Extended spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae: considerations for diagnosis, prevention and drug treatment

Ceftiofur use in finishing swine barns and the recovery of fecal Escherichia coli or Salmonella spp. resistant to ceftriaxone

The objective of this study was to investigate the association between ceftiofur use policy in finishing swine barns and recovery of fecal Escherichia coli or Salmonella spp. resistant to ceftriaxone. The study population included 54 finishing swine barns from three companies located in North Carolina. The barns were each classified according to their reported therapeutic ceftiofur use rates of "Rare," "Moderate," and "Common." Fecal samples from the barns were cultured for the presence of E. coli and Salmonella spp. resistant to ceftriaxone using selective media designed to recover rare organisms expressing the AmpC β-lactamase phenotype. A total of 1899 swine fecal samples yielded 1193 E. coli (63%) resistant to ceftriaxone. Recovery rates by ceftiofur use classification were 45% for Rare, 73% for Moderate, and 68% Common ceftiofur use groups. Barns reporting Rare ceftiofur use had a lower odds of recovery of E. coli (OR=0.32; p<0.001) resistant to ceftriaxone compared to Common use barns. The overall Salmonella spp. prevalence was 63.8% (n=714). Of these, 65 Salmonella were resistant to ceftriaxone with the highest rate (6%) found in the Common ceftiofur use group, followed by Rare (4.1%) and Moderate (0.15%). The odds of recovery of Salmonella resistant to ceftriaxone were similar for barns with ceftiofur use classified as Rare and Common. Samples from barns with ceftiofur use classified as Moderate had a lower odds (OR=0.02; p<0.01) of recovery of Salmonella resistant to ceftriaxone than barns classified as Common. Our result is consistent with the hypothesis that the use of ceftiofur in finishing swine barns, beyond its rare application, may influence the recovery of enteric E. coli with resistance to cephalosporin drugs, although other unmeasured factors appear to be important in the recovery of cephalosporin-resistant Salmonella. The dissemination of enteric bacteria with resistance to cephalosporins has the potential to impact both veterinary and human therapeutic treatment options.

ESBLs: A Clear and Present Danger?

Extended spectrum β-lactamases (ESBLs) are enzymes produced by a variety of Gram negative bacteria which confer an increased resistance to commonly used antibiotics. They are a worrying global public health issue as infections caused by such enzyme-producing organisms are associated with a higher morbidity and mortality and greater fiscal burden. Coupled with increasing prevalence rates worldwide and an ever diminishing supply in the antibiotic armamentarium, these enzymes represent a clear and present danger to public health. This article aims to give an overview of the current situation regarding ESBLs, with a focus on the epidemiology and management of such infections.

Clinical manifestations and prognostic factors in cancer patients with bacteremia due to extended-spectrum β-lactamase-producing Escherichia coli or Klebsiella pneumoniae

BACKGROUND

Clinical information about bacteremia due to extended-spectrum β-lactamase (ESBL)-producing pathogens in cancer patients was limited. The study was aimed to identify the clinical manifestations and risk factors for mortality in ESBL-producer bacteremia in cancer patients.

METHODS

A retrospective study of bacteremia caused by ESBL-producing Escherichia coli or Klebsiella pneumoniae in adults with cancer in National Cheng Kung University Hospital and National Taiwan University Hospital from July 2002 to August 2007 was conducted. Clinical characteristics, initial manifestations, and antimicrobial therapy were analyzed for their association with crude mortality at 14 days after bacteremia onset.

RESULTS

A total 113 episodes of bacteremia caused by E coli (59.3%), K pneumoniae (39.8%) or both (0.9%) were included. Patients with hematological malignancy were younger (55 ± 22 vs. 69 ± 14 years, p < 0.003) and had less co-morbidity, but were more likely to have neutropenia (73.1% vs. 4.6%, p < 0.001) than those with solid tumor. By the univariate analysis in 113 episodes of ESBL-producer bacteremia, several risk factors, including pneumonia or soft-tissue infection as the bacteremia source, initial manifestations with high Pitt bacteremia scores, shock, respiratory failure or severe sepsis, and inappropriate definitive therapy were associated with 14-day crude mortality. By multivariate analysis, only pneumonia [adjusted odds ratio (AOR), 5.2; 95% confident interval (CI), 1.3-21.0; p = 0.021], severe sepsis (AOR, 24.3; 95% CI, 5.6-105.0; p < 0.001), and inappropriate definitive therapy (AOR, 11.3; 95% CI, 1.7-72.8; p = 0.011) were independently associated with a fatal outcome.

CONCLUSION

The presence of neutropenia or underlying hematological malignancy in cancer patients with ESBL-producer bacteremia was not associated with an increase in the mortality rate. Appropriate definitive antimicrobial therapy will be beneficial in improving clinical outcome.

Cirrhotic patients are at risk for health care-associated bacterial infections

BACKGROUND & AIMS

Bacterial infections are a frequent and serious burden among patients with cirrhosis because they can further deteriorate liver function. We assessed the epidemiology, risk factors, and clinical consequences of bacterial infections in hospitalized cirrhotic patients.

METHODS

In a cohort of hospitalized cirrhotic patients (n = 150) referred to a tertiary care setting, all episodes of bacterial infections were recorded prospectively. Infections were classified as community-acquired (CA), health care-associated (HCA), or hospital-acquired (HA). Site of infection, characteristics of bacteria, and prevalence of antibiotic resistance were reported; consequences for liver function and patient survival were evaluated.

RESULTS

Fifty-four infections were observed among 50 patients (12 CA, 22 HCA, and 20 HA). Bacterial resistance was more frequent among patients with HCA or HA infections (64% of isolates). Mortality was 37% from HA, 36% from HCA, and 0% from CA infections. Independent predictors of infection included a previous infection within the past 12 months (P = .0001; 95% confidence interval [CI], 2.2-10.6), model of end-stage liver disease score ≥ 5 (P = .01; 95% CI, 1.3-6.1), and protein malnutrition (P = .04; 95% CI, 1.5-10). Infectious episodes worsened liver function in 62% of patients. Patients with infection more frequently developed ascites, hepatic encephalopathy, hyponatremia, hepatorenal syndrome, or septic shock. Child class C (P = .006; 95% CI, 1.67-23.7), sepsis (P = .005; 95% CI, 1.7-21.4), and protein malnutrition (P = .001; 95% CI, 2.8-38.5) increased mortality among patients in the hospital.

CONCLUSIONS

In hospitalized cirrhotic patients, the most frequent infections are HCA and HA; these infections are frequently resistant to antibiotics. As infections worsen, liver function deteriorates and mortality increases. Cirrhotic patients should be monitored closely for infections.

Infections after primary and revision total hip replacement caused by enterobacteria producing extended spectrum beta-lactamases (ESBL): a case series

Implant infection remains a feared complication after total hip replacement. A higher rate of infection is observed after revision surgery. An additional threat for such patients arises from the fact that bacteria resistant to a multitude of antibiotics are encountered with increasing frequency in the hospital setting. Among them enterobacteria producing extended spectrum beta-lactamases (ESBL) are the second most frequent group of multiresistant isolates. ESBLs are enzymes which hydrolyse third and fourth generation cephalosporins resulting in a distinctive resistance against these antibiotics. Even though ESBLs were first described in the early 1980's and now represent pathogens of importance in intensive care units, they have been only rarely encountered in orthopaedic and trauma surgery. We report on three cases of ESBL-associated infections in hip arthroplasty, resulting in 1) resolution of infection after removal of the hip implant, 2) death after developing a nosocomial pulmonary infection due to ESBL-producing bacteria, and 3) resolution of infection after two-stage revision. The infections, caused by multi-resistant ESBL-producing Escherichia coli and Klebsiella pneumoniae isolates, demonstrate the difficulties in managing implant associated infections with resistant bacteria, and emphasize the importance of recognizing ESBL-positive bacteria as increasingly important pathogens that require special precautions and treatment. Our observations suggest that ESBL-expressing bacteria in orthopaedic and trauma surgery are not a rare phenomenon any more.

Antibiotic optimization in the difficult-to-treat patient with complicated intra-abdominal or complicated skin and skin structure infections: focus on tigecycline

Complicated intra-abdominal and skin and skin structure infections are widely varied in presentation. These infections very often lead to an increase in length of hospital stay, with a resulting increase in costs and mortality. In addition, these infections may be caused by a wide variety of bacteria and are often polymicrobial with the possibility of the presence of antimicrobial-resistant strains, such as methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, extended-spectrum β-lactamase strains (Escherichia coli, Klebsiella pneumoniae), and K. pneumoniae carbapenemase-producing strains. In combination with patients’ immunosuppression or comorbidities, the treatment and management options for initial therapy success are few. Tigecycline, a new glycylcyline antimicrobial from the tetracycline drug class, represents a viable option for the successful treatment of these infections. It has been shown to have activity against a wide variety of bacteria, including the antimicrobial-resistant strains. As with all tetracycline drugs, it is not recommended for pregnant or nursing women. The potential side effects are those typical of tetracycline drugs: nausea, vomiting, and headaches. Drug–drug interactions are not expected, and renal function monitoring is not necessary.

Extended spectrum beta-lactamase-producing bacteria and Clostridium difficile in patients with pouchitis

BACKGROUND

Treatment with fluoroquinolones is associated with the development of Clostridium difficile and extended spectrum beta-lactamase-producing bacteria (ESBL). Clostridium difficile and ESBL are resistant to many antibiotics and each may cause pouchitis after restorative proctocolectomy (RPC) refractory to empirical antibiotic therapy.

AIM

To assess the prevalence and establish risk factors for the development of ESBL and Clostridium difficile toxins (CDT) in RPC patients with recurrent or refractory pouchitis under follow-up at our institution over a 1-year period.

METHOD

An enzyme-linked immunosorbent assay was used to detect CDT and a culture technique was used to identity ESBL in faecal samples. All patients had previously received fluoroquinolone treatment.

RESULTS

Forty-eight patients (35 (74%) men; median age 42 years) underwent testing at a median interval from RPC of 8 (range 1-25) years. No patient had a positive CDT result, but ESBL bacteria were identified in 16 (33%) samples. ESBL positivity was significantly related to prepouch ileitis (P = 0.035) and maintenance antibiotic therapy (P = 0.039).

CONCLUSIONS

Extended spectrum beta-lactamase, but not CDT, is a common finding in faecal samples from patients with recurrent or refractory pouchitis. Treatment with maintenance antibiotics and prepouch ileitis are risk factors for developing ESBL-producing bacteria.

Bacteremia due to extended-spectrum-beta-lactamase-producing Enterobacter cloacae: role of carbapenem therapy

Enterobacter cloacae is an important nosocomial pathogen. However, few studies specifically dealing with the clinical characteristics and outcome of extended-spectrum beta-lactamase (ESBL)-producing E. cloacae infections have been published. During an 8-year period in a medical center, of 610 E. cloacae bacteremic isolates, 138 (22.6%) with ESBL genes were designated the ESBL group, and 120 (19.6%) cefotaxime-nonsusceptible isolates without the ESBL phenotype and genes were designated the control group. Of the former group of isolates, 133 (96.3%) carried the bla(SHV-12) gene, 3 (2.1%) had bla(CTX-M3), and 2 (1.4%) had both the bla(SHV-12) and bla(CTX-M3) genes. After patients under the age of 18 years were excluded, there were 206 adults with E. cloacae bacteremia, and these consisted of 121 patients in the ESBL group and 85 in the control group. More episodes of hospital-onset and polymicrobial bacteremia, increased severity of illness, more cases of bacteremia onset in intensive care units (ICUs), and longer stays in the hospital and ICU after bacteremia onset were noted in the ESBL group. However, the crude and sepsis-related mortality rates in two groups were similar. Of the ESBL group, the in-hospital sepsis-related mortality rate of patients definitively treated by a carbapenem was lower than that of those treated by noncarbapenem beta-lactams (5/53, or 9.4%, versus 13/44, or 29.5%; P = 0.01) though the difference was not significant in the hierarchical multivariate analysis (P = 0.46). Among 62 patients with follow-up blood cultures within 14 days of bacteremia onset, breakthrough bacteremia was more common in those treated by a noncarbapenem beta-lactam agent than in those treated by a carbapenem (18/31, or 58.0%, versus 3/31, or 9.6%; P < 0.001). Thus, carbapenem therapy for ESBL-producing E. cloacae that cause bacteremia may provide therapeutic benefits.

Multidrug resistant gram-negative bacilli as predominant bacteremic pathogens in liver transplant recipients

BACKGROUND

Bacteremias, which are often caused by gram-negative bacteria, are the most frequently occurring infectious complications after liver transplantation (LT). The aim of this study was to investigate bacteremic incidence, pathogenic spectrum, risk factors for bacteremia due to multidrug resistant (MDR) gram-negative bacilli, and its impact on mortality after LT.

METHODS

A cohort analysis of prospectively recorded data was done in 475 LT recipients, who were divided into 3 categories: cases with gram-negative bacteremia, cases with MDR gram-negative bacteremia, and cases without bacteremia as controls.

RESULTS

In 475 LT recipients, there were 152 (32.0%) patients with gram-negative bacillus bacteremia in the first 6 months after LT. Out of 152 patients, there were 225 bacteremic episodes, which accounted for 69.7% in a total 323 bacteremic episodes. A total of 190 bacteremic episodes were caused by Stenotrophomonas maltophilia, Enterobacteriaceae, Ochrobactrum anthropi, Pseudomonas, and Acinetobacter baumanii, all of which were the most frequent gram-negative isolates in this study, and MDR bacilli constituted 56.3%. The most frequent source was intravascular catheters. There were 70 patients with MDR gram-negative bacillus bacteremia. Independent risk factors for bacteremia due to MDR gram-negative bacillus were as follows: post-LT abdominal infection (P<0.0001, odds ratio [OR] 0.066, 95% confidence interval [CI] 0.019-0.226), post-LT reoperative episodes (P<0.0001, OR 10.505, 95% CI 3.055-36.121), or one or more episodes of acute rejection (P=0.042, OR 4.457, 95% CI 0.988-20.103). In the first 6 months after LT, MDR gram-negative bacillus bacteremia-related mortality was significantly higher than that due to antibiotic-susceptible bacillus (38.6% vs. 14.6%, P<0.001).

CONCLUSION

Post-LT bacteremias caused by MDR gram-negative bacilli are common, and associated with allograft acute rejection, post-LT reoperation, and abdominal infection. The increasing isolates of MDR gram-negative bacilli pose a great challenge for clinical treatment.

Hospital-acquired pneumonia: pathophysiology, diagnosis, and treatment

Hospital-acquired pneumonia (HAP) is one of the most common causes of nosocomial infection, morbidity, and mortality in hospitalized patients. Many patient- and disease-specific factors contribute to the pathophysiology of HAP, particularly in the surgical population. Risk-factor modification and inpatient prevention strategies can have a significant impact on the incidence of HAP. While the best diagnostic strategy remains a subject of some debate, prompt and appropriate antimicrobial therapy in patients suspected of having HAP has been shown to significantly decrease mortality. Because the pathogens responsible for HAP are frequently more virulent and have greater resistance to commonly used antimicrobials than other pathogens, clinicians must have knowledge of the resistance patterns at their institutions to choose appropriate therapy.

Update on antimicrobial susceptibility rates among gram-negative and gram-positive organisms in the United States: results from the Tigecycline Evaluation and Surveillance Trial (TEST) 2005 to 2007

BACKGROUND

The Tigecycline Evaluation and Surveillance Trial (TTEST) is a global surveillance study initiated in 2004.Its goal is to assess the in vitro activity of the glycylcycline, tigecycline, and comparator antimicrobials.

OBJECTIVE

The aim of this study was to measure the in vitro activity of a panel of antimicrobial agents against gram-negative and gram-positive organisms collected in the United States in 2005, 2006, and 2007.

METHODS

Isolates were collected from 172 centers across the United States.In vitro activity was assessed using Clinical and Laboratory Standards Institute (CLSI) guidelines and CLSI or US Food and Drug Administration interpretive criteria.

RESULTS

Overall, data on 20,897 gram-negative and 8949 gram-positive isolates were collected. For the majority of organisms, percentage susceptibilities were unchanged over the 3 years of collection. One exception was Acinetobacter baumannii; rates of susceptibility to the majority of agents in the panel decreased by approximately 10% over the 3 years. Rates of resistant phenotypes were relatively unchanged with mean percentages over the 3 years of: 8.9% (337/3787) for extended beta-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae; 2.1% (17/801) for ESBL-producing Klebsiella oxytoca; 2.3% (111/4861) for ESBL-pproducing Escherichia coli; 56.2% (2564/4560) for methicillin-resistant Staphylococcus aureus; 5.1% (97/1903) for vancomycin-resistant Enterococcus faecalis; and 67.2% (487/725) for vancomycin-resistant Enterococcus faecium. The minimum inhibitory concentration required to inhibit the growth of 90% of organisms (MIC(90)) for tigecycline was stable over the 3 years and was < or = 22 mg/L against non-ESBL-producing K pneumoniae, K oxytoca, E coli, Enterobacter aerogenes, Enterobacter cloacae, Serratia marcescens, and A baumannii. Against methicillin susceptible and -resistant S aureus, E faecalis, E faecium, and Streptococcus agalactiae tigecycline MIC(90)s were < or = 0.25 mg/L.

CONCLUSIONS

This report of 3 years of data from the TEST study suggests stable susceptibility rates among gram-negative and gram-positive organisms, with the exception of decreased susceptibility rates for A baumannii. Tigecycline continued to have good activity against Enterobacteriaceae, A baumannii, S aureus, E faecalis, E faecium, and S agalactiae.

“Future” Threat of Gram-negative Resistance in Singapore

The emergence of multidrug-resistant gram-negative bacteria is challenging the treatment of serious nosocomial infections. This is an international trend that is mirrored in Singapore too. Reports of strains resistant to all currently available agents have surfaced here and possibly have taken root here as well. The direst situation is among the non-fermenters, Pseudomonas aeruginosa and Acinetobacter baumannii. This is followed closely by the Enterobacteriaceae family with their array of extended-spectrum β-lactamases, AmpC β-lactamases and carbapenemases. There are also resistance mechanisms such as efflux pumps and porins downregulation that effect resistance against multiple classes of agents. Potentiating these developments is the dwindling “pipeline” of new agents. Hence, there is a real concern that we are running out of options for our patients. Novel antibiotic combinations, enhanced infection control, antibiotic cycling, computer-assisted programmes, and maybe in the distant future, non-antimicrobial agents is all that we have. Key words: Outcomes, Predictors, Stenotrophomonas maltophilia

Occurrence of endemic plasmids causing β-lactam resistance inEnterobacteriaceae in children’s university hospital in Munich

Susceptibility of 62 clinical isolates of Enterobacteriaceae to 15 aminoglycosides, beta-lactams and fluoroquinolones was determined. The isolates originating from 3 intensive care units (neonatal, pediatric, and surgical) and the Department of Infant Internal Medicine of the Children's University Hospital City Center in Munich (Germany) were collected in August 1999, and March and October 2000. Transferability of antibiotic resistance from donors to their E. coli transconjugants was also demonstrated. The majority of isolates were resistant to ampicillin, cefoxitin, ceftriaxone, cefotaxime, ceftazidime and azthreonam but they were susceptible to cefepime, meropenem, aminoglycosides and fluoroquinolones. The occurrence of beta-lactamases and extended-spectrum beta-lactamases (ESBL) was also shown. In August 1999 75% of isolates produced beta-lactamases and 15% ESBL, in March 2000 95% of isolates produced beta-lactamases and 9% ESBL; in October 2000 all isolates produced beta-lactamases and only 5% produced ESBL. Plasmid DNA analysis in randomly chosen isolates and their transconjugants revealed the presence of plasmids ranging from 19 to 136 kb; in the majority of isolates a 120-kb plasmid was observed. Further analysis using restriction endonuclease suggested a dissemination and persistence of an endemic plasmid at all 4 wards of the large pediatric hospital in the City Center of Munich which may be responsible for resistance to beta-lactams among Enterobacteriaceae isolates.

Molecular and descriptive epidemiologyof multidrug-resistant Enterobacteriaceae in hospitalized infants

OBJECTIVE

To investigate the epidemiology of multidrug-resistant Enterobacteriaceae (MDRE) in hospitalized infants.

METHODS

From 2000 through 2005, active surveillance cultures for MDRE were performed for patients admitted to a 40-bed neonatal intensive care unit (NICU) that provides care for critically ill infants 6 months of age or younger. MDRE epidemiology and the genetic relatedness of MDRE strains determined by repetitive-sequence polymerase chain reaction were analyzed.

RESULTS

Active surveillance cultures revealed that 759 (23%) of 3,370 NICU infants (or approximately 1 in 5) developed MDRE colonization or infection and that 613 (72%) of the 853 isolates with epidemiologic data available were healthcare acquired. MDRE colonization occurred more frequently (in 653 infants [86%]) than did MDRE infection (in 106 [14%]). Of the 653 infants with MDRE colonization, 119 (18%) eventually became infected, with 29 (4%) acquiring sterile site infections. The most commonly isolated organisms were the Enterobacter species, accounting for 612 (71%) of the 862 isolates. Molecular epidemiologic analysis revealed that genetic-relatedness clustering (related clusters defined as having a genetic similarity coefficient greater than 95%) varied depending on microbial species. Clustering was detected for 36 (78%) of the 46 Enterobacter aerogenes isolates, 22 (45%) of the 49 Enterobacter cloacae isolates, and 13 (59%) of the 22 Klebsiella pneumoniae isolates.

CONCLUSION

Hospitalized infants are at significant risk of acquiring MDRE, specifically Enterobacter species, at the study institution. Active surveillance cultures identified colonized patients who likely contributed to the institutional reservoir of MDRE. Molecular epidemiologic studies suggest that both patient-to-patient transmission and de novo acquisition of resistance play a role in the acquisition of these organisms, and that the clinical significance of such acquisition varies by species. The high percentage of E. aerogenes isolates that demonstrated genetic clustering suggests that monitoring the prevalence of this organism could serve as a useful measure of compliance with infection control procedures.

An epidemic of plasmids? Dissemination of extended-spectrum cephalosporinases among Salmonella and other Enterobacteriaceae

CTX-M- and AmpC-type beta-lactamases comprise the two most rapidly growing populations among the extended-spectrum cephalosporinases. The evolution and dissemination of resistance genes encoding these enzymes occur mostly through the transmission of plasmids. The high prevalence of clinical isolates of Enterobacteriaceae producing the plasmid-mediated extended-spectrum cephalosporinases resembles an epidemic of plasmids, and has generated serious therapeutic problems. This review describes the emergence and worldwide spread of various classes of plasmid-mediated extended-spectrum cephalosporinases in Salmonella and other Enterobacteriaceae, the transfer mechanism of the plasmids, detection methods, and therapeutic choices.

Ertapenem susceptibility of extended spectrum beta-lactamase-producing organisms

BACKGROUND

Infections caused by multiply drug resistant organisms such as extended spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae are increasing. Carbapenems (imipenem and meropenem) are the antibiotics commonly used to treat these agents. There is limited clinical data regarding the efficacy of the newest carbapenem, ertapenem, against these organisms. Ertapenem susceptibility of ESBL-producing E. coli and K. pneumoniae clinical isolates were evaluated and compared to imipenem to determine if imipenem susceptibility could be used as a surrogate for ertapenem susceptibility.

METHODS

100 ESBL isolates (n = 34 E. coli and n = 66 K. pneumoniae) collected from 2005-2006 clinical specimens at WRAMC were identified and tested for susceptibility by Vitek Legacy [bioMerieux, Durham, NC]. Ertapenem susceptibility was performed via epsilometer test (E-test) [AB Biodisk, Solna, Sweden].

RESULTS

100% of ESBL isolates tested were susceptible to ertapenem. 100% of the same isolates were also susceptible to imipenem.

CONCLUSION

These results, based on 100% susceptibility, suggest that ertapenem may be an alternative to other carbapenems for the treatment of infections caused by ESBL-producing E. coli and K. pneumoniae. Clinical outcomes studies are needed to determine if ertapenem is effective for the treatment of infection caused by these organisms. However, due to lack of resistant isolates, we are unable to conclude whether imipenem susceptibility accurately predicts ertapenem susceptibility.

Susceptibilities of ESBL-Producing Enterobacteriaceae to Ertapenem, Meropenem and Piperacillin-Tazobactam with and without Clavulanic Acid

BACKGROUND

Faced with the extended-spectrum beta-lactamase (ESBL) pandemic, we compared the susceptibilities of ESBL-producing Enterobacteriaceae to ertapenem, meropenem and piperacillin-tazobactam with and without clavulanate.

METHODS

121 strains of Escherichia coli and Klebsiella were studied. 70 strains were originally reported as resistant to ceftazidime based upon disk diffusion; 51 strains were originally reported as sensitive to ceftazidime based upon previous guidelines of the National Committee for Clinical Laboratory Standards, but subsequently shown to be ESBL producers. Minimal inhibitory concentrations (MICs) of the strains towards ertapenem, meropenem and piperacillin-tazobactam were determined by Etest. The effect of adding clavulanate on the MICs was determined by performing the Etest, using plates containing 2 microg/ml of clavulanate.

RESULTS

The MIC90 of all isolates was 0.094 and 0.25 microg/ml for ertapenem, 0.032 and 0.064 microg/ml for meropenem, and 16 and 256 microg/ml for piperacillin-tazobactam with and without clavulanate, respectively.

CONCLUSIONS

ESBL-producing organisms were more susceptible to meropenem than to ertapenem, although the MICs to ertapenem were well within clinically achievable levels. Piperacillin-tazobactam was ineffective in a large percentage of isolates. The presence of clavulanate resulted in a 5-fold decrease in the MIC of ertapenem and in a drastic reduction in the MIC of piperacillin-tazobactam. The decrease observed with ertapenem is unlikely to be of clinical significance. Thus, in our hospital, ertapenem could be a good meropenem-sparing agent for infections due to ESBL-producing organisms. Piperacillin-tazobactam appeared to be a poor choice, as our isolates produce ESBLs which are not successfully inhibited by tazobactam.

Tigecycline: a new glycylcycline antimicrobial

Tigecycline is a new glycyclcycline antimicrobial recently approved for use in the USA, Europe and elsewhere. While related to the tetracyclines, tigecycline overcomes many of the mechanisms responsible for resistance to this class. It demonstrates favourable in vitro potency against a variety of aerobic and anaerobic Gram-positive and Gram-negative pathogens, including those frequently demonstrating resistance to multiple classes of antimicrobials. This includes methicillin-resistant Staphylococcus aureus, penicillin-resistant S. pneumoniae, vancomycin-resistant enterococci, Acinetobacter baumannii, beta-lactamase producing strains of Haemophilis influenzae and Moraxella catarrhalis, and extended-spectrum beta-lactamase producing strains of Escherichia coli and Klebsiella pneumoniae. In contrast, minimum inhibitory concentrations for Pseudomonas and Proteus spp. are markedly elevated. Tigecycline is administered parenterally twice daily. Randomised, controlled trials have demonstrated that tigecycline is non-inferior to the comparators for the treatment of complicated skin and skin structure infections, as well as complicated intra-abdominal infections. The most frequent and problematic side effect associated with its administration to date has been nausea and/or vomiting.

[Extended-spectrum betalactamases producing Escherichia coli: a new health-care associated infection threat?]

OBJECTIVES

Study the health-care associated infection risk due to Extended-Spectrum Betalactamases Producing Escherichia coli (ESBL Esc) isolated from diagnostic samples.

METHODS

Descriptive, longitudinal and prospective study of 104 diagnostic isolates of ESBL Esc, one per patient, identified in Amiens university hospital between February 1999 and December 2005. Patients (sex, age, contamination risk factor, antecedent hospitalization) and microbiological data were progressively collected, entered into EPI INFO 6.04dFr software (ENSP, France) database, and compared using the chi-square test and Wilcoxon rank sum test, as appropriate. A p value of less than 0.05 was considered significant.

RESULTS

Diagnostic ESBL Esc isolates raised, per 1000 isolates of Esc, from 1.2 in 1999 to 6 in 2005. Global and acquired isolates number of ESBL Esc varied from 7 and 3 in 2002 to 25 and 19 in 2003 (P=0.22). ESBL Esc global and acquired incidence per 10(5) patient-days were, 0.8 and 0.6 in 1999 and 4.99 and 3.4 in 2005 (P<10(-6)), but rose from 0.6 acquired isolate in 2002 to 3.9 in 2003 (P=0.002). ESBL Esc, isolated from urines, stools, pulmonary, blood and surgical site samples of patients of>/=65 years aged (68.3%), were imipenem and latamoxef sensitive. Their acquisition risk factors found were hospitalization during the last 6 month period (40/104) and transfer from other institutions (20/104).

CONCLUSION

ESBL Esc isolates, among ESBL-producing Enterobacteriaceae, constitute an escalating health-care associated risk in our institution. The research at admission time of ESBL-producing Enterobacteriaceae, mainly in acute geriatric wards, strict isolation precaution and hand hygiene observance, rational antibiotic usage, are the key actions to control their cross transmission. Nonetheless, other studies are needed to determine whether we are in front of an ESBL Esc new clone emergence.

Phenotypic and genotypic detection of ESBL mediated cephalosporin resistance in Klebsiella pneumoniae: Emergence of high resistance against cefepime, the fourth generation cephalosporin

OBJECTIVES

Cephalosporins belonging to second and third generation are commonly used in India for the treatment of Klebsiella pneumoniae. Report on resistance among K. pneumoniae strains to second and third generation cephalosporins are on rise in this country, which has been attributed to emergence of strains expressing extended-spectrum beta-lactamases (ESBLs). The aim of this study was to evaluate the in vitro susceptibility of K. pneumoniae to broad-spectrum cephalosporins particularly to cefepime, a recently introduced fourth generation cephalosporin in relation to ESBL production.

METHODS

This study has been carried out in two phases among K. pneumoniae strains isolated between October 2001 and September 2002 (phase I, before marketing of cefepime in India) and between August 2003 and July 2004 (phase II, after marketing of cefepime in India). Minimum Inhibitory Concentration (MIC) was determined by a commercial strip containing gradient of antimicrobials (Strip E-test). Detection for ESBL production was carried out by DDST, E-test ESBL and PCR.

RESULTS

Antimicrobial resistance profile of K. pneumoniae strains to five cephalosporins as analyzed by WHONET 5 identified 15 different resistance profiles among the 108 phase I isolates, ranging from resistance to none (19.44%) to all the five cephalosporin (8.33%) and eight different resistance profiles among the 99 phase II isolates, ranging from resistance to none (9.1%) to all the five cephalosporins (36.4%). Among the 108 phase I isolates a total of 71 (65.72%) and out of 99 phase II isolates, a total of 87 (88.0%) could be identified as ESBL producers. Among the isolates, regardless of the phase of the isolation, those characterized by production of ESBL showed overall higher frequency of resistance to cephalosporins (range 19.7-85.9% and 51.7-100% in phase I and phase II, respectively) compared to those for ESBL non-producers (range 0-13.5% and 0-25% in phase I and phase II, respectively). Ten randomly selected isolates from the most common resistance phenotypes probably belonged to a single strain as evident by MIC patterns, genotypic characterization and resistance profile to non-cephalosporin group of antimicrobials thereby pointing out the possibility of an outbreak.

CONCLUSIONS

PCR may be regarded as a reliable method for detection of ESBL since in addition to the strains that could be identified as ESBL producers by DDST and E-test ESBL; PCR could demonstrate ESBL production among additional 32 strains (15 in phase I and 17 in phase II). Continued uses of cephalosporin group appear to be a potential risk factor for emergence of ESBL producing K. pneumoniae strains. In addition, as noted in the present study, the rise of resistance to cefepime that has been introduced recently in this country for therapeutic use could be of concern.

Clinical correlation of the CLSI susceptibility breakpoint for piperacillin- tazobactam against extended-spectrum-beta-lactamase-producing Escherichia coli and Klebsiella species

We assessed infections caused by extended-spectrum-beta-lactamase-producing Escherichia coli or Klebsiella spp. treated with piperacillin-tazobactam to determine if the susceptibility breakpoint predicts outcome. Treatment was successful in 10 of 11 nonurinary infections from susceptible strains and in 2 of 6 infections with MICs of >16/4 mug/ml. All six urinary infections responded to treatment regardless of susceptibility.

Bacterial resistance: a sensitive issue complexity of the challenge and containment strategy in Europe

The development of antimicrobial agents has been a key achievement of modern medicine. However, their overuse has led to an increasing incidence of infections due to antibiotic-resistant microorganisms. Quantitative figures on the current economic and health impact of antimicrobial resistance are scant, but it is clearly a growing challenge that requires timely action. That action should be at the educational, ethical, economic and political level. An important first step would be to increase public awareness and willingness to take the necessary measures to curb resistance. Hence, studies are needed that would provide solid, quantitative data on the societal impact of antibiotic resistance. This review discusses the complexity of resistance, identifies its main drivers and proposes measures to contain it on a European scale.

Mechanisms of antimicrobial resistance in bacteria

The treatment of bacterial infections is increasingly complicated by the ability of bacteria to develop resistance to antimicrobial agents. Antimicrobial agents are often categorized according to their principal mechanism of action. Mechanisms include interference with cell wall synthesis (eg, beta-lactams and glycopeptide agents), inhibition of protein synthesis (macrolides and tetracyclines), interference with nucleic acid synthesis (fluoroquinolones and rifampin), inhibition of a metabolic pathway (trimethoprim-sulfamethoxazole), and disruption of bacterial membrane structure (polymyxins and daptomycin). Bacteria may be intrinsically resistant to > or =1 class of antimicrobial agents, or may acquire resistance by de novo mutation or via the acquisition of resistance genes from other organisms. Acquired resistance genes may enable a bacterium to produce enzymes that destroy the antibacterial drug, to express efflux systems that prevent the drug from reaching its intracellular target, to modify the drug's target site, or to produce an alternative metabolic pathway that bypasses the action of the drug. Acquisition of new genetic material by antimicrobial-susceptible bacteria from resistant strains of bacteria may occur through conjugation, transformation, or transduction, with transposons often facilitating the incorporation of the multiple resistance genes into the host's genome or plasmids. Use of antibacterial agents creates selective pressure for the emergence of resistant strains. Herein 3 case histories-one involving Escherichia coli resistance to third-generation cephalosporins, another focusing on the emergence of vancomycin-resistant Staphylococcus aureus, and a third detailing multidrug resistance in Pseudomonas aeruginosa-are reviewed to illustrate the varied ways in which resistant bacteria develop.

Resistance in gram-negative bacteria: enterobacteriaceae

The emergence and spread of resistance in Enterobacteriaceae are complicating the treatment of serious nosocomial infections and threatening to create species resistant to all currently available agents. Approximately 20% of Klebsiella pneumoniae infections and 31% of Enterobacter spp infections in intensive care units in the United States now involve strains not susceptible to third-generation cephalosporins. Such resistance in K pneumoniae to third-generation cephalosporins is typically caused by the acquisition of plasmids containing genes that encode for extended-spectrum beta-lactamases (ESBLs), and these plasmids often carry other resistance genes as well. ESBL-producing K pneumoniae and Escherichia coli are now relatively common in healthcare settings and often exhibit multidrug resistance. ESBL-producing Enterobacteriaceae have now emerged in the community as well. Salmonella and other Enterobacteriaceae that cause gastroenteritis may also be ESBL producers, which is of relevance when children require treatment for invasive infections. Resistance of Enterobacter spp to third-generation cephalosporins is most typically caused by overproduction of AmpC beta-lactamases, and treatment with third-generation cephalosporins may select for AmpC-overproducing mutants. Some Enterobacter cloacae strains are now ESBL and AmpC producers, conferring resistance to both third- and fourth-generation cephalosporins. Quinolone resistance in Enterobacteriaceae is usually the result of chromosomal mutations leading to alterations in target enzymes or drug accumulation. More recently, however, plasmid-mediated quinolone resistance has been reported in K pneumoniae and E coli, associated with acquisition of the qnr gene. The vast majority of Enterobacteriaceae, including ESBL producers, remain susceptible to carbapenems, and these agents are considered preferred empiric therapy for serious Enterobacteriaceae infections. Carbapenem resistance, although rare, appears to be increasing. Particularly troublesome is the emergence of KPC-type carbapenemases in New York City. Better antibiotic stewardship and infection control are needed to prevent further spread of ESBLs and other forms of resistance in Enterobacteriaceae throughout the world.

Resistance in gram-negative bacteria: Enterobacteriaceae

The emergence and spread of resistance in Enterobacteriaceae are complicating the treatment of serious nosocomial infections and threatening to create species resistant to all currently available agents. Approximately 20% of Klebsiella pneumoniae infections and 31% of Enterobacter spp infections in intensive care units in the United States now involve strains not susceptible to third-generation cephalosporins. Such resistance in K pneumoniae to third-generation cephalosporins is typically caused by the acquisition of plasmids containing genes that encode for extended-spectrum beta-lactamases (ESBLs), and these plasmids often carry other resistance genes as well. ESBL-producing K pneumoniae and Escherichia coli are now relatively common in healthcare settings and often exhibit multidrug resistance. ESBL-producing Enterobacteriaceae have now emerged in the community as well. Salmonella and other Enterobacteriaceae that cause gastroenteritis may also be ESBL producers, which is of relevance when children require treatment for invasive infections. Resistance of Enterobacter spp to third-generation cephalosporins is most typically caused by overproduction of AmpC beta-lactamases, and treatment with third-generation cephalosporins may select for AmpC-overproducing mutants. Some Enterobacter cloacae strains are now ESBL and AmpC producers, conferring resistance to both third- and fourth-generation cephalosporins. Quinolone resistance in Enterobacteriaceae is usually the result of chromosomal mutations leading to alterations in target enzymes or drug accumulation. More recently, however, plasmid-mediated quinolone resistance has been reported in K pneumoniae and E coli, associated with acquisition of the qnr gene. The vast majority of Enterobacteriaceae, including ESBL producers, remain susceptible to carbapenems, and these agents are considered preferred empiric therapy for serious Enterobacteriaceae infections. Carbapenem resistance, although rare, appears to be increasing. Particularly troublesome is the emergence of KPC-type carbapenemases in New York City. Better antibiotic stewardship and infection control are needed to prevent further spread of ESBLs and other forms of resistance in Enterobacteriaceae throughout the world.

Mechanisms of antimicrobial resistance in bacteria

The treatment of bacterial infections is increasingly complicated by the ability of bacteria to develop resistance to antimicrobial agents. Antimicrobial agents are often categorized according to their principal mechanism of action. Mechanisms include interference with cell wall synthesis (e.g., beta-lactams and glycopeptide agents), inhibition of protein synthesis (macrolides and tetracyclines), interference with nucleic acid synthesis (fluoroquinolones and rifampin), inhibition of a metabolic pathway (trimethoprim-sulfamethoxazole), and disruption of bacterial membrane structure (polymyxins and daptomycin). Bacteria may be intrinsically resistant to > or =1 class of antimicrobial agents, or may acquire resistance by de novo mutation or via the acquisition of resistance genes from other organisms. Acquired resistance genes may enable a bacterium to produce enzymes that destroy the antibacterial drug, to express efflux systems that prevent the drug from reaching its intracellular target, to modify the drug's target site, or to produce an alternative metabolic pathway that bypasses the action of the drug. Acquisition of new genetic material by antimicrobial-susceptible bacteria from resistant strains of bacteria may occur through conjugation, transformation, or transduction, with transposons often facilitating the incorporation of the multiple resistance genes into the host's genome or plasmids. Use of antibacterial agents creates selective pressure for the emergence of resistant strains. Herein 3 case histories-one involving Escherichia coli resistance to third-generation cephalosporins, another focusing on the emergence of vancomycin-resistant Staphylococcus aureus, and a third detailing multidrug resistance in Pseudomonas aeruginosa--are reviewed to illustrate the varied ways in which resistant bacteria develop.

Estudo etiológico da diarréia em crianças hospitalizadas no Instituto Materno Infantil Prof. Fernando Figueira, IMIP, em Recife, Pernambuco

OBJETIVOS: identificar enteropatógenos nas fezes de crianças hospitalizadas com diarréia. MÉTODOS: estudo de série de casos, com a participação de 36 crianças entre zero a 60 meses, com diarréia, hospitalizadas no Instituto Materno Infantil Prof. Fernando Figueira, IMIP, no período entre janeiro e maio de 2005. Foram coletadas as variáveis sócio-demográficas, características das mães e do episódio diarréico. A pesquisa etiologica utilizou coprocultura e testes sorológicos. RESULTADOS: a maioria das crianças (80,5%) tinha menos de 12 meses. As famílias tinham precárias condições socioeconômicas e 83,4% tinha renda per capita inferior a meio salário mínimo/mês. Quanto aos microorganismos recuperados nas culturas de fezes, a E. coli enteropatogênica clássica (EPEC) apareceu em 8,4% dos casos, não havendo crescimento de Salmonella sp. ou Shiguella sp. e a Klebsiella sp. ESBL + foi isolada em 33,3% dos pacientes. As Klebsiellas apresentaram um alto perfil de resistência no antibiograma, compatível com as cepas hospitalares catalogadas na instituição. CONCLUSÕES: o estudo apresentou uma baixa taxa de recuperação de bactérias enteropatogênicas mas revelou uma prevalência de Klebsiella multirresistente, o que tem importantes implicações no risco de infecção hospitalar e persistência do episódio diarréico.

Resistance to antibiotics: are we in the post-antibiotic era?

Serious infections caused by bacteria that have become resistant to commonly used antibiotics have become a major global healthcare problem in the 21st century. They not only are more severe and require longer and more complex treatments, but they are also significantly more expensive to diagnose and to treat. Antibiotic resistance, initially a problem of the hospital setting associated with an increased number of hospital-acquired infections usually in critically ill and immunosuppressed patients, has now extended into the community causing severe infections difficult to diagnose and treat. The molecular mechanisms by which bacteria have become resistant to antibiotics are diverse and complex. Bacteria have developed resistance to all different classes of antibiotics discovered to date. The most frequent type of resistance is acquired and transmitted horizontally via the conjugation of a plasmid. In recent times new mechanisms of resistance have resulted in the simultaneous development of resistance to several antibiotic classes creating very dangerous multidrug-resistant (MDR) bacterial strains, some also known as "superbugs". The indiscriminate and inappropriate use of antibiotics in outpatient clinics, hospitalized patients and in the food industry is the single largest factor leading to antibiotic resistance. In recent years, the number of new antibiotics licensed for human use in different parts of the world has been lower than in the recent past. In addition, there has been less innovation in the field of antimicrobial discovery research and development. The pharmaceutical industry, large academic institutions or the government are not investing the necessary resources to produce the next generation of newer safe and effective antimicrobial drugs. In many cases, large pharmaceutical companies have terminated their anti-infective research programs altogether due to economic reasons. The potential negative consequences of all these events are relevant because they put society at risk for the spread of potentially serious MDR bacterial infections.

Kinetic properties of four plasmid-mediated AmpC beta-lactamases

The heterologous production in Escherichia coli, the purification, and the kinetic characterization of four plasmid-encoded class C beta-lactamases (ACT-1, MIR-1, CMY-2, and CMY-1) were performed. Except for their instability, these enzymes are very similar to the known chromosomally encoded AmpC beta-lactamases. Their kinetic parameters did not show major differences from those obtained for the corresponding chromosomal enzymes. However, the K(m) values of CMY-2 for cefuroxime, cefotaxime, and oxacillin were significantly decreased compared to those of the chromosomal AmpC enzymes. Finally, the susceptibility patterns of different E. coli hosts producing a plasmid- or a chromosome-encoded class C enzyme toward beta-lactam antibiotics are mainly due to the overproduction of the beta-lactamase in the periplasmic space of the bacteria rather than to a specific catalytic profile of the plasmid-encoded beta-lactamases.

Infectious Complications of Cancer Therapy

Advances in the management of cancer, particularly the development of new chemotherapeutic agents, have greatly improved the survival and outcome of patients with hematologic malignancies and solid tumors; overall 5-year survival rates in cancer patients have improved from 39% in the 1960s to 60% in the 1990s.1 However, infection, caused by both the underlying malignancy and cancer chemotherapy, particularly myelosuppressive chemotherapy, remains a persistent challenge.

Antimicrobial resistance of Escherichia coli and therapeutic implications

Widespread antibiotic resistance has been recognized in Escherichia coli isolates from human, animal and environmental sources. Although prevalence rates for resistant E. coli strains are significantly distinct for various populations and environments, the impact of resistance to antimicrobial drugs is ubiquitous. This article provides information about the epidemiology, mechanisms and molecular principles of resistance, shows consequences for the antiinfective treatment of selected infections and describes measures to control the spread of antibiotic-resistant E. coli.

Proteus mirabilis bloodstream infections: risk factors and treatment outcome related to the expression of extended-spectrum beta-lactamases

Bloodstream infection (BSI) due to Proteus mirabilis strains is a relatively uncommon clinical entity, and its significance has received little attention. This study was initiated to evaluate risk factors and treatment outcome of BSI episodes due to P. mirabilis producing extended-spectrum beta-lactamases (ESBLs). Twenty-five BSI episodes caused by P. mirabilis occurred at our hospital (Ospedale di Circolo e Fondazione Macchi, Varese, Italy) over a 7.5-year period. Phenotypic and molecular methods were used to assess ESBL production. Clinical records of BSI patients were examined retrospectively. Demographic data, underlying diseases (according to McCabe and Jackson classification and Charlson weighted index), risk factors, and treatment outcome were investigated by comparing cases due to ESBL-positive strains to cases due to ESBL-negative strains. Eleven isolates were found to express ESBLs (TEM-52 or TEM-92). The remaining 14 isolates were ESBL negative and were uniformly susceptible to extended-spectrum cephalosporins and monobactams. Comparison of the two groups showed that previous hospitalization in a nursing home (P = 0.04) and use of bladder catheter (P = 0.01) were significant risk factors for infections due to ESBL-positive strains. In addition, cases due to ESBL-positive strains showed a significantly higher mortality attributable to BSI (P = 0.04). BSI cases due to ESBL-negative isolates uniformly responded to therapy, whereas 5/11 cases due to ESBL-positive isolates failed to respond (P < 0.01). Use of carbapenems was associated with complete response independently of ESBL production. Therapeutic failure and mortality may occur in BSI episodes caused by ESBL-positive P. mirabilis isolates. Thus, recognition of ESBL-positive strains appears to be critical for the clinical management of patients with systemic P. mirabilis infections.

Presence of multidrug-resistant enteric bacteria in dairy farm topsoil

In addition to human and veterinary medicine, antibiotics are extensively used in agricultural settings, such as for treatment of infections, growth enhancement, and prophylaxis in food animals, leading to selection of drug and multidrug-resistant bacteria. To help circumvent the problem of bacterial antibiotic resistance, it is first necessary to understand the scope of the problem. However, it is not fully understood how widespread antibiotic-resistant bacteria are in agricultural settings. The lack of such surveillance data is especially evident in dairy farm environments, such as soil. It is also unknown to what extent various physiological modulators, such as salicylate, a component of aspirin and known model modulator of multiple antibiotic resistance (mar) genes, influence bacterial multi-drug resistance. We isolated and identified enteric soil bacteria from local dairy farms within Roosevelt County, NM, determined the resistance profiles to antibiotics associated with mar, such as chloramphenicol, nalidixic acid, penicillin G, and tetracycline. We then purified and characterized plasmid DNA and detected mar phenotypic activity. The minimal inhibitory concentrations (MIC) of antibiotics for the isolates ranged from 6 to >50 microg/mL for chloramphenicol, 2 to 8 microg/mL for nalidixic acid, 25 to >300 microg/mL for penicillin G, and 1 to >80 microg/mL for tetracycline. On the other hand, many of the isolates had significantly enhanced MIC for the same antibiotics in the presence of 5 mM salicylate. Plasmid DNA extracted from 12 randomly chosen isolates ranged in size from 6 to 12.5 kb and, in several cases, conferred resistance to chloramphenicol and penicillin G. It is concluded that enteric bacteria from dairy farm topsoil are multidrug resistant and harbor antibiotic-resistance plasmids. A role for dairy topsoil in zoonoses is suggested, implicating this environment as a reservoir for development of bacterial resistance against clinically relevant antibiotics.

In vitro activity of tigecycline against 6792 Gram-negative and Gram-positive clinical isolates from the global Tigecycline Evaluation and Surveillance Trial (TEST Program, 2004)

Tigecycline, a new glycylcycline antibiotic, has shown promising in vitro activity against many common pathogens, including multidrug-resistant strains. To determine the activity of tigecycline against a broad range of pathogens from diverse populations and geographic areas, the Tigecycline Evaluation and Surveillance Trial (TEST Program) commenced in 2003. This study evaluated the activity of tigecycline and commonly used antimicrobials against 6792 clinical isolates from 40 study centers in 11 countries. Tigecycline was the most active agent tested against Gram-positive facultative species including multidrug-resistant strains. MIC90 results (microg/mL) for tigecycline against Enterococcus faecalis, Enterococcus faecium, Staphylococcus aureus, Streptococcus agalactiae, and Streptococcus pneumoniae were 0.12, 0.12, 0.25, and 0.25 microg/mL, respectively. Tigecycline was active against Enterobacteriaceae with an MIC90 of 1 microg/mL. Haemophilus influenzae was very susceptible to tigecycline with an MIC90 of only 0.25 microg/mL. Pseudomonas aeruginosa was the least susceptible organism tested against tigecycline. Tigecycline appears to be a promising new glycylcycline agent for the treatment of many types of pathogens with varying resistance phenotypes.

Risk factors associated with extended-spectrum β-lactamase-producing organisms at a tertiary care hospital

BACKGROUND

In 1995, beta-lactam inhibitor combinations replaced third-generation cephalosporins as empirical therapy in an effort to manage extended-spectrum beta-lactamase (ESBL) resistance. This study investigated the relationship between antibiotic usage and ESBL organisms from 1994 through 2002 using epidemiological and molecular analysis.

METHODS

A case-control study of 119 patients with ESBL organisms and 132 patients with non-ESBL organisms was conducted. Demographics, co-morbidities, device utilization and antibiotic use were analysed for all patients and infected patients only (cases = 75, controls = 83). Both exposure and degree of exposure (in grams) to antibiotics were included. A dot blot hybridization technique was used to identify genes in plasmid extracts from the ESBL organisms.

RESULTS

Ventilator days OR 1.1 (1.06, 1.15) P < 0.001, adult respiratory distress syndrome (ARDS) OR 3.1 (1.0, 9.7) P = 0.05, prior aminoglycoside use OR 2.7 (1.2, 6.1) P = 0.02, prior third-generation cephalosporin use OR 7.2 (2.6, 20) P < 0.001, and prior trimethoprim/sulfamethoxazole use OR 8.8 (3.1, 26) P < 0.001 were significantly associated with ESBL organisms by multivariate analysis. All models were concordant with a significant association of ventilator days, third-generation cephalosporins and trimethoprim/sulfamethoxazole with ESBL organisms. beta-Lactamase inhibitor combinations were not associated with ESBL organisms. Hybridization of plasmid extracts demonstrated that 95% of the ESBL organisms carried intI1, a mobile DNA element with a sulphonamide-resistance (R) gene and a frequent carrier of other R factors. Genes for specific types of trimethoprim-R and aminoglycoside-R were present in 26% and 40% of the extracts, respectively.

CONCLUSIONS

These data indicate that, besides patient risk factors and third-generation cephalosporins, other antibiotics may provide selective pressures in maintaining ESBL organisms due to multiple resistance genes on plasmids. beta-Lactamase inhibitor combinations appear to be an acceptable substitute to third-generation cephalosporins in strategies to control ESBL organisms.

Expanded-spectrum beta-lactamase producing Klebsiella pneumoniae-related peritonitis in a patient on peritoneal dialysis

While hospitalized for pneumonia with ventilator-dependent respiratory failure, a 45-year-old man on continuous ambulatory peritoneal dialysis (CAPD) had nosocomial peritonitis secondary to infection by expanded spectrum beta-lactamase producing Klebsiella pneumoniae (ESBL-Kp). He was treated successfully with a 3-week course of intraperitoneal (IP) flomoxef therapy without subsequent relapse, loss of peritoneal catheter, ultrafiltration failure, or dialysis inadequacy. The International Consensus Panel recommends IP ceftazidime as the treatment of choice for CAPD patients suffering Klebsiella species-related peritonitis. However, the most appropriate form of IP antibiotic therapy and the outcomes for expanded-spectrum beta-lactamase (ESBL)-producing bacteria-related peritonitis for CAPD patients have not been established yet. Further, the ability to correctly report minimal inhibitory concentrations (MICs) of ceftazidime for ESBL bacteria in the resistant range varies between laboratories, making the diagnosis of ESBL-Kp-related CAPD peritonitis more complex and difficult. Thus, it appears reasonable to suggest that its incidence is probably underestimated and its significance ignored. The authors suggest that a 3-week IP treatment with flomoxef, a synthesized oxacephem, with loading and maintenance doses of 250 and 125 mg/L, respectively, is effective and safe for ESBL-Kp-related peritonitis in these patients. ESBL producing bacterial infection should be considered as a possible cause of overt CAPD-related peritonitis. Early detection of ESBLB pathogens and institution of effective antibiotic treatment may improve the prognosis.

Update on Resistance among Nosocomial Gram-Negative Pathogens to Extended-Spectrum Cephalosporins and Fluoroquinolones: Results of the Antimicrobial Resistance Management (ARM) Program

Objective

To evaluate trends in antibiotic resistance among Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Pseudomonas aeruginosa isolates submitted to the Antimicrobial Resistance Management (ARM) program between 1990 and 2002.

Design

The ongoing Antimicrobial Resistance Management (ARM) program is a queriable Web-based surveillance system that tracks resistance patterns among U.S. inpatient and outpatient isolates. This report represents data from 285 institutions and over 17 million isolates. Using a Web-based analysis tool, antibiogram and sensitivity reports of E. coli, K. pneumoniae, P. mirabilis, and P. aeruginosa isolates were reviewed for resistance to extended-spectrum cephalosporins and fluoroquinolones.

Setting

285 teaching and non-teaching U.S Hospitals nationwide.

Results

For E. coli, resistance was 3.2% to ciprofloxacin (n = 444,947), 5.4% to levofloxacin (n = 201,532), and 0.8% to cefotaxime (n = 107,394), ceftriaxone (n = 464,931), and cefepime (n = 81,980), respectively. K. pneumoniae isolate resistance was 4.6% to ciprofloxacin (n = 144,698), 4.5% to levofloxacin (n = 57,462), 1.9% to cefotaxime (n = 33,189), 2.0% to ceftriaxone (n = 145,328) and 1.9% to cefepime (n = 25,503). For P. mirabilis, resistance was 12.5% to ciprofloxacin (n = 83,186), 12.2% to levofloxacin (n = 35,277), 1.0% to cefotaxime (n = 18,802), 0.7% to ceftriaxone (83,652), and 2.3% to cefepime (n = 13,968). P. aeruginosa resistance was also higher for fluoroquinolones (only 65.2% of isolates were susceptible to ciprofloxacin) compared to extended-spectrum cephalosporins, with ceftazidime exhibiting the greatest antipseudomonal activity. Clinically significant regional variations in the activity of fluoroquinolones and cephalosporins were apparent.

Conclusion

Resistance to the fluoroquinolones is increasing dramatically, whereas the third generation cephalosporins remain inherently more active. P. aeruginosa exhibits the most formidable resistance pattern with neither the antipseudomonal cephalosporins nor fluoroquinolones representing acceptable monotherapy options. Given the association between fluoroquinolone resistance and extended-spectrum β-lactamase production, continued surveillance is vital to preserve the activity of existing therapies.

First-generation fluoroquinolone use and subsequent emergence of multiple drug-resistant bacteria in the intensive care unit

OBJECTIVE

The objective of this study was to determine the relationship between fluoroquinolone (FQ) use and subsequent emergence of multiple drug-resistant bacteria (MRB) in the intensive care unit (ICU).

DESIGN

The authors conducted a prospective observational cohort study and a case control study.

SETTING

The study was conducted in a 30-bed ICU.

METHODS

All immunocompetent patients hospitalized for >48 hrs who did not receive antibiotics before ICU admission were eligible during a 15-month period. Routine MRB screening was performed at ICU admission and weekly thereafter. This screening included tracheal aspirate and nasal, anal, and axilla swabs. Univariate and multivariate analyses were used to determine risk factors for MRB emergence in the ICU. In addition, a case control study was performed to determine whether FQ use is associated with subsequent emergence of MRB.

RESULTS

Two hundred thirty-nine patients were included; 108 ICU-acquired MRB were isolated in 77 patients. FQ use and longer duration of antibiotic treatment were identified as independent risk factors for MRB occurrence (odds ratio [95% confidence interval [CI] = 3.3 [1.7-6.5], 1.1 [1.0-1.2]; p < .001; respectively). One hundred thirty-five (56%) patients received FQ; matching was successful for 72 (53%) of them. Number of MRB (40 vs. 15 per 1,000 ICU days; p = .019) and percentage of patients with MRB (40% vs. 22%; OR [95% CI] = 1.5 [1.0-2.4]; p = .028) were significantly higher in cases than in controls. Although methicillin-resistant Staphylococcus aureus (26% vs. 12%; OR [95% CI] = 1.6 [.6-2.9]; p = .028) and extending-spectrum beta-lactamase-producing Gram-negative bacilli (11% vs. 1%; OR [95% CI] = 4.7 [0.7-30.2]; p = .017) rates were higher in cases than in controls, ceftazidime or imipenem-resistant Pseudomonas aeruginosa (15% vs. 8%), Acinetobacter baumannii (1% vs. 5%), and Stenotrophomonas maltophilia (2% vs. 1%) rates were similar (p > .05) in case and control patients.

CONCLUSION

FQ use and longer duration of antibiotic treatment are independently associated with MRB emergence. Reducing antimicrobial treatment duration and restricting FQ use could be suggested to control MRB spread in the ICU.