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Welcome to this week’s Monday Micro!

First, an update on the on-going US meningitis outbreak caused a fungal-contaminated steroid made by the New England Compounding Company. The case count has risen to 404 and the number of deaths to 29. But patients are also starting to present with another symptom – nasty and painful abscesses at the site of injection (mostly near the spine). Apparently most abscesses can be cleared by draining and surgery but sometimes the fungal hyphae can wrap around the nerves, meaning they can’t be surgically removed. Yikes! As more than 14,000 people are thought to have been injected with vials from the recalled contaminated lots, it’s likely the number of cases is going to continue to rise.

And speaking of contamination, according to an article in the Telegraph, 160,000 doses of the Novartis flu vaccine Agrippal are being recalled in the UK as a precaution after ‘particles’ were found in the vials. Novartis say these are protein aggregates that can occur naturally and will dissolve when shaken.

In other news, the Ugandan Ministry of Health has reported an outbreak of Marburg haemorrhagic fever (MHF) in south-western Uganda. As of October 28, 18 cases and 9 deaths have been reported. MHF is from the same family of viruses as Ebola and is thought to be initially caught from handling ill or dead infected wild animals such as monkeys and fruit bats. Marburg is also transmitted by direct contact with the blood, body fluids and tissues of infected people. Which reminds me, go read Richard Preston’s The Hot Zone for a great introduction to haemorrhagic viruses.

And finally, a study just out in science is shedding new light into how old drugs work. Para-aminosalicylic acid (PAS), commonly used to treat TB, was believed to work by interfering with a bacterial enzyme necessary for the synthesis of an essential nutrient called folate. Folate is a key precursor in DNA base synthesis, so interfering with its production is an effective strategy because, unlike bacteria, people have no folate-synthesizing pathways to disrupt. Instead we get folate from our diet.

Kyu Rhee and his colleagues at Weill Cornell Medical College have discovered that PAS is actually processed by its mycobacterial target enzyme into anti-bacterial products that inhibit bacterial growth through a number of different mechanisms. This is an important finding, as many drug discovery projects are based on identifying compounds that target key bacterial enzymes. Instead, this work suggests that finding drugs that are broken down into toxic compounds might be a better strategy.

Reference: S. Chakraborty et al., “Para-aminosalicylic acid acts as an alternative substrate of folate metabolism in Mycobacterium tuberculosis,” Science, doi: 10.1126/science.1228980, 2012.