Extended-spectrum beta-lactamase-producing Enterobacteriaceae: an emerging public-health concern

Using a commercial DiversiLab semiautomated repetitive sequence-based PCR typing technique for identification of Escherichia coli clone ST131 producing CTX-M-15

A study was designed to evaluate the ability of the DiversiLab fingerprinting kit, a type of repetitive element PCR (rep-PCR), to identify Escherichia coli clone ST131 producing beta-lactamase CTX-M-15. A set of 53 nonduplicate isolates of extended-spectrum beta-lactamase-producing E. coli underwent rep-PCR, pulsed-field gel electrophoresis, and multilocus sequence typing. The DiversiLab system successfully identified E. coli clone ST131 producing CTX-M-15 and provides a simple standardized typing protocol for monitoring the spread of this clone.

Highly resistant microorganisms in a teaching hospital: the role of horizontal spread in a setting of endemicity

OBJECTIVE

To determine the incidence density of highly resistant organisms (HROs) and the relative contribution of horizontal spread in a setting of endemicity.

METHODS

Prospective surveillance was performed among hospitalized patients during an 18-month period. Enterobacteriaceae, nonfermentative gram-negative bacilli, Staphylococcus aureus, Streptococcus pneumoniae, and Enterococcus faecium--all considered highly resistant, according to Dutch guidelines--were included. Epidemiological linkage and nosocomial transmission were determined on the basis of molecular typing and hospital admission data.

RESULTS

From 119 patients, we recovered a total of 170 unique HRO isolates, as follows: Escherichia coli, 96 isolates; Klebsiella species, 11 isolates; Enterobacter species, 8 isolates; Proteus species, 9 isolates; Citrobacter species, 5 isolates; Pseudomonas species, 5 isolates; Acinetobacter species, 3 isolates; Morganella species, 2 isolates; Salmonella species, 1 isolate; Serratia species, 1 isolate; S. pneumoniae, 20 isolates; and S. aureus, 9 isolates. No vancomycin-resistant E. faecium was found. The incidence density was 4.3 HRO isolates per 10,000 patient-days. The majority of HRO isolates were unique, and nosocomial transmission was observed 4 times for highly resistant gram-negative bacilli (case reproduction rate, 0.05) and 4 times for penicillin-nonsusceptible S. pneumoniae (case reproduction rate, 0.29). A stay on the intensive care unit was the main determinant for the recovery of an HRO.

CONCLUSION

Nosocomial transmission of HROs was observed 8 times during the 18-month period. The intensive care unit was identified as the main reservoir of horizontal spread of HROs. This study shows that nosocomial transmission of HROs is largely preventable using transmission precautions.

Oral and parenteral therapeutic options for outpatient urinary infections caused by enterobacteriaceae producing CTX-M extended-spectrum beta-lactamases

Effective therapeutic options are needed for community-onset urinary tract infections due to Escherichia coli strains that produce CTX-M extended-spectrum beta-lactamases. We examined 46 urinary isolates producing CTX-M against several oral or long-acting parenteral antimicrobial agents. Approximately 90% were susceptible to fosfomycin and to a combination of cefdinir plus amoxicillin-clavulanate. All were susceptible to ertapenem.

Bad bugs, no drugs: no ESKAPE! An update from the Infectious Diseases Society of America

The Infectious Diseases Society of America (IDSA) continues to view with concern the lean pipeline for novel therapeutics to treat drug-resistant infections, especially those caused by gram-negative pathogens. Infections now occur that are resistant to all current antibacterial options. Although the IDSA is encouraged by the prospect of success for some agents currently in preclinical development, there is an urgent, immediate need for new agents with activity against these panresistant organisms. There is no evidence that this need will be met in the foreseeable future. Furthermore, we remain concerned that the infrastructure for discovering and developing new antibacterials continues to stagnate, thereby risking the future pipeline of antibacterial drugs. The IDSA proposed solutions in its 2004 policy report, "Bad Bugs, No Drugs: As Antibiotic R&D Stagnates, a Public Health Crisis Brews," and recently issued a "Call to Action" to provide an update on the scope of the problem and the proposed solutions. A primary objective of these periodic reports is to encourage a community and legislative response to establish greater financial parity between the antimicrobial development and the development of other drugs. Although recent actions of the Food and Drug Administration and the 110th US Congress present a glimmer of hope, significant uncertainly remains. Now, more than ever, it is essential to create a robust and sustainable antibacterial research and development infrastructure--one that can respond to current antibacterial resistance now and anticipate evolving resistance. This challenge requires that industry, academia, the National Institutes of Health, the Food and Drug Administration, the Centers for Disease Control and Prevention, the US Department of Defense, and the new Biomedical Advanced Research and Development Authority at the Department of Health and Human Services work productively together. This report provides an update on potentially effective antibacterial drugs in the late-stage development pipeline, in the hope of encouraging such collaborative action.

Incidence, risk factors and outcomes of Escherichia coli bloodstream infections in a large Canadian region

Although Escherichia coli is the most common cause of bloodstream infection, its epidemiology has not been well defined in non-selected populations. We sought to describe the incidence of risk factors for, and outcomes associated with, E. coli bacteraemia. Population-based surveillance for E. coli bacteraemia was conducted in the Calgary Health Region (population 1.2 million) during the period 2000-2006. In total, 2368 episodes of E. coli bacteraemia were identified for an overall annual population incidence of 30.3/100 000; 15% were nosocomial, 32% were healthcare-associated community-onset and 53% were community-acquired bacteraemias. The very young and the elderly were at highest risk for E. coli bacteraemia. Sixty per cent of the episodes occurred in females (relative risk 1.5; 95% CI 1.4-1.6). Dialysis, solid organ transplantation and neoplastic disease were the most important risk factors for acquiring E. coli bacteraemia. Rates of resistance to ampicillin, trimethoprim-sulphamethoxazole, gentamicin, ciprofloxacin, cefazolin and ceftriaxone increased significantly during the period 2000-2006. The case-fatality rate was 11% and the annual population mortality rate was 2.9/100 000. Increasing age, ciprofloxacin resistance, non-urinary focus and a number of comorbid illnesses were independently associated with an increased risk of death, and community acquisition and urinary focus were associated with a lower risk of death. This study documents the major burden of illness associated with E. coli bacteraemia and identifies groups at increased risk for acquiring and dying from these infections. The emergence of ciprofloxacin resistance and its adverse effect on patient outcome is a major concern.

Prolonged fecal shedding of CTX-M-15-producing Escherichia coli and recurrent sepsis in a patient after cord blood stem-cell transplantation

An extended-spectrum beta-lactamase (CTX-M-15 type)-producing Escherichia coli persisted in the intestinal tract for >5 months in a pediatric patient after cord blood stem-cell transplantation and caused 2 episodes of sepsis. The bla(CTX-M-15) is carried by a large plasmid of approximately 130 kb in size. The prolonged shedding of the highly resistant E. coli posed a great challenge to infection control and public health.

Antimicrobial resistance in zoonotic bacteria: lessons learned from host-specific pathogens

The relative contribution of veterinary and human clinical treatments to the selection of antimicrobial resistance in zoonotic pathogens remains controversial. In this review, we consider bacterial pathogens that differ in host specificity and address their resistance profiles: pathogens that only occur in the human host, pathogens that are specific to particular food-producing animals and pathogens that occur in both host types. Compared with those pathogens restricted to a single animal host, pathogens found in both human and animal hosts appear to have higher incidences of resistance. However, the most urgent and severe resistance problems occur with pathogens exclusively infecting humans. Differences exist in the available genetic repertoire of a bacterial species and these are reflected in the observed resistance patterns; it is important to note that different bacterial species do not automatically result in similarly resistant populations when they undergo comparable selection in different host species. Thus, within a bacterial species, prevalence of resistance can differ between populations isolated from different hosts. For some species, fluctuations in dominant subpopulations, for instance particular serotypes, can be the most important factor determining resistance. The frequently expressed opinion that veterinary use of antimicrobials is at the heart of many resistance problems may be an oversimplification of the complex forces at play.

Multiresistant Enterobacteriaceae: new threat of an old problem

The Enterobacteriaceae are among the most important causes of serious nosocomial and community-onset bacterial infections in humans, and resistance to antimicrobial agents in these species has become an increasingly relevant problem for healthcare providers. beta-lactam and fluoroquinolone antibiotics are important drug classes used to treat infections caused by Enterobacteriaceae. Emerging resistance mechanisms against these agents have recently been described in Enterobacteriaceae and include the production of newer beta-lactamases and plasmid-mediated quinolone resistance. The newer beta-lactamases consist of the following: plasmid-mediated AmpC beta-lactamases (e.g., ephamycin [CMY], CMY types), extended-spectrum beta-lactamases (e.g., cefotaxime [CTX], CTX-M first isolated at Munich) and carbapenem-hydrolyzing enzymes (e.g., Klebsiella pneumoniae carbapenemase [KPC], KPC types and the metallo-beta-lactamases). Recent developments in the epidemiology, clinical relevance and laboratory detection of infections caused by multiresistant Enterobacteriaceae with these new types of resistance mechanisms will be addressed in this review.

Capsular polysaccharide and the O-specific antigen impede antibody binding: a potential obstacle for the successful development of an extraintestinal pathogenic Escherichia coli vaccine

Extraintestinal pathogenic Escherichia coli (ExPEC) cause a wide variety of infections that are responsible for significant morbidity, mortality and costs to our healthcare system. An efficacious vaccine against ExPEC would be desirable. Previously, we demonstrated that nasal immunization with a genetically engineered strain in which capsule and O-antigen are no longer expressed (CP923) was immunogenic, generated antibodies that bound a subset of heterologous ExPEC strains, and enhanced neutrophil-mediated bactericidal activity against the homologous and a heterologous strain in vitro. In the work reported here we tested the hypothesis that nasal immunization with CP923 conferred protection in a mouse intravenous sepsis model. Nasal immunization with the wild-type strain CP9 conferred protection against challenge with itself and this protection was enhanced when IL-12 was used as an adjuvant. However, when CP923 was used the immunogen, protection was not observed against challenge with CP9. Next, we hypothesized that the observed lack of protection may be due to capsule and the O-antigen moiety of lipopolysaccharide (LPS) impeding antibody binding to non-capsule and O-antigen epitopes. This hypothesis was substantiated by in vitro binding assays, which demonstrated that binding of polyclonal anti-CP923 antisera was decreased when capsule and/or O-antigen were present. Lastly, neutrophil-mediated bactericidal activity against CP923, opsonisized with anti-CP923 antisera, was significantly increased compared to CP9. Taken together, these results demonstrate that the capsule and O-antigen form a biologically significant barrier against antibodies directed against non-capsular and O-antigen epitopes. This defense against the acquired immune response will need to be overcome for the development of a successful vaccine against ExPEC.

Susceptibilities of common bacterial isolates from oman to old and new antibiotics

OBJECTIVES

The purpose of this study is to compare the antimicrobial activity of linezolid and tigecycline with other commonly used antibiotics against a variety of clinical isolates at Royal Hospital, Muscat.

METHODS

Clinically-significant bacterial isolates in Royal hospital during the period from 1st of March to 30th of June 2007 were collected, stored and finally tested to determine their susceptibility to different antibiotics by broth microdilution (microscan panels).

RESULTS

Two hundred ten bacterial strains were collected and tested including Staphylococcus aureus (29), Group B ß-haemolytic Streptococcus (10), Streptococcus pneumoniae (15), Enterococcus spp. (16), Haemophilus spp. (15), Escherichia coli (26), Klebsiella spp. (26), Enterobacter spp. (25), Serratia spp. (10), Acinetobacter baumannii (17) and Pseudomonas aeruginosa (21). All strains except P. aeuginosa were susceptible to tigecycline. All gram-positive strains were susceptible to linezolid. Meropenem and piperacillin-tazobactam showed good activity against most organisms tested including P. aeruginosa and Acinetobacter baumannii. Levofloxacin showed 100% activity against K. pneumoniae and 61% activity against E. coli. The activity of 3rd generation cephalosporins against E.coli and K.pneumoniae ranged from 76% to 100%.

CONCLUSION

Tigecycline and linezolid showed excellent activity against microorganisms in their relevant spectrum of activity. However, they should be used wisely and judiciously.

Bloodstream infections caused by extended-spectrum-beta-lactamase- producing Escherichia coli: risk factors for inadequate initial antimicrobial therapy

Extended-spectrum-beta-lactamase (ESBL)-producing strains of Escherichia coli are a significant cause of bloodstream infections (BSI) in hospitalized and nonhospitalized patients. We previously showed that delaying effective antimicrobial therapy in BSI caused by ESBL producers significantly increases mortality. The aim of this retrospective 7-year analysis was to identify risk factors for inadequate initial antimicrobial therapy (IIAT) (i.e., empirical treatment based on a drug to which the isolate had displayed in vitro resistance) for inpatients with BSI caused by ESBL-producing E. coli. Of the 129 patients considered, 56 (43.4%) received IIAT for 48 to 120 h (mean, 72 h). Independent risk factors for IIAT include an unknown BSI source (odds ratios [OR], 4.86; 95% confidence interval [CI], 1.98 to 11.91; P = 0.001), isolate coresistance to >or=3 antimicrobials (OR, 3.73; 95% CI, 1.58 to 8.83; P = 0.003), hospitalization during the 12 months preceding BSI onset (OR, 3.33; 95% CI, 1.42 to 7.79; P = 0.005), and antimicrobial therapy during the 3 months preceding BSI onset (OR, 2.65; 95% CI, 1.11 to 6.29; P = 0.02). IIAT was the strongest risk factor for 21-day mortality and significantly increased the length of hospitalization after BSI onset. Our results underscore the need for a systematic approach to the management of patients with serious infections by ESBL-producing E. coli. Such an approach should be based on sound, updated knowledge of local infectious-disease epidemiology, detailed analysis of the patient's history with emphasis on recent contact with the health care system, and aggressive attempts to identify the infectious focus that has given rise to the BSI.