- Volume 61, Issue 1, 2012
Volume 61, Issue 1, 2012
- Diagnostics, typing and identification
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Identification of bacteria and potential sources in neonates at risk of infection delivered by Caesarean and vaginal birth
Neonatal gastric aspirates (NGA) are routinely screened in UK hospitals to investigate fetal/neonatal infections associated with cases of adverse pregnancy outcome (APO). The aim of this study was to describe and compare the microbiology of NGA from Caesarean and vaginal deliveries using molecular methods, and to evaluate other possible clinical and non-clinical variables that may have determined the presence of the bacteria in the samples. The value of using NGA and molecular methods to investigate potential pathogens associated with the risk of early infection was also evaluated. Bacteria were identified by a combined molecular approach on the basis of the 16S rRNA gene using both clone analysis and denaturing gradient gel electrophoresis. A total of 43 and 34 different species were identified in the vaginal (n = 121) and Caesarean (n = 119) deliveries, respectively; 26 of the species observed (51 %) were common to both modalities, although usually less prevalent in the Caesarean cases. Multivariate analysis confirmed an association between infection and prolonged rupture of membranes in vaginal deliveries (odds ratio = 5.7, 95 % confidence interval = 1.1–29.0). Various associations between infection and given variables were also shown, including labour, intrapartum antibiotic prophylaxis, and time and place of sample collection. The molecular methods allowed identification of a range of bacteria and potential sources not previously observed in NGA, including possible genito-urinary, gastrointestinal and oral pathogens. NGA represents a valuable sample for investigating potential pathogens associated with APO and the risk of early infection in neonates using molecular methods.
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Characterization of highly antimicrobial-resistant clinical pneumococcal isolates recovered in a Chinese hospital during 2009–2010
More LessNinety-one consecutive pneumococcal isolates (primarily from sputum), recovered in Chongqing Southwest Hospital during a 12 month period in 2009–2010 from individuals of all ages with suspected cases of pneumococcal disease, were subjected to PCR-serotyping, Quellung reaction serotyping, antimicrobial-susceptibility testing and multilocus sequence typing (MLST). Although 20 different serotypes were observed, most isolates (69, 75.8 %) were of serotypes included in the pneumococcal 13-valent conjugate vaccine (PCV13), including 33 of the 46 (71.7 %) isolates recovered from individuals less than 5 years of age. The prevalent serotypes were 19F (34 %), 19A (9.9 %), 6B (9.9 %), 23F (7.7 %), 14 (6.6 %) and 6A (4.4 %). PCR-determined serotypes were in agreement with Quellung testing, with the exception of two serotype 33C isolates. Most or all isolates within each PCV13 serotype were represented by one genotype, with the globally disseminated MLST sequence types (STs) ST271, ST320, ST90 and ST81 each accounting for the highly resistant isolates within serotypes 19F, 19A, 6B and 23F, respectively. Sixty-six (72.5 %) isolates were resistant to combinations of β-lactam antibiotics (BLAs). A total of 63 of these 66 (95.5 %) BLA-resistant isolates were of serotypes included in PCV13; however, 3 serogroup 15 isolates were also BLA-resistant. Most isolates (88/91 = 96.7 %) were resistant to erythromycin and clindamycin. The majority of isolates were also resistant to tetracycline (76, 84 %) and to cotrimoxazole (67, 74 %). This work revealed that the majority of antimicrobial-resistant isolates (50/91 = 54.9 %) recovered in this Chinese hospital were represented by four global clones. Serotypes for these as well as more obscure strains were readily determined by using PCR.
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Emergence of new PCR ribotypes from the hypervirulent Clostridium difficile 027 lineage
More LessClostridium difficile is the most common cause of antibiotic-associated diarrhoea worldwide. Over the past 10 years, the incidence and severity of disease have increased in North America and Europe due to the emergence of a hypervirulent clone designated PCR ribotype 027. In this study, we sought to identify phenotypic differences among a collection of 26 presumed PCR ribotype 027 strains from the US and the UK isolated between 1988 and 2008 and also re-evaluated the PCR ribotype. We demonstrated that some of the strains typed as BI by restriction endonuclease analysis, and presumed to be PCR ribotype 027, were in fact other PCR ribotypes such as 176, 198 and 244 due to slight variation in banding pattern compared to the 027 strains. The reassigned 176, 198 and 244 ribotype strains were isolated in the US between 2001 and 2004 and appeared to have evolved recently from the 027 lineage. In addition, the UK strains were more motile and more resistant to most of the antibiotics compared to the US counterparts. We conclude that there should be a heightened awareness of newly identified PCR ribotypes such as 176, 198 and 244, and that they may be as problematic as the notorious 027 strains.
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Multilocus differentiation of the related dermatophytes Microsporum canis, Microsporum ferrugineum and Microsporum audouinii
Microsporum ferrugineum, an uncommon causative agent of dermatophytosis, has restricted endemicity. Iranian strains suspected to be M. ferrugineum from two patients with tinea were analysed using the rDNA internal transcribed spacer (ITS) region and the partial β-tubulin (BT2) and translation elongation factor 1-α (TEF1) genes. Strains were compared to reference strains to differentiate M. ferrugineum from its relatives Microsporum canis and Microsporum audouinii. Inter-species differences for TEF1 and BT2 were found to be higher than for the ITS region, which is the current molecular standard for species identification in dermatophytes. Intra-species variation was zero for each of the markers. In silico analysis showed that the restriction enzymes BanI and BshNI were together sufficient to differentiate the three species based on TEF1, whereas a two-step digestion was needed with BT2 or the ITS region. The prevalence of M. ferrugineum in clinical samples in Iran appeared to be higher than suspected on the basis of routine phenotypic identification.
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Genetic relatedness of Pseudomonas aeruginosa isolates among a paediatric cystic fibrosis patient cohort in Ireland
Pseudomonas aeruginosa is one of the primary pathogens in the cystic fibrosis (CF) lung and a significant cause of morbidity and mortality. Reports of the spread of epidemic or transmissible strains of P. aeruginosa within and across CF centres in Europe have raised concern regarding the possibility of clonal spread among and within CF centres in Ireland. P. aeruginosa isolates (313 isolates from 142 sputum samples and 53 throat swabs) from 68 CF patients were examined using PFGE to explore the diversity of P. aeruginosa isolates among CF patients in a Dublin paediatric hospital. Only 57 different P. aeruginosa genotypes were identified among the 313 isolates. Forty-three of the genotypes were observed only in individual patients (distinct genotypes) while 13 cluster strains (present in two to four patients) were observed. Typing of P. aeruginosa isolates identified one indistinguishable clonal isolate of P. aeruginosa present in 13 CF patients (13/68; 19.1 %) which displayed higher levels of antibiotic resistance than those displayed by P. aeruginosa isolates of distinct genotype.
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Volumes and issues
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Volume 73 (2024)
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Volume 72 (2023 - 2024)
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Volume 71 (2022)
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Volume 70 (2021)
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Volume 68 (2019)
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