Hospital-wide Antibiogram Research Articles

A Single Hospital-Wide Antibiogram is Insufficient to Account for Differences in Antibiotic Resistance Patterns Across Multiple ICUs.

Infection is a common cause of mortality within intensive care units (ICUs). Antibiotic resistance patterns and culture data are used to create antibiograms. Knowledge of antibiograms facilitates guiding empiric therapies and reduces mortality. Most major hospitals utilize data collection to create hospital-wide antibiograms. Previous studies have shown significant differences in susceptibility patterns between hospital wards and ICUs. We hypothesize that institutional or combined ICU antibiograms are inadequate to account for differences in susceptibility for patients in individual ICUs. Culture and susceptibility data were reviewed over a 1-year period for 13 bacteria in the following ICUs: Surgical/Trauma, Medical, Neuroscience, Burn, and Emergency department. Antibiotic management decisions are made by individual teams. Nine species had sufficient data for inclusion into an All-ICU antibiogram. E coli and S aureus were the most common isolates. Seven species had significant differences in susceptibility patterns between ICUs. E cloacae showed higher rates of resistance to multiple antibiotics in the STICU than other ICUs. P aeruginosa susceptibility rates in the NSICU and BICU were 88% and 92%, respectively, compared to 60% and 55% in the STICU and MICU. Cephalosporins and Aztreonam had reduced efficacy against E coli in the NSICU, however remain effective in other ICUs. The results of this study show that different ICUs do have variability in antibiotic susceptibility patterns within a single hospital. While this only represents a single institution, it shows that the use of hospital-wide antibiograms is inadequate for creating empiric antibiotic protocols within individual ICUs.

#74: Development of a Solid-Organ Transplant-Specific Antibiogram in a Tertiary Pediatric Hospital in Canada

Abstract Background Solid-organ transplant (SOT) patients are more vulnerable to infections by antimicrobial-resistant organisms (AROs) because of their hospital exposure, compromised immune systems, and antimicrobial exposure. Therefore, it may be useful for transplant facilities to create transplant-specific antibiograms to direct empirical antimicrobial regimens and monitor trends in antimicrobial resistance. Methods SOT (i.e., lung, liver, renal, and heart) antibiograms were created using antimicrobial susceptibility data on isolates from 2012 to 2018 at The Hospital for Sick Children, a tertiary pediatric hospital and transplant center in Toronto, Ontario. The Clinical Laboratory Standards Institute (CLSI) guidelines were followed to generate the antibiograms. The first clinical isolate of a species from a patient in each year was included irrespective of body site; duplicates were eliminated and surveillance cultures were excluded. Results from 2 years of data were pooled on a rolling basis to achieve an adequate sample size in both SOT and hospital-wide antibiogram. The SOT antibiogram was then compared with the hospital-wide antibiogram of the compatible 2 pooled years from 2012 to 2018. For subgroup analyses in the SOT population, organ-specific antibiograms and transplant timing-specific antibiograms (pretransplant, post-transplant <1 year, and post-transplant ≥1 year) between transplant and sample collection dates were analyzed. All proportions were compared using the χ 2 test. Results The top 5 organisms in one (2 year) analysis period of the SOT antibiogram were Escherichia coli (n = 29), Staphylococcus aureus (n = 28), Pseudomonas aeruginosa (n = 20), Enterobacter cloacae complex (n = 18), and Klebsiella pneumoniae (n = 17). For E.coli, susceptibility in the SOT antibiogram was significantly lower than those in the hospital-wide antibiogram in 2017/2018 for ampicillin (27% vs. 48%; P = 0.015), piperacillin/tazobactam (55% vs. 87%; P < 0.001), cefotaxime (59% vs. 88%; P < 0.001), ciprofloxacin (71% vs. 87%; P = 0.007) and cotrimoxazole (41% vs. 69%; P < 0.001), but not significantly different for gentamicin (94% vs. 91%; P = 0.490), tobramycin (88% vs. 90%; P = 0.701) and amikacin (100% vs. 99%; P = 0.558). These findings were consistent throughout the study period in E.coli. There was no statistically significant difference between the SOT and hospital-wide antibiograms for other organisms. There were no significant differences in susceptibility between organ-specific antibiograms or transplant timing-specific antibiograms in 2012–2018. Conclusions We found that E.coli from the SOT population had a significantly lower sensitivity to all antimicrobials, except aminoglycosides, compared with those from the hospital-wide population. Other organisms had similar susceptibility to the hospital-wide population. Developing a SOT antibiogram will assist in revising and improving empiric treatment guidelines for this population.

Solid organ transplant-specific antibiogram in a tertiary pediatric hospital in Canada.

SOT recipients are more vulnerable to infections with antimicrobial-resistant organisms, and therefore, it may be useful for transplant centers to create transplant-specific antibiograms to direct empirical antimicrobial regimens and monitor trends in antimicrobial resistance. SOT-specific antibiograms were created using antimicrobial susceptibility data on isolates from 2012 to 2018 at The Hospital for Sick Children, Toronto, Ontario, Canada. The CLSI guidelines were followed to generate the antibiograms except that results from 2years of data were pooled on a rolling basis to achieve larger sample sizes. The 3 most frequent organisms in one analysis period of the SOT antibiogram wereEscherichia coli (average sample size ±standard deviation; n=28.7±3.8), Staphylococcus aureus (n=27.8±5.0), and Pseudomonas aeruginosa (non-CF) (n=19.8±8.8). For E.coli, susceptibilities in the SOT antibiogram were significantly lower than those in the hospital-wide antibiogram in 2017-2018 for ampicillin (27% vs 47%;p=.014), piperacillin/tazobactam (55% vs 88%;p<.001), cefotaxime (59% vs 89%;p<.001), ciprofloxacin (71% vs 88%;p=.007), and trimethoprim-sulfamethoxazole (41% vs 69%;p=.001), but not significantly different for aminoglycosides and meropenem.In the SOT antibiogram of E. coli, decreased susceptibility trend was confirmed in some antibiotics, including piperacillin/tazobactam (83% in 2012-2013 vs 55% in 2017-2018). At our center, the solid organ transplant-specific antibiogram revealed important differences inE. colisusceptibilities and trends in antimicrobial resistance. Developing a SOT antibiogram will assist in revising and improving empiric treatment guidelines as well as monitoring antimicrobial resistance in this population.

192. A Hematology/Oncology Unit-Specific Antibiogram Emphasizes the Need for Intensified Local Stewardship

BackgroundAntibiograms are important stewardship tools for empiric antibiotic prescribing. Appropriate therapy is particularly important in patients with hematologic malignancies and bone marrow transplants being treated for febrile neutropenia. These patients are at high risk for multi-drug resistance based on extensive prior antibiotic and hospital exposures, and therefore, hospital-wide antibiograms may not reliably reflect resistance patterns for this population. We created a unit-specific antibiogram for a closed hematology/oncology unit and hypothesized there would be decreased antibiotic susceptibilities compared to the hospital-wide antibiogram.MethodsAll positive cultures with antimicrobial susceptibilities on a closed 32-bed hematology-oncology unit from 7/2016-6/2019 were obtained from the microbiology laboratory. Based on recommendations by the Clinical and Laboratory Standards Institute (CLSI), only organisms with > 30 isolates were included in antibiogram analysis. Susceptibilities were compared to those reported in our hospital-wide antibiograms from the same time period using Fisher’s exact test.ResultsTwo organisms met CLSI criteria: Escherichia coli (n=83) and Klebsiella pneumoniae (n=31). Unit Escherichia coli isolates were significantly more resistant to almost all commonly tested antibiotics (Table 1). Klebsiella pneumoniae unit susceptibilities were significantly lower for many antibiotics, including aztreonam, ceftriaxone, cefepime, levofloxacin, piperacillin-tazobactam and tobramycin (Table 1).Table 1: Percentage of Escherichia coli and Klebsiella pneumoniae isolates susceptible to reported antibiotic agents ConclusionOur hematology-oncology antibiogram showed significantly lower antibiotic susceptibilities in Escherichia Coli and Klebsiella pneumoniae compared with the hospital-wide antibiogram. These findings can help guide prescribers toward appropriate broad-spectrum empiric therapy. Additionally, results suggest a need for intensified stewardship measures to prevent multi-drug resistance in this population.Disclosures All Authors: No reported disclosures

Widespread antimicrobial resistance among bacterial infections in a Rwandan referral hospital.

BackgroundResistance among bacterial infections is increasingly well-documented in high-income countries; however, relatively little is known about bacterial antimicrobial resistance in low-income countries, where the burden of infections is high.MethodsWe prospectively screened all adult inpatients at a referral hospital in Rwanda for suspected infection for seven months. Blood, urine, wound and sputum samples were cultured and tested for antibiotic susceptibility. We examined factors associated with resistance and compared hospital outcomes for participants with and without resistant isolates.ResultsWe screened 19,178 patient-days, and enrolled 647 unique participants with suspected infection. We obtained 942 culture specimens, of which 357 were culture-positive specimens. Of these positive specimens, 155 (43.4%) were wound, 83 (23.2%) urine, 64 (17.9%) blood, and 55 (15.4%) sputum. Gram-negative bacteria comprised 323 (88.7%) of all isolates. Of 241 Gram-negative isolates tested for ceftriaxone, 183 (75.9%) were resistant. Of 92 Gram-negative isolates tested for the extended spectrum beta-lactamase (ESBL) positive phenotype, 66 (71.7%) were ESBL positive phenotype. Transfer from another facility, recent surgery or antibiotic exposure, and hospital-acquired infection were each associated with resistance. Mortality was 19.6% for all enrolled participants.ConclusionsThis is the first published prospective hospital-wide antibiogram of multiple specimen types from East Africa with ESBL testing. Our study suggests that low-resource settings with limited and inconsistent access to the full range of antibiotic classes may bear the highest burden of resistant infections. Hospital-acquired infections and recent antibiotic exposure are associated with a high proportion of resistant infections. Efforts to slow the development of resistance and supply effective antibiotics are urgently needed.

Comparing an Emergency Department–specific Antibiogram Versus Hospital-wide Antibiogram and Therapeutic Dilemmas for Uncomplicated Cystitis

Background The emergency department (ED) lies between the inpatient and outpatient worlds. Varying rates of antimicrobial resistance along with the volume of patients presenting to the ED with potential urinary tract infections make empiric antibiotic selection difficult but vital. However, simply referring to the guidelines may neither optimize therapy nor mitigate resistance. Methods This was a retrospective cohort study comparing antimicrobial sensitivities of women from home, diagnosed with uncomplicated cystitis and discharged home, versus sensitivities of an institution-wide antibiogram between September 1, 2016, and February 28, 2017. The primary outcome was determining whether there was a difference between Escherichia coli sensitivities in nonpregnant women older than 14 years, from home, being discharged home and diagnosed with uncomplicated cystitis versus an institution-specific antibiogram. Results Over the study period, 258 patients were evaluated for uncomplicated cystitis with 128 patients included in the final analysis as the retrospective cohort after 130 patients were excluded. Statistically significant differences between the retrospective cohort and institution-wide antibiogram were 80.5% versus 57% (P &lt; 0.001) for amoxicillin/clavulanic acid, 85.9% versus 75% (P = 0.007) for cefazolin, 94.5% versus 86% (P = 0.008) for ceftriaxone, 96.1% versus 87% (P = 0.003) for cefepime, 97.5% versus 66% (P &lt; 0.001) for levofloxacin, and 99.2% versus 95% (P = 0.032) for nitrofurantoin, respectively. Conclusions Our study shows differences between an ED-specific antibiogram and institution-wide antibiogram. Many common and guideline-recommended antimicrobials used to treat acute uncomplicated cystitis may not be appropriate. Compiling ED-specific antibiograms at all institutions may help to optimally guide therapy.

Solid organ transplant antibiograms: an opportunity for antimicrobial stewardship

ObjectivesWe aimed to compare the antimicrobial susceptibility percentages in blood and urine bacterial isolates recovered from solid organ transplant (SOT) recipients with those reported in the hospital-wide antibiogram. MethodsRetrospective review of the antimicrobial susceptibilities of bacterial isolates recovered from SOT recipients at a 1550-bed hospital over a 2-year period. Antibiograms were categorized by anatomic site (blood and urine). Percentage of bacterial susceptibilities to specific antibiotics were compared with the hospital-wide antibiogram. ResultsA total of 1889 unique cultures were identified. Blood and urine isolates of Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa had significantly lower susceptibility to first and second line antibiotics compared to the hospital-wide antibiogram. ConclusionSignificant differences in susceptibilities between isolates from blood and urine cultures from SOT recipients and the hospital-wide antibiogram were found. A population-based strategy for the development of antibiograms specific for this group of high-risk patients could better guide appropriate empiric antimicrobial selection.

Re: “Antimicrobial Susceptibility of Escherichia coli in Uncomplicated Cystitis in the Emergency Department: Is the Hospital Antibiogram an Effective Treatment Guide?”

Objectives The objective was to compare the rates of antimicrobial susceptibility in strains of Escherichia coli isolated from uncomplicated cystitis cases presenting to the emergency department (ED) of a tertiary care center to those reported on that institution's hospital-wide antibiogram. The hypothesis was that cases of uncomplicated cystitis presenting to the ED will exhibit higher antimicrobial susceptibility than is reported by the hospital-wide antibiogram. Methods A retrospective chart review of patients who were diagnosed with uncomplicated cystitis in the ED of a large, academic tertiary care center was conducted. Due to an error in the implementation of a new electronic medical record system at this institution in 2009, all urine samples with any abnormality were reflexively sent for culture. The authors were then able to review and record the antibiotic susceptibility patterns of all cultures that grew E. coli. Exclusion criteria included fever, subsequent hospital admission, treatment of suspected pyelonephritis, receiving current cystitis treatment, male sex, indwelling catheters, recent surgery or hospitalization, or asymptomatic for cystitis. Culture isolate antimicrobial susceptibility was then compared with the hospital-wide antibiogram of the same period. Empiric treatment regimens were also recorded as secondary data. Results Greater susceptibility to trimethoprim-sulfamethoxazole (TMP-SMX; 80% vs. 71%), cefazolin (97% vs. 87%), and ciprofloxacin (89% vs. 73%) was found in our population than was published in the hospital antibiogram. These differences were shown to be statistically significant using Fisher's exact test (p < 0.05). A very high sensitivity to nitrofurantoin (99%), similar to the hospital antibiogram (98%), was also found. Also noted was a high rate of antimicrobial susceptibility when specific empiric treatment was initiated with TMP-SMX or ciprofloxacin: 92 and 89%, respectively. Conclusions The greater susceptibility of E. coli to TMP-SMX, cefazolin, and ciprofloxacin observed in this population supports the hypothesis that antimicrobial susceptibility rates in uncomplicated cystitis presenting to the ED are greater than those reported in the hospital-wide antibiogram. This could affect treatment guidelines by confirming that antimicrobials currently recommended for use in uncomplicated cystitis are more effective in this setting than currently reported by the hospital-wide antibiogram.

Antibiograms in resource limited settings: Are stratified antibiograms better?

Background Antibiograms often act as a reference guide for empirical selection of antibiotics. Hospital-wide antibiograms constructed on the basis of cumulative antimicrobial susceptibility data from diverse patient groups can often be misleading. In order to show the significance of age- and location-stratified antibiograms, this study compared hospital-wide antibiograms with stratified antibiograms for the clinical isolates of Pseudomonas aeruginosa. Methods Stratified antibiograms were created on the basis of patient age (<18 years, 18–50 years, >50 years) and location (inpatient or outpatient) using all 2011, 2012 and 2013 clinical isolates of P. aeruginosa isolates. Susceptibility rates were compared among cumulative and stratified antibiograms using non-parametric inferential statistics. Results The hospital-wide antibiogram under-estimated susceptibility rates in adult patients isolates (age group = 18–50 years) and over-estimated susceptibility rates in isolates from the paediatric patients and elderly. Paediatric isolates were found to be less susceptible to amikacin and imipenem, whereas isolates from elderly patients >50 years were less susceptible to ciprofloxacin. Statistically significant difference was seen in the susceptibility rates of OPD and IPD isolates of P. aeruginosa in the case of the paediatric age group. Susceptibility rates for all drugs were lower for isolates from inpatients than from outpatients. Conclusion Age and location associated differences in susceptibility rates have the potential to influence empirical antibiotic selection, which was shown in stratified antibiograms of P. aeruginosa that is obscured by hospital-wide antibiograms.

Antimicrobial Susceptibility ofEscherichia coliin Uncomplicated Cystitis in the Emergency Department: Is the Hospital Antibiogram an Effective Treatment Guide?

The objective was to compare the rates of antimicrobial susceptibility in strains of Escherichia coli isolated from uncomplicated cystitis cases presenting to the emergency department (ED) of a tertiary care center to those reported on that institution's hospital-wide antibiogram. The hypothesis was that cases of uncomplicated cystitis presenting to the ED will exhibit higher antimicrobial susceptibility than is reported by the hospital-wide antibiogram. A retrospective chart review of patients who were diagnosed with uncomplicated cystitis in the ED of a large, academic tertiary care center was conducted. Due to an error in the implementation of a new electronic medical record system at this institution in 2009, all urine samples with any abnormality were reflexively sent for culture. The authors were then able to review and record the antibiotic susceptibility patterns of all cultures that grew E. coli. Exclusion criteria included fever, subsequent hospital admission, treatment of suspected pyelonephritis, receiving current cystitis treatment, male sex, indwelling catheters, recent surgery or hospitalization, or asymptomatic for cystitis. Culture isolate antimicrobial susceptibility was then compared with the hospital-wide antibiogram of the same period. Empiric treatment regimens were also recorded as secondary data. Greater susceptibility to trimethoprim-sulfamethoxazole (TMP-SMX; 80% vs. 71%), cefazolin (97% vs. 87%), and ciprofloxacin (89% vs. 73%) was found in our population than was published in the hospital antibiogram. These differences were shown to be statistically significant using Fisher's exact test (p < 0.05). A very high sensitivity to nitrofurantoin (99%), similar to the hospital antibiogram (98%), was also found. Also noted was a high rate of antimicrobial susceptibility when specific empiric treatment was initiated with TMP-SMX or ciprofloxacin: 92 and 89%, respectively. The greater susceptibility of E. coli to TMP-SMX, cefazolin, and ciprofloxacin observed in this population supports the hypothesis that antimicrobial susceptibility rates in uncomplicated cystitis presenting to the ED are greater than those reported in the hospital-wide antibiogram. This could affect treatment guidelines by confirming that antimicrobials currently recommended for use in uncomplicated cystitis are more effective in this setting than currently reported by the hospital-wide antibiogram.

Comparison of bacteria isolated from emergency department patients versus hospitalized patients

The frequencies and corresponding susceptibilities of bacteria isolated from patients in the emergency department (ED) were compared with those from hospitalized patients. A microbiology laboratory report of all positive bacterial cultures obtained in the ED, regardless of the source (e.g., blood, urine, sputum), was obtained. In the case of duplicate cultures, only the first isolate cultured from a single patient was included. Colonization-site cultures (e.g., nasal swabs) and culture reports identified by the laboratory as contaminant organisms were excluded from the evaluation. Antimicrobial susceptibility results were then compiled into a standardized ED-specific antibiogram. Antimicrobial susceptibilities for each pathogen in the ED antibiogram were compared with those in the hospitalwide antibiogram. If there was a difference of ≥5% between the susceptibility of a single antimicrobial agent, chi-square tests were conducted, and unadjusted odds ratios were calculated. Pathogens with fewer than 30 isolates were excluded from the susceptibility comparison. A total of 3140 cultures were evaluated (1417 from the ED, 1723 from the hospital). The frequencies of pathogens isolated in the ED and hospitalwide were similar, with the exception of Escherichia coli, which were more commonly isolated in ED patients, and Enterococcus species and Pseudomonas aeruginosa, which were more common in hospitalized patients. Significant differences in susceptibility profiles were identified for Staphylococcus aureus, coagulase-negative Staphylococcus, Enterococcus faecalis, E. coli, Klebsiella pneumoniae, and P. aeruginosa. Significant differences in the frequencies of bacteria isolated and corresponding susceptibilities were found in cultures obtained in ED patients compared with those obtained in hospitalized patients.

Poster Presenter Juggled Research, Homework

Poster Presenter Juggled Research, Homework

Comparison of a Hospital-wide Antibiogram to That of an Associated Long Term Care Facility

Introduction/Objective: Long term care facilities (LTCFs) can select, enrich and serve as reservoirs for antibiotic resistant bacteria. Although antibiograms have been used in hospitals to guide caregivers in choosing appropriate antibacterial therapy, an antibiogram specifically generated from a long-term care facility has rarely been obtained. The objective of this study was to construct an antibiogram for a specific long-term care facility and compare it to that of the associated hospital that receives its patients.

Comparison of Unit-Specific and Hospital-Wide Antibiograms Potential Implications for Selection of Empirical Antimicrobial Therapy

To identify differences between unit-specific and hospital-wide antibiograms and to determine the potential impact of these differences on selection of empirical antimicrobial therapy. A 625-bed tertiary care medical center. Antimicrobial susceptibility results were collected for all inpatient clinical bacterial isolates recovered over a 3-year period; isolates were categorized by the hospital location of the patient at the time of sampling and by the anatomic site from which the isolate was recovered. Antibiograms from each unit were compiled for the most commonly isolated organisms and were compared to the hospital-wide antibiogram. A total of 9,970 bacterial isolates were evaluated in this study, including 2,646 enterococcal isolates, 2,806 S. aureus isolates, 2,795 E. coli isolates, and 1,723 Pseudomonas aeruginosa isolates. The percentages of bacterial isolates resistant to antimicrobials were significantly higher in the medical ICU and surgical ICU than the hospital-wide antibiogram would have predicted, whereas the percentages of isolates susceptible to antimicrobials were significantly higher in the non-ICU units, compared with the hospital overall. However, on general medicine units, the prevalence of susceptibility to levofloxacin was significantly lower than that for the hospital overall. Unit-specific antibiograms are important for making informed decisions about empirical antimicrobial therapy, because the hospital-wide antibiogram may mask important differences in susceptibility rates across different units. These differences may have important implications for selecting the optimal empirical antimicrobial therapy.

Acinetobacter (ACBA) in sternal surgical site infections (SSI) after cardiac surgery: Case control study to determine significance and outcome

BACKGROUND/OBJECTIVES: Between January 2003 and December 2004, our hospital experienced a hospital-wide outbreak of ACBA, with a nosocomial incidence increase of 48% compared with 2002. The crude mortality for nosocomial acquisition of ACBA was 24%. The hospital-wide antibiogram for nosocomial ACBA demonstrated the following percentages of sensitive organisms: imipenem, 61%; ampicillinsulbactam, 21%; gentamicin, 14%; and quinolone, 13%. The approximately 2000 cardiovascular surgery (CVS) patients per year are admitted to surgical intensive care units, where 43% of ACBA cases are first identified. METHODS: Surveillance for SSIs is conducted concurrently with retrospective record review and post-discharge patient surveys. ACBA incidence is analyzed with CERNER Information System, a 48-hour interval as a marker of probable nosocomial acquisition, and no distinction for colonization or infection. Cases were patients with sternal SSI and positive ACBA cultures; controls were patients with sternal SSI without ACBA. Student's T test was used to compare continuous variables, and chi square was used to compare categorical variables. RESULTS: Between 2003 and 2004, nine patients (0.2% of all CVS; 11.7% of all sternal SSI) had post-operative sternal cultures positive for ACBA. ACBA was only found following a previous diagnosis of sternal SSI or dehiscence. ACBA was never found as the sole organism associated with SSI, and all case patients had debridement with subsequent open wounds before ACBA was cultured. A case control study demonstrated that colonization or infection with a secondary organism was statistically significant. Unexpectedly, blood loss was more severe in controls. All other variables (listed in table) were not significant. Patients with ACBA Patients without ACBA Significance Secondary organisms/infection 9/9 5/65 RR = 13.6 (5.9 – 31.6) Diabetes 6/9 40/68 NS Outcome-expired 2/7 10/67 NS Estimated blood loss 383.3 ± 19.5 504.4 ± 22.4 p = 0.14 Age 60.4 ± 7.8 62.1 ± 7.9 NS Pre-op days 2.7 ± 1.6 2.1 ± 1.5 NS Pre-op blood sugar 139.3 ± 11.8 122.5 ± 11.1 NS Body Mass Index 35.3 ± 5.8 32.6 ± 8.0 NS OR Time 3:39 ± 0:38 4:07 ± 1:19 NS Days -Surgery to Diagnosis 21.3 ± 4.6 23.6 ± 4.9 NS CONCLUSIONS: Although ACBA transmission is relatively common in the surgical intensive care setting, its contribution to diagnosis of SSI appears minimal. In our institution, ACBA associated with CVS SSI appears as secondary infection or colonization and appears as an opportunistic organism, possibly related to devitalized tissue.

Antibiotic susceptibility in the surgical intensive care unit compared with the hospital-wide antibiogram: Kaufman D, Haas CE, Edinger R, et al. Arch Surg 133:1041, 1998

Antibiotic susceptibility in the surgical intensive care unit compared with the hospital-wide antibiogram: Kaufman D, Haas CE, Edinger R, et al. Arch Surg 133:1041, 1998