Successful interventions for gram-negative resistance to extended-spectrum beta-lactam antiobiotics

Phenotype, molecular characterisation and risk factors for postoperative meningitis caused by ESBL-producing-Enterobacteriaceae: a six years multi-Centre comparative cohort study

BACKGROUND

To determine the phenotype, molecular characterisation and risk factors of postoperative meningitis induced by Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae (EPE) in China.

METHODS

We performed a multi-centre comparative cohort study of postoperative meningitis patients infected with Enterobacteriaceae in 4 neurosurgical centres in China from January 2014 to December 2019. Phenotype and molecular characteristics of the isolates were reviewed and tested, and independent risk factors of the EPE meningitis were evaluated by binary logistic regression.

RESULTS

In total, 220 Enterobacteriaceae include 78 EPE were available in this study. 85.6% (67/78) ESBL-related genes were tested, and blaSHV (14.9%) and blaSHV + blaTEM + blaCTX-M-9 (20.9%) were found to be the most frequent mono and combined ESBL-related genes harboured by Enterobacteriaceae. On binary logistic analysis, craniotomy (OR. 2.583, 95% C.I. 1.274-5.235, P = 0.008) and malignancy (OR. 2.406, 95% C.I. 1.299-4.456, P = 0.005) were the associated independent risk factors to meningitis induced by EPE.

CONCLUSIONS

To the best of our knowledge, this is the largest series focusing on risk factors of EPE meningitis which has been conducted in China. Craniotomy and malignancy were independent risk factors for EPE meningitis. The risk factors identified may be further utilized in clinical practice and research to avoid and reduce the mortality in future.

Incidence of Extended-Spectrum β-Lactamase (ESBL)-Producing Escherichia coli and Klebsiella Infections in the United States: A Systematic Literature Review

BACKGROUND

Despite a reported worldwide increase, the incidence of extended-spectrum β-lactamase (ESBL) Escherichia coli and Klebsiella infections in the United States is unknown. Understanding the incidence and trends of ESBL infections will aid in directing research and prevention efforts.

OBJECTIVE

To perform a literature review to identify the incidence of ESBL-producing E. coli and Klebsiella infections in the United States.

DESIGN

Systematic literature review.

METHODS

MEDLINE via Ovid, CINAHL, Cochrane library, NHS Economic Evaluation Database, Web of Science, and Scopus were searched for multicenter (≥2 sites), US studies published between 2000 and 2015 that evaluated the incidence of ESBL-E. coli or ESBL-Klebsiella infections. We excluded studies that examined resistance rates alone or did not have a denominator that included uninfected patients such as patient days, device days, number of admissions, or number of discharges. Additionally, articles that were not written in English, contained duplicated data, or pertained to ESBL organisms from food, animals, or the environment were excluded.

RESULTS

Among 51,419 studies examined, 9 were included for review. Incidence rates differed by patient population, time, and ESBL definition and ranged from 0 infections per 100,000 patient days to 16.64 infections per 10,000 discharges and incidence rates increased over time from 1997 to 2011. Rates were slightly higher for ESBL-Klebsiella infections than for ESBL-E. coli infections.

CONCLUSION

The incidence of ESBL-E. coli and ESBL-Klebsiella infections in the United States has increased, with slightly higher rates of ESBL-Klebsiella infections. Appropriate estimates of ESBL infections when coupled with other mechanisms of resistance will allow for the appropriate targeting of resources toward research, drug discovery, antimicrobial stewardship, and infection prevention.

Infect Control Hosp Epidemiol 2017;38:1209–1215

Phenotypic and molecular characterization of nosocomial K. pneumoniae isolates by ribotyping

PURPOSE

To characterize clinical isolates of Klebsiella pneumoniae by phenotypic and genotypic methods.

MATERIAL/METHODS

Over a 12-month period, 52 isolates of K. pneumoniae were isolated. Of these 52 isolates, 7 were isolated over a period of 21 days from a suspected outbreak in the Neonatal Intensive Care Unit (NICU) and 45 from sporadic cases occurring in different wards of hospital were analysed.

RESULTS

The prevalence of K. pneumoniae isolates was 4% (52/1295). Quinolones, aztreonam and amikacin showed the greatest efficacy showing >85% sensitivity. Of the 52 isolates of K. pneumoniae, 8 (15.4%) isolates were positive for ESBL-production. Among the ESBL-producing K. pneumoniae, two out of 8 (25%) and 6 out of 8 (75%) were positive for (bla)SHV and (bla)CTX-M genes respectively. Ribotyping identified 30 distinct ribogroups among 52 isolates evaluated. Seven NICU outbreak isolates were divided into 2 ribotypes, as many as 6 belonged to one ribotype while one isolate which was isolated a week later was of a different ribotype, indicating the termination of the outbreak in the NICU. The outbreak in the NICU thus, was shown to have been caused by a single clone.

CONCLUSIONS

A high discriminatory power, ease of interpretation coupled with excellent reproducibility and stability make ribotyping a very useful technique for investigating the molecular epidemiology of nosocomial infections caused by K. pneumoniae. A regular surveillance of hospital associated infections including monitoring antibiotic sensitivity pattern of K. pneumoniae, ESBL-production and molecular characterization is mandatory to control the spread of multidrug-resistant and ESBL-producing K. pneumoniae and for epidemiological purposes especially in outbreak situations.

An observational study on bloodstream extended-spectrum beta-lactamase infection in critical care unit: incidence, risk factors and its impact on outcome

BACKGROUND

The incidence of nosocomial infections caused by extended-spectrum beta-lactamase (ESBL) producing microbes is increasing rapidly in the last few years. However, the clinical significance of infections caused by ESBL-producing bacteria in ICU patients remains unclear. We did a prospective study to look for incidence, risk factors and outcome of these infections in ICU patients.

METHODS

Consecutive isolates of Escherichia coli and Klebsiella pneumoniae in blood cultures were included for the analysis. Patients were divided into two groups based on the production of ESBL. Primary outcome measure was ICU mortality. Logistic regression analysis was done to identify risk factors for ESBL production.

RESULTS

Among the 95 isolates tested, 73 (76.8%) produced ESBL. Transfer from other hospitals or wards (OR 3.65; 95% CI: 1.3-10.1 and RR 1.35; 95% CI: 1.05-1.73) and previous history of antibiotics usage (OR 3.54; 95% CI: 1.04-11.97 and RR 1.5; 95% CI: 0.89-2.5) were risk factors for ESBL production. There was no significant difference in ICU mortality (p=0.588), need for organ support between two groups.

CONCLUSION

There is a high incidence of ESBL producing organisms causing blood stream infections in critically ill patients. Transfer from other hospitals and previous antibiotic usage are important risk factors for ESBL production. However ESBL production may not be associated with a poorer outcome if appropriate early antibiotic therapy is instituted.

Prevalence and characterization of extended spectrum β-lactamases in Klebsiella-Enterobacter-Serratia group bacteria, in Algeria

OBJECTIVES

The authors had for aim to assess the local epidemiology, antibiotic resistance, and molecular typing of expanded spectrum betalactamase producing Klebsiella, Enterobacter, and Serratia (ESBL KES).

MATERIALS AND METHODS

Two hundred and seven strains of the KES group were isolated in the microbiology laboratory of the Annaba Ibn Rochd hospital in 2009. The antibiotic resistance (diffusion method and MIC) was tested and ESBL detection was performed as recommended by the Clinical Laboratory Standard Institute (CLSI). The characterization of genes for resistance to β-lactams (CTX-M-1, TEM, and SHV) and AmpC cephalosporinase (DHA-1) was performed by polymerase chain reaction. The epidemiological relationship among identified strains was analyzed by Pulsed Field Gel Electrophoresis (PFGE). Genetic transfers were performed by conjugation using sodium azide resistant Escherichia coli K(12)J(5) as recipient strain.

RESULTS

The overall incidence of ESBL KES was 31.4% (65/207) distributed as follows: 17.4% of Klebsiella spp., 7.2% Enterobacter spp., and 6.8% Serratia marcescens. The β-lactamase CTX-M 1 types were predominant (88%), followed by TEM (36.5%), and SHV (31.1%). Twenty-three strains expressed at least two bla genes. DHA-1 type cephalosporinase was found in 4 E. cloacae associated with CTX-M-1. Several epidemic clones were determined. Conjugation experiments showed that bla(CTX-M), bla(TEM), and bla(SHV) were carried by conjugative plasmids of high molecular weight (≥125kb).

CONCLUSIONS

This study revealed a high frequency of ESBL KES with a predominance of CTX-M-1. This high rate of ESBLs could be due to a clonal spread and the emergence of new epidemic clones.

In vitro antimicrobial activity of ten medicinal plants against clinical isolates of oral cancer cases

Background

Suppression of immune system in treated cancer patients may lead to secondary infections that obviate the need of antibiotics. In the present study, an attempt was made to understand the occurrence of secondary infections in immuno-suppressed patients along with herbal control of these infections with the following objectives to: (a) isolate the microbial species from the treated oral cancer patients along with the estimation of absolute neutrophile counts of patients (b) assess the in vitro antimicrobial activity medicinal plants against the above clinical isolates.

Methods

Blood and oral swab cultures were taken from 40 oral cancer patients undergoing treatment in the radiotherapy unit of Regional Cancer Institute, Pt. B.D.S. Health University,

Rohtak, Haryana. Clinical isolates were identified by following general microbiological, staining and biochemical methods. The absolute neutrophile counts were done by following the standard methods. The medicinal plants selected for antimicrobial activity analysis were Asphodelus tenuifolius Cav., Asparagus racemosus Willd., Balanites aegyptiaca L., Cestrum diurnum L., Cordia dichotoma G. Forst, Eclipta alba L., Murraya koenigii (L.) Spreng. , Pedalium murex L., Ricinus communis L. and Trigonella foenum graecum L. The antimicrobial efficacy of medicinal plants was evaluated by modified Kirby-Bauer disc diffusion method. MIC and MFC were investigated by serial two fold microbroth dilution method.

Results

Prevalent bacterial pathogens isolated were Staphylococcus aureus (23.2%), Escherichia coli (15.62%), Staphylococcus epidermidis (12.5%), Pseudomonas aeruginosa (9.37%), Klebsiella pneumonia (7.81%), Proteus mirabilis (3.6%), Proteus vulgaris (4.2%) and the fungal pathogens were Candida albicans (14.6%), Aspergillus fumigatus (9.37%). Out of 40 cases, 35 (87.5%) were observed as neutropenic. Eight medicinal plants (A. tenuifolius, A. racemosus, B. aegyptiaca, E. alba, M. koenigii, P. murex R. communis and T. foenum graecum) showed significant antimicrobial activity (P < .05) against most of the isolates. The MIC and MFC values were ranged from 31 to 500 μg/ml. P. aeruginosa was observed highest susceptible bacteria (46.6%) on the basis of susceptible index.

Conclusion

It can be concluded that treated oral cancer patients were neutropenic and prone to secondary infection of microbes. The medicinal plant can prove as effective antimicrobial agent to check the secondary infections in treated cancer patients.

Antimicrobial activity of cefepime tested against ceftazidime-resistant Gram-negative clinical strains from North American Hospitals: report from the SENTRY Antimicrobial Surveillance Program (1998-2004)

To assess the effect of ceftazidime resistance on the activity of other antimicrobial agents, 3030 ceftazidime-resistant Gram-negative bacilli (GNB) isolates (of a total of 42061 GNB) were tested against a panel of more than 30 agents. Ceftazidime resistance was observed in 40.3% of Acinetobacter spp., 16.9% of Pseudomonas aeruginosa, and 5.7% of Enterobacteriaceae isolates. The highest rates of ceftazidime resistance among the enteric GNB were observed with Enterobacter spp. (20.9%) >Citrobacter spp. (15.3%) > indole-positive Proteae (10.1%). Overall, 90% of ceftazidime-resistant Enterobacteriaceae and 30% of ceftazidime-resistant P. aeruginosa remained susceptible to the "4th-generation" cephalosporin, cefepime. The activities (% susceptible) of other antimicrobials tested against ceftazidime-resistant Enterobacteriaceae and P. aeruginosa, respectively, were as follows: amikacin, 90% and 88%; ciprofloxacin, 63% and 46%; gentamicin, 59% and 67%, imipenem, 99% and 65%; levofloxacin, 69% and 44%; and piperacillin/tazobactam only 40% and 12%. Ceftazidime-resistant GNB exhibited high rates of resistance to other antimicrobials. Cefepime was very active against ceftazidime-resistant enteric GNB (AmpC enzyme producers), especially Enterobacter spp. (94.3% susceptible), Citrobacter spp. (96.7% susceptible), and indole-positive Proteae (89.6% susceptible), and showed activity similar to that of ceftazidime against all P. aeruginosa and Acinetobacter spp. isolated in North American medical centers. Continued resistances surveillance monitoring will be necessary to assess the effectiveness of widely used broad-spectrum antimicrobials as novel resistance mechanisms emerge.

The use of piperacillin/tazobactam (in association with amikacin) in neonatal sepsis: efficacy and safety data

Piperacillin/tazobactam (P/T) has been used in NICU since 1999 as part of the empirical treatment for presumed sepsis. We studied the microbiological and clinical efficacy and safety of P/T use in newborns with sepsis, using a retrospective analysis of medical records of all newborns treated with P/T (in association with amikacin) during 1999-2003. P/T plus amikacin was used for 353 episodes of presumed sepsis occurring in 252 newborns: 105 episodes occurred in 100 newborns treated for 5-14 d while in 248 (70%) episodes the treatment was discontinued after 2-3 d. 123 pathogens were isolated from the blood cultures (40 in the 5-14 d group and 83 in those treated for 2-3 d only). There were 56 Gram-negative, 55 Gram-positive and 12 Candida spp. isolates. Klebsiella spp. (40%) and E. coli (30%) were the most commonly isolated Gram-negative pathogens; coagulase-negative Staphylococcus (CONS) represented 95% of the Gram-positive pathogens isolated. Pathogen eradication was achieved within 48-72 h of therapy in 93% Gram-negative organisms. There were no clinical, laboratory or cranial ultrasound adverse effects associated with P/T use. We conclude that P/T in association with amikacin is microbiologically and clinically efficacious and safe in the treatment of sepsis in newborns.

Treatment and control of severe infections caused by multiresistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the leading causes of nosocomial infections. Severe infections, such as pneumonia or bacteraemia, are associated with high mortality rates and are often difficult to treat, as the repertoire of useful anti-pseudomonal agents is limited (some beta-lactams, fluoroquinolones and aminoglycosides, and the polymyxins as last-resort drugs); moreover, P. aeruginosa exhibits remarkable ability to acquire resistance to these agents. Acquired resistance arises by mutation or acquisition of exogenous resistance determinants and can be mediated by several mechanisms (degrading enzymes, reduced permeability, active efflux and target modification). Overall, resistance rates are on the increase, and may be different in different settings, so that surveillance of P. aeruginosa susceptibility is essential for the definition of empirical regimens. Multidrug resistance is frequent, and clinical isolates resistant to virtually all anti-pseudomonal agents are increasingly being reported. Monotherapy is usually recommended for uncomplicated urinary tract infections, while combination therapy is normally recommended for severe infections, such as bacteraemia and pneumonia, although, at least in some cases, the advantage of combination therapy remains a matter of debate. Antimicrobial use is a risk factor for P. aeruginosa resistance, especially with some agents (fluoroquinolones and carbapenems), and interventions based on antimicrobial rotation and restriction of certain agents can be useful to control the spread of resistance. Similar measures, together with the prudent use of antibiotics and compliance with infection control measures, are essential to preserve the efficacy of the currently available anti-pseudomonal agents, in view of the dearth, in the near future, of new options against multidrug-resistant P. aeruginosa strains.

Prevalence and antimicrobial susceptibility of extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in a general hospital

BACKGROUND

The prevalence of extended-spectrum beta-lactamases (ESBLs) varies between countries and institutions. We studied the prevalence of ESBL among clinical isolates of Escherichia coli and Klebsiella pneumoniae and analyzed patterns of susceptibilities to different antimicrobial agents in a general hospital in Saudi Arabia over a 15-month period.

METHODS

A total of 2455 clinical isolates of E. coli and K. pneumoniae were tested for ESBL production by double-disk diffusion. The minimum inhibitory concentration to imipenem, meropenem, piperacillin-tazobactam, cefepime, ciprofloxacin, gentamicin and amikacin were determined by the agar dilution method.

RESULTS

Of the 2455 isolates of E. coli and K. pneumoniae tested, 268 (11%) produced ESBL. The ESBL phenotype was detected in 10.3% of 1674 E. coli isolates and 12.2% of 781 K. pneumoniae isolates. The majority of these isolates were from urine (57.5%) and wounds (17%). Only 7% of the blood culture isolates were ESBL-producing. Overall, carbapenems (imipenem and meropenem) had good activity against the ESBL-producing isolates tested (over 92% of isolates were susceptible). There was no difference in the activity of imipenem and meropenem against the ESBL-producing E. coli or K. pneumoniae. Over 66% of the isolates were susceptible to piperacillin-tazobactam. Susceptibilities of the isolates to amikacin varied, ranging from 72.8% for E. coli to 62% for K. pneumoniae. Gentamicin, ciprofloxacin and cefepime were active against 58.6%, 55% and 22.8% of the isolates, respectively.

CONCLUSION

Our findings demonstrate the increasing incidence of infection with ESBL-producing bacteria, and the high rates of antimicrobial resistance encountered among them. Clinicians should be familiar with the clinical importance of these enzymes and potential strategies for dealing with them.

Fluoroquinolones protective against cephalosporin resistance in gram-negative nosocomial pathogens

In a matched case-control study, we studied the effect of prior receipt of fluoroquinolones on isolation of three third-generation cephalosporin-resistant gram-negative nosocomial pathogens. Two hundred eighty-two cases with a third-generation cephalosporin-resistant pathogen (203 with Enterobacter spp., 50 with Pseudomonasaeruginosa, and 29 with Klebsiellapneumoniae) were matched on length of stay to controls in a 1:2 ratio. Case-patients and controls were similar in age (mean 62 years) and sex (54% male). Variables predicting third-generation cephalosporin resistance were surgery (p = 0.005); intensive care unit stay (p < 0.001); and receipt of a β-lactam/β-lactamase inhibitor (p < 0.001), a ureidopenicillin (p = 0.002), or a third-generation cephalosporin (p < 0.001). Receipt of a fluoroquinolone was protective against isolation of a third-generation cephalosporin-resistant pathogen (p = 0.005). Interventional studies are required to determine whether replacing third-generation cephalosporins with fluoroquinolones will be effective in reducing cephalosporin resistance and the effect of such interventions on fluoroquinolone resistance.

Risk factors for the development of extended-spectrum beta-lactamase-producing bacteria in nonhospitalized patients

Although the risk factors for acquiring infection by extended-spectrum beta-lactamase (ESBL)-producing bacteria have been investigated in hospitalized patients, such risk factors have not been defined in the community setting. In this study, clinical data from a total of 311 nonhospitalized patients with community-acquired urinary tract infection (128 with ESBL-positive strains and 183 with ESBL-negative strains) were obtained. According to a multivariate analysis, the following were identified as independent risk factors: previous hospitalization in the past 3 months (OR=8.95, 95%CI, 3.77-21.25), antibiotic treatment in the past 3 months (OR=3.23, 95%CI, 1.76-5.91), age over 60 years (OR=2.65, 95%CI, 1.45-4.83), diabetes (OR=2.57, 95%CI, 1.20-5.51), male gender (OR=2.47, 95%CI, 1.22-5.01), Klebsiella pneumoniae infection (OR=2.31, 95%CI, 1.17-4.54), previous use of third-generation cephalosporins (P=0.014, OR=15.8, 95%CI, 1.7-143), previous use of second-generation cephalosporins (P<0.0001, OR=10.1, 95%CI, 4.2-24), previous use of quinolones (P=0.001, OR=4.1, 95%CI, 1.8-9.0), and previous use of penicillin (P=0.003, OR=4.0, 95%CI, 1.6-9.0).

Bacterial resistance: origins, epidemiology, and impact

The basic mechanisms of antibacterial resistance are well known, but critical new aspects continue to be discovered. Recently discovered factors with major implications for the emergence, dissemination, and maintenance of resistance include multidrug efflux, hypermutability, integrons, and plasmid addiction. Some resistances are widespread and others local, with prevalence rates often worst in newly prosperous countries and in those specialist units where antibacterial use is heaviest. Multidrug-resistant epidemic strains are critical to the total accumulation of resistance (e.g., among Streptococcus pneumoniae, methicillin-resistant Staphylococcus aureus, Klebsiella pneumoniae), but it remains unclear why some bacterial lineages achieve epidemic spread whereas others that are equally resistant do not. The correlation between in vitro resistance and treatment failure is imperfect, but resistance undoubtedly increases mortality, morbidity, and costs in many settings. Recent concern has led to a plethora of governmental and agency reports advocating less antibacterial use, better antibacterial use, better infection control, and the development of new antibacterials. The evidence that better prescribing can reduce resistance rates is mixed, and although changes to hospital regimens may reduce one resistance problem, other opportunistic bacteria may fill the vacant niche. Overall, the best that can reasonably be anticipated is an improved balance between the accumulation of resistance and new antibacterial development.

Antimicrobial activity of broad-spectrum agents tested against Gram-negative bacilli resistant to ceftazidime: report from the SENTRY Antimicrobial Surveillance Program (North America, 2001)

To assess the effect of ceftazidime resistance on the activity of other antimicrobial agents, 4,175 Gram-negative bacilli isolates, designated as ceftazidime-susceptible (3,759, 90%) or -resistant (416, 10%) were tested against a panel of nine agents. Cefepime was the most active of the agents tested, against both ceftazidime-susceptible and -resistant isolates, with a particularly low incidence (0.3%, 10/3152 isolates) of resistance among the Enterobacteriaceae. Tobramycin had the best activity against Pseudomonas aeruginosa and ticarcillin/clavulanate was the least active of the tested agents. This study confirms the need for constant monitoring of in vitro antimicrobial efficacy to direct empiric treatment regimens.

A decade of antimicrobial susceptibilities at the University of Kentucky Hospital

OBJECTIVE

To determine the antimicrobial susceptibility rates for key antimicrobial agents and selective bacterial pathogens in the decade of the 1990s.

METHODS

Data from 1990 to 2000 from the University of Kentucky Clinical Microbiology Laboratory were analyzed by linear regression analysis to identify agents and pathogens that show a decline in susceptibility. For selected pathogens and antimicrobial agents, predictions were made for further declines in susceptibility for 2005 and 2010.

RESULTS

Significant declines in susceptibility to selected antimicrobial agents were found for Pseudomonas aeruginosa, Klebsiella pneumoniae, Enterobacter cloacae, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus pneumoniae. Further declines were predicted for 2005 and 2010.

CONCLUSIONS

Examination of susceptibility rates over time in a university hospital medical center provides useful data for future planning. In our institution, antimicrobial susceptibility rates have significantly declined during the 1990s for certain antimicrobial agents and bacterial pathogens. We are attempting to change our antimicrobial use patterns through formulary manipulation and clinician education, which may retard or prevent such declines in the future.

Extended-Spectrum β-Lactamase Resistance in the ICU

Despite the recent focus on gram-positive infections in the intensive care unit (ICU), gram-negative resistance mechanisms continue to challenge the critical care practitioner. A recent national surveillance study of United States ICUs found Escherichia coli, Enterbacter species, Klebsiella species, and Pseudomonas aeruginosa represented 72% of all gram-negative bacilli recovered. E coli, Klebsiella pneumoniae, and Enterobacter species are significant producers of a β -lactamase that inactivates almost all β -lactam antibiotics, so-called extended-spectrum β -lactamases or ESBLs. Many clinical laboratories may not test for ESBL-production in these organisms, thus clinicians may be unaware of the rising incidence of this plasmid-mediated resistance mechanism. Since initial reports of ESBLs in the 1980s, investigators have found an association with ESBL-producing organisms and the critically ill population. Risk factors for ESBL-related infection in the ICU include arterial, central-venous, and urinary-catheters; mechanical ventilation; abdominal surgery; prior antibiotic therapy with ceftazidime or other extended spectrum cephalosporins; length of time in the ICU; and overall acuity of illness. This article reviews the emergence and epidemiology of the ESBL evolution, describes the clinical implications of ESBL production in the ICU, and outlines a strategy for management of infection in patients at risk for ESBL-producing organisms.

Extended-spectrum beta-lactamases: frequency, risk factors, and outcomes

STUDY OBJECTIVE

To determine epidemiologic factors of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli or Klebsiella pneumoniae in a nonoutbreak setting.

DESIGN

Retrospective analysis.

SETTING

University teaching hospital.

PATIENTS

Fifty-seven patients with cultures of presumed ESBL-producing (i.e., ceftazidime-resistant) E. coli or K. pneumoniae.

INTERVENTIONS

To determine overall frequency, institutional antibiograms from 1991-1999 were examined for percentage of isolates with ceftazidime resistance. Medical records from January 1997-June 2000 were reviewed for patient demographics, comorbidities, culture site, antimicrobial therapy, and clinical and microbiologic outcomes.

MEASUREMENTS AND MAIN RESULTS

From 1991-1999, frequency increased from undetectable to 4% for ceftazidime-resistant E. coli and from 2% to 6% for ceftazidime-resistant K. pneumoniae. Seventy-one isolates were identified in the 57 patients with presumed ESBL-producing E. coli or K. pneumonia. Fifty-one isolates (72%) were E. coli, with urine the primary site of infection (62%). Eighty-six percent of patients had known risk factors for infection due to ESBL-producing organisms, including hospitalization (37 patients) and residence in long-term care facilities (12 patients). However, in 14% (8 patients), the infection was community acquired in patients who resided at home.

CONCLUSION

In addition to known populations at risk, ambulatory patients with chronic conditions represent another patient population that may harbor ESBL-producing organisms.

Therapeutic challenges associated with extended-spectrum, beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae

The emergence of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae, particularly Escherichia coli and Klebsiella pneumoniae, presents significant diagnostic and therapeutic challenges to the management of infections due to these organisms. Detection of resistant isolates is difficult based on routine susceptibility testing performed by a clinical microbiology laboratory. In addition, the utility of penicillins, cephalosporins, and aztreonam in treating serious infections due to these organisms is uncertain due to reports of treatment failure despite apparent in vitro susceptibility. A critical evaluation of the English literature was performed on treatment outcomes associated with ESBL-producing Enterobacteriaceae. Imipenem and extended-spectrum cephalosporins were commonly administered. Discordant outcomes in relation to in vitro susceptibility of the agent did not occur exclusively with cephalosporins but with all drugs including imipenem. Until more outcome data are available, drug selection must take into consideration whether or not an outbreak is occurring and whether therapy is empirical or definitive.

Extended-spectrum beta-lactamases in the 21st century: characterization, epidemiology, and detection of this important resistance threat

Beta-lactamases continue to be the leading cause of resistance to beta-lactam antibiotics among gram-negative bacteria. In recent years there has been an increased incidence and prevalence of extended-spectrum beta-lactamases (ESBLs), enzymes that hydrolyze and cause resistance to oxyimino-cephalosporins and aztreonam. The majority of ESBLs are derived from the widespread broad-spectrum beta-lactamases TEM-1 and SHV-1. There are also new families of ESBLs, including the CTX-M and OXA-type enzymes as well as novel, unrelated beta-lactamases. Several different methods for the detection of ESBLs in clinical isolates have been suggested. While each of the tests has merit, none of the tests is able to detect all of the ESBLs encountered. ESBLs have become widespread throughout the world and are now found in a significant percentage of Escherichia coli and Klebsiella pneumoniae strains in certain countries. They have also been found in other Enterobacteriaceae strains and Pseudomonas aeruginosa. Strains expressing these beta-lactamases will present a host of therapeutic challenges as we head into the 21st century.

The rise and fall of antimicrobial resistance

Antimicrobial resistance is a growing problem in nearly every infectious disease, but the extent and rate of increase of the problem varies widely with different pathogen-drug combinations. The rate of increase of resistance depends primarily on the availability of resistant variants and the intensity of selection imposed by antimicrobial treatment (appropriately measured). Declines in resistance following antimicrobial control measures are typically faster in hospital-acquired infections than in community-acquired ones, probably owing to the dependence in the latter case on the fitness cost of resistance. Open questions and approaches for testing the hypotheses proposed here are outlined.

Improving inpatient antibiotic prescribing: insights from participation in a national collaborative

BACKGROUND

Increasing rates of antimicrobial resistance and the role antibiotic overuse plays in contributing to this problem have been widely documented and have prompted appeals to change prescribing practices. How to actually achieve such changes represents a major challenge. As part of the Institute for Healthcare Improvement (IHI) Breakthrough Series project Improving Prescribing Practices (IPP), in 1997-1998, Cook County Hospital (Chicago) worked with other institutions that chose antibiotics as their focus in this national collaborative.

PRACTICAL SUGGESTIONS

Practical suggestions are offered within six categories--adopting a general approach to improving antibiotic prescribing (marshalling credible evidence, addressing physician concerns and skepticism, and removing barriers to make it easier for prescribers to change); rethinking guidelines (providing syndrome-based guidance, revising national guidelines for local use, defining scenarios in which drug(s) can be safely withheld, offering alternatives, prospectively resolving conflicts over drug of choice and empiric regimens, and defining situations in which immediate treatment is and is not critical); getting the message out and changes implemented (using antibiotic order forms, computer order entry, and infectious disease specialist consultation); building viable linkages to leverage change (bridging disciplines); improving measurement; and promoting nondrug strategies and patients' roles in treating and preventing infection.

CONCLUSION

Antimicrobials are unique, being the only class of drug therapy that affects not only the patient to whom it is prescribed but other current and future patients as well. Institutions therefore have a special responsibility to ensure their efficient and judicious use. It is often easier to prescribe antibiotics than to exercise restraint.

Susceptibility Patterns of Select Gram-Negative Organisms after a Formulary Switch from Ceftazidime to Cefepime

Objective:

To document changes in susceptibility patterns of gram-negative organisms, including Pseudomonas aeruginosa, Enterobacter aerogenes, Acinetobacter calcoaceticus, and Serratia marcescens after a formulary switch from ceftazidime to cefepime.

Design, Setting:

Retrospective, observational study in a tertiary care, university teaching hospital.

Participants:

Adult surgical patients with culture and susceptibility data.

Main Outcome Measures:

Percent susceptible and median minimum inhibitory concentration values were evaluated for select gram-negative organisms from culture and susceptibility results. The time periods of one year before and two years after the formulary change were evaluated. Duplicate isolates were excluded. Different culture sites of infection were assessed for P. aeruginosa, including blood, urine, and lung.

Results:

A total of 957 samples from 489 patients were included. Susceptibility results after the formulary switch favored ceftazidime over cefepime for P. aeruginosa (79% vs. 54%; n = 485) and A. calcoaceticus (65% vs. 29%; n = 140). However, cefepime demonstrated greater kill rate with E. aerogenes isolates compared with ceftazidime (95% vs. 69%; n = 208). Susceptibility results were comparable with S. marcescens (100% for cefepime vs. 98% for ceftazidime). P. aeruginosa results from isolates taken from different culture sites did not differ from the overall results, as susceptibility was higher for ceftazidime compared with cefepime for all culture sites.

Conclusions:

Susceptibility to cefepime and ceftazidime is organism-specific; therefore, it may be appropriate to include both agents on the formulary and/or implement an antibiotic rotation policy.

Screening of antibiotic resistant inhibitors from local plant materials against two different strains of Pseudomonas aeruginosa

The methanolic extracts of 19 Jordanian plants were combined with seven different antibiotics and applied to check the inhibitory effects of the combination on the resistance of Pseudomonas aeruginosa. A resistant strain of Ps. aeruginosa, which was isolated from a patient and a standard strain of the same microorganism were used in this study. Our results showed that there are significant variations in the effects of some combinations used on the resistant and the standard strains probably due to structural changes. Almost all the plant materials used in combination with penicillin G and erythromycin allowed full growth of the standard strain, while the combination with some plant materials like Gundelia tournefortii L. and Lepidium sativum L. inhibited the growth of the resistant strain. Chloramphenicol, gentamicin and cephalosporin can be given advantageously with almost all the plant materials used with few exceptions on the resistant strain. Nalidixic acid activity was improved significantly when combined with all plant materials and tested on standard strain. On the other hand, its activity on the resistant strain was slightly improved using the same combinations.

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.