

CONCLUSIONS

N gonorrhoeae strains exhibited a high frequency of resistance and multiresistance to penicillin and tetracycline. Therefore, these antibiotics should no longer be used to treat gonococcal infections in Cuba and should be substituted with effective drugs such as third-generation cephalosporins, spectinomycin, and fluoroquinolones. The detection of intermediate resistance to azithromycin and ciprofloxacin underlines the importance of periodic surveillance for susceptibility of N gonorrhoeae strains to antimicrobials agents used as primary therapy for gonorrhea.

Characterization of ciprofloxacin resistance in Neisseria gonorrhoeae isolates in Canada

BACKGROUND

Ciprofloxacin (500 mg orally, single dose) is one of the recommended therapies for gonorrhea in Canada. In Canada, the first ciprofloxacin-resistant (CipR) Neisseria gonorrhoeae strain was isolated in 1993. Antimicrobial susceptibilities of N gonorrhoeae isolates were monitored as part of a national surveillance program to ensure efficacy of antimicrobial therapies.

GOAL

The goal was to determine the characteristics of ciprofloxacin resistance in Canadian gonococcal isolates.

STUDY DESIGN

Susceptibility testing was performed on gonococcal strains from different provinces in Canada to determine the prevalence of CipR strains and their distribution. The CipR strains were further differentiated according to auxotype (A), serotype (S), plasmid profile (P), and pulsed-field gel electrophoresis (PFGE) profile. DNA sequencing and DNA microarray technology were used to determine mutations in gyrA and parC.

RESULTS

In Canada, between 1997 and 1999, 4.8% of resistant strains (130 of 2687 antibiotic-resistant N gonorrhoeae isolates) were CipR (MICs of 1-32 microg/l) and belonged to 48 A/S/P classes. Sixty-eight of the strains that were not differentiated by A/S/P were subtyped into 47 classes with PFGE. DNA sequencing and DNA microarray showed that the most common mutations had amino acid substitutions of Ser-->Phe at codon 91 and Asp-->Gly at codon 95 of the gyrA and Ser-->Arg at codon 87 of parC.

CONCLUSION

The CipR strains isolated in Canada are phenotypically and genotypically diverse, indicating that they were imported from overseas and not endemic in Canada. Mutations in gyrA and parC previously only identified by DNA sequencing were successfully identified with DNA microarray technology. DNA microarray technology could be an alternative tool for identifying point mutations in resistance genes or other epidemiologic markers when clinical laboratories replace culture methods with rapid and automated molecular methods for diagnosis.

Mutation in 23S rRNA associated with macrolide resistance in Neisseria gonorrhoeae

Fifty-six azithromycin-resistant (MICs, 2.0 to 4.0 micro g/ml) Neisseria gonorrhoeae strains with cross-resistance to erythromycin (MICs, 2.0 to 64.0 micro g/ml), isolated in Canada between 1997 and 1999, were characterized, and their mechanisms of azithromycin resistance were determined. Most (58.9%) of them belonged to auxotype-serotype class NR/IB-03, with a 2.6-mDa plasmid. Based on resistance to crystal violet (MICs >or= 1 micro g/ml), 96.4% of these macrolide-resistant strains appeared to have increased efflux. Nine of the eleven strains selected for further characterization were found to have a promoter region mtrR mutation, a single-base-pair (A) deletion in the 13-bp inverted repeat, which is believed to cause overexpression of the mtrCDE-encoded efflux pump. The two remaining macrolide-resistant strains (erythromycin MIC, 64.0 micro g/ml; azithromycin MIC, 4.0 micro g/ml), which did not have the mutation in the mtrR promoter region, were found to have a C2611T mutation (Escherichia coli numbering) in the peptidyltransferase loop in domain V of the 23S rRNA alleles. Although mutations in domain V of 23S rRNA alleles had been reported in other bacteria, including E. coli, Streptococcus pneumoniae, and Helicobacter pylori, this is the first observation of these mutations associated with macrolide resistance in N. gonorrhoeae.

Antimicrobial susceptibility of Neisseria gonorrhoeae isolates from three Caribbean countries: Trinidad, Guyana, and St. Vincent

BACKGROUND

The percentage of Neisseria gonorrhoeae isolates resistant to antimicrobial agents commonly used for treatment is unknown in many Caribbean countries.

GOAL

To determine the antimicrobial susceptibility of N gonorrhoeae isolates from Trinidad (144 isolates), Guyana (70 isolates), and St. Vincent (68 isolates) so baseline data can be established for further studies, and to assist in establishing effective treatment guidelines.

STUDY DESIGN

Consecutive urethral and endocervical specimens from several clinics were collected and identified as N gonorrhoeae. Isolates of N gonorrhoeae were tested for their susceptibility to penicillin, tetracycline, ceftriaxone, ciprofloxacin, spectinomycin, and azithromycin. The presumptive identification of penicillinase-producing N gonorrhoeae and/or tetracycline-resistant N gonorrhoeae isolates based on MIC was confirmed by plasmid and tetM content analysis.

RESULTS

High percentages of penicillin and/or tetracycline resistance were observed in N gonorrhoeae isolates from Guyana (92.9%), St. Vincent (44.1%), and Trinidad (42.4%). Isolates from all three countries were susceptible to ceftriaxone, ciprofloxacin, and spectinomycin. One penicillinase-producing N gonorrhoeae/tetracycline-resistant N gonorrhoeae from Guyana had an MIC of 0.5 microg/l to ciprofloxacin. This and nine other isolates from Guyana also were resistant to azithromycin (defined as MIC > or = 2.0 microg/ml) as well as penicillin and tetracycline. A reduced susceptibility to azithromycin was displayed by 16% of the isolates from St. Vincent and 72% of the isolates from Guyana (MIC, 0.25-1.0 microg/ml). Most penicillinase-producing N gonorrhoeae isolates carried Africa-type plasmids (61/90), with 28 of 90 having Toronto-type plasmids and a single isolate carrying an Asia-type plasmid. The tetM determinant in tetracycline-resistant N gonorrhoeae isolates was predominantly of the Dutch type (68/91).

CONCLUSIONS

The high prevalence of N gonorrhoeae isolates from 3 of 21 English- and Dutch-speaking Caricom countries in the Caribbean with either plasmid-mediated or chromosomal resistance to penicillin and tetracycline supports international observations that these drugs should not be used to treat gonococcal infections. The detection of isolates with reduced susceptibility to drugs such as azithromycin, which currently are recommended for treatment in the region, attest to the importance of the continued monitoring of gonococcal antimicrobial susceptibility for the maintenance of effective treatment guidelines.

Decreased azithromycin susceptibility of Neisseria gonorrhoeae due to mtrR mutations

Single-dose azithromycin therapy has recently been used in Uruguay for the treatment of uncomplicated gonococcal infections. As part of an active surveillance study to monitor the emergence of antibiotic resistance in gonococcal isolates, we examined the levels of azithromycin susceptibility in 51 consecutive isolates obtained from males with uncomplicated gonococcal urethritis. Isolates with decreased susceptibility to azithromycin (MICs, 0.25 to 0.5 microg/ml) were common, and these isolates often displayed cross-resistance to hydrophobic antimicrobial agents (erythromycin and Triton X-100). Resistance to erythromycin and Triton X-100 is frequently due to overexpression of the mtrCDE-encoded efflux pump mediated by mutations in the mtrR gene, which encodes a transcriptional repressor that modulates expression of the mtrCDE operon. Accordingly, we questioned whether clinical isolates that express decreased azithromycin susceptibility harbor mtrR mutations. Promoter mutations that would decrease the level of expression of mtrR as well as a missense mutation at codon 45 in the mtrR-coding region that would result in a radical amino acid replacement within the DNA-binding motif of MtrR were found in these strains. When these mutations were transferred into azithromycin-susceptible strain FA19 by transformation, the susceptibility of gonococci to azithromycin was decreased by nearly 10-fold. The mtrCDE-encoded efflux pump system was responsible for this property since insertional inactivation of the mtrC gene resulted in enhanced susceptibility of gonococci to azithromycin. We conclude that the mtrCDE-encoded efflux pump can recognize azithromycin and that the emergence of gonococcal strains with decreased susceptibility to azithromycin can, in part, be explained by mtrR mutations.

Erythromycin-resistant Neisseria gonorrhoeae and oral commensal Neisseria spp. carry known rRNA methylase genes

Two Neisseria gonorrhoeae isolates from Seattle and two isolates from Uruguay were resistant to erythromycin (MIC, 4 to 16 microg/ml) and had reduced susceptibility to azithromycin (MIC, 1 to 4 microg/ml) due to the presence of the self-mobile rRNA methylase gene(s) ermF or ermB and ermF. The two Seattle isolates and one isolate from Uruguay were multiresistant, carrying either the 25.2-MDa tetM-containing plasmid (Seattle) or a beta-lactamase plasmid (Uruguay). Sixteen commensal Neisseria isolates (10 Neisseria perflava-N. sicca, 2 N. flava, and 4 N. mucosa) for which erythromycin MICs were 4 to 16 microg/ml were shown to carry one or more known rRNA methylase genes, including ermB, ermC, and/or ermF. Many of these isolates also were multiresistant and carried the tetM gene. This is the first time that a complete transposon or a complete conjugative transposon carrying an antibiotic resistance gene has been described for the genus Neisseria.

Failure of azithromycin therapy in gonorrhea and discorrelation with laboratory test parameters

BACKGROUND

Azithromycin is efficacious in the treatment of chlamydial genital tract infection but less so in gonorrhea. However, MICs of azithromycin for gonococci from previously reported azithromycin treatment failures were consistently below the 'susceptible' MIC level of 2 mg/L.

GOAL OF THIS STUDY

To examine gonococci not eliminated with 1 g azithromycin therapy to establish treatment outcome/MIC correlates in gonorrhea.

STUDY DESIGN

The MICs and phenotypes of gonococci isolated from five cases of treatment failure after 1 g azithromycin therapy were determined and compared with the MICs of a systematic sample of routine isolates.

RESULTS

Azithromycin MICs of gonococci from five cases of failed 1 g azithromycin treatment were 0.125 or 0.25 mg/L, well within the current 'susceptible' MIC range. None of the isolates were of the mtr phenotype. The MIC90 of a systematic sample of 219 gonococcal isolates was 0.25 mg/L.

CONCLUSION

The antibiotic MIC/treatment outcome correlates that are usually found in gonorrhea do not apply for azithromycin. Current MIC criteria do not accurately define susceptibility or resistance of gonococci to azithromycin and by themselves do not predict the likely outcome of therapy. Pharmacokinetic factors may decrease the predictive value of MIC data.