Third-generation cephalosporins and vancomycin as risk factors for postoperative vancomycin-resistant enterococcus infection

Vancomycin-resistant enterococci: 15 years and counting

We review the history of vancomycin-resistant enterococci (VRE) and propose a causal model illustrating the roles of exposure to VRE reservoirs, patient characteristics, antimicrobial exposure, and prevalence of VRE in the progression from potential VRE reservoirs to active disease in hospitalized patients. Differences in VRE colonization and VRE infection are discussed with respect to hospital surveillance methodology and implications for interventions. We further document clonal transmission of VRE in a large, urban, teaching hospital and demonstrate VRE susceptibility to a wide array of antimicrobial agents. This model can guide the identification of mutable factors that are focal points for intervention.

Changes in the prevalence of vancomycin-resistant enterococci in response to antimicrobial formulary interventions: impact of progressive restrictions on use of vancomycin and third-generation cephalosporins

This study sought to assess the impact of restricting use of vancomycin and third-generation cephalosporins on vancomycin-resistant enterococci (VRE) prevalence. All clinical enterococcal isolates identified at a large academic medical center during a 10-year period were analyzed. Changes in VRE prevalence after sequential restrictions on use of vancomycin and third-generation cephalosporins were evaluated. The correlation between antibiotic use and VRE prevalence was also investigated. Vancomycin use initially decreased by 23.9% but returned to preintervention levels by the end of the study. Third-generation cephalosporin use decreased by 85.8%. However, VRE prevalence increased steadily from 17.4% to 29.6% during the 10-year period (P<.001). Clindamycin use was significantly correlated with VRE prevalence. Restricting the use of vancomycin and third-generations cephalosporins had little impact on VRE prevalence. The association between clindamycin use and the prevalence of VRE suggests that restriction of this and perhaps other antianaerobic agents might be an important component of future antimicrobial interventions.

Ceftriaxone and cefotaxime use in Victorian hospitals

OBJECTIVE

To determine patterns of use of ceftriaxone and cefotaxime (CEFX) in Victorian hospitals and to identify areas for improvement.

DESIGN, PATIENTS AND SETTING

A concurrent, observational evaluation of CEFX use in patients commencing a course of these drugs between 8 and 14 September, 1999, in 51 Victorian hospitals.

MAIN OUTCOME MEASURES

Proportion of patients treated with CEFX; indications; duration of use; concordance with recommendations of national antibiotic guidelines (Therapeutic guidelines: antibiotic, 10th edition [AG10]).

RESULTS

671 patients were treated with CEFX. The overall rate of use was 43 patients per 1000 inpatient separations. Treatment of respiratory tract infection accounted for 352 patients (52%) and surgical prophylaxis for 99 patients (15%). Treatment of skin/soft tissue, urinary tract and gastrointestinal tract infections accounted for about 7% of patients each. The median duration of CEFX courses was 3.0 days. The overall rate of concordance with indications recommended in AG10 was 27%. The rate of concordance for empirical treatment of respiratory tract infection was 24%. Of the 195 patients treated empirically with CEFX for community-acquired respiratory tract infection and assessed as non-concordant, 64% did not have radiological evidence of pneumonia, and a further 30% did not fulfill the criteria for severe pneumonia. All courses given for surgical prophylaxis were non-concordant.

CONCLUSIONS

CEFX is widely used in Victorian hospitals, mostly to treat lower respiratory tract infection and in surgical prophylaxis of infection. The rate of concordance with AG10 is low. Potential areas for intervention include empirical treatment of respiratory tract infection and use in surgical prophylaxis.

The effect of an antimicrobial formulary change on hospital resistance patterns

A university hospital formulary change that was designed to reduce the use of the third-generation cephalosporins ceftazidime and cefotaxime and replace them with the so-called "fourth-generation" cephalosporin cefepime was evaluated. A retrospective review of antibiotic use and antimicrobial resistance during two 6-month periods before and after the formulary change was performed. All hospital patients with vancomycin-resistant Enterococcus (VRE), ceftazidime-resistant Klebsiella pneumoniae (CRKP), methicillin-resistant Staphylococcus aureus (MRSA), piperacillin-resistant Pseudomonas aeruginosa (PRPA), and ceftazidime-resistant P. aeruginosa (CRPA) infections were included in the study Ceftazidime use decreased from 9600 g to 99 g, and cefotaxime use decreased from 6314 g to 732 g, which represented a combined decrease of 89%. Use of cefepime increased from 0 g to 5396 g. Infections from CRKP decreased from 13% to 3%, PRPA infections decreased from 22% to 14%, and CRPA infections decreased from 25% to 15% (p<0.05 for all). Infections from MRSA dropped insignificantly, and VRE infections increased significantly. Substituting cefepime for ceftazidime and cefotaxime while reducing the overall use of cephalosporins appears to decrease rates of CRKP, PRPA, and CRPA.

Infectious diseases in gynecologic oncology: an overview

The increasing trend of a multimodal therapeutic approach in gynecologic oncology in the last few years has markedly changed the nature, frequency, and clinical presentation of infectious diseases. Despite the improved diagnostic tools, refined surgical technique, and routine use of prophylactic antibiotics, the morbidity and mortality of infectious complications remain significant. The rational use of available treatment resources, the recognition of risk factors, and increased awareness of host-cancer interactions should reduce the incidence of these serious infectious complications. The improved prevention and more efficient treatment of infections in the gynecologic oncology patient will not only improve prognosis but also have a significant economic impact as well.

The microbiology of postoperative peritonitis

Postoperative peritonitis carries a higher risk of complications and mortality than does community-acquired disease. Little, however, is known about the specific microbiology of this condition. To gain insight into this problem, the microbiological findings of 67 patients with postoperative peritonitis were compared with those of 68 patients with community-acquired peritonitis. In a comparison of postoperative peritonitis with community-acquired disease, the number of isolates of enterococci (23 versus 6) and Enterobacter species (13 versus 4) were increased and the number of isolates of Escherichia coli (21 versus 42) were reduced. Antibiotic therapy before reintervention increased the number of resistant organisms at relaparotomy (33% versus 8%). The in vitro efficacy of the primary antibiotic or combination of drugs did not affect mortality rates (40% versus 38% after effective and ineffective treatment, respectively). Thus, the microbiology of postoperative peritonitis differs significantly from that of community-acquired disease, and specific antibiotic therapy is required, despite the doubtful impact on survival.

Multi-hospital analysis of antimicrobial usage and resistance trends

We report a pilot study comparing antimicrobial usage and antimicrobial resistance trends for prominent nosocomial pathogens between 1994-1996. A convenience sample of ten hospitals participated in this retrospective review. We found a large variation in antimicrobial use and resistance trends and that many hospitals did not have data readily available to evaluate drug usage and resistance rates. A significant strong positive correlation was observed between the usage of ceftazidime and the prevalence of ceftazidime resistant Pseudomonas aeruginosa (r = 0.8, p = 0.005) and of ceftazidime resistant Enterobacter species (r = 0.8, p = 0.02). The presence of antibiotic control policies correlated with lower rates of some resistant strains and less antibiotic use. Our findings can be a useful starting point for hospitals that want to systematically measure antimicrobial use and resistance. Hospital laboratories, pharmacies, and infection control departments must work together to develop databases that will facilitate such measurements.

Methodological principles of case-control studies that analyzed risk factors for antibiotic resistance: a systematic review

Case-control studies that analyze the risk factors for antibiotic-resistant organisms have varied epidemiological methodologies, which may lead to biased estimates of antibiotic risk factors. A systematic review of case-control studies that analyzed risk factors for antibiotic-resistant organisms addressed 3 methodological principles: method of control group selection, adjustment for time at risk, and adjustment for comorbid illness. A total of 406 abstracts were reviewed. Thirty-seven studies met the inclusion and exclusion criteria and were reviewed and evaluated for the 3 methodological principles. Thirteen (35%) of 37 studies chose the preferred control group. Eleven adjusted for time at risk. Twenty-seven adjusted for comorbid illness. Future studies need to consider more closely the optimization of control group selection, adjusting for confounding caused by time at risk, and adjusting for confounding caused by comorbid illness.

Implementation of strategies to control antimicrobial resistance

Antimicrobial resistance has emerged as a major public health issue in recent years. A steady increase in resistance continues despite the introduction of new antibiotics, and resistant bacteria have been associated with increased patient morbidity and mortality as well as with increased costs. Addressing the problem of antimicrobial resistance requires both infection control and regulation of antibiotic use; addressing either alone is insufficient. Mounting evidence shows that control of the use of broad-spectrum antibiotics (especially vancomycin and third-generation cephalosporins) and implementation of infection control measures can result in decreased incidence of antibiotic-resistant bacteria such as vancomycin-resistant enterococci and extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella. Recent reports from professional organizations and a consensus of experts have outlined strategies for the control of resistance in hospitals, with specific measures identified for antibiotic control and infection control. These reports have emphasized the importance of a multidisciplinary approach in tackling this problem in hospitals and have suggested that a quality-improvement model be used to address antimicrobial resistance. A close collaboration among the disciplines of infectious diseases, microbiology, hospital epidemiology, pharmacy, and nursing, with particular emphasis in ICUs, and with strong support from hospital leadership, can result in an effective program that can be readily incorporated into the quality-improvement goals of any health-care organization.

Antibiotic utilization: is there an effect on antimicrobial resistance?

The antimicrobial resistance problem in hospitals continues to worsen. In particular, extended-spectrum beta-lactamase-producing Klebsiella pneumoniae (ESBL-KP) and vancomycin-resistant enterococci (VRE) are significant causes of morbidity and mortality among critically ill patients. Treating infections caused by these pathogens presents therapeutic dilemmas. The association between broad-spectrum beta-lactam overutilization and selection for ESBL-KP has been appreciated for some time; several institutions have reported a decrease in the prevalence of ESBL-KP with a shift in antibiotic utilization from third-generation cephalosporins to other broad-spectrum drugs. Currently, optimal treatment of ESBL-KP includes the carbapenems, but widespread use of these drugs is expensive and may be associated with further selection of antibiotic resistance and/or superinfection with other inherently resistant pathogens. VRE are especially difficult organisms to treat because of their inherent and acquired resistance to most currently available antibiotics. The prevalence of VRE has also been documented to decrease upon a shift in antibiotic use from third-generation cephalosporins to broad-spectrum antibiotics of other classes. Thus, antibiotic utilization measures appear to contribute to the control of the emergence of multidrug-resistant pathogens such as ESBL-KP and VRE.

Vancomycin-resistant enterococci

After they were first identified in the mid-1980s, vancomycin-resistant enterococci (VRE) spread rapidly and became a major problem in many institutions both in Europe and the United States. Since VRE have intrinsic resistance to most of the commonly used antibiotics and the ability to acquire resistance to most of the current available antibiotics, either by mutation or by receipt of foreign genetic material, they have a selective advantage over other microorganisms in the intestinal flora and pose a major therapeutic challenge. The possibility of transfer of vancomycin resistance genes to other gram-positive organisms raises significant concerns about the emergence of vancomycin-resistant Staphylococcus aureus. We review VRE, including their history, mechanisms of resistance, epidemiology, control measures, and treatment.

Antimicrobial use and bacterial resistance

The current epidemic of bacterial resistance is attributed, in part, to the overuse of antibiotics. Recent studies have documented increases in resistance with over-use of particular antibiotics and improvements in susceptibility when antibiotic use is controlled. The most effective means of improving use of antibiotics is unknown. Comprehensive management programs directed by multi-disciplinary teams, computer-assisted decision-making, and antibiotic cycling have been beneficial in controlling antibiotic use, decreasing costs without impacting patient outcomes, and possibly decreasing resistance.

Vancomycin-resistant enterococci

After they were first identified in the mid-1980s, vancomycin-resistant enterococci (VRE) spread rapidly and became a major problem in many institutions both in Europe and the United States. Since VRE have intrinsic resistance to most of the commonly used antibiotics and the ability to acquire resistance to most of the current available antibiotics, either by mutation or by receipt of foreign genetic material, they have a selective advantage over other microorganisms in the intestinal flora and pose a major therapeutic challenge. The possibility of transfer of vancomycin resistance genes to other gram-positive organisms raises significant concerns about the emergence of vancomycin-resistant Staphylococcus aureus. We review VRE, including their history, mechanisms of resistance, epidemiology, control measures, and treatment.

[Effects of restrictions on use of vancomycin in a German university hospital]

BACKGROUND

Recently, increasing antibiotic resistance has been observed among gram-positive bacteria. However, only few isolates were found to be resistant against glycopeptides. Therefore, internationally accepted guidelines recommend a restricted use of vancomycin and other glycopeptide antibiotics in order to prevent the development of resistance against these clinically important antibiotics. In many countries, the hospital pharmacies play a key role in control and reinforcement of antibiotic formulary restrictions. In Germany, however, the hospital pharmacies usually do not take over such control functions, and most wards keep a stock of regularly used drugs including antibiotics, which makes reinforcement of restrictions difficult.

METHODS

In an attempt to achieve a restriction of vancomycin use, the pharmacy of our university hospital was advised to deliver vancomycin to the wards only on request with a special order form signed by an attending, individually for every patient who should receive vancomycin. The efficacy of this restriction measure was evaluated in 3-month periods before and after the restriction became effective.

RESULTS

Hospitalwide, this led to a 20.1% reduction of i.v. vancomycin and an 85.7% reduction of oral vancomycin use per 1000 patient days. If the hematology/oncology units were not considered, the reduction of i.v. vancomycin use was 41.8%, and the total use after the restriction 24.2 g per 1000 patient days. Microbiology results which justified the use of vancomycin decreased by 8.3% (10.9% hematology/oncology units not considered) between the 2 observation periods. Assuming a 7-day mean course of i.v. vancomycin therapy, the empirical use of i.v. vancomycin decreased from 39.9% to 8% after the restriction had been instituted.

CONCLUSION

Allowing only experienced physicians (attendings) to decide on the use of vancomycin therapy, proved in our experience to be an effective measure to reduce unnecessary vancomycin use.

Epidemiology and microbiology of surgical wound infections

This study included 676 surgery patients with signs and symptoms indicative of wound infections, who presented over the course of 6 years. Bacterial pathogens were isolated from 614 individuals. A single etiologic agent was identified in 271 patients, multiple agents were found in 343, and no agent was identified in 62. A high preponderance of aerobic bacteria was observed. Among the common pathogens were Staphylococcus aureus (191 patients, 28.2%), Pseudomonas aeruginosa (170 patients, 25.2%), Escherichia coli (53 patients, 7.8%), Staphylococcus epidermidis (48 patients, 7.1%), and Enterococcus faecalis (38 patients, 5.6%).

Antibiotic use in humans and bacterial resistance

As with any public health problem, the evolution of antibacterial resistance must be viewed from a perspective of risk, and analysed in terms of probabilities within the populations. It is necessary to be able to predict the risk of antibacterial resistance, in the future, and two main strategies have recently been developed in mathematical models that may help to evaluate these risks. It is also important to understand how antibiotics are used and how their use affects the evolution of antibacterial resistance. Understanding the epidemiology of antibacterial resistance will enable us to develop preventive strategies to limit existing resistance and to avoid the emergence of new strains of resistant bacteria.