Acknowledgements

Monitoring of Anti-Microbial Resistance of STI Pathogens

Why monitor

for resistance?
Drugs are routinely used to treat STI infections. This has led to increasing rates of resistance. Resistance is the alteration of a pathogen that makes it non-responsive to a particular anti-microbial agent. Simply put, the drug being used no longer controls or eliminates the infection.
Resistance monitoring entails examining in the laboratory the effectiveness of various anti-microbial agents in inhibiting the growth of N. gonorrhoeae. In resistance monitoring, various concentrations of a given anti-microbial agent are used to determine the minimum concentration of that agent required to stop the organism from growing. Depending on the concentration of the anti-microbial agent required to inhibit growth, the organism can be classified as sensitive, intermediate or resistant to a particular anti-microbial agent. Usually the organism is checked for sensitivity against several different anti-microbials, often from different classes.
As an example of how to monitor anti-microbial resistance, we will discuss N. gonorrhoeae, a core component of STI surveillance. Resistance monitoring is done to:

• 
  obtain the data necessary for developing and revising treatment guidelines
  
• 
  detect newly emerging resistance.
  

It is also important to monitor N. gonorrhoeae to ensure that the medication given to a patient with a gonococcal infection will cure the infection. Effective treatment for gonorrhoea:

• 
  relieves the signs and symptoms and achieves microbiologic cure in individual patients
  
• 
  prevents complications of pelvic inflammatory disease, chronic pelvic pain and infertility in women
  
• 
  reduces the risk of HIV transmission by decreasing the presence of white blood cells at the cervix and urethra
  
• 
  interrupts transmission of N. gonorrhoea.
  

Laboratory

requirements
Surveillance surveys for anti-microbial resistance of STI pathogens are usually organised and conducted by the national HIV/STI control programme. Sites are chosen that have healthcare facilities with well-
Laboratory requirements, continued
trained staff and laboratory expertise. Only selected sites will have the capacity to conduct these types of surveillance activities.
In our example of monitoring N. gonorrhoeae and selecting anti-microbial drugs for susceptibility testing, give priority to drugs commonly used for treating gonococcal infections. A laboratory performing susceptibility testing for N. gonorrhoeae should be able to accomplish the following tasks:

• 
  culture the organism
  
• 
  perform biochemical and serologic confirmatory tests
  
• 
  perform minimum inhibitory concentration (MIC) agar dilution testing of anti-microbial agents.
  

If the national reference laboratory does not have this capacity, it may send isolates to a regional laboratory in another country for testing. An isolate is a culture of bacteria or other cells.

• 
  Regional networks supported by WHO Collaborating Centres have been established in several WHO regions to conduct anti-microbial susceptibility testing for N. gonorrhoeae.
  
• 
  National reference laboratories are encouraged by WHO and UNAIDS to participate in these centres' programmes of quality control and assessment.
  

Frequency of

assessment

The assessment of anti-microbial resistance should be performed at least once a year. When feasible, it is best to sample isolates on an ongoing basis rather than during only one month or quarter per year. For example, you can test 20 isolates per month at each sentinel site throughout the year. Ongoing sampling makes it more likely that newly emerging resistance or large changes in patterns of resistance will be detected early.

In view of the increasing rates of drug-resistant pathogens worldwide, it is important for each country to monitor anti-microbial resistance in Neisseria gonorrhoeae as a core component of STI surveillance.