Typing

About: Typing is a research topic. Over the lifetime, 5010 publications have been published within this topic receiving 146539 citations.

Evidence of nosocomial Stenotrophomonas maltophilia cross-infection in a neonatology unit analyzed by three molecular typing methods.

Abstract: Objective:To characterize the epidemiological relationships among Stenotrophomonas maltophilia isolates in the neonatology unit of our institution over a 4-month period in which an increased number of isolates was observed.Setting:The neonatology ward in a 2,000-bed university hospital in Madrid, Spain.Design:A retrospective molecular epidemiological analysis using three different typing methods, arbitrarily primed polymerase chain reaction (PCR), pulsed-field gel electrophoresis, and enterobacterial repetitive intergenic consensus-PCR, was performed with 11 isolates obtained from seven neonates over a 4-month period. Presumed unrelated isolates also were included as controls. A similarity dendrogram was obtained, to analyze the genetic relatedness among the isolates.Results:All isolates from the neonates, except one, showed a remarkably high homology among their typing patterns for the three methods assayed and clustered in the relatedness dendrogram at 96% similarity. The unrelated strains selected as controls were unclustered. The index case was considered to be a newborn who had an S maltophilia isolate from a culture drawn on the day of admission to the neonatology unit and which was included in the clustered similarity group.Conclusions:Such a high genetic similarity among the isolates, together with the presence of an index case who had been colonized or infected by S maltophilia before arrival at our institution, constitutes the first evidence of nosocomial cross-transmission of this microorganism.

Molecular typing of Stenotrophomonas (Xanthomonas) maltophilia by DNA macrorestriction analysis and random amplified polymorphic DNA analysis.

Abstract: Stenotrophomonas (Xanthomonas) maltophilia is a multidrug-resistant, nosocomial pathogen for which optimal typing methods in epidemiologic investigations of nosocomial outbreaks have not been defined. We compared DNA macrorestriction analysis by pulsed-field gel electrophoresis (PFGE) with random amplified polymorphic DNA (RAPD) analysis by arbitrarily primed PCR for molecular typing of 109 multidrug-resistant strains of S. maltophilia from multiple outbreaks at our institution over a 10-month period in 1993. PFGE after digestion with restriction endonuclease DraI revealed 62 unique DNA restriction profiles among the 109 strains, with 23, 11, 6, 6, and 3 strains having concordant profiles in each of five types. There were four concordant profiles among 8 strains (2 strains with each profile), while unique profiles were present in each of the remaining 52 strains. Further RAPD analysis with a decanucleotide primer showed the same number of distinct strain types as PFGE but more subtype diversity within each clonal type. We concluded that DNA macrorestriction analysis and RAPD analysis are sufficiently discriminatory and useful for differentiation of S. maltophilia strains in epidemiologic investigations of nosocomial outbreaks. However, RAPD analysis by arbitrarily primed PCR is faster and less laborious method of molecular typing.

Evaluation of Macrolide Resistance and Enhanced Molecular Typing of Treponema pallidum in Patients with Syphilis in Taiwan: a Prospective Multicenter Study

Abstract: Studies of macrolide resistance mutations and molecular typing using the newly proposed enhanced typing system for Treponema pallidum isolates obtained from HIV-infected patients in the Asia-Pacific region are scarce. Between September 2009 and December 2011, we conducted a survey to detect T. pallidum using a PCR assay using clinical specimens from patients with syphilis at six major designated hospitals for HIV care in Taiwan. The T. pallidum strains were genotyped by following the enhanced molecular typing methodology, which analyzed the number of 60-bp repeats in the acidic repeat protein (arp) gene, T. pallidum repeat (tpr) polymorphism, and the sequence of base pairs 131 to 215 in the tp0548 open reading frame of T. pallidum. Detection of A2058G and A2059G point mutations in the T. pallidum 23S rRNA was performed with the use of restriction fragment length polymorphism (RFLP). During the 2-year study period, 211 clinical specimens were obtained from 136 patients with syphilis. T. pallidum DNA was isolated from 105 (49.8%) of the specimens, with swab specimens obtained from chancres having the highest yield rate (63.2%), followed by plasma (49.4%), serum (35.7%), and cerebrospinal fluid or vitreous fluid (18.2%) specimens. Among the 40 fully typed specimens, 11 subtypes of T. pallidum were identified. Subtype 14f/f (18 isolates) was the most common isolates, followed by 14f/c (3), 14b/c (3), and 14k/f (3). Among the isolates examined for macrolide resistance, none had the A2058G or A2059G mutation. In conclusion, we found that type 14 f/f was the most common T. pallidum strain in this multicenter study on syphilis in Taiwan and that none of the isolates exhibited 23S rRNA mutations causing resistance to macrolides.