Intra- and interspecies variations in pupation height in Drosophila.

In order to study the pupation site preference which is an important component of larval behaviour, pupation height was scored in Drosophila ananassae, D. bipectinata and D. malerkotliana by using a large number of strains of these species. The mean pupation height of different strains ranged from 1.1 to 8.7 mm in D. ananassae, from 0.41 to 0.75 mm in D. bipectinata and from 1.0 to 1.3 mm in D. malerkotliana. The analysis of variance and t-test were performed to test intre- and interspecies variations in pupation height. These tests revealed significant variation among three species. Significant variations among different strains of the same species were also found in D. ananassae and D. bipectinata. These observations provide evidence for intra- and interspecies variations in pupation height in Drosophila. Variations among different strains of the same species in pupation height are attributable to genetic heterogeneity among the strains.     

Comparison of drug resistance genotypes between Beijing and non-Beijing family strains of Mycobacterium tuberculosis in Korea

The frequency of resistance genotypes among Beijing and non-Beijing strains was compared using a reverse blot hybridization assay to detect mutations within genes associated with rifampicin (rpoB) and isoniazid (katG, inhA, and ahpC) resistance. Of the 743 Mycobacterium tuberculosis isolates, 569 (77%) belonged to Beijing family. The proportion of Beijing strains was significantly higher among MDR-TB isolates than among drug-susceptible strains (82% vs. 72%, p<0.01). Genotype analysis of the rpoB gene revealed significantly lower rates of the Ser531Leu mutation rate among Beijing vs. non-Beijing MDR-TB strains (41% vs. 66%, p<0.005). While the mutation for Ser315Thr in the katG gene was more common among Beijing vs. non-Beijing family strains (65% vs. 50%, p<0.01), the mutation rate of promoter region of the inhA gene was lower among Beijing strains compared with non-Beijing strains (14% vs. 25%, p<0.05). Reverse hybridization successfully detected over 80% of isoniazid-resistant strains and over 92% of rifampicin-resistant strains among Korean isolates. Significant differences in mutation rates in the rpoB, katG, and inhA genes between Beijing strains and non-Beijing strains could explain discrepancies in mutation rates of genotypes in different countries. Reverse hybridization was useful for rapid detection of isoniazid and rifampicin resistant strains.     

Investigation of seven Vibrio virulence genes among Vibrio alginolyticus and Vibrio parahaemolyticus strains from the coastal mariculture systems in Guangdong, China

AIMS: To investigate the distribution of the virulence of two Vibrio species among different strains obtained from the mariculture systems on the coast of Guangdong in China and the correlation between the virulence strains and the virulence genes among Vibrio alginolyticus. METHODS: Besides three strains, 72 V. alginolyticus strains and seven Vibrio parahaemolyticus strains were examined by PCR or semi-nested PCR for the virulence genes (tlh, trh, tdh, toxR, toxRS, ctxA, VPI). Additionally, the virulence of 18 V. alginolyticus strains was tested. SIGNIFICANCE AND IMPACT OF THE STUDY: Virulence genes homologous to those in the V. parahaemolyticus and Vibrio cholerae are widely distributed among V. alginolyticus and V. parahaemolyticus in the coastal mariculture systems in Guangdong, China. Some of the V. alginolyticus strains are pathogenic to aquatic animals, and might have derived their virulence genes from V. parahaemolyticus or V. cholerae, representing a possible reservoir of these genes. However, there is no correlation between presence and absence of the virulence genes used to investigate V. alginolyticus and its virulent strains. In this report, we also show that tlh is distributed among V. alginolyticus.     

Hypoxanthine-guanine phosphoribosyl transferase in brains of mice. Regional distribution in seven inbred mouse strains

Causal relationships have been suggested between aspects of human behavior and hyperuricemia associated with low tissue activities of the x-linked enzyme hypoxanthine-guanine phosphoribosyl transferase. Brain is reported to have the highest content of HGPRT activity among body organs. Many studies have indicated that genetically distinct strains of mice exhibit strain-specific behavioral phenotypes. The present measurements of HGPRT were made to determine if genetically associated differences in regional distribution of brain HGPRT exist between several inbred mouse strains and if they were of sufficient magnitude to warrant a search for correlations with measures of behavior. Significant differences were found in overall brain content of HGPRT activity among seven inbred mouse strains, as well as in regional distribution of enzyme activity among eight structures of brains of each of the individual strains.     

Stx genotypes and antimicrobial resistance profiles of Shiga toxin-producing Escherichia coli strains isolated from human infections, cattle and foods in Brazil

A total of 107 Shiga toxin-producing Escherichia coli strains (STEC) isolated from different origins in S?o Paulo, Brazil, and belonging to different serotypes were characterized regarding stx subtypes and susceptibility to antimicrobial agents. Most of the human STEC strains harbored stx1 (85.7%), while stx2, associated or not to stx1, was identified preferentially in the animal and food strains. None of the STEC strains carried stx1c. Some genotypes occurred exclusively among strains of bovine origin as stx2c, stx1+2+2c (16.5% each), and stx2d (0.9%), whereas stx2+2c2vha) was only identified among the O157:H7 human strains. Moreover, the stx(2c2vhb) subtype was found more frequently among bovine than human strains (39% vs. 4.8%). The highest frequencies of susceptibility to antimicrobial agents were observed among bovine (87%) and food (100%) STEC strains, while 47.6% of the human isolates were resistant to at least one drug. Multiresistance occurred among O111 STEC strains from human and bovine origin. The antimicrobials to which resistance was most frequently observed were tetracycline (90%) and streptomycin (75%) among human strains, and also sulphazotrin (88%) in animal strains. A few serotypes were commonly identified among STEC strains isolated from diverse sources in Brazil, but in general the strains presented distinct stx subtypes and/or antimicrobial resistance profiles.     

Characteristics of Neisseria meningitidis strains isolated from patients with symptoms of meningococcal meningitis in Poland in 1995-2000

Phenotype and genotype identification of 179 Neisseria meningitidis strains isolated from cerebrospinal fluid or blood of patients with meningococcal infection, hospitalized in Poland, was performed. This is the first analysis of that type conducted in Poland. We analyzed strains collected in 1995-2000 from laboratories located all over the country. Phenotype Neisseria meningitidis B:22:P1.14 was the predominant among analyzed invasive strains in Poland. Type 22 is characteristic to most of the strains isolated in our country. No strain from analyzed group belonged to known epidemic clusters. One penicillin resistant strain (MIC = 2 mg/l) and about 27% strains with decreased susceptibility to penicillin (0.1 = < MIC < 1.0 mg/l) were present among 166 N. meningitidis tested. All strains were susceptible to ciprofloxacin and rifampicin.     

Associations of allozyme variation and behavior in the cowpea weevil (Callosobruchus maculatus)

The cowpea weevil (Callosobruchus maculatus (Fabré)) exhibits several behavioral traits that are stable within, but vary among, strains. These traits are heritable and quantitative. We used cellulose acetate gel electrophoresis to quantify allozyme variation within and among laboratory cultures of four weevil strains and determine whether allozyme variation correlates with behavioral traits. Significant variation exists at 8 of 11 loci assayed and gene frequencies are significantly different among strains. The South Indian strain (SI) is most variable and measures of genetic distance set it apart from the other strains. It is also behaviorally unique. The Brazilian strain (BC) is most different from SI in allozyme diversity and behavioral phenotype, while two African strains (IITA, CAM) are intermediate in allozyme diversity and phenotype. These results are consistent with the known history of these strains and the differences in the allozymes parallel the differences in behavioral traits.     

Emergence of uropathogenic extended-spectrum beta lactamases-producing Escherichia coli strains in the community

The aim of this study was to determine the virulence characteristics and resistance pattern of the extended-spectrum/lactamases (ESBLs)-producing Escherichia coli strains isolated from urine of outpatients in the Zagreb region during a five-month period, and to compare them with the non ESBLs-producing E. coli strains isolated in the same period. Out of 2451 E. coli strains isolated from urine of nonhospitalized patients with significant bacteriuria, a total of 39 ESBLs-producing strains (1.59%) were detected by a double-disk diffusion technique and by the broth-dilution minimal inhibitory concentration reduction method. The 45 non ESBLs-producing strains were randomly chosen, and phenotype of the two groups of strains was characterized and compared. Serogroup O4, hemolysin production, expression of P- and type 1 fimbriae as well as resistance to gentamicin and amikacin were significantly more prevalent characteristics among the ESBLs-producing strains than among non ESBLs-producing strains (p < 0.01), while higher prevalence of trimethoprim-sulfamethoxazole resistance among ESBLs-producing strains was not statistically significant (p > 0.05). Chromosomal DNA analysis by pulsed-field gel electrophoresis exhibited a great genomic similarity among ESBLs-producing strains and revealed that those highly virulent and resistant E. coli strains isolated from urine of outpatients in the Zagreb region had a clonal propagation.     

Variations in virulence between different electrophoretic types of Listeria monocytogenes

A total of 245 strains of Listeria monocytogenes, representing 33 different electrophoretic types (ETs), were examined quantitatively for haemolytic activity. No significant difference was observed in the mean haemolytic activity between different ETs. Eighty four out of 91 strains examined were found to be virulent for chick embryos. Strains belonging to ET 2 and ET 4 were found to be less virulent than strains of other ETs (P = 0.0447). Furthermore, strains from clinical cases were found to be more virulent (P = 0.0002) than strains from foods (the MTD among clinical strains was 2.46 in mean compared with 3.64 among food isolates). The explanation for this may be that more virulent strains are more prone to cause human infection. It is, however, also possible that strains of L. monocytogenes may become more virulent while multiplying in a living organism compared with multiplying in foods.     

Genetic Divergence in Mandible Form in Relation to Molecular Divergence in Inbred Mouse Strains

Genetic divergence in the form of the mandible is examined in ten inbred strains of mice. Several univariate and multivariate genetic distance estimates are given for the morphological data and these estimates are compared to measures of genealogical and molecular divergence. Highly significant divergence occurs among the ten strains in all 11 mandible traits considered individually and simultaneously. Genealogical relationship among strains is highly correlated with genetic divergence in single locus molecular traits. However, the concordance between genealogical relationship and multivariate genetic divergence in morphology is much more complex. Whether there is a significant correlation between morphological divergence and genealogy depends upon the method of analysis and the particular genetic distance statistic being employed.     

Application of multilocus enzyme electrophoresis in studies of the epidemiology of Listeria monocytogenes in Denmark.

A total of 245 strains of Listeria monocytogenes were investigated. These strains were isolated from human and animal cases of listeriosis as well as from different kinds of raw and processed foods. Thirty-three electrophoretic types (ETs) were identified among the 245 strains. The strains investigated included all human clinical strains isolated in Denmark during 1989 and 1990. Seventy-three percent of the strains isolated in this period were assigned to one of only two ETs (ET 1 and ET 4). ET 1, which was found to be the most frequently occurring ET among strains isolated from human clinical cases, was also found to occur rather frequently in animal clinical cases. ET 1 was, however, found only sporadically among strains isolated from foods and food factories. The data indicate that there might be something distinctive about the physiology or ecology of the ET 1 clone which makes it more likely to bring about disease in human beings either because of high pathogenicity or because of a special ability to multiply to infectious doses in processed foods. Another type, designated ET 4, was found to be the next most frequently occurring ET, after ET 1, among human clinical isolates. This could be explained by the fact that ET 4 was found to be the most frequently occurring ET within food isolates.     

Antagonism among Gluconacetobacter diazotrophicus strains in culture media and in endophytic association

In this study the antagonistic activity among 55 Gluconacetobacter diazotrophicus strains, belonging to 13 electrophoretic types (ETs), in culture media was analyzed. Antagonistic effects were seen only in strains belonging to two ETs named ET-1 and ET-3. Two out of 29 ET-1 strains, and 3 out of 7 ET-3 strains of G. diazotrophicus showed antagonistic effects against many other strains belonging to all the ETs of this species analyzed, and against closely related strains of Gluconacetobacter species, including Gluconacetobacter johannae, Gluconacetobacter azotocaptans and Gluconacetobacter liquefaciens but not against other phylogenetically distant bacterial species. Results showed that the substance responsible of such antagonistic activity is a low molecular mass molecule (approximately 3400 Da), stable from pH 3.5 to 8.5, and very stable at 4 degrees C for 10 months. This substance was sensitive to proteases, and the antagonistic activity was lost after 2 h at 95 degrees C. All of these features show that the substance is related to bacteriocin-like molecules. The antagonistic substance should be chromosomally encoded because ET-3 strains of G. diazotrophicus do not harbor any plasmids. The antagonistic ability of ET-3 strains of G. diazotrophicus could be an advantage for the natural colonization of the sugarcane environment, as was observed in experiments with micropropagated sterile sugarcane plantlets co-inoculated with a bacteriocin-producer strain and a bacteriocin-sensitive strain of G. diazotrophicus. In these experiments, both in the rhizosphere as well as inside the roots, the bacteriocin-sensitive population decreased drastically. In addition, this study shows that inside the plants there may exist antagonistic interactions among endophytic bacteria like to those described among the rhizospheric community.     

Genetic and Phenotypic Diversity of Bacillus polymyxa in Soil and in the Wheat Rhizosphere

Diversity among 130 strains of Bacillus polymyxa was studied; the bacteria were isolated by immunotrapping from nonrhizosphere soil (32 strains), rhizosphere soil (38 strains), and the rhizoplane (60 strains) of wheat plantlets growing in a growth chamber. The strains were characterized phenotypically by 63 auxanographic (API 50 CHB and API 20B strips) and morphological features, serologically by an enzyme-linked immunosorbent assay, and genetically by restriction fragment length polymorphism (RFLP) profiles of total DNA in combination with hybridization patterns obtained with an rRNA gene probe. Cluster analysis of phenotypic characters by the unweighted pair group method with averages indicated four groups at a similarity level of 93%. Clustering of B. polymyxa strains from the various fractions showed that the strains isolated from nonrhizosphere soil fell into two groups (I and II), while the third group (III) mainly comprised strains isolated from rhizosphere soil. The last group (IV) included strains isolated exclusively from the rhizoplane. Strains belonging to a particular group exhibited a similarity level of 96%. Serological properties revealed a higher variability among strains isolated from nonrhizosphere and rhizosphere soil than among rhizoplane strains. RFLP patterns also revealed a greater genetic diversity among strains isolated from nonrhizosphere and rhizosphere soil and therefore could not be clearly grouped. The RFLP patterns of sorbitol-positive strains isolated from the rhizoplane were identical. These results indicate that diversity within populations of B. polymyxa isolated from nonrhizosphere and rhizosphere soil is higher than that of B. polymyxa isolated from the rhizoplane. It therefore appears that wheat roots may select a specific subpopulation from the soil B. polymyxa population.     

中国柯萨奇病毒A组16型部分VP1区序列测定及系统进化分析

利用1999～2004年连续6年从中国深圳及北京地区分离的柯萨奇病毒A组16型(Coxsackievirus A16,Cox．A16)毒株的部分VP1区基因序列进行分析和研究,试图找出中国Cox．A16的种系进化规律和分型依据。6株Cox．A16病毒部分VP1区核苷酸和氨基酸同源性均较高,相互间核苷酸同源性为94．5％～98．0％,氨基酸同源性为97．8％～100％。6株中国分离株与Cox．A16国际参考株相比,部分VP1区核苷酸同源性高于78．2％,氨基酸同源性高于为93．3％。基因系统进化分析表明,中国大陆分离的6株Cox．A16与中国台湾流行株Tainan-5079-98(AF177911),与4株日本分离株、瑞典株及美国株GA95—2095(AF081613)、PA94—5753(AF081628)的关系均较近,核苷酸同源性大于93．3％。了解我国Cox．A16流行株的遗传学背景和种系进化关系,对有效地预防和控制Cox．A16流行有重要意义。     

Comparison of pulsed-field gel electrophoresis patterns of antimicrobial-resistant Escherichia coli and enterococci isolates from the feces of livestock and livestock farmers in Japan

Seven hundred thirty-nine animal strains and 662 livestock-farmer strains, consisting of Escherichia coli and enterococci, were examined for their pulsed-field gel electrophoresis (PFGE) and antimicrobial-resistance patterns. Two hundred fifty-eight and 203 PFGE patterns were found among 739 animal strains isolated from animals comprising broilers, pigs and cattle, and 662 human strains isolated from livestock farmers, respectively, from 27 farms in Japan. These results demonstrated that the PFGE patterns found among E. coli and enterococci strains from animals and livestock-farmers were heterogeneous and considerably diverse. The strains having both the identical PFGE pattern and the same drug-resistance pattern were defined as a single clone in this study. Seven types of E. coli and enterococci clones were shared among animals within the same farms and between the different farms housing the same animal species. The 25 strains (3.4%) of 739 E. coli and enterococci animal strains belonged to these seven types of clones. Only three types of E. coli clones were shared among animals between the different farms housing different animal species, but no identical E. faecalis or E. faecium clones were found between different animal species farms. The 15 strains (2.0%) of 739 E. coli and enterococci animal strains belonged to these three types of clones. Additionally, the 11 strains (1.5%) of 739 E. coli and enterococci strains isolated from animals were identical clones to strains isolated from livestock farmers of the same farm. These results suggest that the transmission of animal clones to livestock farmers or vice versa is less common.     

Nucleotide variation in wild and inbred mice

The house mouse is a well-established model organism, particularly for studying the genetics of complex traits. However, most studies of mice use classical inbred strains, whose genomes derive from multiple species. Relatively little is known about the distribution of genetic variation among these species or how variation among strains relates to variation in the wild. We sequenced intronic regions of five X-linked loci in large samples of wild Mus domesticus and M. musculus, and we found low levels of nucleotide diversity in both species. We compared these data to published data from short portions of six X-linked and 18 autosomal loci in wild mice. We estimate that M. domesticus and M. musculus diverged <500,000 years ago. Consistent with this recent divergence, some gene genealogies were reciprocally monophyletic between these species, while others were paraphyletic or polyphyletic. In general, the X chromosome was more differentiated than the autosomes. We resequenced classical inbred strains for all 29 loci and found that inbred strains contain only a small amount of the genetic variation seen in wild mice. Notably, the X chromosome contains proportionately less variation among inbred strains than do the autosomes. Moreover, variation among inbred strains derives from differences between species as well as from differences within species, and these proportions differ in different genomic regions. Wild mice thus provide a reservoir of additional genetic variation that may be useful for mapping studies. Together these results suggest that wild mice will be a valuable complement to laboratory strains for studying the genetics of complex traits.     

Levels of variation in stress resistance in drosophila among strains, local populations, and geographic regions: patterns for desiccation, starvation, cold resistance, and associated traits

Stress resistance traits in Drosophila often show clinal variation. Although these patterns suggest selection, there is generally no attempt to test how large differences at the geographical level are relative to levels of variation within and between local populations. Here we compare these levels in D. melanogaster from temperate Tasmania versus tropical northern Queensland by focusing on adult resistance to desiccation, cold and starvation stress, as well as associated traits (size, lipid content). For starvation and desiccation resistance, levels of variation were highest among strains from the same population. whereas there was little differentiation among local populations and a low level of differentiation at the geographic level. For adult cold resistance, there was local differentiation and strain variation but no geographic variation. For size (thorax length), geographic differentiation was higher despite some overlap among strains from the tropical and temperate locations. Finally, for lipid levels there was only evidence for variation among strains. The low level of differentiation among geographic locations for stress resistance was further verified with the characterization of isofemale strains from 18 locations along a coastal transect extending from Tasmania to northern Queensland. Crosses among some of the isofemale strains showed that results were not confounded by inbreeding effects. Strains derived from a cross between a tropical and temperate strain differed for all traits, and variation among strains for body size was higher than strain variation within the geographic regions. Unlike in previous studies, lipid content and starvation resistance were not correlated in any set of strains, but there was a correlation between cold resistance and lipid content. There was also a correlation between desiccation resistance and size but only in the geographic cross strains. These findings suggest a large amount of variation in stress resistance at the population level and inconsistent correlation patterns across experimental approaches.     

随机扩增多态性DNA技术在鲍氏层孔菌菌株鉴别中的应用

用20个随机引物对7个不同来源的鲍氏层孔菌菌株进行了RAPD分析．结果表明120个随机引物中,有17个引物的扩增产物DNA条带表现出明显的多态性,不同引物对供试菌株扩增出现的DNA条带数目少则10条,多达33条．DNA片段从250bp到2000bp;采用17个引物对7个鲍氏层孔菌菌株共扩增出DNA片段带377条,不同引物扩增出的DNA片段谱带存在较大差异．采用UPGMA系统聚类法,将7个菌株聚类为两大类,能直观准确地揭示菌株间的差异并加以鉴别．     

Assessment of changes in the epidemiology of Clostridium difficile isolated from diarrheal patients in Hungary

150 Clostridium difficile strains isolated from diarrheal feces were collected from three parts of Hungary and the presence of genes responsible for toxin A and B, and binary toxin production were examined. MIC distribution against clindamycin, erythromycin, metronidazole, moxifloxacin and rifampin of 80 toxigenic strains selected from the above-mentioned strains and 20 large clostridial toxins (LCTs)-positive strains chosen from our earlier strain collection were determined. 80% of the examined 150 strains were positive for both tcdA and tcdB, and no toxin A-negative, toxin B-positive isolates were found during the study period. 5.3% of toxigenic strains proved to be positive for binary toxin too. Among binary toxin-positive strains, one strain showed the same pattern characteristic of PCR ribotype 027. Comparison of recent findings and our earlier results, the prevalence of toxin-producing and binary toxin-positive strains among C. difficile isolated from diarrheal specimens increased. No metronidazole resistant isolate was detected among strains isolated in 2002–2003 and 2006–2007. The rates of resistance to erythromycin, clindamycin, moxifloxacin and rifampin among strains isolated between 2006 and 2007 were 25%, 27.5%, 25% and 6.3%, respectively. Erythromycin resistance was frequently associated with clindamycin and moxifloxacin resistance, however this resistant phenotype was not found among strains isolated in 2002–2003.     

Clostridium difficile in emergency room

Clostridium difficile strains are known as etiological agents of pseudomembranous colitis (PMC), antibiotic-associated diarrhea (AAC) and colitis (AAC) and hospital-acquired infections. The aim of this study was to determine the frequency of C. difficile infection among patients in the emergency room and to compare isolated strains by phenotypic and genotypic characteristics. During a period of 11 months, 56 stool samples taken from diarrheic patients hospitalized in the emergency room of the Medical Center UC Davis and 14 environmental samples were cultured for isolation of C. difficile strains. Eighteen C. difficile strains were isolated from stool samples cultured on selective TCCCA plates and 5 strains from environmental samples using Rodac plates. Eleven toxigenic (TcdA+/TcdB+), 6 non-toxigenic (TcdA-/TcdB-) and unique toxin A-negative/toxin B-positive (TcdA-/TcdB+) C. difficile strains were detected among patients' isolates and 3 toxigenic and 2 non-toxigenic strains-among environmental samples. The majority of C. difficile-positive patients were treated previously by antibiotics. Four strains isolated from patients' fecal samples and one strain isolated from the environment demonstrated high-level resistance to erythromycin and clindamycin (MIC >256mug/mL). The results obtained by AP-PCR and PCR-ribotyping revealed genetic heterogeneity among the strains isolated from patients' fecal samples. However, similarity was observed among environmental strains and strains isolated from patients' fecal samples. Considering the importance of emergency room patients as a potential source of C. difficile strains, it appears to be important examine these patients for C. difficile before transfer to the other hospital units.