Genotyping and differential bacterial inhibition of Batrachochytrium dendrobatidis in threatened amphibians in Costa Rica

Detection of the Batrachochytrium dendrobatidis global panzootic lineage in Ecuadorian anurans of the Amazonian lowlands

Considerable attention has been directed to studying the infection dynamics of the fungal pathogen Batrachochytrium dendrobatidis (Bd) affecting amphibians in the high elevations of the Neotropics. However, lowland forests of the same realm remain comparatively understudied in this context. Herein, we attempt to bridge this gap by measuring the prevalence of Bd via quantitative polymerase chain reaction (qPCR) in several anuran taxa inhabiting the Amazonian lowlands in the northeast of Ecuador. To this end, we sampled 207 anurans from 10 different families, 25 different genera, and 55 distinct host species originally collected in 2008. Taxonomy (at the family level), morphology (i.e. weight and snout-vent length), and life-long aquatic dependency of hosts (i.e. aquatic index) were also compiled to serve as potential predictors of Bd infection status. Our findings revealed a relatively high Bd prevalence of 58%, with 88% of sampled anuran families testing positive for the fungus at varying proportions. Model selection involving fitting and testing several different linear models, including mixed linear models, revealed a significant negative relationship between host weight and Bd infection status (p < 0.01). However, no significant associations were observed between taxonomy, aquatic dependency, snout-vent length, and Bd infections. In addition, we only detected the global panzootic lineage of Bd (Bd-GPL) and not the Bd-Asia-2/Bd-Brazil lineage via qPCR single nucleotide polymorphism (SNP) genotyping. Our findings contribute to the understanding of Bd dynamics in the Neotropical lowlands and emphasize the need for future research on the ecological factors influencing Bd in the Amazon and their implications for amphibian conservation.

Culturable bacterial flora of juveniles of Pelophylax ridibundus (Pallas, 1771) and influence of abiotic factors on diversity

This study aims to determine the bacterial flora on the skin surface of the juvenile forms of Pelophylax ridibundus inhabiting three different altitudes and examine potential correlations between bacterial diversity, ecological location, and factors. It was attempted to characterize thirty-two bacteria isolated from the Melet River, Sülük Lake, and Çambaşı Pond through combined biochemical and molecular methods. Canonical correspondence analysis showed that the most important ecological factors for microorganisms to settle on frog skin were determined as water conductivity and dissolved oxygen amount. The most frequently isolated bacteria belonged to the genera Erwinia and Pseudomonas. Altitude positively affected Exiguobacterium. This first report of skin cultivable bacteria from P. ridibundus juvenile forms natural population improves our knowledge of amphibian skin bacterial flora. This study contributes to a better understanding of their ecology and how this species has survived in an environment modulated by altitude.

Characterization of the First Carbapenem-Resistant Pseudocitrobacter faecalis Harboring blaOXA-181 in China

With the wide use of carbapenems, carbapenem-resistant Enterobacterales have been increasingly reported worldwide. In this study, one bla_OXA-181-positive Pseudocitrobacter faecalis strain was isolated from the blood culture of a patient with a bloodstream infection in China, which was its first clinical report outside Pakistan. Species identification of P. faecalis was initially performed using MALDI-TOF/MS and further confirmed by 16S rRNA gene and housekeeping gene sequencing. The antimicrobial susceptibility testing was determined through the broth microdilution method, and their clonal relationship was analyzed by pulsed-field gel electrophoresis. To study the transmission and genetic structure of the bla_OXA-181 gene, a transformation test and whole-genome sequencing (WGS) were performed. The results of the antimicrobial susceptibility testing indicated this P. faecalis was resistant to carbapenems, quinolones, and commonly used β-lactam/β-lactamase inhibitor combinations. Through WGS and transformation experiments, bla_OXA-181 and qnrS1 genes causing antibiotic resistance were located on a 55,148-bp length IncX3 type plasmid with a truncated ColKp3 replicon gene. As a rare species of Enterobacterales, P. faecalis was clinically reported in China for the first time, and the bla_OXA-181 gene it carried was located on a globally disseminated IncX3 plasmid. The spread of such bacteria and antibiotic resistance requires more clinical attention.