Proposed criteria for interpretation of susceptibilities of strains of Neisseria gonorrhoeae to ciprofloxacin, ofloxacin, enoxacin, lomefloxacin, and norfloxacin

Efficacy of Ciprofloxacin for Treatment of Cholera Associated with Diminished Susceptibility to Ciprofloxacin to Vibrio cholerae O1

Objective

We identified a poor clinical response to treatment of cholera with a single 1 g dose of ciprofloxacin, a standard treatment for cholera.

Methods

To determine reasons for the poor response and better therapeutic approaches we examined the minimal inhibitor concentration (MIC, n = 275) and disc-diffusion zone sizes (n = 205) for ciprofloxacin and nalidixic acid of V. cholerae O1 strains isolated in Bangladesh from 1994 to 2012, and reexamined data from 161patients infected with Vibrio cholerae O1 recruited in four clinical trials who received single- or multiple-dose ciprofloxacin for treatment of cholera and compared their clinical response to the V. cholerae O1 susceptibility.

Results

Although all 275 isolates of V. cholerae O1 remained susceptible to ciprofloxacin using standard MIC and disc-diffusion thresholds, the MIC⁹⁰ to ciprofloxacin increased from 0.010 in 1994 to 0.475 μgm/ml in 2012. Isolates became frankly resistant to nalidixic with the MIC⁹⁰ increasing from 21 μgm/ml in 1994 to >256 μgm/ml and 166 of 205 isolates from 1994 to 2005 being frankly resistant using disc-diffusion testing. Isolates resistant to nalidixic acid by disc-diffusion testing had a median ciprofloxacin MIC of 0.190 μgm/ml (10^th-90^th centiles 0.022 to 0.380); nalidixic acid-susceptible isolates had a median ciprofloxacin MIC of 0.002 (0.002 to 0.012).The rate of clinical success with single-dose ciprofloxacin treatment for nalidixic acid-susceptible strains was 94% (61 of 65 patients) and bacteriologic success 97% (63/65) compared to 18% (12/67) and 8% (5/67) respectively with nalidixic acid-resistant strains (P<0.001 for both comparisons). Multiple-dose treatment with ciprofloxacin had 86% and 100% clinical and bacteriologic success rates respectively in patients infected with nalidixic acid-susceptible strains of V. cholerae O1 compared to clinical success 67% and bacteriologic success 60% with nalidixic acid-resistant strains.

Conclusions

Single-dose ciprofloxacin is not effective for treating cholera caused by V. cholerae O1 with diminished susceptibility to ciprofloxacin, and nalidixic acid disc-diffusion testing effectively screens for such isolates.

Olive oil based novel thermo-reversible emulsion hydrogels for controlled delivery applications

Gels have been considered as a popular mode of delivering medicament for the treatment of sexually transmitted diseases (STDs) (e.g. human immunodeficiency virus, bacterial vaginosis, epididymitis, human papillomavirus infection and condylomata acuminata etc.). The present study discusses the development of novel olive oil based emulsion hydrogels (EHs) using sorbitan monopalmitate as the structuring agent. The developed EHs may be tried as drug delivery vehicle for the treatment of STDs. The formation of EHs was confirmed by fluorescence and confocal microscopy. FTIR studies suggested intermolecular hydrogen bonding amongst the components of the EHs. X-ray diffraction study suggested the amorphous nature of the EHs. The developed EHs have shown non-Newtonian flow behavior. The EHs were found to be biocompatible. The formulations were able to effectively deliver two model antimicrobial drugs (e.g. ciprofloxacin and metronidazole), commonly used in the treatment of the STDs.

Emergence of fluoroquinolone resistance in Neisseria gonorrhoeae isolates from four clinics in three regions of Kenya

We have recently reported high levels of fluoroquinolone resistance in a single region of Kenya. In this article, we report high prevalence of fluoroquinolone resistance (53.2%) in Neisseria gonorrhoeae isolates from 4 clinics in 3 additional regions of Kenya. These findings highlight the need to change first-line treatment in these settings and the need to evaluate empirical management guidelines for treatment of gonococcal infection in Kenya.

Impact of fluoroquinolone resistance mutations on gonococcal fitness and in vivo selection for compensatory mutations

BACKGROUND

Quinolone-resistant Neisseria gonorrhoeae (QRNG) arise from mutations in gyrA (intermediate resistance) or gyrA and parC (resistance). Here we tested the consequence of commonly isolated gyrA(91/95) and parC86 mutations on gonococcal fitness.

METHODS

Mutant gyrA(91/95) and parC86 alleles were introduced into wild-type gonococci or an isogenic mutant that is resistant to macrolides due to an mtrR(-79) mutation. Wild-type and mutant bacteria were compared for growth in vitro and in competitive murine infection.

RESULTS

In vitro growth was reduced with increasing numbers of mutations. Interestingly, the gyrA(91/95) mutation conferred an in vivo fitness benefit to wild-type and mtrR(-79) mutant gonococci. The gyrA(91/95), parC86 mutant, in contrast, showed a slight fitness defect in vivo, and the gyrA(91/95), parC86, mtrR(-79) mutant was markedly less fit relative to the parent strains. A ciprofloxacin-resistant (Cip(R)) mutant was selected during infection with the gyrA(91/95), parC86, mtrR(-79) mutant in which the mtrR(-79) mutation was repaired and the gyrA(91) mutation was altered. This in vivo-selected mutant grew as well as the wild-type strain in vitro.

CONCLUSIONS

gyrA(91/95) mutations may contribute to the spread of QRNG. Further acquisition of a parC86 mutation abrogates this fitness advantage; however, compensatory mutations can occur that restore in vivo fitness and maintain Cip(R).

An insight into the drug resistance profile & mechanism of drug resistance in Neisseria gonorrhoeae

Among the aetiological agents of treatable sexually transmitted diseases (STDs), Neissseria gonorrhoeae is considered to be most important because of emerging antibiotic resistant strains that compromise the effectiveness of treatment of the disease - gonorrhoea. In most of the developing countries, treatment of gonorrhoea relies mainly on syndromic management rather than the aetiological based therapy. Gonococcal infections are usually treated with single-dose therapy with an agent found to cure > 95 per cent of cases. Unfortunately during the last few decades, N. gonorrhoeae has developed resistance not only to less expensive antimicrobials such as sulphonamides, penicillin and tetracyclines but also to fluoroquinolones. The resistance trend of N. gonorrhoeae towards these antimicrobials can be categorised into pre-quinolone, quinolone and post-quinolone era. Among the antimicrobials available so far, only the third-generation cephalosporins could be safely recommended as first-line therapy for gonorrhoea globally. However, resistance to oral third-generation cephalosporins has also started emerging in some countries. Therefore, it has become imperative to initiate sustained national and international efforts to reduce infection and misuse of antibiotics so as to prevent further emergence and spread of antimicrobial resistance. It is necessary not only to monitor drug resistance and optimise treatment regimens, but also to gain insight into how gonococcus develops drug resistance. Knowledge of mechanism of resistance would help us to devise methods to prevent the occurrence of drug resistance against existing and new drugs. Such studies could also help in finding out new drug targets in N. gonorrhoeae and also a possibility of identification of new drugs for treating gonorrhoea.

Strain typing and antimicrobial resistance of fluoroquinolone-resistant Neisseria gonorrhoeae causing a California infection outbreak

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

The potent antibacterial activity of Sitafloxacin against fluoroquinolone-resistant clinical isolates of Vibrio cholerae O1

The in vitro antibacterial activity of sitafloxacin using clinical isolates of Vibrio cholerae O1 was compared to other fluoroquinolones: ciprofloxacin, ofloxacin, sparfloxacin and levofloxacin. Against fluoroquinolone-resistant O1 strains, sitafloxacin was 4- to 16-fold more effective than other fluoroquinolones at MIC(90*). Against fluoroquinolone-susceptible O1 strains, the MIC(90) of sitafloxacin was 2- to 4-fold lower than other fluoroquinolones. This suggests sitafloxacin can be used in the treatment of infections caused by V. cholerae O1 strains including the fluoroquinolone-resistant strains.

Real-time PCR assay for detection of quinolone-resistant Neisseria gonorrhoeae in urine samples

A need exists for the development of applicable surveillance tools to detect fluoroquinolone-resistant Neisseria gonorrhoeae (QRNG) in urine samples. We describe here a real-time PCR assay for detecting mutations in the Ser91 codon of the gyrA gene of N. gonorrhoeae in urine specimens. We tested 96 urine samples collected along with Gonorrhea Isolate Surveillance Project (GISP) urethral swab samples and compared the results with matched MICs of ciprofloxacin, as reported by the regional GISP laboratory. We then tested 100 urine specimens, known to be gonorrhea positive by nucleic acid amplification testing, provided by females to challenge the real-time PCR assay with urine specimens containing potentially less target DNA content than specimens from symptomatic males. With an MIC threshold of 0.125 mug of ciprofloxacin/ml, our assay correctly identified resistance in 41 of 44 (93.2%; 95% confidence interval [CI] = 81.3 to 98.6%) corresponding resistant culture specimens and correctly identified 51 of 51 (100%; 95% CI = 93.0 to 100%) susceptible specimens. One specimen did not amplify. The assay successfully amplified the gyrA amplicon and determined a susceptibility genotype in 72 of 100 (72%) urine specimens collected from female patients. We developed an assay for detecting QRNG in urine specimens that correlated well with MIC results of cultured specimens and had moderate sensitivity with urine specimens. This methodology might fulfill the need for a QRNG detection system for urine specimens, a useful characteristic in the age of nucleic acid amplification testing for gonococcal infection.

Fluoroquinolone-Resistant Neisseria gonorrhoeae in Bali, Indonesia: 2004

OBJECTIVES

In the mid-1990s, fluoroquinolones were introduced in Indonesia for the management of gonorrhea and are now part of the national recommended treatment guidelines. We recently documented introduction of ciprofloxacin-resistant Neisseria gonorrhoeae strains in female sex workers (FSWs) in Timika, Indonesia, 5 years after treating gonococcal cervicitis with ciprofloxacin and periodically monitoring antimicrobial susceptibility of isolates. To assess the importance of this observation, we determined antimicrobial susceptibilities and strain types of N. gonorrhoeae isolates from FSWs seen in a sexually transmitted infection (STI) clinic in Denpasar, Bali, Indonesia.

GOAL

The goal of this study was to determine antimicrobial susceptibilities and strain types among N. gonorrhoeae isolated from FSWs in Denpasar, Bali.

STUDY DESIGN

FSWs in Denpasar were screened for N. gonorrhoeae by standard culture. Endocervical isolates were frozen in Microbank tubes and sent to the University of California at San Francisco on dry ice. Antimicrobial susceptibility testing using a Clinical Laboratory Standards Institute-recommended agar dilution method was performed at the Centers for Disease Control and Prevention. Isolates were characterized by beta-lactamase production, antimicrobial resistance phenotypes, and auxotype/serovar class.

RESULTS

One hundred forty-seven N. gonorrhoeae isolates were characterized. All isolates were highly resistant to tetracycline (minimum inhibitory concentration, >or=16.0 microg/mL): 117 (79.1%) were beta-lactamase-positive (PP-TR), 3 (2.0%) exhibited chromosomally mediated resistance to penicillin (PenR-TRNG), and 27 (18.2%) were susceptible to penicillin (TRNG). All isolates were susceptible to ceftriaxone, cefixime, and spectinomycin; lack of interpretive criteria do not allow interpretation of susceptibilities of cefoxitin, cefpodoxime, or azithromycin. Fifty-nine (40.1%) isolates were ciprofloxacin-resistant; 35 (59.3%) of the ciprofloxacin-resistant isolates exhibited high-level resistance to ciprofloxacin (Cip-HLR; minimum inhibitory concentration, >or=4.0 microg/mL of ciprofloxacin). Three (2.0%) isolates were intermediate to ciprofloxacin. Twenty-two strain types were identified among these isolates; small clusters were identified with 3 strain types.

CONCLUSIONS

N. gonorrhoeae isolates from FSWs in Denpasar were resistant to penicillin and tetracycline; 40.1% of the isolates were fluoroquinolone-resistant. With gonorrhea prevalence of 35% at this clinic (by nucleic acid amplified tests), ongoing surveillance for antimicrobial resistance will be needed to appropriately choose treatment for infections caused by these resistant organisms.

Single-dose azithromycin for the treatment of cholera in adults

BACKGROUND

Single-dose azithromycin is effective in the treatment of severe cholera in children, but its effectiveness in adults has not been evaluated.

METHODS

We conducted a double-blind, randomized trial comparing the equivalence of azithromycin and ciprofloxacin (each given in a single 1-g dose of two 500-mg tablets) among 195 men with severe cholera caused by Vibrio cholerae O1 or O139. Patients were hospitalized for five days. A stool culture was performed daily. Primary outcome measures were clinical success (the cessation of watery stools within 48 hours after drug administration) and bacteriologic success (the inability to isolate V. cholerae after 48 hours).

RESULTS

Therapy was clinically successful in 71 of 97 patients receiving azithromycin (73 percent) and in 26 of 98 patients receiving ciprofloxacin (27 percent) (P<0.001) and bacteriologically successful in 76 of 97 patients receiving azithromycin (78 percent) and in 10 of 98 patients receiving ciprofloxacin (10 percent) (P<0.001). Patients who were treated with azithromycin had a shorter duration of diarrhea than did patients treated with ciprofloxacin (median, 30 vs. 78 hours); a lower frequency of vomiting (43 percent vs. 67 percent); fewer stools (median, 36 vs. 52); and a lower stool volume (median, 114 vs. 322 ml per kilogram of body weight). The median minimal inhibitory concentration of ciprofloxacin for the 177 isolates of V. cholerae O1 was 0.25 mug per milliliter, which was 11 to 83 times as high as that in previous studies at this site.

CONCLUSIONS

Single-dose azithromycin was effective in the treatment of severe cholera in adults. The lack of efficacy of ciprofloxacin may result from its diminished activity against V. cholerae O1 strains currently circulating in Bangladesh. (ClinicalTrials.gov number, NCT00229944.).

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.

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.

Reevaluating fluoroquinolone breakpoints for Salmonella enterica serotype Typhi and for non-Typhi salmonellae

Salmonella enterica infections cause considerable morbidity and mortality worldwide. Antimicrobial therapy may be life-saving for patients with extraintestinal infections with S. enterica serotype Typhi or non-Typhi salmonellae. Because antimicrobial resistance to several classes of traditional first-line drugs has emerged in the past several decades, the quinolone antimicrobial agents, particularly the fluoroquinolones, have become the drugs of choice. Recently, resistance to nalidixic acid has emerged among both Typhi and non-Typhi Salmonella serotypes. Such Salmonella isolates typically also have decreased susceptibility to fluoroquinolones, although minimum inhibitory concentrations of the fluoroquinolones usually are within the susceptible range of the interpretive criteria of the NCCLS. A growing body of clinical and microbiological evidence indicates that such nalidixic acid-resistant S. enterica infections also exhibit a decreased clinical response to fluoroquinolones. In this article, we recommend that laboratories test extraintestinal Salmonella isolates for nalidixic acid resistance, we recommend that short-course fluoroquinolone therapy be avoided for infection with nalidixic acid-resistant extraintestinal salmonellae, and we summarize existing data and data needs that would contribute to reevaluation of the current NCCLS fluoroquinolone breakpoints for salmonellae.

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.

Mutation patterns in gyrA and parC genes of ciprofloxacin resistant isolates of Neisseria gonorrhoeae from India

AIM

To analyse mutations in the gyrA and parC genes leading to possible increase in ciprofloxacin resistance (high MIC values for ciprofloxacin) in clinical isolates of Neisseria gonorrhoeae in Delhi, India.

METHOD

MIC of ciprofloxacin for 63 clinical isolates of N gonorrhoeae were examined by the Etest method. Subsequently, gyrA and parC genes of these isolates were amplified and sequenced for possible mutations.

RESULTS

Out of the 63 clinical isolates tested, only five (8%) isolates were found to be susceptible to ciprofloxacin (MIC <0.06 micro g/ml). DNA sequence analysis of the gyrA and the parC genes of all these isolates (n = 63) revealed that all isolates which were not susceptible to ciprofloxacin (n=58) had mutation(s) in gyrA and parC genes. 12 isolates (19%) exhibited high resistance with an MIC for ciprofloxacin of 32 micro g/ml. Two out of these 12 isolates (UD62 and UD63), harboured triple mutations (Ser-91 to Phe, Asp-95 to Asn and Val-120 to Leu) in the gyrA gene. The third mutation of Val-120 to Leu, lies downstream of the quinolone resistance determining region (QRDR) of the gyrA and has not been described before in gonococcus. In addition, both these isolates had a Phe-100 to Tyr substitution in the parC, a hitherto unknown mutation.

CONCLUSIONS

Emergence of ciprofloxacin resistance with high levels of MIC values (up to 32 micro g/ml) in India is alarming. Double and triple mutations in gyrA alone or together in gyrA and parC could be responsible for such a high resistance.

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.

Multidrug-resistant strains of Neisseria gonorrhoeae in Greece

Eighty-seven out of 575 gonococci isolated in Greece from 1991 to 1998 belonged to serovar Bropyst and exhibited resistance to penicillin, tetracycline, erythromycin, and chloramphenicol. Conventional and molecular typing showed three clusters, A, B, and C, that were associated with networks of high- frequency transmitters (cluster A with homosexuals and clusters B and C with refugees from Eastern Europe). Study of one isolate revealed mutations in the penA, mtrR, and porB genes that may explain the multidrug-resistant phenotype.

A randomized trial of ciprofloxacin versus cefixime for treatment of gonorrhea after rapid emergence of gonococcal ciprofloxacin resistance in The Philippines

From 1994 through 1996-1997, high-level ciprofloxacin resistance (minimum inhibitory concentration [MIC], > or = 4.0 microg/mL) increased from 9% to 49% of gonococcal isolates recovered from consecutive female sex workers in Cebu and Manila, The Philippines (P < .01). During 1996-1997, 105 female sex workers with gonorrhea were prospectively randomized to receive treatment with oral ciprofloxacin, 500 mg, or cefixime, 400 mg, and followed for test of cure. Neisseria gonorrhoeae was reisolated within 28 days after treatment from 1 (3.8%) of 26 women given cefixime versus 24 (32.3%) of 72 women given ciprofloxacin (P < .01). Treatment failure (reisolation of pretreatment auxotype/serovar) occurred in 14 (46.7%) of 30 women infected with strains with MICs of ciprofloxacin > or = 4.0 microg/mL versus 1 (3.6%) of 28 infected by strains with MICs < 4.0 microg/mL (P < .01). High-level, clinically significant gonococcal resistance to ciprofloxacin has rapidly emerged in The Philippines, and spread of fluoroquinolone resistance through commercial sex poses a threat to control of gonorrhea and prevention of human immunodeficiency virus infection and the acquired immunodeficiency syndrome.

Quinolone Resistance in Neisseria gonorrhoeae

Single-dose oral quinolones have been recommended for gonorrhea treatment since 1989. The antimicrobial resistance surveillance system has detected several outbreaks of quinolone-resistant gonococcal infections (QRNG), and sporadic treatment failures have been reported from high-incidence areas such as southeast Asia. QRNG may result from mutations that cause structural-functional changes in DNA topoisomerase (the quinolone target enzyme) or by changes in antimicrobial transport into the bacteria. QRNG has occurred sporadically in the United States, predominantly in persons with contact to persons in southeast Asia, and has typically occurred as an epiphenomenon in persons who were treated with other regimens. Nevertheless, this entity warrants close monitoring. The emergence of QRNG is probably related to antimicrobial misuse and overuse, in particular long-term suppressive or subtherapeutic doses.

In vitro antibiotic susceptibility of Neisseria gonorrhoeae in Jakarta, Indonesia

Antibiotic susceptibilities were determined for 122 Neisseria gonorrheae isolates obtained from 400 sex workers in Jakarta, Indonesia, and susceptibilities to ciprofloxacin, cefuroxime, cefoxitin, cefotaxime, ceftriaxone, chloramphenicol, and spectinomycin were found. All isolates were resistant to tetracycline. A number of the isolates demonstrated decreased susceptibilities to erythromycin (MIC >/= 1.0 microg/ml), thiamphenicol (MIC >/= 1.0 microg/ml), kanamycin (MIC >/= 16.0 microg/ml), penicillin (MIC >/= 2.0 microg/ml), gentamicin (MIC >/= 16.0 microg/ml), and norfloxacin (MIC = 0.5 microg/ml). These data showed that certain antibiotics previously used in the treatment of gonorrhea are no longer effective.

Increased ciprofloxacin resistance in gonococci isolated in Scotland

A review of the susceptibility of Neisseria gonorrhoeae isolated from 4415 episodes of infection in Scotland between 1991 and 1999 showed that the proportion of isolates with lowered susceptibility (ciprofloxacin minimum inhibitory concentration [MIC] > or = 0.05 mg/L) increased from 0.5% in 1991 to 5% in 1999 (p<0.001), whereas the proportion of isolates with clinical resistance (ciprofloxacin MIC > or = 1 mg/L) was significantly higher in 1999 than the average for the preceding 4 years (2.2% vs 0.9%; p=0.02). Ciprofloxacin is a recommended treatment for gonococcal infection in the UK but if resistance continues to increase at the present rate it might not be suitable as a first-line treatment of gonorrhoea for much longer.

Characterization of Neisseria gonorrhoeae strains with decreased susceptibility to fluoroquinolones isolated in Greece from 1996 to 1999

Of the 331 Neisseria gonorrhoeae strains isolated in Greece from 1996 to 1999, 39 (11.8%) exhibited decreased susceptibility to quinolones due to gyrA and parC mutations. Conventional typing and pulsed-field gel electrophoresis showed that 34 of these isolates were clonally related. Epidemiological data indicated that the epidemic clone was sustained in a group of high-frequency transmitters.

Antimicrobial resistance of Neisseria gonorrhoeae and high prevalence of ciprofloxacin-resistant isolates in Japan, 1993 to 1998

To assess the antimicrobial resistance of Neisseria gonorrhoeae isolated from 1993 through 1998 in Japan, susceptibility testing was conducted on 502 isolates. Selected isolates were characterized by auxotype and analysis for mutations within the quinolone resistance-determining region (QRDR) in the gyrA and parC genes, which confer fluoroquinolone resistance on the organism. Plasmid-mediated penicillin resistance (penicillinase-producing N. gonorrhoeae) decreased significantly from 1993-1994 (7.9%) to 1997-1998 (2.0%). Chromosomally mediated penicillin resistance decreased from 1993-1994 (12.6%) to 1995-1996 (1.9%) and then increased in 1997-1998 (10.7%). Chromosomally mediated tetracycline resistance decreased from 1993-1994 (3.3%) to 1997-1998 (2.0%), and no plasmid-mediated high-level tetracycline resistance was found. Isolates with ciprofloxacin resistance (MIC >/= 1 microg/ml) increased significantly from 1993-1994 (6.6%) to 1997-1998 (24.4%). The proline-requiring isolates were less susceptible to ciprofloxacin than the prototrophic or arginine-requiring isolates. Ciprofloxacin-resistant isolates contained three or four amino acid substitutions within the QRDR in the GyrA and ParC proteins.

Detection of decreased fluoroquinolone susceptibility in Salmonellas and validation of nalidixic acid screening test

We evaluated 1,010 Salmonella isolates classified as fluoroquinolone susceptible according to the National Committee for Clinical Laboratory Standards guidelines for susceptibility to nalidixic acid and three fluoroquinolones. These isolates were divided into two distinct subpopulations, with the great majority (n = 960) being fully ciprofloxacin susceptible and a minority (n = 50) exhibiting reduced ciprofloxacin susceptibility (MICs ranging between 0.125 and 0.5 microg/ml). The less ciprofloxacin-susceptible isolates were uniformly resistant to nalidixic acid, while only 12 (1.3%) of the fully susceptible isolates were nalidixic acid resistant. A similar association was observed between resistance to nalidixic acid and decreased susceptibility to ofloxacin or norfloxacin. A mutation of the gyrA gene could be demonstrated in all isolates for which the ciprofloxacin MICs were >/= 0.125 microg/ml and in 94% of the nalidixic acid-resistant isolates but in none of the nalidixic acid-susceptible isolates analyzed. Identification of nalidixic acid resistance by the disk diffusion method provided a sensitivity of 100% and a specificity of 87.3% as tools to screen for isolates for which the MICs of ciprofloxacin were >/= 0.125 microg/ml. We regard it as important that microbiology laboratories endeavor to recognize these less susceptible Salmonella strains, in order to reveal their clinical importance and to survey their epidemic spread.

Antimicrobial susceptibilities and plasmid contents of Neisseria gonorrhoeae isolates from commercial sex workers in Dhaka, Bangladesh: emergence of high-level resistance to ciprofloxacin

Commercial sex workers (CSWs) serve as the most important reservoir of sexually transmitted diseases (STD), including gonorrhea. Periodic monitoring of the antimicrobial susceptibility profile of Neisseria gonorrhoeae in a high-risk population provides essential clues regarding the rapidly changing pattern of antimicrobial susceptibilities. A study concerning the prevalence of gonococcal infection among CSWs was conducted in Bangladesh. The isolates were examined with regards to their antimicrobial susceptibility to, and the MICs of, penicillin, tetracycline, ciprofloxacin, cefuroxime, ceftriaxone, and spectinomycin by disk diffusion and agar dilution methods. The total plasmid profile of the isolates was also analyzed. Of the 224 CSWs, 94 (42%) were culture positive for N. gonorrhoeae. There was a good correlation between the results of the disk diffusion and agar dilution methods. Some 66% of the isolates were resistant to penicillin, and 34% were moderately susceptible to penicillin. Among the resistant isolates, 23.4% were penicillinase-producing N. gonorrhoeae (PPNG). 60.6% of the isolates were resistant and 38.3% were moderately susceptible to tetracycline, 17.5% were tetracycline-resistant N. gonorrhoeae, 11.7% were resistant and 26.6% had reduced susceptibility to ciprofloxacin, 2.1% were resistant and 11.7% had reduced susceptibility to cefuroxime, and 1% were resistant to ceftriaxone. All PPNG isolates contained a 3.2-MDa African type of plasmid, and a 24.2-MDa conjugative plasmid was present in 34.1% of the isolates. Since quinolones such as ciprofloxacin are recommended as the first line of therapy for gonorrhea, the emergence of significant resistance to ciprofloxacin will limit the usefulness of this drug for treatment of gonorrhea in Bangladesh.

Identification of novel mutation patterns in the parC gene of ciprofloxacin-resistant isolates of Neisseria gonorrhoeae

Of 65 ciprofloxacin-resistant, clinical isolates of Neisseria gonorrhoeae, 5 isolates exhibited ParC mutations previously undescribed in the gonococcus. For isolates containing two ParC mutations (the Ser-87-->Ile and Glu-91-->Gly mutations and the Gly-85-->Cys and Arg116-->Leu mutations) the MICs of ciprofloxacin (8.0 to 64.0 microg/ml) were higher than those for the isolate containing the single ParC mutation (Arg-116-->Leu; MIC, 1.0 microg/ml).

Sexually transmitted diseases in Ulaanbaatar, Mongolia

Although human immunodeficiency virus (HIV) rates are increasing rapidly in Asia, a full understanding of the extent of other sexually transmitted diseases (STDs) in many of these areas is lacking. There have been anecdotes of rising rates of STDs in Mongolia, a country thus far relatively unaffected by HIV. To further the understanding of STDs, a prevalence study was conducted in the STD clinic in Ulaanbaatar, the capital and largest city in Mongolia. Among 260 patients, the prevalence of gonorrhoea, chlamydia and syphilis was 31.1%, 8.1% and 8.6% respectively for males and 10.3%, 9.9% and 6.0% for females. Sixty-seven per cent of females had trichomoniasis and 19.7% of males had non-gonococcal urethritis (NGU). Forty-two per cent of gonococcal isolates had plasmid mediated resistance to penicillin, and chromosomal resistance to penicillin, tetracycline, and ciprofloxacin was documented. No patients were infected with HIV. STDs are a significant problem in Mongolia. Improved control efforts are urgently needed to prevent the emergence of HIV.

Incidence, epidemiology and evolution of reduced susceptibility to ciprofloxacin in Neisseria gonorrhoeae in Korea

OBJECTIVE: To verify the decrease of susceptibility to ciprofloxacin in Neisseria gonorrhoeae, determine the size of the recently reported new beta-lactamase plasmid and explain the high prevalence of penicillinase-producing Neisseria gonorrhoeae (PPNG). METHODS: Gonococci were isolated from prostitutes in Korea. Antimicrobial susceptibility was tested by NCCLS disk diffusion and agar dilution methods. Plasmid was isolated by an alkaline lysis method. Patterns of Nhel-digested genomic DNA were compared after pulsed-field gel electrophoresis (PFGE). RESULTS: The minimum inhibitory concentration of ciprofloxacin for 50% of the isolates rose from 0.015 mg/L in 1993 to 0.12 mg/L in 1996. The proportion of PPNG remained at 70% or over during the 5-year period. The size of a novel beta-lactamase plasmid, first reported in 1994, was determined to be approximately 3.2 MDa, and 48% of the PPNG isolates contained it. Twelve of 50 isolates had the same PFGE pattern and nine others another pattern. CONCLUSION: The rapid decrease of fluoroquinolone-susceptible gonococci suggests that in the near future the drug may become less useful for gonorrhea treatment. The new 3.2-MDa plasmid may have been introduced as a result of the recent increase in overseas travel. The PFGE pattern suggests that high prevalence of PPNG may be due to dissemination of a few resistant clones among the high-risk groups.

Antimicrobial resistance in Neisseria gonorrhoeae in Finland, 1976 to 1995. The Finnish Study Group For Antimicrobial Resistance

BACKGROUND AND OBJECTIVES

The worldwide increase in antimicrobial resistance in Neisseria gonorrhoeae prompted the authors to evaluate the status and course of resistance in gonococci in Finland.

GOALS

The minimal inhibitory concentrations (MIC) of penicillin, tetracycline, spectinomycin, ciprofloxacin, ceftriaxone, and cefixime were tested for 337 consecutive clinical N. gonorrhoeae isolates collected in 19 Finnish microbiology laboratories in 1993.

STUDY DESIGN

The results were compared with data obtained in three Finnish laboratories in 1986 and contrasted with the development of the incidence of gonorrhea and the prevalence of penicillinase-producing N. gonorrhoeae (PPNG) in Finland, 1976 to 1995. The number of strains with an elevated MIC to ciprofloxacin was assessed by questionnaire.

RESULTS

A decrease, from more than 50% in 1986 to 20% in 1993, of strains susceptible to penicillin and tetracycline was observed. The prevalence of PPNG increased from 0% (1976) to 5.7% (1995). In 1995, two strains with a ciprofloxacin MIC of > or = 32 micrograms/ml were reported. No resistance to ceftriaxone or spectinomycin was detected.

CONCLUSIONS

In spite of the rarity of gonorrhea and the availability of efficient antimicrobials in Finland, monitoring of the antimicrobial resistance of N. gonorrhoeae remains important.

Molecular epidemiology of infections with Neisseria gonorrhoeae among visitors to a sexually transmitted diseases clinic

OBJECTIVES

To identify determinants for plasmid-mediated resistance to penicillin (penicillinase-producing Neisseria gonorrhoeae [PPNG]) and tetracycline (tetracycline-resistant N. gonorrhoeae [TRNG]) among gonococci, to determine the distribution of bacterial characteristics, and to correlate these with antibiograms and patient characteristics.

STUDY DESIGN

Gonococcal isolates from 131 patients attending a sexually transmitted diseases clinic in The Netherlands in 1994 were auxotyped and serotyped and antimicrobial susceptibility was tested. Information on patient characteristics was collected at the initial visit.

RESULTS

The most prevalent serotype, IB-1 (26%), proved to be related to sexual contact with casual partners, especially commercial sex partners. In addition, IB-1 strains were associated with PPNG and displayed higher minimum inhibitory concentrations (MICs) for ceftriaxone, cefuroxime, and ciprofloxacin. Homosexual men were more often infected with nonrequiring, IB-2, and IB-6 strains than heterosexuals. These strains were very sensitive to ceftriaxone and ciprofloxacin. Overall, one strain showed decreased susceptibility to ciprofloxacin (MIC 0.5 microgram/ml), but no resistance to ceftriaxone, ciprofloxacin, or cefuroxime was observed. However, 31% of the isolates were TRNG, PPNG, or both. Determinants for these resistant strains among men were the use of antibiotics (odds ratio [OR] = 4.8, 90% confidence interval [CI] 1.3-19.1), Surinam or Morrocan origin (OR = 3.3, 90% CI 1.3-8.4), and homosexual contacts (OR = 0.1, 90% CI 0.03-0.4).

CONCLUSIONS

Different types, with variable susceptibility, were associated with homosexual and commercial sexual behavior. PPNG and TRNG were more commonly isolated from antibiotic users, heterosexual individuals, and ethnic minorities. Continuous surveillance of susceptibility is needed to follow the spread of PPNG and TRNG and to detect resistance to the currently recommended agents in a timely fashion.

Antimicrobial activity of trovafloxacin tested against ciprofloxacin-susceptible and -resistant Neisseria gonorrhoeae. Interpretive criteria and comparisons with Etest results

Trovafloxacin, a new fluorinated naphthyridine, has enhanced activity against Gram-positive cocci, while retaining an excellent spectrum against Gram-negative pathogens. It has been used successfully in clinical trials for therapy of gonorrhea, and this investigation proposes in vitro susceptibility testing criteria for trovafloxacin. A total of 150 Neisseria gonorrhoeae clinical isolates (50 resistant to ciprofloxacin; MICs > or = 0.12 microgram/mL) were tested by methods recommended by the National Committee for Clinical Laboratory Standards (NCCLS) and the Etest (AB BIODISK, Solna, Sweden). Trovafloxacin was very active against gonococci (MIC90, 0.008 to 0.015 microgram/mL), but was generally eightfold less potent versus ciprofloxacin-resistant strains. Etest results correlated well (r = 0.96; 98% of MICs +/- one log2 dilution) compared to the reference agar dilution test. Reference agar dilution and Etest MICs were compared to disk-diffusion test zones (10-micrograms trovafloxacin disk), and excellent categorical agreement (89.4 to 99.3%) was achieved without significant false-susceptible or -resistant error (< or = 1.3%). Tentative breakpoints were suggested initially to outline the ciprofloxacin-susceptible and trovafloxacin-susceptible as susceptible (MIC, < or = 0.015 microgram/mL; zones > or = 47 mm), and strains with various well-characterized mutations of the gyr A and par C genes as either intermediate or resistant to trovafloxacin. When the results of clinical studies treating ciprofloxacin-resistant N. gonorrhoeae with trovafloxacin become available, the alternative breakpoints could be utilized for resistant MIC breakpoints of > or = 0.06 microgram/mL or > or = 0.5 microgram/mL. Trovafloxacin was stable in supplemented GC agar for 21 days stored at refrigerated temperatures. These in vitro results indicate that trovafloxacin should be a very acceptable agent for therapy of gonorrhea and other common sexually transmitted pathogens.

Antimicrobial susceptibility and types of Neisseria gonorrhoeae in Greece. Data for the period 1990 to 1993

BACKGROUND

Surveillance of the rapidly changing patterns of antimicrobial resistance of Neisseria gonorrhoeae is imperative for monitoring gonococcal infection.

GOAL

To describe the types and the antimicrobial susceptibility profile of a representative samples of gonococci isolated in Greece between 1990 and 1993.

STUDY DESIGN

The antimicrobial susceptibilities, serovar/auxotypes classes, and plasmid contents of 263 consecutive isolates of N. gonorrhoeae, recovered from cases of male gonococcal urethritis, were determined.

RESULTS

Penicillinase-producing N. gonorrhoeae (PPNG) were isolated at a rate of 6.1% and were mostly from imported cases of infection. Six (2.3%) of the isolates (one PPNG and five non-PPNG) were highly resistant to tetracycline, and one PPNG strain was resistant to norfloxacin and ciprofloxacin. Strains with chromosomal resistance to penicillin, tetracycline, erythromycin, and chloramphenicol accounted for 18.5%, 12.5%, 19%, and 16% of the isolates, respectively; much higher proportions of strains were intermediately susceptible to these antibiotics. Spectinomycin and cefotaxime were active against all gonococci studied. A shift to IB serovars and to sporadic types of strains was noted from previous years among the non-PPNG isolates. This is compatible with the marked increase in the rate of imported cases of infection caused by n on-PPNG strains.

CONCLUSIONS

The emergence of high-level resistance to tetracycline and resistance to fluoroquinolones was ascertained. At the present, however, the main problem with gonococcal resistance in Greece seems to ensue from the increasing rates of chromosomally resistant strains. Moreover, the increasing frequency of imported gonococci underlines the necessity for continuous epidemiologic surveillance.

Antimicrobial susceptibilities of strains of Neisseria gonorrhoeae in Bangkok, Thailand: 1994-1995

BACKGROUND AND OBJECTIVES

Failure of uncomplicated gonococcal infections acquired in the Far East to respond to doses of ciprofloxacin and ofloxacin recommended by the Centers for Disease Control and Prevention have been identified in Australia, the United Kingdom, and the United States. In the Republic of the Philippines, 54.3% of strains exhibited decreased susceptibility to fluoroquinolones; 12% of strains were resistant to ciprofloxacin. This study was undertaken to compare the antimicrobial susceptibilities of gonococcal isolates in Bangkok, Thailand, with those in the Republic of the Philippines.

GOAL

To determine the frequency and diversity of antimicrobial resistance, particularly to fluoroquinolones, in gonococcal strains in Bangkok, Thailand.

STUDY DESIGN

Strains of Neisseria gonorrhoeae isolated from 101 patients with uncomplicated gonorrhea in Bangkok, Thailand, in July, 1994 (46 strains) and November, 1994 to July, 1995 (55 strains), were characterized by auxotype/serovar class, antimicrobial susceptibilities, and plasmid profile. Susceptibilities were determined to penicillin G, tetracycline, ceftriaxone, cefixime, cefoxitin, ciprofloxacin, ofloxacin, norfloxacin, erythromycin, kanamycin, and thiamphenicol.

RESULTS

Of 101 strains, 89.1% (90/101) were resistant to penicillin or tetracycline. Plasmid-mediated resistance to penicillin or tetracycline was identified in 33.7% (34/101) of the isolates: penicillinase-producing Neisseria gonorrhoeae (17.8%; 18/101), tetracycline-resistant Neisseria gonorrhoeae (7.9%; 8/101), and penicillinase-producing/tetracycline-resistant Neisseria gonorrhoeae (7.9%; 8/101). Most penicillinase-producing strains (96.2%; 25/26) possessed the 4.4-megadalton (Md) beta-lactamase plasmid; one strain possessed the 3.2-Md beta-lactamase plasmid. Chromosomally mediated resistance to penicillin and tetracycline was exhibited by 51.5% (52/101) of strains, and 4.0% (4/101) were tetracycline resistant. All strains were susceptible to spectinomycin. Of 21.8% (22/101) strains exhibiting decreased susceptibility to ciprofloxacin (minimal inhibitory concentration [MIC] > or = 0.125 microgram/ml), one strain (ciprofloxacin MIC, 0.5 microgram/ml; ciprofloxacin inhibition zone diameter of 23 mm) had MICs of 2.0 and 8.0 micrograms/ml for ofloxacin and norfloxacin, respectively, indicating resistance to these agents. Decreased susceptibility to ciprofloxacin was identified in strains with chromosomally mediated resistance to penicillin or tetracycline and in penicillinase-producing strains.

CONCLUSIONS

In Bangkok, Thailand, gonococcal isolates exhibit resistance to penicillin, tetracycline, kanamycin, and thiamphenicol. Decreased susceptibility to fluoroquinolones is emerging in a variety of strains of N. gonorrhoeae. Thus, all gonococcal infections should be treated with antimicrobial therapies known to be active against all gonococcal strains to reduce the spread of strains exhibiting decreased susceptibilities to fluoroquinolones.

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.

Molecular epidemiology, in 1994, of Neisseria gonorrhoeae in Manila and Cebu City, Republic of the Philippines

BACKGROUND AND OBJECTIVES

Failure of gonococcal infections to respond to 500 mg of ciprofloxacin or 400 mg of ofloxacin has been reported from Australia, the United Kingdom, and the United States. Recently, high rates of decreased susceptibility to the fluoroquinolones have been detected in penicillinase-producing Neisseria gonorrhoeae in the Republic of the Philippines.

GOALS

To assess the diversity of antimicrobial-resistant gonococcal strains isolated from female sex workers in Manila and Cebu City in the Republic of the Philippines in 1994.

STUDY DESIGN

Isolates of N. gonorrhoeae isolated from 92 female sex workers in Manila (n = 28) and Cebu City (n = 64), respectively, were characterized by plasmid profile, auxotype/serovar class, and antimicrobial susceptibility profile.

RESULTS

Plasmid-mediated resistance to penicillin or tetracycline was identified in 79.3% (73/92) of the isolates: penicillinase-producing N. gonorrhoeae (65/92; 70.7%), tetracycline-resistant N. gonorrhoeae (6/92; 6.5%), and penicillinase-producing/tetracycline-resistant N. gonorrhoeae (1/92; 1.1%). A beta-lactamase plasmid of 3.9 megadaltons was discovered. Of 54.3% (50/92) of strains resistant to nalidixic acid, 84% (42/50) of strains had minimum inhibitory concentrations of > or = 0.125 microgram/ml ciprofloxacin; penicillinase-producing N. gonorrhoeae (possessing the 3.05-, 3.2-, 3.9-, and 4.4-megadalton beta-lactamase plasmids, respectively) accounted for 68% (34/50) of these strains.

CONCLUSIONS

In the Republic of the Philippines, gonococcal isolates resistant to penicillin or tetracycline accounted for 85.9% (79/92) of the isolates examined and included strains exhibiting resistance to fluoroquinolones. All gonococcal infections should be treated with antimicrobial therapies known to be active against all gonococcal strains to reduce the spread of strains exhibiting decreased susceptibilities to fluoroquinolones.