Risk factors for and outcomes of bloodstream infection caused by extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella species in children

The epidemiology, pathogenesis and treatment of Pseudomonas aeruginosa infections

Pseudomonas aeruginosa is an important bacterial pathogen, particularly as a cause of infections in hospitalised patients, immunocompromised hosts and patients with cystic fibrosis. Surveillance of nosocomial P. aeruginosa infections has revealed trends of increasing antimicrobial resistance, including carbapenem resistance and multidrug resistance. Mechanisms of antimicrobial resistance include multidrug efflux pumps, ss-lactamases and downregulation of outer membrane porins. Mechanisms of virulence include secreted toxins and the ability to form biofilms. The effective treatment of infections caused by P. aeruginosa includes prevention when possible, source control measures as necessary and prompt administration of appropriate antibacterial agents. Antibacterial de-escalation should be pursued in patients with an appropriate clinical response, especially when antibacterial susceptibilities are known. Multidrug-resistant P. aeruginosa may require treatment with less commonly used antibacterials (e.g. colistin), but newer anti-pseudomonal antibacterials are expected to be available in the near future.

Clinical variables associated with the isolation of Klebsiella pneumoniae expressing different extended-spectrum beta-lactamases

Clinical variables associated with the isolation of Klebsiella pneumoniae expressing different extended-spectrum beta-lactamases (ESBLs) were studied. Clinical records of patients with ESBL-positive K. pneumoniae isolates between 1989 and 2003 (n = 80) were reviewed retrospectively. Patients with SHV- and TEM-type ESBLs were identified more frequently in the intensive care units (67% and 78%, respectively), whereas those with CTX-M ESBLs were found in medical wards (52.2%) or were outpatients (17.4%) (p <0.01). The absence of urinary or central catheters was associated with CTX-M-10 (p 0.013 and p <0.01, respectively). Central catheter-related infections and secondary bacteraemia were associated more frequently with SHV- and TEM-type ESBLs, whereas urinary tract infections were associated with CTX-M-10. Previous aminoglycoside use was associated particularly with SHV-type ESBLs (p <0.01), whereas amoxycillin-clavulanate and oral cephalosporins were associated with CTX-M-10 (p <0.01 and p 0.050, respectively). The frequency of adequate empirical treatment was low (22%), and 61% of patients were treated according to the susceptibility testing results. Mortality (22%) and related mortality (14%) did not differ statistically according to the type of ESBL. Different ESBL types in K. pneumoniae were associated with different clinical variables, and this should be taken into account in current and future epidemiological scenarios.

Comparative effects of single-dose ceftriaxone versus three oral antibiotic regimens on stool colonization by resistant bacilli in children

OBJECTIVE

The use of short-term intramuscular ceftriaxone for pediatric ambulatory conditions raises concerns regarding the promotion of resistance among colonizing enteric bacteria. This study was designed to assess the prevalence of stool colonization with resistant Gram-negative bacilli after single-dose ceftriaxone treatment compared with other regimens for acute otitis media.

METHODS

Children age 3 months to 7 years and diagnosed with acute otitis media were randomized to receive treatment with single-dose ceftriaxone or with oral cefprozil, amoxicillin or azithromycin. Stool samples were obtained at enrollment and then 3-5 days, 10-14 days, and 28-30 days after therapy was initiated and screened for the presence of facultative Gram-negative bacilli resistant to ceftriaxone, cefprozil, amoxicillin, piperacillin, piperacillin-tazobactam and tobramycin. Mean prevalence of colonization by resistant organisms for each treatment group was compared at each time point.

RESULTS

One thousand nine subjects were enrolled. The prevalence of colonization by a Gram-negative bacillus resistant to at least 1 of the screening antibiotics decreased after receipt of ceftriaxone but returned close to values measured at study entry by 30 days. A qualitatively similar pattern was noted for the 3 other regimens, but a quantitatively greater decrease in the prevalence of colonization by a resistant bacterium was noted at the 3- to 5-day and 10- to 14-day visits among azithromycin recipients (P < 0.001). Colonization by a Gram-negative bacillus resistant specifically to ceftriaxone was unusual at each study visit, regardless of treatment assignment.

CONCLUSIONS

A single intramuscular dose of ceftriaxone had a similar effect on the prevalence of antibiotic-resistant Gram-negative facultative bacilli in the stool of healthy children when compared with commonly used oral agents.

Outbreak of CTX-M-3-type extended-spectrum β-lactamase-producing Enterobacter cloacae in a pediatric ward

A first resistant strain of Enterobacter cloacae was isolated from a blood specimen in a pediatric patient with immature teratoma-developed sepsis after combination chemotherapy. The strain produced extended-spectrum beta-lactamase (ESBL), and the same ESBL-producing strains were detected in urine samples from other patients in the pediatric ward. All strains harbored genes for bla (CTX-M-3) by polymerase chain reaction (PCR) and sequencing analysis. Analysis of pulsed-field gel electrophoresis revealed that all strains were the same clonal type. These results suggest that ESBL-producing strains might be transmitted in the ward via contact among patients or medical staff.

Investigating the association between antibiotic use and antibiotic resistance: impact of different methods of categorising prior antibiotic use

Many studies have explored the association between antibiotic use and antibiotic resistance. However, methods employed in these studies to categorise prior antibiotic use (e.g. by class, by spectrum) have not been well described. The impact of using different categorisation methods on identifying risk factors for resistance is unknown. To explore these issues, we focused on extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella spp. (ESBL-EK) as a model. First, we conducted a systematic review of studies of risk factors for ESBL-EK to characterise past approaches to categorising antibiotic use. Second, we re-analysed data from a prior study of risk factors for ESBL-EK. Two separate multivariate models of risk factors for ESBL-EK were constructed: one with prior antibiotic use categorised by class and the other with prior antibiotic use categorised by spectrum of activity. Among the 20 articles that met the inclusion criteria for the systematic review, there was tremendous variability in how prior antibiotic use was categorised (e.g. by agent, class, spectrum and/or a combination of these). No study justified its choice of categorisation method. In the re-analysis of the existing data set, multivariate models of risk factors for ESBL-EK using 'class' and 'spectrum' categorisations differed substantially. In conclusion, there has been no consistent approach to categorising antibiotic use in studies of risk factors for ESBL-EK. Different categorisation schemes were shown to have a substantial impact on study results, particularly for the antibiotic exposures associated with resistance. Elucidating these issues is critical if effective strategies to curb resistance are to be designed.

The intensive care unit as a research laboratory: developing strategies to prevent antimicrobial resistance

OBJECTIVE

To assemble the available clinical data on the prevention of antimicrobial resistance in the intensive care unit (ICU) setting.

DATA SOURCE

A MEDLINE database search and references from identified articles were employed to obtain the literature relating to the prevention of antimicrobial resistance in the ICU.

CONCLUSIONS

The ICU presents a unique environment for the conduct of clinical research. The closed physical space with centralized patient management and efficient data recovery allows important clinical questions to be evaluated in a timely manner. Antimicrobial resistance has emerged as an important determinant of mortality for patients in the ICU. Additionally, there is currently a limited pipeline of new agents for the treatment of emerging bacteria with new resistance genes that pose an increasing threat to the ICU patient. Effective strategies for the prevention of antimicrobial resistance within ICUs are available and should be implemented aggressively. These strategies can be divided into non-pharmacologic infection- control strategies (e.g., routine hand hygiene, infection-specific prevention protocols) and antibiotic management strategies (e.g., shorter courses of appropriate antibiotics, narrowing of the antimicrobial spectrum on the basis of culture results). Additional studies conducted in ICUs are needed urgently to identify the optimal approaches for the management of antibiotics in order to balance the need for efficacy with the ability to minimize resistance.

Outcomes evaluation of patients with ESBL- and non–ESBL-producing Escherichia coli and Klebsiella species as defined by CLSI reference methods: report from the SENTRY Antimicrobial Surveillance Program

As extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae continue to emerge worldwide, selection of empiric treatment modalities is an increasing challenge. Data describing the clinical outcomes associated with different treatment regimens have been limited. Using data from centers with confirmed ESBL- and non-ESBL-producing Escherichia coli and Klebsiella species isolates in North America, Latin America, and Europe, potential risk factors for the occurrence of invasive ESBL- and non-ESBL-producing Enterobacteriaceae infections and factors associated with clinical outcome were evaluated. Of the 175 cases considered evaluable, 77% were ESBL-producing organisms. Underlying comorbidities and potential risk factors were generally similar between ESBL and non-ESBL cases with a statistically greater proportion of ESBL cases requiring gastrostomy or jejunostomy tubes, ventilatory assistance, or care in the intensive care unit before culture (P<or=0.008). Among ESBL cases, carbapenem monotherapy and combination therapy were often selected for treatment (32.6% and 13.3%, respectively). Among non-ESBL cases, fluoroquinolones and beta-lactam/beta-lactamase inhibitor combination agents accounted for the highest proportion of treatment regimens (25.0% and 22.5%, respectively), whereas cephalosporin monotherapy and combination therapy were each used as treatment for 10% of cases. Clinical success was similar between patients with ESBL and non-ESBL-producing isolates (83% and 80%, respectively). Although infections arising from E. coli and Klebsiella species are associated with significant mortality, ESBL production alone did not appear to be an independent risk factor for treatment failure.