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Updates

By Carol A. Kemper, MD, FACP

May 1, 2013
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By Carol A. Kemper, MD, FACP, Section Editor: Updates, Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases; Santa Clara Valley Medical Center, is Associate Editor for Infectious Disease Alert.

Crossing the border with highly resistant TB

Tuberculosis, XDR – USA: Texas ex Nepal. A ProMED-mail post, March 1 2013; www.promedmail.org

This ProMED-mail alert describes the world-wending saga of a man from Nepal with smear-positive extremely-drug resistant tuberculosis (XDR-Tb), who arrived in the United States in late November 2012. In order to enter the United States (illegally), he traveled thru 13 different countries over a 3-month period, including an 8-hour air flight to Brazil, before crossing the border from Mexico into the U.S. near McAllen, Texas. It is not possible to reconstruct his journey nor adequately identify and screen the thousands of people exposed during his journey, but the CDC and WHO have been notifying affected countries. Twelve border patrol agents who were exposed have all tested negative for infection.

This man, who has not been identified, is the first individual with XDR-Tb detained by U.S. immigration authorities. A total of 4 cases of XDR-Tb were reported in the U.S. for 2011 (all of them were foreign born).

XDR-Tb is by definition resistant to at least 3 classes of drugs, including isoniazid, rifampin and/or rifabutin, fluoroquinolones, and at least one injectable agent (e.g., streptomycin). This man has a strain of tuberculosis resistant to at least 8 of 15 drugs tested.

We were involved with a similarly scary case in December 2012 at our hospital in Mt. View, CA, when a 30-year old Nepalese man with smear-positive Tb required hospitalization. He worked as an aide at a local academic medical facility. Thought to possibly be an XDR case, based on preliminary resistance data, his isolate proved resistant to isoniazid, rifampin, rifabutin and streptomycin but was sensitive in vitro to fluoroquinolones (making him only MDR-TB). Quite frustrated with his 4-week hospitalization, he attempted to elope from the hospital one afternoon, and was practically tackled by my colleague in the hall. On examining the family, the local public health department found that his sister had 4+ smear-positive pulmonary disease and both children had abnormal chest radiographs. Concurrently, I was also asked to consult in the clinic on a young woman recently arrived from India with smear-positive pulmonary disease, who also proved to have 4-drug resistant MDR-TB. Their strains were genetically different.

Physicians must be on guard for the increased potential for multi- and extremely-drug resistant TB, especially in foreign born persons from India and Nepal. Both countries have seen a dramatic increase in drug-resistant strains. While Nepal (which reported 35,000 cases of MTb in 2011) has made good public health efforts to control the disease, they are faced with the highest rates of multi-drug resistant disease (up to 48%).

 

Fecal Transplant Centers are growing in ‘poopularity’

Jiang Z, et al. Physician attitudes toward the use of fecal transplantation for recurrent Clostridium difficile infection in a metropolitan area. Clin Infect Dis 2013; 56: 1059-1060.

On the heels of last month’s “poopular” fecal transplant article, these authors from the University of Texas and Baylor Medical School in Houston, Texas conducted a survey of local physicians’ attitudes towards fecal transplant. The survey was intended to determine whether there was local community physician support for a fecal transplant treatment center in the area. Two-hundred-and-four local gastroenterologists and ID specialists were queried, only 33% of whom responded. The majority of physicians who responded were in favor of fecal transplant treatment (65% of gastroenterologists and 69% of ID specialists). A significant percent of these indicated they would be willing to refer patients to a local fecal transplant center for treatment, if one were available (89% of gastroenterologists and 81% of ID specialists).

The authors suggest that academic medical facilities develop local treatment programs for fecal transplantation , employing the latest techniques and emerging technologies (e.g., frozen fecal material from a single donor, synthetic fecal products that mimic fecal microbiota), to assist the community in managing patients refractory to other C difficile treatments.

 

Bedbug Detection Squad

Vaidyanathan R and Feldlaufer MF. Bed bug detection: Current technologies and future directions. Am J Trop Med and Hyg 2013;88:619-625.

Remember that scene in Doc Martin when he travels to London for a conference, and while his lady awaits his affection in a tiny negligee, he methodically strips the bed looking for bed bugs ? How many of us make that a habit now when traveling ?

Detection and control of bedbugs has become a busy industry the past decade, as estimates suggest 100-fold increase in the bed bug population. Bed bug bites vary from a few annoying bites to dramatic infestations, sometimes resulting in severe allergic reactions, delayed hypersensitivity reactions and even anemia. I’ve seen patients come in with hundreds of bites, desperate for information and relief.

There are a number of methods and technologies to detect (and possibly control) bed bug infestations, including newer technologies pending patent. Visual inspection of beds and furniture for bugs, exuviae and fecal droplets is cheap and easy — but you have to know what you’re looking for and accuracy drops off with lesser infestations. It is also time-consuming (having to remake all those beds). There are a number of passive methods used, most of which employee glue or adhesive “traps”, which vary in price from a few cents to $30 for a 12-pack. These are undoubtedly better than passive inspection, especially if you are staying in a place for more than one night. But the traps must be manually removed and inspected, and they often have a mix of live and dead bugs stuck to them — and the traps are not specific for bedbugs so can attract other insects (some people might object to this). Another passive method is a coaster trap for furniture and bed legs, which can be left for a week at a time, and reportedly trap 6-7 times the bed bugs of other passive traps. But they too need to be removed and inspected, and are also non-specific for bed bugs. They cost anywhere from $34 to $80 for a 12-pack.

Active traps can employee a number of methods, including heat and CO2, which are the two most effective attractants, bringing in bugs at night wanting to feed. Traps based on CO2 productions are, however, more costly, varying in price from $400 to $999, and require refillable CO2 cartridges. In addition to cost, these systems also require visual inspection and removal of traps with live bugs and their feces, and operators often complain about the bulky cartridges, mechanical problems with the dispersal systems, and the constant hissing sound of the carbon dioxide being dispersed. One study found that a homemade passive trap using dry ice was more successful than more expensive commercial traps using CO2 — the homemade dry ice system caught as many bugs in one day as the more expensive traps caught in a week.

Newer active trap systems, based on an increased understanding of bed bug interactions and chemical communication, are being developed. Two “alarm” pheromones have been identified, specific to bed bugs, and have been incorporated into active traps. They can also be used in part as a control strategy, because they are more effective at attracting bugs. Bedbugs have also been found to use another pheromone to signal gregarious behavior (called a kairomone), which seems to promote aggregation behavior, thereby possibly allowing better control of infestations. Such systems are advertised for $30 for a 90 day supply.

Pest control companies have also used trained canines for bed bug detection. While it is not entirely clear what the dogs are smelling, they presumably are responding to some combination of volatile pheromones or chemicals in bug excrement. These authors found that a trained dog identified live bed bugs, filter paper with a mix of the two alarm pheromones, and cast skins 100% of the time, although they commented that this was in a clean, well appointed office building. Lower detection rates have been reported when dogs are used in crowded urban settings. One issue with the use of dogs is they may not be able to detect a current infestation from a past infestation, and the dogs can only detect the presence of bed bugs — not reduce their numbers. Newer technologies based on antigens from digested human blood in bed bug feces are also being explored — but again have the disadvantage of not being able to detect current from past infestations. Other technologies based on mass spectrometry, DNA analysis and electronic noses are accurate but impractical for commercial home use.