Multidrug resistant Acinetobacter baumanii: clinical update and new highlights

A. HERNÁNDEZ, E. GARCÍA, G. YAGÜE, J. GÓMEZ 

 

The role of multidrug resistant Acinetobacter baumanii and its clinical relevance have been recently appreciated as a ubiquitous opportunistic nosocomial pathogen. Risk factors associated with A. baumanii infection include severe underlying diseases, previous surgery, invasive procedures, treatment with broad-spectrum antibiotics, length of hospital stay, admission to intensive care units (ICU). Carbapenem-multidrug resistant A. baumanii infections are probably associated to greater severity and more complications; in our cohort mortality was 49.3% and related mortality (within 72 hours) was 10.39%. However, severe underlying diseases probably play an important role in the clinical outcome of patients with MDR-C A. baumanii infection and controversy exists regarding the real mortality attributable to antimicrobial resistance because a high proportion of deaths took place > 7 days after diagnosis. Nevertheless, in our experience, carbapenem resistance, inappropriate therapy and monotherapy are associated to a higher mortality. Special attention should be paid to design well-controlled prospective clinical trials to determine the optimal antimicrobial therapy in critically ill patients suspected of having MDR Acinetobacter infection.

 
Rev Esp Quimioter 2010:23(1):12-19 [pdf]

Pseudomonas aeruginosa: antimicrobial resistance in clinical isolates. Castellón 2004 -2008

F. J. PARDO, M. D. TIRADO, E. D. GARCÍA, J. GRANADOS, A. CAMPOS, R. MORENO 

 

Retrospective study of antimicrobial susceptibility of 1.943 Pseudomonas aeruginosa clinical isolates to amikacin, tobramycin, gentamicin, ceftazidime, cefepime, meropenem, piperacillin-tazobactam and ciprofloxacin during a five year period. The percentage of resistance went from 2.07% to amikacin from 15.89% to ciprofloxacin. These percentages showed differences depending on the extra or intrahospitalary origin, departments and samples. Isolates from hospital patients were significantly more resistant than the ones from ambulatory patients (p≤0.001:tobramycin, 13.74% vs 5.05%; gentamicin, 13.74% vs 8.26%; ceftazidime, 12.67% vs 4.24%; cefepime, 11.48% vs 7.07%; meropenem, 8.57% vs 2.06%),except for amikacin (1.98% vs 2.2%, p=0.74), piperacillin/tazobactam (6.07% vs 4.55%, p=0.14) and ciprofloxacin (17.17% vs 13.97%, p=0.06). Critical care department and respiratory samples showed the highest resistance percentages while surgery department and invasive samples showed the lowest. Multidrug-resistance was found in 4.8% of the isolates. When comparing our data with those from our previous study (1992-2003), we observed a significant reduction in antibiotic resistance to amikacin (7.74% vs 2.07%, p<0.001), tobramycin (13.61% vs 10.26%, p<0.001), gentamicin (30,85% vs 14.73%, p<0,001), ceftazidime (14.63% vs 9,28%, p<0.001), cefepime (12,31% vs 9.71%, p=0.005), and meropenem (7.74% vs 2.07%, p=0.001); and there were no changes in resistance to piperacillin- tazobactam (4.26% vs 5.46%, p=0,06) and ciprofloxacin (16.02% vs 15.89%, p=0.89). In the last years, the susceptibility pattern of P. aeruginosa to antimicrobial agents has changed in our health district, and it is very different from the one described in national studies so it would be very important to monitore susceptibility of clinical isolates periodically.

 
Rev Esp Quimioter 2010:23(1):20-26 [pdf]

Linezolid more efficacious than vancomycin to eradicate infecting organism in critically ill patients with Gram-positive infections

J. M. SIRVENT, L. PIÑEIRO, M. DE LA TORRE, M. MOTJÉ, J. DE BATLLE, A. BONET

 

Objetive: A prospective and observational study has been conducted to analyze the efficacious of linezolid compared to vancomycin to eradicate the infecting organism in critically ill patients with Gram-positive infections.
Patients and Methods: Prospective, observational and non-controlled study in a medical-surgical intensive care unit (ICU) in a university hospital. A total number of 53 critically ill patients with therapy to proven Grampositive bacterial infection were studied. Infected patients were diagnosed and treated according to international guidelines, following standard protocol for the critically ill infected patients. Microbiologic eradication of the infecting organism at the seventh day of treatment and patients’ clinical outcome were analysed.
Results: Twenty-seventh patients received linezolid and twenty-six received vancomycin. Infection-site diagnoses were: hospital-acquired pneumonia (21 cases: 39.6%), complicated surgical-site infection (19 cases: 35.8%) and catheter-related bacteraemia (13 cases: 24.5%).The most important isolated microorganism was methicillin-resistant Staphylococcus aureus (MRSA) (28 cases:52.8%). Clinical success was 20/27 (74.1%) in the linezolid group and 16/26 (61.5 %) in the vancomycin group, with p= 0.3. The adjusted logistic regression model demonstrated that the treatment with linezolid is associated to microbiologic eradication of the infecting organism at the seventh day of treatment [OR = 7.88 (95% CI 1.86-33.52)] and p = 0.005. In this model, the length of hospital stay was lower in the group with microbiologic eradication at the seventh day (p = 0.015). Drug-related adverse events were comparable in both groups of treatment.
Conclusion: Treatment with linezolid in critically ill patients with Gram-positive infections was equivalent to vancomycin in terms of efficacy and safety, but linezolid was associated to a higher rate of microbiologic eradication of the infecting organism at the seventh day of treatment.

 
Rev Esp Quimioter 2010:23(1):27-35 [pdf]

Changes in the antimicrobial susceptibility of Escherichia coli isolates from community diagnosed urinary tract infections during the period 2003-2007. Multicentre study in Castilla la Mancha (Spain)

D. TENA, A. GONZÁLEZ-PRAETORIUS, J. C. GONZÁLEZ, E. HEREDERO, S. ILLESCAS, C. SAINZ DE BARANDA, G. SESEÑA

 

Objective: To know the evolution of susceptibility patterns of Escherichia coli in patients with communitydiagnosed urinary tract infections (UTIs) during last years in Castilla la Mancha (Spain).
Methods: Descriptive and retrospective study performed between january 2003 and december 2007. We studied data about frequency and susceptibility of 33.651 E. coli isolates from urine cultures that were remited from primary care centres depending of 6 hospitals in Castilla la Mancha (Spain).
Results: Susceptibility rates of E. coli for most antibiotics decreased significantly during the 5-year period, especially for amoxicillin-clavulanic acid, cefuroxime and quinolones. Average rates of susceptibility for amoxicillin- clavulanic acid, ciprofloxacin, cefuroxime, fosfomycin and nitrofurantoin were: 86,7, 75,4, 87,3, 97,6 and 96,2%, respectively. We observed a significantly increase of E. coli isolates producing extended-spectrum betalactamases (ESBLs), from 1,9% in 2003 to 4,9% in 2007 (χ2 TL = 143,6, p<0,001).
Conclusions: We observed a significantly reduction of E. coli susceptibility for most antibiotics and an increase of E. coli isolates producing ESBLs. Fosfomycin and nitrofurantoin are the best choices for empiric treatment. Prospective studies should be performed in the future to confirm the results of our study.

 
Rev Esp Quimioter 2010:23(1):36-42 [pdf]

Evaluation of pharmacodynamic target attainment with vancomycin treatment of bacteremia due to Staphylococcus aureus methicillin resistant

J. A. LEPE, M. V. GIL-NAVARRO, M. D. SANTOS-RUBIO, J. BAUTISTA, J. AZNAR

 

Objective: The objective of the study is to evaluate the ability of standard vancomycin dosing strategies actually recommended to attain the pharmacodynamic target of an area under the curve of vancomycin serum concentration versus time from 0 to 24 hours (AUC24h) to minimum inhibitory concentration (MIC) ratio greater than 400:1 for patients with a suspected or documented methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia by individual analysis and Monte Carlo simulation.
Material and methods: The study included all patients admitted with suspected or proven MRSA infection during the years 2007-2008, and who were initially treated with vancomycin at a dose of 30 mg/kg/day, and underwent pharmacokinetic monitoring. The area under the curve of vancomycin serum concentration versus time from 0 to 24 hours (AUC24h) was calculated as daily dose/clearance total (D24h/CL). Additionally, we studied 45 isolates of MRSA obtained from blood cultures in the period 2007-2008. The MIC to vancomycin was determined using Epsilon-test®. The PK-PD parameter calculated was AUC24h/MIC. Microsoft
Excel was used to perform a 10.000 subject Monte Carlo simulation. An AUC24h/MIC ≥ 400 was assumed as the target attainment.
Results: In the individual study, the percentage of patients with AUC24h/MIC50/90 ≥ 400 was 50%. The probability (%) of attaining AUC24h/MIC ratio values ≥ 400 by Monte Carlo simulation was of 66%. The vancomycin MIC value from which the scenario would have to wait a suboptimal treatment (target <90%) was >1 mg/L.
Discussion: This study shows that in the population studied to achieve a vancomycin AUC24h/MIC ≥ 400 is not always attained with the standard dose. Therefore, one would expect a high probability of suboptimal vancomycin AUC24h/MIC ratios for patients infected with organisms with vancomycin MICs of >1 mg/L treated with doses of 30 mg/kg/day.

 
Rev Esp Quimioter 2010:23(1):43-47 [pdf]