Quinolone-resistant Neisseria gonorrhoeae isolated in Sydney, Australia, 1991 to 1995

Is gentamicin a viable therapeutic option for treating resistant Neisseria gonorrhoeae in New South Wales?

Abstract

The key issues with Neisseria gonorrhoeae infections, in Australia and elsewhere, are coincident increases in disease rates and in antimicrobial resistance (AMR), although these factors have not been shown to be correlated. Despite advances in diagnosis, control of this disease remains elusive, and incidence in Australia continues to increase. Of the Australian jurisdictions, New South Wales (NSW) has the highest N. gonorrhoeae notifications, and over the five-year period 2015-2019, notifications in NSW have increased above the national average (by 116% versus 85%, respectively). Gonococcal disease control is reliant on effective antibiotic regimens. However, escalating AMR in N. gonorrhoeae is a global health priority, as the collateral injury of untreated infections has substantive impacts on sexual and newborn health. Currently, our first-line therapy for gonorrhoea is also our last line, with no ideal alternative identified. Despite some limitations, gentamicin is licensed and readily available in Australia, and is proposed for treatment of resistant N. gonorrhoeae in national guidelines; however, supportive published microbiological data are lacking. Analysis of gonococcal resistance patterns within Australia for the period 1991-2019, including 35,000 clinical isolates from NSW, illustrates the establishment and spread of population-level resistance to all contemporaneous therapies. An analysis of gentamicin susceptibility on 2,768 N. gonorrhoeae clinical isolates from NSW, for the period 2015-2020, demonstrates that the median minimum inhibitory concentration (MIC) for gentamicin in NSW has remained low, at 4.0 mg/L, and resistance was not detected in any isolate. There has been no demonstration of MIC drift over time (p = 0.91, Kruskal-Wallis test), nor differences in MIC distributions according to patients' sex or site of specimen collection. This is the first large-scale evaluation of gentamicin susceptibility in N. gonorrhoeae in Australia. No gentamicin resistance was detected in clinical isolates, 2015-2020, hence this is likely to be an available treatment option for resistant gonococcal infections in NSW.

Epidemiology of gonorrhoea: a global perspective

Although understanding the local epidemiology of gonorrhoea is critical for local efforts, understanding the multinational epidemiology may support development of national and international prevention and control policies and strategies. In this paper, current epidemiology of gonorrhoea is reviewed through an international lens and with a focus on selected populations. The World Health Organization (WHO) estimates that ~87 million new gonococcal infections occurred among people aged 15-49 years in 2016. Gonorrhoea rates are rising in many countries. Gay, bisexual and other men who have sex with men, racial or ethnic minorities, Indigenous populations and sex workers appear to bear disproportionate burdens of gonorrhoea. International travel can facilitate spread of gonorrhoea, including resistant strains, across international borders. Critical gaps in epidemiological knowledge are highlighted, including data on gonorrhoea among transgender persons and the burden of extragenital gonorrhoea. Even as further data are gathered, action - informed by currently available data - is needed now to confront this growing international threat.

Trends in Antimicrobial Resistance Patterns in Neisseria Gonorrhoeae in Australia and New Zealand: A Meta-analysis and Systematic Review

(1) Background: The widespread development of resistance among Neisseria gonorrhoeae (NG) clinical isolates has been reported by surveillance systems around the world. This meta-analysis estimated the changes in susceptibility patterns among antibiotics under surveillance in Australia and New Zealand. (2) Methods: Articles published in English from 1980-2018, from Australia or New Zealand, that met the selection criteria were included. The meta-analysis was carried out using the R statistical software. (3) Results: In Australia, there has been decreasing susceptibility of gonococcal isolates to selected antimicrobials over time. Azithromycin (Odds Ratio (OR): 0.73; 95% Confidence Interval (CI) 0.64-0.82) and ceftriaxone (OR: 0.69; 95% CI 0.59-0.80) showed decreasing levels of susceptibility each year. Western Australia (OR: 0.76; 95% CI 0.60-0.96) and Victoria (OR: 0.74; 95% CI 0.60-0.90) also had decreasing levels of susceptibility to ceftriaxone over time compared with other states and territories. (4) Conclusions: The results highlight the need for the development of new approaches for managing cases of gonorrhoea. Improved antimicrobial stewardship, enhanced surveillance and contact tracing are needed to identify and respond to changes in antibiotic resistance in a timely manner. Increasing awareness and public health follow-up of cases can help to interrupt the cycle of infection and limit transmission.

Exploring quinolone resistance-determining region in Neisseria gonorrhoeae isolates from across India

Background & objectives:

Antimicrobial resistance in Neisseria gonorrhoeae, the causative agent of gonorrhoea, is a subject of worldwide attention. The present study was undertaken to examine the rates of ciprofloxacin resistance, to correlate mutations in gyrA and parC genes with the level of resistance and to look for a variation in mutation pattern, if any, in isolates from across the country.

Methods:

A total of 113 isolates of N. gonorrhoeae collected from sexually transmitted infection patients in six centres during November 2010 to October 2013 were investigated. Minimum inhibitory concentration (MIC) determination was done by E-test and results interpreted as per Calibrated Dichotomous Sensitivity criteria. DNA sequence analysis of gyrA and parC genes was done.

Results:

Of the 113 isolates, only three (2.6%) were susceptible whereas eight (7.07%) were less susceptible, 32 [28.3%, 95% confidence interval (CI): 20.4-37.6%] resistant (MIC 1-3 µg/ml) and 70 (61.9%, 95% CI: 52.2-70.7%) exhibited high-level resistance (HLR) (MIC ≥4 µg/ml) to ciprofloxacin. A S91F substitution in gyrA gene was demonstrated in all ciprofloxacin non-susceptible isolates. All resistant and HLR isolates had a double mutation in gyrA gene. However, only 5.7 per cent of HLR isolates showed double mutations in parC gene. One isolate (MIC 32 µg/ml) had a previously undescribed G85D substitution in the parC gene.

Interpretation & conclusions:

A S91F substitution in gyrA gene was seen in all non-susceptible isolates of N. gonorrhoeae. It may be used as a marker for ciprofloxacin resistance for molecular surveillance approaches to complement the culture-based methods.

Antibiotic resistance inNeisseria gonorrhoeaeis diminishing available treatment options for gonorrhea: some possible remedies

Gonorrhea is essentially out of control in many settings and high disease rates are coupled with the spread of multiresistant gonococci. Increases in quinolone resistance have followed loss of the penicillins and tetracyclines as useful treatments. Decreasing susceptibility to third-generation cephalosporins is also reported. Over-reliance on antibiotic treatment as a disease control measure in settings with high disease rates and poor control of antibiotic usage is a significant contributor to the antimicrobial resistance reported. Conversely, containment of resistance is more likely to be achieved when combined with disease control principles shown to be effective. However, until a higher priority is given to funding for sexually transmitted diseases, this prospect is unlikely to eventuate and the possibility of untreatable gonorrhea becomes more real.

Cephalosporin Resistance in Neisseria gonorrhoeae

Gonorrhea, a disease of public health importance, not only leads to high incidence of acute infections and complications but also plays a major role in facilitating human immunodeficiency virus (HIV) acquisition and transmission. One of the major public health needs for gonorrhea control is appropriate, effective treatment. However, treatment options for gonorrhea are diminishing as Neisseria gonorrhoeae have developed resistance to several antimicrobial drugs such as sulfonamides, penicillin, tetracyclines and quinolones. Antimicrobial resistance (AMR) surveillance of N. gonorrhoeae helps establish and maintain the efficacy of standard treatment regimens. AMR surveillance should be continuous to reveal the emergence of new resistant strains, monitor the changing patterns of resistance, and be able to update treatment recommendations so as to assist in disease control. Current treatment guidelines recommend the use of single dose injectable or oral cephalosporins. The emergence and spread of cephalosporin resistant and multi drug resistant N. gonorrhoeae strains, represents a worrying trend that requires monitoring and investigation. Routine clinical laboratories need to be vigilant for the detection of such strains such that strategies for control and prevention could be reviewed and revised from time to time. It will be important to elucidate the genetic mechanisms responsible for decreased susceptibility and future resistance. There is also an urgent need for research of safe, alternative anti-gonococcal compounds that can be administered orally and have effective potency, allowing high therapeutic efficacy (greater than 95.0% cure rate).

The use of cephalosporins for gonorrhea: the impending problem of resistance

Gonorrhea remains an important clinical and public health problem throughout the world. Gonococcal infections have historically been diagnosed by Gram stain and culture but are increasingly diagnosed through nucleic acid tests, thereby eliminating the opportunity for antimicrobial susceptibility testing. Gonococcal infections are typically treated with single-dose therapy with an agent found to cure > 95% of cases. Unfortunately, the gonococcus has repeatedly developed resistance to antimicrobials including sulfonamides, penicillin, tetracyclines and fluoroquinolones. This has now left third-generation cephalosporins as the lone class of antimicrobials recommended as first-line therapy for gonorrhea in some regions. However, resistance to oral third-generation cephalosporins has emerged and spread in Asia, Australia and elsewhere. The mechanism of this resistance seems to be associated with a mosaic penicillin binding protein (penA) in addition to other chromosomal mutations previously found to confer resistance to beta-lactam antimicrobials (ponA, mtrR, penB, pilQ). Few good options exist or are in development for treating cephalosporin-resistant isolates, as most have had multidrug resistance. Preventing the spread of resistant isolates will depend on ambitious antimicrobial management programs, strengthening and expanding surveillance networks, and through effective sexually transmitted disease control and prevention.

Sexually transmitted diseases diagnosed among travelers returning from the tropics

OBJECTIVES

Data are lacking on the spectrum of sexually transmitted diseases (STDs) diagnosed in returning travelers.

STUDY DESIGN

All consecutive travelers consulting our tropical unit between November 1, 2002 and October 31, 2003 were included if they presented within 1 month after their return from the tropics, with mucocutaneous signs suggesting STDs.

RESULTS

Forty-nine patients (12 women and 37 men; median age 36.4 y, 35 heterosexuals) were included. Four patients had traveled with their usual sexual partner and 45 patients had casual sex while abroad (31 with locals and 14 with other tourists). The main diagnoses were gonococcal urethritis (n = 18), herpes simplex virus 2 infection (n = 12), urethritis of undetermined origin (n = 9), Chlamydia trachomatis infection (n = 4), primary syphilis (n = 4), and primary human immunodeficiency virus infection (n = 2).

CONCLUSIONS

These results illustrate the broad spectrum of STDs contracted by travelers to the tropics. They suggest the need to also inform travelers of the risks of STD and to promote the use of condoms in case of casual sex while abroad.

High-frequency of quinolone-resistant Neisseria gonorrhoeae in Austria with a common pattern of triple mutations in GyrA and ParC genes

OBJECTIVE

Quinolones have a broad spectrum of antimicrobial activity and are widely used for the treatment of uncomplicated Neisseria gonorrhoeae infections. A dramatic increase in the number of reported N. gonorrhoeae infections as well as quinolone-resistant isolates in Vienna prompted us to investigate the pattern of mutations in these isolates.

GOALS

The goal of this study was to investigate the pattern of mutations in GyrA and ParC genes in quinolone-resistant N. gonorrhoeae clinical isolates in Vienna from 1999 to 2002.

STUDY

The antibiotic susceptibility of N. gonorrhoeae clinical isolates and point mutations of the GyrA and ParC genes of 104 clinical isolates were analyzed.

RESULTS

Quinolone-resistant N. gonorrhoeae isolates increased from 3.9% (3 of 77) in 1999 to 59.4% (120 of 202) in 2002. As expected, none of the 46 N. gonorrhoeae quinolone-sensitive strains showed mutations at these positions of GyrA and ParC genes with the exception of 1 isolate, which had a single mutation at GyrA 91. Unlike what has been previously reported for other geographic areas, 96.6% (56 of 58) of the quinolone-resistant isolates harbored common triple mutations at Gyr 91, 95, and ParC 86. The majority of these isolates (76.8%) belong to the PPNG phenotype.

CONCLUSIONS

Our data indicate that the pattern of mutations in GyrA and ParC subunits of N. gonorrhoeae in Austria differs from that reported from other geographic areas. The differences may either be the result of the difference in bacterial subtypes or various antibiotic regimens used in these regions.

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.

Mutations in the gyrA and parC Genes and in vitro Activities of Fluoroquinolones in 91 Clinical Isolates of Neisseria gonorrhoeae in Japan

BACKGROUND AND OBJECTIVES

Fluoroquinolone resistance in Neisseria gonorrhoeae has been associated with alternations in the quinolone-resistance determining regions in the gyrA and parC genes.

GOAL

The goal of this study was to investigate the correlation between fluoroquinolone minimum inhibitory concentrations (MICs) and mutations in the gyrA and parC genes of 91 N. gonorrhoeae clinical isolates from Japan.

STUDY DESIGN

The MICs of fluoroquinolones ciprofloxacin, levofloxacin, and gatifloxacin for 91 clinical isolates from male gonococcal urethritis in Hyogo or Osaka, Japan, were measured, and the gyrA and parC genes of these isolates were sequenced.

RESULTS

Among 91 isolates tested, over 70% isolates were resistant to ciprofloxacin. We found that 4 mutations (Ser-91-Phe, Ser-91-Ile, Asp-95-Gly in gyrA, and Ser-88-Pro in parC) had significant correlation to MICs of fluoroquinolone (ciprofloxacin, levofloxacin, and gatifloxacin).

CONCLUSION

Some mutations in QRDR had a significant relationship to the fluoroquinolone resistance of N. gonorrhoeae clinical isolates from Japan.

Spatial bridges for the importation of gonorrhea and chlamydial infection

A study of heterosexuals with gonorrhea and/or chlamydial infection in King County, Washington, found that 5.2% of study participants had both local and geographically distant sex partners in the 60 days before diagnosis. Individuals who served as spatial bridges were of higher socioeconomic status and older than other patients.

BACKGROUND

Sexual mixing between distant geographic areas (spatial bridging) is important in the spread of antimicrobial resistance and new sexually transmitted disease pathogens.

GOAL

The goal was to define the extent of sexual mixing between persons with gonorrhea or chlamydial infection in King County, Washington, and persons outside the Seattle area, and to identify characteristics of persons and partnerships associated with spatial bridging.

METHODS

Patients contacted for purposes of partner notification were interviewed regarding demographics, sexual behavior, and the characteristics of their sex partners.

RESULTS

Of 2912 participants, 150 (5.2%) were spatial bridgers. Bridgers were of higher socioeconomic status than nonbridgers and more often reported concurrent partnerships. Over a 39-month period, bridgers and potential bridgers linked King County with 35 states and 13 foreign countries.

CONCLUSION

Spatial bridging could represent an important channel of transmission between geographic areas. These results highlight the need for linkage of prevention efforts across geographic boundaries.

Antimicrobial susceptibility of Neisseria gonorrhoeae strains isolated in Guangzhou, China, 1996-2001

OBJECTIVE

To investigate the in vitro antimicrobial susceptibility and resistant trends of Neisseria gonorrhoeae strains isolated in Guangzhou, from 1996 to 2001.

METHODS

The agar dilution method was used to determine the minimum inhibitory concentrations (MICs) to four antimicrobials, penicillin G, ciprofloxacin, ceftriaxone, and spectinomycin. The resistance of all strains to four antibiotics was interpreted according to criteria used in the project of surveillance of gonococcal antibiotic susceptibility in the WHO Western Pacific Region. Penicillinase producing N gonorrhoeae (PPNG) was analysed by the paper acidometric method.

RESULTS

793 consecutive N gonorrhoeae isolates collected in Guangzhou were studied from 1996 to 2001. A total of 55 strains of PPNG were identified and the prevalence rapidly spread from 2% to 21.8%. Of the four antibiotics examined, ceftriaxone and spectinomycin appeared to be the most effective agents although two spectinomycin resistant strains were isolated in 1996. Their MIC(50), MIC(90), and geometric mean MIC (MICmean) were all between the sensitive ranges of the interpretative criteria and remained stable over the years. However, resistance increased continuously to penicillin G and dramatically to ciprofloxacin. In 1996-2001, MIC(50), MIC(90), and MICmean of penicillin G increased from 1 micro g/ml to 2 micro g/ml, 4 micro g/ml to 32 micro g/ml, and 0.68 micro g/ml to 2.35 micro g/ml, respectively; those of ciprofloxacin steeply increased from 0.12 micro g/ml to 4 micro g/ml, 2 micro g/ml to 32 micro g/ml, and 0.14 micro g/ml to 2.62 micro g/ml in 1996-9, respectively, and then declined slightly in 2000-1. The prevalence of resistant isolates spread from 57.2% to 81.8% for penicillin G and from 17.6% to 72.7% for ciprofloxacin over the 6 years.

CONCLUSION

Resistance to penicillin and ciprofloxacin increased greatly during 1996-2001. Ceftriaxone and spectinomycin should be used as the first line agents in treating gonorrhoea. It is of great importance to continuously survey the susceptibilities of N gonorrhoeae to antibiotics in controlling the spread of gonococcal infections.

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.

Lower dose of ciprofloxacin is adequate for the treatment of Neisseria gonorrhoeae in KwaZulu Natal, South Africa

The response of male gonococcal urethritis to a single 250 mg dose of ciprofloxacin versus 500 mg was studied. Both regimens were given in combination with doxycycline in the context of the local syndromic management protocol. There was no significant difference in response between the regimens, inclusive/exclusive of tetracycline susceptible isolates. One patient in the 250 mg arm failed to respond clinically but was microbiologically cured and four patients in the 500 mg arm failed microbiologically but responded clinically. All four isolates had ciprofloxacin MICs </=0.007 mg/l.

Reduced susceptibility to azithromycin and high percentages of penicillin and tetracycline resistance in Neisseria gonorrhoeae isolates from Manaus, Brazil, 1998

BACKGROUND

The identification of Neisseria gonorrhoeae isolates resistant to antimicrobial agents currently recommended for the treatment of gonococcal infections continues to escalate globally. Thus, in some areas, resistance to fluoroquinolone drugs is commonplace; several reports document resistance to third-generation cephalosporins, and the sporadic isolation of spectinomycin-resistant isolates continues unabated. Gonococcal resistance to azithromycin, an antibiotic used for the primary treatment of gonococcal infections in some Latin American countries, also has been described. Because the prevalence of resistant isolates is insufficiently documented in many areas of Latin America, the efficacy of locally recommended therapies for gonococcal infections is often unknown.

GOAL

To determine the antimicrobial susceptibility and strain types of N gonorrhoeae isolates collected in Manaus, Brazil. These data will establish antimicrobial susceptibility baseline data for the region as a reference point for future surveillance.

STUDY DESIGN

Consecutive N gonorrhoeae isolates from urethral and endocervical specimens were collected and examined for identity, antimicrobial susceptibility, and strain type (plasmid content, tetM type, auxotype, and serovar).

RESULTS

Most of the isolates (65/81; 85.2%) were resistant to tetracycline, penicillin, or both, with the majority (n = 62) carrying plasmid-mediated resistance to tetracycline (tetracycline-resistant N gonorrhoeae [TRNG]). All of the TRNG contained the Dutch-type tetM plasmid, and 18 were A/S class NR/IA-02. Penicillinase-producing N gonorrhoeae comprised 8.2% (7/81) of the isolates. Of these seven isolates, four also were TRNG, and two carried chromosomal resistance to tetracycline. The isolates were susceptible to ciprofloxacin, spectinomycin, and ceftriaxone. However, 23 isolates were characterized by reduced susceptibility to azithromycin (MIC, 0.25-0.5 microg/ml), and one isolate had reduced susceptibility to ciprofloxacin (MIC, 0.25 microg/ml).

CONCLUSIONS

This study supports the continued use of third-generation cephalosporins, spectinomycin, and fluoroquinolone drugs for the primary treatment of gonococcal infections in Manaus. The occurrence of isolates with reduced susceptibility to azithromycin and ciprofloxacin underscores the importance of ongoing antimicrobial susceptibility monitoring to support decisions regarding appropriate drugs for the treatment of gonococcal infections.

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.

Sexually transmitted diseases in travelers

Prevention of sexually transmitted diseases (STDs) is a low priority among travel clinic services, despite increasing evidence that travelers have an increased risk of acquiring such infections. A proportion of 5%-50% of short-term travelers engage in casual sex while abroad, and this rate is even higher among long-term travelers. Few publications are available on STD preventive interventions among travelers. Education and counseling are recognized as key components of risk reduction. New efforts should be put forth with regard to identifying effective tools to promote safer sexual behaviors and to reduce the spread of infection by promoting condom use. Travelers at increased risk should be identified for targeted interventions; research to validate proposed markers of increased risk is prospectively needed. Hepatitis B infection is the only STD that is preventable by vaccination. The feasibility and cost-effectiveness of STD screening in travelers after exposure is a virtually unexplored field, though it may represent an important component of STD control strategies in developed countries.

Correlation of in vitro susceptibilities to newer quinolones of naturally occurring quinolone-resistant Neisseria gonorrhoeae strains with changes in GyrA and ParC

The in vitro activities of ciprofloxacin, trovafloxacin, moxifloxacin, and grepafloxacin against 174 strains of Neisseria gonorrhoeae isolated in Sydney, Australia, were determined. The strains included 84 quinolone-less-sensitive and -resistant N. gonorrhoeae (QRNG) strains for which ciprofloxacin MICs were in the range of 0.12 to 16 microg/ml. The QRNG included strains isolated from patients whose infections were acquired in a number of countries, mostly in Southeast Asia. The gyrA and parC quinolone resistance-determining regions (QRDR) of 18 selected QRNG strains were sequenced, and the amino acid mutations observed were related to the MICs obtained. The activities of moxifloxacin and grepafloxacin against QRNG were comparable to that of ciprofloxacin. Trovafloxacin was more active than the other quinolones against some but not all of the QRNG strains. Increments in ciprofloxacin resistance occurred in a step-wise manner with point mutations initiated in gyrA resulting in amino acid alterations Ser91-to-Phe, Ser91-to-Tyr, Asp95-to-Gly, and Asp95-to-Asn. Single gyrA changes correlated with ciprofloxacin MICs in the range 0.12 to 1 microg/ml. The Ser91 changes in GyrA were associated with higher MICs and further QRDR changes. QRNG strains for which ciprofloxacin MICs were greater than 1 microg/ml had both gyrA and parC QRDR point mutations. ParC alterations were seen in these isolates only in the presence of GyrA changes and comprised amino acid changes Asp86-to-Asn, Ser87-to-Asn, Ser87-to-Arg, Ser88-to-Pro, Glu91-to-Lys, and Glu91-to-Gln. QRNG strains for which MICs were in the higher ranges had double GyrA mutations, but again only with accompanying ParC alterations. Not only did the nature and combination of GyrA and ParC changes influence the incremental increases in ciprofloxacin MICs, but they seemingly also altered the differential activity of trovafloxacin. Our findings suggest that the newer quinolones of the type examined are unlikely to be useful replacements for ciprofloxacin in the treatment of gonorrhea, particularly where ciprofloxacin MICs are high or where resistance is widespread.

Molecular basis of high-level ciprofloxacin resistance in Neisseria gonorrhoeae strains isolated in Denmark from 1995 to 1998

In Denmark surveillance of the in vitro susceptibility to ciprofloxacin of Neisseria gonorrhoeae was established in 1990. The proportion of N. gonorrhoeae strains with decreased susceptibility or resistance to ciprofloxacin (MIC >/= 0.06 microg/ml) was low (0.3 to 2.3%) up to 1995. Between 1995 and 1998 the rate of less-susceptible and resistant strains rose from 6.9 to 13.2%. Among ciprofloxacin-resistant strains (MIC >/= 1 microg/ml), 81% were highly resistant (MIC >/= 4 microg/ml). Thirty-five N. gonorrhoeae strains (40 isolates) for which ciprofloxacin MICs were 4 to 32 microg/ml were investigated for the frequency and patterns of mutations within the gyrA and parC genes. The quinolone resistance-determining regions of the gyrA and parC genes were amplified by PCR, and the amplicons were directly sequenced. Alterations at Ser-91 and Asp-95 in GyrA and a single or double alteration in ParC were identified in 32 strains (91%). Ser-91-to-Phe and Asp-95-to-Gly alterations in GyrA were detected in 28 strains (80%). The most common ParC alteration, Asp-86 to Asn, was found in 19 strains (54%). The strains were analyzed for genetic relationship by pulsed-field gel electrophoresis (PFGE). The analysis showed that nine strains with the same mutation pattern in the gyrA and parC genes, originating from different geographical areas over 3 years, had the same PFGE patterns after SpeI as well as NheI digestion (only one strain with one band difference in the NheI pattern), suggesting that a resistant clone had spread worldwide. The results from this study strongly suggest that double gyrA mutations plus a parC mutation(s) play an important role in the development of high-level fluoroquinolone resistance in N. gonorrhoeae.

In vitro selection of fluoroquinolone-resistant Neisseria gonorrhoeae harboring alterations in DNA gyrase and topoisomerase IV

PURPOSE

We attempted to select increasingly fluoroquinolone-resistant strains of Neisseria gonorrhoeae in vitro and to assess whether selected mutants harbored alterations in the GyrA subunit of DNA gyrase and the ParC subunit of DNA topoisomerase IV, which were analogous to those in fluoroquinolone-resistant clinical isolates.

MATERIALS AND METHODS

A fluoroquinolone-susceptible strain was exposed to norfloxacin in vitro. Selected mutants were sequentially exposed to norfloxacin, and this procedure was repeated. For 11 mutants, minimum inhibitory concentrations (MICs) of antimicrobial agents were determined, and mutations in the region corresponding to the quinolone resistance-determining region (QRDR) of the Escherichia coli gyrA gene and the analogous region of the parC gene were analyzed.

RESULTS

Mutants obtained in one step exhibited significantly increased MICs of norfloxacin, ofloxacin and ciprofloxacin and had a single amino acid change in GyrA. Two-step mutants exhibited significantly higher norfloxacin MICs. Three of four two-step selected strains had single amino acid changes in both GyrA and ParC. Three-step mutants exhibited further increases in fluoroquinolone MICs and were assigned to the ciprofloxacin-resistant category. Two had a double amino acid change in GyrA, and one had a double GyrA change and a single amino acid change in ParC.

CONCLUSION

We selected fluoroquinolone-resistant strains that carried GyrA and ParC alterations analogous to those in clinical isolates. The serial accumulation of changes in the QRDR of GyrA and the analogous region of ParC was associated with a stepwise increase in fluoroquinolone resistance, although the development of additional alterations in other regions of GyrA and ParC or other mechanisms of fluoroquinolone resistance also might contribute to the enhancement in fluoroquinolone resistance. The clinical emergence of fluoroquinolone-resistant strains may be due to in-vivo stepwise selection of strains with genetic alterations in GyrA and ParC, as observed here in the in-vitro selection of fluoroquinolone-resistant mutants.

Cefaclor into the millennium

We review the discovery and development of the cephalosporins and subsequently cefaclor. Cefaclor is active against a wide range of commonly encountered bacterial pathogens, acting by inhibiting cell wall synthesis. Its in vitro activity compares favourably with other beta-lactam antibiotics. Its pharmacokinetic properties indicate that an 8-hourly dosing schedule is appropriate. In addition a delayed release formulation allowing twice daily dosage has been developed. The efficacy of both formulations of cefaclor has been verified by many clinical trials. Cefaclor has been widely used in infections of the respiratory tract (including otitis media), urinary tract and soft tissues. The results of therapy are summarized. The low incidence of adverse events is highlighted and the beneficial influence of this on compliance is described. Finally, the pharmaco-economics of cefaclor are considered.

Neisseria gonorrhoeae in Newcastle upon Tyne 1995-1997: increase in ciprofloxacin resistance

Fluoroquinolones and third generation cephalosporins are the most effective antimicrobial agents for the treatment of gonorrhoea. However, clinically significant resistance to fluoroquinolones in Neisseria gonorrhoeae has been reported worldwide including Britain. The aim of this analysis was to study the factors relating to ciprofloxacin resistance and treatment failure. A total of 201 patients attending the Newcastle Genitourinary Medicine (GUM) clinic from 1995-1997 who were diagnosed with culture positive gonorrhoea was analysed. Treatment failure rates for ciprofloxacin were determined and the minimum inhibitory concentration (MIC) was measured for all cases of treatment failure. The case notes of all patients who had strains with MICs of ciprofloxacin in the resistant range (>0.05 microg/ml) were reviewed to determine the clinical outcome. The ciprofloxacin resistance with treatment failure was seen in 5% (8/160). All the 8 cases of treatment failure were heterosexual and had isolates resistant to penicillin and 4 cases (50%) were also resistant to tetracycline. All were sensitive to spectinomycin and ceftriaxone. Most of the cases probably acquired their infection from the Far East. As ciprofloxacin resistance seems to be associated with overseas exposure, changes in the standard treatment of gonorrhoea are not justified but consideration should be given to appropriate alternatives when the infection may have arisen from where such resistant strains are endemic. Monitoring fluoroquinolone resistance is now essential for ensuring adequate treatment of infections with resistant strains and for maximizing the time of usage of fluoroquinolones to treat gonorrhoea.

Antimicrobial resistance in Neisseria gonorrhoeae

Despite a declining incidence of gonorrhea in much of the industrialized world, antimicrobial resistance continues to present a challenge to the treatment of gonococcal infections. Although no clinically significant resistance to the broad-spectrum cephalosporins has been identified, fluoroquinolone-resistant gonococcal strains are now prevalent in Australia and much of the Far East. Ongoing surveillance for antimicrobial resistance is crucial to obtain the information needed to choose effective empiric therapies for gonorrhea.

Drift in susceptibility of Neisseria gonorrhoeae to ciprofloxacin and emergence of therapeutic failure

Ciprofloxacin, 500 mg, was introduced as the first-line therapy for gonorrhea at St. Mary's Hospital, London, in 1989, when a surveillance program was initiated to detect the emergence of resistance. Isolates of Neisseria gonorrhoeae from consecutive patients attending the Jefferiss Wing, Genitourinary Medicine Clinic at St. Mary's Hospital, between 1989 and 1997 have been tested for susceptibility to ciprofloxacin by using an agar dilution breakpoint technique. Isolates considered potentially resistant (MIC, >0.12 microg/ml) were further characterized by determination of the MICs of ciprofloxacin, nalidixic acid, and penicillin, auxotyped and serotyped, and screened for mutations in the DNA gyrase gene, gyrA, and the topoisomerase IV gene, parC. A total of 4,875 isolates were tested. While the majority of isolates were highly susceptible (MIC, 0.12 microg/ml); all of these belonged to serogroup B, and NR/IB-1 was the most common auxotype/serovar class. The infections in 14 of the 18 patients were known to be acquired abroad, and 5 were known to result in therapeutic failure. The surveillance program has established that ciprofloxacin is still a highly effective antibiotic against N. gonorrhoeae in this population. However, it has identified a drift in susceptibility which may have resulted from increased usage of ciprofloxacin. High-level resistance has now emerged, although treatment failure is still uncommon.

Quinolone-resistant Neisseria gonorrhoeae: the beginning of the end? Report of quinolone-resistant isolates and surveillance in the southwestern United States, 1989 to 1997

BACKGROUND

Fluoroquinolones are one of the most widely used treatments for gonorrhoeae. Changes in the susceptibility of Neisseria gonorrhoeae to these agents may threaten their use.

GOAL OF THIS STUDY

To report several resistant strains (>1 mcg/ml) isolated in the western United States and to evaluate the prevalence of strains with reduced susceptibility (ofloxacin 0.25 mcg/ml, ciprofloxacin 0.06 mcg/ml).

STUDY DESIGN

The microbiology and epidemiology of three resistant strains were characterized and 12,761 other strains were evaluated for fluoroquinolone susceptibility as part of the Gonococcal Isolate Surveillance Project of the Centers for Disease Control and Prevention.

RESULTS

Fluoroquinolone-resistant strains may appear sporadically. The prevalence of isolates with reduced susceptibility to fluoroquinolones remains low in the Southwest region of the United States.

CONCLUSIONS

Continued active surveillance is needed to detect and control the spread of quinolone-resistant Neisseria gonorrhoeae.

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.

Clinical evaluation of ceftibuten in gonorrhea. A pilot study in Hong Kong

BACKGROUND

The escalating rates of gonococcal resistance to quinolone in Hong Kong have prompted a search for an alternative first-line antimicrobial agent for use in treating uncomplicated gonococcal urethritis. Ceftibuten is an orally active third-generation cephalosporin with potent in vitro activity against Neisseria gonorrhoeae. Its pharmacokinetic properties allow single-dose administration.

OBJECTIVE

To evaluate the efficacy, safety, and tolerability of ceftibuten in the treatment of uncomplicated gonorrhea in men.

STUDY DESIGN

Ceftibuten was evaluated in an open-label, noncomparative, multicenter study. Eligible men with uncomplicated gonococcal urethritis were treated with a single 400-mg oral dose of ceftibuten and reassessed 1 week and 3 weeks after treatment. The main outcome measures were the isolation of N. gonorrhoeae, patient-reported side effects, and other safety parameters (e.g., blood counts and renal and hepatic function tests).

RESULTS

One hundred twenty-five men were enrolled in the study. The overall cure rate was 98.2% (110 of 112 evaluable patients). Adverse events, which occurred in 4.5% of patients, were all mild, well tolerated, and of short duration. No significant changes in laboratory test results were noted. Of the 125 isolates, 4.8% were -lactamase positive. Susceptibility to ofloxacin was found to be low in 59.2% of isolates (MIC 0.1 to < 1g/mL) and 25.6% of isolates were resistant (MIC1g/mL) to ofloxacin.

CONCLUSIONS

A single 400-mg oral dose of ceftibuten is highly effective and well tolerated in the treatment of uncomplicated gonococcal urethritis in men.

Continuing evolution of the pattern of quinolone resistance in Neisseria gonorrhoeae isolated in Sydney, Australia

BACKGROUND AND OBJECTIVES

Multiple phenotypes of quinolone-resistant Neisseria gonorrhoeae isolated in Sydney since 1984 originated in Asia and increased in number and level of resistance in 1995.

GOAL

To study the origins, characteristics, and infection pattern of quinolone-resistant Neisseria gonorrhoeae in Sydney from 1995 to 1997 and to compare these results with prior findings.

STUDY DESIGN

Quinolone minimal inhibitory concentrations, phenotype, and geographic source of quinolone-resistant Neisseria gonorrhoeae isolated in Sydney from 1995 to 1997 were analyzed.

RESULTS

Two hundred nineteen episodes of infection with quinolone-resistant Neisseria gonorrhoeae from 2,236 gonococcal isolates occurred during 1995 through 1997. The rate of isolation of quinolone-resistant Neisseria gonorrhoeae increased significantly at the end of 1996 and was maintained through 1997. The increase resulted from sustained domestic transmission of a limited number of phenotypes in heterosexual patients.

CONCLUSION

The pattern of isolation of quinolone-resistant Neisseria gonorrhoeae in Sydney changed from the sporadic isolation of multiple phenotypes of imported quinolone-resistant Neisseria gonorrhoeae to a higher rate of endemic disease caused by a few subtypes. Alterations in antibiotic treatment regimens in the affected patient group were required.

Cefaclor, an alternative to third generation cephalosporins for the treatment of gonococcal urethritis in the developing world?

OBJECTIVE

To reassess the in vivo and in vitro efficacy of cefaclor for the treatment of uncomplicated gonococcal infection.

DESIGN

Open clinical trail conducted in South Africa among consecutive male patients with symptoms and signs of uncomplicated urethritis and laboratory evidence of gonorrhoea.

METHODS

Patients were treated with 3 g of cefaclor plus 1 g probenecid as a single dose. Urethral specimens were cultured for Neisseria gonorrhoeae at the initial visit and at follow up. Patients were considered cured if follow up cultures were negative. Treatment was considered to have failed in the patients infected with identical gonococcal strains at the initial and at the control visit. Those with evidence of infection at the follow up visit were administered 400 mg of ofloxacin and doxycycline 100 mg twice daily for 7 days. Minimal inhibitory concentrations (MICs) of cefaclor were determined by an agar dilution technique on the gonococcal isolates from the study subjects. The results were compared with those of isolates from three other African countries.

RESULTS

Of 155 patients evaluated, 151 were cured (97%). Thirty per cent of the patients complained of adverse effects, mainly gastrointestinal. Even though MICs for the isolates from the three other African countries were significantly higher than those for the isolates from the study, none was considered resistant to cefaclor in vitro. MICs were markedly influenced by the type of test medium used.

CONCLUSION

The trial demonstrated the efficacy of a single oral dose of cefaclor with probenecid for the treatment of uncomplicated gonococcal urethritis in South Africa. Its potential as an alternative therapy to third generation cephalosporins deserves to be further investigated.

Surveillance of antibiotic susceptibility of Neisseria gonorrhoeae in the WHO western Pacific region 1992-4. WHO Western Pacific Region Gonococcal Antimicrobial Surveillance Programme

OBJECTIVE

To describe the establishment and outcomes of a regional programme of continuing long term surveillance of antibiotic susceptibility of Neisseria gonorrhoeae over the period 1992-4.

METHODS

Laboratories in 17 countries in the WHO Western Pacific Region participated in a continuing programme of surveillance of the susceptibility of gonococci to an agreed group of antibiotics over 3 years. Established techniques were used and these included quality control and proficiency testing systems.

RESULTS

About 20,000 gonococci were examined over a 3 year period. Resistance to the penicillins through beta lactamase production or chromosomal mechanisms was widespread, with further changes evident over the 3 years. Spectinomycin resistance was infrequently encountered but high level tetracycline resistance was present in most participating centres, with some having high proportions of tetracycline resistant organisms. Quinolone resistance increased and became widespread throughout the region in the 3 years, ultimately involving all but one centre. Both the number and minimum inhibitory concentrations of quinolone resistant isolates increased markedly.

CONCLUSIONS

Patterns of gonococcal resistance to antibiotics continue to evolve, at times rapidly, and have the potential for wide and rapid dissemination. Regional surveillance programmes can be developed by using and expanding existing resources. Data thus derived were applied to the development of appropriate treatment regimens in the region, and emphasised further the need for a global expansion of the programme of integrated surveillance of gonococcal resistance.

Fluoroquinolone resistance in Neisseria gonorrhoeae

Fluoroquinolones and broad-spectrum cephalosporins are the most effective antimicrobial agents for the treatment of gonorrhea. However, clinically significant resistance to fluoroquinolones has emerged in Neisseria gonorrhoeae. Fluoroquinolone-resistant strains account for approximately 10% of all gonococcal strains in Hong Kong and the Republic of the Philippines. As many as 50% of strains from some Far Eastern countries exhibit decreased susceptibility (intermediate resistance) to fluoroquinolones. Strains with intermediate resistance and clinically significant resistance are being isolated sporadically in North America, where resistant strains have been associated with an outbreak and with failure of infections to respond to treatment with doses of ciprofloxacin and ofloxacin recommended by the Centers for Disease Control and Prevention; strains exhibiting decreased susceptibility to these agents are endemic in at least one metropolitan area. Monitoring for fluoroquinolone resistance is now critical for ensuring adequate treatment of infections with resistant strains and for maximizing the time during which fluoroquinolones may be used to treat gonorrhea.