Biomedical subjects
S J Dancer
Publications and source records attributed to S J Dancer.
Antibiotic use is associated with resistance of environmental organisms in a teaching hospital.
An intensive care unit (ICU), acute stroke unit (ASU) and medical day bed unit (MDBU) underwent a standardized four-month environmental screening programme. The aim was to examine environmental organisms from these wards and compare bacterial resistances in association with antimicrobial usage. Hand-touch and other sites were screened using commercial dip-slides, and staff were asked to provide fingertip cultures. Patient blood isolates were retained throughout the study. Organisms were quantitatively and qualitatively assessed including antimicrobial susceptibility testing. Antibiotic consumption data in defined daily doses/1000 patient-days were obtained for each unit for the previous year. Two hundred and seventy-six staphylococci and 67 Gram-negative bacilli were recovered. Antibiotic resistance was significantly associated with individual wards for staphylococci (P<0.0001) and coliforms (P=0.04), and trends were also demonstrated for other Gram-negative organisms (P=0.06) despite fewer numbers. Antibiotic consumption on the ICU was six-fold higher than on the ASU and MDBU. Associations were found between consumption of selected antibiotic groups and corresponding resistances among staphylococci and Gram-negative bacilli. Antibacterial resistance was the only significant difference between environmental bacteria from different wards, and appeared to reflect prescribing pressure. Visual inspection of a ward may not provide a reliable guide regarding the presence of multi-resistant organisms in the hospital environment or the potential risk of infection. These findings have implications for local antibiotic policies, infection control and cleaning schedules.
MRSA--the storm clouds gather.
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How do we assess hospital cleaning? A proposal for microbiological standards for surface hygiene in hospitals.
Increasing numbers of hospital-acquired infections have generated much attention over the last decade. The public has linked the so-called 'superbugs' with their experience of dirty hospitals, but the precise role of cleaning in the control of these organisms in unknown. Hence the importance of a clean environment is likely to remain speculative unless it becomes an evidence-based science. This proposal is a call for bacteriological standards with which to assess clinical surface hygiene in hospitals, based on those used by the food industry. The first standard concerns any finding of a specific 'indicator' organism, the presence of which suggests a requirement for increased cleaning. Indicators would include Staphylococcus aureus, including methicillin-resistant S. aureus, Clostridium difficile, vancomycin-resistant enterococci and various Gram-negative bacilli. The second standard concerns a quantitative aerobic colony count of <5 cfu/cm(2) on frequent hand touch surfaces in hospitals. The principle relates to modern risk management systems such as HACCP, and reflects the fact that pathogens of concern are widespread. Further work is required to evaluate and refine these standards and define the infection risk from the hospital environment.
Oral streptogramins in the management of patients with methicillin-resistant Staphylococcus aureus (MRSA) infections.
OBJECTIVES: Chronic methicillin-resistant Staphylococcus aureus (MRSA) infections in debilitated patients are difficult to treat. We studied the clinical efficacy and safety of an oral streptogramin, pristinamycin, for these patients. PATIENTS AND METHODS: Patients were admitted consecutively to receive pristinamycin, usually with doxycycline, for 7-21 days. Fifty-six patients (average age 75 years) from hospital and community were treated for skin, soft tissue, chest and other infections. RESULTS: The overall clinical response rate was 39 of 53 patients (74%; 95% CI: 60%, 85%) cured or substantially improved, from 53 of 56 (95%) patients clinically and 49 of 56 (87.5%) patients bacteriologically evaluable. Toxic effects comprised gastrointestinal disturbances in eight patients (14%) and one (2%) possible skin rash. CONCLUSION: This study suggests that oral streptogramins may be useful in the management of debilitated patients with MRSA infections.
Bacillus cereus cellulitis from contaminated heroin.
Concern exists over recent unexplained deaths among intravenous drug users. This report describes a patient with crepitant cellulitis who was admitted complaining of severe pain in the right forearm. Ultrasonography demonstrated gas in the tissues and he was referred for early surgical debridement of the arm. He was treated with intravenous benzyl penicillin, gentamicin and metronidazole and made a full recovery. Aspirate samples grew Bacillus cereus, morphologically similar to the isolate obtained from a sample of the patient's own heroin. Antibiogram and API 50CHB profiles were also similar. Further typing included 'H' flagellar serotyping, which found both blood and heroin strains to be non-typable, and amplified fragment polymorphism analysis, which showed that the strains were indistinguishable. Genotyping of two selected genes from B. cereus confirmed almost certain identity between the two strains. This case illustrates the potential virulence of B. cereus when inoculated into tissues, and to our knowledge, is the first report to demonstrate a conclusive microbiological link between contaminated heroin and serious sepsis in a drug user due to B. cereus.
The problem with cephalosporins.
The cephalosporin antibiotics have become a major part of the antibiotic formulary for hospitals in affluent countries. They are prescribed for a wide variety of infections every day. Their undoubted popularity relies upon lesser allergenic and toxicity risks as well as a broad spectrum of activity. It is the latter feature, however, that encourages the selection of microorganisms that are resistant to these agents. There are long-term implications for the treatment and control of this heterogeneous group of superinfections. When clinicians evaluate a septic patient, it is understandable that they choose empirical therapy with a cephalosporin whilst awaiting microbiology and other tests, since bacterial identification and antimicrobial testing still usually require 24-48 h. The broad-spectrum capability of these drugs, however, encourages rapid overgrowth of some microorganisms that are neither eliminated nor inhibited by therapy. These organisms not only have pathogenic potential, they may also be multiply resistant to antibiotics. This review discusses the evidence that cephalosporin usage is the most important factor in the selection and propagation of microorganisms such as Clostridium difficile, methicillin-resistant Staphylococcus aureus, penicillin-resistant pneumococci, multiply resistant coliforms and vancomycin-resistant enterococci, the continuing increase of which threatens the future of antimicrobial therapy.
Keeping MRSA out of a district general hospital.
This study describes a three-year audit of methicillin-resistant Staphylococcus aureus (NIRSA) in a district general hospital and surrounding community. Despite a continuing increase in new cases of MRSA both nationally and locally, and the transfer of patients with MRSA from outside, the hospital remains free from endemic MRSA, albeit with occasional sporadic cases. This is attributed to the presence of a Control of Infection team who have introduced and implemented various policies to control MRSA. These include prompt screening of hospital transfers, an effective topical regimen, attention to environmental cleaning, treatment for established infection, tailored protocol for colonized urinary catheters and an educational programme for staff. Some of these policies have been extended into the community. This report also presents data from 172 cases of MRSA, including carriage rate, infection site, antibiogram, phage-typing, treatment and/or clearance outcome and preliminary evaluation of pathogenicity. A questionnaire has been formulated to assess colonization vs infection. Future strategies will be required if the status quo is to be maintained.
Swinging back the MRSA pendulum?
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Mopping up hospital infection.
Hospital cleaning is a neglected component of infection control. In the UK, financial constraints have forced managers to re-evaluate domestic services and general cleaning has been reduced to the bare minimum. Services have been contracted out in some hospitals, which has further lowered standards of hygiene. Control of infection personnel believe that cleaning is important in preventing hospital-acquired infections but they do not manage domestic budgets and have failed to stop their erosion. It is difficult to defend high levels of hygiene when there is little scientific evidence to support cleaning practices. This review examines the common micro-organisms associated with hospital-acquired infection and their ability to survive in the hospital environment. It also describes studies which suggest that comprehensive cleaning disrupts the chain of infection between these organisms and patients. It is likely that restoring hygienic standards in hospitals would be a cost-effective method of controlling hospital-acquired infection. Furthermore, good cleaning is achievable whereas the enforcement of hand washing and good antibiotic prescribing are not.
Isolation and characterization of coliforms from glacial ice and water in Canada's High Arctic.
Ellesmere Island is the northern most member of the Canadian Arctic Archipelago with over one-third of the land mass covered by ice. A joint services expedition to the island's Blue Mountains offered a unique opportunity for microbiological studies of resident bacteria in an environment uninhabited by man. Over 100 samples of water and ice were collected from stream, lake and glacier and the filtrate cultured under canvas. Bacterial growth was harvested onto swabs for transport back to the UK and 50 coliforms chosen at random for identification and antibiotic susceptibility testing. Most of the glacial strains were capsulated, pigmented and some over 2000 years old. Genera such as Serratia, Enterobacter, Klebsiella and Yersinia were found; speciation was inconclusive and some organisms remain unidentified. Ampicillin resistance was evident in 80% of water isolates as opposed to 30% of the glacial organisms, but the isolates were generally exquisitely susceptible to antibiotics. The facility for ampicillin resistance did not appear to be transferable. Plasmid DNA was found in 33% of the glacial organisms and over 50% of the water isolates. Similar profiles were identified within and apparently between species and required plasmid restriction analysis to help establish identity. Plasmid-free Serratia spp. were subjected to genomic fingerprinting. Indistinguishable patterns were found within sets of isolates both widely spaced by distance and collection date and it was postulated that coliforms able to survive an Arctic environment had spread extensively throughout the expedition area. In conclusion, this study contributes towards knowledge of naturally occurring antibiotic resistance, confirms the presence of plasmids and genotypic data provided evidence that potentially ancient organisms from glaciers can be cultured from water samples significantly distant.
Creative infection control--raising awareness of infection control policies.
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Nasal, axillary, and perineal carriage of Staphylococcus aureus among women: identification of strains producing epidermolytic toxin.
Following two outbreaks of staphylococcal scalded skin syndrome in a maternity unit, 500 pregnant women attending an antenatal clinic were screened for carriage of epidermolytic toxin producing Staphylococcus aureus. Nasal, axillary, and perineal swabs were collected from women whose gestational ages ranged from 12-40 weeks. Isolates of S aureus were purified, phage typed, and tested for methicillin sensitivity and production of epidermolytic toxin. The results showed that 164 (33%) women carried S aureus; of these, 100 (61%) were from the nose and three (2%) from axillae, but 41 (25%) strains were isolated from the perineum alone. Screening for nasal carriage alone will therefore miss 25% of carriers. More than one strain of S aureus was identified in seven of 20 women with multiple site carriage. Three (2%) methicillin resistant strains were isolated during the survey, and five (3%) isolates produced epidermolytic toxin. Phage typing identified 63 (34%) strains as non-typable, but 50% of isolates typed either groups I, II or III, and a further 10% represented varying combinations of these and other phage groups. These results provide baseline information on S aureus in the community, and identification of methicillin resistant and toxin producing strains shows a reservoir of outbreak potential which could become relevant on hospital admission of such a carrier.
The epidermolytic toxins are serine proteases.
Certain strains of Staphylococcus aureus usually belonging to phage group II produce epidermolytic toxins (ETA and ETB) which cause intraepidermal splitting in mice, neonates and occasionally adults. Amino acid sequences of ETA and ETB have been reported but the mechanism of epidermolysis remains unknown. A search of the NBRF-PIR computer database showed the toxins to have significant sequence similarity with staphylococcal V8 protease and that the catalytic triad of V8 protease is present in ETA and ETB. Comparison of ETA, ETB and V8 protease with other members of the trypsin-like serine protease family revealed little homology save for the immediate vicinity of the residues constituting the catalytic triad. The toxins, therefore, exhibit a distant relationship to mammalian serine proteases. A potential Ca2(+)-binding loop was identified in ETA (but not ETB) on the basis of sequence similarity with the second calcium-binding loop of rat intestinal calcium-binding protein. Epidermolysis produced by ETA in the mouse bioassay was shown to be inhibited by the presence of EDTA consistent with a Ca2(+)-dependent mechanism.
An outbreak of pemphigus neonatorum.
During the summer of 1987, an epidemic of pemphigus neonatorum took place at Guy's Hospital. It involved more than 80 neonates in the maternity unit. Swabs from the umbilical stumps of the babies and from the noses of several attending midwives yielded Staphylococcus aureus of phage-type Group II 3A/3C. Despite an extensive disinfection policy, which included identification and treatment of carriers, the outbreak persisted for 3 months. Final resolution came only after detailed epidemiological research revealed those midwives most likely to be involved. After these had been singled out for further treatment, the outbreak ended. The epidemic strains were later subjected to reverse phage-typing, plasmid profiling and in vivo testing for production of epidermolytic toxin in order to confirm true carriers and cases. Retrospective analysis identified those persons most likely to have been responsible for propagation of the epidemic strain. The exact course of the outbreak was then clarified.
Outbreak of staphylococcal scalded skin syndrome among neonates.
Over a period of 2 months, 12 babies born in the maternity unit at Guy's Hospital developed staphylococcal scalded skin syndrome in two distinct outbreaks. Staphylococci isolated from the babies, together with those from the mothers and attending medical staff were phage-typed. All isolates from the babies were of type 3A/3C. During the first outbreak only one carrier of the epidemic strain (a paediatrician) was found but a further 12 persons were identified as possible carriers during the second outbreak. In order to confirm the link between outbreaks, all phage group II isolates were subjected to reverse phage-typing, testing for metal-ion resistance, plasmid profiling and in-vivo testing for production of epidermolytic toxin. It was shown that the same epidemic strain of toxin-producing Staphylococcus aureus was responsible for both outbreaks. The affected neonates responded rapidly to a short course of intravenous flucloxacillin. The outbreak ceased after appropriate treatment of all carriers and the implementation of an extensive disinfection policy within the maternity unit.