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[Editor’s note: This is the second in a series of posts covering topics related to drug resistance, including causes, effects, what is being done to fight drug resistance, and what needs to be done to limit the harm caused by drug-resistant pathogens. The first post is available here.]

The failure of antiretroviral therapy and the appearance of drug-resistant HIV strains continue to hinder efforts to keep HIV-positive individuals healthy. Unfortunately, the tests needed for early detection of antiretroviral therapy failure and drug resistance are expensive and not widely available in many countries with a high HIV prevalence. But the provision of such tests may benefit from an unusual source: old shipping containers.

Immunological and viral load testing are necessary to slow the emergence and spread of drug-resistant HIV strains. A recent meta-analysis published in The Lancet Infectious Diseases revealed that patients whose viral loads were monitored frequently (at 3-month intervals) were less likely to harbor drug-resistant HIV viruses at the time of virological failure than patients who were monitored less frequently or not at all. (Virological failure occurs when drugs are no longer able to suppress HIV replication and viral loads increase. Patients with viral loads of 1000 viral RNA copies per milliliter of blood or higher are considered to have experienced virological failure.)

Numerous studies have shown that resistant HIV viruses can be transmitted, causing some newly infected individuals to harbor HIV viruses resistant to antiretrovirals even before beginning treatment. The possibility of transmission of resistant viruses makes the expansion of viral load testing even more important — monitoring the viral loads of patients on antiretroviral therapy (ART) not only protects the patient from the harmful effects of virological failure and the emergence of drug resistant strains but it also protects the patient’s sexual partners (and the partner’s partners, and so on) from drug-resistant HIV. Read more

[Editor’s note: This is the first in a series of posts covering topics related to drug resistance, including causes, effects, what is being done to fight drug resistance, and what needs to be done to limit the harm caused by drug-resistant pathogens.]

The discovery of penicillin in 1928 was one of the greatest medical discoveries to date, and since their introduction, penicillin and other antibiotics have saved an incredible number of lives. Unfortunately, it didn’t take long for the bacteria to fight back.

The discovery of penicillin-resistant bacteria within a year of the first clinical use of the antibiotic would serve as a sign of things to come. Today, there are few (if any) widely used antimicrobial drugs that have not been rendered less effective by the emergence of resistant pathogen strains. The fast replication cycles of bacteria and viruses and the mistakes made by their replication machinery give these pathogens the ability to respond to and overcome drug pressures. With penicillin, for example, replication errors allowed some formerly penicillin-sensitive bacteria strains to evolve so that the targeted bacterial proteins no longer interact with the antibiotic. Other bacterial strains acquired new genes that allow them to produce proteins that degrade penicillin, rendering it ineffective and allowing these bacteria to survive.

Drug resistance continues to be a major obstacle in reducing the prevalence of the “big three” infectious diseases: HIV/AIDS, tuberculosis (TB), and malaria. The recent emergence of malaria strains resistant to artemisinin, one of the most effective anti-malarial drugs and sometimes the only drug that can effectively kill the deadly Plasmodium falciparum parasite, serves to highlight how troublesome — and downright frightening — drug resistance can be. Read more

Two new studies suggest promising methods of detecting and treating TB despite discouraging reports about the increasing global prevalence of multi-drug resistant tuberculosis (MDR-TB) and extensively-drug-resistant tuberculosis (XDR-TB). The first study underlines the importance of follow-up visits in detecting TB among immigrants and asylum seekers entering the US. While screening is crucial in preventing the spread of TB, identifying TB-infected persons can be difficult; blood or sputum smear testing can take weeks to complete and has only a 50% accuracy rate. Screening of immigrants and asylum seekers is especially important, as the TB rate in foreign-born persons is 9.7 times higher than in US-born persons. Researchers found that follow-up visits with immigrants after their entry into the US were effective in identifying and reducing the number of TB patients in the US.

The World Health Organization estimated 9.27 million cases of TB in 2007, a significant increase from 6.6 million cases in 1990. The majority of these cases are found in the South-East Asia region, which accounts for 34% of all new cases, and sub-Saharan Africa, which has the highest TB mortality rate in the world. People with health conditions that weaken the immune system like HIV infection, substance abuse, or malnutrition are more susceptible to the disease. A recent study showed that one-fourth of all TB-related deaths were in patients who were also HIV-positive.

No new classes of TB drugs have been created since the 1960s, and few clinical trials have been conducted using modern regulatory standards. To address this need, research groups are focusing on novel approaches to TB therapeutics. The Global Alliance for TB Drug Development (TB Alliance) recently announced four research partnerships that will explore new methods of treating drug-resistant TB. One of these collaborations, led by Anacor Pharmaceuticals, will provide any new compounds developed to the TB Alliance royalty-free. Read more