Tips from the journals of the American Society for Microbiology

String Test: Effective and Inexpensive Method for Detecting Helicobacter pylori

Swallowing a string may offer a simple and effective alternative to costly and invasive techniques used for detecting Helicobacter pylori in patients say researchers from the U.S. and abroad. They report their findings in the March 2006 issue of the Journal of Clinical Microbiology.

Helicobacter pylori is a gram negative bacterium known for causing chronic gastric distress in individuals worldwide and can lead to the development of peptic ulcers and early onset of gastric cancer. Current methods for detecting H. pylori infection do provide highly sensitive and specific results, but they can be costly, invasive, and uncomfortable.

In the study 35 patients with gastric complaints were administered the string test (or Entero test) which involves swallowing a capsule with a protruding absorbent string whose end is held outside the mouth. The ingested string is then retrieved and microbes from the gastrointestinal tract are recovered and studied. H. pylori was cultured from 80% of the strings of those patients who had also undergone extensive biopsy procedures and received positive results. No organisms were found on strings taken from patients whose biopsy results were negative.

"Our study shows that the string test, which is minimally invasive, inexpensive, and not dependent on sophisticated or costly equipment or radioactivity, allows culture of H. pylori from infected persons about 80% as efficiently as endoscopic gastric biopsies," say the researchers. "We suggest that the H. pylori string test assays will be of increasing importance in a public health context."

(B. Velapatino, J. Balqui, R.H. Gillman, A. Bussalleu, W. Quino, S.A. Finger, L. Santivanez, P. Herrera, A. Piscoya, J. Valdivia, J. Cok, D.E. Berg. 2006. Validation of string test for diagnosis of Helicobacter pylori infections. Journal of Clinical Microbiology, 44. 3: 976-980.)

Ebola Virus Vaccine May Protect Against Sudan and Zaire Species

Researchers from South Carolina and Maryland have developed a bivalent vaccine that may protect against both the Sudan and Zaire species of Ebola virus. Their findings appear in the March 2006 issue of the Journal of Virology.

Ebola virus (EBOV) causes a severe hemorrhagic fever in humans and nonhuman primates resulting in death in 90% of those infected. Two particular species, Sudan ebolavirus (SEBOV) and Zaire ebolavirus (ZEBOV), have been responsible for the deadly human outbreaks that have occurred in Africa. To date, outbreaks have been limited to this region, however increasing international travel and bioterrorist threats have reinforced the need for an effective and swift acting vaccine.

In the study researchers vaccinated mice with a bivalent vaccine, containing both SEBOV and ZEBOV genes, and found that vaccination led to efficient induction of EBOV antibody and immune responses to both species. In addition, a group of immunized mice were challenged with a lethal dose of ZEBOV and the survival rate was 100%.

"To our knowledge, this is the first demonstration of a bivalent EBOV vaccine to coexpress multiple serotype proteins in a single vaccine construct, eliciting efficient humoral and cellular immune responses to both SEBOV and ZEBOV antigens," say the researchers.

(D. Wang, N.U. Raja, C.M. Trubey, L.Y. Juompan, M. Luo, J. Woraratanadharm, S.B. Deitz, H. Yu, B.M. Swain, K.V. Moore, W.D. Pratt, M.K. Hart, J.Y. Dong. 2006. Development of a cAdVax-based bivalent Ebola virus vaccine that induces immune responses against both the Sudan and Zaire species of Ebola virus. Journal of Virology, 80. 6: 2738-2746.)

Statistical Tool May Assist in Determining Virulence Factors for Microbes

A well established statistical tool known as multivariate linear regression may offer a new approach in determining contributions of multiple virulence factors to the overall virulence of pathogenic microbes say researchers from Albert Einstein College of Medicine, Bronx, New York and Westminster College, Salt Lake City, Utah. Their findings appear in the March 2006 issue of the journal Infection and Immunity.

Virulence is defined as the capacity of a microbe to cause damage to its host. Although there is much literature discussing the contribution of virulence factors to microbial virulence, there is no designated methodology for determining the impact of individual virulence factors on overall microbial virulence. Identification of such a method could greatly contribute to vaccine development and antimicrobial strategies.

Multivariate linear regression is a statistical tool used to analyze the relative contributions of different parameters. Out of the three types of multivariate linear regression researchers identified hierarchical regression as the type most applicable to this study. It is described as entering variables in different blocks in a specific order with the order of entry resulting from theoretical or logical importance. This approach was applied to Cryptococcus neoformans and Bacillus anthracis and results showed the method to be useful in determining the relative contributions of virulence factors in pathogenesis.

"Multivariate linear regression can be used to identify the relative levels of importance of virulence factors in virulence studies, and this information can be used to prioritize antigen identification for vaccine development and the design of antimicrobial strategies that target virulence mechanisms," say the researchers.

(E.E. McClelland, P. Bernhardt, A. Casadevall. 2006. Estimating the relative contributions of virulence factors for pathogenic microbes. Infection and Immunity, 74. 3: 1500-1504.)


Last updated: 30 Apr 2016
Last reviewed: By John M. Grohol, Psy.D. on 30 Apr 2016
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