Outbreak of ceftazidime resistance due to a novel extended-spectrum beta-lactamase in isolates from cancer patients

The role of tazobactam-based combinations for the management of infections due to extended-spectrum β-lactamase-producing Enterobacterales: Insights from the Society of Infectious Diseases Pharmacists

Extended-spectrum β-lactamase (ESBL)-producing Enterobacterales are a global threat to public health due to their antimicrobial resistance profile and, consequently, their limited available treatment options. Tazobactam is a sulfone β-lactamase inhibitor with in vitro inhibitory activity against common ESBLs in Enterobacterales, including CTX-M. However, the role of tazobactam-based combinations in treating infections caused by ESBL-producing Enterobacterales remains unclear. In the United States, two tazobactam-based combinations are available, piperacillin-tazobactam and ceftolozane-tazobactam. We evaluated and compared the roles of tazobactam-based combinations against ESBL-producing organisms with emphasis on pharmacokinetic/pharmacodynamic exposures in relation to MIC distributions and established breakpoints, clinical outcomes data specific to infection site, and considerations for downstream effects with these agents regarding antimicrobial resistance development. While limited data with ceftolozane-tazobactam are encouraging for its potential role in infections due to ESBL-producing Enterobacterales, further evidence is needed to determine its place in therapy. Conversely, currently available microbiologic, pharmacokinetic, pharmacodynamic, and clinical data do not suggest a role for piperacillin-tazobactam, and we caution clinicians against its usage for these infections.

Anticancer and antibacterial effects of a clove bud essential oil-based nanoscale emulsion system

BACKGROUND AND PURPOSE

The essential oil derived from clove buds (Syzygium aromaticum) has been used as a chemopreventive agent in Ayurvedic medicine. The antiviral, antibacterial, and anticancer properties of its chemo-skeleton have motivated this study to explore its efficacy in pharmaceutics.

METHODS

Nanoscale-based emulsions were prepared by employing a spontaneous emulsification technique through self-assembly using varying concentrations of Tween 20 and Tween 80 surfactants. Their physicochemical properties and stability were studied in order to choose an optimum formulation which was clear and stable. The cytotoxicity of the stable oil-based emulsion system was evaluated using MTT assay, colony formation assay, and Annexin V-FITC assay against the thyroid cancer cell line (HTh-7).

RESULTS

All three methods verified apoptosis and reduction in cancer cell proliferation, making the formulation a promising candidate as an alternative cancer drug. The oil-based emulsion system was also tested for its antibacterial properties against Staphylococcus aureus. Membrane permeability studies proved its efficacy to permeate through cell membrane, thereby increasing the leakage of cytoplasmic contents.

CONCLUSION

Many current treatments for cancers are aggressive yet ineffective. This study positions the clove bud-based nanoscale emulsion as a suitable candidate for further in vivo studies and trials as a cancer drug.

Antiproliferative, neurotoxic, genotoxic and mutagenic effects of toxic cyanobacterial extracts

Cyanobacteria are the rich resource of various secondary metabolites including toxins with broad pharmaceutical significance. The aim of this work was to evaluate the antiproliferative, neurotoxic, genotoxic and mutagenic effects of cyanobacterial extracts containing Microcystin-LR (MCLR) in vitro. ELISA analysis results showed that MCLR contents of five cyanobacterial extracts were 2.07 ng/mL, 1.43 ng/mL, 1.41 ng/mL, 1.27 ng/mL, and 1.12 ng/mL for Leptolyngbya sp. SB1, Phormidium sp. SB4, Oscillatoria earlei SB5, Phormidium sp. SB2, Uncultured cyanobacterium, respectively. Phormidium sp. SB4 and Phormidium sp. SB2 extracts had the lowest neurotoxicity (86% and 79% cell viability, respectively) and Oscillatoria earlei SB5 extracts had the highest neurotoxicity (47% cell viability) on PC12 cell at 1000 µg/ml extract concentration. Leptolyngbya sp. SB1 and Phormidium sp. SB2 showed the highest antiproliferative effect (92% and 77% cell death) on HT29 cell. On the other hand, all concentrations of five toxic cyanobacterial extracts induced DNA damage between 3.0% and 1.3% of tail intensity and did not cause any direct mutagenic effect at the 1000 µg/plate cyanobacterial extracts. These results suggest that cyanobacteria-derived MCLR is a promising candidate for development of effective agents against colon cancer.

PK/PD Target Attainment With Ceftolozane/Tazobactam Using Monte Carlo Simulation in Patients With Various Degrees of Renal Function, Including Augmented Renal Clearance and End-Stage Renal Disease

Introduction

Ceftolozane/tazobactam is an antibacterial agent with potent in vitro activity against Gram-negative pathogens, including many extended-spectrum β-lactamase-producing Enterobacteriaceae and drug-resistant Pseudomonas aeruginosa. Because ceftolozane/tazobactam is primarily excreted renally, appropriate dose adjustments are needed for patients with renal impairment. Monte Carlo simulations were used to determine the probability of pharmacokinetic/pharmacodynamic target attainment for patients with varying degrees of renal function, including augmented renal clearance (ARC) and end-stage renal disease (ESRD) with hemodialysis.

Methods

Monte Carlo simulations were conducted for 1000 patients with ARC and normal renal function, mild renal impairment, moderate renal impairment, or severe renal impairment, and for 5000 patients with ESRD. Simulated dosing regimens were based on approved doses for each renal function category. Attainment targets for ceftolozane were 24.8% (bacteriostasis), 32.2% (1-log kill; bactericidal), and 40% (2-log kill) fT > minimum inhibitory concentration (MIC). The target for tazobactam was to achieve a 20% fT > minimum effective concentration (MEC) at an MEC of 1 mg/L, which was derived from a neutropenic mouse thigh infection model and was confirmed by efficacy data from clinical studies for complicated intraabdominal infections and complicated urinary tract infections.

Results

In patients with ARC or normal renal function, ≥91% achieved bactericidal activity (32.2% fT > MIC) up to an MIC of 4 mg/L with a 1000-mg ceftolozane dose. In patients with renal impairment (mild, moderate, severe, ESRD), ≥93% achieved bactericidal activity up to an MIC of 8 mg/L. In patients of all renal function categories, the approved dosing regimens of tazobactam achieved ≥91% target attainment against a target of 20% fT > MEC.

Conclusions

At the approved dosing regimens for ceftolozane/tazobactam, ≥91% of patients in all renal function categories, including ARC (up to 200 mL/min) and ESRD, reached target attainment for bactericidal activity at MICs that correspond to susceptibility breakpoints for Enterobacteriaceae and P. aeruginosa.

Urinary tract infection in infants caused by extended-spectrum beta-lactamase-producing Escherichia coli: comparison between urban and rural hospitals

BACKGROUND

Community-acquired urinary tract infection (UTI) caused by extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli is an emerging problem. Compared with urban infants, rural infants may encounter different distributions of community-acquired resistant strains and various barriers to efficient management.

METHODS

A retrospective survey and comparison was conducted for infants with UTI caused by ESBL-producing E. coli admitted to an urban hospital (n = 111) and a rural hospital (n = 48) in southern Taiwan from 2009 to 2012.

RESULTS

Compared with 2009 and 2010, the total number of cases at both hospitals significantly increased in 2011 and 2012 (p < 0.001). Compared with the rural patients, the urban patients were significantly younger, and they had fewer days of fever before and after admission, fewer presentations of poor activity and poor appetite, and a lower serum creatinine level. Most of the patients had no prior history of illness, and we could not identify any significant different risk factors for acquiring ESBL-producing E. coli, such as past antimicrobial use, hospitalization, UTI, and underlying renal diseases, between the urban and rural populations.

CONCLUSIONS

The increase in community-acquired UTI in infants caused by ESBL-producing E. coli was similar between the urban and rural populations. Our preliminary data suggest that the rural-urban disparities were probably related to easy access to health care by the urban population. ESBL complicates disease management, and the increase in the prevalence of ESBL producers is a major health concern and requires further healthy carrier and environmental surveillance.

Emergence of extended spectrum-β-lactamase-producing Escherichia coli O25b-ST131: a major community-acquired uropathogen in infants

BACKGROUND

Escherichia coli sero-group O25b-sequence type 131 (O25b-ST131), a multidrug-resistant clonal group, is a significant pathogen in adults and children. This study investigated the genotyping and role of extended spectrum β-lactamase (ESBL)-producing E. coli O25b-ST131 and non-O25b-ST131 in urinary tract infections in infants.

METHODS

Clinical and laboratory data from 111 infants less than 1 year of age, who were hospitalized for urinary tract infections caused by ESBL-producing E. coli between 2009 and 2012 were collected. Polymerase chain reactions and multi-locus sequence typing were used to identify E. coli O25-ST131 clones. The gene blaCTX-M groups 1, 2 and 9, a specific polymerase chain reaction of CTX-M 14 and 15, were also determined in ESBL-producing E. coli isolates.

RESULTS

O25b-ST131 accounted for 65% of the 111 isolates, although 92 isolates belonged to the blaCTX-M group 9, of which most were CTX-M-14. Those with O25b-ST131 clones had similar risk factors, clinical features and outcomes as those with non-O25b-ST131. The E. coli O25b-ST131 isolates were more resistant to ciprofloxacin and gentamicin, but more susceptible to cefoxitin, minocycline and trimethoprim/sulfamethoxazole than the non-O25b-ST131 isolates. Most of the infants (78%) were previously healthy with no apparent risk factors.

CONCLUSIONS

E. coli O25b-ST131 is a major community-acquired uropathogen in the infant population. Regardless of O25b-ST131 or non-O25b-ST131 clones, CTX-M-14 accounts for majority of the ESBL genotype. The O25b-ST131 clone is not associated with more severe clinical disease, but it may make the diagnosis and selection of antimicrobials for treatment more challenging.

In vitro activity of ceftolozane-tazobactam as determined by broth dilution and agar diffusion assays against recent U.S. Escherichia coli isolates from 2010 to 2011 carrying CTX-M-type extended-spectrum β-lactamases

Ceftolozane MIC(50)/MIC(90)s were 4/8 μg/ml when tested against 26 CTX-M-14-type-producing isolates and 64/>64 μg/ml against 219 CTX-M-15-type-producing isolates. The addition of 4 μg/ml tazobactam lowered the ceftolozane MIC50/MIC9(0)s to ≤ 0.25/0.5 μg/ml by broth microdilution and Etest. The zone diameters for the ceftolozane-tazobactam disks were 23 to 29 mm for 92.2% of the isolates.

Essential oils and their constituents as anticancer agents: a mechanistic view

Exploring natural plant products as an option to find new chemical entities as anticancer agents is one of the fastest growing areas of research. Recently, in the last decade, essential oils (EOs) have been under study for their use in cancer therapy and the present review is an attempt to collect and document the available studies indicating EOs and their constituents as anticancer agents. This review enlists nearly 130 studies of EOs from various plant species and their constituents that have been studied so far for their anticancer potential and these studies have been classified as in vitro and in vivo studies for EOs and their constituents. This review also highlights in-depth various mechanisms of action of different EOs and their constituents reported in the treatment strategies for different types of cancer. The current review indicates that EOs and their constituents act by multiple pathways and mechanisms involving apoptosis, cell cycle arrest, antimetastatic and antiangiogenic, increased levels of reactive oxygen and nitrogen species (ROS/RNS), DNA repair modulation, and others to demonstrate their antiproliferative activity in the cancer cell. The effect of EOs and their constituents on tumour suppressor proteins (p53 and Akt), transcription factors (NF- κB and AP-1), MAPK-pathway, and detoxification enzymes like SOD, catalase, glutathione peroxidase, and glutathione reductase has also been discussed.

Prevalence of extended spectrum beta lactamase producing Escherichia coli and Klebsiella pneumoniae urinary isolates in a tertiary care hospital in Kathmandu, Nepal

BACKGROUND

Escherichia coli and Klebsiella pneumoniae are the major bacterial pathogens being isolated and reported from mid stream urine (MSU) specimens, globally. These uropathogens are mostly implicated as the major extended spectrum beta-lactamase (ESBL) producers, severely limiting the therapeutic management in cases of urinary tract infections. Limited studies had been reported from Nepal investigating the ESBL producers among uropathogens. This study was designed to assess the prevalence of ESBL producing E.coli and K. pneumoniae in urinary isolates at a centrally located major tertiary care hospital in Kathmandu valley, Nepal.

METHODS

Between September 2011 and May 2012, during the nine months period, 6308 MSU specimens were collected aseptically from the same number of clinically suspected patients of urinary tract infections. The samples were cultured on MacConkey agar and blood agar. The isolates with significant bacteriuria (105 CFU / ml) were identified based on standard laboratory procedures. Antimicrobial susceptibility tests were carried out using various antimicrobial discs alongwith ceftriaxone on E.coli and K. pneumoniae isolates by Kirby Bauer disc diffusion method as per the recommendations of CLSI. On initial screening with ceftriaxone (30 μg) disc showing resistance was then confirmed for ESBL production by phenotypic confirmatory disc diffusion test (PCDDT) using ceftazidime (30 ug) and ceftazidime + clavulanic acid (30 μg + 10ug) disc as per guidelines of CLSI (2011).

RESULTS

Out of a total of 6308 MSU specimens investigated for significant bacteriuria, E.coli isolates were 444 (7.04%) and K.pneuminiae were 145 (2.3%) making a total of 589 (9.34%). Initial screening with ceftriaxone disc revealed 155 isolates of E.coli and 70 isolates of K.pneumoniae to be resistant. Further testing by PCDDT method showed 60/444 (=13.51%) of E. coli and 24/145 (=16.55%) of K. pneumoniae isolates to be confirmed ESBL producers. These ESBL - producer uropathogens showed high degree of resistance to ceftriaxone (100.0%), amoxycillin, fluoroquinolones and co-trimoxazole.

CONCLUSION

An emerging and moderately high prevalence of ESBL-producing E. coli and K. pneumoniae was observed and confirmed in the urinary isolates investigated. It is essential to have a regular and routine monitoring of ESBL producing clinical isolates in laboratory practice.

Impact of extended-spectrum beta-lactamase on acute pyelonephritis treated with empirical ceftriaxone

BACKGROUND

Ceftriaxone is frequently administered empirically for hospitalized patients with acute pyelonephritis (APN) due to prevalent quinolone resistance in our hospital; however, its use is inappropriate for extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli, an increasing problem.

METHODS

A retrospective, 1:2 matched cohort study was performed to evaluate the impact of ESBL on APN treated with empirical ceftriaxone. Each patient in ESBL group was matched with two patients in the non-ESBL group, using a 16-point scoring system, which included age, sex, bacteremia, simplified acute physiology score 2, Charlson comorbidity index and APN severity score.

RESULTS

From 2009 to 2011, among 1,322 community-onset cases of the E. coli bacteriuria with 212 (16%) ESBL producers, 261 patients with APN were treated empirically with ceftriaxone in a secondary care hospital. Among these 261 cases, twenty-six patients in the ESBL group and 52 matched patients in the non-ESBL group (1:2) were included. Mean time to defervescence was 4.6±2.2 days in the ESBL group and 2.6±1.3 days in the non-ESBL group (p<0.01). Rate of microbiological resolution within 5 days after antibiotic treatment was 77% (17/22) in the ESBL group and 100% (45/45) in the non-ESBL group (p=0.01). The duration of hospitalization was 13.3±8.2 days in the ESBL group and 7.3±3.5 days in the non-ESBL group (p<0.01). No patient died in either group.

CONCLUSION

Empirical ceftriaxone therapy for APN caused by ESBL-producing E. coli is inappropriate, and consequently can delay recovery and result in longer hospitalization.

Liver abscesses in adult patients with and without diabetes mellitus: an analysis of the clinical characteristics, features of the causative pathogens, outcomes and predictors of fatality: a report based on a large population, retrospective study in China

In China, there are four types of liver abscesses (LAs) that meet the clinical criteria. Pyogenic liver abscesses (PLAs) and amoebic liver abscesses (ALAs) are two of the most common types of abscesses, followed by fungal liver abscesses (FLAs) and hydatid secondary liver abscesses (HsLAs). Diabetes mellitus (DM) is associated with the development of PLAs. However, there is a lack of population-based studies that have evaluated the underlying relationship between LAs (mainly PLAs and FLAs) and DM. We conducted a retrospective study based on a large population to identify the potential differences and factors that affect the mortality of PLA patients in DM and non-DM groups. Our results revealed that the prevalence of DM is 44.3% (158/357) in PLA patients and 35.3% (18/51) in FLA patients. Compared with the non-DM patients, statistically significant differences were found in DM patients according to symptomatology, clinical manifestations, laboratory findings, microbiological characteristics, antimicrobial resistance, clinical treatments and outcomes in relation to mortality. In addition, the status of antibiotic resistance to E. coli and K. pneumoniae, which were isolated from the patient samples, is severe in the area in which the study was conducted. Regarding the treatment of PLAs, our study indicated that broad-spectrum antimicrobial therapy and drug combinations should be recommended and initiated before the pathogens are cultured and identified. In the clinic, therapies that combine percutaneous drainage with antibiotics and surgery with antibiotics are the two most useful strategies for treating an LA. These two combined treatments resulted in satisfactory cure rates. In the DM and non-DM groups, the cure rates for percutaneous drainage with antibiotics were 90.3% and 92.0%, respectively, and the cure rates for surgery with antibiotics were 93.9% and 95.2%, respectively.

Emergence of community-acquired extended-spectrum beta-lactamase Escherichia coli (ESBLEC) in Honolulu: a case series of three individuals with community-acquired ESBLEC bacteriuria

Community-acquired extended-spectrum beta-lactamase E coli (ESBLEC) have not been previously described in Honolulu. Its emergence as a community-acquired pathogen is concerning. This case series describes three patients who were diagnosed with community-acquired ESBLEC bacteriuria in 2010.

Rapid functional definition of extended spectrum β-lactamase activity in bacterial cultures via competitive inhibition of fluorescent substrate cleavage

The functional definition of extended-spectrum β-lactamase (ESBL) activity is a clinical challenge. Here we report a rapid and convenient assay of β-lactamase activity through the competitive inhibition of fluorescent substrate hydrolysis that provides a read-out nearly 40× more rapidly than conventional techniques for functional definition. A panel of β-lactam antibiotics was used for competition against β-lactamase enzyme-activated photosensitizer (β-LEAP) yielding a competitive index (C(i)) in 30 min. Significant differences in the relative C(i) values of the panel of β-lactams were determined in vitro for Bacillus cereus penicillinase. Additionally, the relative C(i) values for whole bacterial cell suspensions of B. cereus 5/β were compared with the relative minimal inhibitory concentration (MIC) values and a correlation coefficient of 0.899 was determined. We further demonstrated the ability of β-LEAP to probe the capacity of ceftazidime to inhibit the enzyme activity of a panel of ESBL-producing Escherichia coli. The bacteria were assayed for susceptibility to ceftazidime and the relative MIC values were compared with the relative C(i) values for ceftazidime yielding a correlation coefficient of 0.984. This work demonstrates for the first time the whole cell assay of the competitive inhibition of β-lactamase enzyme activity and derivation of associated constants.

Klebsiella and extended spectrum beta-lactamases

During the past 14 years a rapid, world-wide increase in prevalence of Klebsiella pneumoniae resistant to late generation cephalosporins has occurred. A growing number of newly identified plasmid encoded beta-lactam hydrolyzing enzymes has broadened the spectrum of primitive beta-lactamases allowing inactivation of a wide variety of beta-lactam agents. The extrachromosomal genes which code for these enzymes often exist with genes expressing resistance to several other classes of antibacterial agents, potentially arming Klebsiella pneumoniae with resistance to all therapeutically available antibiotics. More focused surveillance studies and individualized strategies within institutions are necessary to reduce this insidious trend.

Risk factors in community-acquired urinary tract infections caused by ESBL-producing bacteria in children

In this study, risk factors were investigated in children with community-acquired urinary tract infections (UTI) caused by extended-spectrum beta-lactamases (ESBL)-producing E. coli or Klebsiella spp. One hundred and fifty-five patients were diagnosed with ESBL-positive UTI (case group) in the outpatient clinics of Hacettepe University Children's Hospital between 1 January 2004 and 31 December 2006. A control group, 155 out of 4,105 children, was matched by age and sex among children with ESBL-negative UTI. A total of 310 patients' files were evaluated retrospectively. As regards the symptoms of UTI, no statistical differences were seen between the two groups. Although the most frequently isolated microorganism was E. coli in both groups, Klebsiella spp. was found to be more frequent in those diagnosed with ESBL(+) UTI (p < 0.001). Having an underlying disease and hospitalization, infections, and use of antibiotics within the last 3 months were found to be potential risk factors (p < 0.001). With conditional logistic regression analysis, having an underlying disease and hospitalization within the last 3 months were identified as independent risk factors for ESBL(+) UTI. In conclusion, the recognition of risk factors for UTI, caused by ESBL(+) bacteria in children, may aid in the identification of high-risk cases and may enable proper management of these patients.

Three decades of beta-lactamase inhibitors

Since the introduction of penicillin, beta-lactam antibiotics have been the antimicrobial agents of choice. Unfortunately, the efficacy of these life-saving antibiotics is significantly threatened by bacterial beta-lactamases. beta-Lactamases are now responsible for resistance to penicillins, extended-spectrum cephalosporins, monobactams, and carbapenems. In order to overcome beta-lactamase-mediated resistance, beta-lactamase inhibitors (clavulanate, sulbactam, and tazobactam) were introduced into clinical practice. These inhibitors greatly enhance the efficacy of their partner beta-lactams (amoxicillin, ampicillin, piperacillin, and ticarcillin) in the treatment of serious Enterobacteriaceae and penicillin-resistant staphylococcal infections. However, selective pressure from excess antibiotic use accelerated the emergence of resistance to beta-lactam-beta-lactamase inhibitor combinations. Furthermore, the prevalence of clinically relevant beta-lactamases from other classes that are resistant to inhibition is rapidly increasing. There is an urgent need for effective inhibitors that can restore the activity of beta-lactams. Here, we review the catalytic mechanisms of each beta-lactamase class. We then discuss approaches for circumventing beta-lactamase-mediated resistance, including properties and characteristics of mechanism-based inactivators. We next highlight the mechanisms of action and salient clinical and microbiological features of beta-lactamase inhibitors. We also emphasize their therapeutic applications. We close by focusing on novel compounds and the chemical features of these agents that may contribute to a "second generation" of inhibitors. The goal for the next 3 decades will be to design inhibitors that will be effective for more than a single class of beta-lactamases.

Epidemiology of an outbreak of antibiotic-resistant Klebsiella pneumoniae at a tertiary care medical center

BACKGROUND

In 2004, a 650-bed, tertiary care medical center experienced an outbreak of multiple antibiotic-resistant Klebsiella pneumoniae (MR-KP) that included extended-spectrum beta-lactamase (ESBL)-producing and non-ESBL-producing strains.

METHODS

Characteristics associated with MR-KP were evaluated by case-control study with variables tested by conditional regression analyses. Pulsed-field gel electrophoresis (PFGE) was used to compare the molecular relatedness of isolates.

RESULTS

In 2004, the incidence rate of MR-KP increased significantly compared with 2003 (relative risk [RR], 5.1; 95% confidence interval [CI]: 3.10-8.37) when only ESBL-producing K pneumoniae were present. The increase involved both ESBL-producing MR-KP and MR-KP in which ESBL production was not detected by the testing in use. Nineteen isolates were identical or closely related by PFGE. Characteristics associated with MR-KP were longer length of hospital stay (odds ratio [OR], 2.92; 95% CI: 1.17-7.30; P = .022), greater total antibiotic-days (OR, 2.81; 95% CI: 1.19-6.65; P = .018], and higher Acute Physiology and Chronic Health Evaluation (APACHE) II score (OR, 1.15; 95% CI: 1.06-1.25; P = .001). When the MR-KP cases were subdivided into ESBL-producing K pneumoniae and ESBL-negative K pneumoniae, while controlling for length of stay, total antibiotic-days was significantly associated with ESBL-producing K pneumoniae (OR, 3.8; 95% CI: 1.2-12.1; P = .02).

CONCLUSION

Compared with patients housed on the same unit at the same time, patients with MR-KP had a longer length of stay and greater antibiotic exposure. Patients with longer length of stay and greater total antibiotic exposure should be potential targets for stringent infection control measures.

Clinical impact of infections caused by ESBL-producing E. coli and K. pneumoniae

The outcome of infections occurring at different anatomic sites caused by ESBL-producing E. coli or K. pneumoniae was retrospectively analysed for a 3-y period. 23 cases were compared to 46 controls with infections caused by third-generation cephalosporin-susceptible strains matched by age, severity of illness and duration of hospitalization before onset of infection. Only 27.8% of cases received appropriate empirical antimicrobial therapy compared with 79.6% of controls (OR(paired)=0.053, p=0.001). This did not result in higher costs of antibiotic therapy, a longer median post-infection hospital stay or higher mortality in cases of patients with urinary tract or wound infections. In cases of patients with respiratory tract and bloodstream infections (RTI/BSI), median costs of definitive antibiotic treatment were significantly higher than in controls (325 vs 58.9 Euros, p=0.002). Moreover, more case patients with RTI/BSI had a post-infection stay exceeding the 75th percentile of 15 d on ICU and of 18 d in hospital, respectively (50% vs 6.67%, p=0.034). There was no difference in in-hospital mortality between case and control patients with RTI/BSI (25% vs 20%, p=1.0).

Risk factors of nosocomial infection with extended-spectrum beta-lactamase-producing bacteria in a neonatal intensive care unit in China

BACKGROUND

To study risk factors of neonatal nosocomial infection caused by extended-spectrum beta-lactamase (ESBL)-producing bacteria in a neonatal intensive care unit (NICU).

PATIENTS AND METHODS

A retrospective cohort study was conducted in a university hospital NICU in south China. Medical records of neonatal nosocomial infection caused by Escherichia coli or Klebsiella pneumoniae were reviewed. Twenty-two neonates infected with ESBL-producing bacteria (case patients) were compared with 17 patients infected with non-ESBL producing strains (controls). Univariable and multivariable logistic regression were performed to analyze risk factors for infection with ESBL-producing strains. The spectrum of antimicrobial resistance of ESBL-positive E. coli or K. pneumoniae was also examined.

RESULTS

Both univariable and multivariable logistic regression analysis revealed that preterm low birth weight, prolonged mechanical ventilation (> or = 7 days) and prior use of third-generation cephalosporins were risks factors for ESBL-producing E. coli or K. pneumoniae infection (p < 0.05), with an odd ratio of 6.43 (95% CI: 1.51-27.44; p = 0.017), 7.50 (95% CI: 1.38-40.88; p = 0.017) and 9.00 (95% CI: 1.65-49.14; p = 0.008) respectively. However, the length of hospital stay before isolation of pathogens, endotracheal intubation, presence of a central venous catheter, days on third-generation cephalosporins and prior use of beta-lactamase inhibitors were not statistically significant (p > 0.05). Resistance of ESBL-positive strains to piperacillin, tobramycin, aztreonam and cephalosporins was significantly higher than that of ESBL-negative ones (p < 0.05). ESBL-producing strains appeared susceptible to carbapenem, fluoroquinolones, and beta-lactamase inhibitor combination piperacillin-tazobactam.

CONCLUSIONS

Preterm low birth weight, prolonged mechanical ventilation and prior use of third-generation cephalosporins are risks factors for nosocomial infection with ESBL-producing bacteria in NICU.

Clinico-epidemiological features of infections caused by CTX-M type extended spectrum beta lactamase-producing Escherichia coli in hospitalised patients

A review of medical records of 45 of 53 hospitalised patients with positive cultures for CTX-M type ESBL-producing Escherichia coli between 01 January and 31 May 2004 was conducted. The mean age of the population studied was 73.1 (+/-14.6) years and the majority (55.6%) had been under the care of the internal medicine or elderly care service. In the majority (77.8%) of instances the isolate was attributed to a clinical infection rather than colonisation and the commonest clinical specimen to yield the organism was urine, which was positive in 57.8% of patients. Acquisition of the organism was categorised as nosocomial in 68.9% of patients; in this subgroup, the median duration of inpatient stay prior to recovery of the organism was 24 (range 3-240) days. Haemodialysis-dependence was the most common of the comorbidities evaluated. The mean number of antibiotics prescribed per patient in the 30 days prior to first isolation of the organism was 1.7 (range 0-4). Furthermore, the mean number of antibiotic-days exposure per patient during this period was 13.9 (range 0-48). The most frequently received class of antibiotic was beta-lactam/beta-lactamase inhibitor combinations. Of 35 infections, 26 (74.2%) were successfully treated. Overall 12 patients with infection died (34.3%); attributable mortality was presumed in seven (20%).

Outcome of cephalosporin treatment of bacteremia due to CTX-M–type extended-spectrum β-lactamase–producing Escherichia coli

The aim of the study was to analyze the outcome of different antibiotic treatments for bacteremia due to CTX-M-type extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli. In a prospective controlled clinical study from October 2002 to April 2005, 22 consecutive cases of bacteremia due to ESBL-producing E. coli with a ceftazidime-inhibition zone diameter of > or =18 mm were studied. The Etest method was used to determine the MIC values of cefotaxime, ceftazidime, imipenem, gentamicin, and ciprofloxacin against 22 isolates of E. coli. The polymerase chain reaction and sequencing analyses were used to determine the genotypes of the ESBLs. Of these 22 episodes, 7 were treated with ceftazidime, 8 were treated with imipenem/cilastatin, and 7 were treated with cefoperazone/sulbactam after detection of bacteremia. The demographic characteristics were comparable between the 3 groups. The treatment success ratio was similar (ceftazidime 85.7%, imipenem/cilastatin 87.5%, cefoperazone/sulbactam 71.4%, P = 0.637). Difficulties arose during treatment of peritonitis caused by CTX-M-producing E. coli bacteremia. Patients with bacteremia associated with urinary tract infection or biliary tract infection had a better chance of survival. All the 22 strains of E. coli produced CTX-M ESBLs (CTX-M-3, CTX-M-14, or CTX-M-27). The MICs of ceftazidime for 22 strains of E. coli were < or =8 microg/mL. All 7 patients who received ceftazidime survived, 6 of them were cured. Treatment in one patient with a ceftazidime MIC of 2 mug/mL failed because of abdominal abscess. Treatment with ceftazidime in vivo was effective against cases of CTX-M ESBL-producing E. coli bacteremia due to urinary tract infections and biliary tract infection when the MICs of ceftazidime were < or =8 microg/mL.

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.

Predictors of mortality in patients with bloodstream infection due to ceftazidime-resistant Klebsiella pneumoniae

Bloodstream infection (BSI) due to multidrug-resistant Klebsiella is associated with high rates of morbidity and mortality. The aim of this study was to identify predictors of in-hospital mortality among patients with BSI due to ceftazidime-resistant (CAZ-R) Klebsiella pneumoniae at a tertiary care medical center. Patients with CAZ-R K. pneumoniae BSI were identified by our microbiology laboratory between January 1995 and June 2003. Clinical data were collected retrospectively. Logistic regression was used to identify independent predictors of all causes of in-hospital mortality. Of 779 patients with K. pneumoniae BSI, 60 (7.7%) had BSI due to CAZ-R K. pneumoniae; 43 (72%) of these were nosocomial infections. Pulsed-field gel electrophoresis identified a single predominant strain in 17 (28%) patients. The in-hospital mortality rate was 43% (n = 26). Among patients with CAZ-R K. pneumoniae BSI, those who died were similar to survivors with respect to demographic, clinical, and antimicrobial susceptibility characteristics. Only 43 (72%) patients received effective therapy within 5 days of BSI. In bivariable analysis, delay in initiation of effective therapy for >72 h after diagnosis of BSI was associated with death (P = 0.03). Strain genotype was not predictive of outcome. In multivariable analysis, delay in initiation of effective therapy for >72 h after diagnosis of BSI was an independent predictor of death (odds ratio, 3.32; 95% confidence interval, 1.07 to 10.3). Thus, among patients with BSI due to CAZ-R K. pneumoniae, a delay in the initiation of effective therapy of greater than 72 h after BSI was associated with a >3-fold increase in mortality risk.

Clinical outcome and risk factors related to extended-spectrum beta-lactamase-producing Klebsiella spp. infection among hospitalized patients

Over the past two decades, nosocomial infections caused by extended-spectrum beta-lactamase (ESBL)-producing Klebsiella spp. have become a major problem all around the world. This situation is of concern because there are limited antimicrobial options to treat patients infected with these pathogens, and also because this kind of resistance can spread to a wide variety of Gram-negative bacilli. Our objectives were to evaluate among in-patients at a public university tertiary-care hospital with documented infection due to Klebsiella spp., which were the risk factors (cross-sectional analysis) and the clinical impact (prospective cohort) associated with an ESBL-producing strain. Study subjects were all patients admitted at the study hospital between April 2002 and October 2003, with a clinically and microbiologically confirmed infection caused by Klebsiella spp. at any body site, except infections restricted to the urinary tract. Of the 104 patients studied, 47 were infected with an ESBL-producing strain and 57 with a non-ESBL-producing strain. Independent risk factors associated with infection with an ESBL-producing strain were young age, exposure to mechanical ventilation, central venous catheter, use of any antimicrobial agent, and particularly use of a 4th generation cephalosporin or a quinolone. Length of stay was significant longer for patients infected with ESBL-producing strains than for those infected with non-ESBL-producing strains, although fatality rate was not significantly affected by ESBL-production in this cohort. In fact, mechanical ventilation and bacteremia were the only variables within dependent association with death detected in this investigation.

Extended-spectrum beta-lactamases: a clinical update

Extended-spectrum beta-lactamases (ESBLs) are a rapidly evolving group of beta-lactamases which share the ability to hydrolyze third-generation cephalosporins and aztreonam yet are inhibited by clavulanic acid. Typically, they derive from genes for TEM-1, TEM-2, or SHV-1 by mutations that alter the amino acid configuration around the active site of these beta-lactamases. This extends the spectrum of beta-lactam antibiotics susceptible to hydrolysis by these enzymes. An increasing number of ESBLs not of TEM or SHV lineage have recently been described. The presence of ESBLs carries tremendous clinical significance. The ESBLs are frequently plasmid encoded. Plasmids responsible for ESBL production frequently carry genes encoding resistance to other drug classes (for example, aminoglycosides). Therefore, antibiotic options in the treatment of ESBL-producing organisms are extremely limited. Carbapenems are the treatment of choice for serious infections due to ESBL-producing organisms, yet carbapenem-resistant isolates have recently been reported. ESBL-producing organisms may appear susceptible to some extended-spectrum cephalosporins. However, treatment with such antibiotics has been associated with high failure rates. There is substantial debate as to the optimal method to prevent this occurrence. It has been proposed that cephalosporin breakpoints for the Enterobacteriaceae should be altered so that the need for ESBL detection would be obviated. At present, however, organizations such as the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards) provide guidelines for the detection of ESBLs in klebsiellae and Escherichia coli. In common to all ESBL detection methods is the general principle that the activity of extended-spectrum cephalosporins against ESBL-producing organisms will be enhanced by the presence of clavulanic acid. ESBLs represent an impressive example of the ability of gram-negative bacteria to develop new antibiotic resistance mechanisms in the face of the introduction of new antimicrobial agents.

Multidrug resistance in Gram-negative bacteria that produce extended-spectrum beta-lactamases (ESBLs)

In 1983, just two years after the introduction of the oxymino-beta-lactams to the market , the first extended-spectrum beta-lactamases were isolated in Germany from Klebsiella pneumoniae strains. Since then several outbreaks have been reported in many European countries and the USA, and nowadays in several places worldwide the problem seems to reach endemic dimensions, with rates exceeding 50% in some countries, such as Portugal and Turkey. On the other hand not only K. pneumoniae but also Escherichia coli strains, with Enterobacter aerogenes predominating among the other enterobacteriaceal species, are increasingly reported as ESBL producers. In this review types, molecular characteristics, detection methods, epidemiology as well as interventions for therapy and antibiotic strategies to prevent and control infections caused by ESBL-producing microorganisms, are presented and discussed.

Long-term study of the frequency of Escherichia coli and Klebsiella pneumoniae isolates producing extended-spectrum β-lactamases

In total, 438 (1.7%) Escherichia coli and 125 (3.98%) Klebsiella pneumoniae isolates were found to be producers of extended-spectrum beta-lactamase (ESBL) during 1995-2003 in southern Spain. There was a significant increase in the frequency of ESBL-producing E. coli isolates, from < 0.36% before 1999 to 4.8% in 2003, while the frequency of ESBL-producing K. pneumoniae isolates decreased during the same period. The most common ESBLs detected in K. pneumoniae were SHV type, whereas both CTX-M and SHV types were detected in E. coli. In addition, E. coli isolates showed greater clonal diversity (84 distinct REP-PCR patterns, compared with five in K. pneumoniae), fewer enzymes per isolate, and a higher number of isolates recovered from outpatients. These differences may have implications for the control measures that should be used for these two microorganisms.

Bloodstream infections due to extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae: risk factors for mortality and treatment outcome, with special emphasis on antimicrobial therapy

This study was conducted to evaluate risk factors for mortality and treatment outcome of bloodstream infections due to extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae (ESBL-EK). ESBL production in stored K. pneumoniae and E. coli blood isolates from Jan 1998 to Dec 2002 was phenotypically determined according to NCCLS guidelines and/or the double-disk synergy test. A total of 133 patients with ESBL-EK bacteremia, including 66 patients with ESBL-producing K. pneumoniae and 67 with ESBL-producing E. coli, were enrolled. The overall 30-day mortality rate was 25.6% (34 of 133). Independent risk factors for mortality were severe sepsis, peritonitis, neutropenia, increasing Acute Physiology and Chronic Health Evaluation II score, and administration of broad-spectrum cephalosporin as definitive antimicrobial therapy (P < 0.05 for each of these risk factors). In 117 of the 133 patients, excluding 16 patients who died within 3 days after blood culture sample acquisition, the 30-day mortality rates according to definitive antibiotics were as follows: carbapenem, 12.9% (8 of 62); ciprofloxacin, 10.3% (3 of 29); and others, such as cephalosporin or an aminoglycoside, 26.9% (7 of 26). When patients who received appropriate definitive antibiotics, such as carbapenem or ciprofloxacin, were evaluated, mortality in patients receiving inappropriate empirical antimicrobial therapy was found not to be significantly higher than mortality in those receiving appropriate empirical antimicrobial therapy (18.9 versus 15.5%; P = 0.666). Carbapenem and ciprofloxacin were the most effective antibiotics in antimicrobial therapy for ESBL-EK bacteremia. A delay in appropriate definitive antimicrobial therapy was not associated with higher mortality if antimicrobial therapy was adjusted appropriately according to the susceptibility results. Our data suggest that more prudent use of carbapenem as empirical antibiotic may be reasonable.

Bloodstream infections due to extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae: risk factors for mortality and treatment outcome, with special emphasis on antimicrobial therapy

This study was conducted to evaluate risk factors for mortality and treatment outcome of bloodstream infections due to extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae (ESBL-EK). ESBL production in stored K. pneumoniae and E. coli blood isolates from Jan 1998 to Dec 2002 was phenotypically determined according to NCCLS guidelines and/or the double-disk synergy test. A total of 133 patients with ESBL-EK bacteremia, including 66 patients with ESBL-producing K. pneumoniae and 67 with ESBL-producing E. coli, were enrolled. The overall 30-day mortality rate was 25.6% (34 of 133). Independent risk factors for mortality were severe sepsis, peritonitis, neutropenia, increasing Acute Physiology and Chronic Health Evaluation II score, and administration of broad-spectrum cephalosporin as definitive antimicrobial therapy (P < 0.05 for each of these risk factors). In 117 of the 133 patients, excluding 16 patients who died within 3 days after blood culture sample acquisition, the 30-day mortality rates according to definitive antibiotics were as follows: carbapenem, 12.9% (8 of 62); ciprofloxacin, 10.3% (3 of 29); and others, such as cephalosporin or an aminoglycoside, 26.9% (7 of 26). When patients who received appropriate definitive antibiotics, such as carbapenem or ciprofloxacin, were evaluated, mortality in patients receiving inappropriate empirical antimicrobial therapy was found not to be significantly higher than mortality in those receiving appropriate empirical antimicrobial therapy (18.9 versus 15.5%; P = 0.666). Carbapenem and ciprofloxacin were the most effective antibiotics in antimicrobial therapy for ESBL-EK bacteremia. A delay in appropriate definitive antimicrobial therapy was not associated with higher mortality if antimicrobial therapy was adjusted appropriately according to the susceptibility results. Our data suggest that more prudent use of carbapenem as empirical antibiotic may be reasonable.

Determining incidence of extended spectrum β-lactamase producing Enterobacteriaceae, vancomycin-resistant Enterococcus faecium and methicillin-resistant Staphylococcus aureus in 38 centres from 17 countries: the PEARLS study 2001–2002

The PEARLS study prospectively monitored selected nosocomial pathogens from 38 centres in 13 European, three Middle Eastern countries and South Africa during 2001-2002. Extended spectrum beta-lactamase (ESBL) production rates among Escherichia coli, Klebsiella pneumoniae, and Enterobacter spp. were 5.4% (142/2609), 18.2% (401/2,206) and 8.8% (204/2,328), respectively, for all study sites. The overall ESBL production rate for the combined Enterobacteriaceae was 10.5% (747/7,143), highest in Egypt, 38.5%, and Greece, 27.4%, and lowest in The Netherlands, 2.0%, and Germany, 2.6%. IEF, PCR and DNA sequencing determined 10.7% false positives among Enterobacter spp. when using NCCLS guidelines to screen for ESBL production. The prevalence of nosocomial methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium was 32.4% (294/908) and 8.7% (83/949), respectively. PEARLS provides baseline data against which prospective changes in resistant determinants and outcomes can be measured in this ongoing study.

Effects of inoculum and beta-lactamase activity in AmpC- and extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae clinical isolates tested by using NCCLS ESBL methodology

Escherichia coli and Klebsiella pneumoniae isolates with extended-spectrum beta-lactamases (ESBLs) or AmpC cephalosporinases generally respond as predicted to NCCLS tests for ESBL production. However, inoculum size may affect MICs. The effect of inoculum level in clinical isolates expressing beta-lactamases were studied at inocula within 0.5 log unit of the standard inoculum, using broth microdilution methodology with ceftazidime, cefotaxime, cefepime, cefpodoxime, and aztreonam. Strains with TEM-1 or no beta-lactamases gave consistent MIC results with inocula of 10(5) and 10(6) CFU/ml. When the bacteria were screened for ESBL production and the lower inoculum was used, several strains with ESBLs, including CTX-M-10, TEM-3, TEM-10, TEM-12, TEM-6, SHV-18, and K1, gave false-negative results for one or more antimicrobial agents (MICs below the NCCLS screening concentration for detecting suspected ESBLs). When the higher inoculum was used, MICs of at least one antimicrobial agent increased at least fourfold in strains producing TEM-3, TEM-10, TEM-28, TEM-43, SHV-5, SHV-18, and K1. All antimicrobial agents showed an inoculum effect with at least one ESBL producer. Confirmatory clavulanate effects were seen for both inocula for all ESBL-producing strains with all antimicrobial agents tested, except for the CTX-M-10-producing E. coli with ceftazidime and the SHV-18-producing K. pneumoniae with cefotaxime. In kinetic studies, cefpodoxime and cefepime were hydrolyzed by ESBLs in a manner similar to that of cefotaxime. When total beta-lactamase activity and hydrolysis parameters were evaluated, however, no single factor was predictive of inoculum effects. These results indicate that the NCCLS screening and confirmation tests are generally predictive of ESBL production, but false-negative results can arise when a lower inoculum is used in testing.

Extended spectrum beta lactamase-producing Klebsiella pneumoniae infections: a review of the literature

Infections caused by extended-spectrum beta-lactamase (ESBL)-producing pathogens, particularly Klebsiella pneumoniae, are increasing. The epidemiology of ESBL-producing K. pneumoniae, the mechanisms of resistance, and treatment strategies for infections caused by these organisms are reviewed.

Prevalence of extended-spectrum beta-lactamase-producing Gram-negative bacteria in septicaemic neonates in a tertiary care hospital

The present study was undertaken to investigate the high incidence of multiresistant Gram-negative bacilli causing neonatal septicaemia. Samples of neonatal blood from 728 suspected cases were obtained in brain heart infusion broth with sodium polyanethol sulfonate. All Gram-negative rods isolated were subsequently subjected to routine antimicrobial susceptibility testing and tests for extended-spectrum beta-lactamase (ESBL) production, as per NCCLS recommendations. ESBL was detected in 86.6% of Klebsiella spp., 73.4% of Enterobacter spp. and 63.6% of Escherichia coli strains. It was also observed that 74.4-80.9% of these ESBL producers were resistant to cefotaxime and 47.6-59.5% were resistant to ceftazidime in routine susceptibility testing. Some ESBL producers (36.3-61.5%) were found to be susceptible to either or both cephalosporins used in this study. It is concluded that indiscriminate use of third-generation cephalosporins may be responsible for the selection of ESBL-producing multiresistant strains in the neonatal intensive-care unit (NICU).

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

Extended spectrum beta-lactamase (ESBL)-producing organisms pose unique challenges to clinical microbiologists, clinicians, infection control professionals and antibacterial-discovery scientists. ESBLs are enzymes capable of hydrolysing penicillins, broad-spectrum cephalosporins and monobactams, and are generally derived from TEM and SHV-type enzymes. ESBLs are often located on plasmids that are transferable from strain to strain and between bacterial species. Although the prevalence of ESBLs is not known, it is clearly increasing, and in many parts of the world 10-40% of strains of Escherichia coli and Klebsiella pneumoniae express ESBLs. ESBL-producing Enterobacteriaceae have been responsible for numerous outbreaks of infection throughout the world and pose challenging infection control issues. Clinical outcomes data indicate that ESBLs are clinically significant and, when detected, indicate the need for the use of appropriate antibacterial agents. Unfortunately, the laboratory detection of ESBLs can be complex and, at times, misleading. Antibacterial choice is often complicated by multi-resistance. Many ESBL-producing organisms also express AmpC beta-lactamases and may be co-transferred with plasmids mediating aminoglycoside resistance. In addition, there is an increasing association between ESBL production and fluoroquinolone resistance. Although in in vitro tests ESBLs are inhibited by beta-lactamase inhibitors such as clavulanic acid, the activity of beta-lactam/beta-lactamase inhibitor combination agents is influenced by the bacterial inoculum, dose administration regimen and specific type of ESBL present. Currently, carbapenems are regarded as the drugs of choice for treatment of infections caused by ESBL-producing organisms. Unfortunately, use of carbapenems has been associated with the emergence of carbapenem-resistant bacterial species such as Stenotrophomonas sp. or Pseudomonas sp.

[Risk factors associated with ceftazidime-resistant Klebsiella pneumoniae infection]

INTRODUCTION

Risk factors associated with ceftazidime-resistant Klebsiella pneumoniae (CAZ-R Kp) infection may vary among hospitals and in the same hospital at different time points. Knowledge of these factors is required to establish suitable infection control programs.

METHODS

A case-control study was conducted to assess risk factors for CAZ-R Kp infection. Thirty-two cases were compared with 28 controls admitted to a 200-bed general hospital during 1999 and 2000.

RESULTS

In the univariate analysis Kp CAZ-R isolates were significantly associated with nosocomial acquisition (OR 5 17.40), prior antibiotic use (OR 5 14.94), particularly ciprofloxacin use (OR 5 5), and hospitalization stay of more than 6 days (OR 5 6.72). Significantly associated variables in the logistic regression analysis included nosocomial acquisition (OR 5 9.29), prior antibiotic use (OR 5 6.21), and particularly, ciprofloxacin use (OR 5 10.84).

CONCLUSIONS

Efforts toward more rational overall antibiotic use and particularly ciprofloxacin use, combined with infection control measures are necessary to decrease the prevalence of CAZ-R Kp in our hospital.

Hospital-acquired infections in the neonatal intensive care unit--Klebsiella pneumoniae

Klebsiella pneumoniae is medically the most important organism of the Klebsiella species. It is responsible for a significant proportion of hospital-acquired infections including septicemias, urinary tract infections, pneumonia, and soft tissue infections especially in the immunocompromised hosts such as the neonate. The hands of healthcare workers and the gastrointestinal tract of hospitalized infants serve as reservoirs for the transmission of the organism and are responsible for multiple hospital outbreaks. In recent years, there has been an increase in the incidence of outbreaks caused by multidrug resistance K. pneumoniae organisms or the extended spectrum beta-lactamase (ESBL)-producing K. pneumoniae. The problems associated with extended spectrum beta-lactamase-producing organisms include difficulties in accurate antimicrobial susceptibility testing, limited treatment options and increased morbidity and perhaps mortality. Hence, prevention through implementation of strict infection control guidelines, effective hand washing and judicious use of antimicrobials such as third generation cephalosporins is important to effectively reduce the morbidity associated with this infection.

Antimicrobial use prior to the acquisition of multiresistant bacteria

We assessed whether patients who acquired methicillin-resistant Staphylococcus aureus (MRSA) had less exposure to antimicrobial agents than did those who acquired Enterobacteriaceae that produced extended-spectrum beta-lactamase (ESbetaL). In a 6-month, prospective study, ESbetaL carriers had received antimicrobial therapy more often than had MRSA carriers. Amoxicillin-clavulanic acid, fluoroquinolones, and third-generation cephalosporins, especially ceftazidime, had been prescribed more often for ESbetaL carriers than for MRSA carriers.

Molecular correlation for the treatment outcomes in bloodstream infections caused by Escherichia coli and Klebsiella pneumoniae with reduced susceptibility to ceftazidime

Data are limited on outcomes of treatment with extended-spectrum cephalosporins (ESCs) for infections caused by Enterobacteriaceae that produce extended-spectrum beta-lactamases (ESBLs). This study describes the largest treatment experience of a nonoutbreak series of bloodstream infections caused by strains of Escherichia coli (23 episodes) and Klebsiella pneumoniae (13 episodes) with a ceftazidime minimal inhibitory concentration of > or =2 microg/mL. E. coli isolates produced a greater variety of beta-lactamase types than did K. pneumoniae isolates, among which ESBL production was predominant. Five ESBL types were identified: TEM-12, TEM-71, TEM-6, SHV-12, and SHV-5. Most patients were treated empirically with an ESC-based regimen. A favorable response to treatment with a nonceftazidime ESC was observed when the causative pathogen produced either TEM-6 or TEM-12; ceftazidime treatment was associated with failure of therapy in all patients. Despite the limited clinical success, ESCs are currently not recommended for the treatment of serious infections caused by ESBL-producing strains.

The effect of an antimicrobial formulary change on hospital resistance patterns

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

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.