Rapid identification of Staphylococcus aureus and methicillin resistance by flow cytometry using a peptide nucleic acid probe.

A total of 56 Staphylococcus aureus isolates incubated for 2 h in the presence or absence of oxacillin were analyzed by flow cytometry after labeling with an S. aureus-specific peptide nucleic acid (PNA) probe. Two defined ratios, the paired signal count ratio (PSCR) and the gate signal count ratio (GSCR), differentiated methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) with sensitivities of 100% each and specificities of 96% and 100%, respectively.

Rapid differentiation of methicillin-resistant and methicillin-susceptible Staphylococcus aureus by flow cytometry after brief antibiotic exposure.

We noticed that methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) isolates yielded side-scatter (SSC) and fluorescence intensity (FI) differences on flow cytometry (FCM) following incubation in oxacillin broth. The purpose of this study was to determine whether MRSA and MSSA could be reliably differentiated by FCM. S. aureus isolates were incubated in oxacillin-containing Mueller-Hinton broth, stained using the FASTEST total viable organisms kit, and analyzed by FCM in the MicroPRO instrument. SSC versus FI were examined, and gates 1 and 2 were defined to encompass the majority of MSSA and MRSA signal events, respectively. A count ratio (CR) was defined as the ratio of counts in gate 2 to those in gate 1. Initially, 33 isolates were tested after 4 h of incubation for proof-of-concept. Twenty others were then tested after incubation intervals ranging from 30 min to 4 h to determine the earliest possible time for differentiation. Next, 100 separate isolates were tested to determine the best CR cutoff value. Finally, the CR was validated by using an independent cohort of 121 isolates. We noted that MRSA isolates had higher SSC and FI readings than did MSSA isolates after 2 h of incubation. The receiver-operator characteristics curve showed that a CR cutoff of 0.0445 reliably differentiated MRSA from MSSA. In the validation cohort, this cutoff had a sensitivity of 100% and a specificity of 98.7% for identifying MRSA from among S. aureus isolates, following 2 h of incubation. This study demonstrates that MRSA and MSSA can be accurately differentiated by FCM after 2 h of incubation in an oxacillin-containing liquid culture medium.

Hospital Readmissions in Patients With Carbapenem-Resistant Klebsiella pneumoniae.

BACKGROUND: Various transmission routes contribute to spread of carbapenem-resistant Klebsiella pneumoniae (CRKP) in hospitalized patients. Patients with readmissions during which CRKP is again isolated ("CRKP readmission") potentially contribute to transmission of CRKP. OBJECTIVE: To evaluate CRKP readmissions in the Consortium on Resistance against Carbapenems in K. pneumoniae (CRaCKLe). DESIGN: Cohort study from December 24, 2011, through July 1, 2013. SETTING: Multicenter consortium of acute care hospitals in the Great Lakes region. PATIENTS: All patients who were discharged alive during the study period were included. Each patient was included only once at the time of the first CRKP-positive culture. METHODS: All readmissions within 90 days of discharge from the index hospitalization during which CRKP was again found were analyzed. Risk factors for CRKP readmission were evaluated in multivariable models. RESULTS: Fifty-six (20%) of 287 patients who were discharged alive had a CRKP readmission. History of malignancy was associated with CRKP readmission (adjusted odds ratio [adjusted OR], 3.00 [95% CI, 1.32-6.65], P<.01). During the index hospitalization, 160 patients (56%) received antibiotic treatment against CRKP; the choice of regimen was associated with CRKP readmission (P=.02). Receipt of tigecycline-based therapy (adjusted OR, 5.13 [95% CI, 1.72-17.44], using aminoglycoside-based therapy as a reference in those treated with anti-CRKP antibiotics) was associated with CRKP readmission. CONCLUSION: Hospitalized patients with CRKP-specifically those with a history of malignancy-are at high risk of readmission with recurrent CRKP infection or colonization. Treatment during the index hospitalization with a tigecycline-based regimen increases this risk.

Determining the duration of therapy for patients with community-acquired pneumonia.

Emerging data, including results from two systematic reviews, suggest that with appropriate antimicrobial selection, community-acquired pneumonia (CAP) can be successfully treated in less than 7 days, rather than the 7-14 days frequently utilized. Shorter course therapy has the potential not only to improve efficacy, safety, and compliance, but also to minimize the evolution of resistance. Utilization of procalcitonin as a biomarker in CAP can appropriately influence the duration of therapy without affecting mortality and cure rates. CAP treatment duration can further be reduced successfully into the clinical setting with the assistance of an antibiotic stewardship team.

Contribution of infectious disease consultation toward the care of inpatients being considered for community-based parenteral anti-infective therapy.

BACKGROUND: In the acute care setting in a multidisciplinary healthcare environment, the contribution of infectious disease (ID) specialists to overall patient care is difficult to measure. This study attempts to quantify the contribution of ID specialists when consulted for an activity specific to ID practice, community-based parenteral anti-infective therapy (CoPAT). METHODS: In February 2010, an electronic form for requesting ID consultations was introduced in the computerized provider order entry (CPOE) system at the Cleveland Clinic. This allowed for easy identification of ID consultations for CoPAT. Hospital records for all patients with CoPAT consultation requests between February 11, 2010 and May 15, 2010 were reviewed for specific defined contributions in the domains of optimization of antimicrobial therapy, significant change in patient assessment, and additional medical care contribution. RESULTS: Over a 3-month period, there were 263 CoPAT consultation requests via CPOE, of which 172 were initial consultations and 91 reconsultations. Antimicrobial treatment was optimized in 84%, a significant change in patient assessment made in 52%, and additional medical care contribution provided in 71% of consultations. In 33% of consultations, there was contribution in all 3 domains. CoPAT was deemed not to be necessary in 27%. For patients requiring CoPAT, effective care transition from the inpatient to outpatient setting was assured at least 86% of the time. CONCLUSION: Infectious disease consultation before discharge on parenteral antibiotics adds value by contributing substantially to inpatient care, and providing antimicrobial stewardship and continuity of care at a critical patient care transition point.

Antimicrobial stewardship at transition of care from hospital to community.

Mandatory infectious disease consultation for parenteral antimicrobials at hospital discharge resulted in avoiding postdischarge parenteral antimicrobials in 28% of patients. No emergency department visit or rehospitalization within 30 days for these patients was a consequence of parenteral antimicrobial avoidance. Antimicrobial stewardship at transition of care is effective in reducing unnecessary antimicrobial use.

The first pandemic of the 21st century: a review of the 2009 pandemic variant influenza A (H1N1) virus.

Swine influenza was first described in the 1918 pandemic and made a resurgence in April 2009 in the form of a triple-reassortant influenza A virus, which is composed of a combination of human, swine, and Eurasian avian strains. As evidenced with previous influenza pandemics, young adults and children aged < 24 years are the population most affected. Definitive diagnosis has largely been limited by the inability of conventional influenza testing to distinguish among influenza A subtypes; however, the surge in pandemic cases clearly emerged at the end of the annual influenza season in the northern hemisphere. The pandemic variant influenza A (H1N1) strain is typically susceptible to oseltamivir and resistant to adamantanes, unlike the 2008 to 2009 seasonal influenza A (H1N1). However, 2 cases of oseltamivir-resistant pandemic-variant influenza A (H1N1) were reported in late August 2009. The full impact of the current pandemic is not yet clear, and further reassortment with the circulating seasonal influenza strains in the upcoming 2009 fall season could potentially lead to acquisition of widespread oseltamivir resistance. Vaccination will become paramount in importance for prevention and public health safety.

How long should we treat community-acquired pneumonia?

PURPOSE OF REVIEW: The studies reviewed in this article suggest that a shorter duration of antibiotic therapy is comparable to standard therapy in the treatment of community-acquired pneumonia and promotes reduction of adverse events, microbial resistance, cost, and improved patient compliance. RECENT FINDINGS: Community-acquired pneumonia has traditionally been treated with a 7-14-day course of antimicrobial therapy. Since there have been few well controlled trials regarding the optimal duration of therapy, however, there has been no consensus on length of therapy among different organizational guidelines. Several recent studies have demonstrated that shorter course antibiotic regimens are effective in the treatment of community-acquired pneumonia. SUMMARY: Short-course antibiotic therapy is equivalent to standard length of therapy for clinical cure and bacterial eradication. Minimization of drug exposure, however, reduces selection pressure for resistant strains, strengthens patient compliance, and potentially reduces adverse events such as Clostridium difficile infections.