Biomedical subjects
Publications and source records attributed to D S Reeves.
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Occasional staff or visitors to operating theatres are usually requested to don over-shoes as this is perceived to reduce bacterial floor colony counts. However, this entails some expense and considerable inconvenience. Using disposable surface contact plates floor bacterial counts were measured four times a day at five different sites during the 5 normal working days of one 2-week period in a general operating theatre when over-shoes were worn and one 2-week period when over-shoes were not worn. There was no significant difference in the mean bacterial floor colony counts between the two periods according to sampling times or sites. As in Intensive Therapy units, over-shoes should no longer be used in general operating theatres.
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The wearing of disposable head-gear in operating theatres is currently recommended for scrubbed and non-scrubbed staff. However, there is little evidence of its effectiveness as an infection control measure in casual or non-scrubbed theatre staff. The effect of head-gear on bacterial air counts was studied, using six volunteers, in a sealed room, with and without ventilation. Using a Casella slit sampler and a SAS Air Sampler, air counts ranged from 0.08 to greater than 2.9 colony forming units (cfu) m-3. The wearing of head-gear was not associated with a reduction in air counts but counts were lower with ventilation. We recommend that non-scrubbed staff no longer wear head-gear as effective ventilation probably counteracts any possible increased bacterial shedding. Scrubbed staff should continue to wear disposable head-gear because of their proximity to the operative field.
About 2.3% (16/700) of faecal specimens from renal transplant recipients and patients having home haemodialysis as well as patients attending their general practitioners with symptoms of gastroenteritis yielded Listeria species 40% of positive faeces contained more than one Listeria species or serovar. The proportion of positive specimens was similar in all three patient groups. Listeria were isolated from 5.6% (10/177) of renal transplant recipients on one or more occasions over the period of a year. The commonest species was L. monocytogenes and type 4b the commonest serovar. Carriage was more common in July and August than other times of year, and less than 28 weeks in duration. In renal transplant recipients carriage was positively related to treatment with ranitidine, consumption of more than three types of cheese in the previous 20 months, and consumption of English cheddar cheese more than once per week.
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.
Eleven elderly patients (mean age 83 years; range 75-90) with microbiologically proven urinary tract infections were given 400 mg lomefloxacin as a single daily dose for up to seven days. On the first and final day of treatment blood was taken at timed intervals and drug concentration-time curves plotted. Blood was also taken immediately before each of the other doses for assay of pre-dose concentrations. The mean (+/- S.D.) peak serum concentration of lomefloxacin on the first day was 4.8 mg/l (+/- 1.5) observed at a mean of 156 min (+/- 88) and on the final day was 6.3 mg/l (+/- 2.5) at a mean of 119 min (+/- 68). The mean serum half-life on the first day was 10.0 h (+/- 2.8) and on the final day 10.3 h (+/- 2.5). The daily pre-dose serum concentrations of lomefloxacin showed no accumulation of the drug. No serious adverse events were reported and all patients were cured although two had persistent pyuria. It is suggested that a once daily dose of 400 mg lomefloxacin is suitable for the elderly and that no dosage modification is needed in this patient group.
Five hundred and twenty two clinical urine specimens submitted for routine microbiological examination were tested in parallel by conventional microscopy and culture and for lipopolysaccharide antibodies by an enzyme linked immunoabsorbent assay (ELISA) to assess the ELISA as a screen for urinary tract infection. When the ELISA alone was compared with routine methods the specificity sensitivity, and predictive value of positive and negative tests was 73.2%, 75.7%, 51.1% and 38.5%. For ELISA with microscopy the same variables were 71.1%, 82.2%, and 92.4% and 94.7%, respectively. The ELISA absorbency increased with increasing bacterial numbers, but results varied widely. Only 65.4% of urines which contained greater than or equal to 10(5) bacteria/ml were positive by ELISA; 36.8% of urines with less than 10(3) bacteria/ml were positive by ELISA; 100% of greater than or equal to 10(5) bacteria/ml cultures of Pseudomonas sp (n = 4), Staphylococcus aureus (n = 3), and Streptococcus faecalis (n = 2) were positive by ELISA but only 71.4% of Proteus sp (n = 7), 61.4% coliforms (n = 70), and 25% of coagulase negative staphylococci (n = 4). It is concluded that further development is required before the ELISA can be used for routine screening for urinary tract infection.
To determine the turn-around time in a microbiology laboratory a survey form was designed to collect data on the origin and type of specimen and the dates and times when (i) the sample was taken; (ii) the specimen was received in the laboratory; (iii) the report was signed by the microbiologist; (iv) the report was sorted by the laboratory clerical staff; and (v) the final report was received on the ward. The cumulative time from sampling to a result arriving on the ward was 51.5 (SD 28.6) hours. The survey is a simple method of determining turn-around time and high-lighted minor deficiencies in the service which were easily rectified.
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Single dose fosfomycin trometamol (3 g) was used to treat 20 hospitalised patients with UTI. Tolerance was good or excellent in 19/20 patients; a satisfactory bacteriological outcome was recorded in 11/17 of patients with sensitive organisms and a satisfactory clinical outcome was noted in 12/16 symptomatic individuals.
The MICs and MBCs of 21 antimicrobial agents were determined for 103 strains of Listeria monocytogenes isolated in the UK and 27 strains of other Listeria species. Ampicillin, penicillin, azlocillin, imipenem, gentamicin, netilmicin, amikacin, erythromycin, rifampicin, trimethoprim, clindamycin and vancomycin had good activity, while cephalothin, chloramphenicol, ciprofloxacin and ofloxacin were less active, and cefuroxime, enoxacin, norfloxacin and fosfomycin were the least active. Tetracycline had good activity against many strains, but the MIC was high for some. Unlike the other Listeria species tested, Listeria ivanovii was susceptible to fosfomycin. Inoculum size and media employed were shown to affect the MBC, tryptose phosphate broth yielding higher MBCs than Mueller-Hinton or Isosensitest broths.
Five patients with exacerbation of chronic bronchitis received as a single iv injection 500 mg of ampicillin and 500 mg of amoxycillin. Blood and sputum samples were collected at timed intervals following dosing and the concentrations of the two antibiotics present in the samples were determined by HPLC analysis. No statistically significant differences were observed between the serum concentrations of ampicillin and amoxycillin, and the pharmacokinetics of the two drugs were almost identical, with half lives of 93 min (amoxycillin) and 103 min (ampicillin). Sputum amoxycillin concentrations were significantly higher (Student's paired t-test; P less than 0.001) than those of ampicillin, with mean levels two hours after dosing of 2.9 mg/l (range 1.9-4.0) for amoxycillin and 1.4 mg/l (range 0.8-2.4) for ampicillin.
In-vitro antimicrobial synergy against Listeria monocytogenes was assessed using nine combinations in chequerboard (bacteriostatic) tests and time-kill (bactericidal) studies. Ampicillin/gentamicin and trimethoprim/sulphamethoxazole were the most synergistic combinations in bacteristatic tests, whereas gentamicin with ampicillin, trimethoprim or vancomycin and trimethoprim/sulphamethoxazole were the most synergistic in bactericidal tests. Gentamicin-containing combinations were most effective at killing L. monocytogenes and those containing rifampicin least effective.
Six patients with newly diagnosed haematological malignancy were treated with ciprofloxacin 500 mg orally, as chemoprophylaxis during neutropenia. The mean serum ciprofloxacin concentrations, measured 1, 2, 3 and 4 h after dosage were reduced for up to ten days after the start of chemotherapy. The mean maximum serum concentration and AUC 0-4 h were reduced from 3.7 (95% confidence limits, 2.3-5.1) mg/l and 10.7 (6.2-15.2) mg/l.h pre-chemotherapy to 2.0 (1.4-2.6) mg/l and 5.7 (4.4-7.0) mg/l.h, 13 days after chemotherapy. Absorption of ciprofloxacin is reduced after cytotoxic chemotherapy, and this may have implications for the use of oral ciprofloxacin in this group of patients.
Five patients undergoing routine total knee replacement received standard antibiotic prophylaxis of 1000 mg of iv cefamandole and also regional administration of 750 mg of cefuroxime. Regional dosing was carried out at the start of the operation, following the application of a mid-thigh tourniquet, by administration into a foot vein. Samples of bone and fat were collected during the operation and assayed for cefuroxime and cefamandole by HPLC analysis. The mean cefuroxime bone (133.1 mg/l) and fat (88.4 mg/l) levels following regional administration were significantly higher (P less than 0.001) than the mean cefamandole bone (9.1 mg/l) and fat (9.8 mg/l) levels following systemic dosing. The possibility of administration of prophylaxis by the regional route is suggested.
A total of 1834 non-copy, general practice or outpatient isolates were collected by 20 hospital laboratories within the British Isles, and identified and tested for susceptibility to nine antimicrobial agents available by oral administration at one centre. Against Enterobacteriaceae cefpodoxime was the most active beta-lactam agent tested, the MIC90s being: for Escherichia coli 1.0 mg/l, for Proteus mirabilis 1.0 mg/l, for Citrobacter spp. 2.0 mg/l, and for Enterobacter spp., Serratia spp., Morganella spp. and Klebsiella spp. 16-64 mg/l. Cefpodoxime also showed a certain amount of activity against staphylococci and high activity against streptococci, the MIC90s being for Staphylococcus aureus 2 mg/l, for coagulase negative staphylococci 8 mg/l, for Streptococcus pyogenes 0.015 mg/l, for Str. pneumoniae 0.06 mg/l and for Str. agalactiae 0.5 mg/l.