Effects of penicillin, streptomycin, and tetracycline on N. gonorrhoeae isolated in 1944 and in 1957

Where have all the susceptible gonococci gone? A historical review of changes in MIC distribution over the past 75 years

BACKGROUND

Does the emergence of antimicrobial resistance in Neisseria gonorrhoeae include the erasure of highly susceptible strains or does it merely involve a stretching of the MIC distribution? If it was the former this would be important to know as it would increase the probability that the loss of susceptibility is irreversible.

METHODS

We conducted a historical analysis based on a literature review of changes of N. gonorrhoeae MIC distribution over the past 75 years for 3 antimicrobials (benzylpenicillin, ceftriaxone and azithromycin) in five countries (Denmark, Japan, South Africa, the United Kingdom and the United States).

RESULTS

Changes in MIC distribution were most marked for benzylpenicillin and showed evidence of a right shifting of MIC distribution that was associated with a reduction/elimination of susceptible strains in all countries. In the case of ceftriaxone and azithromycin, where only more recent data was available, right shifting was also found in all countries but the extent of right shifting varied and the evidence for the elimination of susceptible strains was more mixed.

CONCLUSIONS

The finding of right shifting of MIC distribution combined with reduction/elimination of susceptible strains is of concern since it suggests that this shifting may not be reversible. Since excess antimicrobial consumption is likely to be responsible for this right shifting, this insight provides additional impetus to promote antimicrobial stewardship.

Epidemiological Trends of Antibiotic Resistant Gonorrhoea in the United Kingdom

Gonorrhoea is one of the most common sexually-transmitted bacterial infections, globally and in the United Kingdom. The levels of antibiotic resistance in gonorrhoea reported in recent years represent a critical public health issue. From penicillins to cefixime, the gonococcus has become resistant to all antibiotics that have been previously used against it, in each case only a matter of years after introduction as a first-line therapy. After each instance of resistance emergence, the treatment recommendations have required revision, to the point that only a few antibiotics can reliably be prescribed to treat infected individuals. Most countries, including the UK, now recommend that gonorrhoea be treated with a dual therapy combining ceftriaxone and azithromycin. While this treatment is still currently effective for the vast majority of cases, there are concerning signs that this will not always remain the case, and there is no readily apparent alternative. Here, we review the use of antibiotics and epidemiological trends of antibiotic resistance in gonorrhoea from surveillance data over the past 15 years in the UK and describe how surveillance could be improved.

Antimicrobial Resistance Expressed by Neisseria gonorrhoeae: A Major Global Public Health Problem in the 21st Century

Neisseria gonorrhoeae is a strictly human pathogen that is typically transmitted by sexual contact. The associated disease gonorrhea has plagued humankind for thousands of years, with a current estimated incidence of 78 million cases per year. Advances in antimicrobial discovery in the 1920s and 1930s leading to the discovery of sulfonamides and penicillin begun the era of effective antimicrobial treatment of gonorrhea. Unfortunately, the gonococcus developed decreased susceptibility or even resistance to these initially employed antibiotics, a trend that continued over subsequent decades with each new antibiotic that was brought into clinical practice. As this pattern of resistance has continued into the 21st century, there is now reason for great concern, especially in an era when few new antibiotics have prospects for use as treatment of gonorrhea. Here, we review the history of gonorrhea treatment regimens and gonococcal resistance to antibiotics, the mechanisms of resistance, resistance monitoring schemes that exist in different international settings, global responses to the challenge of resistance, and prospects for future treatment regimens in the 21st century.

Antimicrobial resistance in Neisseria gonorrhoeae in the 21st century: past, evolution, and future

Neisseria gonorrhoeae is evolving into a superbug with resistance to previously and currently recommended antimicrobials for treatment of gonorrhea, which is a major public health concern globally. Given the global nature of gonorrhea, the high rate of usage of antimicrobials, suboptimal control and monitoring of antimicrobial resistance (AMR) and treatment failures, slow update of treatment guidelines in most geographical settings, and the extraordinary capacity of the gonococci to develop and retain AMR, it is likely that the global problem of gonococcal AMR will worsen in the foreseeable future and that the severe complications of gonorrhea will emerge as a silent epidemic. By understanding the evolution, emergence, and spread of AMR in N. gonorrhoeae, including its molecular and phenotypic mechanisms, resistance to antimicrobials used clinically can be anticipated, future methods for genetic testing for AMR might permit region-specific and tailor-made antimicrobial therapy, and the design of novel antimicrobials to circumvent the resistance problems can be undertaken more rationally. This review focuses on the history and evolution of gonorrhea treatment regimens and emerging resistance to them, on genetic and phenotypic determinants of gonococcal resistance to previously and currently recommended antimicrobials, including biological costs or benefits; and on crucial actions and future advances necessary to detect and treat resistant gonococcal strains and, ultimately, retain gonorrhea as a treatable infection.

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.

Cephalosporins of the third generation for the treatment of gonorrhea

The article presents the data on antibiotic resistance and N. gonorrhoeae mechanisms for developing resistance to antimicrobial drugs belonging to different pharmacologic groups and applied for causal treatment of gonorrhea. The article proves the key problem related to the treatment of gonococcal infection in Russia lies in the prevalence of strains being resistant to most of the antibacterial drugs that used to be applied in the clinical practice on a broad scale and efficiently. So, cephalosporins of the third generation are presently the only drug type that N. gonorrhoeae remains sensitive to. Their application ensures the maximum efficacy against the gonococcal infection. According to the presentday international recommendations complying with the WHO criteria as well as accumulated experience, cefixime, a drug belonging to cephalosporins of the third generation, can be a drug of choice for the antibacterial therapy of gonorrhea along with ceftriaxon.

The virgin population of Neisseria gonorrhoeae in Stockholm has decreased and antimicrobial resistance is increasing

AIMS

To investigate the evolution of chromosomal and plasmid mediated resistance for ampicillin and tetracycline of N gonorrhoeae strains in Stockholm during 1982-1993.

METHODS

A total of 404 gonococcal strains isolated in 1982, 1987, 1990, 1992, 1993 were analysed for minimal inhibitory concentrations (MIC) of ampicillin and tetracycline and for plasmid content. MIC values were determined by the agar dilution method and plasmid preparations were performed using alkaline lysis. To detect additional gonococcal strains with tet(M) plasmids all strains isolated in 1988-1989 and 1991, in all 234 isolates, were analysed retrospectively for MIC values of tetracycline. If an MIC value of > or = 4.0 mg/l was recorded plasmid analysis was performed.

RESULTS

Increased proportions of chromosomally mediated resistance to tetracycline (p < 0.001) as well as plasmid mediated resistance to both ampicillin (p < 0.02) and tetracycline were found in the later part of the study. In 1991 the first gonococcus with tet(M) plasmid was isolated in Sweden. The proportion of strains with chromosomally mediated resistance for ampicillin did not change during the study period. The proportion of gonococcal strains with the 39 kb conjugative plasmid was increased in the later part of the study.

CONCLUSIONS

The increased proportion of N gonorrhoeae strains with resistance to ampicillin and tetracycline is most likely due to importation of strains from areas with high prevalence of antibiotic resistant gonococci. The proportion of N gonorrhoeae strains with tet(M) plasmids is low in Sweden, but might increase in the same way as the proportion of PPNG strains has increased during 1982-1993.

Epidemiology of penicillin resistant Neisseria gonorrhoeae

OBJECTIVE

To study the epidemiology of Neisseria gonorrhoeae that exhibit both chromosomal and plasmid-mediated resistance to penicillin.

MATERIALS AND METHODS

A total of 1589 strains of N gonorrhoeae isolated from patients attending St Mary's Hospital, London were tested for both their susceptibility to penicillin and for their auxotype and serotype.

RESULTS

Of the 940 non-penicillinase producing N gonorrhoeae, 840 were considered penicillin sensitive (MIC less than or equal to 0.5 mg/l) and 100 were chromosomally-mediated resistant N gonorrhoeae (CMRNG), (MIC greater than or equal to 1.0 mg/l). Of the 649 penicillinase producing N gonorrhoeae (PPNG), 429 carried the 4.4 megadalton (MDa) penicillinase encoding plasmid and 220 carried the 3.2 MDa plasmid. CMRNG were predominantly serogroup IB (90%). PPNG with 3.2 MDa plasmid were the only group more often serogroup IA (58%) than IB (42%). Serovar IA-1/2 and requirement for arginine, hypoxanthine and uracil (AHU) were associated with increased susceptibility to penicillin whereas serovar IB-5/7 was associated with decreased susceptibility in nonPPNG. There was a significant difference in the distribution of the IA and IB serovars between PPNG carrying either the 4.4 MDa or 3.2 MDa plasmid. AHU and PAOU requiring strains were not found among PPNG and were uncommon among CMRNG.

CONCLUSION

Some clear associations have been found but the pattern among PPNG appears more complex and in most instances could be related to clusters of a single strain over a short time span.

Standardization of disk diffusion and agar dilution susceptibility tests for Neisseria gonorrhoeae: interpretive criteria and quality control guidelines for ceftriaxone, penicillin, spectinomycin, and tetracycline

A six-laboratory study developed a standardized method for determining the susceptibilities of Neisseria gonorrhoeae strains to penicillin, tetracycline, spectinomycin, and ceftriaxone. Three quality control organisms were also selected, and quality assurance guidelines were initially generated for the disk diffusion and agar dilution methods. The medium recommended for gonococcal susceptibility testing was GC agar with a defined "XV-like" supplement. The supplement should be free of cysteine, a component implicated in the inactivation of some newer beta-lactam compounds. Penicillin, tetracycline, spectinomycin, and ceftriaxone were stable in agar plates stored at 3 to 5 degrees C for at least 2 weeks. Numerous GC agar and drug disk lots were used during the trials without significant variation in test results. Several other gonococcal strains were recommended for additional medium quality assurance. The disk quality control zone limits were established for N. gonorrhoeae ATCC 49226 (formerly CDC F-18) and Staphylococcus aureus ATCC 25923. MIC quality control ranges were also developed for N. gonorrhoeae ATCC 49226 and S. aureus ATCC 29213. The interpretive criteria for penicillin were as follows: susceptibility, greater than or equal to 47 mm (diameter of inhibition zone) (less than or equal to 0.06 micrograms/ml [MIC]); resistance, less than or equal to 26 mm (greater than or equal to 2 micrograms/ml). For tetracycline they were as follows: susceptibility, greater than or equal to 38 mm (less than or equal to 0.25 microgram/ml); resistance, less than or equal to 30 mm (greater than or equal to 2 micrograms/ml). For spectinomycin they were as follows: susceptibility, >/= 18 mm (</= 32 micrograms/ml); resistance, </= 14 mm (>/= 128 micrograms/ml). For ceftriaxone susceptibility, the criterion was >/= 35 mm (</= 0.25 micrograms/ml) with no other category. Criteria of </= 19 mm for plasmid-mediated resistances to penicillin and tetracycline were also confirmed. The false-susceptibility errors were </= 1% with these criteria.

Associations between serotype and susceptibility to antibiotics of Neisseria gonorrhoeae

A serological classification scheme for Neisseria gonorrhoeae was used to investigate the epidemiological associations between gonococcal serotype and other bacterial and host characters. Six hundred and fifty clinical isolates of non-penicillinase producing N gonorrhoeae from the Praed Street Clinic, St Mary's Hospital, were included in this study. The strains collected represented 41 serovars, although 485 (75%) of the 650 strains belonged to five serovars. Strains of serovar IA-1/2 were commonly isolated from the cervix and tended to be sensitive to penicillin and moderately resistant to erythromycin. Strains of serovar IB-1 showed bimodal patterns of susceptibility to both penicillin and erythromycin and were obtained equally from all anatomical sites. Strains of serovar IB-2 were isolated more often from the rectum and were associated with homosexually acquired infections, whereas those of serovar IB-3 were sensitive to erythromycin and were rarely isolated from the rectum. Strains of IB-5/7 were more resistant to penicillin and erythromycin than strains of other serovars. The serological classification of N gonorrhoeae is thus a powerful tool that may be used to study biological characteristics of the gonococcus, such as susceptibility to antimicrobials and site tropism.

Susceptibility testing of Neisseria gonorrhoeae to penicillin and spectinomycin in a diagnostic laboratory

Agar dilution breakpoint susceptibility testing using GC, DST, and proteose agars, was performed on consecutive clinical isolates of non-penicillinase producing Neisseria gonorrhoeae to examine the feasibility of using such a system in a diagnostic laboratory. The incidence and level of resistance to penicillin and spectinomycin was also assessed. On DST medium 93 of 200 (46.5%) of isolates were of intermediate resistance to penicillin (MIC 0.12-0.5 mg/l) and 21 of 200 (10.5%) were resistant to penicillin (MIC greater than or equal to 1.0 mg/l). Ninety two of 200 (46%) of isolates had an MIC to spectinomycin of 32 mg/l on DST agar. Isolates seemed to be more resistant when tested on the two other media. The methods used in this study could be applied in a routine diagnostic laboratory for immediate clinical benefit and long term epidemiological studies. To enable direct comparisons to be made between populations at different centres, however, methods for gonococcal susceptibility testing need to be standardised.

Neisseria gonorrhoeae: a versatile pathogen

Neisseria gonorrhoeae is one of the most important causes of sexually transmitted disease. We do not fully understand the pathogenesis of infection with this organism, although recent improvements in immunological and molecular techniques have brought us closer to an answer. These techniques are now also being used to detect and identify N gonorrhoeae and to analyse the epidemiology of gonorrhoea. Plasmid and chromosomal mediated antibiotic resistance increases the difficulty of controlling gonorrhoea. Resistant strains occur all over the world and new patterns of resistance are still emerging. A better understanding of gonococcal pathogenicity is necessary for the development of an effective vaccine. Despite work on pili and outer membrane proteins no vaccine yet exists. The control of gonorrhoea still depends on diagnosis, treatment, and epidemiological control, facilities that are not widely available in many of those parts of the world where gonorrhoea is a major problem.

Role of cephalosporins in gonorrhoea and other sexually transmitted diseases

Cephalosporins have a role in the treatment of gonorrhoea, and especially infections caused by strains that are penicillin-resistant, either because they produce plasmid-mediated beta-lactamase or they have chromosomally mediated diminished permeability or modified penicillin-binding proteins. Although none of the oral or Group I agents are useful, most of the Group II, III and IV agents are, and especially cefuroxime, cefotaxime, ceftriaxone and cefoxitin. In addition to uncomplicated urethral, cervical or rectal infections, appropriate regimens are also effective for the treatment of pharyngeal infections, disseminated infections and gonococcal ophthalmia. The cephalosporins have no clear role in the treatment of syphilis, granuloma inguinale, Mycoplasma or chlamydial infections or bacterial vaginosis, but ceftriaxone may be effective in chancroid, and cefoxitin in combination with an antichlamydial agent (such as a tetracycline) might be used for the treatment of pelvic inflammatory disease.

Recognition and clinical significance of mechanisms of bacterial resistance to beta-lactams

Resistance to beta-lactams may be difficult to recognize. This is due to the difficulty in detecting these resistances, when the routine tests performed in diagnostic laboratories are interpreted in the usual manner. Since failure to recognize this type of resistance may have serious consequences for the patient, it is essential that it be detected when present. For the detection of methicillin resistance of Staphylococcus aureus a standardized method using either a medium containing 5% NaCl or a low incubation temperature is advocated. Methicillin resistance of S. epidermidis can only be recognized reliably by means of a quantitative test and incubation for 42-48 h. Resistance of Haemophilus influenzae to ampicillin may be intrinsic or it may be caused by a TEM beta-lactamase; a beta-lactamase test should be used to detect the latter type of resistance. Inducible cephalosporinase may be responsible for the rapid development of resistance of some bacterial species to cefamandole, even during therapy. If a stable beta-lactamase production is attained by mutation, resistance to other beta-lactams will usually be present as well. Routine induction tests should be performed for all isolates of species of Enterobacter, Serratia, Citrobacter and Proteus, indole-positive. The same type of 'hidden' resistance may be present in Pseudomonas aeruginosa, with regard to cefotaxime and other third-generation cephalosporins. Beta-lactamase-positive Neisseria gonorrhoeae can easily be recognized by a beta-lactamase test. In addition, the results of diffusion tests allow one to distinguish between beta-lactamase-positive and beta-lactamase-negative strains. Recognition of those strains of N. gonorrhoeae having a decreased susceptibility to penicillin is only possible when well-standardized quantitative tests are used.

Antimicrobial sensitivity of Neisseria gonorrhoeae. Comparison of penicillinase producing and non-penicillinase producing strains

The sensitivity of 42 strains of penicillinase producing Neisseria gonorrhoeae (PPNG) and 46 strains of non-PPNG was tested against benzyl penicillin, spectinomycin, erythromycin, cefuroxime, ceftriaxone, tetracycline, sulphamethoxazole, and trimethoprim. The minimum inhibitory concentrations (MICs) of all antimicrobials, except trimethoprim and ceftriaxone, differed significantly for PPNG and non-PPNG strains. Ceftriaxone was the most active compound tested, the MIC for all strains being less than or equal to 0.015 mg/1. PPNG were less sensitive than non-PPNG strains to spectinomycin. It remains to be seen whether the increase in prevalence of PPNG strains is followed by a gradual increase in low level resistance to spectinomycin as well as the occasional finding of high level resistance to this antibiotic.

In vitro susceptibility of 50 non-beta-lactamase-producing Neisseria gonorrhoeae strains to 12 antimicrobial agents

The in vitro activities of six commonly used antibiotics and six newer beta-lactam agents were determined in 50 consecutive clinical isolates of beta-lactamase-negative Neisseria gonorrhoeae. The gonococci isolated were notably resistant to penicillin, ampicillin, erythromycin, and tetracycline, whereas all of the strains were susceptible to the newer beta-lactam agents cefoxitin and spectinomycin.

Neisseria gonorrhoeae isolated from disseminated and localised infections in pre-penicillin era. Auxotypes and antibacterial drug resistances

Interest in the evolution of gonococcal auxotrophy led to a study of 72 strains isolated between 1935 and 1948 from the urogenital tract (57 patients), the eye (two patients), and from disseminated gonococcal infections (11 patients and probably two others). Two cervical isolates with nutritional requirements for proline, arginine, histidine, and biotin were oxidase-positive, Gram-negative diplococci, but their identity as Neisseria gonorrhoeae was uncertain because they were atypically susceptible to colistin and did not produce acid in glucose media. The N gonorrhoeae strains were highly susceptible to 11 other antibacterial drugs but not to sulphadiazine. Defects of one or more pathways for the biosynthesis of methionine, proline, arginine, threonine, lysine, the branched-chain amino acids, hypoxanthine, and thiamine pyrophosphate were found in 39 of the 70 strains, including four isolated in the presulphanilamide era. Unexpectedly, methionine was required for the growth of 11 (21%) of the 52 Danish strains and for 13 (72%) of 18 strains isolated in the USA. The Danish strains included 28 (54%) that did not require any of the compounds used for differentiating auxotypes, whereas this type was represented by only three (17%) of the USA strains. None of the gonococci required uracil or other pyrimidines. This suggests that the requirements for arginine, hypoxanthine, and uracil commonly found in recent isolates from disseminated gonococcal infections probably evolved treatment with sulphonamide was replaced by penicillin.

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.

Penicillinase-producing Neisseria gonorrhoeae in Riyadh, Saudi Arabia

Of 83 strains of Neisseria gonorrhoeae isolated in Riyadh, Saudi Arabia, between April 1979 and August 1980, 10 produced beta-lactamase and had minimum inhibitory concentrations (MICs) of penicillin between 1 and greater than or equal to 4 micrograms/ml. Of the 73 (88%) non-penicillinase-producing strains, 55% had diminished sensitivity to penicillin (MIC = 0.06 micrograms/ml) and 11 (15%) were highly resistant (MICs ranging from 0.5-2 micrograms/ml). This high incidence of resistance may be due to widespread abuse of antibiotics; it also confirms that two mechanisms of resistance to penicillin exist in this species.

Patient variables associated with penicillin resistance in Neisseria gonorrhoeae

In an ongoing cooperative study of uncomplicated genital gonorrhea within the United States, 6,735 pretreatment gonococcal isolates were tested for their in vitro resistance to penicillin. By using a regression analysis technique, we examined 99 patient-associated variables which might be associated with penicillin resistance of the isolates. Patients were most likely to have relatively resistant isolates if they were black, had used antimicrobial agents within 2 weeks of treatment for gonorrhea, or were men with symptomatic urethritis.

Studies on Neisseria gonorrhoeae cultured in liquid medium

Experiments were carried out to determine the minimum amount of inoculum of gonococci that is needed to produce growth in ANM liquid medium. This was found to be less than had previously been thought. Minimum inocula were used to study penicillin sensitivity in liquid medium. This work showed that growth occurred at higher concentrations of penicillin with larger inocula. Evidence was also obtained which suggested that in some circumstances penicillin acts bacteriostatically rather than bacteriocidally. It was also shown that growth of gonococci can be inhibited in liquid medium by the presence of hyperimmune serum, the inhibition being more marked in the presence of fresh complement. This work is continuing in the hope that it may provide a basis for a much-needed serological test for gonorrhoea. This would be especially valuable in chronic assymptomatic infections.

Sensitivity pattern of Neisseria gonorrhoeae to penicillin and screening for beta-lactamase production in Ibadan, Nigeria

The few reports from Africa on sensitivity determinations of Neisseria gonorrhoeae suggest that there is an increasing resistance in the strains, as has been found in other parts of the world. In the current study, the penicillin sensitivities and β-lactamase production of 80 consecutive strains of N. gonorrhoeae isolated from cases of acute urethritis in African men in Ibadan were studied. Of these strains, 17·5% had a penicillin minimum inhibitory concentration (MIC) of 0·038 μg/ml or less and were considered as being `fully sensitive'. However, 82·5% had an MIC of 0·075 μg penicillin/ml or more, and were considered as having `diminished sensitivity' to penicillin. It was thought that this high incidence of relatively insensitive strains was owing to the sequential selection of these strains because of the easy availability and abuse of antimicrobial agents by the general population. Furthermore, 13 strains (16·25%) demonstrated high level resistance with MIC values of over 0·6 μg penicillin per ml and it is probable that many of the strains will demonstrate multiresistance to the commonly misused antimicrobial agents. Consequently, treatment of patients harbouring these strains may present problems because of financial constraints of the health services in purchasing the appropriate antibiotics. Despite the high level resistance of the strains in an environment of intensive penicillin and ampicillin use, none of the strains studied showed any evidence of β-lactamase production. Nevertheless, continuous surveillance of β-lactamase production by the gonococcus is recommended in the larger medical centres in developing countries.

Auxotypes and penicillin susceptibilities of Neisseria gonorrhoeae isolated from patients with gonorrhea involving two or more sites

A system of auxotyping described in 1973 is based on the differing nutritional requirement patterns of Neisseria gonorrhoeae strains. Our ongoing evaluation of the reliability of auxotyping has involved a study of the constancy of characteristics of gonococci isolated at one time from two or more sites of a given subject. The auxotypes and minimal inhibitory concentration (MIC) of penicillin G were determined for 181 isolates obtained from 84 patients with uncomplicated gonorrhea, for 16 isolates from 8 couples with uncomplicated gonorrhea, and for 21 isolates from 12 other patients, 9 with disseminated gonococcal infection and three consorts. The penicillin MIC served to distinguish between many members of auxotypes 1, 2, and 3, which are commonly involved in uncomplicated gonorrhea. Thus, for proline-requiring gonococci (auxotype 2) the MIC ranged from 0.01 to 1.2 IU of penicillin per ml. The profile of gonococcal responses to seven other antibacterial drugs provided useful additional information where the extent of phenotypic similarity was in doubt. In all but seven instances, the gonococci isolated from different sites of the same patient, or from a consort, had the same nutritional requirements and penicillin MIC. The gonococci isolated from one patient with disseminated gonococcal infection and from one of her two sexual contacts had nutritional requirements for arginine, hypoxanthine, uracil, and thiamine pyrophosphate, whereas the strain isolated from her second contact differed in having no requirement for thiamine pyrophosphate. The paired cervical and rectal isolates from one patient with uncomplicated gonorrhea differed only with respect to a requirement for hypoxanthine. Pairs of isolates from three patients differed slightly in degree of susceptibility to penicillin. In the remaining two instances, however, numerous differences between the isolates from the endocervix and the anal canal of a given patient indicated the presence of concomitant infections with different strains of N. gonorrhoeae.

Effective treatment of gonorrhoea

Effective therapy of gonorrhoea has changed drastically over the years, reflecting the progessive acquisition of relative antibiotic resistance by the causative organism. Although in the US. th 1974 USPHS recommendations are the best guidelines for management at present, recent epidemiological trends may obviate some of these provisions. The most important of these trends is the emergence of R-factor carrying strains capable of producing penicillinase, thereby making these strains absolutely resistant to clinically achievable levels of penicillin. This review analyses this problem in the context of reasonable therapeutic goals and also discusses optimum management of patients with such complications as pharyngeal infection, pelvic inflammatory disease and disseminated gonococcal infection.

Activity of eight antimicrobial agents in vitro against N. Gonorrhoeae

The sensitivity of four groups of gonococcal strains to ampicillin (Am), penicillin (P), tetracycline (T), rifampicin (Ri), spectinomycin (Sp), sulphamethoxazole (Su), trimethoprim (Tr), and a combination of Su and Tr in the ratio 5:1 (Su/Tr 5:1) has been determined. The various groups of strains were isolated from male civilians (MC), female civilians (FC), and sailors (S) in Rotterdam (R) in 1972, and from FC in Amsterdam (A) in 1967. The S-R strains, which may be regarded as mainly imported, were compared with the MC-R and FC-R (which may be considered as mainly of Dutch origin). Also investigated was whether the incidence of relative resistance to the antibiotics investigated among Dutch strains has changed in the period from 1967 to 1972. For this purpose, the FC-A and FC-R strains were compared. The MC-R and FC-R strains were also compared with one another. Finally, Spearman's rank correlation coefficient r were calculated between the sensitivity distributions for each pair of antibiotics investigated, for all strains. The S-R strains were significantly less sensitive to Am, P, T, Ri, and Tr than the MC-R and FC-R strains. Comparison of the FC-A and FC-R strains revealed that the FC-R strains were significantly less sensitive only to Su/Tr 5:1. A possible explanation for this finding is given. With the exception of one FC-A strain, all gonococcal strains were sensitive to Sp. High values of r (larger than or equal to 0.50) were found between Am and P, Am and T, and P and T for all groups of strains. The values of r between any pair of the antibiotics Am, P, T, Ri, and Tr (with the exception of the pair Am-P) were always highest for the S-R strains. High values of r (larger than or equal to 0.50) were found between Su and Su/Tr 5:1 for all groups of strains. The FC-A strains, unlike the R strains, gave low values of r between Su and Tr and between Tr and Su/Tr 5:1. A possible explanation for this is given. Finally, a hypothesis is put forward to explain the fact that no significant changes were found in the sensitivity of Dutch gonococcal strains to Am, P, T, Ri, Sp, Su, and Tr in the period from 1967 to 1972, while the S strains (which may be regarded as imported) showed a significantly higher percentage of strains relatively resistant to Am, P, T, Ri, and Tr.

Gonococcal antibiotic resistance in Los Angeles

One hundred and thirty-five gonococcal isolates collected from Los Angeles in 1972 were studied for antibiotic susceptibility to penicillin, ampicillin, carbenicillin, tetracycline, minocycline, doxycycline and spectinomycin. Only 12 percent of the isolates were sensitive to 0.05 mug per ml of penicillin while 35 percent required at least 0.5 mug per ml for inhibition of growth. The results were slightly better with ampicillin and nearly the same with carbenicillin. Nineteen percent of the isolates required at least 1.0 mug per ml of tetracycline for inhibition of growth and the results were similar with either minocycline or doxycycline. Forty-nine percent were sensitive to 2.0 mug per ml spectinomycin, but 37 percent required at least 8.0 mug per ml for inhibition of growth. In this study nine of eleven isolates resistant to 1.0 mug per ml of tetracycline were also resistant to both penicillin and spectinomycin. Six came from endocervical sites of female patients who contributed only 37 percent of the total number of isolates studied. Correlation between the agar dilution and disc diffusion methods was satisfactory with penicillin but not with ether tetracycline or spectinomycin.

Antibiotic disk susceptibility tests with Neisseria gonorrhoeae

We have used a standardized disk diffusion procedure to test the susceptibility of 892 isolates of Neisseria gonorrhoeae to six antibiotics. The disk diffusion test described is a modification of the disk test of Bauer, Kirby, Sherris, and Turck, which is widely used for susceptibility testing of fast-growing, aerobic pathogens. With all six antibiotics (penicillin, ampicillin, tetracycline, erythromycin, chloramphenicol, and cephaloridine), disk test results were found to be reproducible and correlated well with the minimal inhibitory concentration as determined by an agar dilution procedure. The coefficients of correlation ranged from -0.79 with cephaloridine to -0.93 with penicillin. The technique described for disk susceptibility testing of gonococci can be used both for research and clinical purposes.

Antibiotic sensitivity of gonococcal strains isolated in the South-East Asia and Western Pacific regions in 1961-68

A decreasing susceptibility of gonococcal strains to penicillin and other antibiotics has been observed in most parts of the world, including the WHO South-East Asia and Western Pacific regions. In the Neisseria Department, Statens Seruminstitut, Copenhagen, the antibiotic sensitivity of about 100 gonococcal strains from these regions has been determined. The strains were collected during 2 periods, one in 1961 (Ceylon and the Philippines), the other in 1967-68 (Thailand, Taiwan, Viet-Nam and Hong Kong).It was found that the incidence of gonococcal strains with decreased susceptibility to penicillin and most of the more generally used antibiotics is increasing in these regions. The distribution of the 50% inhibitory concentrations of penicillin, tetracycline, streptomycin and spiramycin was similar for the strains isolated in the Philippines in 1961 and for those from the other areas in 1967-68, namely, strains with "normal sensitivity" were lacking. Most of the strains collected in 1961 were fully sensitive to chloramphenicol and erythromycin, whereas about 25% of the strains collected in 1967-68 were only moderately sensitive to chloramphenicol, and about 75% were moderately sensitive to erythromycin; 1 strain was resistant to erythromycin. Only 10% of these strains were sensitive to all the antibiotics employed.In contrast to these findings, several authors report an increasing susceptibility of the gonococcal strains in northern Europe. Possible explanations for the reversion to "normal sensitivity" are discussed briefly.