Wound infections acquired from a disperser of an unusual strain of Staphylococcus aureus

Antimicrobial efficacy of preoperative skin antisepsis and clonal relationship to postantiseptic skin-and-wound flora in patients undergoing clean orthopedic surgery

Nosocomial surgical site infections (SSI) are still important complications in surgery. The underlying mechanisms are not fully understood. The aim of this study was to elucidate the possible role of skin flora surviving preoperative antisepsis as a possible cause of SSI. We conducted a two-phase prospective clinical trial in patients undergoing clean orthopedic surgery at a university trauma center in northern Germany. Quantitative swab samples were taken from pre- and postantiseptic skin and, additionally, from the wound base, wound margin, and the suture of 137 patients. Seventy-four patients during phase I and 63 during phase II were investigated. Microbial growth, species spectrum, and antibiotic susceptibility were analyzed. In phase two, the clonal relationship of strains was additionally analyzed. 18.0 % of the swab samples were positive for bacterial growth in the wound base, 24.5 % in the margin, and 27.3 % in the suture. Only 65.5 % of patients showed a 100 % reduction of the skin flora after antisepsis. The microbial spectrum in all postantiseptic samples was dominated by coagulase-negative staphylococci (CoNS). Clonally related staphylococci were detected in ten patients [nine CoNS, one methicillin-susceptible Staphylococcus aureus (MSSA)]. Six of ten patients were suspected of having transmitted identical clones from skin flora into the wound. Ethanol-based antisepsis results in unexpected high levels of skin flora, which can be transmitted into the wound during surgery causing yet unexplained SSI. Keeping with the concept of zero tolerance, further studies are needed in order to understand the origin of this flora to allow further reduction of SSI.

Staphylococcal infections: a historical perspective

Staphylococcus aureus is an unusually successful and adaptive human pathogen that can cause epidemics of invasive disease despite its frequent carriage as a commensal. Over the past 100 years and more, S aureus has caused cycles of outbreaks in hospitals and the community and has developed resistance to every antibiotic used against it, yet the exact mechanisms leading to epidemics of virulent disease are not fully understood. Approaches such as bacterial interference have been effective in interrupting outbreaks, but to better prevent staphylococcal disease, we will need to be vigilant about environmental factors that facilitate its spread. Even more importantly, we need to understand more about the mechanisms that lead to its virulence and transmission. With such information, it may be possible to develop a vaccine that will prevent endemic and epidemic staphylococcal disease.

Source and route of methicillin-resistant Staphylococcus epidermidis transmitted to the surgical wound during cardio-thoracic surgery. Possibility of preventing wound contamination by use of special scrub suits

The objective of this study was to trace the source and route of transmission of methicillin-resistant Staphylococcus epidermidis (MRSE) in the surgical wound during cardio-thoracic surgery, and to investigate the possibility of reducing wound contamination by wearing special scrub suits. In total 65 elective operations for coronary artery bypass grafting (CABG) with or without concomitant valve replacement were investigated. All staff present in the operating room wore conventional scrub suits during 33 operations and special scrub suits during 32 operations. Samples were taken from the hands of the scrubbed team after surgical scrub but before putting on sterile gowns and gloves, and from patients' skin (incisional area of sternum and vein harvesting area of legs) after preoperative skin preparation with chlorhexidine gluconate. Air samples were taken during operations. Samples were also taken from the wound just before closure. Total counts of bacteria on sternal skin and from the wound (cfu/cm2) were calculated as well as total counts of bacteria in the air (cfu/m3). Strains of MRSE recovered from the different sampling sites were compared by pulsed field gel electrophoresis (PFGE). It was found that wearing special scrub suits did not reduce the number of air-samples where MRSE was found compared with conventional scrub suits. The risk factor most strongly associated with MRSE in the wound at the end of the operation was preoperative carriage of MRSE on sternal skin; RR 2.42 [95% CI 1.43-4.10], P= 0.021. By use of PFGE, it was possible to identify the probable source for four MRSE isolates recovered from the wound. In three cases the source was the patients own skin. Finding MRSE in air-samples, or on the hands of the scrubbed team, were not risk factors for the recovery of MRSE in the wound at the end of operation. In conclusion, with a total bacterial air count around 20 cfu/m3 and a low proportion of MRSE, the reduction of total air counts by use of tightly woven special scrub suits did not reduce air counts of MRSE or wound contamination with MRSE. The patients' sternal skin was the main source for wound contamination with MRSE

Dispersal of methicillin-resistant Staphylococcus epidermidis by staff in an operating suite for thoracic and cardiovascular surgery: relation to skin carriage and clothing

Methicillin-resistant Staphylococcus epidermidis (MRSE) is a common cause of deep sternal infections. The aim of the present investigation was to evaluate staff in an operating suite for thoracic and cardiovascular surgery as a possible source of MRSE and the possibility of reducing the amount of MRSE shed into the air by wearing tightly woven scrub suits. A second aim was to compare the results of dispersal obtained in a test chamber with those from an operating room. We studied carriage of MRSE in the nose and on different skin sites and made an experimental study of dispersal of MRSE during exercise in a test chamber and during operations, using two different types of scrub suits. Dispersal of MRSE [defined as > 1% of the total count of colony forming units (CFU) shed into the air] occurred in 25% of women and 43% of men. Nasal carriage was found among 28% in women and 33% in men. Among five skin-sampling sites, carriage of MRSE was most frequent on the cheek (50%) and in the axilla (24%) and least frequent in the perineum (5%). Dispersal of MRSE was however more strongly associated with carriage in the perineum (P = 0.097) than on the cheek (P = 0.5) and in the axilla (P = 0.21). With regard to shedding of bacteria into the air, there was a significant difference in favour of the tightly woven clothes regarding total counts of CFU both in the test chamber (P = 0.02) and the operating theatre (P = 0.002). Regarding MRSE, no such difference was found. We found there were too many dispersers of MRSE among operating department staff to exclude them from work. Although tightly woven scrub suits significantly reduced the amount of bacteria shed into the air, the amount of MRSE was not significantly reduced. Full-scale experiments in operating rooms are not needed when evaluating the protective capacity of different scrub suits as results from a test chamber give conclusive information.

Importance of air quality and related factors in the prevention of infection in orthopaedic implant surgery

Small numbers of organisms can cause orthopaedic implant infections, which give rise to a considerable degree of morbidity and also mortality. The periprosthetic infection rates have been shown to correlate with the number of airborne bacteria within 30 cm of the wound. This is influenced by factors such as the number of operating theatre personnel, their clothing and the type of ventilation system used. Guidance on routine bacteriological monitoring of ultraclean air theatres, based on the Department of Health document Health Technical Memorandum 2025, is discussed. Factors important in minimizing the number of postoperative implant infections such as the use of ultraclean air, ultraviolet radiation, different types of surgical clothing, prophylactic antibiotics and host-related factors are also discussed. The importance of proper scientific investigation into the effectiveness of practical preventative measures in the operating room is emphasized.

Flucloxacillin in the treatment of atopic dermatitis

Although colonization of atopic dermatitis by Staphylococcus aureus is universal and bacterial infection is common, it is not known whether antibiotic therapy is helpful in eczematous children who do not have any signs suggestive of bacterial infection. Fifty children aged 1-16 years with atopic dermatitis took part in a randomized double-blind placebo-controlled study of 4 weeks treatment with oral flucloxacillin, with an 8-week follow-up period. The change in the mean of the log10 of the counts/cm2 of S. aureus after 4 weeks of treatment was significantly different for patients receiving treatment, compared with the change for those receiving the placebo (P = 0.008). However, the difference in the change at 14 days after stopping treatment was not significant (P = 0.32). Methicillin-resistant strains of S. aureus were cultured from five children during or after treatment. Flucloxacillin did not improve the symptoms or clinical appearance of atopic dermatitis and only temporarily changed skin colonization by S. aureus.

Wound infections after surgery in a modern operating suite: clinical, bacteriological and epidemiological findings

A prospective study of 2983 operations in general and orthopaedic surgery during 3 years performed in four operating theatres in a modern operating suite was carried out in order to evaluate the importance of airborne infection. Weekly nose-and-throat samples were taken from the surgical staff and pre-operative samples were taken from the nose, throat, skin and perineum of the patients. The air contamination was followed by using settle plates, which showed low mean counts of total bacteria of between 9 and 15 c.f.u./m(2)/min, with mean counts of Staph. aureus of between 0.03 and 0.06 c.f.u./m(2)/min. No correlation was found between the total number of bacteria and the incidence of post-operative infections or between the amount of Staph. aureus in the air and post-operative Staph. aureus infections. It was concluded that further increases in ventilation could, at best, only marginally affect the incidence of post-operative infection.The post-operative wound-infection rate was 9.0%. In various types of surgery, the infection rates varied from 5.3% in clean operations to 47.6% in dirty surgery. About one third of the infections were classified as moderate or severe.Adverse patient factors, such as immunodeficiency, steroid treatment, intensive care, etc., increased the rate to 15.0%; in ;normal' patients it was 3.8%.Among the bacteria isolated, gram-negative bacilli (31% of wounds), often together with other bacteria, and Staph. aureus (28%) predominated, but in 25% no specimens were taken.Of 76 post-operative Staph. aureus infections, 32 were caused by the patients' own strains, and of the remaining 44 infections, 22, or 8% of all infections, could be traced to strains present in the air and/or the respiratory tracts of staff during the operation.The length of pre-operative hospital stay had no influence on the carrier rate of Staph. aureus in patients. The incidence of post-operative wound infection was significantly higher in patients carrying Staph. aureus and was even higher if these bacteria were found on the skin.Patients with wound infections stayed, on an average, 15 days longer than patients without infections. In serious infections the increase in duration of stay was > 20 days. Although infections were commoner in older patients, the average additional hospital stay of infected patients did not increase with age. If the post-operative infections studied in a concurrent retrospective study are taken into account more than 12 000 bed-days were due to post-surgical wound infections in the period studied or, in other words, some 12 beds (corresponding to 5.5% of the total) were always occupied by infected patients.

Genetic basis, epidemiology, and future significance of antibiotic resistance in Staphylococcus aureus: a review

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Isolation for the control of infection in skin wards

An isolation policy in a hospital for skin diseases is reported. Patients carrying penicillin- and tetracycline-resistant organisms were to be isolated in single rooms, though barrier nursing was not practised. The policy failed because the single beds rapidly became blocked with long-stay patients and because even in a single-bed unit patients acquired staphylococci within 3-7 days of admission. Patients with skin diseases often do not feel ;ill' and resent isolation.

Stability of neomycin resistance in Staphylococcus aureus

A strain of Staphylococcus aureus isolated from the skin of a subject with eczema showed a loss in resistance to neomycin and tetracycline after treatment with neomycin was stopped. Seven out of 22 strains of neomycin-resistant Staph. aureus showed a loss in resistance to neomycin and streptomycin after storage in nutrient broth for 14 days at room temperature, and it seems probable that resistance in these unstable strains was controlled by extrachromosomal elements or plasmids. Strains of phage types 84/85 and 29/77 and related types were frequently isolated in general hospital wards and showed no loss in resistance on similar storage in nutrient broth. Five of the neomycin-unstable strains were isolated from patients with eczematous lesions. Multiple-resistant and antibiotic-sensitive strains of Staph. aureus of similar phage type were isolated from patients in a ward for patients with skin disease, and the possibility of transfer of resistance in vivo is discussed.

Ward floors and other surfaces as reservoirs of hospital infection

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Severe outbreak of surgical sepsis due to Staphylococcus aureus of unusual type and origin

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