A biothermal activity detection method has been established to determine the potency of colistin. The biothermal activity fingerprints of E. coli with colistin were determined. There was a good linear relationship (r = 0.993) between logarithm concentration of colistin (lgC) and lag rate of growing time (Deltat%) when the concentrations of colistin ranged from 17.0 to 41.6 u x mL(-1). The average recovery rate was 100.3% (n = 9). Using this method, there was no significant difference between results of colistin potency measurement and those using cup-plate method (P > 0.05). As a result, biothermal activity detection method is sensitive, accurate, rapid, convenient and feasible to determine the potency of colistin. This method can also be applied in real time and online to monitor the process of bacterial growth and could be complementary to the cup-plate method.
Anti-Bacterial Agents ; administration & dosage ; pharmacology ; Calorimetry ; methods ; Colistin ; administration & dosage ; pharmacology ; Dose-Response Relationship, Drug ; Escherichia coli ; drug effects ; growth & development ; Microbial Sensitivity Tests ; methods ; Thermodynamics

PURPOSE: Colistin is used for the treatment of pneumonia associated with multidrug-resistant Acinetobacter baumannii and Pseudomonas aeruginosa. However, the best route of administration and dosage is not known. We report our experience with aerosolized colistin in twelve patients with pneumonia caused by colistin-only-susceptible (COS) A. baumannii. MATERIALS AND METHODS: We retrospectively reviewed patients' medical records who were treated with aerosolized colistin for the treatment of pneumonia. RESULTS: Ten patients were treated only with aerosolized colistin inhalation and two patients received a 3-day course intravenous colistin, and then switched to colistin inhalation therapy. The median duration of aerosolized colistin therapy was 17 days (5-31 days). Four patients were treated only with aerosolized colistin, whereas 4 patients received concomitant glycopeptides, and 4 received concomitant levofloxacin or cefoperazone/sulbactam. At the end of the therapy, the clinical response rate and bacteriological clearance rate was 83% and 50%, respectively. Colistin-resistant strains were isolated from 3 patients after aerosolized colistin therapy; however, all of them showed favorable clinical response. The median interval between inhalation therapy and resistance was 7 days (range 5-19 days). Acute kidney injury developed in 3 patients. Two patients experienced Clostridium difficile associated diarrhea. One patient developed fever and skin rash after aerosolized colistin therapy. No patient developed neurotoxicity or bronchospasm. CONCLUSION: Colistin inhalation therapy is deemed tolerable and safe, and could be beneficial as an adjuctive therapy for the management of pneumonia due to COS A. baumannii. However, the potential development of colistin resistance cannot be overlooked.
Acinetobacter baumannii/drug effects/*pathogenicity ; Administration, Inhalation ; Aged ; Anti-Bacterial Agents/administration & dosage/*therapeutic use ; Colistin/administration & dosage/*therapeutic use ; Female ; Humans ; Male ; Middle Aged ; Pneumonia/*drug therapy ; Retrospective Studies

BACKGROUND: Acinetobacter infections are difficult to treat as they often exhibit multiple resistance to the antibiotics that are currently available for the treatment of pneumonia. Colistin is active against gram-negative bacteria, including the multiple drug resistant (MDR) Acinetobacter species. However, intravenous administration of colistin was abandoned because of its nephrotoxicity and neurotoxicity. The aims of this study were to examine the efficacy and safety of colistin administered by aerosol in the treatment of pneumonia caused by MDR Acinetobacter baumannii. METHODS: We retrospectively reviewed the medical records of patients admitted to the intensive care unit (ICU) from Dec. 2006 to Aug. 2007 who had been diagnosed as suffering from pneumonia due to MDR Acinetobacter baumannii and had been treated with nebulized colistin. RESULTS: 31 patients received aerosolized colistin. The average duration of the treatment was 14+/-7 days and the daily dose of ranged from 225 mg to 300 mg. All patients received concomitant intravenous antimicrobial agents. The average length of the stay in the ICU was 34+/-21 days and in the hospital 58+/-52 days. The overall microbiological eradication was observed in 25 patients (80.6%). 14 of these (56%) were cured, and 11 (44%) were infected with other microorganisms. The overall crude mortality of the ICU was 48%. Nephrotoxicity and significant bronchial constriction did not occur in any patient during neublized colistin treatment. CONCLUSION: Nebulized colistin may be a safe and effective option in the treatment of pneumonia due to MDR Acinetobacter baumannii. Its role in therapy warrants further investigation in comparative studies.
Acinetobacter ; Acinetobacter baumannii ; Acinetobacter Infections ; Administration, Intravenous ; Anti-Bacterial Agents ; Anti-Infective Agents ; Bronchoconstriction ; Colistin ; Gram-Negative Bacteria ; Humans ; Intensive Care Units ; Medical Records ; Pneumonia ; Retrospective Studies ; Stress, Psychological

BACKGROUNDAerosolized amikacin (AA) is a current option for the management of ventilator-associated pneumonia (VAP) caused by multidrug-resistant Gram-negative bacteria (MDR-GNB), as it is reported that AA could increase the alveolar level of the drug without increasing systemic toxicity. This study aimed to evaluate the efficacy and safety of AA as an adjunctive therapy for VAP caused by MDR-GNB.

METHODSIn this single-center, double-blind study conducted in a 36-bed general Intensive Care Unit (ICU) in a tertiary hospital from June 2014 to June 2016, 52 ICU patients with confirmed MDR-GNB VAP were randomized to two groups (AA group, n = 27 and placebo group, n = 25). Amikacin (400 mg, q8h) or saline placebo (4 ml, q8h) was aerosolized for 7 days. The attending physician determined the administration of systemic antibiotics for VAP. Patients were followed up for 28 days. Bacteriological eradication, clinical pulmonary infection score (CPIS), and serum creatinine were assessed on day 7 of therapy. New resistance to amikacin, cure rate of VAP, weaning rate, and mortality were assessed on day 28.

RESULTSThe baseline characteristics of patients in both groups were similar. At the end of the treatment, 13 of the 32 initially detected bacterial isolates were eradicated in AA group, compared to 4 of 28 in placebo group (41% vs. 14%, P= 0.024). As for patients, 11 of 27 patients treated with AA and 4 of 25 patients treated with placebo have eradication (41% vs. 16%, P= 0.049). The adjunction of AA reduced CPIS (4.2 ± 1.6 vs. 5.8 ± 2.1, P= 0.007). New drug resistance to amikacin and the change in serum creatinine were not detected in AA group. No significant differences in the clinical cure rate in survivors (48% vs. 35%, P= 0.444), weaning rate (48% vs. 32%, P= 0.236), and mortality (22% vs. 32%, P= 0.427) were detected between the two groups on day 28.

CONCLUSIONSAs an adjunctive therapy of MDR-GNB VAP, AA successfully eradicated existing MDR organisms without inducing new resistance to amikacin or change in serum creatinine. However, the improvement of mortality was not found.

Administration, Inhalation ; Aged ; Amikacin ; administration & dosage ; therapeutic use ; Anti-Bacterial Agents ; administration & dosage ; therapeutic use ; Colistin ; administration & dosage ; therapeutic use ; Double-Blind Method ; Drug Resistance, Multiple, Bacterial ; Female ; Gram-Negative Bacteria ; drug effects ; pathogenicity ; Humans ; Intensive Care Units ; statistics & numerical data ; Male ; Middle Aged ; Pneumonia, Ventilator-Associated ; drug therapy

Despite the identification of Acinetobacter baumannii isolates that demonstrate susceptibility to only colistin, this antimicrobial agent was not available in Korea until 2006. The present study examined the outcomes of patients with multidrug resistant (MDR) Acinetobacter species bloodstream infection and who were treated with or without colistin as part of their regimen. The colistin group was given colistin as part of therapy once colistin became available in 2006. The non-colistin group was derived from the patients who were treated with other antimicrobial regimens before 2006. Mortality within 30 days of the onset of bacteremia occurred for 11 of 31 patients in the colistin group and for 15 of 39 patients in the non-colistin group (35.5% vs 38.5%, respectively, P = 0.80). Renal dysfunction developed in 50.0% of the 20 evaluable patients in the colistin group, but in 28.6% of the 35 evaluable patients in the non-colistin group (P = 0.11). On multivariate analysis, only an Acute Physiological and Chronic Health Evaluation II score > or = 21 was associated with mortality at 30 days. This result suggests that administering colistin, although it is the sole microbiologically appropriate agent, does not influence the 30 day mortality of patients with a MDR Acinetobacter spp. bloodstream infection.
APACHE ; Acinetobacter/*drug effects/isolation & purification ; Acinetobacter Infections/*drug therapy/mortality ; Adolescent ; Adult ; Aged ; Aged, 80 and over ; Anti-Bacterial Agents/*therapeutic use ; Bacteremia/*drug therapy/mortality ; Child ; Colistin/administration & dosage/*therapeutic use ; Drug Resistance, Multiple, Bacterial/*drug effects ; Female ; Humans ; Male ; Middle Aged ; Republic of Korea ; Retrospective Studies ; Risk ; Treatment Outcome

BACKGROUND: Acinetobacter baumannii has emerged as a major cause of nosocomial outbreaks. It is particularly associated with nosocomial pneumonia and bloodstream infections in immunocompromised and debilitated patients with serious underlying pathologies. Over the last two decades, a remarkable rise in the rates of multidrug resistance to most antimicrobial agents that are active against A. baumannii has been noted worldwide. We evaluated the rates of antimicrobial resistance and changes in resistance over a 5-year period (2010–2014) in A. baumannii strains isolated from hospitalized patients in a tertiary Greek hospital. MATERIALS AND METHODS: Identification of A. baumannii was performed by standard biochemical methods and the Vitek 2 automated system, which was also used for susceptibility testing against 18 antibiotics: ampicillin/sulbactam, ticarcillin, ticarcillin/clavulanic acid, piperacillin, piperacillin/tazobactam, cefotaxime, ceftazidime, cefepime, imipenem, meropenem, gentamicin, amikacin, tobramycin, ciprofloxacin, tetracycline, tigecycline, trimethoprim/sulfamethoxazole, and colistin. Interpretation of susceptibility results was based on the Clinical and Laboratory Standards Institute criteria, except for tigecycline, for which the Food and Drug Administration breakpoints were applied. Multidrug resistance was defined as resistance to ≥3 classes of antimicrobial agents. RESULTS: Overall 914 clinical isolates of A. baumannii were recovered from the intensive care unit (ICU) (n = 493), and medical (n = 252) and surgical (n = 169) wards. Only 4.9% of these isolates were fully susceptible to the antimicrobials tested, while 92.89% of them were multidrug resistant (MDR), i.e., resistant to ≥3 classes of antibiotics. ICU isolates were the most resistant followed by isolates from surgical and medical wards. The most effective antimicrobial agents were, in descending order: colistin, amikacin, trimethoprim/sulfamethoxazole, tigecycline, and tobramycin. Nevertheless, with the exception of colistin, no antibiotic was associated with a susceptibility rate >40% for the entire study period. The most common phenotype showed resistance against ampicillin/sulbactam, cephalosporins, carbapenems, aminoglycosides, ciprofloxacin, and tigecycline. An extremely concerning increase in colistin-resistant isolates (7.9%) was noted in 2014, the most recent study year. CONCLUSION: The vast majority of A. baumannii clinical isolates in our hospital are MDR. The remaining therapeutic options for critically ill patients who suffer from MDR A. baumannii infections are severely limited, with A. baumannii beginning to develop resistance even against colistin. Scrupulous application of infection control practices should be implemented in every hospital unit. Lastly, given the lack of available therapeutic options for MDR A. baumannii infections, well-controlled clinical trials of combinations of existing antibiotics are clearly needed.
Acinetobacter baumannii* ; Acinetobacter* ; Amikacin ; Aminoglycosides ; Anti-Bacterial Agents ; Anti-Infective Agents ; Carbapenems ; Cefotaxime ; Ceftazidime ; Cephalosporins ; Ciprofloxacin ; Colistin ; Critical Illness ; Disease Outbreaks ; Drug Resistance, Multiple ; Gentamicins ; Hospital Units ; Humans ; Imipenem ; Infection Control ; Intensive Care Units ; Pathology ; Phenotype ; Piperacillin ; Pneumonia ; Tetracycline ; Ticarcillin ; Tobramycin ; United States Food and Drug Administration