Staphylococcus aureus bacteriuria and surgical site infections by methicillin-resistant Staphylococcus aureus

In Vitro and In Vivo Activities of a Bi-Aryl Oxazolidinone, RBx 11760, against Gram-Positive Bacteria

RBx 11760, a bi-aryl oxazolidinone, was investigated for antibacterial activity against Gram-positive bacteria. The MIC₉₀s of RBx 11760 and linezolid against Staphylococcus aureus were 2 and 4 mg/liter, against Staphylococcus epidermidis were 0.5 and 2 mg/liter, and against Enterococcus were 1 and 4 mg/liter, respectively. Similarly, against Streptococcus pneumoniae the MIC₉₀s of RBx 11760 and linezolid were 0.5 and 2 mg/liter, respectively. In time-kill studies, RBx 11760, tedizolid, and linezolid exhibited bacteriostatic effect against all tested strains except S. pneumoniae RBx 11760 showed 2-log₁₀ kill at 4× MIC while tedizolid and linezolid showed 2-log₁₀ and 1.4-log₁₀ kill at 16× MIC, respectively, against methicillin-resistant S. aureus (MRSA) H-29. Against S. pneumoniae 5051, RBx 11760 showed bactericidal activity, with 4.6-log₁₀ kill at 4× MIC compared to 2.42-log₁₀ and 1.95-log₁₀ kill for tedizolid and linezolid, respectively, at 16× MIC. RBx 11760 showed postantibiotic effects (PAE) at 3 h at 4 mg/liter against MRSA H-29, and linezolid showed the same effect at 16 mg/liter. RBx 11760 inhibited biofilm production against methicillin-resistant S. epidermidis (MRSE) ATCC 35984 in a concentration-dependent manner. In a foreign-body model, linezolid and rifampin resulted in no advantage over stasis, while the same dose of RBx 11760 demonstrated a significant killing compared to the initial control against S. aureus (P < 0.05) and MRSE (P < 0.01). The difference in killing was statistically significant for the lower dose of RBx 11760 (P < 0.05) versus the higher dose of linezolid (P > 0.05 [not significant]) in a groin abscess model. In neutropenic mouse thigh infection, RBx 11760 showed stasis at 20 mg/kg of body weight, whereas tedizolid showed the same effect at 40 mg/kg. These data support RBx 11760 as a promising investigational candidate.

Perioperative Antimicrobial Prophylaxis in Urology: a Multi-Center Prospective Study

Since there are few published reports regarding the impact of urologic surgery on perioperative infections, an epidemiologic analysis was performed on data from 1,156 open or laparoscopic operations in urology collected by the 21 hospitals participating in this study between September 2002 and August 2003. Prophylactic antibiotics were administered intravenously according to our protocol designed on the basis of the invasiveness and contamination levels. The surgical site infection (SSI) rates following clean, clean-contaminated and contaminated surgery were 1.2%. 5.8% and 23.4%, respectively, while the remote infection (RI) rates were 3.5%. 7.1% and 35.9%, respectively. Methicillin-resistant Staphylococcus aureus (MRSA) was most frequently isolated from SSIs as well as RIs, whereas Enterococcus faecalis and Pseudomonas aeruginosa were more frequently discovered in RIs than in SSIs. Several risk factors for SSI and/or RI, such as older age, high ASA score, obesity, diabetes, preoperative chemotherapy, long operation time and much blood loss, were identified by univariate analysis.

[Incidence of nosocomial infection in open prostate surgery]

OBJECTIVES

To know the rate of nosocomial infections in open prostate surgery and to assess the application of pre-surgery preparation and preoperative antibiotic prophylaxis protocols at three public hospitals in the Autonomous Community of Madrid.

MATERIALS AND METHODS

Prospective observational and multicentre study, including all the patients operated on at the services monitored and admitted for more than 48 hours between 1 January and 31 December 2009. They were monitored from admittance until their discharge.

RESULTS

The rate of hospital infection observed was 3.38%. The most frequent infection was surgical localization, with an incidence rate of 2.77% (superficial=1.23%; deep=0.31%; organ-space=1.23%). The percentage of appropriate surgical prophylaxis, both in the indication and in the selection of antibiotics, initiation and duration, with respect to all those patients that received it, was 47.42%. According to the data obtained from their clinical records, the percentage of patients in which the pre-surgery preparation protocol was correctly complied with, was 92%.

CONCLUSIONS

The results obtained in this multicentre study can serve not only as a reference to other public hospitals, but they are also comparable to other international monitoring systems. Monitoring and controlling infections associated with healthcare must be a key aspect in Patient Care and Safety programmes.

Predictors of surgical site infection in dirty urological surgery

OBJECTIVES

Risk factors for surgical site infection (SSI) following urologic dirty operations have not been clearly identified. This study was conducted to describe incidence, potential risk factors and common causative pathogens of the SSI in such operations.

METHODS

Medical records of patients who had undergone simple nephrectomy or lumbotomy for suppurative renal infection at our institutions from 1999 to 2006 were retrospectively evaluated. The following data were retrieved: presence of SSI, demographic data, laboratory findings, comorbidities, microbiological data, type of renal suppuration, type of urological surgery and antibiotic regimen. Risk factors for SSI were evaluated using the multiple logistic regression model.

RESULTS

Sixty-five patients (mean age 55.6 +/- 13.1 years) were eligible for data analysis. In 20 of them (30.8%) a SSI was identified. The most common isolated pathogens were gram-negative bacteria. At univariate logistic regression analysis risk factors significantly associated with SSI included: presence of emphysematous infection, hypoalbuminemia, number of predisposing conditions, emergency operations, isolation of Enterobacteriaceae, positive pus culture. The use of trimethoprim/sulfamethoxazole was associated with a decreased risk for SSI. Multiple logistic model identified only the emergency operations and isolated Enterobacteriaceae as independent predictors of SSI (odds ratio [OR] = 11.1) (95% confidence interval [CI] = 3.0-40.8) and OR = 3.9 (1.0-14.8), respectively.

CONCLUSIONS

Patients with suppurative renal infections are submitted to life-saving emergency surgery. Urological surgeons should keep in mind that this carries a high risk for subsequent SSI. Effective preventive measures in these circumstance cannot be identified. Further research in this area is necessary to clarify this issue.

Japanese guidelines for prevention of perioperative infections in urological field

For urologists, it is very important to master surgical indications and surgical techniques. On the other hand, the knowledge of the prevention of perioperative infections and the improvement of surgical techniques should always be considered. Although the prevention of perioperative infections in each surgical field is a very important issue, the evidence and the number of guidelines are limited. Among them, the preparation of guidelines has progressed, especially in gastrointestinal surgery. The Center for Disease Control and Prevention (CDC) proposed guidelines for the prevention of surgical site infections, which have been used worldwide. In urology, the original guidelines were different from those of general surgery, due to many endourological procedures and urine exposure in the surgical field. The Japanese Society of UTI Cooperative Study Group has thus framed these guidelines supported by The Japanese Urological Association. The guidelines consist of the following nine techniques: open surgeries, laparoscopic surgeries, transurethral resection of bladder tumor, ureterorenoscope and transurethral lithotripsy, transurethral resection of the prostate, prostate biopsy, cystourethroscope, pediatric surgeries in the urological field, and extracorporeal shock wave lithotripsy and febrile neutropenia. These are the first guidelines for the prevention of perioperative infections in the urological field in Japan. Although most of these guidelines were made using reliable evidence, there are parts without enough evidence. Therefore, if new reliable data is reported, it will be necessary for these guidelines to be revised in the future.

Antibiotic prophylaxis in radical prostatectomy: 1-day versus 4-day treatments

OBJECTIVE

The standard protocol of antibiotic prophylaxis in radical prostatectomy remains to be established. We retrospectively compared the occurrence of perioperative infections following radical prostatectomy between two different protocols of antibiotic prophylaxis.

METHODS

This study included 106 cases of radical retropubic prostatectomy managed on the clinical pathways. Two different protocols of antibiotic prophylaxis were used in otherwise identical pathways. Between January and December 2004, 50 patients received a second generation cephem, cefotiam, for 4 days, beginning 30 min before surgery (4-day group), whilst between December 2004 and July 2005, only two doses of cefotiam were given on the day of operation in 56 patients (1-day group). The incidence of surgical site infection (SSI) and remote infection (RI) was retrospectively investigated.

RESULTS

Superficial incisional SSI occurred in one (1.8%) patient in the 1-day group, whereas no patient in the 4-day group developed SSI. No RI was observed in either the 1-day or 4-day group. Intravenous antibiotics were administered besides the pathway in a patient in the 1-day group because unexplained fever more than 38 degrees C continued postoperative day (POD) 2 through POD 4 without signs of SSI or RI. Excluding this case, postoperative more than 38 degrees C was rare and transient after POD 2.

CONCLUSION

The incidence of SSI and RI was low and not significantly different between the 1-day and 4-day groups. Therefore, the 1-day protocol of prophylactic antibiotic treatment seems adequate for preventing perioperative infections in radical prostatectomy.

MRSA in Urology: A UK Hospital Experience

OBJECTIVE

Methicillin-resistant Staphylococcus aureus (MRSA) infection appears to be increasing, the UK has one of the worst MRSA rates in Europe. As urological patients are at high risk, the aim of this study was to determine the number of newly diagnosed cases of MRSA detected in a urology ward.

PATIENTS AND METHODS

The urology department serves an annual local population of greater than 500,000 with 30 inpatient beds and a tertiary population of 1 million. Over a five year period, we retrospectively recorded all patients with a new diagnosis of MRSA. We also determined colonization site and if the diagnosis of MRSA was made in an elective surgical patient or a patient admitted as an emergency.

RESULTS

The mean number of newly diagnosed cases of MRSA was 20.6 per year. The percentage of patients with a new diagnosis of MRSA was less than or equal to 1% per year with no significant difference of new cases of MRSA over five years. Emergency patients had a trend towards a mean higher rate of MRSA. The commonest site of MRSA colonization was from catheters (32%) and open wounds (18%).

DISCUSSION

MRSA is of concern, as compared to methicillin-sensitive staphylococcus aureus, because it is associated with high rates of clinically relevant infection, increased hospital stay and cost, greater mortality and high vancomycin usage. Mandatory reporting has shown a steady increase in the number of cases of MRSA infection over the past four years. We found that the number of newly diagnosed cases of MRSA was low, at less than or equal to 1% of patients per year. Furthermore, the number of new cases of MRSA remained constant over five years suggesting low acquisition rates in a busy UK urology ward.

Incidence of and risk factors for surgical site infection in patients with radical cystectomy with urinary diversion

In radical cystectomy (RC), surgical-site infection (SSI) remains one of the most frustrating postoperative complications. Only a few reports have assessed SSI after RC according to the guideline authorized by the Centers for Disease Control and Prevention (CDC guideline). In this study, using the guideline, we assessed the incidence, causative organisms, classification, and risk factors for SSI in patients receiving RC with urinary diversion (UD). The subjects of this study were 104 patients who underwent RC with UD at the Department of Urology, Sapporo Medical University Hospital, between January 1996 and December 2003. As prophylactic antimicrobial agents, intravenous cephalosporins or penicillins were started before surgery and maintained until postoperative day 3. Patients who had preoperative bacteriuria were treated with antimicrobial agents before operation to eradicate the bacteria or reduce their number. The CDC guideline was used for the diagnosis of SSI. The overall incidence of SSI was 33%. The most frequent type of SSI was superficial incisional infection (71%). Methicillin-resistant Staphylococcus aureus (MRSA) was the most frequently isolated organism, accounting for 38% of the causative organisms. Operation time was shown to be a significant risk factor for SSI. Preoperative antibacterial chemotherapy for bacteriuria was not sufficiently efficacious to decrease the incidence of SSI. In our study, the incidence of SSI after RC was 33%, although 71% of the infections were superficial. It is necessary to establish more appropriate countermeasures to prevent SSI after RC with UD; in particular, that caused by MRSA.

Bacteria of preoperative urinary tract infections contaminate the surgical fields and develop surgical site infections in urological operations

BACKGROUND

The risk factors for surgical site infection (SSI) following urological operations have not been clearly identified, although the presence of a preoperative urinary tract infection (UTI) is thought to be one risk factor. We studied potential risk factors to clarify when and how bacteria contaminate wounds and SSI develop.

METHODS

Objects of the present study were patients with SSI after open urological operations that were performed at the Department of Urology, Miyazaki Medical College Hospital, University of Miyazaki, Kiyotake, Miyazaki, Japan, during the period between June 1999 and December 2000. Endourological operations, operations on children and short operations of less than 2 h duration were excluded. Patients were screened for the presence of UTI before the operation and subcutaneous swabs for culture were collected at the end of the operation by brushing with a sterile cotton-swab just before skin closure.

RESULTS

Surgical site infections occurred in 20 of 134 patients. Bacteria from the subcutaneous swabs were detected in 15 (75.0%) of the patients with SSI. All patients received antimicrobial prophylaxis (AMP), but bacteria from the subcutaneous swabs of patients with SSI were less susceptible to the agents (20.0%). Preoperative UTI were observed in 11 (55.0%) of the patients with SSI. In these patients, four had the same species of bacteria detected from urine, swab and wound, three had the same species from swab and wound and one had the same species from urine and wound.

CONCLUSIONS

Preoperative UTI was the most important risk factor for SSI following urological operations. It is most likely that the bacteria in the urine contaminated the surgical fields and the AMP resistant strains produced SSI.

Assessment of a protocol for prophylactic antibiotics to prevent perioperative infection in urological surgery: A preliminary study

BACKGROUND

The aim of the present study was to assess the usability and efficacy of our new protocol of prophylactic antibiotic use to prevent perioperative infection in urological surgery.

METHODS

We prospectively investigated 339 cases of typical urological surgery in our department between April 2001 and March 2002 (group I). We classified surgical procedures into four categories by invasiveness and contamination levels: category A, clean less invasive or endoscopic surgery; category B, clean invasive or clean contaminated surgery; category C, urinary tract diversion using the intestine; and category D, infected surgery. Antibiotics were administrated intravenously according to our protocol: category A, first or second generation cephems or penicillins during the operative day only; category B, first and second generation cephems or penicillins for 3 days; and category C, second or third generation cephems for 4 days. Category D was excluded from the analysis. To judge perioperative infections, the wound condition and general conditions were evaluated in terms of the surgical site infection (SSI) as well as remote infection (RI) up to postoperative day (POD) 14. We retrospectively reviewed 308 patients who underwent urological surgery between April 2000 and March 2001 (group II) as reference cases that were administered antibiotics without any restriction.

RESULTS

Perioperative infection rates (SSI + RI) in group I and group II were 25 of 339 (7.4%) and 35 of 308 (11.4%), respectively. Surgical site infection rates of categories A, B, and C in group I were 1.8%, 7.6%, and 30.0%, respectively, while those in group II were 2.0%, 7.4%, and 46.2%, respectively. There was no significant difference in infection rates in terms of RI and SSI between group I and group II. The amounts, as well as the prices, for intravenously administrated antibiotics and oral antibiotics decreased to approximately half and one-fifth, respectively.

CONCLUSION

Our protocol effectively decreased the amount of antibiotics used without increasing perioperative infection rates. Thus, our protocol of prophylactic antibiotic therapy would be recommended as an appropriate method for preventing perioperative infection in urological surgery.

Concentrations in plasma, urinary excretion, and bactericidal activity of linezolid (600 milligrams) versus those of ciprofloxacin (500 milligrams) in healthy volunteers receiving a single oral dose

In a randomized crossover study, 12 volunteers (6 males, 6 females) received a single oral dose of 600 mg of linezolid or 500 mg of ciprofloxacin to assess the concentrations in plasma (up to 24 h), urinary excretion (by high-pressure liquid chromatography), and bactericidal titers in urine (UBT) at intervals up to 120 h. The mean maximum concentration of linezolid in plasma was 13.1 mg/liter, and that of ciprofloxacin was 2.46 mg/liter. The median cumulative levels of renal excretion of the administered dose of the parent drug were 44% for linezolid (range, 28 to 47%; mean +/- standard deviation, 40% +/- 7.8%) and 43% for ciprofloxacin (range, 20 to 56%; mean +/- standard deviation, 40% +/- 9.3%). The UBTs, i.e., the highest twofold dilution (with antibiotic-free urine used as the diluent) of urine that was still bactericidal, were determined for a reference strain and five gram-positive clinical uropathogens for which the MICs of linezolid and ciprofloxacin were as follows: Staphylococcus aureus ATCC 27278, 2 and 0.25 mg/liter, respectively; Staphylococcus aureus (methicillin susceptible), 1 and 16 mg/liter, respectively; Staphylococcus aureus (methicillin resistant), 2 and 64 mg/liter, respectively; Staphylococcus saprophyticus (methicillin susceptible), 1 and 0.25 mg/liter, respectively; Enterococcus faecalis, 2 and 1 mg/liter, respectively; and Enterococcus faecium, 2 and 1 mg/liter, respectively. The median UBTs of linezolid measured within the first 6 h were 1:96 for each of the two enterococcal strains and between 1:128 and 1:256 for the four staphylococcal strains. The median UBTs of ciprofloxacin were 1:64 for the two enterococcal strains; between 1:384 and 1:512 for the two ciprofloxacin-susceptible strains; and 1 (bactericidal activity of undiluted urine only) and 1:2 for the two resistant staphylococcal strains, respectively. The areas under the UBT-time curve (AUBT) for linezolid and ciprofloxacin showed no statistically significant (P<0.05) differences except for a better AUBT for linezolid for the two ciprofloxacin-resistant staphylococcal strains. For linezolid there were no statistically significant differences in UBTs or AUBTs for ciprofloxacin-susceptible and -resistant strains. Thus, the bactericidal activities of linezolid and ciprofloxacin against susceptible strains in urine were comparable, whereas linezolid also exhibited the same good bactericidal activity against ciprofloxacin-resistant strains. Therefore, linezolid should be tested for use as empirical treatment for complicated urinary tract infections due to gram-positive uropathogens in an appropriate clinical trial.

Toxicity and Antimicrobial Activity of a Hydrocolloid Dressing Containing Silver Particles in an ex vivo Model of Cutaneous Infection

In the present study we examined the effects of two hydrocolloid wound dressings (conventional silver-free Comfeel, silver-incorporating Contreet-H) on uninfected and Candida albicans- or methicillin-resistant Staphylococcus aureus-infected reconstituted human epithelium (RHE). The morphological alterations of the keratinocytes caused by infection and by treatment were analysed with light and electron microscopy. As a measure of epithelial cell damage the release of lactate dehydrogenase from epithelial cells into the surrounding medium was monitored. Application of Contreet-H or Comfeel to uninfected RHE induced no major morphological effects on epithelial cells. Both wound dressings reduced the growth of micro-organisms. Specific alterations of the infected epithelium (vacuoles, spongiosis, oedema, detachment of keratinocytes) and invasion of the epithelium were significantly reduced only by treatment with Contreet-H. At the ultrastructural level release of silver by Contreet-H and superior antimicrobial efficacy could be verified. In summary, treatment with both wound dressings reduced the number of pathogens, with the silver-based wound dressing providing a more effective antimicrobial activity. This resulted in a strong decrease of pathogen-specific alterations of the infected epithelium. We present evidence that delivering silver to infected keratinocytes in a moist healing environment improves the benefit/risk ratio as compared to silver-free wound dressings.

Prophylactic antimicrobial agents in urologic laparoscopic surgery: 1-day versus 3-day treatment

Although the incidence of surgical site infection (SSI) is generally low in laparoscopic urologic surgery, the standard protocol for prophylactic use of antimicrobial agents remains to be established. We retrospectively compared the incidence and severity of SSI after laparoscopic surgery between two different protocols for prophylactic use of antimicrobial agents. This study included 114 patients who underwent urologic laparoscopic surgery categorized as "clean" or "clean-contaminated" in Sapporo Medical University School Hospital between January 1996 and October 2002. As a prophylactic antimicrobial agent, one of the cephalosporins or penicillins was administered intravenously to all patients. For 46 consecutive patients between January 1996 and July 2000, an antimicrobial agent was given 30 min before operation and thereafter every 12 h on the same day and the next 2 days after operation (the 3-day group). For 68 consecutive patients from August 2000 to October 2002, an antimicrobial agent was given once 30 min before operation and was additionally given only in the evening or night of the day of operation (the 1-day group). The incidence of SSI was retrospectively investigated. There were two patients who developed SSI in each group (4.3% in the 3-day group and 2.9% in the 1-day group). The incidence of SSI was not significantly different between the two groups. The 1-day protocol has efficacy equal to that of the 3-day protocol in prophylaxis of SSI. The 1-day use of a prophylactic antimicrobial agent may be recommended for the clean or clean-contaminated urologic laparoscopic surgery described above.

Prevention of postsurgical infections: some like it hot

PURPOSE OF THE REVIEW

The present review covers the literature on prevention of surgical site infections published during 2001. Only papers that offer new insights or question current recommendations are included.

RECENT FINDINGS

The most interesting advances have been made in the preoperative preparation of the patient. In particular, the effects of preoperative warming of the patient, either generally or locally at the incision site, on the rate of surgical site infections are impressive and warrant further investigation. Also, the effects of strict control of perioperative blood glucose levels and of preoperative eradication of nasal carriage of Staphylococcus aureus should be studied in greater detail.

SUMMARY

The protective effect of local and systemic warming before surgical procedures has been described in two well designed studies. Although a final judgement regarding effectiveness can only be made after more extensive investigations have been conducted, there appear to be few arguments against application of this cheap and safe measure. Thus, implementation of preoperative warming can be justified in settings associated with high rates of surgical site infections.