I Smell a Rat—Smelling TB?

Source: NewScientist.com. News Service. December 16, 2003.

The World Bank is funding a novel project to train 30 giant pouched rats to sniff out tuberculosis (TB) in respiratory specimens in Sub-Saharan Africa. Rats have been previously successfully trained to target landmines, and a similar training/reward technique is being used with this project. Preliminary results look encouraging. In pilot trials, 5 rats were trained to detect the smell of TB in 10,000 respiratory specimens, and 5 were trained to target TB in cultures. Compared with trained technicians using light microscopy (~95% accuracy), the rats were able to accurately detect TB in 77% of positive smears and 92% of positive cultures—with less than a 2% false-positive rate. Although the rats may not be quite as accurate as trained humans, they are much faster with less prep time. While it takes a trained technician about 1 day to prep and review 20 specimens, a single rat can sniff up to 150 specimens in just 30 minutes.

Aerosolized E coli 0157 at a County Fair

Source: Varma JK, et al. JAMA. 2003; 290:2709-2712.

Aerosolization of E coli 0157 is a novel concept, never previously considered until recently when a series of 3 outbreaks possibly caused by exposure to contaminated buildings (or air space) occurred—at the University of Wisconsin, the Lane County Fair in Oregon, and the Lorain County Fair in Ohio. In the latter outbreak, at least 23 people who attended the Lorain County Fair developed laboratory-confirmed infection with E coli 0157 within 7 days of attending the fair in August 2001. Six patients required hospitalization, and 2 (9%) developed hemolytic uremic syndrome. Nineteen of the 23 patients had attended a dance in an exhibition hall, usually used for exhibition of large livestock.

A case-control study was conducted matching the 23 cases (average age, 15 years), to 53 age-matched controls, all of whom attended the fair but did not develop diarrhea. Case patients were more likely than controls to have visited the exhibition hall. Specific risk factors included attending the dance in the exhibit hall, handling the sawdust from the floor, and eating or drinking in the hall. Six weeks after the fair, Shiga-toxin producing E coli 0157 was isolated from 22 of 54 specimens obtained from the exhibit hall, including the sawdust, rafters, and other surfaces. Ten months later, the same E coli could still be isolated from specimens obtained from the building.

Talk about "sick building syndrome." E coli is known to survive in the environment for long periods of time, but even this case, with isolation of the same organism from the building 10 months later, was surprising to those involved. It sounds as if the dust kicked up in the air (possibly by the dancing?) was either inhaled or settled and was ingested on food or drink. Once again, it sounds like activities involving eating and drinking should not occur in the same space where livestock defecate. So much for good old-fashioned barn dances, at least without changing the hay.

Fatal Illness Strikes Traveler

Source: MMWR Morb Mort Wkly Rep. 2004;52:1285-1286.

How quickly can you guess this case? A 63-year-old previously healthy man traveled to Haiti for one week in October 2003, to help build a church in a more rural area. On the final day of his trip, he developed a sore throat. Two days later, back in the United States, he presented to a local emergency room in Pennsylvania with worsening sore throat and difficulty swallowing. Despite a negative rapid strep screen, he received Augmentin. Two days later, he was admitted to hospital with progressive throat pain, neck swelling, and, over the next few days, developed pulmonary infiltrates and respiratory failure. Although epiglottitis was originally suspected, laryngoscopy revealed thick yellow exudates coating the throat. However, cultures were negative for C diphtheriae.

Despite treatment with broad-spectrum antimicrobials (including azithromycin, ceftriaxone, and nafcillin) and steroids, he clinically deteriorated, requiring transfer to a tertiary care facility. There, while being trached on the eighth day of illness, thick white pseudomembranes were visualized covering the supraglottic structures. Repeat cultures for C diphtheria were negative, but specimens forwarded to the CDC were subsequently positive for C diphtheriae tox genes by PCR. Despite continued treatment with antibacterials and receipt of diphtheria anti-toxin (DAT) on the ninth day of illness, he died of cardiac complications.

While diphtheria remains uncommon in the United States, travelers to areas endemic for this infection remain at risk if they have not been adequately vaccinated. Sporadic cases continue to occur (only 53 cases have been reported to the CDC between 1980 and 2001), largely in unvaccinated older adults. While > 95% of children in the United States have been adequately vaccinated, coverage amongst older adults is lower; the man described above had never been vaccinated to diphtheria. Serologic studies performed in 1988-1994 indicate that adequately protective antibodies decrease progressively with age, from 91% at ages 6-11 years to ~30% at age 60-69 years.

This unfortunate case serves as a reminder that DAT should be administered as soon as diphtheria is suspected and should not be based solely on the results of cultures (which may be negative in partially treated cases). It is crucial to neutralize the toxin before it enters cells. The duration of illness roughly correlates with the severity of symptoms and the degree of membrane formation, which roughly correlates with toxin burden. More established illness therefore requires greater amounts of antitoxin. Although not specifically addressed in this report, myocarditis is one of the complications of diphtheria and may have explained this man’s cardiac demise.

Any international travelers- regardless of age or other health issues—and especially those traveling to areas where diphtheria remains endemic (www.cdc.gov/ travel/diseases/dtp.htm)—should receive a primary series ( > 3), including a booster of diphtheria-containing toxoid within the previous 10 years.

VZV Reactivation in Astronauts

Source: Mehta SM, et al. J Med Virol. 2004;72:174-179.

Stress is a known trigger for reactivation of herpes viruses. Just the physical and psychological trauma of swapping alpha-male mice between 2 mouse colonies and the resultant battle for new alpha-male-dom has been shown to trigger reactivation of HSV in about half the mice. Herpes zoster can also reactivate after stress, including the stress of surgery.

After a 47-year-old healthy astronaut developed herpes zoster 2 days before a space flight, Mehta and associates decided to examine whether the stress of space flight can result in the reactivation of VZV. A total of 312 saliva samples, obtained from 8 astronauts before, during, and after space flight were examined by PCR. Amazingly, 61 of 200 (30%) specimens obtained during and after space flight were positive, compared with 1 of 112 (< 1%) obtained in a 234-265 day period before flying. No VZV was detected in 88 samples from 10 control subjects, who did not fly. Seven of 8 astronauts had at least 1 positive specimen during flight (2-12 days), while all 8 had anywhere from 1-8 positive specimens within 15 days of returning to earth.