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Biomedical subjects

M H Wilcox

Publications and source records attributed to M H Wilcox.

At least 19 recordsLinked to original sources
PubMed1997

Evaluation of a novel endoluminal brush method for in situ diagnosis of catheter related sepsis.

AIMS: To determine the accuracy of a novel endoluminal brush method for the diagnosis of catheter related sepsis (CRS), which is performed in situ and hence does not require line sacrifice. METHODS: 230 central venous catheters in 216 patients were examined prospectively for evidence of CRS or colonisation using an endoluminal brush method in conjunction with peripheral blood cultures. The results were compared with those obtained using methods that require line sacrifice: extraluminal sampling (Maki roll) or endoluminal sampling (modified Cleri flush) of microorganisms. RESULTS: Only 16% of 128 patients suspected clinically of having line associated infection were confirmed as having CRS. In addition, 2 of 102 patients not suspected of having line associated infection had CRS. Line colonisation was apparent in approximately twice as many catheters using the Maki roll criteria (92%) compared with either the endoluminal brush (43%) or Cleri flush (43%). Furthermore, colonised catheters sampled using the Maki roll technique yielded mixed growth twice as often as when examined by endoluminal methods (17 and 8 cases, respectively). It was rare to detect either only endoluminal (4 of 22 episodes) or extraluminal (1 of 22 episodes) microorganisms in cases of CRS. In contrast, catheters defined as being colonised most frequently (59% of episodes) yielded only significant extraluminal growth. Only one case of CRS (5%) would have been "missed" if lines yielding a negative result from endoluminal brush sampling had been left in situ. Conversely, four episodes of CRS (18%) would not have been diagnosed by relying on extraluminal sampling alone. CONCLUSIONS: Diagnosis of CRS by the endoluminal brush method can be achieved without line sacrifice and is more sensitive (95%) and specific (84%) than extraluminal sampling of the catheter tip by the Maki roll technique (82% and 66%, respectively).

Adolescent↗
PubMed1996

Financial burden of hospital-acquired Clostridium difficile infection.

Clostridium difficile infection has become endemic in many hospitals and yet few data on the associated costs of such cases are available. We prospectively followed 50 consecutive cases of C. difficile infection and 92 control patients, who were admitted to the same geriatric wards within 72 h of the cases. Cases and controls had similar age, sex and major diagnosis distributions. Cases stayed significantly longer (mean 21.3 days, median 20.5 days; P < 0.001) in hospital than controls, including an average 14 days in a side room. Diarrhoea developed in cases on average 10.8 days after admission, which, when compared with a mean duration of stay for controls of 25.2 days, implies that C. difficile infection caused an increased duration of stay, as opposed to infection occurring because of longer residence. There was a significantly higher death rate in cases compared with controls (P < 0.01). Antibiotic treatment of C. difficile infection cost an average of Pounds 47 per case. The average number of laboratory investigations per day was similar for cases and controls, but the increased length of stay meant an extra cost for tests of approximately Pounds 210 per case. Assuming hotel costs of Pounds 150 (Pounds 200) per day stay (in a side room), 94% of the additional costs associated with C. difficile infection were due to increased duration of stay (Pounds 3850). The total identifiable increased cost of C. difficile infection was, therefore, in excess of Pounds 4000 per case. Such high costs can be used to justify expenditure on personnel and/or other control measures to reduce the incidence of this hospital-acquired infection.

Aged↗
PubMed1996

Review article: antibiotic-induced Clostridium difficile infection.

The great majority of cases of Clostridium difficile infection are hospital-acquired, and the reported incidence in England and Wales has increased sixfold between 1990 and 1993, with at least 17 patients dying in a recent large nosocomial outbreak. C. difficile infection accounts for an average 3-week increased length of stay in hospital. Acquisition of a toxigenic strain of Clostridium difficile may be followed by asymptomatic carriage, diarrhoea, colitis or pseudomembranous colitis. Antibiotic treatment and older age are major risk factors for the development of symptomatic disease, but less well-defined differences in strain virulence and host susceptibility are also probably important. Accurate data on the relative risks of different antibiotics to induce symptomatic C. difficile infection are scarce, but third-generation cephalosporins are frequently implicated. New kits are becoming available for the laboratory diagnosis of C. difficile infection but many of these lack sensitivity. Oral metronidazole or vancomycin are the main treatment options but avoidance of further antibiotics should also be encouraged where possible. The role of environmental C. difficile spores, which are highly resistant to conventional disinfectants, needs to be defined. Proven strategies for the prevention of C. difficile infection are required, in particular protocols to ensure that cross-infection does not occur.

Anti-Bacterial Agents↗
PubMed1996

True identity of control Staphylococcus aureus strains and their performance in the tube coagulase test.

One hundred laboratories were asked to submit their control Staphylococcus aureus strains to determine the true identity of strains presumed to be S. aureus NCTC 6571, and also to evaluate the performance of those strains being used as controls in the tube coagulase test (TCT). Of the 60 who replied, 55 laboratories sent at least one strain labelled as S. aureus NCTC 6571 (total of 64 strains). Of these, 84% were identified as S. aureus, and were indistinguishable from a fresh type strain by a combination of phenotypic methods including biotyping, antibiotic susceptibility testing and phage typing. Six-to-ten strains (9-16%), depending on the degree of stringency, were not identifiable as S. aureus NCTC 6571. The time since last retrieval from storage ranged from daily to > or = 3 years, but there was no correlation between this duration and the likelihood of differing from S. aureus NCTC 6571. Forty-seven laboratories submitted 51 strains used as controls in the TCT; these included 31 strains labelled as S. aureus NCTC 6571, eight wild strains, three other NCTC strains and nine strains of uncertain origin. Generally, the S. aureus NCTC 6571 strains produced weaker clots than the remainder. None of the S. aureus NCTC 6571 strains was found to be inoculum dependent but four of the other control strains were. The study demonstrates that some laboratories must improve procedures for ensuring that control S. aureus strains retain their true identity, particularly by avoiding repeated subcultures. Laboratories are divided in their use of strong or weak (S. aureus NCTC 6571) positive controls for the TCT. S. aureus NCTC 6571 is a more stringent control for the TCT than other control strains presently being used and is, therefore, to be preferred.

Anti-Bacterial Agents↗
PubMed1996

Effect of pH changes in cerebrospinal fluid specimens on bacterial survival and antigen test results.

AIMS: To determine the effect of pH changes occurring in cerebrospinal fluid (CSF) after sampling on the viability of meningitis causing bacteria, and on the performance of agglutination assays used for the rapid detection of bacterial antigens. METHODS: The pH of CSF collected via lumbar puncture was measured by various methods, and the effects of the following different incubation conditions on subsequent changes were determined: air at 4 degrees C; air at room temperature (22 degrees C); air at 37 degrees C; and air with 5% CO2 at 37 degrees C. The growth/survival in pooled CSF of 15 bacterial isolates collected from 74 patients with meningitis was assessed in these incubation conditions over 24 hours. The effects of pH changes in the CSF on the sensitivity of two latex agglutination and one co-agglutination kits for detecting Haemophilus influenzae, Neisseria meningitidis groups B and C, and Streptococcus pneumoniae were determined. RESULTS: The measured pH of CSF was highly affected by the method used and particularly the time delay between patient sampling and assay. Measured pH values at the time of sampling (mean 7.5) increased rapidly within 60 seconds by about one unit. CSF pH continued to increase during incubation in all tested conditions (up to approximately pH 10), with the exception of in air with 5% CO2 at 37 degrees C where pH changes were reversible and near physiological values were attained. Bacterial survival for all species tested was poorest in CSF incubated in air at 37 degrees C and best following exposure to air with 5% CO2 at 37 degrees C. Agglutination in rapid antigen detection kits with CSF incubated in air as opposed to air with 5% CO2 generally took longer to occur and in some instances was less prominent. In one case a false negative result was obtained with CSF seeded with N meningitidis group B incubated in the former but not the latter conditions. CONCLUSIONS: CSF pH increases after patient sampling are minimised and/or mostly reversed by incubation in an atmosphere containing 5% CO2. CSF samples should ideally be placed in such an atmosphere as soon as possible after collection, and left there until laboratory processing occurs, to reduce the detrimental effects of pH stress on bacterial survival. pH increases may also reduce the likelihood of obtaining a positive result in rapid antigen detection assays.

Antigens, Bacterial↗
PubMed1996

Accuracy of serology for the diagnosis of Helicobacter pylori infection--a comparison of eight kits.

AIMS: To determine the accuracy of eight commercially available kits for the serological diagnosis of Helicobacter pylori infection, and hence whether a serology service could be introduced to reduce endoscopy workload. METHODS: Eighty four patients newly presenting to their general practitioners with dyspepsia were recruited. Gold standard diagnosis of H pylori infection was obtained both by a histological examination of gastroduodenal biopsy specimens and by the 14C-urea breath test (UBT). The performance of six quantitative and two qualitative enzyme linked immunosorbent assays for H pylori IgG, used according to the manufacturers' instructions, with serum samples obtained during the endoscopy visit, were compared. RESULTS: The study population had a median age of 45 years, and the prevalence of H pylori infection was 35%. With one exception, where the patient had received a course of anti-H pylori treatment between endoscopy and UBT, there was 100% concordance in the results of the two gold standard techniques. Discordant serology results were more common in patients aged > 50 years (42% of the total) than in younger patients (21%), and this was most noticeable in uninfected patients. The sensitivity of the kits was good (90-100%), but specificity was more variable (76-96%), and the rate of equivocal results was unacceptably high in some cases (0-12%). The overall accuracy of the kits ranged from 83 to 98%. Two kits in particular performed well (Pylori-Elisa II, Bio-Whitaker and Premier, Launch; qualitative) with 98% and 100% accuracy, respectively. CONCLUSIONS: In a symptomatic population with a prevalence of H pylori infection of 35%, particularly in patients aged < 50 years, some but not all serology kits may be used as a highly accurate and inexpensive alternative to the gold standard techniques.

Adult↗
PubMed1995

Campylobacter fetus subspecies fetus septicaemia: SDS-PAGE as an aid to speciation.

We describe a case of bacteraemia due to an atypical strain of Campylobacter fetus ssp. fetus. Conventional biochemical and phenotypic characterisation was unhelpful but whole cell protein profiles obtained by means of sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) allowed us to identify this strain.

Bacteremia↗
PubMed1995

Aeromonas infections and their treatment.

With advances in the identification and molecular taxonomy of Aeromonas spp., these organisms, which are widely distributed in the environment, are increasingly being recognised as human pathogens. Clinical infections include gastroenteritis, skin and soft tissue infections and bacteraemia. Antibiotic resistance poses a potential problem in the antimicrobial therapy of infections cased by Aeromonas spp. While most strains are susceptible to chloramphenicol, ciprofloxacin, co-trimoxazole and the aminoglycosides, the activity of amoxycillin/clavulanate and the acylureidopenicillins is inconsistent. Addition of a beta-lactamase inhibitor does not significantly enhance the activity of the acylureidopenicillins. Aztreonam and the carbapenems, imipenem and meropenem remain highly active. Although resistance to the first and second generation cephalosporins is variable, more than 90% of Aeromonas spp. are susceptible to the third generation agents. Of potential significance is the identification of chromosomally-encoded inducible beta-lactamases, associated with resistance to extended spectrum penicillins, cephalosporins, monobactams and carbapenems, in clinical isolates of Aeromonas spp. Two distinct enzymes are produced: the A1 enzyme, a serine beta-lactamase behaving as a group 1 cephalosporinase, and the A2 enzyme, a metallo beta-lactamase which hydrolyses a wide range of beta-lactam agents including the carbapenems. The clinical relevance of these enzymes in Aeromonas spp. is unclear.

Aeromonas↗
PubMed1995

An audit of ciprofloxacin use in a district general hospital.

An audit of ciprofloxacin use at Southmead Hospital, Bristol was carried out for forty patients treated in early 1992 employing a modified Delphi technique with six assessors. Most patients assessed (20/40, 50%) had urinary tract infections (UTIs), 5/40 (12.5%) had chest infections, 4/40 (10%) had bacterial gastroenteritis and 3/40 (7.5%) had either bacteraemia or infection following an orthopaedic procedure. A likely bacterial pathogen was isolated from 32/40 (80%) of patients; 14/32 (44%) had Pseudomonas aeruginosa infections and from the remainder Enterobacteriaceae including Salmonella spp. (non-typhoid) were cultured. Oral therapy with ciprofloxacin was used in 37 (93%) of the 40 patients, and the three others received iv treatment. In 21/35 (60%) of patients where an assessment was made by majority scoring, a quinolone was felt to be clinically justified. A quinolone was least likely to be thought justified if the patient had a chest infection. The assessors had few concerns about the effectiveness or toxicity of ciprofloxacin but for 41% (14/34) of patients, where there was a majority opinion, a cheaper alternative was felt to be available; most of these patients had hospital-acquired UTIs caused by Enterobacteriaceae. The duration of therapy was felt to be too long in 35% (10/29) of patients, mainly because of prolonged treatment of UTIs. In some cases of P. aeruginosa infection the assessors would have used higher doses than those prescribed. Ciprofloxacin was the quinolone of choice in 24/32 (75%) of assessable cases. Norfloxacin was chosen to treat UTI due to multi-resistant Enterobacteriaceae in 6.2% (2/32) cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Infective Agents↗
PubMed1995

Diarrhoea caused by Clostridium difficile: response time for treatment with metronidazole and vancomycin.

One hundred patients, known to have been excreting Clostridium difficile cytotoxin in faeces, were reviewed retrospectively to determine the response time for treatment with oral metronidazole and vancomycin, and the effect of the additional administration of anti-motility agents. Records were available for 78 patients of whom 58 had received treatment with either metronidazole or vancomycin. Response and relapse rates were similar for the two treatment regimens. However, the mean duration of symptoms was significantly shorter in evaluable patients treated with vancomycin (3.0 days, n = 22) compared with those given metronidazole (4.6 days, n = 28) (Mann-Whitney-U, P < 0.01). No difference in the duration of symptoms, irrespective of antibiotic therapy, was associated with use of anti-motility agents. The increased cost of vancomycin compared with metronidazole for the treatment of C. difficile infection may be justifiable by reductions in the length of stay in hospital or in the need for nursing in isolation facilities, consequent upon a shorter symptomatic response time. Administration of anti-motility agents did not appear to impair response in patients with mild to moderate C. difficile infection.

Adult↗