Epidemiology and control of vancomycin-resistant enterococci (VRE) in a renal unit.

This study reports an outbreak of infection and colonization caused by vancomycin-resistant enterococci (VRE) in the renal service of a large teaching hospital. The polymerase chain reaction and pulsed-field gel electrophoresis were used to study the epidemiology of 26/34 strains of vancomycin-resistant Enterococcus faecalis and Enterococcus faecium from the outbreak in comparison with five strains from other hospitals in Edinburgh and the Borders, and three from other wards in the Royal Infirmary. The study revealed a heterogeneous population of vancomycin-resistant E. faecalis. Over 60% of E. faecium isolates had matching pulsed-field gel electrophoresis patterns and all of these were of VanA phenotype. These results suggest that clonal spread of VanA phenotype E. faecium within and possibly between hospitals is the major vancomycin-resistant enterococcal problem in Edinburgh. Screening of patients and isolation of colonized and infected patients appear to have been successful in controlling the spread of VRE.

A prospective controlled study of the association of Streptococcus bovis with colorectal carcinoma.

AIM: To investigate the ability of Streptococcus bovis to colonise colorectal cancers. PATIENTS: 19 patients with colorectal cancer and 23 controls without malignancy. SETTING: University teaching hospital. METHODS: Prospective study comparing unselected patients with known colorectal cancer with age and sex matched controls. Carcinoma tissue from patients with colorectal cancer and normal colonic mucosa, stool, and blood from both patients and control subjects were cultured. RESULTS: In contrast to published data, the faecal carriage rate was similar in cancer (11%) and control groups (13%). CONCLUSIONS: Faecal colonisation by Str bovis in colorectal cancer patients is lower than previously reported and does not differ significantly from controls.

Antibiotic resistance in nosocomial isolates in Scotland.

In this first multi-centre study in Scotland, 1028 consecutive Gram-negative and staphylococci strains were obtained from four major teaching hospitals. E. coli was the most common organism among both intensive care units (ICUs) (39%) and non-ICU strains (46.6%). The prevalence of antibiotic resistance among E. coli was always higher in isolates from ICUs than non-ICUs: ceftazidime (14.1%, 7.2%), ceftriaxone (12.7%, 6.1%), cefotaxime (15.5%, 8.7%), cefuroxime (28.8%, 20.8%), amoxicillin plus clavulanic acid (52.2%, 38.8%) and gentamicin (7.0%, 2.8%). The highest incidences of resistance were identified among Enterobacter/Citrobacter spp. from ICUs; 43.8%, 41.7%, 45.8%, 54.2%, 87.5% and 10.4% of these organisms were resistant to ceftazidime, ceftriaxone, cefotaxime, cefuroxime, amoxicillin plus clavulanic acid and gentamicin, respectively.

Biochemical properties of inducible beta-lactamases produced from Xanthomonas maltophilia.

Four different beta-lactamases have been found in several strains of Xanthomonas maltophilia isolated from blood cultures during 1984 to 1991 at the Edinburgh Royal Infirmary. One was a metallo-beta-lactamase with predominantly penicillinase activity and an isoelectric point of 6.8. Its molecular size as determined by gel filtration was 96 kDa but was only 26 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), suggesting a tetramer of four equal subunits. The enzyme hydrolyzed all classes of beta-lactams except the monobactam aztreonam. This enzyme was not inhibited by potassium clavulanate or BRL 42715 but was inhibited by p-chloromercuribenzoate, mercuric chloride, and EDTA. The beta-lactamase was unstable in 50 mM sodium phosphate buffer (pH 8.0) but stable in 50 mM Tris HCl (pH 8.0). The other beta-lactamases focused as a series of different isoelectric points, ranging from pI 5.2 to 6.6. Together, these enzymes exhibited a broad spectrum of activity, hydrolyzing most classes of beta-lactams but not imipenem or aztreonam. Their molecular size was 48 kDa by Sephadex gel filtration and 24 kDa by SDS-PAGE, indicating that they were enzymes consisting of two equal subunits. They were inhibited by p-chloromercuribenzoate, mercuric chloride, potassium clavulanate, and BRL 42715 but not EDTA. This study demonstrated that X. maltophilia produces more than just the L1 and L2 beta-lactamases.

ARI 1: beta-lactamase-mediated imipenem resistance in Acinetobacter baumannii.

A strain of Acinetobacter baumannii 6B92 isolated from the blood culture of a patient at the Edinburgh Royal Infirmary i 1985 was found to be resistant to imipenem, all classes of cephalosporins and penicillins. Extraction of the soluble proteins of the cell and isoelectric focusing revealed the presence of two beta-lactamases: a chromosomal cephalosporinase of high pI (> pI 9.0) and a novel beta-lactomase of pI 6.65 named ARI 1 (Acinetobacter resistant to imipenem). Despite the fact that original clinical isolate could be 'cured' of its resistance to imipenem and penicillins by growing in the presence of ethidium bromide with the concurrent loss of the ARI 1 enzymes, no resistance plasmid was visualised or transferred. The ARI 1 beta-lactamase hydrolysed penicillin, ampicillin and cephaloridine slowly during enzyme assay but inactivation of imipenem could only be demonstrated by microbiological means. The molecular size of the ARI 1 enzyme was 23 kDa and it was not inhibited by EDTA, p-CMB, or clavulanate.

The incidences of resistance to cephalosporins and fluorinated 4-quinolones in similar strains isolated in Glasgow and Edinburgh.

Bacterial sensitivity to cefuroxime, ceftazidime, cefotaxime, ciprofloxacin and ofloxacin was determined for 1386 urinary and bacteraemia isolates from Glasgow and Edinburgh to detemine the impact of these antibacterials on the development of resistance. The MIC(50) and MIC(90) values were determined for each species or genus. Cefuroxine was the least effective antibacterial drug and cefotaxime was the most potent cephalosporin, but it rarely matched the efficacy of the 4-quinolones. There was little difference in the sensitivities of Gram-negative bacteria from Edinburgh of Glasgow but Gram-positive bacteria isolated in Glasgow were usually more resistant. There has been no significant emergence of resistant Gram-negative bacteria even amongst the Pseudomonas spp.; however, the proportion of Gram-positive bacteria resistant to these drugs is higher in Scotland than elsewhere.

Antibiotic resistance in urinary bacteria isolated in central Scotland.

The levels of antibacterial amongst 991 strains responsible for significant bacteriuria, isolated in central Scotland at the end of 1990, have been determined by breakpoint sensitivity testing. Overall resistance to the commonly used antibacterials for UTI, trimethoprim and ampicillin was 23% and 36%, revealing that resistance to these agents in central Scotland had not significantly changed over the last ten years. High levels of ampicillin resistance have led to the widespread use of amoxicillin in combination with the beta-lactamase inhibitor clavulanic acid. The effectiveness of this approach was demonstrated by the fact that resistance among these urinary isolates to amoxicillin/clavulanic acid was only 6%. More detailed examination of Escherichia coli isolates, which were ampicillin-resistant, revealed that the addition of clavulanic acid restored sensitivity in 97.5% of the strains.

What standards should we use for the disinfection of large equipment?

There are no universal guidelines for cleaning and disinfecting large items of medical equipment. Washer/disinfectors provide one method of making medical equipment safe for staff and patients. Methods of evaluating the performance of such machines are discussed in an attempt to stimulate a much needed review of existing advice and guidelines on cleaning and disinfection. A plea is made for interested parties to agree practical standards for the cleaning and disinfection of medical equipment using washer/disinfectors.

Activity of clindamycin against Staphylococcus aureus and Staphylococcus epidermidis from four UK centres.

MICs of penicillin, methicillin, clindamycin, erythromycin, sodium fusidate and gentamicin were determined by an agar dilution method for 300 current isolates of Staphylococcus aureus and 100 of S. epidermidis, collected from four centres, and 38 stock strains of methicillin-resistant S. aureus (MRSA). All but one of the 300 current isolates of S. aureus were sensitive to clindamycin (MIC less than 0.5 mg/l), with an MIC90 of 0.12 mg/l. Of a total of 39 MRSA strains, 11 (28.2%) were resistant to clindamycin (MIC greater than 32 mg/l); all of these strains were also resistant to erythromycin. Ten of the 100 strains of S. epidermidis were resistant to clindamycin; they came from a reasonably equal geographical distribution and were also resistant to erythromycin. The results suggest that clindamycin might still be useful as a second-line agent for infections caused by S. aureus and S. epidermidis, although its activity against MRSA was limited to approximately two-thirds of the MRSA strains tested in this study.

Is antibiotic prophylaxis necessary for internal fixation of low-energy fractures?

A series of 54 patients who had low-energy, closed fractures requiring internal fixation were entered into a randomized prospective study comparing prophylactic antibiotics with no treatment. In five patients who did not have antibiotics a superficial wound infection or fever was recorded. In those who received antibiotics, no infection or fever was detected. However, there was no statistical difference between the two groups, and it is concluded that there is no need for prophylactic antibiotics when internally fixing low-energy fractures.

Antibiotic prophylaxis in proximal femoral fracture.

A prospective randomized double-blind trial was carried out to assess the effectiveness of one dose of prophylactic cefuroxime versus placebo in 502 patients who underwent surgery for a proximal femoral fracture. With an overall deep infection rate of 2.2 per cent there was no significant difference in the superficial or deep wound infection rate between the two groups. However, there was a significant reduction in the incidence of postoperative bacteriuria in the cefuroxime group. A study of three doses of cefuroxime versus placebo is now proposed.

Evaluation of the Draeger Anaesthetic Equipment Washing Machine (ANDA 9002).

An evaluation was made of an anaesthetic equipment washing machine. Our results largely substantiated the manufacturers claims. A clean, dry, disinfected load could be produced within 75 min. After minor modifications were made to the machine by the manufacturers, potential users were satisfied with its performance. We recommend consideration of this type of equipment for use in hospitals.