Intereactions between doripenem and clavulanate ­ Application of minimal inhibitory concentration analysis and cytometry flow for bactericidal studies

Background: In view of the current low efficacy of bacterial infection treatment the common trend towards searching for antibiotic systems exhibiting synergistic action is well justified. Among carbapenem analogues a particularly interesting option is provided by combinations of clavulanic acid with meropenem, which have proven to be especially effective. Results: Determination of the minimal inhibitory concentration (MIC) along with the method based on flow cytometry constitutes an important tool in the identification of bacterial sensitivity to active substances. Within this study the inhibitory effect of doripenem, clavulanic acid and the doripenem-clavulanate acid system was analyzed in relation to such bacteria as Salmonella enteritidis, Salmonella typhimurium, Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, Clostridium butyricum and Clostridium pasteurianum, Acinetobacter baumannii, Enterobacter aerogenes. The lowest MIC, amounting to 0.03 µg/mL, was observed for the doripenem-clavulanate acid system in the case of E. coli ATCC 25922. In turn, the lowest MIC for doripenem applied alone was recorded for K. pneumoniae ATCC 31488, for which it was 0.1 µg/mL. The strain which proved to be most resistant both to doripenem and the doripenem-clavulanate acid system, was A. baumannii, with MIC of 32 µg/mL (clinical isolate) and 16 µg/mL (reference strain). Cytometric analysis for P. aeruginosa ATCC 27853 and S. aureus ATCC 25923 showed changes in cells following exposure to limiting concentrations of the active substance. Conclusions: Analysis of MIC supplies important information concerning microbial sensitivity to active substances, mainly in terms of limiting concentrations causing mortality or vitality of the tested species, which is essential when selecting appropriate antibiotic therapy.

Actividad comparativa in vitro de doripenem y otros carbapenemicos frente a pseudomonas aeruginosa aisladas en el laboratorio de microbiología del hospital Vargas de Caracas / Comparative in vitro activity of dorypenem and other carbapenems in pseudomonas aeruginosa isolates on Vargas Caracas Hospital´s Microbiology

Los ensayos de cuantificación de ARN plasmáticos de VIH-1 son importantes para el control de pacientes infectados, así como el monitoreo de la respuesta a la terapia antirretroviral. Por lo tanto, los ensayos comerciales empleados para este propósito deben presentar buena correlación entre si, para dar lugar al manejo terapéutico apropiado. El objetivo del estudio consistió en correlacionar los resultados obtenidos mediante el ensayo de amplificación de señal (bDNA) y PCR en tiempo real (RT-PCR), ambas casas comerciales aprobadas por la FDA y con diferente diana de detección del VIH-1. La validación se realizó con 180 muestras clínicas de pacientes referidos al INHRR. Los resultados fueron comparados con la subpoblación de linfocitos TCD4+ determinados mediante citometría de flujo. El análisis estadístico se realizó empleando el coeficiente de regresión lineal de Pearson (R2) y el valor de contraste de hipótesis con una significancia del 95 %, usando el programa SPSS Statistics v10.0. Se observó una buena correlación entre los ensayos (R2=0.961, p<0.05), siendo la RTPCR más sensible. Las diferencias cuantitativas de carga viral entre las técnicas ensayadas fue menor de 0.5 log10 copias/ml para el 89% de las muestras, y >1 log10 copias/ml solo en dos pacientes, no indicando necesariamente cambio terapéutico. Adicionalmente, se encontró una correlación inversa entre los linfocitos TCD4+ y carga viral del VIH-1 medida por bDNA (R2= 0.20, p<0.05) y RT-PCR (R2= 0.15, p<0.05). Los ensayos evaluados mostraron que ambas técnicas puedes ser empleadas indistintamente para el control de los pacientes VIH positivo.

The assay for quantification of plasma HIV-1 RNA are important for the control of patients infected, as well as the monitoring of the response to antiretroviral therapy. Therefore, the commercial assays used for this purpose must submit good correlation between to give place to the appropriate therapeutic management. In this study, we correlate the results obtained through the testing of signal amplification (bDNA) and real-time PCR (RT-PCR), two comercial technical approved by the FDA and with different targets of detection HIV-1. The validation was carried out with 180 clinical samples of patients referred to the INHRR. The results were compared with the subpopulation of lymphocytes TCD4+ determined by flow cytometry. The statistical analysis was performed using the program SPSS Statistics v10. It was observed good correlation between the tests studied (R2=0.961, p<0.05), with RT-PCR more sensitive. The quantitative differences in viral load between the techniques tested was less than 0.5 log10 copies/ml for the 89% of the samples, and >1 log10 copies/ml in only two patients. Additionally, it was found an inverse correlation between lymphocytes TCD4+ and viral load of HIV-1, measured by bDNA (R2= 0.20, p<0.05) and RT-PCR (R2= 0.15, p<0.05). Therefore, these assays can be employed for the patient control HIV.

In Vitro Interactions of Antibiotic Combinations of Colistin, Tigecycline, and Doripenem Against Extensively Drug-Resistant and Multidrug-Resistant Acinetobacter baumannii

BACKGROUND: Acinetobacter baumannii infections are difficult to treat owing to the emergence of various antibiotic resistant isolates. Because treatment options are limited for multidrug-resistant (MDR) A. baumannii infection, the discovery of new therapies, including combination therapy, is required. We evaluated the synergistic activity of colistin, doripenem, and tigecycline combinations against extensively drug-resistant (XDR) A. baumannii and MDR A. baumannii. METHODS: Time-kill assays were performed for 41 XDR and 28 MDR clinical isolates of A. baumannii by using colistin, doripenem, and tigecycline combinations. Concentrations representative of clinically achievable levels (colistin 2 microg/mL, doripenem 8 microg/mL) and achievable tissue levels (tigecycline 2 microg/mL) for each antibiotic were used in this study. RESULTS: The colistin-doripenem combination displayed the highest rate of synergy (53.6%) and bactericidal activity (75.4%) in 69 clinical isolates of A. baumannii. Among them, thedoripenem-tigecycline combination showed the lowest rate of synergy (14.5%) and bacteri-cidal activity (24.6%). The doripenem-tigecycline combination showed a higher antagonistic interaction (5.8%) compared with the colistin-tigecycline (1.4%) combination. No antagonism was observed for the colistin-doripenem combination. CONCLUSIONS: The colistin-doripenem combination is supported in vitro by the high rate of synergy and bactericidal activity and lack of antagonistic reaction in XDR and MDR A. baumannii. It seems to be necessary to perform synergy tests to determine the appropri-ate combination therapy considering the antagonistic reaction found in several isolates against the doripenem-tigecycline and colistin-tigecycline combinations. These findings should be further examined in clinical studies.

A meta-analysis of efficacy and safety of doripenem for treating bacterial infections

Objective: The aim of this article is to compare the efficacy and safety of doripenem for bacterial infections. Methods: We included six randomized clinical trials identified from PubMed and Embase up to July 31, 2014. The included trials compared efficacy and safety of doripenem for complicated intra-abdominal infections, complicated urinary tract infection, nosocomial pneumonia, and acute biliary tract infection. The meta-analysis was carried on by the statistical software of Review Manager, version 5.2. Results: Compared with empirical antimicrobial agents on overall treatment efficacy, doripenem was associated with similar clinical and microbiological treatment success rates (for the clinical evaluable population, odds ratio [OR] = 1.26, 95% confidence interval [CI] 0.93-1.69, p = 0.13; for clinical modified intent-to-treatment population, OR = 0.88, 95% CI 0.55-1.41, p = 0.60; for microbiology evaluable population, OR = 1.16, 95% CI 0.90-1.50, p = 0.26; for microbiological modified intent-to-treatment (m-mITT), OR = 0.98, 95% CI 0.81-1.20, p = 0.87). We compared incidence of adverse events and all-cause mortality to analyze treatment safety. The outcomes suggested that doripenem was similar to comparators in terms of incidence of adverse events and all-cause mortality on modified intent-to-treatment population (for incidence of AEs, OR = 1.10, 95% CI 0.90-1.35, p = 0.33; for all-cause mortality, OR = 1.08, 95% CI 0.77-1.51, p = 0.67). In nosocomial pneumonia and ventilator-associated pneumonia treatment, doripenem was not inferior to other antibacterial agents in terms of efficacy and safety. Conclusion: From this meta-analysis, we can conclude that doripenem is as valuable and well-tolerated than empirical antimicrobial agents for complicated intra-abdominal infections, complicated urinary tract infection, acute biliary tract infection and nosocomial pneumonia treatment. .

In vitro Antibacterial Activity of Doripenem against Gram-Negative Blood Isolates in a Korean Tertiary Care Center / 감염과화학요법

BACKGROUND: Doripenem is the most recently introduced antimicrobial agent of the carbapenem class. It is a valuable therapeutic option in the context of increasing antimicrobial resistance to imipenem and meropenem among gram-negative bacilli (GNB) clinical isolates. However, clinicians are usually reluctant to prescribe doripenem, because susceptibility to doripenem is not automatically reported by most clinical laboratories and the in vitro activity of doripenem against clinically significant GNB isolates remains uncertain. MATERIALS AND METHODS: We investigated the in vitro antibacterial activity of doripenem in GNB blood isolates in a tertiary care center. Over a period of 10 months, 212 adult bacteremia cases were treated at the study hospital. Doripenem susceptibility testing was performed for the 212 blood isolates by the disk diffusion method, and clinical data were collected. RESULTS: Among the blood isolates, the rate of doripenem resistance (7.5%) was lower than that of imipenem (12.9%) or other anti-GNB antimicrobial agents, except amikacin (2.1%). Almost all imipenem-susceptible GNB blood isolates (181/182, 99.5%) were susceptible to doripenem. Whereas doripenem resistance was rarely observed in Enterobacteriaceae (2/181, 1.1%), it was frequently observed in patients with non-fermentatative GNB (12/27, 44.4%), hospital-acquired infections (7/27, 25.9%), and pneumonia (11/49, 22.4%). CONCLUSION: Doripenem exhibited more potent in vitro activity against GNB blood isolates than other anti-GNB antimicrobial agents in a tertiary care center where it was infrequently prescribed compared with other carbapenems. However, its clinical utility may be limited due to the increasing number of carbapenem-resistant non-fermentative GNB infections.

Actividad in vitro de doripenem comparado con meropenem frente a aislamientos de Pseudomonas aeruginosa en un centro asistencial de tercer nivel de Bogotá (Colombia) / Activity of Doripenem compared to Meropenem against Pseudomonas aeruginosa isolates at Tertiary Care Teaching Hospital in Bogotá (Colombia)

Objetivo: El objetivo de este estudio fue evaluar la actividad in vitro de doripenem comparado con meropenem frente a aislamientos locales de Pseudomonas aeruginosa (P. aeruginosa) . Materiales y métodos: En el Hospital San José de Bogotá (Colombia), un hospital universitario de 300 camas, se recolectaron entre 2009 y 2011, 83 aislamientos no repetidos de P. aeruginosa , en los cuales se determinó la concentración inhibitoria mínima frente a meropenem y doripenem por el método de E-test. Se aplicaron los puntos de corte del Clinical and Laboratory Standars Institute para carbapenémicos vigentes para 2012 Resultados: La sensibilidad global de los aislamientos de P. aeruginosa a meropenem fue del 69% y a doripenem del 75%, siendo la concentración inhibitoria mínima 50 y 90 (µg/mL) de 0,75 y 28,8 para meropenem y de 0,64 y 15,2 para doripenem. Conclusiones: La concentración inhibitoria mínima frente a doripenem fue menor que la correspondiente a meropenem. Se requiere realizar en el ámbito local estudios de este tipo con el fin de llevar a cabo los ajustes a los protocolos de antibióticos institucionales.

objective: The aim of this study was to evaluate the in vitro activity of doripenem compared to meropemen against local isolates of Pseudomonas aeruginosa (P. aeruginosa) . Materials and methods: At the San José Hospital in Bogotá-Colombia, a 300-bed teaching hospital, 83 nonduplicate isolates of P. aeruginosa were collected between 2009 and 2011.Meropenem and Doripenem Minimum Inhibitory Concentration (MIC) were determined by the E test method. The 2012 Clinical and Laboratory Standards Institute breakpoints for carbapenems were applied. Results: The global susceptibility of P. aeruginosa isolates to meropemen was 69% and to doripenem was 75%, being the CIM 50 and 90 (ug/mL) of 0.75 and 28.8 for meropenem and of 0.64 and 15.2 for doripenem. Conclusions: The MIC of doripenem was lower than the corresponding MIC of meropenem. It is required to carry out local studies of this type in order to make adjustments to the institutional antibiotics protocol.

Doripenem vs meropenem against Pseudomonas and Acinetobacter.

Recently, doripenem has been approved for the treatment of nosocomial pneumonia (NP), including ventilator-associated pneumonia (VAP). The E-test was performed to determine the MICs of doripenem and meropenem in 203 endotracheal aspirate isolates that consisted of 140 Acinetobacter calcoaceticus-Acinetobacter baumannii complexes and 63 Pseudomonas aeruginosa. Doripenem showed minimum concentration necessary for inhibition of 50% (MIC 50 ) of P. aeruginosa isolates at 0.38 mg/L which is several times (84.2 times) lower than the corresponding MIC 50 value of >32 mg/L for meropenem. The MIC 50 and MIC 90 were similar for both the drugs against A. baumannii. Thus, P. aeruginosa was consistently more susceptible than the A. baumannii.

Actividad comparativa in vitro de doripenem y de otros carbapenemes frente a Pseudomonas aeruginosa / In vitro activity of doripenem and other carbapenems against Pseudomonas aeruginosa

Según estudios previos, el nuevo carbapeneme doripenem sería más activo frente a Pseudomonas aeruginosa en comparación con otros carbapenemes. En este estudio evaluamos la actividad in vitro del doripenem, el meropenem y el imipenem frente a 93 aislamientos de P. aeruginosa mediante los métodos de dilución en agar y de difusión con discos. Las CIM50 y CIM90 de los carbapenemes fueron (μg/ml): imipenem, 4 y 8; meropenem, 2 y 8; doripenem, 2 y 4, respectivamente. El doripenem fue 1 a 3 diluciones más activo que el imipenem para un 82% de los aislamientos. Comparado con el meropenem, el doripenem fue, 1-3 diluciones más activo frente a un 50% de los aislamientos, mientras que en el 49% la CIM fue la misma. Los porcentajes de resistencia según los métodos de dilución y de difusión fueron: imipenem = 7,5%/49,5% y meropenem = 3,2%/9,7%. Para el doripenem, estos valores variaron según los puntos de corte (PC) que se consideraron: 1,1%/2,2% usando el PC del CLSI para el imipenem y el meropenem, o 1,1%/17,2% según los PC sugeridos por Brown et al. El método de difusión presentó un elevado porcentaje de errores menores en la categorización de los aislamientos respecto de la dilución en agar, lo que sobrestimó la resistencia. El doripenem mostró muy buena actividad frente a P. aeruginosa, superior a la del imipenem y al menos equiparable a la del meropenem, por lo que puede considerarse una interesante opción para el tratamiento de infecciones por esta bacteria.

Doripenem, a new carbapenem, has shown to be more active against Pseudomonas aeruginosa than other carbapenems. The activity of doripenem, imipenem and meropenem was evaluated against 93 P. aeruginosa isolates, by agar dilution and disk diffusion methods. MIC50 and MIC90 were as follows (μg/ml): doripenem, 2 and 4; meropenem, 2 and 8; and imipenem, 4 and 8, respectively. Doripenem MICs were 1 to 3 dilutions lower (i.e. more active) than those for imipenem in 82% of the isolates. In comparison with meropenem, doripenem was 1 to 3 dilutions more active in 50% of the isolates. Forty-nine percent of isolates showed the same MIC for both antibiotics. Resistance percentages for both methods were (dilution/diffusion): imipenem = 7.5%/49.5% and meropenem = 3.2%/9.7%. As the CLSI has not established cut off values for doripenem yet, resistance rates for this antibiotic were estimated by considering (a) the same cut off values for imipenem/meropenem set up by the CLSI, and (b) those suggested by Brown et al. In case (a), resistance rates would be 1.1%/2.2% whereas in case (b) 1.1%/17.2% for agar dilution and disk diffusion, respectively. In scenarios where resistance to carbapenem is based on mechanisms other than carbapenemases, doripenem has a promising future for treating P. aeruginosa infections.