Cytogenetic analysis of three sea catfish species (Teleostei, Siluriformes, Ariidae) with the first report of Ag-NOR in this fish family

Despite their ecological and economical importance, fishes of the family Ariidae are still genetically and cytogenetically poorly studied. Among the 133 known species of ariids, only eight have been karyotyped. Cytogenetic analyses performed on Genidens barbus and Sciades herzbergii revealed that both species have 2n = 56 chromosomes and Cathorops aff. mapale has 2n = 52 chromosomes: Genidens barbus has 10 Metacentrics (M), 14 Submetacentrics (SM), 26 Subtelocentrics (ST), and 6 Acrocentrics (A), Sciades herzbergii has 14M, 20SM, 18ST and 4A, whereas Cathorops aff. mapale has 14M, 20SM, and 18ST. The nucleolus organizer regions (NORs) were found in a single chromosome pair on the short arm of a large-sized ST pair in Genidens barbus and on the short arm of a middle-size SM pair in Cathorops aff. mapale. Multiple NORs on the short arms of two large-sized ST pairs were found in Sciades herzbergii. The occurrence of diploid numbers ranging from 2n = 52 through 56 chromosomes and the presence of different karyotypic compositions, besides the number and position of NORs suggest that several numeric and structural chromosome rearrangements were fixed during the evolutionary history of this fish family.     

A New Model for the Origin of Bipedality

Scholars have long thought that bipedality evolved gradually in response to the opening of the savanna. Recently, both parts of this concept have come into question. A variety of benefits of bipedality have been posited as responsible, but a trait can not evolve unless a useful mutation appears. Perhaps we need to stop wondering about selective pressures and consider what kind of mutation might be involved in forming a bipedal pelvis. Work on the evolution of development has shown that there are segmental control genes, alterations in which have large effects. These include the hox genes, of which there are four sets in humans, referred to as the HOX A, B, C, and D sequences. Changes in their activation in embryogenesis alter the identity of vertebrae and limb structure. An alteration in the control region of certain of the distal HOX D genes may well be responsible for the sudden appearance of bipedality by moving the boundary between the lumbar and sacral vertebrae, and so moving the position of the pelvis and lower limb origin. Pongids usually have three lumbar vertebrae; early hominids, 6. Pongids also have 48 chromosomes while we have 46. HOX D is located on our 2nd chromosome, the one that is a fusion of two pongid chromosomes. If that fusion altered the onset of perhaps HOX D 10, so that it switched on a couple of segments later, then the sacrum would form further down the vertebral column and might be shorter. In this paper I look at the chromosomal location of HOX D and examine the likelihood that the fusion of two panid chromosomes could have given rise to alterations in its control resulting in the abrupt appearance of bipedality and accompanying changes in the limbs and in the chela in which the HOX sequences are reused.     

Application of variable number of tandem repeat analysis to track Salmonella enterica ssp. enterica serovar Typhimurium infection of pigs reared on three British farms through the production cycle to the abattoir

Aims: This study investigated the diversity and persistence of Salmonella strains through the pork finishing cycle, from the farm into the abattoir. Methods and Results: Isolates from four batches of finishers, from farm to abattoir, were used. Salmonella Typhimurium isolates were subjected to molecular typing using pulsed‐field gel electrophoresis and variable number of tandem repeat analysis. The results demonstrated that infection was transferred from the farm to the abattoir. Within the abattoir, infection from individual pigs contaminated the exterior of the carcass and pigs exposed to Salmonella in the lairage were infected. Conclusions: Salmonella can be introduced at various points in the pig production and slaughter process. Carcass contamination may arise from infection on farm and exposure in the lairage and abattoir environment. Pigs could be contaminated by previous batches of pigs while in lairage or during the dressing process. Salmonella infection on farms is dynamic with multiple serovars present from different sources. Significance and Impact of the Study: Molecular typing methods facilitated the tracing of Salm. Typhimurium through the production cycle and differentiated some farm‐acquired from abattoir‐acquired strains. The findings emphasize the importance of integrated control strategies along the pork food chain.     

Variability in occurrence of multiple prophage genes in Salmonella Typhimurium strains isolated in Slovak Republic

Lysogenic bacteriophages are a significant source of variability in closely related Salmonella strains. In this study, screening for diversity of 152 Salmonella Typhimurium strains was performed using PCR detection of selected prophage regions derived from phages P22, Gifsy-1, Gifsy-2, Fels-1, ST104 and SopEPhi. A high degree of variability was observed in the presence of specific genes. Based on the presence of particular prophage genes, we divided strains into 37 different PCR-prophage profiles; 20 of them were represented by only a single strain. Using multilocus variable number tandem repeats analysis (MLVA), 152 Salmonella strains were separated into 82 MLVA strings. Similar grouping of Salmonella strains was observed in the case of PCR-prophage detection and MLVA and the results corresponded well with the phage type of strains. However, several Salmonella strains were detected, which were closely related according to MLVA; yet, they differed in PCR phage profiles. The observations support a view that integration/excision of bacteriophages in Salmonella strains are frequent events shaping the bacterial genome.     

Oral immunization with attenuated Salmonella vaccine expressing Escherichia coli O157:H7 intimin gamma triggers both systemic and mucosal humoral immunity in mice

Human infections with EHEC such as O157:H7 have been a great concern for worldwide food-industry surveillance. This pathogen is commonly associated with bloody diarrhea that can evolve to the life-threatening hemolytic uremic syndrome. Animals are the natural reservoir where this pathogen remains asymptomatically, in steps of ingestion and colonization of the bowel. The bacterium is shed in the feces, contaminating the surroundings, including water and food that are directed for human consumption. A major player in this colonization process is intimin, an outer membrane adhesion molecule encoded by the E. coli attachment and effacement (eae) gene that has been shown to be essential for intimate bacterial attachment to eukaryotic host cells. In an attempt to reduce the colonization of animal reservoirs with EHEC O157:H7, we designed a vaccine model to induce an immune response against intimin gamma. The model is based on its recombinant expression in attenuated Salmonella, used as a suitable vaccine vector because of its recognized ability to deliver recombinant antigens and to elicit all forms of immunity: mucosal, systemic, and humoral responses. To test this model, mice were orally immunized with a S. enterica serovar Typhimurium strain carrying the pYA3137eaeA vector, and challenged with E. coli O157:H7. Here we show that immunization induced the production of high levels of specific IgG and IgA antibodies and promoted reduction in the fecal shedding of EHEC after challenge. The live recombinant vaccine reported herein may contribute to the efforts of reducing animal intestinal mucosa colonization.     

鼠伤寒沙门菌7个未知功能岛在致病性中的作用

【目的】探索沙门菌在进化过程中通过水平转移获得的未知功能岛在其致病过程中的作用,发现新的与致病性相关的岛。【方法】以鼠伤寒沙门菌ATCC 14028为亲本株,利用λRed重组酶系统分别构建了7个未知功能岛(STM14_0667-0673、2682-2687、2885-2891、3721-3728、4247-4253、4823-4828、5331-5341)的突变株,通过细胞侵袭实验、巨噬细胞内复制力检测及小鼠实验比较了野生型和突变株的毒力差异。【结果】Δ2682-2687和Δ5331-5341对上皮细胞的侵袭力显著低于野生型(P0.01);Δ2682-2687、Δ2885-2891和Δ5331-5341在巨噬细胞内的复制力、对小鼠的致死率以及在小鼠肠道和肝、脾的定殖能力均显著低于野生型(P0.05);其余4个突变株(Δ0667-0673、Δ3721-3728、Δ4247-4253、Δ4823-4828)的侵袭力、胞内复制力以及对小鼠的致病力与野生型相比无显著差异。【结论】发现3个未知功能岛显著影响鼠伤寒沙门菌的致病力,为深入研究这些岛的功能及调控机制奠定了基础。     

Serotyping, PCR, phage-typing and antibiotic sensitivity testing of Salmonella serovars isolated from urban drinking water supply systems of Nepal

AIMS: To study the occurrence and diversity of Salmonella serovars in urban water supply systems of Nepal. METHODS AND RESULTS: Occurrence of Salmonella was detected in 42 out of 300 water samples by enrichment culture technique in selenite F broth followed by plating on Salmonella Shigella agar. A total of 54 isolates identified to genus level by standard tests were subsequently confirmed by serotyping, phage typing and PCR detection of virulence genes (inv A and spv C). The predominant serotype was Salmonella Typhimurium, followed by Salm. Typhi, Salm. Paratyphi A and Salmonella Enteritidis. Most of the Salm. Typhi isolates were E1 phage type followed by UVS4, A and UVS1. All isolates of Salm. Paratyphi A and Salm. Enteritidis were an untypable (UT) phage type. The majority of isolates were multi-drug resistant as revealed by Kirby-Bauer disc diffusion technique. Ceftriaxone resistant isolates of Salm. Enteritidis indicated the presence of one of the ESBL genes, blaSHV, whereas the genes blaTEM and blaCTX were absent. CONCLUSIONS: The microbiological quality of the urban water supply is poor and indicates possibility of fatal outbreaks of enteric fever and related infections in Nepal. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study will be useful in water borne disease control and prevention strategy formulation in Nepal and in the global context.     

Comparative susceptibility of planktonic and 3‐day‐old Salmonella Typhimurium biofilms to disinfectants

Aims: To compare the susceptibility of a 3‐day‐old biofilm and planktonic Salmonella to disinfectants at different exposure times. We hypothesize that Salmonella biofilms are more resilient to disinfectants compared to planktonic Salmonella. Methods and Results: The susceptibility of planktonic cells to disinfectants was tested by a modified version of the Council of Europe suspension test EN 1276. Salmonella biofilms were formed using the Calgary Biofilm Device. Results show that 3‐day‐old Salmonella biofilms are less susceptible to the disinfectants benzalkonium chloride, chlorhexidine gluconate, citric acid, quaternary ammonium compounds, sodium hypochlorite (SH) and ethanol, compared to planktonic Salmonella. Surprisingly, the results also demonstrate that low concentrations of SH were more effective against a 3‐day‐old biofilm compared to high concentrations of SH. Conclusions: While all the disinfectants evaluated were able to reduce biofilm‐associated cells at concentrations and contact times sufficient to eliminate planktonic cells, there were still sufficient viable cells remaining in the biofilm to cause further contamination and potential infection. Significance and Impact of the Study: Protocols for the use of chemical disinfectants need to include biofilm susceptibility testing. There is a requirement for an effective and standardized tool for determining the susceptibility of biofilms to disinfectants.