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B D Cookson

Publications and source records attributed to B D Cookson.

At least 19 recordsLinked to original sources
PubMed2001

Children with atopic dermatitis who carry toxin-positive Staphylococcus aureus strains have an expansion of blood CD5- B lymphocytes without an increase in disease severity.

Toxin-positive strains of Staphylococcus aureus (T + S. aureus) are present on the skin of some but not all patients with atopic dermatitis. Many staphylococcal toxins are superantigens, which can stimulate the immune response and thus may potentially lead to the very high levels of IgE characteristic of this condition, as well as exacerbating the clinical disease. The aim of this study was to determine whether the presence of T + S. aureus on the skin of children with atopic dermatitis was associated with in vivo evidence of a heightened humoral immune response, higher IgE levels and more severe clinical disease. Toxin gene expression in S. aureus isolated from the eczematous lesions of 28 children with atopic dermatitis was assessed by PCR. Clinical and immune data were also collected from this cohort. Thirteen of the 28 children (46%) were colonized with T + S. aureus strains. The presence of T + S. aureus was associated with a significant expansion in peripheral blood CD5- B cells (P = 0.01), and the more toxin types identified the greater the B-cell expansion (P = 0.002). However, in this cohort of children with atopic dermatitis, despite th in vivo expansion of B cells in children harbouring T + S. aureus, there was no associated increase in IgE levels or in clinical disease severity scores.

Adolescent↗
PubMed2001

Diploma in Hospital Infection Control: a progress report.

The Diploma in Hospital Infection Control (DipHIC) was established by the Hospital Infection Society (HIS), the London School of Hygiene and Tropical Medicine (LSHTM) and the Public Health Laboratory Service (PHLS) in 1997 and has now completed two examinations. We outline progress since the announcement of the diploma and changes to the written examination and reflective portfolio. The reflective process is described and guidance provided to active infection control practitioners wishing to consider application for the diploma by accreditation of prior learning.

Certification↗
PubMed2000

Do antimicrobials have a role in preventing septicaemia following instrumentation of the urinary tract?

Urinary tract instrumentation is a significant cause of septicaemia. Review of the literature suggests that selective use of antimicrobials would reduce the risk of septicaemia as this varies between patients and with procedures. Antimicrobial prophylaxis is indicated for patients at high risk of endocarditis, or who are neutropenic. For patients without these risk factors, it is indicated for open, transurethral, or certain forms of laser prostatectomy or trans-rectal prostate biopsy. For cystoscopy, antimicrobials are indicated for patients with preoperative bacteriuria or a preoperative indwelling catheter. Single dose aminoglycosides or oral fluoroquinolones are the agents of choice with the exception of the prevention of endocarditis, where combinations active against streptococci are recommended. For other instrumentations, the risk of antimicrobial toxicity probably outweighs the benefits and a risk-reduction strategy is recommended. Further studies are required to provide definitive answers in many of these areas.

Adult↗
PubMed2000

Methicillin-resistant Staphylococcus aureus in the community: new battlefronts, or are the battles lost?

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of nosocomial infections worldwide. Interpretation of community MRSA trends is problematical, in that the term is ill-defined, and related data are difficult to put into context. There are four relevant battlefronts, all of interest to risk assessment and prevention. These comprise the following: the issues relating to an increasing pool of patients with MRSA discharged from hospitals into the community; MRSA spreading to patients in nursing and residential homes; and MRSA spreading from patients and healthcare workers to others in the community. There are often difficulties in determining whether the fourth issue, MRSA arising apparently de novo in the community, is in fact due to one of these other fronts. All these battlefronts are important and not yet lost. However, we must agree on definitions and design-appropriate surveillance strategies, so that we can best inform prevention and control activities to contain these emerged or emerging problems.

Community-Acquired Infections↗
PubMed1999

Use of fluorescent amplified fragment length polymorphism (fAELP) to characterise methicillin-resistant Staphylococcus aureus.

The new PCR-based genotyping technique, fluorescent amplified fragment length polymorphism (fAFLP), was compared for discriminatory power and reproducibility with standard phenotypic methods, a coagulase gene (coa) restriction fragment length polymorphism (RFLP) method and pulsed-field gel electrophoresis (PFGE), in typing 34 isolates and four reference strains of methicillin-resistant Staphylococcus aureus (MRSA). The fAFLP showed from 40 to 75 fragments, 50 to 450 base pairs (bp) in size. Based on replicate studies, the isolates were judged indistinguishable when their fAFLP pattern was >93.7% similar. Only two of the isolates were indistinguishable by this criterion. Thirty-one MRSA fell into four major fAFLP groups (1, 2, 3 and 4) at the level of >79.9% similarity. Three other isolates and an EMRSA-16 strain fell outside these major groups. Within both fAFLP groups 1 and 2, two subgroups, A and B, could be identified at approximately 82.0% similarity. While most isolates within group 1 could also be separated by their phenotypic and coagulase gene (coa) RFLP pattern, all the isolates within fAFLP groups 2A and 2B were identical on the basis of these characters. The MRSA within fAFLP groups 3 and 4 were heterogeneous by their phenotypic characteristics and coa gene RFLP patterns. fAFLP was reproducible and distinguished between MRSA isolates that appeared identical by other methods. It is likely to contribute to the epidemiological analysis of outbreaks of MRSA infection.

Coagulase↗
PubMed1999

Nosocomial antimicrobial resistance surveillance.

The global threat of antimicrobial resistance and potentially untreatable infections is a serious matter under review currently by the WHO and many countries throughout the world. I consider the optimal surveillance scheme and point out the various biases in the systems that we have been using in the UK over the last decade. MRSA are used as an example where similar trends have been identified in these systems and the information has, once again, proved to be of value to the MRSA control working party.

Bacteremia↗
PubMed1999

PCR-RFLP analysis of the coagulase gene of Staphylococcus aureus: application to the differentiation of epidemic and sporadic methicillin-resistant strains.

Preventing cross-infection with epidemic strains of methicillin-resistant Staphylococcus aureus (MRSA) requires effective control measures. These call for simple, rapid, discriminatory and reproducible methods for typing this pathogen. In this study 140 isolates/strains from 105 hospitals in England and Wales, representing 72 diverse phage types, were analysed by bacteriophage typing and PCR coagulase (coa) gene restriction fragment length polymorphism (RFLP). Isolates gave a coa gene PCR product that was either 660 base pairs (bp), 603 bp or 547 pb in size. The PCR products were digested with Alu I and Cfo I, and the fragments separated by gel electrophoresis. Eight coa gene RFLP patterns, numbered 1 to 8, were observed. Pattern 3 was most common (N = 25 isolates), followed by patterns 2 and 5 (18 isolates each), pattern 1 (14 isolates), pattern 4 (11 isolates), pattern 7 (10 isolates), pattern 8 (eight isolates) and pattern 6 (six isolates). Isolates of the same phage type often gave different coa gene RFLP patterns, and the patterns within the epidemic types EMRSA-03, EMRSA-15 and EMRSA-16 were heterogeneous. Thus, representatives of EMRSA-03 were subtyped to coa RFLP patterns 1 and 2, those of EMRSA-05 to coa RFLP patterns 1, 2, 7 and 8, and those for EMRSA-16 to coa RFLP patterns 2, 3, 4, 5 and 6. The range of patterns within single phage types of S. aureus could help to discriminate between isolates/strains, and in a hierarchical approach coa gene RFLP could occupy an intermediate position between phage typing and pulsed-field gel electrophoresis (PFGE).

Bacteriophage Typing↗
PubMed1999

DNA banding pattern polymorphism in vancomycin-resistant Enterococcus faecium and criteria for defining strains.

The degree of DNA banding pattern polymorphism exhibited by vancomycin-resistant Enterococcus faecium (VREM) strains isolated on a renal unit over an 11-month period was investigated. Thirty VREM strains from different patients were analyzed by pulsed-field gel electrophoresis (PFGE; with extended run and optimal pulse times), ribotyping, plasmid profile analysis, biotyping, pyrolysis mass spectrometry, and antibiogram analysis. PFGE resolved 17 banding patterns which formed four distinct clusters at the 82% similarity level. Intercluster band differences ranged from 14 to 31 bands. The strains in one cluster, which contained seven patterns that differed from each other by one to seven bands and from the common pattern by five bands, were confirmed to be a single strain by four of the five other typing methods. The strains in a second cluster with eight patterns, which differed from each other by 1 to 12 bands, contained two subclusters. This subdivision was supported by ribotyping and biotyping. However, it was unclear whether these subclusters represented distinct strains. In one strain, marked polymorphism (patterns that differed from each other by up to four bands) was observed in the ribotype pattern. This study demonstrates the high degree of DNA banding pattern polymorphism found for some strains of VREM and illustrates the complexity involved in defining such strains.

Anti-Bacterial Agents↗
PubMed1998

The emergence of mupirocin resistance: a challenge to infection control and antibiotic prescribing practice.

Mupirocin was introduced into clinical practice in the UK in 1985, and has proved to be an extremely effective treatment of skin infections and one of the most successful topical antibiotics for the clearance of nasal Staphylococcus aureus isolates including those resistant to methicillin. It is currently registered for use in more than 90 countries worldwide. Unfortunately resistance was described shortly after its initial use. Many of the issues regarding its use are reviewed here, together with the mechanisms, genetics, surveillance and epidemiology of resistance, particularly in staphylococci. The various factors that increase resistance and how they might be controlled are also discussed.

Anti-Bacterial Agents↗
PubMed1998

Evaluation of disc diffusion and Etest for determining the susceptibility of Staphylococcus aureus to mupirocin.

The susceptibilities to mupirocin of 102 selected clinical isolates of Staphylococcus aureus and of control strain S. aureus NCTC 6571 were determined by disc diffusion (using discs containing 5, 15, 25, 30, 50 and 200 microg of mupirocin) and Etest and the results were compared with MICs determined using an agar incorporation method. On the basis of agar incorporation MICs, 42 isolates were sensitive to mupirocin (MIC < or = 4 mg/L), 39 showed low-level resistance (MICs = 8-128 mg/L) and 22 were highly resistant (MICs > or = 256 mg/L) and contained the mupA resistance gene. Using Stokes' criteria, none of the discs used gave major errors (sensitive isolates classified as highly resistant) or very major errors (highly resistant isolates classified as sensitive) in assigning a category of susceptibility, but minor errors (a difference of one category) were noted with all strengths. The best correlation with agar incorporation MIC was obtained with 25 microg mupirocin discs, which classified correctly 98 (95%) isolates, while worse correlations were noted with 5 microg and 200 microg discs which are the only types currently available commercially, for which there were 47 and 30 minor errors, respectively. The MICs found by Etest were the same as, or lower than, those determined by agar incorporation. Etests classified correctly all 42 mupirocin-sensitive isolates, 19 (49%) low-level resistant isolates and 16 (73%) highly resistant isolates. Two isolates that contained the mupA gene and showed agar incorporation MICs of 256 mg/L and 512 mg/L were not classified as highly resistant by any of the diffusion methods used. Agar incorporation MIC determination, possibly supported by detection of the mupA gene, offers the most effective means of identifying high-level mupirocin resistance in S. aureus, although the Etest also proved to be reproducible. However, we conclude that 25 microg discs warrant further evaluation for possible use in clinical laboratories, as they appear to be more reliable than the discs currently available.

Anti-Bacterial Agents↗
PubMed1998

Pneumococci causing invasive disease in Britain 1982-1990.

A total of 5348 isolates of Streptococcus pneumoniae was serotyped and screened for insusceptibility to tetracycline, penicillin, erythromycin and chloramphenicol. Of these, 4238 (79%) were isolated from patients who had pneumonia or meningitis or were bacteraemic. Altogether, 3948 (74%) of the isolates belonged to one or other of the serotypes 1, 3, 4, 6, 8, 9, 14, 19 or 23 with serotypes 6, 14, 18, 19 and 23 being frequent causes of invasive disease in young children. Many isolates of type 1 were isolated from pneumonia and few from meningitis. Some 768 (14%) isolates were insusceptible to one or more antibiotic and 591 of these belonged to serotypes 6, 9, 14, 19 or 23. Representatives of type 14 resistant to erythromycin were prominent from 1986 onwards. There was an increase in the number of multi-resistant pneumococci from 1985. Among these were isolates of type 23 insusceptible to penicillin, chloramphenicol and tetracycline and cultures of type 6 resistant additionally to erythromycin.

Adolescent↗
PubMed1998

Heterogeneous location of the mupA high-level mupirocin resistance gene in Staphylococcus aureus.

Epidemiologically unrelated clinical isolates of Staphylococcus aureus with high-level resistance to mupirocin (MIC > or = 512 mg/L) were studied to determine the location of the mupA resistance gene. The gene was carried on plasmids of variable size, some of which were transferable in vitro. DNA hybridisation of genomic DNA from 85 isolates showed that mupA was located on EcoRI fragments of seven different sizes; the most frequently observed fragments were 7 kb (46 isolates) or 4.1 kb (21 isolates). All isolates retained a 1.6-kb Nco I fragment that hybridised with mupA probes, but showed heterogeneous hybridisation patterns after digestion with Hinc II. These data suggested that mupA may be conserved, but that variation occurs in the flanking DNA proximal to it. Amplification of spacer regions between mupA and closest proximal copy of IS257 yielded products of variable size and was consistent with the presence of IS257 in either orientation. It is proposed that IS257-mediated events are responsible for the heterogeneity observed. The location of mupA varied between epidemiologically unrelated isolates of the same strain, including isolates of EMRSA-16 -- one of the two predominant methicillin-resistant strains in UK hospitals at the present time -- and this correlated with variations in the digestion patterns of the mupirocin resistance plasmids. The variable location of mupA should be evaluated further as a potential epidemiological tool with which to monitor the spread of high-level mupirocin resistance in EMRSA-16 or other strains of S. aureus.

Anti-Bacterial Agents↗
PubMed1998

Diversity of VanA glycopeptide resistance elements in enterococci from humans and nonhuman sources.

Elements mediating VanA glycopeptide resistance in 106 diverse enterococci from humans and nonhuman sources were compared with the prototype VanA transposon, Tn1546, in Enterococcus faecium BM4147. The isolates included 64 from individual patients at 15 hospitals in the United Kingdom (isolated between 1987 and 1996) and 42 from nonhuman sources in the United Kingdom (27 from raw meat, 7 from animal feces, and 8 from sewage). VanA elements were assigned to 24 groups (designated groups A to X) with primers that amplified 10 overlapping fragments of Tn1546. Ten groups of elements were found only in human enterococci, eight groups of elements were unique to nonhuman strains, and six groups of elements were common in enterococci from all sources. Elements indistinguishable from Tn1546 (group A) were observed more frequently in enterococci from nonhuman sources (34 versus 9%) but were identified in enterococci that caused outbreaks in hospital patients between 1987 and 1995. The most common group found in human enterococci (group H; 33%) was rarely observed in enterococci from other sources (5%). Group H elements differed from Tn1546 in three regions and included a novel insertion sequence, designated IS1542, between orf2 and vanR. The VanA elements of 14 other groups had a similar insertion at this position and/or distinct insertions at other positions. We conclude that VanA elements in enterococci are heterogeneous, although all show regions of homology with Tn1546. Furthermore, the elements most common among the human and nonhuman enterococci studied were different. This approach may be useful for monitoring the evolution of VanA resistance and may also be applicable in local "snapshot" epidemiological studies. However, as transposition events involving insertion sequences accounted for the differences observed between several groups, the stability of the elements must be assessed before their true epidemiological significance can be determined.

Animals↗
PubMed1998

Molecular typing of Staphylococcus aureus based on PCR restriction fragment length polymorphism and DNA sequence analysis of the coagulase gene.

A typing procedure for Staphylococcus aureus was developed based on improved PCR amplification of the coagulase gene and restriction fragment length polymorphism (RFLP) analysis of the product. All coagulase-positive staphylococci produced a single PCR amplification product of either 875, 660, 603, or 547 bp. Those strains of epidemic methicillin-resistant S. aureus 16 (EMRSA-16) studied all gave a product of 547 bp. PCR products were digested with AluI and CfoI, and the fragments were separated by gel electrophoresis. Ten distinct RFLP patterns were found among 85 isolates of methicillin-resistant S. aureus (MRSA) and 10 propagating strains (PS) of methicillin-sensitive S. aureus (MSSA) examined. RFLP patterns 1, 2, and 3 were specific to strains of EMRSA-3, -15, and -16, respectively. By contrast, RFLP patterns 4 and 5 were seen with a heterogeneous collection of strains, together with drug-resistant forms of S. aureus isolated in Europe and four propagating strains used for the international phage set. RFLP pattern 6 was given by the Airedale isolate and PS 95. RFLP pattern 7 encompassed EMRSA-2 (isolate 331), PS 94, and PS 96. An isolate from Germany gave RFLP pattern 8. Eight strains of MSSA gave patterns similar to those of methicillin-resistant strains (RFLP patterns 3, 4, 5, 6, and 7), but two, PS 42E and PS 71, gave unique RFLP patterns 9 and 10, respectively. The coagulase gene PCR products for 24 isolates of MRSA and two isolates of MSSA were sequenced for both strands. The sequences were aligned, and evolutionary lineages were inferred based on pairwise distances between isolates.

Bacterial Typing Techniques↗