High prevalence of class 1 integrons in clinical isolates of methicillin-resistant Staphylococcus aureus from India.

INTRODUCTION: Class1 integrons are one of the prevalent mechanisms of antibiotic resistance gene transfer in Gram-negative organisms, but their prevalence and role in the spread of antibiotic resistance genes in methicillin-resistant Staphylococcus aureus (MRSA) is unexplored. The purpose of this study was to investigate the prevalence of class 1 integrons in clinical isolates of MRSA. MATERIALS AND METHODS: Total 143 MRSA isolates obtained from two different cities in India (Pune and Mumbai) were characterized by biochemical tests, and the antibiotic sensitivity was performed using the Clinical and Laboratory Standards Institute (CLSI) guidelines. The presence of class 1 integrons, sul1/qacE0Δ1 region of class 1 integron and mecA gene among these isolates was determined by polymerase chain reaction (PCR). RESULTS: All 143 isolates were mecA positive and coagulase-positive. Overall, 71% of the MRSA isolates carried class 1 integrons; 58% (45/77) of the isolates obtained from Mumbai and 85% (56/66) of the isolates from Pune carried class 1 integrons. In all, 39% of these isolates carried sul1/qacEΔ1 region, thus confirming the association of class 1 integrons with antibiotic resistance genes. Along with ß-lactam antibiotics the MRSA isolates were resistant to several other antibiotics, with resistance to erythromycin, ciprofloxacin and trimethoprim-sulfamethoxazole being observed in 75%, 66% and 60% of the isolates, respectively. CONCLUSION: To the best of our knowledge, this is the first report of class 1 integrons in MRSA isolates from India. The study provides insights into the prevalence of a novel mechanism adapted by MRSA for the propagation of antibiotic resistance genes.

The risk of asthma exacerbation after reducing inhaled corticosteroids: a systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: Asthma guidelines suggest reducing controller medications when asthma is stable. METHODS: The purpose of the study is to estimate the risk of asthma exacerbation in stable asthmatics who reduce inhaled corticosteroids (ICS) compared to those who maintain a stable ICS dose. We identified articles from a systematic review of English and non-English articles using MEDLINE, EMBASE, Web of Science, and CENTRAL (inception to May 25, 2013). We included randomized controlled trials (RCTs) with a stable asthma run-in period of 4 weeks or more, an intervention to reduce ICS, and a follow-up period of at least 3 months. RESULTS: The search strategy identified 2253 potential articles, of which 206 were reviewed at the full-text level and 6 met criteria for inclusion. The relative risk of an asthma exacerbation in individuals who reduced ICS compared to those who maintained the same ICS dose was 1.25 (95% CI 0.96, 1.62; P = 0.10; I(2)  = 0%) in studies with a mean follow-up of 22 weeks. Individuals who reduced ICS had a decreased% predicted FEV1 of 0.87% (95% CI -1.58%,3.33%; P = 0.49, I(2)  = 58%) and a decreased mean morning peak expiratory flow of 9.57 l/min (95% CI 1.25, 17.90; P = 0.02; I(2)  = 74%) compared to those individuals who maintained a stable ICS dose. CONCLUSIONS: Asthma exacerbations were statistically no more likely among individuals who reduced ICS compared to those who maintained their ICS dose, supporting current guidelines which recommend decreasing ICS by 50% after a period of asthma stability.

The molecular basis of "curlicue": a sperm motility abnormality linked to the sterility of t haplotype homozygous male mice.

The t complex, a variant region of chromatin occupying approximately 40-million base pairs of proximal chromosome 17, exists in natural populations of wild mice of the Mus musculus species as a family of homologues called t haplotypes (t). Relative to wild-type (+) homologues, all t haplotypes share four large non-overlapping inversions, spanning 95% of the region, leading to intra-inversion recombination suppression in +/t heterozygotes. Non-lethal t homozygous males or complementing recessive lethal t doubly heterozygous males (hereafter both abbreviated "t/t males") are invariably and completely sterile, due to expression of several sperm function abnormalities. One of these traits, "curlicue", describes a condition in which spermatozoa from t/t males fail to reach the site of fertilization in vivo because they exhibit a severe loss of vigorous forward motility due to the chronic negative curvature of their flagella. Current data indicate that "curlicue" is the complex phenotypic reflection of the expression of three or more mutations clustered in the distal one-third of the largest and most-distal t complex inversion, In(17)4. From proximal to distal, candidates include Dnahc8, Tsga2 and Tctex5. Interestingly, new results from high-resolution intra-inversion genetic mapping and protein localization studies suggest that the products of the distal two candidates, Tsga2 and Tctex5, might play synergic roles in the expression of both the "curlicue" motility abnormality and the "stop" sperm-egg interaction aberration, regarded as functionally unrelated traits.

An axonemal dynein at the Hybrid Sterility 6 locus: implications for t haplotype-specific male sterility and the evolution of species barriers.

Poor sperm motility characterized by a distinct aberration in flagellar waveform known as "curlicue" is a hallmark of t haplotype (t) homozygous male sterility. Previous studies have localized "curlicue" and a flagellar developmental defect, "whipless", to the Hybrid Sterility 6 locus (Hst6), between the markers Pim1 and Crya1. More recent heterospecific breeding experiments between Mus spretus (Spretus) and Mus musculus domesticus (Domesticus) have mapped the primary source(s) of both "curlicue" and "whipless" to a small sub-locus of Hst6, Curlicue a (Ccua). Here we report the complete physical isolation of the Ccua locus and the identification of a candidate gene for expression of both "whipless" and "curlicue" at its proximal end, an axonemal dynein heavy chain gene, Dnahc8, formerly mapped by interspecific backcross analysis near Pim1. Dnahc8 mRNA expression commences in the Domesticus wild-type testis just prior to flagellar assembly and is testis-specific in the adult male. However, expression of Dnahc8 is not readily evident in the testis of either Spretus or "whipless" animals (Domesticus males homozygous for the Spretus allele of Dnahc8). Our results argue that Dnahc8 is fundamental to flagellar organization and function in Domesticus, but not Spretus, and suggest that Dnahc8 is integral to both Hst6- and t-specific male infertility.

Mutational analysis of transgenic mouse B cell lymphomas: indication of a Trp53-independent pathway in tumor progression.

Deregulated myc, bcl-2 and/or TP53 gene expression is associated with non-Hodgkin's B cell lymphomas (B-NHLs). Emu-N-myc transgenic mice that misexpress N-myc protein and carry a non-disrupted bcl-2 gene develop indolent B cell lymphomas reminiscent of the B-NHL, follicular lymphoma. Tumors from mice with end-stage disease exhibited discrete, nodular lesions as well as areas of diffuse tumor likely due to coalescence of enlarged follicles. Tumor DNAs were screened for mutations in the Trp53 gene, the murine homologue of the TP53 gene, which participates in B cell differentiation and survival. By PCR-based sequence analyses, we determined there were no mutations in exons 5-8, the common sites of TP53 mutation in B-NHLs. These findings suggested that disease progression in our novel murine lymphoma model may proceed via a Trp53-independent pathogenetic pathway.

Mapping and cloning recombinant breakpoints demarcating the hybrid sterility 6-specific sperm tail assembly defect.

Variants of the mouse t complex known as t haplotypes (t) express factors that perturb sperm differentiation, resulting in the non-Mendelian transmission of t from +/t heterozygous males and the sterility of t/t homozygous males. Previous studies of mice carrying heterospecific combinations of the t complex have revealed a 1-cM candidate locus, Hst6, for the distal-most of these factors, Tcd/Tcs2. Males heterozygous for the M. spretus allele of Hst6 and a t haplotype (Hst6(s)/t) are sterile, expressing an abnormality in sperm flagellar curvature ("curlicue") indistinguishable from one exhibited by sperm from t/t homozygotes. Hst6(s)/Hst6(s) males are also sterile; however, sperm produced by these males are completely immotile owing to the absence of assembled flagella. Recent studies have shown that the complete presentation of "curlicue" derives from expression of at least two factors within the locus, Curlicue a (Ccua) proximally and Curlicue b (Ccub) distally, with a factor affecting sperm-oolemma penetration, Stop1p, mapping between them. In the present report, we have examined expression of the Hst6-specific flagellar assembly phenotype in sperm from mice homozygous for M. spretus-M. m. domesticus recombinant Chr 17 homologs whose breakpoints map within the Hst6 locus. SSLP analysis of these homologs has demonstrated that the flagellar assembly defect maps to less than 0.2 cM between D17Mit61 and D17Mit135, coincident with Ccua. SSR content analysis of 23 BACs mapping to four contigs within the Hst6 locus has resulted in isolation of proximal and distal recombinant breakpoints circumscribing the flagellar assembly phenotype/Ccua factor. In addition, we have provided increased high-resolution mapping of the Stop1p and Ccub factors. These new data enhance our ability to isolate and characterize candidates for Tcd/Tcs2.

Study of coagulase positive and negative Staphylococci in clinical samples.

A total of 983 patients samples (pus, urine, sputum, throat swabs, blood culture, CSF, vaginal swabs, ear swabs) were studied for a period of one year. The incidence of coagulase positive Staphylococci was highest in pus and the incidence of coagulase negative Staphylococci was highest in conjunctival swabs. Antibiotic Sensitivity pattern of routinely used antibiotics was studied. Coagulase positive Staphylococci was found to be most sensitive to Ciprofloxacin followed by Norfloxacin and Gentamycin. Coagulase negative Staphylococci showed maximum sensitivity to Ciprofloxacin followed by Norfloxacin and Chloramphenicol.

Transgenic N-myc mouse model for indolent B cell lymphoma: tumor characterization and analysis of genetic alterations in spontaneous and retrovirally accelerated tumors.

Little is known about stepwise deregulation of specific genes leading to lymphoid malignancy. Aberrant myc gene expression in transgenic mice is correlated with B cell lymphomagenesis. We generated a unique transgenic mouse model in which deregulated murine E mu-N-myc transgene expression leads to development of indolent B cell lymphoma. Tumor cells were monoclonal, morphologically mature and surface immunoglobulin expressing B cells. Tumors arose in a disease course and exhibited a cytoarchitectural appearance reminiscent of human follicular lymphoma. Yet tumor cells were staged as preB since they failed to rearrange the immunoglobulin light chain genes. Retroviral insertion mutagenesis analyses of adult transgenic mice infected as newborns with murine leukemia virus revealed decreased disease latency, increased lymphoma incidence and a histologically more mature tumor type. Proviral insertion sites were not equivalent when accelerated E mu-N-myc indolent lymphomas were compared to accelerated c-myc preB cell lymphomas. The bcl-2 gene was not disrupted in either spontaneous or provirally accelerated E mu-N-myc lymphomas. These findings suggest that tumor progression in N-myc-associated indolent B cell lymphoma can proceed along diverse pathways involving distinctly different combinations of deregulated and/or intact genes than those pathways described in highly aggressive forms of myc-related murine preB cell disease.

Characterization of MboI repeat DNA sequence of Anopheles stephensi.

MboI repeat fragment of mosquito Anopheles stephensi has been isolated by molecular cloning. The restriction map and entire nucleotide sequence of the 433bp insert has been determined. Hybridization of this repeat DNA with restriction enzyme digest of mosquito DNA does not show an interspersed pattern but suggests that this repeat may be tandemly repeated at one major site and a few minor sites in the genome of Anopheles stephensi. The hybridization pattern also indicates that this repeat family comprises of many similar but non-identical sequences. An open reading frame encoding 66 amino acids with an initiation and two tandem termination codons has been identified. This putative 66 amino acid polypeptide sequence has significant homology to a small region of RNA tumour viral envelope protein.