Aura 2016: first Australian report on antimicrobial use and resistance in human health

4.6 Neisseria gonorrhoeae

Health impact

N. gonorrhoeae causes gonorrhoea, an infection that is usually sexually transmitted. Most infections are asymptomatic, but common symptoms are urethritis in men and cervicitis in women. In some women, the infection ascends to the uterus and fallopian tubes, which can result in infertility if not treated promptly. Women who become infected in late pregnancy can spread the infection to the newborn during birth.

Treatment

Treatment of most gonorrhoea is empirical, and does not depend on the results of culture and susceptibility testing. This is because immediate empirical treatment is the most effective tool in preventing further transmission. Treatment is based on standard treatment protocols, which are guided by the prevalence of resistances determined in national surveillance programs.

Treatment of most gonorrhoea is empirical, and does not depend on the results of culture and susceptibility testing. This is because immediate empirical treatment is the most effective tool in preventing further transmission.

The most important agent for treating gonorrhoea is ceftriaxone, a third-generation cephalosporin. This is effective as a single dose in uncomplicated infections such as urethritis or cervicitis. Ceftriaxone has superseded penicillin and ciprofloxacin for first-line treatment because resistance to these latter agents has emerged. Azithromycin, an antimicrobial used for many years for the treatment of sexually transmitted infections caused by Chlamydia trachomatis and included in standard gonorrhoeae treatment regimens, is now considered as having additional value because it can treat strains with reduced susceptibility and resistance to ceftriaxone.

Types and impact of resistance

Resistance to ceftriaxone is an emerging concern globally. Failures of ceftriaxone treatment have been documented in Australia in strains that have decreased susceptibility to it (MICs above those of the wild-type; wild-type strains have no acquired resistance mechanisms).

Key findings (national)

In 2014, 15 703 cases of gonococcal infection were notified nationally (66.8 per 100 000 population). Of these cases, 4804 had positive laboratory cultures that were submitted for susceptibility testing. Most other cases would have been diagnosed without culture, using nucleic acid testing. Overall rates of resistance or decreased susceptibility to the main agents used for treatment are shown in Figure 4.19. In this and subsequent data, all ceftriaxone percentages are presented as decreased susceptibility, rather than full resistance.

Figure 4.19 Neisseria gonorrhoeae resistance to individual antimicrobials used for treatment, 2014

Note: Decreased susceptibility to ceftriaxone = minimum inhibitory concentrations above those of the wild type; wild-type strains have no acquired resistance mechanisms.

Source: National Neisseria Network (national)

Data table: Figure 4.19

Agent	% resistant
Benzylpenicillin	28.5
Ciprofloxacin	36.4
Azithromycin	2.5
Ceftriaxone	5.4 (decreased susceptibility)

Jurisdictional rates

There was some variation in resistance to first-line agents across states and territories (Figure 4.20). Most noticeable are the low rates of resistance in the remote areas of the Northern Territory and Western Australia, where a high proportion of the population is Indigenous. Rates of decreased susceptibility to ceftriaxone exceed 5% in New South Wales and Victoria.

Figure 4.20 Neisseria gonorrhoeae resistance to individual antimicrobials used for treatment, by jurisdiction, 2014

ACT = Australian Capital Territory; NSW = New South Wales; NT = Northern Territory; Qld = Queensland; SA = South Australia; Tas = Tasmania; Vic = Victoria; WA = Western Australia

Note: Decreased susceptibility to ceftriaxone = minimum inhibitory concentrations above those of the wild type; wild-type strains have no acquired resistance mechanisms.

Source: National Neisseria Network (national)

Data table: Figure 4.20

Jurisdiction	Benzylpenicillin (% resistant)	Ciprofloxacin (% resistant)	Ceftriaxone (% decreased susceptibility)	Azithromycin (% resistant)
ACT (n = 75)	12.0	44.0	2.7	9.3
NSW (n = 1672)	43.4	43.4	7.1	2.0
NT urban and rural (n = 99)	21.2	27.3	3.0	0.0
NT remote (n = 130)	1.5	3.1	0.8	0.0
Qld (n = 650)	23.5	28.3	3.2	3.5
SA (n = 207)	10.6	41.5	1.0	0.5
Tas (n = 30)	23.3	26.7	0.0	3.3
Vic (n = 1440)	22.4	38.8	6.6	2.3
WA urban and rural (n = 393)	26.5	29.8	3.6	5.3
WA remote (n = 108)	4.6	5.6	0.9	0.0

National trends

Over the past 15 years, resistance rates to the four main antimicrobials have evolved in different ways. Resistance to benzylpenicillin and ciprofloxacin trended upwards from 2003 to 2008, then declined somewhat, to stabilise at about 30%; this rate is not low enough to consider the reintroduction of these agents into standard treatment protocols. Rates of reduced susceptibility to ceftriaxone and resistance to azithromycin are low, but slowly trending upwards (Figure 4.21).

Figure 4.21 Trends in resistance and multidrug-resistance patterns, and decreased susceptibility to ceftriaxone, in Neisseria gonorrhoeae, 2000–14

Notes: Decreased susceptibility to ceftriaxone = minimum inhibitory concentrations above those of the wild type; wild-type strains have no acquired resistance mechanisms.

Source: National Neisseria Network (public and private hospitals, and health services)

Detailed reports of susceptibility data on N. gonorrhoeae from 1995 to 2013 can be found in the Australian Gonococcal Surveillance Programme annual reports (see Appendix 3).