Diagnosis of gonorrhoea by culture on a selective medium containing vancomycin, colistin, nystatin and trimethoprim (VCNT). A comparison with Gram-staining and immunofluorescence

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.

Laboratory methods in genitourinary medicine. Methods of diagnosing gonorrhoea

Gonorrhoea is normally diagnosed presumptively by the presence of intracellular Gram-negative cocci on a Gram stain and confirmed by culture of the causative organism, Neisseria gonorrhoeae. Alternative methods have been evaluated extensively for the detection of gonococci in clinical specimens including immunological techniques such as ELISA and immunofluorescence, DNA probes, genetic transformation and the limulus lysate assay. Some of these tests have proved as sensitive and specific for the detection of gonorrhoea in symptomatic men as the Gram stain but offer no advantage in time or cost. In women, no test has been found that shows a sensitivity and specificity sufficiently adequate for clinical use. Culture in men and women remains the method of choice for diagnosis. In addition the need to obtain the infecting organism for antibiotic susceptibility testing has not been overcome. In contrast, the rapid identification of N gonorrhoeae can be achieved within four hours using either monoclonal antibodies or by the detection of preformed enzymes. New methods for both the detection and identification of N gonorrhoeae should be carefully evaluated particularly for use in cases of child and sexual abuse where medico-legal problems may arise.

Ciprofloxacin for treating urethral gonorrhoea in men

The effectiveness of a single oral dose of ciprofloxacin in eradicating urethral gonorrhoea was assessed in 18 men who received 250 mg and 26 men who were given 100 mg. All patients, including two infected with beta lactamase (penicillinase) producing strains of Neisseria gonorrhoeae (PPNG), were cured. The drug had no effect on infection with Chlamydia trachomatis or on the incidence of post gonococcal urethritis. Ciprofloxacin may be useful in patients hypersensitive to penicillins and cephalosporins, and the drug may also be useful in urethral gonorrhoea caused by PPNG strains.

Comparison of econazole and isoconazole as single dose treatment for vaginal candidosis

In a single blind trial there was no significant difference between econazole (2 X 150 mg pessaries) and isoconazole (2 X 300 mg pessaries) given as a once only treatment for vaginal candidosis. Cure rates at 14 days were 70.4% for econazole and 77.6% for isoconazole, and at 28 days were 63.8% and 64.5% respectively. Though isoconazole was formulated for single dose usage, econazole was formulated for a regimen of one pessary a night for three nights.

Single dose ciprofloxacin for treating gonococcal infections in men

A single oral dose of ciprofloxacin 500 mg was used to treat five men with gonococcal urethritis and five men with gonococcal proctitis, and all were cured. In a subsequent study the dose of ciprofloxacin was reduced to 250 mg, and 54 men with 57 gonococcal infections (47 urethral, seven rectal, and three pharyngeal) were treated; of the isolates of Neisseria gonorrhoeae, four were penicillinase producing strains. All the patients were cured of gonococcal infection. Urethral specimens from nine of the men with gonococcal urethritis yielded Chlamydia trachomatis before treatment. These organisms were isolated again from all these patients seven days after treatment, and from a further seven men who had been chlamydia negative before treatment. It is concluded that a single oral dose of ciprofloxacin is an effective treatment for uncomplicated gonorrhoea, but is ineffective against C trachomatis. Of the 54 men given 250 mg ciprofloxacin, six (11%) showed minor abnormalities of liver function tests after treatment.

Two regimens of sultamicillin in treating uncomplicated gonorrhoea

Sultamicillin is a covalent union of ampicillin and the beta lactamase inhibitor, sulbactam (CP-45,899). Two studies were conducted to assess its efficacy in treating uncomplicated gonorrhoea. In the first study treatment comprised sultamicillin 1.5 g and probenecid 1 g; 124 (89.2%) of 139 patients responded including seven of 11 patients harbouring beta lactamase (penicillinase) producing strains of Neisseria gonorrhoeae (PPNG). In the second study sultamicillin 2.25 g and probenecid 1 g were given; 122 (93.8%) of 130 patients responded. Only two of seven pharyngeal infections resolved, and if pharyngeal infections are excluded the overall cure rate rose to 95.3%. Thirteen of 14 patients infected with PPNG strains were cured by the larger dose. Side effects were mild and transitory. It may be concluded that sultamicillin 2.25 g plus probenecid 1 g is an effective regimen to treat uncomplicated rectal and genital gonorrhoea and is useful for treating infections with PPNG strains. Most beta lactamase resistant antimicrobials must be given parenterally; sultamicillin is given by mouth.

Advantages of adding a course of tetracycline to single dose ampicillin and probenecid in the treatment of gonorrhoea

Chlamydia trachomatis was reisolated from 11 of 12 men with gonorrhoea who had initially yielded chlamydiae and who had been treated with ampicillin and probenecid (AMP) only, but from none of five such men treated with ampicillin and probenecid followed by tetracycline (AMPT). These results correlated with the absence of postgonococcal urethritis (PGU) in the group treated with AMPT. C trachomatis was isolated or reisolated from 20 of 25 women after treatment with AMP, compared with none of 14 women treated with AMPT. We recommend the addition of a course of tetracycline to the routine single dose treatment for gonorrhoea in men and women.

Imported penicillinase producing Neisseria gonorrhoeae becomes endemic in London

We review all cases of gonorrhoea caused by penicillinase producing Neisseria gonorrhoeae (PPNG) seen between 1976 and 1983 at the sexually transmitted disease (STD) clinic of this hospital, which accounted for 11% of all such cases reported in that period in the United Kingdom. While the overall incidence of gonorrhoea remained relatively stable in this clinic, that of PPNG rose to 4.4% of all such cases by 1982. Until last year, 75% of these cases were imported, mainly from Nigeria and Ghana, but a marked change was seen in the second half of 1982, when 71% of cases were indigenous in origin. Casual partners and prostitutes in London were mentioned as the source of infection by 34% of patients, a much higher percentage than that seen previously. Such sources are notoriously difficult to trace and these figures show a very disturbing trend. Although rectal infection tends to be asymptomatic, PPNG was isolated in rectal cultures from two of five homosexuals and 19 of 26 women. There is therefore a risk that PPNG could spread rapidly through the homosexual population. We suggest that spectinomycin should no longer be the first drug of choice in the treatment of gonorrhoea caused by PPNG but should be replaced by the newer cephalosporins.

Acquisition of new genes by oral Neisseria

It is suggested that part of the increased pharyngeal carriage of meningococci reported in patients with gonorrhoea is due to misidentification of gonococci which have been transformed to maltose fermenters by DNA from normal throat flora. The distribution of specific aminopeptidases in strains of gonococci, meningococci isolated from the throat and meningococci from systemic infections is consistent with this view. Gonococci oxidising maltose and gonococci with gamma-L-glutamyl aminopeptidase activity, both factors regarded as typical of Neisseria meningitidis, can be produced in vitro by transformation with DNA from N lactamica and N meningitidis. The clinical and theoretical implications of such changes are discussed.

Auxotypes and antibacterial resistance to gonococci with differing susceptibilities to vancomycin

The responses to vancomycin and 11 other antibacterial drugs and the nutritional requirements of gonococci recovered from two selective media were determined. Single urogenital specimens from 508 patients attending a social hygiene clinic in 1975 yielded 97 strains of Neisseria gonorrhoeae; 95 were recovered on VCNT (a modification of Thayer-Martin medium), always inoculated first, and 69 on LC medium containing lincomycin (4 micrograms/ml) and colistin (5 micrograms/ml). The two drugs at these concentrations in LC medium were not inhibitory for isolates from either medium. Unexpectedly, three isolates on VCNT were susceptible to vancomycin at the concentrations (3 micrograms/ml) in VCNT medium; these three were typically sensitive to penicillins but were hypersusceptible to erythromycin (inhibited by less than or greater than 0.05 micrograms/ml) and rifampin (less than or equal to 0.02 micrograms/ml). Resistance to streptomycin (greater than or equal to 500 micrograms/ml) (22% of the strains) was correlated with increased resistance to penicillins, erythromycin, and rifampin in most instances. All streptomycin-resistant gonococci required proline, or arginine, or none of the test compounds. Strains requiring arginine, hypoxanthine, and uracil were uniformly sensitive to antibiotics but not hypersusceptible. In contrast, six strains of N gonorrhoeae isolated in Denmark required arginine (not satisfied by ornithine), hypoxanthine, and uracil and were hypersusceptible to vancomycin (inhibited by 0.5 micrograms/ml), erythromycin, and rifampin. DNA-mediated transformation showed that all three hypersusceptibilities of one Danish strain were introduced together into a wild-type gonococcus, suggesting that a mutation of an env (envelope) locus might be responsible for the atypical permeability.

Rosaramicin and tetracycline in the treatment of non-gonococcal urethritis. A comparison of clinical and microbiological results

The clinical and microbiological outcome of the treatment of 94 men for uncomplicated non-gonococcal urethritis (NGU) was studied. Rosaramicin 250 mg six hourly for seven days was given to 46 men and tetracycline 250 mg six hourly for seven days to 48 men; the follow-up period was up to six weeks. Complete resolution of the clinical signs of infection was seen in 40 (87%) of the men treated with rosaramicin and in 37(77%) of those treated with tetracycline. Chlamydia trachomatis was eliminated from 17 of the 18 men treated with rosaramicin and from all of the 16 men treated with tetracycline. Ureaplasma urealyticum was eliminated from 12 of the 14 men treated with rosaramicin and from 15 of the 19 receiving tetracycline. Clinical recovery correlated well with the elimination of C trachomatis but less well with that of U urealyticum. The two antimicrobial agents were equally effective in the therapy of NGU, but gastrointestinal side effects were significantly more common in men treated with rosaramicin.

Inhibition of Neisseria gonorrhoeae isolates by Martin-Lewis medium. Epidemiology, susceptibility profile, and plasma analysis

A study was undertaken on the premise that if an increase of 1 microgram/ml in the concentration of vancomycin in Martin-Lewis medium (MLM) could improve inhibition of Gram-positive cocci, then a concomitant increase in the inhibition of gonococci could also occur. Isolates of Neisseria gonorrhoeae that failed to grow on MLM accounted for 18-5% of all positive culture results for gonorrhoea. The incidence of isolates susceptible to vancomycin was 14% and of those susceptible to trimethoprim 2.4%; one isolate was susceptible to both vancomycin and trimethoprim. The antibiotic-susceptible isolates were more frequently isolated from asymptomatic white men. Plasmid analysis showed that the 2.4-megadalton cryptic plasmic was absent in the vancomycin-susceptible isolates. The large proportion of isolates failing to grow on selective MLM has important clinical implications for the diagnosis of gonorrhea.

Assessment of transport and isolation methods for gonococci

Urethral discharge from men was diluted to give heavy and light inocula and cultured on seven different solid culture media, including two transport/isolation media, or held in three types of semi-solid transport medium for varying periods and then cultured. The amount of growth was quantitated and the performance of the different systems compared. Fresh non-selective media were best, with up to two failures in 254 cultures on each medium. With selective media there were 9-23 failures with heavy inocula and 22-47 failures with dilute inocula. For Transgrow or the Jembec system incubation before holding at ambient temperature was better than holding followed by incubation. Transport media yielded good results if cultures were set up within six hours; only minor losses occurred after 24 hours.

Assessment of a selective medium for the isolation of Neisseria gonorrhoeae

Specimens of urethral pus from 312 men with gonorrhoea were diluted and inoculated on to non-selective and selective media, the latter containing vancomycin, colistin, nystatin, and trimethoprim. Although three (1%) isolates of Neisseria gonorrhoeae were inhibited by trimethoprim 4 mg/1 and 10 by vancomycin 2 mg/1, only two failed to grow on a selective medium from large inocula but eight strains sensitive to vancomycin failed to grow on a selective medium from a light inoculum. These few failures do not appear to negate the value of the selective medium.

An assessment of the Microcult-GC culture test

Microcult-GC, a miniaturised culture test, was compared with an established selective culture method for laboratory confirmation of gonorrhoea. Microcult-GC correlated 94% with the control method in identifying gonococci in male urethral specimens. Microcult-GC testing of 130 gonococci-negative vaginal swabs gave only 4.6% false-positive oxidase results, which could probably have been readily refuted by Microcult Gram stain. The test may be difficult to interpret for rectal specimens and is not appropriate for pharyngeal cultures.

Urinary tract infection in a clinic for sexually transmitted diseases

A study of the prevalence of urinary tract infection (UTI) in 430 women attending a clinic for sexually transmitted diseases and its relationship to sexual activity is presented. UTI, usually asymptomatic, was found to be slightly more common in women attending the clinic than in the general population, its prevalence being 4.9%. UTI was more commonly found in patients who gave a history of recent sexual intercourse, which suggests that recent coitus was a factor in the development of significant bacteriuria. The likelihood of finding significant bacteriuria was not related to the number of sexual partners in the previous year. Trichomoniasis was more common in the small group of patients with UTI than in other women. The most common causative organism of UTI was Escherichia coli, and the isolates were usually sensitive to ampicillin, sulphonamides, trimethoprim, and nitrofurantoin.

Improved management in the diagnosis of gonorrhoea in women

In this paper an evaluation is made of the endeavours to improve diagnosis in women named as contacts of gonorrhoea. The problem was approached in three ways. (a) The number of sites sampled was increased. (b) The results of microscopical examination of smears made by clinical staff were regularly evaluated. (c) Cultural examinations by the supporting laboratory were dealt with more efficiently and speedily. It is concluded that the number of tests currently used to establish or exclude a diagnosis of gonorrhoea in women can safely be reduced to two, and that the methods currently in use allow a more cost-effective management of an increasing case load.

Which Neisseria?

A case of disseminated gonococcal infection in which the gonococcus was isolated from the blood and genitalia and the meningococcus from the throat is described. A second patient, in whom the meningococcus was isolated from the throat and the gonococcus from the genitals but in whom no organisms were recovered from the blood, had lesions resembling those of a disseminated infection. The results of 150 throat cultures from patients who were examined at a clinic because they had a history of oral sexual intercourse are presented. The meningococcus was isolated nearly six times more often in patients with genital gonorrhoea than in those in whom genital cultures were negative, while the gonococcus was found 2 1/2 times more often in those who carried the meningococcus in the throat than in those who did not. If these findings can be confirmed it could indicate an individual susceptibility to the acquisition of Neisserian organisms that would merit further investigation.

Interrelationship of Chlamydia trachomatis and other pathogens in the female genital tract

The isolation of Neisseria gonorrhoeae, Chlamydia trachomatis, Trichomonas vaginalis, and Candida albicans in the female genital tract was studied in 1323 patients attending a venereal disease clinic. Disruption of the cell monolayers use for the isolation of C. trachomatis was significantly associated with the presence of T. vaginalis; this effect was markedly reduced by the addition of vancomycin to gentamicin and amphotericin B in the transport and growth media. The only significant positive association was the more frequent isolation of C. trachomatis in the presence of N. gonorrhoeae. There was a negative association between N. gonorrhoeae and C. albicans and between T. vaginalis and C. albicans, the fungus being isolated significantly less frequently when these microorganisms were present.

Spectinomycin hydrochloride in the treatment of gonorrhoea: Its effect on associated Chlamydia trachomatis infections

Sixty-three heterosexual men were successfully treated with a single injection of spectinomycin hydrochloride 2 g for urethral infections with Neisseria gonorrhoeae. Chlamydia trachomatis was recovered from the urethra of 11 of these men both before and after treatment. In six men, the organism was isolated after but not before treatment. No isolates were obtained from the remaining men either before or after treatment. All 17 of the men who yielded C. trachomatis developed post-gonococcal urethritis. Eight of 46 men from whom no isolate was obtained in their cultures developed post-gonococcal urethritis. Seventeen of 50 women successfully treated with spectinomycin for cervical infections with N. gonorrhoeae yielded isolates of C. trachomatis both before and after treatment. The organism was isolated from five women before but not after treatment, and from four women after but not before treatment. In 24 women culture for C. trachomatis was negative both before and after treatment. Spectinomycin hydrochloride in the dosage used rarely eliminated C. trachomatis from the genital tract of either men or women; in this respect it resembled two other drugs commonly used for the treatment of gonorrhoea-pencillin and ampicillin.

Diagnosis of gonorrhoea in women

250 consecutive female contacts of men with gonorrhoea were examined in Lydia Department of Genito-urinary Medicine, St Thomas' Hospital, London, and 165 (66 per cent.) were found to be positive for gonorrhoea. Over 99 per cent. of the positive results were found by the first two sets of genital investigations. These results are compared with earlier and more recent results from our own and other centres and it is postulated that the higher early diagnosis rate is due to the introduction of a highly selective but non-inhibitory culture medium (VCNT), combined with a new incubator which accurately regulates temperature, humidity, and CO2 content. Reasons for the negative findings in 35 per cent. of the female gonorrhoea contacts are discussed.

Minimum inhibitory concentrations of penicillin and minocycline for 300 isolates of N. gonorrhoeae

The minimum inhibitory concentrations of penicillin and minocycline were measured on 300 consecutive isolates of N. gonorrhoeae from patients attending the Nottingham treatment centre. 210 (70 per cent.) of these were fully sensitive to penicillin (MIC less than 0-1 mug./ml) and 89 per cent. were fully sensitive to minocycline (MIC less than 0-5 mug./ml.). Of the nine strains resistant to penicillin (MIC less than or equal to 0-5 mug./ml.), eight were also of reduced sensitivity to minocycline.

Articular and cutaneous manifestations of gonorrhoea. Review of sixteen cases

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Diagnosis of gonorrhoea in women: comparison of sampling sites

A total of 250 women, 100 of them named contacts of men with gonorrhoea, were tested for infection. Each had prepared smear and culture specimens from urethra, endocervix, and vagina. The smears were Gram-stained and examined immediately. Cultures were taken using Stuart's transport medium with later inoculation of both selective and non-selective media for each specimen.It was shown that examination of specimens from urethra and endocervix gave results superior to those found on examination of vaginal material alone. The study revealed that nearly one infected woman in three would have been missed if vaginal material only had been examined. Failure to secure a prompt scientific diagnosis has serious epidemiological implications.Our results find support in the work of others. We conclude that the suggestion in some quarters that examination of vaginal material for the detection of gonococci is adequate should be abandoned. Any who feel unwilling to accept this view should at least supplement their testing with examination of urethral and endocervical specimens.

Selectagerm: a new approach to clinical bacteriology

A method of processing clinical specimens received at the laboratory on cotton wool swabs is described. The method uses a range of selective culture media to assist in the isolation of potential pathogens from mixed cultures. Because the culture media are distributed in 2 millilitre volumes in the small squares of divided plastic petri dishes it is economically possible to use the same series for every specimen. This facilitates the rapid processing of large numbers of swabs and allows the isolation of pathogens from sites where they might otherwise go unnoticed.