Clinical impact of pharmacist-directed antimicrobial stewardship guidance following blood culture rapid diagnostic testing

BACKGROUND

Rapid diagnostic testing (RDT) has been shown to be associated with improved clinical outcomes.

AIM

To evaluate the clinical outcomes of using RDT paired with well-defined pharmacist-directed antimicrobial stewardship programme (ASP) guidance to achieve targeted treatment in patients with bacteraemia.

METHODS

In this quasi-study, a retrospective (pre-intervention) phase was compared with a prospective (post-intervention) phase. Adult patients with positive blood cultures identified using the BacT/ALERT system were included. Bacterial identification and susceptibility were provided by VITEK 2. During the post-intervention phase, Verigene ASP guidance was developed to optimize antibiotic selection. Pharmacists received the results from the microbiology laboratory, evaluated the appropriateness of current therapy (if any), and communicated the recommended antimicrobial therapy to the treating physician accordingly.

FINDINGS

The cohort consisted of 164 patients in the pre-intervention group and 148 patients in the post-intervention group. When comparing the post-intervention period with the pre-intervention period, the median time to culture identification was 22 vs 96 h (P<0.0001), median time to targeted antibiotics was 2 vs 22 h (P<0.0001), median time for antibiotic de-escalation was 12.2 vs 27 h (P<0.0001), and median time to escalation was 1.3 vs 24 h (P<0.003), respectively. In-hospital mortality and 30-day re-admission were significantly lower in the post-intervention group (P<0.003 and 0.034, respectively). Length of hospital stay was significantly shorter in the post-intervention group (6.5 vs 8 days; P=0.03).

CONCLUSION

Rapid identification of bacteraemia combined with a pharmacist's recommendation as an ASP initiative significantly improved time to optimal therapy, and may have decreased the risk of mortality and re-admission.

Role of the Clinical Microbiology Laboratory in Antimicrobial Stewardship

For adequate antimicrobial stewardship, microbiology needs to move from the laboratory to become physically and verbally amenable to the caregivers of an institution. Herein, we describe the contributions of our microbiology department to the antimicrobial stewardship program of a large teaching hospital as 10 main points ranging from the selection of patients deemed likely to benefit from a fast track approach, to their clinical samples, or the rapid reporting of results via a microbiology hotline, to rapid searches for pathogens and susceptibility testing. These points should serve as guidelines for similar programs designed to decrease the unnecessary use of antimicrobials.

Real-world performance of a microarray-based rapid diagnostic for Gram-positive bloodstream infections and potential utility for antimicrobial stewardship

The Verigene Gram-positive blood culture assay (BC-GP) is a microarray-based rapid diagnostic test, which includes targets for 12 bacterial species and 3 resistance determinants. We prospectively compared the diagnostic accuracy of the BC-GP to routine microbiologic methods and evaluated the potential of the BC-GP for antimicrobial stewardship programs. A total of 143 consecutive patients with Gram-positive bacteremia were included in the analysis. BC-GP correctly identified 127/128 (99.2%) of organisms from monomicrobial blood cultures and 9/14 (64.3%) from polymicrobial, including all methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. Stewardship interventions were possible in 51.0% of patients, most commonly stopping or preventing unnecessary vancomycin or starting a targeted therapy. In Monte Carlo simulations, unnecessary antibiotics could be stopped at least 24 hours earlier in 65.6% of cases, and targeted therapy could be started at least 24 hours earlier in 81.2%. BC-GP is a potentially useful test for antibiotic stewardship in patients with Gram-positive bacteremia.

Importance of antimicrobial stewardship to the English National Health Service

Antimicrobials are an extremely valuable resource across the spectrum of modern medicine. Their development has been associated with dramatic reductions in communicable disease mortality and has facilitated technological advances in cancer therapy, transplantation, and surgery. However, this resource is threatened by the dwindling supply of new antimicrobials and the global increase in antimicrobial resistance. There is an urgent need for antimicrobial stewardship (AMS) to protect our remaining antimicrobials for future generations. AMS emphasizes sensible, appropriate antimicrobial management for the benefit of the individual and society as a whole. Within the English National Health Service (NHS), a series of recent policy initiatives have focused on all aspects of AMS, including best practice guidelines for antimicrobial prescribing, enhanced surveillance mechanisms for monitoring antimicrobial use across primary and secondary care, and new prescribing competencies for doctors in training. Here we provide a concise summary to clarify the current position and importance of AMS within the NHS and review the evidence base for AMS recommendations. The evidence supports the impact of AMS strategies on modifying prescribing practice in hospitals, with beneficial effects on both antimicrobial resistance and the incidence of Clostridium difficile, and no evidence of increased sepsis-related mortality. There is also a promising role for novel diagnostic technologies in AMS, both in enhancing microbiological diagnosis and improving the specificity of sepsis diagnosis. More work is needed to establish an evidence base for interventions to improve public and patient education regarding the role of antibiotics in common clinical syndromes, such as respiratory tract infection. Future priorities include establishing novel approaches to antimicrobial management (eg, duration of therapy, combination regimens) to protect against resistance and working with the pharmaceutical industry to promote the development of new antimicrobials.

Evaluation and use of a rapid Staphylococcus aureus assay by an antimicrobial stewardship program

PURPOSE

The performance of a rapid test for methicillin-resistant Staphylococcus aureus (MRSA) in a large community hospital was investigated.

METHODS

A prospective observational study was conducted to evaluate an immunochromatographic assay (Alere PBP2a Culture Colony Test, Alere Scarborough, Inc.) for rapid differentiation of MRSA and methicillin-susceptible S. aureus (MSSA) strains using isolates cultured overnight on common laboratory media. S. aureus isolates cultured for 12-24 hours were tested with the assay, which detects penicillin-binding protein 2a (PBP2a) and provides results in six minutes. The test results were compared with data from standard overnight antimicrobial susceptibility testing to determine the assay's sensitivity and specificity. Changes in therapy associated with use of the rapid assay were evaluated.

RESULTS

Over an 11-month period, 661 inpatient isolates from mostly nonhematologic sites were tested. There were six false-negative results, indicating assay sensitivity of 98.4%, with no false positives (specificity of 100%). Eight invalid test results were documented. During designated evaluation periods, a total of 169 patient cases involving PBP2a testing were reviewed by the hospital's antimicrobial stewardship pharmacist. In 63 of those cases (37%), changes in therapy were implemented on the day of test result posting. Interventions often involved switching patients from inappropriate to appropriate MRSA therapy or optimizing MRSA- or MSSA-targeted therapy.

CONCLUSION

An assay for quickly differentiating between MRSA and MSSA was highly sensitive, highly specific, and inexpensive in actual hospital use and led to rapid prescription of appropriate antistaphylococcal therapy 24-48 hours after culture specimens were collected.

Clinical outcomes with rapid detection of methicillin-resistant and methicillin-susceptible Staphylococcus aureus isolates from routine blood cultures

Staphylococcus aureus is a common cause of bacteremia, with a substantial impact on morbidity and mortality. Because of increasing rates of methicillin-resistant Staphylococcus aureus, vancomycin has become the standard empirical therapy. However, beta-lactam antibiotics remain the best treatment choice for methicillin-susceptible strains. Placing patients quickly on the optimal therapy is one goal of antimicrobial stewardship. This retrospective, observational, single-center study compared 33 control patients utilizing only traditional full-susceptibility methodology to 22 case patients utilizing rapid methodology with CHROMagar medium to detect and differentiate methicillin-resistant and methicillin-susceptible Staphylococcus aureus strains hours before full susceptibilities were reported. The time to targeted therapy was statistically significantly different between control patients (mean, 56.5 ± 13.6 h) and case patients (44.3 ± 17.9 h) (P = 0.006). Intensive care unit status, time of day results emerged, and patient age did not make a difference in time to targeted therapy, either singly or in combination. Neither length of stay (P = 0.61) nor survival (P = 1.0) was statistically significantly different. Rapid testing yielded a significant result, with a difference of 12.2 h to targeted therapy. However, there is still room for improvement, as the difference in time to susceptibility test result between the full traditional methodology and CHROMagar was even larger (26.5 h). This study supports the hypothesis that rapid testing plays a role in antimicrobial stewardship by getting patients on targeted therapy faster.