Penicillinase-producing Neisseria gonorrhoeae in Dade County, Florida: phenotypic characterization of isolates from 1983, 1984, and 1986

Gonococcal susceptibility to antimicrobials in Baltimore, 1988-1994. What was the impact of ciprofloxacin as first-line therapy for gonorrhea?

BACKGROUND

Single-dose, oral quinolones have been a recommended treatment option for gonorrhea since 1989 and have since been used as first-line therapy for gonorrhea in Baltimore.

METHODS

The impact of this strategy on antimicobial susceptibility patterns in Neisseria gonorrhoeae was assessed utilizing data collected as part of the National Gonococcal Isolate Surveillance system. This system evaluates a systematically collected sample. Minimum inhibitory concentrations to penicillin, tetracycline, ceftriaxone, and ciprofloxacin were determined by agar dilution.

RESULTS

Between January 1988 and September 1994, 1,846 gonococcal isolates were evaluated. The proportion of isolates with plasmid-mediated resistance (penicillinase-producing Neisseria gonorrhoeae or tetracycline-resistant Neisseria gonorrhoeae) increased from 22% in 1988 to 46% in 1992 and then dropped to 20% in 1994. In contrast, the prevalence of chromosomally mediated resistant isolates ranged between 3% and 10%. Between 1988 and 1994, the geometric mean penicillin and tetracycline minimum inhibitory concentrations decreased slightly (penicillin: from 0.509 microgram/ml to 0.369 microgram/ml; tetracycline: from 1.01 micrograms/ml to 0.767 microgram/ml). The mean ceftriaxone MIC increased from 0.005 microgram/ml in 1988 to 0.021 microgram/ml in 1992, and then abruptly decreased. Ciprofloxacin minimum inhibitory concentrations did not change substantially during the study period. Concurrent studies performed in this community suggest that quinolones were infrequently used for infections other than sexually transmitted ones during this time period.

CONCLUSIONS

Single-dose quinolone therapy does not appear to foster development of resistant gonococcal isolates. However, resistance may develop as a result of complex ecological interactions with the community, underscoring the need for continued surveillance.

Susceptibility of Neisseria gonorrhoeae associated with pelvic inflammatory disease to cefoxitin, ceftriaxone, clindamycin, gentamicin, doxycycline, azithromycin, and other antimicrobial agents

We determined the susceptibilities, by the agar dilution method, of 84 recent clinical isolates of Neisseria gonorrhoeae obtained from women with pelvic inflammatory disease in the United States to the following antimicrobial agents: penicillin, cefoxitin, cefotetan, ceftriaxone, ceftizoxime, cefixime, tetracycline, doxycycline, ciprofloxacin, ofloxacin, erythromycin, azithromycin, clindamycin, and gentamicin. Twenty-five percent of the isolates were resistant to penicillin and 20% were resistant to tetracycline. In comparison, doxycycline was more active than tetracycline and azithromycin was more active than erythromycin in vitro. Ceftriaxone, ceftizoxime, and cefixime were equally active against penicillin-susceptible isolates, but they had different in vitro activities against gonococcal isolates possessing chromosomally mediated resistance to penicillin. Overall, cefoxitin was slightly more active than cefotetan and ciprofloxacin was more active in vitro than ofloxacin, especially against N. gonorrhoeae with chromosomally mediated resistance. Criteria for the interpretation of susceptibility data for N. gonorrhoeae are not available for clindamycin or gentamicin, but for at least half of all isolates, including penicillin-susceptible isolates, at least 4 micrograms of clindamycin or gentamicin per ml was required to inhibit growth in vitro.

Antimicrobial susceptibilities of Neisseria gonorrhoeae strains representing five distinct resistance phenotypes

The susceptibilities of 109 strains of Neisseria gonorrhoeae to penicillin G, tetracycline, amoxicillin-clavulanic acid, cefotetan, cefoxitin, ceftriaxone, ciprofloxacin, and fleroxacin were determined. The activities of cefmetazole, cefuroxime, cefixime, and ofloxacin were also determined against 62 of these strains. Strains represented penicillin-susceptible (Pen(s)) N. gonorrhoeae; penicillinase-producing N. gonorrhoeae (PPNG) possessing 2.9-, 3.05-, 3.2-, or 4.4-MDa beta-lactamase plasmids; strains with high-level, plasmid-mediated tetracycline resistance (TRNG); strains with plasmid-mediated resistance to penicillin and tetracycline; and strains with chromosomally mediated resistance to penicillin and tetracycline (CMRNG). Ceftriaxone, cefixime, and ciprofloxacin were the most active agents tested against all strains. Pen(s), TRNG, and PPNG strains possessing a 3.2-MDa beta-lactamase plasmid were more susceptible to amoxicillin-clavulanic acid, extended- and broad-spectrum cephalosporins, and quinolones than were either PPNG strains possessing a 2.9-, a 3.05-, or a 4.4-MDa beta-lactamase plasmid or CMRNG strains.

Penicillinase producing Neisseria gonorrhoeae from St Thomas' Hospital 1976-1990--the first fifteen years

OBJECTIVE

To examine the penicillinase producing N. gonorrhoeae (PPNG) collected at St Thomas' Hospital from 1976-1990 and, by determination of antibiotic susceptibility pattern and application of three typing methods, examine the prevalence of different gonococcal types. Also to determine whether there is any relationship between antibiotic sensitivity, plasmid profile, auxotype and serovar.

MATERIALS AND METHODS

A total of 665 isolates of PPNG from patients attending the Department of Genitourinary Medicine at St Thomas' Hospital were characterised by antibiotic MIC, plasmid profile, auxotyping and serotyping.

RESULTS

Penicillin MICs for 85% of all isolates were between 0.25 and 32 mg/l. The MIC of tetracycline for 60-80% of the isolates was < 1 mg/l. A small number of isolates had tetracycline MICs of 32 mg/l but MICs > 32 mg/l were not seen. Over 90% of the isolates were sensitive to the remaining three antibiotics tested, erythromycin, cefuroxime and spectinomycin. The 3.2 or 4.4 MDa plasmid with or without the 24.5 MDa conjugal plasmid was seen in all isolates until 1989/90 when a 2.9 MDa beta-lactamase encoding plasmid and the 25.2 MDa plasmid mediating tetracycline resistance were also recognised. Ninety-nine percent of all isolates belonged to one of four auxotypes, prototrophic, arginine, proline or proline/arginine requiring. An initial predominance of isolates with the 1A outer membrane protein was reversed in 1982 and 1B has remained predominant. Thirty two different serovars were identified among the 665 isolates, 14 belonged to serogroup 1A and 18 to 1B, and the eight most common accounted for 83.9% (554) of all isolates. Analysis of the results of combined typing methods showed there was an association between antibiotic resistance, plasmid profile and serogroup. The number of auxotypes and serovars detected in the collection, indicates the possibility that PPNG have been introduced from abroad or outside our local population.

CONCLUSION

Temporal trends in the distribution of auxotype/serovar classes show that the total population of PPNG isolates is formed by a heterogenous mixture in which certain auxotype/serovar classes appear, disappear and may re-emerge. Others were present throughout in small numbers.

Antimicrobial susceptibility testing of Neisseria gonorrhoeae and implications for epidemiology and therapy

Antimicrobial susceptibility testing (AST) of Neisseria gonorrhoeae has been under development since the early days of antimicrobial agents. However, it is rarely applied to clinical isolates today. The history of the various in vitro tests to determine the susceptibility of N. gonorrhoeae to antibiotics is rich with evidence that these results predict response to therapy for almost all agents tested. Further, AST is a useful and important aspect of strain characterization and disease epidemiology in conjunction with the more specific but laborious techniques of auxotyping, serotyping, and plasmid analysis. Current technology has overcome many of the objections to AST for N. gonorrhoeae with standardization of test media and the development of an accurate disk diffusion AST method that is suited to most clinical laboratories regardless of volume or level of technical expertise. Ironically, the very low level of resistance to the current primary treatment strategy in the United States, ceftriaxone or another potent cephalosporin, makes the use of AST somewhat superfluous.

Correlation between in vitro antimicrobial susceptibilities and beta-lactamase plasmid contents of isolates of Haemophilus ducreyi from the United States

We determined the susceptibilities of 94 strains of Haemophilus ducreyi isolated in various municipalities in the United States between 1982 and 1989 to the following antimicrobial agents: amoxicillin-clavulanic acid, ceftriaxone, erythromycin, azithromycin, ciprofloxacin, ofloxacin, trimethoprim, and spectinomycin. Ceftriaxone (MIC, less than or equal to 0.008 micrograms/ml), azithromycin (MIC, less than or equal to 0.125 micrograms/ml), erythromycin (MIC, less than or equal to 0.125 micrograms/ml), ciprofloxacin (MIC, less than or equal to 0.25 micrograms/ml), and ofloxacin (MIC, less than or equal to 0.25 micrograms/ml) were highly active against all isolates. Amoxicillin-clavulanic acid (MICs, 0.25 to 8.0 micrograms/ml), trimethoprim (MICs, 0.06 to 16.0 micrograms/ml), and spectinomycin (MICs, 2.0 to greater than or equal to 32.0 micrograms/ml) were less active against these isolates. Isolates possessing the 5.7-MDa beta-lactamase plasmid were less susceptible to erythromycin, trimethoprim, and spectinomycin than were isolates possessing the 3.2-MDa beta-lactamase plasmid. The susceptibilities of plasmidless isolates to erythromycin, trimethoprim, and spectinomycin were distributed bimodally; the median MIC for the more susceptible plasmidless isolates corresponded to that for isolates with the 3.2-MDa plasmid, and the median MIC for the less susceptible plasmidless isolates corresponded to that for isolates with the 5.7-MDa plasmid. Thus, plasmid profiles may be valuable markers for geographical variations in antimicrobial susceptibilities of H. ducreyi strains that may indicate the relative efficacy of regimens for the treatment of chancroid. Of the regimens recommended by the U.S. Public Health Service for the treatment of chancroid, our results support the use of erythromycin, ceftriaxone, and ciprofloxacin, and perhaps ofloxacin, but suggest that amoxicillin-clavulanic acid and sulfamethoxazole-trimethoprim should be used with caution.

Current status of serotyping of Neisseria gonorrhoeae

Protein I has become the basis of serotyping of N. gonorrhoeae. A panel of 12 anti-protein I monoclonal antibodies is supplied by Syva Company, Palo Alto, CA, through distributors for research purposes only. These distributors are responsible for storing the monoclonal antibodies, supplying research groups and training new users, particularly in the interpretation of coagglutination reactions. A European Workshop was held in Heidelberg, Federal Republic of Germany in July 1988 to discuss serotyping with these antibodies. The current uses of serotyping of N. gonorrhoeae include epidemiological studies, clinical purposes and surveillance of antibiotic resistance and plasmid carriage. Predominant serovars may be subtyped either by additional antibodies or with the use of another technique, such as auxotyping, determination of antibiotic sensitivities, plasmid analysis or genetic fingerprinting. Conversely, there is growing evidence that it may be appropriate to group certain serovars together. Data collected during prevalence studies could be combined with clinical information and an international data bank set up. This supposes a close future collaboration of all groups involved in the epidemiology of N. gonorrhoeae.