- Volume 66, Issue 4, 2017
Volume 66, Issue 4, 2017
- Clinical Microbiology
-
-
-
Molecular epidemiological survey of Treponema pallidum in pregnant women in the Zhabei District of Shanghai
Yingying Lu, Qi Wu, Li Wang and Liting JiPurpose. To evaluate the epidemiological characteristics of syphilis, such as incidence, vertical transmission and genotypes, in pregnant women in the Zhabei District of Shanghai. In addition, the changes in genotypes and the efficiency of genotyping were evaluated.
Methodology. We screened 3022 pregnant women for syphilis in the Shanghai Zhabei Central Hospital. Whole blood, plasma, earlobe blood and specimens from genital ulcers or skin/mucosal lesions were collected from syphilis-positive patients. Samples were genotyped by analysing a combination of three genes: tpr, arp and tp0548 (the tpr/arp/tp0548 genotype). Clinical data were further collected to evaluate disease incidence, maternal–neonatal transmission and social factors.
Results. Out of 3022 pregnant women screened for syphilis, 41 were syphilis-positive. Of these, 43.9 % showed vertical transmission (18/41). The prevalence of syphilis in pregnant women was 1.32 %, higher than that in other districts in Shanghai in 2014. Genotyping was performed in 10/11 (90.9 %) samples of syphilis lesions, 8/41 (19.5 %) blood samples, 12/41 (29.3 %) plasma samples, and 20/39 (48.7 %) earlobe blood samples. The predominant genotype was 14d/f, followed by 15d/f, 13a/f, 13d/f and 9o/c. Genotype 13a/f was reported for the first time in the Shanghai area since 2010.
Conclusion. The prevalence of syphilis in pregnant women in the Zhabei District was higher than that in other areas in Shanghai and the genotype is variable.
-
-
-
-
First genotype identification of Trichosporon asahii in Sfax, Tunisia
Purpose. The objectives of our study were species identification and genotyping of Trichosporon isolates collected at the Parasitology and Mycology Laboratory in Sfax, Tunisia.
Methodology. Molecular identification was carried out by analysing the IGS1 regions of the rDNA of 30 Trichosporon isolates.
Results. Trichosporon asahii was the most frequent species detected. Furthermore, four genotypes were identified in Tunisia: 1 (46.4 %), 4 (35.7 %), 7 (14.3 %) and 3 (3.6 %). In vitro antifungal susceptibility testing of the isolates showed that voriconazole exhibited the highest activity.
Conclusion. This is the first reported study of genotype identification of T. asahii in Tunisia and even in the African continent.
-
-
-
Resistotyping, phenotyping and genotyping of New Delhi metallo-β-lactamase (NDM) among Gram-negative bacilli from Iranian patients
More LessPurpose. The purpose of this study was to investigate New Delhi metallo-β-lactamase (NDM) production among Gram-negative bacilli.
Methodology. Antibiogram-resistotyping and detection of New Delhi metallo-β-lactamase (NDM) in clinical isolates of Klebsiella pneumoniae, Acinetobacter baumannii and Pseudomonas aeruginosa and comparative evaluation of the diagnostic performance of three phenotypic methods for NDM detection, with PCR considered as the gold standard, were performed. Minimum inhibitory concentration (MIC) of antibiotics against NDM-positive strains using E-tests and clonal relationship analysis using enterobacterial repetitive intergenic consensus (ERIC)-PCR in these strains were determined.
Results. The most effective antibiotics against strains of the species K. pneumoniae were Colistin, Chloramphenicol and Tigecycline; against P. aeruginosa were Fosfomycin and Polymyxins, and against A. baumannii were Polymyxins, Ampicillin/Sulbactam and Minocycline. Overall, 66, 31 and 40 different resistotypes were observed among K. pneumoniae, A. baumannii and P. aeruginosa strains, respectively. The bla NDM-1 gene was detected in 28 (8.5 %) strains of the bacteria investigated. The sensitivities and specificities of the Meropenem-EDTA combined disk test, the meropenem-dipicolinic acid combined disk test and the modified Hodge test methods for NDM detection were 96.43, 55.15; 96.43, 54.85; and 89.29, 35.15, respectively. Additionally, in spite of the low positive predictive values of these tests, their negative predictive values were high. ERIC-PCR results revealed two main clusters in NDM-positive strains of each of the species P. aeruginosa and A. baumannii, and ten main clusters in K. pneumoniae. In all the NDM-positive strains maximum MIC rates (>256) were observed for all beta-lactam antibiotics.
Conclusion. There were high levels of antibiotic resistance and a high frequency of multi-drug resistance and extensive-drug resistance profiles, as well as highly prevalent bla NDM-1 genes in the bacteria investigated.
-
-
-
Rapid detection of Mycobacterium tuberculosis and rifampicin resistance in extrapulmonary tuberculosis and sputum smear-negative pulmonary suspects using Xpert MTB/RIF
Background. Tuberculosis (TB) is a serious public health problem in developing countries such as Pakistan. Rapid diagnosis of TB and detection of drug resistance are very important for timely and appropriate management of multidrug-resistant TB (MDR-TB).
Objective. The purpose of this study was to determine the diagnostic efficacy of the Xpert MTB/RIF assay for rapid diagnosis of TB and detection of rifampicin (RIF) resistance in extrapulmonary and smear-negative pulmonary TB suspects.
Methods. A total of 98 bronchoalveolar lavage fluid (BALF) and 168 extrapulmonary specimens were processed by Xpert MTB/RIF. Culture results are considered as the gold standard for diagnosis of TB, and drug susceptibility testing for detection of RIF resistance. Diagnostic efficacy was measured in terms of sensitivity, specificity and positive and negative predictive values.
Results. The Xpert MTB/RIF assay detected 40 (40.8 %) of 98 BALF of presumptive pulmonary TB and 60 (35.7 %) of 168 extrapulmonary specimens. Sensitivity and specificity of the Xpert MTB/RIF assay for detection of TB was 86 and 88.4 %, respectively. The positive predictive value was 71.5 % while negative predictive value was 95.1 %.
Conclusion. The Xpert MTB/RIF assay is a rapid and simple technique with high sensitivity and specificity for diagnosing TB and detecting drug resistance in extrapulmonary and smear-negative TB cases.
-
-
-
Characterization of the translation elongation factor 1-α gene in a wide range of pathogenic Aspergillus species
Purpose. We aimed to evaluate the resolving power of the translation elongation factor (TEF)-1α gene for phylogenetic analysis of Aspergillus species.
Methodology. Sequences of 526 bp representing the coding region of the TEF-1α gene were used for the assessment of levels of intra- and inter-specific nucleotide polymorphism in 33 species of Aspergillus, including 57 reference, clinical and environmental strains.
Results. Analysis of TEF-1α sequences indicated a mean similarity of 92.6 % between the species, with inter-species diversity ranging from 0 to 70 nucleotides. The species with the closest resemblance were A. candidus/A. carneus, and A. flavus/A. oryzae/A. ochraceus, with 100 and 99.8 % identification, respectively. These species are phylogenetically very close and the TEF-1α gene appears not to have sufficient discriminatory power to differentiate them. Meanwhile, intra-species differences were found within strains of A. clavatus, A. clavatonanicus, A. candidus, A. fumigatus, A. terreus, A. alliaceus, A. flavus, Eurotium amstelodami and E. chevalieri. The tree topology with strongly supported clades (≥70 % bootstrap values) was almost compatible with the phylogeny inferred from analysis of the DNA sequences of the beta tubulin gene (BT2). However, the backbone of the tree exhibited low bootstrap values, and inter-species correlations were not obvious in some clades; for example, tree topologies based on BT2 and TEF-1α genes were incompatible for some species, such as A. deflectus, A. janus and A. penicillioides.
Conclusion. The gene was not phylogenetically more informative than other known molecular markers. It will be necessary to test other genes or larger genomic regions to better understand the taxonomy of this important group of fungi.
-
-
-
In vitro and in vivo assessments of Rhodomyrtus tomentosa leaf extract as an alternative anti-streptococcal agent in Nile tilapia (Oreochromis niloticus L.)
More LessPurpose. Rhodomyrtustomentosa is a Thai medicinal plant that has been attracting attention for its remarkable antibacterial properties against Gram-positive pathogenic bacteria. The purpose of this study was to evaluate the antibacterial properties of R. tomentosa leaf extract against Streptococcus agalactiae and Streptococcus iniae isolated from infected tilapia.
Methodology. The anti-streptococcal activity of R. tomentosa was determined using broth microdilution assays.
Results. The extract demonstrated strong antibacterial activity against the fish pathogens, with minimum inhibitory concentrations (MICs) ranging from 7.8‒62.5 µg ml−1. It was found to possess a dose-dependent bacteriostatic effect on this organism. Scanning electron microscopy revealed irregular and long chains of swollen cells, as well as corkscrew shapes andincomplete separation of cell division of S. agalactiae cells following the treatment at sub-MIC. Moreover, S. agalactiae cells pre-treated with the extract became more sensitive to oxidative stress induced by H2O2 than the untreated cells. Based on the mortality of Nile tilapia after intraperitoneal infection of S. agalactiae at median lethal dose (LD50), the pre-treated cells caused a significant (P<0.01) reduction in mortality of S. agalactiae-infected Nile tilapia.
Conclusion. The results suggested that R. tomentosa could be further developed as a simple and effective agent for the treatment of streptococcosis in Nile tilapia.
-
-
-
Bactericidal mechanisms and effector targets of TiO 2 and Ag-TiO 2 against Staphylococcus aureus
More LessPurpose. In our previous study, Ag+-loaded TiO2 and Ag+-loaded SiO2 coatings for tracheal intubation were prepared to prevent ventilator-associated pneumonia (VAP), but the antimicrobial targets and the underlying mechanisms of TiO2 and Ag-TiO2 (Ag+) are still unclear. We attempted to elucidate the antimicrobial activity and potential mechanisms against Staphylococcus aureus.
Methodology. The study tested the TiO2 and Ag+ bacteriostatic activity against S. aureus strains by MIC assays and S. aureus growth curves, lesion in the membranes by surface hydrophobicity tests, conductivity tests and measurements of DNA and RNA contents in S. aureus cultures, and investigated the inhibition of soluble protein and nucleic acid synthesis by measurements of soluble protein content, fluorescent intensity and nucleic acid content of living S. aureus.
Results. The MIC values of TiO2 and Ag+ were 1.6 mg ml−1 and 5.781 µg ml−1. TiO2 and Ag+ could inhibit the growth of S. aureus. After treatment with TiO2 and Ag+, the surface hydrophobicity was significantly reduced, the conductivity of cultures increased, and DNA and RNA content in cultures showed no obvious changes. The expressions of soluble proteins and nucleic acid contents of living S. aureus were reduced after treatment with TiO2 and Ag+.
Conclusion. TiO2 and Ag+ could cause slight lesion in the membrane to affect S. aureus membrane permeability, but not decomposition of membrane. Moreover, TiO2 and Ag+ could lead to reduced expression of soluble protein by inhibiting the synthesis of nucleic acids, thereby further inhibiting the growth of S. aureus.
-
-
-
Culture-independent detection of chlorhexidine resistance genes qacA/B and smr in bacterial DNA recovered from body sites treated with chlorhexidine-containing dressings
Purpose. Dressings containing chlorhexidine gluconate (CHG) are increasingly used in clinical environments for prevention of infection at central venous catheter insertion sites. Increased tolerance to this biocide in staphylococci is primarily associated with the presence of qacA/B and smr genes.
Methodology. We used a culture-independent method to assess the prevalence of these genes in 78 DNA specimens recovered from the skin of 43 patients at catheter insertion sites in the arm that were covered with CHG dressings.
Results. Of the 78 DNA specimens analysed, 52 (67 %) possessed qac A/B and 14 (18 %) possessed smr; all samples positive for smr were also positive for qacA/B. These prevalence rates were not statistically greater than those observed in a subsample of specimens taken from non-CHG treated contralateral arms and non-CHG-dressing exposed arms. A statistically greater proportion of specimens with greater than 72 h exposure to CHG dressings were qac-positive (P=0.04), suggesting that the patients were contaminated with bacteria or DNA containing qacA/B during their hospital stay. The presence of qac genes was not positively associated with the presence of DNA specific for Staphylococcus epidermidis and Staphylococcus aureus in these specimens.
Conclusion. Our results show that CHG genes are highly prevalent on hospital patients’ skin, even in the absence of viable bacteria.
-
-
-
Group B streptococcal bacteriuria during pregnancy as a risk factor for maternal intrapartum colonization: a prospective cohort study
Purpose. Current evidence is inconclusive regarding the intrapartum administration of chemoprophylaxis, merely based on the presence of group B streptococcal (GBS) bacteriuria of any colony count, in the prevention of early-onset neonatal GBS infection. The aim of this study was to assess whether GBS bacteriuria is a risk factor for intrapartum colonization (IPC) regardless of urinary concentration or the results of late third-trimester rectovaginal screening cultures (RVSCs).
Methodology. Six hundred and eight pregnant women, with urine specimens cultured between May 2011 and May 2013, were enrolled in this prospective cohort study. RVSCs were available for 582 women and intrapartum rectovaginal cultures for 246.
Results. The prevalence of GBS bacteriuria and positive RVSCs was 10.8 and 16.5 %, respectively. The frequency of IPC was 15.9 % (39/246). Sensitivity, specificity, positive and negative predictive values of urine culture and of RVSC in predicting GBS IPC were 41, 94.7, 59.3 and 89.5 %, and 76.9, 95.4, 76.9 and 95.4 %, respectively. GBS bacteriuria was significantly associated with IPC, overall [relative risk (RR) 5.6] and in women with negative RVSC (RR 8.5), with bacteriuria <104 c.f.u. ml−1 (RR 5.9) or when both circumstances coexisted (RR 8.9). The urinary colony count was <104 c.f.u. ml−1 in 13 of the 16 women with GBS bacteriuria and IPC.
Conclusion. GBS bacteriuria is a risk factor for IPC, irrespective of urinary GBS concentration or of colonization status at late gestation. Therefore, microbiology laboratories should search, and report, GBS of any colony count in urine from pregnant women, and not only in the presence of ≥104 c.f.u. ml−1 as the 2010 CDC guidelines recommend.
-
-
-
Antibiotic susceptibility of planktonic- and biofilm-grown staphylococci isolated from implant-associated infections: should MBEC and nature of biofilm formation replace MIC?
More LessPurpose. The purpose of this study was to develop an alternative, more clinically relevant approach to susceptibility reporting for implant-associated infections. Using 20 staphylococcal isolates, isolated from clinical implant infections, the majority (85 %) demonstrated biofilm-forming capabilities. A significantly increased minimum biofilm eradication concentration (MBEC) compared to minimum inhibitory concentration (MIC) breakpoint was obtained, with MBEC values greater than 256 µg ml−1 for the majority of bacteria. Such a vast increase was also demonstrated for isolates defined as negligible biofilm formers via crystal violet staining, likely due to the high protein content of biofilms, as confirmed by proteinase-K treatment.
Methodology. This study employed a variety of techniques to assess MIC and MBEC of the isolates tested. In addition, the nature of bacterial biofilm across a range of clinical isolates was investigated using crystal violet staining, sodium metaperiodate and proteinase-K treatment, and PCR analysis.
Results/Key findings. Infection of medical implants is associated with increased rates of infection and increased bacterial tolerance to antibiotic strategies. Clinical significance is due to the presence of pathogens attached to biomaterial surfaces enclosed in an extracellular polymeric matrix termed the biofilm. This article highlights the importance of defining the clinical susceptibility of implant-associated infections in vitro using methods that are relevant to the biofilm phenotype in vivo, and highlights how current planktonic-based antimicrobial susceptibility tests are often misleading.
Conclusion. The use of biofilm-relevant susceptibility tests would improve patient outcomes by enabling correct antimicrobial regimens to be rapidly identified, reducing treatment failure and halting the spread of antimicrobial-resistant strains.
-
- Microbial Ecology and Health
-
-
-
Evaluation of three different bottles in BACTEC 9240 automated blood culture system and direct identification of Candida species to shorten the turnaround time of blood culture
More LessPurpose. Candida spp. are the most common causes of fungemia. Rapid and accurate diagnostic methods are very important for appropriate management of candidemia. At present, blood culture is the essential diagnostic test despite having a long detection time and low sensitivity rate. We aimed to investigate the ways to shorten the turnaround time from blood culture collection to final identification in candidemia.
Methodology. Sixty clinical bloodstream isolates of Candida were included, and Plus Aerobic/F, Peds Plus/F and Mycosis IC/Fbottles were used with a BACTEC 9240 blood culture instrument. Germ tube production, carbohydrate assimilation (API 20C AUX) and peptide nucleic acid fluorescent in situ hybridization yeast traffic light tests were performed directly from positive-signalled bottles.
Results. Time to positivity of blood cultures was affected by species of Candida, fungal load and bottle type. Candida tropicalis had the shortest and Candida glabrata had the longest time to positivity. Mycosis IC/F culture bottle had a significant superiority in the isolation of yeasts, especially for C. glabrata and if there was a low fungal load in the bottle. Direct germ tube test had 90 % sensitivity and 97.6 % specificity for Candida albicans in two hours after signalling. The compliance between direct and classical assimilation tests was 98.3 %. Sensitivity and specificity of peptide nucleic acid fluorescent in situ hybridization were 100 %.
Conclusion. We think that it is possible to shorten the turnaround time for the identification of Candida in blood culture even with currently available methods.
-
-
- Microbial Epidemiology
-
-
-
Occurrence of qnrB1 and qnrB12 genes, mutation in gyrA and ramR, and expression of efflux pumps in isolates of Klebsiella pneumoniae carriers of bla KPC-2
Purpose. The occurrence of quinolone-resistance genes (qnrA, qnrB and qnrS), the presence of mutations in gyrA, gyrB and parC, as well as the expression of efflux pumps (acrB and acrF) and mutations in the gene ramR.
Methodology. Were investigated in 30 bla KPC-2-positive isolates of Klebsiella pneumoniae taken from infection and colonization in hospital patients from Recife-PE, Brazil. The detection of the qnr, acrB and acrF genes and analysis of the mutations in ramR and the quinolone-resistance-determining regions of gyrA, gyrB and parC were performed by PCR followed by DNA sequencing.
Results. Among the isolates analysed, 73.3 % (n=22) presented the qnrB gene. For the DNA sequencing, six isolates (K3-A2, K12-A2, K25-A2, K27-A2, K19-A2 and K3-C2) were selected and the qnrB1 and qnrB12 variants were detected. This is the first ever report, to the best of our knowledge, of the presence of qnrB12 in K. pneumoniae. This is also the first report, to the best of our knowledge, of the presence of qnrB1 or qnrB12 with bla KPC-2 in K. pneumoniae in Brazil. Mutations were observed in gyrA S83 and in ramR. All isolates presented genes for the acrB and a crF efflux pumps and the reverse transcription PCR performed showed that the pumps were being expressed.
Conclusion. KPC-2-positive isolates colonizing patients, which also showed qnrB, mutation in gyrA and efflux pumps, may be important reservoirs for disseminating these resistance mechanisms in the hospital environment.
-
-
-
-
Accuracy of diagnostic tests for Legionnaires' disease: a systematic review
More LessPurpose. Rapid and effective diagnosis of Legionnaires’ disease (LD) cases is extremely important so that timely and appropriate therapy can be provided, thereby lowering the morbidity and mortality rates and reducing the health and economic costs associated with this disease.
Methodology. Diagnosis is established solely by microbiological tests. There are several methods available, each with different performance, sensitivity and specificity characteristics, and further understanding is required. Our objective was to assess the accuracy of urinary antigen detection, direct fluorescent antibody (DFA) staining, serological testing and the polymerase chain reaction (PCR) method versus culture analysis (the reference standard) in patients suspected of being infected with Legionella or patients with laboratory-confirmed LD. We performed a MEDLINE search in November 2014. Two authors independently assessed the trials and extracted data. Pooled analysis was performed through Meta-DiSc version 1.4.
Result. The inclusion criteria were met by 11 studies. All the studies evaluated PCR and DFA tests to detect Legionella in clinical specimens, comparing them to culture techniques, and were included in the meta-analysis. The pooled sensitivity and specificity for PCR were 83 % [95 % confidence interval (CI): 79–87 %] and 90 % (95 % CI: 88–92 %), respectively. DFA was evaluated in one study and the sensitivity and specificity of this test were 67 % (95 % CI: 30–93 %) and 100 % (95 % CI: 91–100 %), respectively. PCR had high sensitivity and specificity for early diagnosis of LD.
Conclusion. Culture analysis is deemed necessary for epidemiological studies, molecular strain typing and antibiotic sensibility evaluations; however, the performance of PCR in recent studies calls for additional, well-designed studies in order to achieve the best standard test, which will enable optimization of the Legionella infection diagnostic.
-
-
-
Prevalence of Burkholderia species, including members of Burkholderia cepacia complex, among UK cystic and non-cystic fibrosis patients
Purpose. We aimed to establish the prevalence of different Burkholderia species among UK cystic fibrosis (CF) and non-CF patients over a 2 year period.
Methodology. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry was used to identify isolates to genus level, followed by recA/gyrB sequence clustering or species-specific PCR. In all, 1047 Burkholderia isolates were submitted for identification from 361 CF patients and 112 non-CF patients, 25 from the hospital environment and three from a commercial company. Potential cross-infection was assessed by pulsed-field gel electrophoresis (PFGE) and multi- locus-sequence typing (MLST). MICs were determined for 161 Burkholderia cepacia complex (Bcc) isolates. CF Trust registry data were sought to examine clinical parameters relating to Bcc infection.
Results. Burkholderia multivorans was the most prevalent species among CF patients affecting 56 % (192) patients, followed by Burkholderia cenocepacia IIIA (15 %; 52 patients). Five novel recA clusters were found. Among non-CF patients, Burkholderia cepacia was the most prevalent species (37/112; 34 %), with 18 of 40 isolates part of a UK-wide B. cepacia ‘cluster’. This and three other clusters were investigated by PFGE and MLST. Cable-pili positive isolates included two novel sequence types and representatives of ET12. Antibiotic susceptibility varied between and within species and CF/non- CF isolates. CF Trust registry data suggested no significant difference in lung function between patients harbouring B. cenocepacia, B. multivorans and other Bcc species (P=0.81).
Conclusion. The dominance of B. multivorans in CF, the presence of a B. cepacia cluster among non-CF patients and the existence of putative novel species all highlighted the continuing role of Burkholderia species as opportunistic pathogens.
-
-
-
Genetic analysis of human parainfluenza virus type 3 obtained in Croatia, 2011–2015
Purpose. This study investigated the HPIV3 circulating strains in Croatia and whether the other parts of HPIV3 genome (F gene and HN 582 nucleotides fragment) could be equally suitable for genetic and phylogenetic analysis.
Methodology. Clinical materials were collected in period 2011–2015 from children suffering from respiratory illnesses. In positive HPIV3 samples viral genome was partially amplified and sequenced for HN and F genes. Obtained sequences were analysed by phylogenetic analysis and genetic characterization was performed.
Results. All samples from this study belonged to subcluster C and over a short period of time, genetic lineage C3a gained prevalence over the other C genetic lineages, from 39 % in 2011 to more than 90 % in 2013 and 2014. Phylogenetic classifications of HPIV3 based on the entire HN gene, HN 582 nt fragment and entire fusion (F) gene showed identical classification results for Croatian strains and the reference strains. Molecular analysis of the F and HN glycoproteins, showed their similar nucleotide diversity (Fcds P=0.0244 and HNcds P=0.0231) and similar Ka/Ks ratios (F Ka/Ks=0.0553 and HN Ka/Ks=0.0428). Potential N-glycosylation sites, cysteine residues and antigenic sites are generally strongly conserved in HPIV3 glycoproteins from both our and the reference samples.
Conclusion. The HPIV3 subclaster C3 (genetic lineage C3a) became the most detected circulating HPIV3 strain in Croatia. The results indicated that the HN 582 nt and the entire F gene sequences were as good for phylogenetic analysis as the entire HN gene sequence.
-
-
-
Characterisation of clinically isolated Streptococcus pyogenes from balanoposthitis patients, with special emphasis on emm89 isolates
More LessPurpose. Streptococcus pyogenes causes a variety of diseases, such as pharyngitis and toxic shock syndrome. In addition, this bacterium is a causative agent of balanoposthitis. To reveal the bacteriological characteristics of the isolates from balanoposthitis patients, we analysed 47 isolates. In addition, novel clade genotype emm89 S. pyogenes isolates have been reported to be spreading worldwide recently. Hence, we further analysed eight emm89 isolates.
Methodology. A drug susceptibility experiment was performed and emm types were determined. More detailed experiments, such as PCR analysis for the presence of virulence-associated genes and MLST analysis, were performed especially using emm89 isolates.
Results. All isolates were sensitive to ampicillin, but 34 % of the isolates were resistant to at least one antibiotic. The emm types of the isolates varied, with emm89 and emm11 being the most prevalent, but the emm1 type was not detected. The analysis of emm89 isolates revealed that drug susceptibilities varied. All isolates were negative for the hasABC gene and produced active NADase that are characteristics of novel clade genotype emm89 S. pyogenes. MLST analysis demonstrated that six isolates were of the ST101 type, the most predominant type reported thus far, but two isolates were of the ST646 type. According to the PCR analysis used to determine the presence of streptococcal pyrogenic exotoxin-related genes, the six ST101 isolates were further classified into four groups.
Conclusion. These results suggest that balanoposthitis is caused by a variety of types of S. pyogenes, with novel clade genotype emm89 isolates playing a role in balanoposthitis infections in Japan.
-
-
-
Importance of adhesins in the recurrence of pharyngeal infections caused by Streptococcus pyogenes
More LessPurpose. Pharyngo-amygdalitis is the most common infection caused by Streptococcus pyogenes (S. pyogenes). Reinfection with strains of different M types commonly occurs. However, a second infection with a strain of the same M type can still occur and is referred to as recurrence. We aimed to assess whether recurrence of S. pyogenes could be associated to erythromycin resistance, biofilm formation or surface adhesins like fibronectin-binding proteins and pilus proteins, both located in the fibronectin-binding, collagen-binding, T-antigen (FCT) region.
Methodology. We analyed clinical isolates of S. pyogenes obtained from children with multiple positive cultures of throat swabs. We analysed potential associations between M types, clonal patterns, biofilm production and FCT types with their capacity of producing a recurrent infection. We genetically defined recurrence as an infection with the same M type (same strain) and reinfection as an infection with a different M type.
Results. No differences were observed between recurrent and reinfection isolates in relation to erythromycin resistance, presence and number of domains of prtF1 gene, and biofilm formation capacity; the only significant difference was the higher frequency of FCT-4 type among recurrent isolates. However, when all the factors that could contribute to recurrence (erythromycin resistance, biofilm production, presence of prtF1 gene and FCT-4 type) were analysed together, we observed that recurrent isolates have a higher number of factors than reinfection isolates.
Conclusions. Recurrence seems not to be associated with biofilm formation. However, pili and fibronectin-binding proteins could be associated with recurrence because FCT-4 isolates which harbour two fibronectin-binding proteins are more frequent among recurrent isolates.
-
- Pathogenicity and Virulence/Host Response
-
-
-
Increase in human immunodeficiency virus 1 diversity and detection of various subtypes and recombinants in north-eastern Brazil
Purpose. Diverse human immunodeficiency virus 1 (HIV-1) subtypes and circulating recombinant forms are found in Brazil. The majority of HIV-1 molecular epidemiological studies in Brazil have been conducted in the southern and south-eastern regions of the country, although several recent studies in the north-eastern region have addressed this issue. The objective of this study was to molecularly characterize HIV-1 circulating in Pernambuco, north-eastern Brazil.
Methodology. A total of 64 samples were collected from 2002 to 2003, and another 103 were collected from 2007 to 2009. The protease and partial reverse transcriptase regions of the HIV-1 polymerase-encoding (pol) gene were sequenced, and subtyping, recombination and phylogenetic analyses were performed.
Results/Key findings. Subtype B (60.9 %) was found to be predominant, followed by HIV-1 F (31.4 %). Several BF recombinants (4.2 %), and BC and AG recombinants were also identified. The intra-subtype genetic diversity was estimated to be 0.065 (sd±0.004) for HIV-1 B and 0.055 (sd±0.004) for HIV-1 F, reflecting a greater accumulation of mutations in subtype B (P<0.01). More codons were found to be under positive selective pressure in samples collected from 2007 to 2009, from individuals with a T-cell count≥200 cells mm−3 and from women. Coalescence data indicated that the subtype F population has been continuously expanding.
Conclusions. HIV-1 shows high genetic diversity in the state of Pernambuco. Thus, additional molecular evaluations of circulating strains will provide a better understanding of the epidemic and may lead to more effective preventive strategies.
-
-
-
-
Autophagy induction regulates influenza virus replication in a time-dependent manner
Purpose. Autophagy plays a key role in host defence responses against microbial infections by promoting degradation of pathogens and participating in acquired immunity. The interaction between autophagy and viruses is complex, and this pathway is hijacked by several viruses. Influenza virus (IV) interferes with autophagy through its replication and increases the accumulation of autophagosomes by blocking lysosome fusion. Thus, autophagy could be an effective area for antiviral research.
Methodology. In this study, we evaluated the effect of autophagy on IV replication. Two cell lines were transfected with Beclin-1 expression plasmid before (prophylactic approach) and after (therapeutic approach) IV inoculation.
Results/Key findings. Beclin-1 overexpression in the cells infected by virus induced autophagy to 26 %. The log10haemagglutinin titre and TCID50 (tissue culture infective dose giving 50 % infection) of replicating virus were measured at 24 and 48 h post-infection. In the prophylactic approach, the virus titre was enhanced significantly at 24 h post-infection (P≤0.01), but it was not significantly different from the control at 48 h post-infection. In contrast, the therapeutic approach of autophagy induction inhibited the virus replication at 24 and 48 h post-infection. Additionally, we showed that inhibition of autophagy using 3-methyladenine reduced viral replication.
Conclusion. This study revealed that the virus (H1N1) titre was controlled in a time-dependent manner following autophagy induction in host cells. Manipulation of autophagy during the IV life cycle can be targeted both for antiviral aims and for increasing viral yield for virus production.
-
-
-
Increased drug resistance of meticillin-resistant Staphylococcus aureus biofilms formed on a mouse dermal chip model
More LessPurpose. Meticillin-resistant Staphylococcus aureus (MRSA) biofilm formation in humans is of serious clinical concern. Previous in vitro studies have been performed with biofilms grown only on inorganic substrates; therefore, we investigated the vancomycin (VCM) resistance of MRSA biofilms grown on skin tissue.
Methodology. We established a novel tissue substrate model, namely MRSA grown on segments of mouse skin tissue (dermal chips, DCs), and compared its resistance capacity against VCM with that of MRSA biofilms grown on plastic chips (PCs).
Results/Key findings. For one MRSA isolate, we found that the VCM MIC was identical (1.56 µg ml−1) for planktonic cultures and for biofilms-formed on PCs (PC-BF), although the minimum bactericidal concentration (MBC) increased to 6.25 µg ml−1 in PC-BF. On the contrary, the MIC and MBC for biofilms formed on DCs (DC-BF) significantly increased (25 and 50 µg ml−1, respectively). Furthermore, the minimum biofilm-eradicating concentration was higher for DC-BF (100 µg ml−1) than for PC-BF (25 µg ml−1). Using six MRSA strains, we found that in PC-BF, the c.f.u. number decreased with increasing VCM concentration, whereas in DC-BF, it greatly increased until the MIC was reached, accompanied by the formation of large colonies, thicker bacterial walls and the presence of many mitotic cells.
Conclusion. Our results indicate that the VCM resistance of MRSA was greater in DC-BF. We conclude that DCs may provide a specific environment for MRSA that enhances bacterial growth under cytotoxic VCM concentrations, and might be useful for the study of skin wound infections and the effects of antimicrobial drugs.
-
Volumes and issues
-
Volume 73 (2024)
-
Volume 72 (2023 - 2024)
-
Volume 71 (2022)
-
Volume 70 (2021)
-
Volume 69 (2020)
-
Volume 68 (2019)
-
Volume 67 (2018)
-
Volume 66 (2017)
-
Volume 65 (2016)
-
Volume 64 (2015)
-
Volume 63 (2014)
-
Volume 62 (2013)
-
Volume 61 (2012)
-
Volume 60 (2011)
-
Volume 59 (2010)
-
Volume 58 (2009)
-
Volume 57 (2008)
-
Volume 56 (2007)
-
Volume 55 (2006)
-
Volume 54 (2005)
-
Volume 53 (2004)
-
Volume 52 (2003)
-
Volume 51 (2002)
-
Volume 50 (2001)
-
Volume 49 (2000)
-
Volume 48 (1999)
-
Volume 47 (1998)
-
Volume 46 (1997)
-
Volume 45 (1996)
-
Volume 44 (1996)
-
Volume 43 (1995)
-
Volume 42 (1995)
-
Volume 41 (1994)
-
Volume 40 (1994)
-
Volume 39 (1993)
-
Volume 38 (1993)
-
Volume 37 (1992)
-
Volume 36 (1992)
-
Volume 35 (1991)
-
Volume 34 (1991)
-
Volume 33 (1990)
-
Volume 32 (1990)
-
Volume 31 (1990)
-
Volume 30 (1989)
-
Volume 29 (1989)
-
Volume 28 (1989)
-
Volume 27 (1988)
-
Volume 26 (1988)
-
Volume 25 (1988)
-
Volume 24 (1987)
-
Volume 23 (1987)
-
Volume 22 (1986)
-
Volume 21 (1986)
-
Volume 20 (1985)
-
Volume 19 (1985)
-
Volume 18 (1984)
-
Volume 17 (1984)
-
Volume 16 (1983)
-
Volume 15 (1982)
-
Volume 14 (1981)
-
Volume 13 (1980)
-
Volume 12 (1979)
-
Volume 11 (1978)
-
Volume 10 (1977)
-
Volume 9 (1976)
-
Volume 8 (1975)
-
Volume 7 (1974)
-
Volume 6 (1973)
-
Volume 5 (1972)
-
Volume 4 (1971)
-
Volume 3 (1970)
-
Volume 2 (1969)
-
Volume 1 (1968)