Molecular phylogeny and biogeographic history of the Neotropical tribe Glandulocaudini (Characiformes: Characidae: Stevardiinae)

Although former studies on systematics and biogeography represent a progress on the knowledge of the tribe Glandulocaudini, none was grounded on molecular evidence. Thus, the first hypothesis of relationships for the tribe based on a multilocus analysis is presented, including all genera and most of the valid species. DNA sequences of Glandulocauda caerulea and Mimagoniates sylvicola were analyzed for the first time. A molecular clock analysis was used to estimate the origin of the Glandulocaudini and the approximate timing of cladogenetic events within the group. Glandulocaudini was recovered as monophyletic. No hypothesis recovered Glandulocauda as monophyletic, since G. melanopleura is sister to Lophiobrycon weitzmani while G. caerulea is closely related to Mimagoniates. The relationships within the latter genus were resolved. The molecular clock results indicate the origin of the Glandulocaudini during the Miocene with diversification in the group occurring from Neogene to Pleistocene. These results corroborated the hypothesis that its origin took place on the Brazilian crystalline shield with the subsequent occupation of the Atlantic Coastal drainages. Apparently, Pleistocene sea-level fluctuations might have shaped the distribution pattern of some species in Glandulocaudini.(AU)

Embora estudos prévios sobre sistemática e biogeografia representam um avanço no conhecimento da tribo Glandulocaudini, nenhum foi baseado em evidência molecular. Assim, a primeira hipótese de relações para a tribo com base em uma análise multilocus é apresentada, incluindo todos os gêneros e a maioria das espécies válidas. Sequências de DNA de Glandulocauda caerulea e Mimagoniates sylvicola foram analisadas pela primeira vez. Uma análise de relógio molecular foi utilizada para estimar a origem de Glandulocaudini e datas aproximadas de eventos cladogenéticos dentro do grupo. Glandulocaudini foi recuperada como monofilética. Nenhuma hipótese recuperou Glandulocauda como monofilético, uma vez que G. melanopleura é irmã de Lophiobrycon weitzmani e G. caerulea está proximamente relacionada a Mimagoniates. As relações dentro deste último gênero foram resolvidas. Os resultados do relógio molecular indicam que Glandulocaudini originou-se durante o Mioceno, com diversificação dentro do grupo ocorrendo desde o Neogeno até o Pleistoceno. Estes resultados corroboram a hipótese da sua origem no escudo cristalino brasileiro, com a subsequente ocupação das drenagens costeiras atlânticas. Aparentemente, as flutuações pleistocênicas do nível do mar podem ter moldado o padrão de distribuição de algumas espécies em Glandulocaudini.(AU)

Occurrence and characterization of livestock-associated methicillin-resistant Staphylococcus aureus in pig industries of northern Thailand

This study was conducted to determine the prevalence of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in pigs, farm workers, and the environment in northern Thailand, and to assess LA-MRSA isolate phenotypic characteristics. One hundred and four pig farms were randomly selected from the 21,152 in Chiang Mai and Lamphun provinces in 2012. Nasal and skin swab samples were collected from pigs and farm workers. Environmental swabs (pig stable floor, faucet, and feeder) were also collected. MRSA was identified by conventional bacterial culture technique, with results confirmed by multiplex PCR and multi locus sequence typing (MLST). Herd prevalence of MRSA was 9.61% (10 of 104 farms). Among pigs, workers, and farm environments, prevalence was 0.68% (two of 292 samples), 2.53% (seven of 276 samples), and 1.28% (four of 312 samples), respectively. Thirteen MRSA isolates (seven from workers, four from environmental samples, and two from pigs) were identified as Staphylococcal chromosomal cassette mec IV sequences type 9. Antimicrobial sensitivity tests found 100% of the MRSA isolates resistant to clindamycin, oxytetracycline, and tetracycline, while 100% were susceptible to cloxacillin and vancomycin. All possessed a multidrug-resistant phenotype. This is the first evidence of an LA-MRSA interrelationship among pigs, workers, and the farm environment in Thailand.

Prevalence and characteristics of Shiga toxin-producing Escherichia coli (STEC) from cattle in Korea between 2010 and 2011

A total of 156 Shiga-like toxin producing Escherichia coli (STEC) were isolated from fecal samples of Korean native (100/568, 18%) and Holstein dairy cattle (56/524, 11%) in Korea between September 2010 and July 2011. Fifty-two STEC isolates (33%) harbored both of shiga toxin1 (stx1) and shiga toxin2 (stx2) genes encoding enterohemolysin (EhxA) and autoagglutinating adhesion (Saa) were detected by PCR in 83 (53%) and 65 (42%) isolates, respectively. By serotyping, six STEC from native cattle and four STEC from dairy cattle were identified as O-serotypes (O26, O111, O104, and O157) that can cause human disease. Multilocus sequence typing and pulsed-field gel electrophoresis patterns highlighted the genetic diversity of the STEC strains and difference between strains collected during different years. Antimicrobial susceptibility tests showed that the multidrug resistance rate increased from 12% in 2010 to 42% in 2011. Differences between isolates collected in 2010 and 2011 may have resulted from seasonal variations or large-scale slaughtering in Korea performed to control a foot and mouth disease outbreak that occurred in early 2011. However, continuous epidemiologic studies will be needed to understand mechanisms. More public health efforts are required to minimize STEC infection transmitted via dairy products and the prevalence of these bacteria in dairy cattle.

Dissimilarity of ccrAB gene sequences between methicillin-resistant Staphylococcus epidermidis and methicillin-resistant Staphylococcus aureus among bovine isolates in Korea

The sequences of the ccrAB genes from bovine-, canine- and chicken-originating methicillin-resistant Staphylococcus (S.) epidermidis (MRSE) and bovine methicillin-resistant Staphylococcus (S.) aureus (MRSA) were compared to investigate the frequency of intra-species horizontal transfer of the staphylococcal cassette chromosome mec (SCCmec) complex. Nineteen MRSE strains were isolated from bovine milk, chickens, and dogs, and their genetic characteristics were investigated by multilocus sequence typing and SCCmec typing. Among the animal MRSE strains, the most frequent SCCmec type was type IV, which consisted of the type B mec complex and ccrAB type 2. The ccrA2 and ccrB2 genes were sequenced from the bovine, chicken and canine MRSE strains and compared with those of the bovine MRSA strains. The sequences generally clustered as MRSA and MRSE groups, regardless of the animal source. Additionally, no bovine MRSE sequence was associated with the bovine MRSA groups. Although most of the bovine MRSE and MRSA isolates possessed SCCmec type IV sequences, our results suggest that the intra-species gene transfer of the SCCmec complex between bovine S. aureus and bovine S. epidermidis strains is not a frequent event.