No effect of parental quality or extrapair paternity on brood sex ratio in the blue tit (Parus caeruleus)

Sex allocation theory predicts that parents should manipulatebrood sex ratio in order to maximise the combined reproductivevalue of their progeny. Females mating with high quality malesshould, therefore, be expected to produce brood sex ratiosbiased towards sons, as male offspring would receive a relativelygreater advantage from inheritance of their father's characteristicsthan would their female siblings. Furthermore, it has been suggested that sex allocation in chicks fathered through extrapair fertilizations should also be biased towards sons. Contraryto these predictions, we found no evidence that the distributionof sex ratios in a sample of 1483 chicks from 154 broods ofblue tits (Parus caeruleus) deviated significantly from thatof a binomial distribution around an even sex ratio. In addition,we found no significant effect on brood sex ratio of the individualquality of either parent as indicated by their biometrics, feather mite loads, time of breeding, or parental survival. This suggeststhat females in our population were either unable to manipulateoffspring sex allocation or did not do so because selectionpressures were not strong enough to produce a significant shiftaway from random sex allocation. The paternity of 986 chicks from 103 broods was determined using DNA microsatellite typing.Extrapair males sired 115 chicks (11.7%) from 41 broods (39.8%).There was no significant effect of paternity (within-pair versusextrapair) on the sex of individual offspring. We suggest that,in addition to the weakness of selection pressures, the possiblemechanisms responsible for the allocation of sex may not besufficiently accurate to control offspring sex at the levelof the individual egg.     

Plasmids of Chlamydia psittaci: Cloning and comparison of isolates by Southern hybridisation

Abstract A chlamydial plasmid, 6.2 kb in size, was isolated from an avian strain of Chlamydia psittaci and cloned into the Eco RI site of pUC13. A restriction enzyme cleavage map of the resultant clone, pAP¹p, was very similar to the published map of the plasmid cloned from the C. psittaci meningopneumonitis strain Cal-10. Southern hybridisation analyses using pAP¹p as a probe, revealed the presence of plasmids with homologous DNA sequences in avian psittacosis, avian ornithosis, ovine polyarthritis and sporadic bovine encephalomyelitis strains of C. psittaci , as well as the LGV strain of Chlamydia trachomatis . Plasmid was not detected in koala conjunctivitis, ovine abortion or feline conjunctivitis isolates. The plasmid-containing isolates could be grouped according to size (6.2 or 7.2–7.3 kb) and restriction endonuclease pattern. These three plasmid categories correlate with previously reported C. psittaci biotypes, immunotypes and serotypes. The absence of plasmid from three infectious, pathogenic strains of C. psittaci suggests that, in this species at least, plasmid-encoded genes are not essential for survival, infectivity or virulence of the parasite.     

深圳市金黄色葡萄球菌耐药性分析及分子分型

目的了解深圳市金黄色葡萄球菌的耐药性特点及分子分型特征。方法收集2012年来自深圳市7所医院的428株金黄色葡萄球菌,以琼脂稀释法测定其对12种抗菌药物的最低抑菌浓度(MIC),采用聚合酶链式反应(PCR)检测杀白细胞毒素(PVL),并对携带PVL基因的菌株进行多位点基因序列分型(MLST)。结果428株金黄色葡萄球菌中耐甲氧西林金黄色葡萄球菌(MRSA)共116株(26.2%),甲氧西林敏感金黄色葡萄球菌(MSSA)共312株(73.8%)。在12种抗菌药物中,该菌对青霉素和红霉素的耐药率最高,分别为88.8%和44.2%;未发现替考拉宁、利奈唑胺和万古霉素的耐药株。MRSA对青霉素和环丙沙星的耐药率显著高于MSSA。428株金黄色葡萄球菌中,有60株(14.02%)携带PVL基因。MLST分型结果显示共有14种已知序列型和4种新的序列型,其中ST59和ST338最多,分别为16株和12株。结论深圳地区金黄色葡萄球菌MRSA检出率以及对多种抗菌药物的耐药率均低于全国平均水平,PVL基因阳性率处于中等水平;存在多种ST分型,以ST59和ST338多见,具有遗传多样性和独特的遗传背景。     

Application of the MALDI Biotyper to clinical microbiology: progress and potential

Introduction: The introduction of the MALDI Biotyper in laboratories substantially changed microbiology practice, this has been called a revolution. The system accelerated diagnostic while costs were reduced and accuracy was increased. In just a few years MALDI-TOF MS became the first-line identification tool for microorganisms. Ten years after its introduction, more than 2000 MALDI Biotyper systems are installed in laboratories which are performing routine diagnostic, and the number is still increasing.

Areas covered: This article summarises changes in clinical microbiology introduced by the MALDI Biotyper and its effects, as it has been published in peer reviewed articles found in PubMed. Further, the potential of novel developments to increase the value of the system is described.

Expert commentary: The MALDI Biotyper has significantly improved clinical microbiology in the area of microorganism identification. Now new developments and applications, e.g. for typing and resistance testing, might further increase its value in clinical microbiology. The systems might get the central diagnostic analyser which is getting integrated into the widely automated microbiology laboratories of the future.     

Contrasting patterns of molecular diversity and Wolbachia infection in bisexual and parthenogenetic Strophosoma weevils (Coleoptera: Curculionidae)

It has been postulated that parthenogenesis in weevil species is of hybrid origin, but some have speculated that Wolbachia infection plays a role through the modification of host breeding systems. Here we focus on Strophosoma weevils, which are known to be pests in young forest stands. Using molecular data, we investigated the diversity of the two most common Strophosoma species in Europe: S. capitatum, which reproduces bisexually, and S. melanogrammum, which is parthenogenetic. Also researched were their associations with the endosymbiotic bacterium Wolbachia. These species of weevil were found to be clearly distinguishable based on their mitochondrial DNA, with the bisexual taxa being more diverse. However, the nuclear DNA divergence of the two species was very low, and the parthenogenetic taxon was found to be heterozygous. Wolbachia infection was detected in all individuals of the S. melanogrammum populations and less than half of the S. capitatum populations. Moreover, multiple Wolbachia strains were found in both taxa (two in the former and three in the latter). The results of this research suggest that parthenogenesis in this genus is of hybrid origin and that Wolbachia could have played a role in speciation of these weevils.     

用全基因组测序评价VNTR分型在泛耐药结核分枝杆菌传播中的应用

近年来,随着技术的进步、测序成本的降低,全基因组测序(whole-genome sequencing,WGS)技术开始应用于结核分枝杆菌传播的研究。本研究采用基于单核苷酸多态性(single nucleotide polymorphism,SNP)的分型方法评价多位点数目可变串联重复序列(variable-number tandem-repeat,VNTR)分型判断泛耐药结核分枝杆菌(extensively drug-resistant Mycobacterium tuberculosis,XDR-TB)传播及成簇特征的准确性。对2003-2009年重庆市肺科医院诊断的55例XDR-TB菌株分别进行9＋3个位点的VNTR分型和WGS分析,分别构建系统进化树,并比较两种方法判断成簇的一致性与差异。VNTR分型方法鉴定出45个基因型,其中39株为单一基因型,16株(29.1%)分别归入6个基因簇。规定菌株间差异不超过12个SNP即为成簇,WGS将20株(36.4%)分为5个簇。两种方法判断成簇的一致性为 63.6%。与WGS相比,VNTR分型的灵敏度为 40.0%,特异度为 77.1%。相比于WGS,VNTR分型特异度较高,但仅凭其结果可能会错误估计XDR-TB的传播性。因此,规定菌株间相差不超过12个SNP即有近期传播关系是否适用于XDR-TB,有待进一步研究。     

Complete genome sequencing of sixteen Francisella noatunensis subsp. orientalis isolates: A genomic approach for molecular characterization and spread dynamics of this clonal population

Francisella noatunensis subsp. orientalis (FNO) is an important emerging pathogen associated with disease outbreaks in farm-raised Nile tilapia. FNO genetic diversity using PCR-based typing, no intra-species discrimination was achieved among isolates/strains from different countries, thus demonstrating a clonal behaviour pattern. In this study, we aimed to evaluate the population structure of FNO isolates by comparing whole-genome sequencing data. The analysis of recombination showed that Brazilian isolates group formed a clonal population; whereas other lineages are also supported by this analysis for isolates from foreign countries. The whole-genome multilocus sequence typing (wgMLST) analysis showed varying numbers of dissimilar alleles, suggesting that the Brazilian clonal population are in expansion. Each Brazilian isolate could be identified as a single node by high-resolution gene-by-gene approach, presenting slight genetic differences associated to mutational events. The common ancestry node suggests a single entry into the country before 2012, and the rapid dissemination of this infectious agent may be linked to market sales of infected fingerlings.     

Polymerase Chain Reaction Test for Differentiation of Five Toxin Types of Clostridium perfringens

In order to avoid the use of experimental animals, the polymerase chain reaction (PCR) method was applied to differentiate Clostridium perfringens into five toxin types. Twenty-two out of 23 strains tested produced the toxin(s) corresponding to the toxin gene(s) identified by PCR, and vice versa. Consequently, the gene typing was consistent with conventional typing by animal tests. Twenty-five strains were identified as types different from original ones by the PCR method as well as a toxin neutralization test. These findings suggest that the PCR method, which is easy and timesaving, is applicable to identify the toxin types of C. perfringens as an alternative to animal tests, and that beta-, epsilon- and iota-toxin genes might be lost by long-term preservation. The reasons why the strains lost the genes are discussed.