Rosario Achí

Detection of shigella in lettuce by the use of a rapid molecular assay with increased sensitivity.

A Multiplex Polymerase Chain Reaction (PCR) assay to be used as an alternative to the conventional culture method in detecting Shigella and enteroinvasive Escherichia coli (EIEC) virulence genes ipaH and ial in lettuce was developed. Efficacy and rapidity of the molecular method were determined as compared to the conventional culture. Lettuce samples were inoculated with different Shigella flexneri concentrations (from 10 CFU/ml to 107 CFU/ml). DNA was extracted directly from lettuce after inoculation (direct-PCR) and after an enrichment step (enrichment PCR). Multiplex PCR detection limit was 104 CFU/ml, diagnostic sensitivity and specificity were 100% accurate. An internal amplification control (IAC) of 100 bp was used in order to avoid false negative results. This method produced results in 1 to 2 days while the conventional culture method required 5 to 6 days. Also, the culture method detection limit was 106 CFU/ml, diagnostic sensitivity was 53% and diagnostic specificity was 100%. In this study a Multiplex PCR method for detection of virulence genes in Shigella and EIEC was shown to be effective in terms of diagnostic sensitivity, detection limit and amount of time as compared to Shigella conventional culture.

Serum antibody titres to shigella lipopolysaccharides and invasion plasmid antigens in healthy Costa Rican and Swedish women

Specific serum antibody titres to defined lipopolysaccharides (LPS) of Shigella spp. and Salmonella serogroup B (BO) and Shigella invasion plasmid antigens (Ipa) were determined by enzyme immunoassays in healthy Costa Rican women from low (n = 34), middle (n = 36) and high (n = 19) socioeconomic conditions and from 64 Swedish women. Specific IgG antibody titres were the highest, in particular to the S. flexneri Y LPS, with mean titres of 750 (SD = 360), 690 (380), and 820 (300) for the Low, Middle and High Costa Rican groups respectively. Lower titres were recorded against S. sonnei and S. dysenteriae type 1. Titres against Salmonella LPS were very low (< 250). In Swedish women, significantly lower serum anti-LPS titres were found (p < 0.05). No statistically significant differences regarding socioeconomic conditions or serum anti-LPS titres were seen in the Costa Rican groups (p > 0.05). Mean IgG-titres to the Ipa of 330 (150), 220 (170) and 140 (110) were found for the 3 Costa Rican groups, respectively. The IgG and IgM titres to Ipa in serum from the Low group were significantly higher than those of the High group (p < 0.05). The mean serum IgG titre of 70 (90) for the Swedish women was significantly lower than that of the Low and Middle groups (p < 0.05), but similar to that of the High group (p > 0.05). High IgG anti-Ipa titres were found in 38% from the Low, 19% from the Middle but none in the High group (mean value of the High group +2 SD).(ABSTRACT TRUNCATED AT 250 WORDS)

The CDRC principles of international health research

The Comprehensive Drug Research Center (CDRC) at the University of Miami was established in the early 1970s. Through the decades, investigators from the CDRC have worked with investigators from several countries to establish joint research efforts. Countries often do not have the infrastructure or monetary resources to carry out research on their own. Collabo rating with institutions in these countries to build a sustainable capacity for research is a worthwhile and satisfying endeavor, and it presents a method for initiating research and building the necessary research structures. However, working with other countries presents a unique set of challenges and ethical dilemmas. this article presents some of the specific challenges encountered in these research efforts and describes what we have done to resolve the problems and work more effectively and efficiently with foreign investigators.

The importance of integrons for development and propagation of resistance in Shigella: the case of Latin America

In Latin America, the disease burden of shigellosis is found to coexist with the rapid and rampant spread of resistance to commonly used antibiotics. The molecular basis of antibiotic resistance lies within genetic elements such as plasmids, transposons, integrons, genomic islands, etc., which are found in the bacterial genome. Integrons are known to acquire, exchange, and express genes within gene cassettes and it is hypothesized that they play a significant role in the transmission of multidrug resistance genes in several Gram-negative bacteria including Shigella. A few studies have described antibiotic resistance genes and integrons among multidrug resistant Shigella isolates found in Latin America. For example, in Brazil, Bolivia, Chile, Costa Rica and Peru, class 1 and class 2 integrons have been detected among multidrug resistant strains of Shigella; this phenomenon is more frequently observed in S. flexneri isolates that are resistant to trimethoprim, sulfamethoxazole, streptomycin, ampicillin, chloramphenicol, and tetracycline. The gene cassette sul2, which is frequently detected in Shigella strains resistant to the sulfonamides, suggests that the sulfonamide-resistant phenotype can be explained by the presence of the sul2 genes independent of the integron class detected. It is to be noted that sul3 was negative in all isolates analyzed in these studies. The high frequency of sulfonamide (as encoded by sul2) and trimethoprim resistance is likely to be a result of the recurrent use of trimethoprim sulfamethoxazole as a popular regimen for the treatment of shigellosis. The observed resistance profiles of Shigella strains confirm that ampicillin and trimethoprim-sulfamethoxazole are ineffective as therapeutic options. In-depth information regarding antibiotic resistance mechanism in this pathogen is needed in order to develop suitable intervention strategies. There is a pressing need for regional and local antimicrobial resistance profiling of Shigella to be included as a part of the public health strategy.