Evaluating the usefulness of the estimated glomerular filtration rate for determination of imipenem dosage in critically ill patients.

BACKGROUND: Antibiotic dosing in critically ill patients is complicated by variations in the pharmacokinetics of antibiotics in this group. The dosing of imipenem/cilastatin is usually determined by severity of illness and renal function. OBJECTIVES: To determine the correlation between estimated glomerular filtration rates (eGFRs) calculated with the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and imipenem trough levels in critically ill patients. METHODS: This prospective observational study was done in the surgical intensive care unit (ICU) at Steve Biko Academic Hospital, Pretoria, South Africa. Imipenem trough levels were measured by high-performance liquid chromatography and compared with eGFRs calculated with the CKD-EPI equation. Correlation was evaluated by the Pearson product-moment correlation coefficient. RESULTS: The study population consisted of 68 critically ill patients aged between 18 and 81 years; 43 (63%) were male, and the mean weight was 78 kg (range 40 - 140). On admission, 30 patients (44%) had sepsis, 16 (24%) were admitted for trauma, and 22 (32%) were admitted for miscellaneous surgical conditions. Acute Physiology and Chronic Health Evaluation II (APACHE II) scores ranged from 4 to 39 (mean 18). The 28-day mortality rate was 29%. The mean albumin level was 16 g/L (range 7 - 25), the mean creatinine level 142 µmol/L (range 33 - 840), and the mean eGFR 91 mL/min/1.73 m2 (range 6 - 180). Imipenem trough levels ranged between 3.6 and 92.2 mg/L (mean 11.5). The unadjusted Pearson product-moment correlation coefficient between eGFR and imipenem trough level was -0.04 (p=0.761). CONCLUSION: Considering the high mortality rate of sepsis in ICUs and the rapid global increase in antimicrobial resistance, it is crucial to dose antibiotics appropriately. Owing to the variability of antibiotic pharmacokinetics in critically ill patients, this task becomes almost impossible when relying on conventional dosing guidelines. This study found that eGFRs do not correlate with imipenem blood levels in critically ill patients and should not be used to determine the dose of imipenem/cilastatin. Instead, the dose should be individualised for patients through routine therapeutic drug monitoring.

Investigating the need for therapeutic drug monitoring of imipenem in critically ill patients: Are we getting it right?

BACKGROUND: The drug levels and clearances of imipenem in critically ill patients are not comprehensively described in current literature, yet it is vital that adequate levels be achieved for therapeutic success. OBJECTIVES: To determine the proportion of critically ill patients treated with imipenem/cilastatin with sub-therapeutic imipenem plasma levels, and to compare the clinical outcomes of those patients with therapeutic levels with those who had sub-therapeutic levels. METHODS: Trough imipenem plasma levels of 68 critically ill patients from a surgical intensive care unit were measured using a validated high-performance liquid chromatography method. Imipenem trough levels were compared with the minimum inhibitory concentration (MIC) of the causative bacterial agents, based on a target value of 100% time above MIC (¦T >MIC). RESULTS: The proportion of participants with sub-therapeutic imipenem levels was 22% (95% confidence interval (CI) 13% - 34%). The 14- and 28-day mortality rates in the sub-therapeutic group were 33% and 40%, respectively, compared with 19% (p=0.293) and 26% (p=0.346), respectively, in the therapeutic group. Sub-therapeutic imipenem plasma levels are associated with adjusted hazard ratio of 1.47 (95% CI 0.55 - 3.91). CONCLUSIONS: The lower proportion of critically ill patients with sub-therapeutic imipenem plasma levels in this study compared with previous studies may be attributed to the practice of higher dosages and the administration method of extended infusions of imipenem/cilastatin in our setting. The results demonstrate a trend of higher mortality in patients with sub-therapeutic imipenem levels, although the results were not statistically significant at this sample size.

Evaluation of an In-House Colistin NP Test for Use in Resource-Limited Settings.

Colistin has become increasingly important in the treatment of multidrug-resistant Gram-negative bacteria. Resistance to colistin has emerged globally, necessitating the need for an accurate method to detect colistin resistance. The colistin NP test has shown promise as a rapid screening assay for colistin resistance. This study compared the performance of an in-house-prepared colistin NP test against broth microdilution (BMD) as the gold standard and against Etest (bioMérieux, Marcy l'Etoile, France) as an alternative method. A total of 215 stored Enterobacteriaceae isolates were evaluated, of which 159 were resistant and 56 susceptible to colistin by BMD. The categorical agreement of the colistin NP test with BMD was found to be 98.1%, compared to 87.9% for the Etest. One major error was detected with both the colistin NP test and the Etest. Three very major errors were detected with the colistin NP test compared to 25 with the Etest. This resulted in a major error rate of 1.8% for both the colistin NP test and the Etest and a very major error rate of 1.9% and 15.7% for the colistin NP test and the Etest, respectively. The colistin NP test compared satisfactorily to the BMD reference method in determining colistin susceptibility. The colistin NP test is a rapid, inexpensive screening method for colistin resistance, especially in resource-limited settings.

Small molecule inhibition of cAMP response element binding protein in human acute myeloid leukemia cells.

The transcription factor CREB (cAMP Response-Element Binding Protein) is overexpressed in the majority of acute myeloid leukemia (AML) patients, and this is associated with a worse prognosis. Previous work revealed that CREB overexpression augmented AML cell growth, while CREB knockdown disrupted key AML cell functions in vitro. In contrast, CREB knockdown had no effect on long-term hematopoietic stem cell activity in mouse transduction/transplantation assays. Together, these studies position CREB as a promising drug target for AML. To test this concept, a small molecule inhibitor of CREB, XX-650-23, was developed. This molecule blocks a critical interaction between CREB and its required co-activator CBP (CREB Binding Protein), leading to disruption of CREB-driven gene expression. Inhibition of CBP-CREB interaction induced apoptosis and cell-cycle arrest in AML cells, and prolonged survival in vivo in mice injected with human AML cells. XX-650-23 had little toxicity on normal human hematopoietic cells and tissues in mice. To understand the mechanism of XX-650-23, we performed RNA-seq, ChIP-seq and Cytometry Time of Flight with human AML cells. Our results demonstrate that small molecule inhibition of CBP-CREB interaction mostly affects apoptotic, cell-cycle and survival pathways, which may represent a novel approach for AML therapy.

Replication factor C3 is a CREB target gene that regulates cell cycle progression through the modulation of chromatin loading of PCNA.

CREB (cyclic AMP response element-binding protein) is a transcription factor overexpressed in normal and neoplastic myelopoiesis and regulates cell cycle progression, although its oncogenic mechanism has not been well characterized. Replication factor C3 (RFC3) is required for chromatin loading of proliferating cell nuclear antigen (PCNA) which is a sliding clamp platform for recruiting numerous proteins in the DNA metabolism. CREB1 expression, which was activated by E2F, was coupled with RFC3 expression during the G1/S progression in the KG-1 acute myeloid leukemia (AML) cell line. There was also a direct correlation between the expression of RFC3 and CREB1 in human AML cell lines as well as in the AML cells from the patients. CREB interacted directly with the CRE site in RFC3 promoter region. CREB-knockdown inhibited primarily G1/S cell cycle transition by decreasing the expression of RFC3 as well as PCNA loading onto the chromatin. Exogenous expression of RFC3 was sufficient to rescue the impaired G1/S progression and PCNA chromatin loading caused by CREB knockdown. These studies suggest that RFC3 may have a role in neoplastic myelopoiesis by promoting the G1/S progression and its expression is regulated by CREB.

The use and maintenance of visible light activating units in general practice.

AIM: The present study to investigate the use, care and maintenance of light units in everyday clinical practice was undertaken to complement light unit emission surveys, with a view to developing a protocol for light unit use and care in everyday clinical practice. METHOD: The investigative work comprised a survey of selected practices in the Blackburn area with follow-up practice visits to examine light units in situ, and to glean additional information in respect of light unit use and care in the practice environment. RESULTS: Completed questionnaires were returned by 54 of 77 selected practices--a 70% response, including information in relation to 164 light units. Subsequently, 100 (61%) of these light units were examined in 42 practices according to a standardised protocol. The use and care of the light units included in the study was found to be very variable. In addition to finding that 28 (28%) had inadequate light output (<300 mW/cm2), many of the light units were found to be damaged or repaired (47, 47%). Thirty five (35%) of the light units inspected were found to have varying amounts of material adherent to the light guide exit portal. CONCLUSION: It is concluded that practitioners should address practical aspects of their increasing reliance on light units, and to this end, guidance is offered on visible light curing and the care and maintenance of light units.

An investigation by dielectric methods of hydration in myoglobin solutions.

The permittivities of three solutions of sperm-whale myoglobin of different concentrations were measured in the frequency range 300-1300MHz at 20 degrees C by using a coaxial-line technique. These results were combined with those measured previously at frequencies below 10MHz. Two methods are described for calculating the extent of macromolecular hydration from the data. The more reliable method yields results of approx. 0.25g of H(2)O/g of protein, which is in satisfactory agreement with the theoretically calculated value. Agreement with the value found from the rotational motion of the molecule is not so close, which is probably caused by the different meanings that may be ascribed to the term hydration.