Trachoma

So I went to an interesting talk on the role of water and sanitation on incidence of Trachoma, and for the first time in recent memory, somebody besides me used the word “fomites”.  So I naturally wanted to blog all about it.

Trachoma is an infectious eye disease caused by Chlamydia trachomitis.  [Side note: inour lab safety training, the safety coordinator tells a story about how she got Chlamydia in her eye when she was working in the lab]  A typical infection, which lasts for 5-12 days, causes conjunctivitis-like symptoms, with eye inflamation leading to irritation and discharge.  If you visited the poorest of regions in Africa, Asia, the Middle East, and/or Latin America, and ended up with Trachoma, it’d be no big thing.  Your doctor would hand you antibiotics like he always does and you’d keep on walking.  But the locals who are continually re-infected with Trachoma end up with permanent blindness.  The constant inflamation from repeat infections leads to entropian, a painful form of blindess, which (according to Wikipedia) is the leading cause of infectious blindness.

Gross.

So trachoma is spread through contact with eye, nose, and throat secretions.  Either by direct contact, indirect contact via fomites, or indirect contact via vectors (like flies and cattle).  People who like the F-diagram say it is spread through feces, flies, fomites, and fingers.

The fomites in question are thought to be items like towels, but the speaker mentioned that the cloths women use to wrap and hold their babies [is kitenge the right word?  When i Googled it, i just got a bunch of photos of the whitest people wrapping random African-looking cloths around themselves and their sun-deprived babies,  so there's probably a better word out there] rubs right against the baby’s eyes, allowing discharge from one infection to continually cause reinfection.

So secretions appear to be the main form of transmission, but the speaker’s premise for the talk was that sanitation would reduce incidence of Trachoma because it would remove feces from areas where individuals and flies had access.  In general, promoting sanitation is always a great thing, but I’m not completely sold on its usefulness in combating an infectious disease spread through secretions.

And, perhaps, neither are the individuals at WHO working on its elimination who apparently rely heavily on the use of antibiotics to treat individuals, instead of trying to interrupt the transmission pathway.

 

Triclosan – Where Microbiology and Toxicology Collide.

Hitting the innerwaves today, care of ES&T,  is an article on EPA’s approval of Triclosan.   Triclosan is found in a large number of consumer products (e.g.  soaps, detergents, deodorants, mouth wash, and toothpaste).  Colgate Total, for example, contains triclosan to prevent gingivitas.

Triclosan is an antibacterial that binds to an enzyme in bacteria that is used to build fatty acids, a necessary component in bacterial cell membranes.    Notice, I said that it is an antibacterial and not an antibiotic.

Triclosan’s efficacy in hand soap is debatable.  Some studies have shown that hand washing is not improved with the addition of triclosan, if the recommended 30 second social hand wash is followed.  Others contend that triclosan provides a residual on the hands that continues to work against bacterial contamination, useful in settings where people do not wash their hands completely or correctly.  Most consumer products, like cutting boards, table tops, and children’s toys, that bear the term antibacterial likely have triclosan imbedded in the surface.

Additionally, soap with high concentrations of triclosan (think 2% compared to the 0.5% found in consumer soaps) are used to decontaminate individuals exposed to MRSA.

So why is it news that the EPA extended triclosan’s approval?

1) There is some (ok, very little) concern about antibacterial resistance developing, which seems unlikely unless organisms currently resistant (such as P. aeroginosa) are able to transfer resistance to other species.

2) Triclosan degrades in sunlight to form byproducts in a class of compounds known as Dioxins, which bioaccumulate in fatty tissue and pose a threat to the reproductive, sexual development, and immune systems and are probable carcinogens.  With household use sending triclosan directly down the drain to the waste water treatment plant, it frequently ends up in surface waters where it becomes an environmental pollutant.

and 3) The ES&T article mentions, through Cathy Propper at NAU, that triclosan bioaccumulates and impacts nitrogen fixation in microbial communities and plants.

My take?  Totally not necessary.  Just wash your hands well.  Wash your cutting board well.  Your table top…  Why contribute to a problem we have no idea of the magnitude of for the sole benefit of maybe, possibly, protecting ourselves environmental bacteria?

We’ll see what the EPA says when it comes up again in 5 years…

 

Salmonella in Pet Food

I am a little late to the party on the contamination of pet food with Salmonella by a Mars, Inc. plant in Everson, PA.  But this may be an ongoing problem, as “71 people who have fallen ill since 2006″.  Keep in mind this is dry pet food only.  Canning wipes out microorganisms.

I’d like to point out CDC recommendations:

To prevent Salmonella infections, persons should wash their hands for at least 20 seconds with warm water and soap immediately after handling dry pet foods, pet treats, and pet supplements, and especially before preparing and eating food for humans.

These recommendations are the same for handling likely contaminated foodstuffs like raw chicken, even though this is fomes-mediated transmission, not foodborne.  The CDC also mentions feces as a source; this strain of Salmonella schwarzen-grunde can pass right through the gut of a pet without the pet showing signs of illness.  Animals are definitely not vectors in this.

The CDC states that children should be kept away from “pet feeding areas” and not be allowed to “touch or eat pet food”.  This added emphasis on children is because they are disproportionally becoming ill:  the median age is 8 months and six of the eight diagnosed are <2 yo.  This disparity is probably due to an increased likelihood of reporting.  Poor immunity probably also plays a large role. I doubt its level of activity or interaction with the pet food because I’d obviously expect that a greater proportion of adults are feeding their animals.  Adults who become ill are unlikely to make the connection with the dog food, and also unlikely to report to a doctor/hospital because of it.  Plus, I’d expect that children in the 2-5 yo age range are the most likely to  unintentionally eat pet food, not the <2 yo age range.   It would be nice to have information on this, though.  The route of transmission is probably pet food/feces-to-parent-to-child.

So, wash your hands.