Epidemiology of penicillin-resistant Neisseria gonorrhoeae isolated in Taiwan, 1960-1990

Changes in the six most common sequence types of Neisseria gonorrhoeae, including ST4378, identified by surveillance of antimicrobial resistance in northern Taiwan from 2006 to 2013

BACKGROUND

There has been no longitudinal study of drug susceptibility in Neisseria gonorrhoeae in Taiwan since 2006.

METHODS

We collected 1090 gonococcal isolates from Taipei City Hospital, Taiwan from April 2006 to August 2013. We used a disk diffusion assay to determine the susceptibility to five antibiotics and an E-test to determine the minimum inhibitory concentrations for cefixime and ceftriaxone in isolates with resistance. Neisseria gonorrhoeae-multi Antigen Sequence Typing and DNA sequencing of the por and tbpB genes were used to identify sequence types.

RESULTS

Among the 1090 isolates, the resistances to penicillin, ciprofloxacin, cefpodoxime, cefixime, and ceftriaxone were 61.01%, 83.39%, 9.63%, 6.70%, and 2.39%, respectively. The highest minimum inhibitory concentrations of cefixime and ceftriaxone were 0.19 mg/L and 0.50 mg/L, respectively. There were 327 sequence types. The four most common sequence types in homosexuals were ST4378, ST359, ST4654, and ST547; the two most common sequence types in heterosexuals were ST421 and ST419. Each of these sequence types had more than 25 isolates. There were significant differences in the sequence types in patients with different sexual orientations (p < 0.001).

CONCLUSION

Oral cefixime or ceftriaxone injections were used as first-line drugs for the treatment of gonorrhea from 2006 to 2013 because gonorrhea isolates had low minimum inhibitory concentrations for these two drugs. The abrupt emergence of ST4378 (closely related to the notorious ST1407) since 2009 is a cause for alarm. Changes in sexual behavior, including an increase in sexual activity without the use of condoms, may have contributed to the peak in gonorrhea in 2010. Further molecular epidemiological investigations are required.

Antimicrobial susceptibility of Neisseria gonorrhoeae isolates determined by the agar dilution, disk diffusion and Etest methods: comparison of results using GC agar and chocolate agar

Although the use of GC agar for determining Neisseria gonorrhoeae antimicrobial susceptibilities is suggested by Clinical and Laboratory Standard Institute (CLSI) guidelines, chocolate agar is still used in some regions owing to its low cost and availability. To determine the differences in susceptibilities determined using GC and chocolate agars, 163 non-duplicate N. gonorrhoeae isolates were tested. Minimum inhibitory concentrations (MICs) and percent susceptibilities determined using the GC agar dilution method, respectively, were as follows: ceftriaxone, 0.004-0.125 mg/L, 100%; cefixime, 0.002 mg/L to >32 mg/L, 98.2%; and ciprofloxacin, 0.002 mg/L to >32 mg/L, 3.1%. Comparison of ceftriaxone MICs determined by the Etest using GC agar and chocolate agar showed that use of GC agar tended to result in lower MICs than GC agar dilution, whilst use of chocolate agar tended to result in higher MICs (concordance, 55.8% and 82.8%, respectively). Disk inhibition zones obtained using GC agar and chocolate agar (and their correlation coefficients) were, respectively: ceftriaxone, 35-55 mm and 25-50mm (0.46); ciprofloxacin, 6-55 mm and 6-43 mm (0.84); and penicillin, 6-47 mm and 6-50 mm (0.93). Use of chocolate agar with the disk diffusion method for ceftriaxone was associated with a 5.5% false resistance rate. In summary, compared with GC agar, susceptibility testing using chocolate agar tends to yield higher MICs with the Etest and smaller disk inhibition zones with disk diffusion methods. Clinical microbiology laboratories should strictly adhere to CLSI recommendations by using GC agar instead of chocolate agar when performing susceptibility testing for N. gonorrhoeae.

High prevalence of ciprofloxacin-resistant Neisseria gonorrhoeae in Northern Taiwan

Among 55 preserved isolates collected in northern Taiwan from 1999 through 2003, ciprofloxacin resistance (minimum inhibitory concentration, >or=1 microg/mL) was found in 1 (25%) of 4 isolates obtained in 1999-2000 and in 27 (93.1%) of 29 isolates obtained in 2003. Pulsed-field gel electrophoresis analysis indicated that several clones predominated among the ciprofloxacin-resistant isolates.

Antibiotic usage in primary care units in Taiwan after the institution of national health insurance

To understand antibiotic usage in primary care units in Taiwan after the institution of national health insurance, we collected all prescriptions for one week in March each year from 1996 to 1999 from out-patient clinics of randomly sampled public health stations located in various parts of Taiwan. We sampled 114 health stations with 40,891 patient-visits and 68,386 diagnoses made in 1996; 154 health stations were sampled with 53,992 patient-visits and 99,466 diagnoses in 1997; 166 health stations were sampled with 49,112 patient-visits and 96,161 diagnoses in 1998; and 162 health stations were sampled with 46,976 patient-visits and 93,641 diagnoses in 1999. The percentages of total patient-visits that resulted in antibiotic treatment were 14.2%, 12.5%, 14.1% and 13.0% in the four time periods, respectively. Among patient-visits, patient group under the age of 11 received the highest percentage of antibiotic treatment. Common cold was the most frequent diagnosis for which antibiotic was prescribed during the four time periods, accounting for 32.3% of total antibiotic prescriptions. Among patients with the diagnosis of common cold, 31.3% received antibiotic treatment, and the highest figure was among pediatric patients (<16 year of age). Penicillins, cephalosporins and macrolides were the most commonly prescribed classes of antibiotics. They accounted for 35.4%, 26.5% and 21.6% of all prescribed antibiotics in these four study periods. From this study, it was found that, after institution of the national health insurance system, antibiotics are still very commonly used in primary care units in Taiwan and still seem to be overused.

Gonococcal meningitis and intra-abdominal abscess in the presence of a ventriculoperitoneal shunt

We report a case of gonococcal meningitis with an intraabdominal abscess in a 19-y-old woman, who had a ventriculoperitoneal shunt after craniotomy for astrocytoma. Percutaneous drainage was performed for the intraabdominal abscess. Ceftriaxone was administered with the ventriculoperitoneal shunt removal. The clinical course improved, but visual impairment last for 3 months following treatment.

A multiplex polymerase chain reaction to differentiate beta-lactamase plasmids of neisseria gonorrhoeae

In penicillinase-producing Neisseria gonorrhoeae (PPNG), resistance to penicillin may be mediated by one of several related plasmids of different sizes. These include the Asian, African and Rio/Toronto plasmids. Identification of these plasmids provides useful epidemiological information, but has necessitated plasmid purification and gel analysis. We have developed a rapid, simple multiplex polymerase chain reaction (PCR) which discriminates between the beta-lactamase resistance plasmids that are frequently found in strains of N. gonorrhoeae. Amplicons of 1191, 958 and 650 bp were produced from strains containing the African, Asian and Rio/Toronto plasmids, respectively, whilst no products resulted from non-PPNG strains harbouring the cryptic, conjugative or tetracycline resistance plasmids. PCR analysis of 123 strains of PPNG identified 60 strains with African, 16 strains with Asian and 47 strains with Rio/Toronto plasmids and showed complete agreement with the standard plasmid analysis.

High prevalence of antibiotic resistance of common pathogenic bacteria in Taiwan. The Antibiotic Resistance Study Group of the Infectious Disease Society of the Republic of China

We analyzed the antimicrobial susceptibilities of all clinical isolates of 14 common pathogenic bacteria recovered from patients in eight medical centers in Taiwan during 1995 and 1996. Susceptibility to commonly used antimicrobial agents was tested by the disk diffusion method as recommended by the National Committee for Clinical Laboratory Standards. Of the Staphylococcus aureus isolates, 59.3% and 62% were oxacillin-resistant in 1995 and 1996, respectively, whereas 63.2% of the coagulase-negative staphylococci isolates during the study period were oxacillin-resistant. The rate of penicillin-resistance among Streptococcus pneumoniae isolates was 39.7% in 1995 and 53.7% in 1996. Macrolide-resistance was found in 71.4%, 42.1%, and 46.7% of S. pneumoniae, beta-hemolytic streptococci, and viridans streptococci, respectively, in 1996. Less than 2% of the enterococcal isolates were vancomycin resistant, but 77% of them were gentamicin resistant. Resistance to gentamicin was also common in Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter baumannii. Various degrees of resistance to ampicillin, piperacillin, cephalosporins, aztreonam, and ciprofloxacin were detected in Enterobacteriaceae, P. aeruginosa, and A. baumannii. More than 55% of Haemophilus influenzae isolates were ampicillin resistant. In summary, resistance to many antimicrobial agents in various common pathogenic bacteria is very common in Taiwan. Our results implicate that antibiotic resistance in the developing countries need to be monitored closely.

Antibiotic usage in primary care units in Taiwan

To understand the situation of antibiotic usage in primary care units in Taiwan, we collected all prescriptions over a 1 week period during March 2 to March 7, 1992, December 2 to December 7, 1992, and January 14 to January 19, 1994 from out-patient clinics of public health stations located in various parts of Taiwan. In the first time period 60 health stations were sampled, 18,350 patient-visits made and 23,674 diagnoses recorded. In the second time period 168 health stations were sampled, 84,143 patient-visits made and 96,528 diagnoses recorded. In the third time period 173 health stations were sampled with 85,623 patient-visits and 105,132 diagnoses recorded. The percentages of total patient-visits that resulted in antibiotic treatment were 16.7, 13.5 and 12.4% in the three time periods, respectively. The patient group under the age of 11 received the highest percentage of antibiotic treatment. The percentage of patient-visits that resulted in treatment with two or more types of antibiotics decreased from 25.4% in March, 1992 to 13.2% in January, 1994. Common cold was the most frequent diagnosis in patients receiving antibiotic therapy during the three time periods and accounted for 36.9% of total antibiotic prescriptions. Of the patients with the diagnosis of common cold, 29.7% received antibiotic treatment, of whom the largest group were paediatric patients (< 16 years). Penicillins, macrolides and cephalosporins were the most commonly prescribed antibiotics and accounted for 34.0, 21.8 and 21.3% of all prescribed antibiotics in the three study periods.

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.

Genomic homogeneity of the AHU/IA-1,2 phenotype of Neisseria gonorrhoeae during its disappearance from an urban population

BACKGROUND

Isolates of Neisseria gonorrhoeae requiring arginine, hypoxanthine, and uracil (AHU) appeared in Denmark in 1946, were preponderant in Seattle during the 1970s, were associated with disseminated gonococcal infections (DGI), and were primarily of the IA-1,2 serovar.

GOALS

To investigate the disappearance of the AHU/IA-1,2 phenotype and to examine by pulsed-field gel electrophoresis (PFGE) the genomic homogeneity of this unique phenotype isolated from Seattle-King County during the past decade.

STUDY DESIGN

This retrospective study used data extracted from previous publications for the period 1971 through 1984, and from existing records at the Neisseria Reference Laboratory, University of Washington for the period 1985 through 1996. Samples (n = 68) of AHU/IA-1,2 isolates from 1984 to 1985 and 1988 to 1993 were analyzed using endonucleases NheI and XbaI. For comparison, 10 AHU/IB isolates were included in the study.

RESULTS

AHU isolates, predominantly IA-1,2 strains accounted for 52% of the gonococcal isolates for the period 1971 through 1974, 40% for 1974 through 1976, 16% for 1984, and then declined from 7% in 1986 to 0% for each of the last 3 years, 1994 through 1996. Isolates with < or = 1 band difference after digestion with either NheI or XbaI were considered to belong to a single closely related pattern. Pulsed-field gel electrophoresis (PFGE) type designation was made from the combination of NheI and XbaI patterns. These criteria yielded 5 NheI and 8 XbaI PFGE patterns, and 11 PFGE types based on the combination of NheI and XbaI pattern. The most frequently occurring NheI and XbaI patterns accounted for 74% and 57% of isolates, respectively. One type persisted throughout the decade and accounted for 54% of the 68 isolates. Analysis of the 10 AHU/IB isolates yielded 7 NheI and 8 XbaI patterns that gave 9 types that were distinct from the types found in the AHU/IA-1,2 strains.

CONCLUSION

The AHU/IA-1,2 phenotype first documented 50 years ago in Denmark still shows a high degree of genomic homogeneity during the past decade in Seattle. The implementation of screening, decreased rates of sexual exposure in the acquired immune deficiency syndrome era, or other factors may explain its apparent elimination in Seattle-King County.

Agar dilution method for susceptibility testing of Neisseria gonorrhoeae

The antibiotic susceptibilities of Neisseria gonorrhoeae isolates obtained from patients attending a clinic for sexually transmitted diseases in Tucumán, Argentina, were determined by the agar dilution method (MIC). 3.5% of the isolates produced beta-lactamase. A total of 96.5% of beta-lactamase negative isolates tested were susceptible to penicillin (MIC < or = 2 micrograms/ml-1); 14.03% of the tested isolates were resistant to tetracycline (MIC < or = 2 micrograms/ml-1), and 98% of the tested isolates were susceptible to spectinomycin (MIC < or = 64 micrograms/ml-1). The MICs for 95% of the isolates, tested for other drugs were: < or = 2 micrograms/ml-1 for cefoxitin, < or = 0.06 microgram/ml-1 for cefotaxime, < or = 0.25 microgram/ml-1 for norfloxacin, < or = 10 micrograms/ml-1 for cephaloridine, < or = 10 micrograms/ml-1 for cephalexin, and < or = 50 micrograms/ml-1 for kanamycin. Antibiotic resistance among N. gonorrhoeae isolates from Tucumán, Argentina, appeared to be primarily limited to penicillin and tetracycline, which has been a general use against gonorrhoeae in Tucumán since 1960. Periodic monitoring of the underlying susceptibility profiles of the N. gonorrhoeae strains prevalent in areas of frequent transmission may provide clues regarding treatment options and emerging of drug resistance.

Epidemiology of penicillin-resistant Neisseria gonorrhoeae in Frankfurt, Germany

In the present study 150 Neisseria gonorrhoeae strains from prostitutes in Frankfurt, Germany, were investigated for their in vitro susceptibility to eight antimicrobial agents by the agar dilution test. While 21.3% of gonococci were highly resistant to penicillin (MICs > or = 2 mg/l), 49.4% of the organisms were moderately sensitive (MICs = 0.125-0.5 mg/l) and only 29.3% of strains were fully susceptible to penicillin (MICs < or = 0.06 mg/l). No resistance to other antibiotics tested was observed, with the exception of doxycycline, to which overall resistance was 9.7%. Genotypic analysis of Neisseria gonorrhoeae by the restriction enzyme technique showed that most penicillin-resistant strains could be grouped into two main bacterial clones, whereas penicillin-susceptible isolates displayed a remarkable heterogeneity. This observation suggests that a restricted number of resistant Neisseria gonorrhoeae strains are likely to spread within the prostitute population of Frankfurt, Germany.

Emergence of in vitro resistance to fluoroquinolones in Neisseria gonorrhoeae isolated in Japan

To investigate emerging fluoroquinolone resistance in Neisseria gonorrhoeae isolated in Japan, we compared the in vitro antimicrobial susceptibilities of 79 gonococcal isolates from 1992 through 1993 to 14 fluoroquinolones and 14 other antibiotics with those of 27 isolates from between 1981 and 1984. The MICs at which 90% of the isolates were inhibited by nine fluroquinolones, including norfloxacin, enoxacin, ofloxacin, ciprofloxacin, tosufloxacin, lomefloxacin, fleroxacin, levofloxacin, and sparfloxacin, for isolates from 1992 to 1993 were 8- or 16-fold higher than those for isolates from 1981 to 1984. Furthermore, the MICs at which 90% of the isolates were inhibited by five fluroquinolones, including OPC-17116, T-3761, DU-6859a, AM-1155, and Q-35, that have recently been synthesized but have not yet been introduced for clinical use in Japan for isolates from 1992 to 1993 were also 2- to 16-fold higher than those for isolates from 1981 to 1984. The gonococcal isolates from 1992 to 1993 showed no significant decreases in susceptibility to beta-lactams, tetracyclines, macrolides, and spectinomycin, compared with those for isolates from 1981 to 1984. Our data indicate that the incidence of gonococcal strains with decreased susceptibilities to fluoroquinolones is increasing in Japan.

Rapid decline in penicillinase-producing Neisseria gonorrhoeae in Hong Kong associated with emerging 4-fluoroquinolone resistance

OBJECTIVE--To study the changes in penicillinase-producing (PPNG) and high-level tetracycline resistant (TRNG) Neisseria gonorrhoeae isolated in Hong Kong associated with emerging quinolone resistance (QRNG) over a two year period from November 1992 to October 1994. MATERIALS AND METHODS--Four thousand and eighty-six strains of Neisseria gonorrhoeae isolated, of which 432 were PPNG, were examined for susceptibilities to penicillin and tetracycline by an agar dilution method using the breakpoint minimum inhibitory concentrations (MICs) of 1 and 10 mg/1 respectively. Ofloxacin susceptibility was done using 0.1 and 1 mg/l. Penicillinase production was detected by performing the chromogenic cephalosporin nitrocefin test on all penicillin resistant (MIC > 1 mg/l) strains. RESULTS--Three thousand and eighty (75.4%) and 79 (1.9%) strains were found to be penicillin resistant and TRNG (MIC > 10 mg/l) respectively. Sixty-nine strains (1.7%) were resistant to both, of which 54 (1.3%) were PPNG. Three strains were multiply-resistant to penicillin, tetracycline and ofloxacin; however, none was PPNG. While the percentage of penicillin resistant strains remained stable (mean 75.5%, SD 7.0), TRNG decreased from 4.5% to 2.1%. The most dramatic change was the sharp decline of PPNG from 25.5% in January 1993 to 4.3% in October 1994, concurrent with a linear increase in strains with ofloxacin MIC > 0.1 mg/l. Significant clinical failure was seen in strains having ofloxacin MIC > 1 mg/l (QRNG), which increased drastically from 0.5% to 10.4% during the study period. Selection against PPNG and TRNG strains appeared to occur only when fully quinolone-susceptible strains first become less susceptible (MIC > 0.1 mg/l), but not when these less susceptible strains become fully resistant (MIC > 1 mg/l). CONCLUSION--PPNG is now no longer hyperendemic in Hong Kong. Emergence of QRNG is associated with rapid decline of both PPNG and TRNG. This is the first report of plasmid-curing effect of the 4-fluoroquinolones occurring on an ecological scale.

Reduced uptake and accumulation of norfloxacin in resistant strains of Neisseria gonorrhoeae isolated in Japan

OBJECTIVE

To investigate the alteration of cell permeability toward fluoroquinolones in Neisseria gonorrhoeae, which is a major quinolone-resistance mechanism along with the alteration of DNA gyrase in gram-negative bacteria. The prevalence of fluoroquinolone-resistant N gonorrhoeae strains is rapidly increasing in Japan.

MATERIALS AND METHODS

The uptake and accumulation of norfloxacin by gonococcal cells, including six clinical and five World Health Organization (WHO) reference strains, were measured. Of the six clinical strains, two were highly resistant to norfloxacin (MIC 8.0 and 4.0 micrograms/ml), two were moderately resistant (MIC 1.0 and 0.5 microgram/ml), and two were sensitive (MIC 0.063 and 0.004 microgram/ml). All five WHO reference strains were sensitive to norfloxacin (MIC < or = 0.001 to 0.063 microgram/ml).

RESULTS

Mean initial norfloxacin uptake in the four resistant strains (104 ng/mg of dry cells) was significantly lower than that in the seven sensitive strains (158 ng/mg of dry cells) (p < 0.05). The mean uptake after 20 minutes was also significantly lower in the four resistant strains (130 ng/mg of dry cells) than in the seven sensitive strains (194 ng/mg of dry cells) (p < 0.05). However, there was no significant difference in mean norfloxacin accumulation after 20 minutes between the four resistant strains (26 ng/mg of dry cells) and the seven sensitive strains (36 ng/mg of dry cells). The accumulation of norfloxacin after 20 minutes was almost zero in two of the four resistant strains, while the remaining two strains accumulated norfloxacin as well as the sensitive strains.

CONCLUSIONS

These findings suggest that alteration of bacterial cell permeability is a quinolone-resistance mechanism in N gonorrhoeae isolated in Japan, and that this bacteria may exhibit other mechanisms such as alteration of DNA gyrase.

High prevalence of Neisseria gonorrhoeae strains with reduced susceptibility to fluoroquinolones in Japan

OBJECTIVE

To study the antibiotic susceptibility of Neisseria gonorrhoeae strains isolated in Japan and, in particular, to examine the possibility of emerging fluoroquinolone resistance.

MATERIALS AND METHODS

Sixty-nine strains of Neisseria gonorrhoeae isolated in 1992 were tested for susceptibility to 15 antibiotics including fluoroquinolones and were seroclassified. Twenty-seven strains isolated from 1981 to 1984 were also evaluated as controls.

RESULTS

The MIC90 values of norfloxacin, ofloxacin, and ciprofloxacin against the isolates from 1992 were 2.0, 1.0, and 0.5 microgram/ml, respectively. The MIC90 values of norfloxacin, ofloxacin, and ciprofloxacin against the isolates from 1981-84 (controls) were 0.25, 0.125, and 0.063 microgram/ml, respectively. These results indicate that the MIC90 values of norfloxacin, ofloxacin, and ciprofloxacin against the strains from 1992 were 8-fold higher than those against the strains from 1981-84. However, there were no significant differences in susceptibility to beta-lactams, tetracyclines, macrolides, and spectinomycin between the isolates from 1992 and those from 1981-84. The majority of the isolates belonged to the WII/WIII serogroup. There was no relationship between fluoroquinolone resistance and serogroup.

CONCLUSIONS

Fluoroquinolones have been used frequently as first-line therapy and have provided excellent clinical efficacy for gonococcal infections for the last several years in Japan. However, our data indicate that a rapid decrease in the susceptibility of Neisseria gonorrhoeae to fluoroquinolones is occurring in our country.