Antimicrobial resistance of Neisseria gonorrhoeae in Japan, 1993–2002: continuous increasing of ciprofloxacin-resistant isolates

The frequency of mutations in the penA, mtrR, gyrA and parC genes of Neisseria gonorrhoeae, the presence of tetM gene and antibiotic resistance/susceptibility: a systematic review and meta-analyses

Gonorrhoea is currently one of the most important sexually transmitted infections (STIs) due to the increasing spread of multidrug-resistant strains of N. gonorrhoeae. The aim of this study was to analyse the association between resistance or decreased susceptibility to antibiotics in N. gonorrhoeae and the presence of mutations in the penA, mtrR, gyrA and parC genes, and the presence of tetM gene. We conducted a systematic review according to the PRISMA guidelines. We selected 19 studies for the penA gene, 23 for gyrA and parC, 18 for mtrR and 12 for tetM using the Science Direct and PubMed databases. Meta-analyses of isolates resistant to penicillin, cefixime and ceftriaxone showed that more than 50% of isolates had mutations in the penA and mtrR genes. More than 50% of azithromycin-resistant isolates had mutations in the mtrR gene, while more than 50% of ciprofloxacin-resistant and intermediate-resistant isolates had mutations in gyrA. Less than 50% of the isolates with intermediate resistance to ciprofloxacin had mutations in parC. The plasmid containing the tetM gene was found in more than 50% of tetracycline-resistant isolates. Infection surveillance and genetic studies are important for controlling the spread of the disease, which can improve the quality of life of infected people and reduce the financial burden on public health systems.

The third nationwide surveillance of antimicrobial susceptibility against Neisseria gonorrhoeae from male urethritis in Japan, 2016-2017

Neisseria gonorrhoeae is one of the important pathogens of sexually transmitted infections. N. gonorrhoeae is rapidly becoming antimicrobial resistant, and there are few drugs that are effective in the initial treatment of gonorrhea. To understand the trends of antimicrobial susceptibility of N. gonorrhoeae, the Surveillance Committee of the Japanese Society of Infectious Diseases, the Japanese Society for Chemotherapy, and the Japanese Society of Clinical Microbiology conducted the third nationwide antimicrobial susceptibility surveillance of N. gonorrhoeae isolated from male urethritis. The specimens were collected from male patients with urethritis at 30 facilities from May 2016 to July 2017. From the 159 specimens collected, 87 N. gonorrhoeae strains were isolated, and 85 were tested for susceptibility to 21 antimicrobial agents. All strains were non-susceptible to penicillin G. Seven strains (8.2%) were β-lactamase-producing strains. The rates of susceptibility to cefixime and cefpodoxime were 96.5% and 52.9%, respectively. Three strains were non-susceptible with a minimum inhibitory concentration (MIC) of 0.5 mg/L for cefixime. None of the strains were resistant to ceftriaxone or spectinomycin. The susceptibility rate for ciprofloxacin was 23.5% (20 strains), and no strains showed intermediate susceptibility. The susceptibility rate against azithromycin was 81.2%, with one strain isolated with a MIC of 8 mg/L against azithromycin. The results of this surveillance indicate that ceftriaxone and spectinomycin, which are currently recommended for gonococcal infections in Japan, appear to be effective. It will be necessary to further expand the scale of the next surveillance to understand the current status of drug-resistant N. gonorrhoeae in Japan.

The second nationwide surveillance of the antimicrobial susceptibility of Neisseria gonorrhoeae from male urethritis in Japan, 2012-2013

Worldwide, the most important concern in the treatment of sexually transmitted infections is the increase in antimicrobial resistant Neisseria gonorrhoeae strains including resistance to cephalosporins, penicillins, fluoroquinolones or macrolides. To investigate the trends of antimicrobial susceptibility among N. gonorrhoeae strains isolated from male patients with urethritis, a Japanese surveillance committee conducted the second nationwide surveillance study. Urethral discharge was collected from male patients with urethritis at 26 medical facilities from March 2012 to January 2013. Of the 151 specimens, 103 N. gonorrhoeae strains were tested for susceptibility to 20 antimicrobial agents. None of the strains was resistant to ceftriaxone, but the minimum inhibitory concentration (MIC) 90% of ceftriaxone increased to 0.125 μg/ml, and 11 (10.7%) strains were considered less susceptible with an MIC of 0.125 μg/ml. There were 11 strains resistant to cefixime, and the MICs of these strains were 0.5 μg/ml. The distributions of the MICs of fluoroquinolones, such as ciprofloxacin, levofloxacin and tosufloxacin, were bimodal. Sitafloxacin, a fluoroquinolone, showed strong activity against all strains, including strains resistant to other three fluoroquinolones, such as ciprofloxacin, levofloxacin and tosufloxacin. The azithromycin MICs in 2 strains were 1 μg/ml.

Decreased susceptibility of Neisseria gonorrhoeae isolates from Switzerland to Cefixime and Ceftriaxone: antimicrobial susceptibility data from 1990 and 2000 to 2012

Background

Neisseria gonorrhoeae can rapidly develop resistance to antimicrobial agents. Over the last years, decreased gonococcal susceptibility to third-generation cephalosporins, especially cefixime, emerged worldwide. Therefore, current international guidelines recommend dual therapy for gonorrhoea with ceftriaxone plus either azithromycin or doxycycline. Gonococcal susceptibility data in Switzerland are sparse.

Methods

We investigated the prevalence of antibiotic susceptibility of N. gonorrhoeae in specimens collected between 1990 and 2012 at the University of Zurich, Switzerland. Minimum inhibitory concentrations (MICs) for cefixime, ceftriaxone, ciprofloxacin, and penicillin were determined by Etests. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints were used to define reduced susceptibility.

Results

A total of 320 isolates were tested. Between 1990 and 2006 all tested samples were susceptible to both cephalosporins. Subsequently, the prevalence of elevated MICs for cefixime increased to 10.4% (2007/2008), 11.5% (2009/2010), and 11.4% (2011/2012); and for ceftriaxone to 2.4% (2007/2008), 4.7% (2009/2010), and 0% (2011/2012), respectively. The prevalence of resistance to ciprofloxacin (72.7%) and penicillin (22.7%) was high in 2011/2012.

Conclusions

Decreasing susceptibility of N. gonorrhoeae to third-generation cephalosporins in Switzerland supports treatment recommendations with ceftriaxone plus azithromycin or doxycycline. Health-care providers need to be aware of possible treatment failures with cephalosporins. Continued surveillance of gonococcal antimicrobial resistance is essential.

Safety evaluation of cephalosporins based on utilization and adverse drug events: analysis of two databases in China

OBJECTIVE

The aim of this study is to evaluate the safety of cephalosporins, based on utilization and adverse drug events (ADEs).

METHODS

This is a retrospective study using data on cephalosporins, obtained from Yangtze River hospital drug information and the Wuhan adverse drug reactions monitoring center database, from January 2009 to December 2010, in 30 hospitals in China.

RESULTS

22/44 (55%) cephalosporins were third-generation, which accounted for more than 50% of total expenditure. The top five cephalosporins (sorted by their defined daily doses) were cefodizime sodium, cefoperazone/sulbactam sodium, cefaclor, cefixime and cefmenoxime hydrochloride, which were used 182.93, 110.63, 109.09, 101.47 and 100.05 defined daily dose per 10,000 days, respectively. Third-generation cephalosporins were responsible for 747/1337 ADEs (55.87%). In particular, 208 episodes (15.56%) were associated with ceftriaxone. The most frequently reported damages were involved in the skin and its appendages (967, 68.92%). 603 (45.10%) were identified as definite in causality evaluation. Cefaclor was found to be safer than other cephalosporins, whereas ceftriaxone was found to be less safe.

CONCLUSION

This retrospective evaluation demonstrated that overused and misused cephalosporins caused a relatively high incidence of ADEs. Therefore, surveillance should be strengthened successfully to optimize the rational use of cephalosporins.

[Nationwide antimicrobial susceptibility survey of Neisseria gonorrhoeae isolates in Japan]

In a nationwide antimicrobial susceptibility survey of 494 Nesseria gonorrhoeae isolates collected from February 2008 to December 2009 in 3 regions of Japan, 112 (22.7%) were collected from western Japan (Kinki, Chugoku, Shikoku, and Kyushu), 277 (56.1%) from mid-eastern Japan (Kanto), and 105 (21.1%) from eastern Japan (Tokai, Hokuriku, Koushinetsu, Tohoku, and Hokkaido). Resistance to ciprofloxacin (CPFX) was 72.8%, to penicillin G (PCG) 19.8%, and to tetracycline (TC) 18.2%. Intermediate resistance to CPFX was 1.8%, to PCG 73.7%, and to TC 43.7%. These results indicate that both types of resistance to the 3 agents were very high. Intermediate resistance to cefixime (CFIX) was 38.1% and to cefozidim (CDZM) 13.4%. Resistance to CFIX was only 0.4% and to CDZM 0%. Susceptibility to azithromycin was 96.6%, to ceftriaxone 99.8%, and to spectinomycin 100%. No significant difference in resistance was seen to different antimicrobial agent classes tested in the 3 regions, although intermediate resistance to CFIX in western Japan was significantly higher than in mid-eastern Japan.

Identification of TEM-135 beta-lactamase in penicillinase-producing Neisseria gonorrhoeae strains in Japan

Ten penicillinase-producing Neisseria gonorrhoeae (PPNG) strains isolated from 2000 to 2008 were characterized by multilocus sequence typing, multiantigen sequence typing, and plasmid typing. Sequence analysis showed that 8 strains contained a TEM-1 beta-lactamase gene. However, two other genetically distinct PPNG strains, isolated in 2004 and 2008, each contained a TEM-135 beta-lactamase on different plasmids, a Toronto/Rio type R plasmid and an Asia type R plasmid, suggesting independent origins of these PPNG strains.

Antimicrobial resistance in clinical isolates of Neisseria subflava from the oral cavities of a Japanese population

A recent study indicated that Neisseria subflava, one of the commensal Neisseria species, may play an important role in the emergence of Neisseria gonorrhoeae strains with chromosomally mediated resistance to penicillin or cephalosporin by the horizontal genetic exchange of penA genes encoding the target site for penicillin or cephalosporin. The present investigation examined the antimicrobial susceptibility of 45 isolates of N. subflava from the oral cavities of Japanese men and women to various agents used for the treatment of gonococcal infections. Of the 45 isolates, 40 (88.9%) and 4 (8.8%) were intermediately resistant and resistant to penicillin, respectively, with the minimal inhibitory concentration (MIC)(50) and MIC(90) of penicillin being 0.5 mg/l and 1 mg/l, respectively. Of the 45 isolates, 13 (28.9%) and 14 (31.1%) were resistant to tetracycline and ciprofloxacin, respectively, and 3 (6.7%) showed reduced susceptibility to cefixime (although the susceptibility category was not determined). These results indicate that several isolates of N. subflava have acquired resistance or intermediate resistance to various antimicrobial agents, including penicillin, cephalosporin, tetracycline, and ciprofloxacin. The present study may thus confirm that N. subflava may be involved in the emergence of N. gonorrhoeae strains with either intermediate or total resistance to penicillin or cephalosporin by the horizontal genetic exchange of the penA gene.

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.

Antimicrobial susceptibility of Neisseria gonorrhoeae isolated in Jiangsu Province, China, with a focus on fluoroquinolone resistance

In this study, the phenotypic and genotypic resistance to fluoroquinolones in Neisseria gonorrhoeae isolated in Jiangsu Province, China, was analysed. In vitro susceptibility testing of eight antimicrobial agents, including ciprofloxacin and levofloxacin, against 95 clinical isolates was carried out. Detection of mutations in the gyrA and parC genes was performed by sequence analysis. The clinical isolates demonstrated 100 % resistance to ciprofloxacin and 98.9 % non-susceptibility to levofloxacin. All of the isolates were susceptible to cefotaxime and ceftriaxone. For cefepime, spectinomycin and tetracycline, 98.9, 94.7 and 1.1 % of the isolates were susceptible, respectively. None of the isolates was susceptible to penicillin. Five types based on gyrA mutations could be categorized among 54 isolates with seven different mutation sites found on their parC gene. Analysis of sequence results showed that the gyrA mutation Asp-95→Ala and the parC mutations Ser-87→Arg and Ser-87→Asn made a significant contribution to the resistance to fluoroquinolones, in addition to double mutations found in each gene. Therefore, the use of fluoroquinolones in the treatment of N. gonorrhoeae infections in Jiangsu Province is not recommended, while the use of third- and fourth-generation cephalosporins and spectinomycin is recommended.

Multiple doses of cefodizime are necessary for the treatment of Neisseria gonorrhoeae pharyngeal infection

A single dose of cefodizime (CDZM), ceftriaxone (CTRX), or spectinomycin (SPCM) is recommended for the treatment of gonococcal urethritis or uterine cervicitis in the era of multidrug-resistant Neisseria gonorrhoeae; namely, cefozopran-resistant N. gonorrhoeae (CZRNG). N. gonorrhoeae pharyngeal infection is not so rare in Japan; however, the proper treatment regimen for this infection is not clear. We previously found that a single dose of CDZM completely eradicated multidrug-resistant N. gonorrhoeae in patients with urethritis and uterine cervicitis, so we tried a single 1.0-g dose of CDZM for the treatment of N. gonorrhoeae pharyngeal infection, including infections with CZRNG. The eradication rate of N. gonorrhoeae from the pharynx was 63.0% with a single 1.0-g dose of CDZM, while the rate for CZRNG with the same dose of CDZM was 38.5%. N. gonorrhoeae was completely eradicated from the pharynx when patients received one or two additional doses of CDZM. Therefore, we concluded that two to three doses of CDZM were necessary for the treatment of N. gonorrhoeae pharyngeal infection including infection with CZRNG.

Amino acid substitutions in mosaic penicillin-binding protein 2 associated with reduced susceptibility to cefixime in clinical isolates of Neisseria gonorrhoeae

The molecular mechanisms of reduced susceptibility to cefixime in clinical isolates of Neisseria gonorrhoeae, particularly amino acid substitutions in mosaic penicillin-binding protein 2 (PBP2), were examined. The complete sequence of ponA, penA, and por genes, encoding, respectively, PBP1, PBP2, and porin, were determined for 58 strains isolated in 2002 from Japan. Replacement of leucine 421 by proline in PBP1 and the mosaic-like structure of PBP2 were detected in 48 strains (82.8%) and 28 strains (48.3%), respectively. The presence of mosaic PBP2 was the main cause of the elevated cefixime MIC (4- to 64-fold). In order to identify the mutations responsible for the reduced susceptibility to cefixime in isolates with mosaic PBP2, penA genes with various mutations were transferred to a susceptible strain by genetic transformation. The susceptibility of partial recombinants and site-directed mutants revealed that the replacement of glycine 545 by serine (G545S) was the primary mutation, which led to a two- to fourfold increase in resistance to cephems. Replacement of isoleucine 312 by methionine (I312M) and valine 316 by threonine (V316T), in the presence of the G545S mutation, reduced susceptibility to cefixime, ceftibuten, and cefpodoxime by an additional fourfold. Therefore, three mutations (G545S, I312M, and V316T) in mosaic PBP2 were identified as the amino acid substitutions responsible for reduced susceptibility to cefixime in N. gonorrhoeae.

In vitro synergistic effects of double combinations of beta-lactams and azithromycin against clinical isolates of Neisseria gonorrhoeae

In Japan, Neisseria gonorrhoeae, a sexually transmitted pathogen, has recently shown significant resistance to various antimicrobial agents. In this study, a checkerboard method was utilized to investigate the in vitro activities of cefixime (CFIX), cefteram (CFTM), or amoxicillin (AMPC) in combination with azithromycin (AZM) against 25 clinical isolates of N. gonorrhoeae. Synergy, defined as a fractional inhibitory concentration (FIC) index of less than or equal to 0.50, was observed in 32% of isolates with CFIX+AZM, 12% of isolates with CFTM+AZM, and 4% of isolates with AMPC+AZM. Moreover, partial synergy, defined as an FIC index of greater than 0.50 and less than 1, was observed in 44% of isolates with CFIX+AZM, 68% of isolates with CFTM+AZM, and 52% of isolates with AMPC+AZM. In particular, as a result of the combination of CFIX and AZM, for all isolates, significant reductions were observed in the median CFIX minimum inhibitory concentration (MIC; from 0.25 to 0.008 microg/ml; P < 0.0001) and the median AZM MIC (from 0.12 to 0.03 microg/ml; P < 0.0001). However, antagonism, defined as an FIC index of greater than 1, was observed in only 4% of the isolates with both CFIX+AZM and CFTM+AZM, while it was seen in 12% of the isolates with AMPC+AZM. To our knowledge, this is the first study to demonstrate that the in vitro activity of CFIX against N. gonorrhoeae can be significantly enhanced in combination with AZM.

Activity of gemifloxacin tested against Neisseria gonorrhoeae isolates including antimicrobial-resistant phenotypes

The antigonococcal potency of gemifloxacin and 5 reference comparator antimicrobials was determined for a selected collection of gonococcal isolates. The 250 Neisseria gonorrhoeae strains were inclusive of (1) 50 historic strains from Japan with elevated fluoroquinolone minimal inhibitory concentration values (QRNG) and (2) 200 contemporary strains from clinical specimens in 2004 (176 from 6 sentinel sites in the United States and 24 bacteremic isolates from the SENTRY Antimicrobial Surveillance Program). The rank order of potency of the tested antimicrobials for the entire collection was: ceftriaxone (MIC(90) = 0.06 microg/mL) > gemifloxacin (1 microg/mL) > tetracycline (2 microg/mL) > ciprofloxacin = levofloxacin = penicillin (4 microg/mL). The activity of gemifloxacin was not affected by penicillinase production; however, its activity was decreased for penicillin-resistant strains. Cross-resistance between gemifloxacin and the older fluoroquinolones was present, and the gemifloxacin MIC90 value was higher for the ciprofloxacin-resistant strains compared with the ciprofloxacin-susceptible strains (2 versus 0.016 mug/mL, respectively). More than 20.0% of the recent clinical strains were resistant to penicillin, tetracycline, and ciprofloxacin with >30.0% of gonococci resistant to ciprofloxacin in Washington State and Hawaii. The historic QRNG strains from the Far East were predominantly of intermediate susceptibility (88.0%) to ciprofloxacin, with a gemifloxacin MIC90 value of only 0.25 microg/mL. The bacteremic gonococcal strains were exquisitely susceptible to the 3 quinolones tested (ciprofloxacin, levofloxacin, and gemifloxacin, MIC90 at < or = 0.03 microg/mL) and ceftriaxone (MIC90 = 0.06 microg/mL). In summary, the potency of gemifloxacin was competitive and positioned between that of ceftriaxone and older quinolones or penicillin or tetracycline, irrespective of the gonococcal resistance phenotype. Gemifloxacin should be considered for further development as a therapeutic option to treat uncomplicated infections due to emerging strains resistant to penicillins, tetracycline, and some older fluoroquinolones.

Analysis of mutations within multiple genes associated with resistance in a clinical isolate of Neisseria gonorrhoeae with reduced ceftriaxone susceptibility that shows a multidrug-resistant phenotype

A Neisseria gonorrhoeae strain with a reduced susceptibility to ceftriaxone (minimum inhibitory concentration (MIC) = 0.5 microg/mL) was isolated among 398 clinical isolates obtained from 2000-2001 in Fukuoka City, Japan. The N. gonorrhoeae strain was negative for penicillinase production but it showed multidrug resistance against penicillin (MIC = 8 microg/mL), tetracycline (MIC = 4 microg/mL), azithromycin (MIC = 0.5 microg/mL) and ciprofloxacin (MIC = 16 microg/mL). The molecular mechanisms of the multidrug-resistant phenotype in this strain were analysed. Polymerase chain reaction and direct DNA sequencing were performed to identify mutations within the penA, ponA, mtrR, penB, gyrA and parC genes of the gonococcal strain, which thus explain the multidrug-resistant phenotype. The N. gonorrhoeae strain contained a significantly different sequence of the penA gene from that of the ceftriaxone-susceptible strains. Some regions of the transpeptidase domain within this penA gene were closely similar to those found in other Neisseria species such as Neisseria subflava, Neisseria flavescens or Neisseria perflava/sicca. This strain also included a ponA mutation that is associated with high-level resistance to penicillin, mtrR mutations that mediate overexpression of the MtrCDE efflux pump responsible for resistance to hydrophobic agents such as azithromycin, and penB mutations that reduce porin permeability to hydrophilic agents such as tetracycline. Moreover, this strain contained gyrA and parC mutations that confer high-level resistance to ciprofloxacin. These results indicate the emergence of a N. gonorrhoeae strain with reduced susceptibility to ceftriaxone, which also showed a multidrug-resistant phenotype that can be explained by the presence of multiple loci mutations associated with antibiotic resistance.

Single dose of cefodizime completely eradicated multidrug-resistant strain of Neisseria gonorrhoeae in urethritis and uterine cervicitis

Cefodizime (CDZM) has strong antimicrobial activity to Neisseria gonorrhoeae in vitro. However, multidrug-resistant N. gonorrhoea emerged and has been increasing in Japan. To know the effectiveness of CDZM on gonococcal urethritis and uterine cervicitis even in the era of multidrug-resistant N. gonorrhoeae, a clinical trial of single-dose therapy of CDZM for gonococcal urethritis and uterine cervicitis was conducted. N. gonorrhoeae was eradicated from 100% of patients with gonococcal urethritis and uterine cervicitis by a single dose of CDZM. In conclusion, CDZM is one of most suitable drugs for the treatment of gonococcal genital infection in the era of multidrug-resistant N. gonorrhoeae.

Activity of faropenem tested against Neisseria gonorrhoeae isolates including fluoroquinolone-resistant strains

We evaluated the anti-gonococcal potency of faropenem along with 7 comparator reference antimicrobials against a preselected collection of clinical isolates. The 265 isolates were inclusive of 2 subsets: 1) 76 well-characterized resistant phenotypes of gonococcal strains (53 quinolone-resistant strains--31 with documented quinolone resistance-determining region changes from Japan, 15 strains resistant to penicillin and tetracycline, and 8 strains with intermediate susceptibility to penicillin) and 2) 189 recent isolates from clinical specimens in 2004 from 6 states across the United States where quinolone resistance is prevalent. Activity of faropenem was adversely affected by l-cysteine hydrochloride in IsoVitaleX (4-fold increase in [minimal inhibitory concentration] MIC50; 0.06 versus 0.25 microg/mL). The rank order of potency of the antimicrobials for the entire collection was ceftriaxone (MIC90, 0.06 microg/mL) > faropenem (0.25 microg/mL) > azithromycin (0.5 microg/mL) > cefuroxime (1 microg/mL) > tetracycline (2 microg/mL) > penicillin = ciprofloxacin = levofloxacin (4 microg/mL). Using MIC90 for comparison, faropenem was 4-fold more potent than cefuroxime (0.25 versus 1 microg/mL), but was 4-fold less active than ceftriaxone (0.25 versus 0.06 microg/mL). Although the activity of faropenem was not affected by either penicillinase production (MIC90, 0.12 microg/mL, penicillinase-positive) or increasing ciprofloxacin MIC (0.25 microg/mL, ciprofloxacin-resistant), increasing penicillin MIC was associated with an increase in MIC90 values (0.016 microg/mL for penicillin-susceptible to 0.25 microg/mL for penicillin-resistant strains). Among the recent (2004) clinical gonococcal isolates tested, reduced susceptibility to penicillins, tetracycline, and fluoroquinolones was high (28.0-94.2%). Geographic distribution of the endemic resistance rates of gonococci varied considerably, with 16.7-66.7% of the gonococcal isolates being ciprofloxacin-resistant in Oregon, California, Washington, and Hawaii. Faropenem retained its potency against these recent clinical strains and also quinolone-resistant strains from Japan (MIC90, < or =0.25 microg/mL). In summary, the excellent activity of faropenem against the gonococcal strains analyzed irrespective of the resistance phenotype, along with its beta-lactamase stability, makes it an ideal contender for further development as an oral beta-lactam agent to treat uncomplicated gonococcal infections due to strains emerging with resistant to penicillins, tetracyclines, and fluoroquinolones.

Cultivation of Neisseria gonorrhoeae in liquid media and determination of its in vitro susceptibilities to quinolones

The cultivation of Neisseria gonorrhoeae by use of fastidious broth (FB) was evaluated. FB was found to be able to support the growth of all N. gonorrhoeae strains tested in this study without a rapid decrease in the viable count after exponential growth. After 24 h of incubation at 35 degrees C with 5% CO(2), viable counts of all strains reached over 10(8) CFU/ml in FB. Similar growth of the wild-type strain and its target-altered quinolone-resistant derivatives was observed. The susceptibilities of laboratory-adapted strains and clinical isolates to quinolones were tested by the microdilution method using FB. The MICs determined by microdilution were not significantly different from those determined by the agar dilution method recommended by the CLSI (formerly National Committee for Clinical Laboratory Standards). Moreover, the concentration-dependent time-kill of quinolones such as gatifloxacin and ciprofloxacin was observed in FB. At 2 to 4 times the MIC, gatifloxacin and ciprofloxacin were predominantly bactericidal against N. gonorrhoeae WHO A. At the MIC, the activities of both quinolones ranged from bactericidal to bacteriostatic. At 0.25 to 0.5 times the MIC, gonococcal growth was comparable to that of the growth control. These results suggest that the cultivation of N. gonorrhoeae by use of FB may be useful for evaluation of the antibacterial effects of quinolones.