[Show abstract][Hide abstract] ABSTRACT: The increasing occurrence of livestock-associated (LA) methicillin-resistant Staphylococcus aureus (MRSA) associated with the clonal complex (CC) 398 within the past years shows the importance of standardized and comparable typing methods for the purposes of molecular surveillance and outbreak detection. Multiple-locus variable number of tandem repeats analysis (MLVA) has recently been described as an alternative and highly discriminative tool for S. aureus. However, until now the applicability of MLVA for the typing of LA-MRSA isolates from different geographic origin has not been investigated in detail. We therefore compared MLVA and S. aureus protein A (spa) typing for characterizing porcine MRSA from distinct Dutch and German farms.
Overall, 134 MRSA isolates originating from 21 different pig-farms in the Netherlands and 36 farms in Germany comprising 21 different spa types were subjected to MLVA-typing. Amplification and subsequent automated fragment sizing of the tandem repeat loci on a capillary sequencer differentiated these 134 isolates into 20 distinct MLVA types. Whereas overall MLVA and spa typing showed the same discriminatory power to type LA-MRSA (p = 0.102), MLVA was more discriminatory than spa typing for isolates associated with the prevalent spa types t011 and t034 (Simpson's Index of Diversity 0.564 vs. 0.429, respectively; p<0.001).
Although the applied MLVA scheme was not more discriminatory than spa typing in general, it added valuable information to spa typing results for specific spa types (t011, t034) which are highly prevalent in the study area, i.e. Dutch-German border area. Thus, both methods may complement each other to increase the discriminatory power to resolute highly conserved clones such as CC398 (spa types t011, t034) for the detection of outbreaks and molecular surveillance of zoonotic MRSA.
[Show abstract][Hide abstract] ABSTRACT: Highly pathogenic enterohemorrhagic Escherichia coli (EHEC) O157 cause a spectrum of clinical signs that include diarrhea, bloody diarrhea, and hemolytic uremic syndrome. The current evolutionary model of EHEC O157:H7/H(-) consists of a stepwise evolution scenario proceeding from O55:H7 to a node (hypothetical intermediate) that then branches into sorbitol-fermenting (SF) O157:H(-) and non-SF (NSF) O157:H7. To identify this hypothetical intermediate, we performed single nucleotide polymorphism analysis by sequencing of 92 randomly distributed backbone genomic regions of 40 O157:H7/H(-) isolates. Overall, 111 single nucleotide polymorphisms were identified in 75/92 partial open reading frames after sequencing 51,041 nt/strain. The EHEC O157:H7 strain LSU-61 from deer occupied an intermediate position between O55:H7 and both O157 branches (SF and NSF O157), complementing the stepwise evolutionary model of EHEC O157:H7/H(-). The animal origin of this intermediate emphasizes the value of nonhuman reservoirs in the clarification of the evolution of human pathogens.
[Show abstract][Hide abstract] ABSTRACT: Multilocus variable-number tandem-repeat analysis (MLVA) was compared to multilocus sequence typing (MLST) to differentiate
hemolytic uremic syndrome-associated enterohemorrhagic Escherichia coli strains. Although MLVA—like MLST—was highly discriminatory (index of diversity, 0.988 versus 0.984), a low level of concordance
demonstrated the limited ability of MLVA to reflect long-term evolutionary events.
Full-text · Article · Aug 2011 · Journal of clinical microbiology
[Show abstract][Hide abstract] ABSTRACT: Evolution, broadly defined as a gradual development that may lead to a more advanced or complex form, is the most widely applicable scientific concept to understand processes at all scales, from the formation of Earth to human societies. In particular Charles Darwin’s theory of evolution based on heritable variation and selection is now being applied to many disciplines. Modern evolutionary thinking can thus provide a unifying theoretical framework to understand and address urgent problems of humankind, such as climate change, bioinvasions or disease epidemiology. The increasing relevance of cultural evolution and human influences on biological evolution, including its biomedical implications, also demand a reconsideration of evolutionary theory itself. However, evolutionary research and teaching do not yet bridge the gap between disciplines. For example, the humanities could benefit from fruitful feedback from the life sciences, while the life sciences could benefit from the humanities to deepen our understanding of the different meanings of evolution. Importantly, such collaborations also have great potential to advance evolutionary theories.
[Show abstract][Hide abstract] ABSTRACT: Multilocus variable number tandem repeat analysis (MLVA) is a subtyping technique for characterizing human pathogenic bacteria such as enterohemorrhagic Escherichia coli (EHEC) O157. We determined the phylogeny of 202 epidemiologically unrelated EHEC O157:H7/H- clinical isolates through 8 MLVA loci obtained in Germany during 1987-2008. Biodiversity in the loci ranged from 0.66 to 0.90. Four of 8 loci showed null alleles and a frequency < or =44.1%. These loci were distributed among 48.5% of all strains. Overall, 141 MLVA profiles were identified. Phylogenetic analysis assigned 67.3% of the strains to 19 MLVA clusters. Specific MLVA profiles with an evolutionary persistence were identified, particularly within sorbitol-fermenting EHEC O157:H-.These pathogens belonged to the same MLVA cluster. Our findings indicate successful persistence of this clone.