Biomedical subjects
R C Slack
Publications and source records attributed to R C Slack.
The autumn peak in campylobacter gastro-enteritis. Are the risk factors the same for travel- and UK-acquired campylobacter infections?
BACKGROUND: In the autumn of 1992 there was an excess of campylobacter cases in Nottingham compared with the national average. No relative increase was seen for salmonella infections. METHODS: A case-control study with a postal questionnaire was carried out to determine exposure to possible risk factors. The patients were 282 laboratory confirmed cases of campylobacter and 318 culture negative controls who had submitted a faeces specimen. All patients were aged 18 or older. The main outcome measures were relative risks for campylobacter infection compared with controls with a negative faeces culture. RESULTS: Twenty-five per cent of cases were associated with foreign travel. Eating chicken and handling raw poultry were the main risk factors for UK-acquired infections. The number of cases with a history of contact with puppies or drinking milk that was either unpasteurized or from bottles with bird-damaged tops was small. CONCLUSION: Eating chicken and handling raw poultry are the main risk factors for campylobacter infections. Contact with puppies or drinking potentially infected milk can explain only a small percentage of campylobacter infections. Risk factors for infection acquired abroad follow a different pattern compared with UK-acquired cases.
Recent treatment with H2 antagonists and antibiotics and gastric surgery as risk factors for Salmonella infection.
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The cost of postoperative wound infections.
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Outbreak of Legionnaires' disease at University Hospital, Nottingham. Epidemiology, microbiology and control.
Twelve patients in a large teaching hospital contracted Legionnaires' disease over a period of 11 months. The source was a domestic hot water system in one of the hospital blocks, which was run at a temperature of 43 degrees C. Five different subtypes of Legionella pneumophila serogroup 1 have been isolated from water in different parts of the hospital, over a period of time. Only one subtype, Benidorm RFLP 14, was implicated in disease. Circumstantial evidence suggested that the outbreak may have been due to recent colonization of the hot water system with a virulent strain of Legionella pneumophila. The outbreak was controlled by raising the hot water temperature to 60 degrees C, but careful surveillance uncovered two further cases in the following 30 months. Persistent low numbers of Legionella pneumophila were isolated from the domestic hot water of wards where Legionnaires' disease had been contracted, until an electrolytic unit was installed releasing silver and copper ions into this supply.
Definition of urinary tract infection and assessment of efficacy in drug trials--a laboratory perspective.
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Development and design of a novel in vivo chamber implant for the analysis of microbial virulence and assessment of antimicrobial therapy.
An accurate reflection of the pathogenicity of microorganisms and the therapeutic effects of antimicrobial agents on their growth necessitates testing within an in vivo environment. We have developed a novel diffusion chamber, incorporating two 0.22 microns membrane filters, for the growth of in vivo organisms. The chamber, which is implanted intraperitoneally into the rat, has an external sampling portal. This portal allows multiple and sequential sampling of the microbial inoculum without killing the rat, thus significantly reducing the total number of animals used in such studies. In addition, the chamber is superior to other reported implants since it is well tolerated, reusable, easily constructed and can be used within two days of implantation. Staphylococcus epidermidis and a toxic shock syndrome toxin-1 (TSST-1) producing strain of S. aureus have been successfully grown within in vivo chambers, with 10(8)-10(9) organisms per millilitre being recovered within 48 h. Scanning electron microscopy revealed clusters of staphylococci and fibrous material adhering to the inner surface of the filters, with numerous phagocytic cells attached to the outer side. Western immunoblotting indicated that higher levels of TSST-1 were produced by S. aureus grown in vivo as opposed to cells grown in vitro.
Streptococcus pyogenes vulvovaginitis in children in Nottingham.
Isolates of Streptococcus pyogenes from vaginal swabs of children with vulvovaginitis received at Nottingham Public Health Laboratory during 1986-9 were studied. A total of 159 isolates was made during the 4 years, increasing from 17 in 1986 to 64 in 1989 and accounting for 11% of all vaginal swabs received from children. The numbers of throat swabs yielding S. pyogenes also showed an increase from 974 in 1986 to 1519 in 1989. A winter peak of isolates was noted for both vaginal swabs and throat swabs. A total of 98 strains from vaginal swabs were serotyped: 22 different types were identified, 61% of which were the common types M4, M6, R28 and M12. Erythromycin sensitivity was done on 89 strains; 84% were highly sensitive (MIC less than 0.03 mg/l). There are no other reports of such large numbers in the literature; the reason for seeing this increase in Nottingham is unclear.
A comparative double-blind randomised study of single dose fosfomycin trometamol with trimethoprim in the treatment of urinary tract infections in general practice.
A double-blind, double-dummy trial comparing a single dose treatment with fosfomycin trometamol (FT, 3 g) versus trimethoprim (TMP, 200 mg) was carried out in women with uncomplicated urinary tract infections. From 51 clinically evaluable patients, 44 were bacteriologically assessable at the 6-week follow-up. The results were as follows in the FT group (n = 22): eradication in 17 (77.3%); recurrence in 2 (9%); reinfection in 2 (9%), and persistence in 1 (4.5%). For the TMP group (n = 22) the results were: eradication in 12 (54.5%); recurrence in 1 (4.5%); reinfection in 1 (4.5%), and persistence in 8 (33.3%). There were no significant adverse events reported with either agent.
Randomised study of prophylactic parenteral sulbactam/ampicillin and cephazolin in biliary surgery: significant benefit in jaundiced patients.
Two hundred consecutive patients undergoing biliary-tract surgery were entered into a randomized trial of prophylactic single dose cephazolin or sulbactam/ampicillin. There was no overall difference in the infection rates between the two antibiotic groups, but in the group of patients with jaundice there was an excess of wound infections in the cephazolin group compared to the sulbactam/ampicillin group (35% vs. 14%). We conclude that sulbactam/ampicillin is a satisfactory prophylactic agent for use in biliary-tract surgical sepsis, and that it may be superior to cephazolin in jaundiced patients.
A bacteriological survey of amputation wound sepsis.
A retrospective survey of 100 lower limb amputations performed for ischaemia were analysed to assess the influence of preoperative bacterial isolates and the use of prophylactic antibiotics on wound sepsis. Forty-eight per cent had previously undergone a vascular procedure to attempt limb salvage and 17% were diabetics. Benzylpenicillin was given preoperatively and continued for 5 days; diabetics received metronidazole in addition. A total of 51 isolates were obtained from 30 patients preoperatively; Staphylococcus aureus and Enterobacteriaceae each accounted for over 25%. Postoperatively, 74 isolates (20 multiple) were obtained with an overall sepsis rate of 40%. Those patients with a positive preoperative culture were significantly more likely to develop wound sepsis. There was no significant difference in wound sepsis rates for diabetics. In view of the range of organisms causing postoperative infection, we recommend prophylaxis with a broad spectrum antibiotic for amputations.
Do preoperative chlorhexidine baths reduce the risk of infection after vascular reconstruction?
Pathogenic organisms are frequently present on the skin of vascular patients and are a risk factor for postoperative infection. A randomised trial of preoperative antiseptic baths was performed in 64 high risk vascular patients to determine whether two chlorhexidine baths could reduce the incidence of postoperative sepsis. Although pathogenic organisms were isolated preoperatively in 35% of patients, the wound infection rate after chlorhexidine baths (26%) was greater, though not significantly, than after baths with non-medicated soap (11%). An alternative theory that infection arises via lymphatics in the limb was not confirmed when organisms could not be isolated from groin lymph nodes in a group of 35 patients. The case for preoperative antiseptic regimes in vascular surgery remains unproven.
Use of a non-radioactive hybridisation assay for direct detection of gram-negative bacteria carrying TEM beta-lactamase genes in infected urine.
DNA in infected urines from 81 patients with urinary tract infection was hybridised directly with a non-radioactive DNA probe specific for bacterial genes coding for TEM-type beta-lactamase. The results were assessed by means of a computerised image analysis system and compared with those obtained following isolation of the infecting organism, conventional sensitivity testing and isoelectric focusing (IEF) procedures for the detection of TEM-type beta-lactamase. Of the 27 ampicillin-resistant gram-negative organisms isolated in pure culture from the urines, 14 were shown by both hybridisation and IEF to carry a gene for TEM beta-lactamase production. Only four discordant results were obtained: three "false positive" direct hybridisation results, one due to urine pigmentation, and one, possibly, to a TEM beta-lactamase gene which was not being expressed, and one "false negative" result due to insufficient cell numbers in the urine. The system is capable of screening large numbers of samples and is applicable to any gene for which a suitable DNA probe is available.
Bacterial resistance to trimethoprim in geriatric medical wards.
Urinary tract infections (UTI) caused by organisms resistant to trimethoprim (TMP), as well as their faecal carriage were studied in two geriatric wards. TMP-resistant UTI was common (26 and 50% of admission and ward-acquired infections, respectively) and was associated with male sex, recurrent and transferred admissions and length of stay. There was a strong relationship between faecal carriage and isolation of TMP-resistant organisms from urine. Antimicrobial exposure was the major determinant of TMP-resistant faecal carriage.
Risk factors in vascular surgical sepsis.
The risk factors for sepsis after vascular surgery were studied in 100 consecutive patients with lower limb arterial ischaemia. Patients were randomised either to a short or long course of antibiotic prophylaxis with amoxycillin/clavulanic acid combination (Augmentin). Pathogenic organisms were isolated from the skin preoperatively in 39 (36%) cases, significantly more frequently in patients with ischaemic rest pain and skin necrosis (66%) than rest pain alone (21%) (P = 0.0004) or claudication/aneurysm (11%) (P = 0.0001). All but three organisms isolated (5%) were sensitive to amoxycillin/clavulanic acid. A wound infection occurred after 21 (19%) reconstructions, significantly more frequently both in patients suffering rest pain with skin necrosis (P = 0.001) and rest pain without skin necrosis (P = 0.04) compared with claudication/aneurysm. Sixteen of the 21 patients with a wound infection had at least one organism isolated from their skin preoperatively (P = 0.0001). Twelve patients (57%) had a similar organism isolated from the skin preoperatively and from the postoperative wound infection. Reducing the course of antibiotic prophylaxis from 5 days to 3 doses did not significantly increase the infection rate. The only other significant risk factor for sepsis was increasing age of the patient. Although prophylaxis is undisputed in patients having synthetic grafts, antibiotics may not be as important in the prevention of wound sepsis as had been thought. The role of antiseptic agents requires further evaluation.
Detection of TEM beta-lactamase genes by non-isotopic spot hybridisation.
A 998 bp fragment of plasmid pBR322, comprising part of the TEM-1 beta-lactamase gene, was labelled with biotin-11-dUTP for use as a DNA probe in a rapid non-isotopic spot hybridisation test. Diluted broth cultures of bacteria producing different beta-lactamases were filtered onto nitrocellulose and lysed in situ. Following pre-hybridisation treatment with proteinase K, hybridisation with the labelled probe was demonstrated using a commercially available streptavidine/polyalkaline phosphatase-based detection system. The probe was highly specific, reacting only with strains producing either the TEM-1 or structurally similar TEM-2 enzyme. An inoculum of 3-4 X 10(6) cells gave optimum positive discrimination. When 90 recent ampicillin-resistant strains of Escherichia coli isolated from patients with urinary tract infections were screened using the system, 72% gave a positive hybridisation signal.
Perioperative prophylaxis with sulbactam and ampicillin compared with metronidazole and cefotaxime in the prevention of wound infection in children undergoing appendectomy.
Sulbactam is a beta-lactamase inhibitor, which when administered with ampicillin, increases the latter agents antibacterial activity against beta-lactamase producing organisms. One hundred children between the ages of 5 and 14 undergoing emergency appendectomy were entered into a prospective randomized trial comparing sulbactam and ampicillin (SA) with metronidazole and cefotaxime (MC) as prophylaxis against postoperative wound infection. Patients in whom the appendix was perforated or gangrenous received a 72-hour course of antibiotics, others received a single dose only. The overall wound infection rate was 8% (14% in patients with perforation or gangrene and 4% in those without). There was no difference in infection rate between the two antibiotic groups; there were three wound infections and one subphrenic abscess in patients receiving SA and four wound infections in patients receiving MC. SA, therefore, appears to be a suitable antibiotic combination for use as prophylaxis in appendicitis in children.
Rapid detection of a specific trimethoprim resistance gene using a biotinylated DNA probe.
A DNA probe specific for the dihydrofolate reductase (DHFR) type I gene was labelled with biotin by the process of nick-translation and used to screen 83 independently-derived trimethoprim R plasmids from Enterobacteriaceae. Hybridization was detected using streptavidine and a biotin-conjugated alkaline phosphatase to generate an insoluble coloured precipitate following the addition of an appropriate dye. Sixty-eight plasmids (81.9%) hybridized with the probe for DHFR type I. The method could be adapted for use with any antibiotic resistance gene for which a suitable DNA probe is available and has none of the drawbacks associated with the use of radioactively-labelled DNA in hybridization techniques.