Effectiveness of aztreonam for the treatment of gonorrhea

Management of Neisseria gonorrhoeae in the United States: Summary of Evidence From the Development of the 2020 Gonorrhea Treatment Recommendations and the 2021 Centers for Disease Control and Prevention Sexually Transmitted Infection Treatment Guidelines

INTRODUCTION

Neisseria gonorrhoeae has developed resistance to all first-line recommended therapies, making gonococcal antimicrobial resistance a major public health concern given limited antibiotic options currently and an even smaller antimicrobial development pipeline. Since the release of the Centers for Disease Control and Prevention (CDC) 2015 STD Treatment Guidelines, azithromycin, part of the 2015 dual-drug treatment regimen, has had a rapid rise in resistance. The 2020 CDC Gonorrhea Treatment Recommendations and the 2021 Sexually Transmitted Infections (STI) Treatment Guidelines were developed weighing the priorities of treating the individual, protecting the population, and preventing antimicrobial resistance.

METHODS

Gonorrhea subject matter experts (SME) generated 8 key questions and conducted a literature review of updated data from 2013 to 2019 on gonorrhea antimicrobial resistance, treatment failures, clinical trials, and other key topics. More than 2200 abstracts were assessed, and 248 clinically relevant articles were thoroughly reviewed. SMEs also evaluated N gonorrhoeae antimicrobial resistance data from the Gonococcal Isolate Surveillance Project (GISP).

EVIDENCE

Although there have been reports of ceftriaxone treatment failures internationally, GISP data suggest that ceftriaxone minimal inhibitory concentrations (MICs) have remained stable in the United States, with < 0.1% exhibiting an "alert value" MIC (> 0.25 mcg/mL). However, GISP documented a rapid rise in the proportion of isolates with an elevated MIC (≥ 2.0 mcg/mL) to azithromycin-nearly 5% in 2018. At the same time, new pharmacokinetic/pharmacodynamic data are available, and there is greater recognition of the need for antimicrobial stewardship.

SUMMARY

The 2021 CDC STI Treatment Guidelines now recommend 500mg ceftriaxone intramuscularly once for the treatment of uncomplicated gonorrhea at all anatomic sites. If coinfection with chlamydia has not been excluded, cotreatment with doxycycline 100mg twice daily for 7 days should be added. Few alternative therapies exist for persons with cephalosporin allergies; there are no recommended alternative therapies for N gonorrhoeae infection of the throat.

Treatment efficacy for rectal Neisseria gonorrhoeae: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Rectal gonorrhoea is a common sexually transmitted infection with increasing antimicrobial resistance requiring optimization of available treatments.

OBJECTIVES

This systematic review aimed to assess the efficacy of current treatments, previously trialled treatments and new emerging treatments for rectal Neisseria gonorrhoeae (NG).

METHODS

Online bibliographic databases were search from 1 January 1946 to 14 August 2020. All randomized controlled trials (RCTs) with rectal NG data among participants aged 15 years or above and published in English were included. Random effects meta-analyses were used to estimate overall treatment efficacy, defined as microbiological cure. Sub-group analyses included stratifying by diagnostic assay, by dual versus monotherapy, and by currently recommended treatments (e.g. ceftriaxone ± azithromycin) versus previously trialled but not recommended treatments (e.g. amoxicillin) versus emerging treatments (e.g. zoliflodacin). The study protocol was registered on PROSPERO (CRD42020202998).

RESULTS

54 studies including 1813 participants and 44 treatment regimens were identified. The overall summary treatment efficacy for rectal NG was 100.0% (95% CI: 99.9%-100.0%; I2 = 0.0%; P = 0.86). Efficacy estimates for monotherapies (100.0%; 95% CI: 99.88%-100.0%; I2 = 0.00%; P = 0.97) and dual therapies (100.0%; 95% CI: 97.65%-100.0%; I2 = 56.24%; P = 0.03) were similar. Efficacy was highest for current treatments (100.00%; 95% CI: 99.96%-100.00%; I2 = 0.00%; P = 0.98) versus emerging treatments (97.16%; 95% CI: 86.79%-100.00%; I2 = 0.00%; P = 0.84). There were no trials exclusively investigating rectal NG and small sample size was a limitation in most trials.

CONCLUSIONS

Currently recommended treatments containing ceftriaxone, as mono or dual therapy, are effective. Emerging drugs such as zoliflodacin may be potentially useful for rectal NG but further data are needed.

Aztreonam for Neisseria gonorrhoeae: a systematic review and meta-analysis

BACKGROUND

Ceftriaxone is the only consistently active antimicrobial agent recommended for the treatment of Neisseria gonorrhoeae. Although some new antimicrobials are in development, the necessity to expand treatment options in the near term may require using older drugs that have not been widely used to treat gonorrhoea.

METHODS

We conducted a literature review of clinical trials and case series, published from 1983 to 2017, reporting treatment efficacy results following administration of 1 g aztreonam intramuscularly or IV for uncomplicated gonococcal infections. We summed trial data, stratified by anatomical site of infection, and calculated summary efficacy estimates and 95% CI for each site of infection.

RESULTS

The 10 identified clinical trials enrolled 678, 38 and 16 individuals with urogenital, rectal and pharyngeal gonorrhoea, respectively. Aztreonam had an efficacy of 98.6% (95% CI: 97.5%-99.4%) for urogenital, 94.7% (95% CI: 82.3%-99.4%) for rectal and 81.3% (95% CI: 54.4%-96.0%) for pharyngeal gonococcal infections.

CONCLUSIONS

Although most clinical trials included in this meta-analysis were conducted >30 years ago, aztreonam appears to have excellent efficacy for urogenital gonorrhoea; its efficacy at extragenital sites remains uncertain.

Treatment of uncomplicated gonorrhoea with single dose aztreonam

Infection with Neisseria gonorrhoeae was cleared in 61 men and 26 women at all sites (except in the pharynx of one male bisexual patient with urethral and pharyngeal gonorrhoea) after treatment with aztreonam as a single 1 g intramuscular injection. Aztreonam was well tolerated with no adverse effects. This monobactam antibiotic was effective against both penicillin sensitive and resistant strains.

Aztreonam

Aztreonam is a new, totally synthetic beta-lactamase agent--the first monobactam. It is highly resistant to hydrolytic inactivation caused by plasmid-mediated (except PSE-2 enzyme found in some Pseudomonas species) or chromosomally mediated beta-lactamases (except for K1 produced by rare strains of Klebsiella oxytoca). Accordingly, aztreonam remains active against many pathogens that are resistant to other beta-lactam antibiotics. The drug exhibits directed antibacterial activity against gram-negative organisms and is effective as monotherapy against most Enterobacteriaceae and Hemophilus and Neisseria species, including beta-lactamase-producing strains; it is not active against anaerobes or gram-positive organisms. Before culture results are known, it may be necessary to administer the agent empirically in combination with other antibiotics. Aztreonam is rapidly distributed to most body tissues and fluids when administered parenterally. Its serum half-life is 1.7 hours, suggesting a dosing interval of 6-8 hours for severe or life-threatening infections and 8-12 hours for moderately severe infections and urinary tract infections. It is primarily eliminated unchanged in the urine and in much lesser amounts as a microbiologically inactive metabolite; slight biliary excretion may occur. Aztreonam is well-tolerated, lacking any serious adverse hematologic, otic, or renal system effects. Its lack of effect on anaerobes helps to maintain resistance against colonization. Particularly in light of its safety and unique properties, aztreonam promises to be a useful alternative to aminoglycoside therapy.

Aztreonam. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Aztreonam (azthreonam; SQ 26,776) is the first member of a new class of beta-lactam antibiotics, the monobactams. Aztreonam is selectively active against Gram-negative aerobic bacteria and inactive against Gram-positive bacteria. Thus, in vitro, aztreonam is inhibitory at low concentrations (MIC90 less than or equal to 1.6 mg/L) against Enterobacteriaceae except Enterobacter species, and is active against Pseudomonas aeruginosa, 90% of pseudomonads being inhibited by 12 to 32 mg/L. Aztreonam is inactive against Gram-positive aerobic bacteria and anaerobes, including Bacteroides fragilis. Therefore, when administered alone, aztreonam has minimal effect on indigenous faecal anaerobes. Aztreonam must be administered intravenously or intramuscularly when used to treat systemic infections, since absolute bioavailability is very low (about 1%) after oral administration. Since elimination half-life is less than 2 hours, 6- or 8-hourly administration is used in the treatment of moderately severe or severe infections, although 12-hourly injection is adequate in less severe systemic and some urinary tract infections. Therapeutic trials have shown aztreonam to be effective in Gram-negative infections including complicated infections of the urinary tract, in lower respiratory tract infections and in gynaecological and obstetric, intra-abdominal, joint and bone, skin and soft tissue infections, uncomplicated gonorrhoea and septicaemia. In comparisons with other antibiotics, aztreonam has been at least as effective or more effective than cefamandole in urinary tract infections and similar in efficacy to tobramycin or gentamicin. Where necessary, aztreonam and the standard drug have both been combined with another antibiotic active against Gram-positive and/or anaerobic bacteria. Aztreonam has been effective in eradicating pseudomonal infections in most patients (except in patients with cystic fibrosis), but the inevitably limited number of pseudomonal infections available for study prevents any conclusions as to the relative efficacy of aztreonam compared with other appropriate regimens against these infections. Thus, with an antibacterial spectrum which differs from that of other antibiotics, aztreonam should be a useful alternative to aminoglycosides or 'third generation' cephalosporins in patients with proven or suspected serious Gram-negative infections.

The use of aztreonam in the treatment of uncomplicated gonorrhoea

A total of 57 men and 26 women with uncomplicated gonorrhoea was treated with 1 g aztreonam intramuscularly. The cure rate was 96% and included successful treatment of 4 infections due to beta-lactamase producing organisms and 8 patients with pharyngeal involvement. The minimum inhibitory concentrations of aztreonam in vitro were lower than those of penicillin and similar to cefuroxime, and side-effects were minimal. It is concluded that aztreonam is effective against Neisseria gonorrhoeae in vivo and in vitro.