A statistical procedure for the analysis of microbial communities based on phenotypic properties of isolates

A new Inequity-in-Health Index based on Millennium Development Goals: methodology and validation

OBJECTIVES

Developing a new Inequity-in-Health Index (IHI) assuming inequity as "inequality of health outcomes," based on Millennium Development Goals (MDG).

STUDY DESIGN AND SETTING

Ecological study. Countries from around the world were included from United Nations, the World Bank, and a nonprofit organization's databases. The reliability and validity of this bidimensional IHI was tested. Main factor analysis (promax rotation) and main component analysis were used.

RESULTS

Six variables were used for constructing the IHI was constructed with six variables: underweight children, child mortality, death from malaria in children aged 0-4, death from malaria at all ages, births attended by skilled health personnel, and immunization against measles. The IHI had high internal consistency (Cronbach's alpha=0.8504), was reliable (Spearman>0.9, P=0.0000), and had 0.3033pi around the world (range: 0pi-0.5984pi). IHI had high correlation with the human development and poverty indexes, health gap indicator, life expectancy at birth, probability of dying before 40 years of age, and Gini coefficients (Spearman>0.7, P=0.0000). IHI discriminated countries by income, region, indebtedness, and corruption level (Kruskal Wallis, P<0.01). IHI had sensitivity to change (P=0.0000).

CONCLUSION

IHI is a bidimensional, valid and reliable index to monitor MDG. A new reliable methodology for developing bidimensional indicators is shown, which could be used for constructing other ones with their corresponding scores and graphs.

Molecular characterization of lactic acid bacteria from sourdough breads produced in Sardinia (Italy) and multivariate statistical analyses of results

The objective of this work was to investigate the structure and diversity of lactic acid bacteria (LAB) communities in sourdough used for the production of traditional breads (Carasau, Moddizzosu, Spianata, Zichi) in Sardinia. 16S rDNA sequencing and Randomly Amplified Polymorphic DNA (RAPD-PCR) was applied for the identification and typing of the LAB isolated from 25 samples of sourdoughs. Multivariate statistical techniques were applied to RAPD-PCR pattern to study the biological diversity of sourdough samples. Twelve different species of LAB were identified, and most isolates were classified as facultative heterofermentative lactobacilli. Lactobacillus pentosus dominated the lactic microflora of many samples while Lactobacillus sanfranciscensis was isolated only from a limited number of samples. Although heterofermentative species represented between between 30% and 60% of the isolates in Carasau, Spianata and Zichi sourdoughs, only 2% of the isolates from Moddizzosu sourdoughs were identified as heterofermentative LAB. RAPD-PCR with a single primer followed by cluster analysis did not allow the identification of the isolates at the species level. However, a multidimensional scaling/bootstrapping approach on the RAPD-PCR patterns uncovered the diversity of the LAB communities of LAB showing differences both within and between bread types.

Diversity and dynamics of communities of coagulase-negative staphylococci in traditional fermented sausages

AIMS

Evaluation of composition and evolution of the coagulase-negative staphylococci (CNS) communities in two traditionally fermented sausages (salsiccia and soppressata lucana) produced in Basilicata, southern Italy.

METHODS AND RESULTS

A culture-dependent approach based on isolation on selective media and identification with phenotypic and molecular methods was used. Phenotypic data of 471 strains were analysed by multivariate statistical methods by using 28 strains from culture collections and 48 strains identified by molecular methods (such as 16S rDNA sequencing, species-specific PCR assays, intergenic spacer region-PCR and PCR-denaturing gradient gel electrophoresis) as a reference. The CNS microflora of the sausages was found to be dominated by different biotypes of Staphylococcus xylosus (51.2%), followed by S. pulvereri/vitulus, S. equorum and S. saprophyticus (13.4, 10.2 and 10%, respectively). Other species (S. succinus, S. pasteuri, S. epidermidis, S. warneri and Macrococcus caseolyticus) were also present at lower levels. Identification of 25% of the isolates was impossible.

CONCLUSIONS

The composition of CNS communities varied significantly with sausage type, plant and ripening time and clear differences were found among communities of salsiccia and soppressata at the end of ripening.

SIGNIFICANCE AND IMPACT OF THE STUDY

Phenotypic characterization, supported by molecular and statistical analyses, can be considered a useful approach for typing a large number of isolates and for monitoring the evolution of staphylococcal communities during sausage fermentation but does not always provide a satisfactory identification of the isolates.