- Volume 64, Issue 12, 2015
Volume 64, Issue 12, 2015
- Commentary
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70th Anniversary Collection for the Microbiology Society: Journal of Medical Microbiology
More LessIn the last 70 years, we have seen a radical change in our perception and understanding of the microbial world. During this period, we learned from Woese and Fox there exists a third kingdom called ‘Archea’ based on the phylogenetic studies of the 16S rRNA that revolutionized microbiology ( Woese & Fox, 1977 ; Woese et al., 1978 ). Furthermore, we were forced to reckon with the fact that Koch and Pasteur's way of growing cells in test-tubes or flasks planktonically does not necessarily translate to the real-life scenario of bacterial lifestyle, where they prefer to live and function as a closely knit microbial community called biofilm. Thanks are due to Costerton, who led the crusade on the concept of biofilms and expanded its scope of inquiry, which forced scientists and clinicians worldwide to rethink how we evaluate and apply the data. Then progressively, disbelief turned into belief, and now it is universally accepted that the micro-organisms hobnob with the members of their community to communicate and coordinate their behaviour, especially in regard to growth patterns and virulence traits via signalling molecules. Just when we thought that we were losing the battle against bacteria, antimicrobials were discovered. We then witnessed the rise and fall of antibiotics and the development of antibiotic resistance. Due to space and choice limitation, we will focus on the three areas that caused this major paradigm shift (i) antimicrobial resistance (AMR), (ii) biofilm and (iii) quorum sensing (QS), and how the Journal of Medical Microbiology played a major role in advancing the shift.
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- Review
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Staphylococcus aureus ST121: a globally disseminated hypervirulent clone
More LessStaphylococcus aureus is a leading cause of bacterial infections in hospitals and communities worldwide. With the development of typing methods, several pandemic clones have been well characterized, including the extensively spreading hospital-associated meticillin-resistant S. aureus (HA-MRSA) clone ST239 and the emerging hypervirulent community-associated (CA) MRSA clone USA300. The multilocus sequence typing method was set up based on seven housekeeping genes; S. aureus groups were defined by the sharing of alleles at ≥ 5 of the seven loci. In many cases, the predicted founder of a group would also be the most prevalent ST within the group. As a predicted founder of major S. aureus groups, approximately 90 % of ST121 strains was meticillin-susceptible S. aureus (MSSA). The majority of ST121 strains carry accessory gene regulator type IV, whereas staphylococcal protein A gene types for ST121 are exceptionally diverse. More than 90 % of S. aureus ST121 strains have Panton–Valentine leukocidin; other enterotoxins, haemolysins, leukocidins and exfoliative toxins also contribute to the high virulence of ST121 strains. Patients suffering from S. aureus ST121 infections often need longer hospitalization and prolonged antimicrobial therapy. In this review, we tried to summarize the epidemiology of the S. aureus clone ST121 and focused on the molecular types, toxin carriage and disease spectrum of this globally disseminated clone.
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- Pathogenicity and Virulence/Host Response
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Effect of honokiol on exotoxin proteins listeriolysin O and p60 secreted by Listeria monocytogenes
Listeria monocytogenes is considered one of the most important foodborne pathogens. The virulence-related proteins listeriolysin O (LLO) and p60 are critical factors involved in Listeria pathogenesis. In the present study, we investigated the effect of honokiol on LLO and p60 secreted from L. monocytogenes. A listeriolysin assay was used to investigate the haemolytic activities of L. monocytogenes exposed to honokiol, and the secretion of LLO and p60 was detected by immunoblot analysis. Additionally, the influence of honokiol on the transcription of LLO and p60 genes (hly and iap, respectively) was analysed by real-time reverse transcription PCR. TNF-α release assays were performed to elucidate the biological relevance of changes in LLO and p60 secretion induced by honokiol. According to the data, honokiol showed good anti-L. monocytogenes activity, with MICs of 8–16 μg ml− 1, and the secretion of LLO and p60 was decreased by honokiol. In addition, the transcription of hly and iap was inhibited by honokiol. Our results indicate that TNF-α production by RAW264.7 cells stimulated with L. monocytogenes supernatants was inhibited by honokiol. Based on these data, we propose that honokiol could be used as a promising natural compound against L. monocytogenes and its virulence factors.
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- Clinical Microbiology
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Efficacy of the FilmArray blood culture identification panel for direct molecular diagnosis of infectious diseases from samples other than blood
Molecular-based techniques reduce the delay in diagnosing infectious diseases and therefore contribute to better patient outcomes. We assessed the FilmArray blood culture identification (BCID) panel (Biofire Diagnostics/bioMérieux) directly on clinical specimens other than blood: cerebrospinal, joint, pleural and ascitic fluids, bronchoscopy samples and abscesses. We compared the results from 88 samples obtained by culture-based techniques. The percentage of agreement between the two methods was 75 % with a Cohen κ value of 0.51. Global sensitivity and specificity using the FilmArray BCID panel were 71 and 97 %, respectively. Sensitivity was poorer in samples with a low bacterial load, such as ascitic and pleural fluids (25 %), whereas the sensitivity for abscess samples was high (89 %). These findings suggest that the FilmArray BCID panel could be useful to perform microbiological diagnosis directly from samples other than positive blood cultures, as it offers acceptable sensitivity and moderate agreement with conventional microbiological methods. Nevertheless, cost–benefit studies should be performed before introducing this method into algorithms for microbiological diagnostics.
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- Microbial Epidemiology
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Antibiotic surgical prophylaxis increases nasal carriage of antibiotic-resistant staphylococci
More LessStaphylococci are a significant cause of hospital-acquired infection. Nasal carriage of Staphylococcus aureus is an important risk factor for infection in surgical patients and coagulase-negative staphylococci (CNS) are a major cause of prosthetic joint infections. The impact that antibiotic surgical prophylaxis has on the nasal carriage of staphylococci has not been studied. Daily nasal swabs were taken from 63 patients who received antibiotic surgical prophylaxis and 16 patients who received no antibiotics. Total aerobic bacterial count, S. aureus and CNS were enumerated by culture from nasal swabs. Representative isolates were typed by staphylococcal interspersed repeat units (SIRU) typing and PFGE, and MICs to nine antibiotics were determined. After antibiotic administration, there was a reduction in S. aureus counts (median − 2.3 log10c.f.u. ml− 1) in 64.0 % of S. aureus carriers, compared with only a 0.89 log10c.f.u. ml− 1 reduction in 75.0 % of S. aureus carriers who did not receive antibiotics. A greater increase in the nasal carriage rate of meticillin-resistant CNS was observed after antibiotic surgical prophylaxis compared with hospitalization alone, with increases of 16.4 and 4.6 %, respectively. Antibiotic-resistant S. epidermidis carriage rate increased by 16.6 % after antibiotic administration compared with 7.5 % with hospitalization alone. Antibiotic surgical prophylaxis impacts the nasal carriage of both S. aureus and CNS.
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Characterization of the extra-intestinal pathogenic Escherichia coli ST131 clone among isolates recovered from urinary and bloodstream infections in the United Kingdom
More LessThe multidrug-resistant ST131-O25b clone of Escherichia coli is well established as a significant cause of extra-intestinal infections worldwide. However, there have been only two small regional studies comparing ST131 isolates from the UK. Therefore, we characterized 143 ST131 E. coli (38 urinary, 105 bloodstream) collected between January 2011 and March 2012 from 38 centres located across the UK and Republic of Ireland. Phenotypic and genotypic characterization of clonal isolates revealed high rates of resistance to amoxicillin-clavulanate (56 %), cefotaxime (32 %), ciprofloxacin (79 %), temocillin (69 %, bloodstream isolates only), gentamicin (67 %) and trimethoprim–sulfamethoxazole (59 %). The most frequently detected extended-spectrum beta-lactamase was CTX-M-15 (87 %), predominantly encoded on IncF plasmids, although it was also associated with IncU plasmids in two isolates. The majority of UK ST131 clonal isolates possessed the O25b antigen (97 %) and the H30 fimH allele (92 %), but three serogroups (O19a, O136 and O153) novel to ST131 were identified among our strains. Contrary to previous reports, UK ST131-O16 isolates were typically susceptible to ciprofloxacin and lacked beta-lactamase genes (n = 12/12). In summary, ST131 strains of E. coli circulating in the UK possess characteristic clonal features, but are becoming more diverse than other international ST131 populations.
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- Prevention and Therapy
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Amphibian antimicrobial peptide fallaxin analogue FL9 affects virulence gene expression and DNA replication in Staphylococcus aureus
The rapid rise in antibiotic-resistant pathogens is causing increased health concerns, and consequently there is an urgent need for novel antimicrobial agents. Antimicrobial peptides (AMPs), which have been isolated from a wide range of organisms, represent a very promising class of novel antimicrobials. In the present study, the analogue FL9, based on the amphibian AMP fallaxin, was studied to elucidate its mode of action and antibacterial activity against the human pathogen Staphylococcus aureus. Our data showed that FL9 may have a dual mode of action against S. aureus. At concentrations around the MIC, FL9 bound DNA, inhibited DNA synthesis and induced the SOS DNA damage response, whereas at concentrations above the MIC the interaction between S. aureus and FL9 led to membrane disruption. The antibacterial activity of the peptide was maintained over a wide range of NaCl and MgCl2 concentrations and at alkaline pH, while it was compromised by acidic pH and exposure to serum. Furthermore, at subinhibitory concentrations of FL9, S. aureus responded by increasing the expression of two major virulence factor genes, namely the regulatory rnaIII and hla, encoding α-haemolysin. In addition, the S. aureus-encoded natural tolerance mechanisms included peptide cleavage and the addition of positive charge to the cell surface, both of which minimized the antimicrobial activity of FL9. Our results add new information about FL9 and its effect on S. aureus, which may aid in the future development of analogues with improved therapeutic potential.
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Bacteriocin-producing strains of Lactobacillus plantarum inhibit adhesion of Staphylococcus aureus to extracellular matrix: quantitative insight and implications in antibacterial therapy
More LessIn the present study, the adhesion of bacteriocin-producing probiotic strains of Lactobacillus plantarum onto extracellular matrix (ECM) proteins such as collagen and mucin and their potential to prevent pathogen invasion onto the ECM was ascertained. Fluorescence-based in vitro assays indicated that L. plantarum strains CRA21, CRA38 and CRA52 displayed considerable adhesion to ECM molecules, which was comparable to the probiotic Lactobacillus rhamnosus GG. Flow cytometry-based quantitative assessment of the adhesion potential suggested that L. plantarum CRA21 exhibited superior adhesion onto the ECM as compared with other lactic acid bacteria strains. Furthermore, fluorescence-based assays suggested that the highest inhibition of Staphylococcus aureus adhesion onto collagen and mucin by bacteriocin-producing L. plantarum strains was observed in the exclusion mode as compared with the competition and displacement modes. This observation was supported by the higher binding affinity (k d) for the ECM exhibited by the L. plantarum strains as compared with S. aureus. Interestingly, a crude plantaricin A extract from food isolates of L. plantarum displayed potent antibacterial activity on ECM-adhered S. aureus cells. It is envisaged that the L. plantarum isolates displaying bacteriocinogenic and ECM-adhering traits can perhaps be explored to develop safe antibacterial therapeutic agents.
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Probiotic attributes, antioxidant, anti-inflammatory and neuromodulatory effects of Enterococcus faecium CFR 3003: in vitro and in vivo evidence
More LessAccumulating evidence suggests that probiotic bacteria play a vital role in modulating various aspects integral to the health and well-being of humans. In the present study, probiotic attributes and the antioxidant, anti-inflammatory and neuromodulatory potential of Enterococcus faecium CFR 3003 were investigated by employing suitable model systems. E. faecium exhibited robust resistance to gastrointestinal stress conditions as it could withstand acid stress at pH 1.5, 2 and 3. The bacterium also survived at a bile salt concentration of 0.45 %, and better tolerance was observed towards pepsin and trypsin. E. faecium produced lactic acid as a major metabolic product, followed by butyric acid. Lyophilized cell-free supernatant (LCS) of E. faecium exhibited significant antioxidant capacity evaluated against 1,1-diphenyl-2-picryl-hydrazyl, ascorbate auto-oxidation, oxygen radical absorbance and reducing power. Interestingly, E. faecium, Lactobacillus rhamnosus GG MTCC 1408 and LCS showed a significant anti-inflammatory effect by negatively modulating TNF-α production and upregulating IL-10 levels in LPS-stimulated macrophage cell lines. In an in vivo mice model, the propensity of probiotic supplements to modulate endogenous oxidative markers and redox status in brain regions was assessed. Young mice provided with oral supplements (daily for 28 days) of E. faecium and L. rhamnosus exhibited diminished oxidative markers in the brain and enhanced activities of antioxidant enzymes with a concomitant increase in γ-aminobutyric acid and dopamine levels. Collectively, our findings clearly suggest the propensity of these bacteria to protect against tissue damage mediated through free radicals and inflammatory cytokines. Although the underlying molecular mechanisms need further studies, it is tempting to speculate that probiotics confer a neuroprotective advantage in vivo against oxidative damage-mediated neurodegenerative conditions.
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- Correspondence
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 69 (2020)
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Volume 68 (2019)
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Volume 67 (2018)
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Volume 66 (2017)
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Volume 65 (2016)
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Volume 64 (2015)
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Volume 63 (2014)
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Volume 62 (2013)
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Volume 61 (2012)
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Volume 60 (2011)
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Volume 59 (2010)
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Volume 58 (2009)
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Volume 57 (2008)
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Volume 56 (2007)
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Volume 55 (2006)
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Volume 54 (2005)
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Volume 53 (2004)
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Volume 52 (2003)
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Volume 51 (2002)
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Volume 50 (2001)
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Volume 49 (2000)
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Volume 48 (1999)
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Volume 47 (1998)
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Volume 46 (1997)
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Volume 45 (1996)
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Volume 44 (1996)
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Volume 43 (1995)
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Volume 42 (1995)
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Volume 41 (1994)
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Volume 40 (1994)
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Volume 39 (1993)
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Volume 38 (1993)
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Volume 37 (1992)
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Volume 36 (1992)
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Volume 35 (1991)
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Volume 34 (1991)
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Volume 33 (1990)
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Volume 32 (1990)
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Volume 31 (1990)
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Volume 30 (1989)
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Volume 29 (1989)
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Volume 28 (1989)
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Volume 27 (1988)
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Volume 26 (1988)
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Volume 25 (1988)
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Volume 24 (1987)
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Volume 23 (1987)
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Volume 22 (1986)
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Volume 21 (1986)
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Volume 20 (1985)
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Volume 19 (1985)
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Volume 18 (1984)
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Volume 17 (1984)
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Volume 16 (1983)
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Volume 15 (1982)
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Volume 14 (1981)
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Volume 13 (1980)
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Volume 12 (1979)
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Volume 11 (1978)
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Volume 10 (1977)
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Volume 9 (1976)
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Volume 8 (1975)
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Volume 7 (1974)
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Volume 6 (1973)
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Volume 5 (1972)
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Volume 4 (1971)
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Volume 3 (1970)
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Volume 2 (1969)
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Volume 1 (1968)