Eradication of carbapenem-resistant Enterobacteriaceae gastrointestinal colonization with nonabsorbable oral antibiotic treatment: A prospective controlled trial

BACKGROUND

Carbapenem-resistant Enterobacteriaceae (CRE) are emerging. In attempt to eradicate CRE colonization, we conducted a semirandomized, prospective, controlled trial using oral nonabsorbable antibiotics.

METHODS

Consecutive hospitalized CRE carriers were studied. Patients whose rectal isolates were gentamicin sensitive but colistin resistant were treated with gentamicin. Patients whose isolates were colistin sensitive but gentamicin resistant were treated with colistin. Patients whose isolates were sensitive to both drugs were randomized to 3 groups of oral antibiotic treatment: gentamicin, colistin, or both. Patients whose isolates were resistant to both drugs, and those who did not consent, were followed for spontaneous eradication.

RESULTS

One hundred fifty-two patients were included; 102 were followed for spontaneous eradication for a median duration of 140 days (controls), and 50 received 1 of the 3 drug regimens: gentamicin, 26; colistin, 16; both drugs, 8, followed for a median duration of 33 days. Eradication rates in the 3 treatment groups were 42%, 50%, and 37.5%, respectively, each significantly higher than the 7% spontaneous eradication rate in the control group (P < .001, P < .001, and P = .004, respectively) with no difference between the regimens. No significant adverse effects were observed.

CONCLUSION

Oral antibiotic treatment with nonabsorbable drugs to which CRE is susceptible appears to be an effective and safe for eradication of CRE colonization and, thereby, may reduce patient-to-patient transmission and incidence of clinical infection with this difficult-to-treat organism.

Acinetobacter baumannii: A Brief Account of Mechanisms of Multidrug Resistance and Current and Future Therapeutic Management

Acinetobacter baumannii, a non-motile, glucose non fermentative, oxidase negative, encapsulated, gram-negative coccobacillus, has recently gained importance because of its increasing resistance to the available antibiotics. Three main mechanisms of resistance in A. baumannii are: enzymes inactivating antibiotics, reduced entry into the target site of bacteria and alteration of the target or cellular functions due to mutations. Multi-drug resistant A. Baumannii, including carbapenam resistant A. Baumannii, are posing a potential threat to mankind by causing lethal infections, especially in ICU set up and in patients who are on ventilators, for which our conventional antibiotics were not shown to be effective. Many reports have indicated carbapenam resistance among A. Baumannii and only colistin and tigecyclyne have shown some promise in combating this lethal microorganism.

Rapid emergence of secondary resistance to gentamicin and colistin following selective digestive decontamination in patients with KPC-2-producing Klebsiella pneumoniae: a single-centre experience

After a single patient was transferred to Leipzig University Hospital from a hospital in Rhodes, Greece, the hospital experienced the largest outbreak due to a KPC-2-producing Klebsiella pneumoniae (KPC-2-KP) strain thus far observed in Germany. Ninety patients hospitalised between July 2010 and October 2012 were affected. In an attempt to eliminate KPC-2-KP from their digestive tracts, 14 consecutive patients (16%) were treated with a short course (7 days) of selective digestive decontamination (SDD), employing colistin (1 million units q.i.d.) and gentamicin (80 mg q.i.d.) as oral solutions, and applying colistin/gentamicin gel (0.5 g) to the oral cavity. In a retrospective analysis, these 14 SDD patients were compared with the remaining 76 patients harbouring KPC-2-KP. KPC-2-KP carrier status was followed in all 14 SDD patients by submitting stool samples to KPC-specific PCR. The mean follow-up period was 48 days (range 12-103 days). Successful elimination of KPC-2-KP was defined as a minimum of three consecutive negative PCR test results separated by ≥48 h each. Decolonisation of KPC-2-KP was achieved in 6/14 patients (43%) after a mean of 21 days (range 12-40 days), but was also observed in 23/76 (30%) of the non-SDD controls (P = 0.102). SDD treatment resulted in the development of secondary resistance to colistin (19% increase in resistance rate) and gentamicin (45% increase) in post-treatment isolates. In the control group, no secondary resistance occurred. We conclude that the SDD protocol applied in this study was not sufficiently effective for decolonisation and was associated with resistance development.

Intravenous colistin in a patient with serious burns and borderline syndrome: the benefits of therapeutic drug monitoring

Colistin is a decades-old drug that fell out of favour due to its nephrotoxicity. Today, colistin is experiencing a renaissance as a treatment against multiresistant Gram-negative bacteria such as Pseudomonas and Acinetobacter in critically ill patients. The optimal dosing of colistin for most infections is unknown. Here we present the intravenous dosing, optimised by therapeutic drug monitoring (TDM), of a borderline patient with severe burns and a consecutive transfemoral amputation. A 32-year-old woman with severe burns (35% total body surface area) and sepsis exhibited normal serum creatinine (SCr) concentrations at the beginning of her intensive care unit (ICU) stay, but over the course of her ICU stay her SCr increased to 100 μmol/L. With the colistin standard dose of 3 × 3 million units (MU) colistin/day after a loading dose of 9 MU, she failed to achieve effective plasma concentrations. The estimated glomerular filtration rate (eGFR) via CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) revealed GFRs between 180 mL/min and 63 mL/min after correcting for body surface. The patient required a high daily dosage of colistin (3 × 6 MU) that exceeded the approved maximum dose. Most clinicians rely heavily on SCr concentrations as the primary biochemical marker of GFR. At most, the CKD-EPI formula is helpful in determining creatinine clearance. The pharmacokinetics of colistin are currently poorly understood. TDM of colistin methanesulfonate and colistin may represent an invaluable approach to optimise colistin drug exposure in ICU patients with fluctuating renal clearance.

In vitro toxicity of colistin on primary chick cortex neurons and its potential mechanism

Colistin is increasingly used as the last-line therapy for infections caused by Gram-negative 'superbugs'. Although colistin neurotoxicity was reported in the literature, there has no data on its mechanism. In the present study, we examined the effect of colistin on primary chick neuron cells, which were treated with 0.83, 4.15 and 8.3μg/mL colistin for 6, 12 and 24h. Cell viability was evaluated with 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assays after exposure to colistin. Formation of reactive oxygen species (ROS), nuclear morphology, caspase-3 activity and internucleosomal DNA fragmentation were examined. The results showed that, compared with the control, no significant change was observed in cell viability, ROS formation and caspase-3 activity in cells treated for 6, 12 and 24h with 0.83μg/mL colistin. However, in the 4.15 and 8.3μg/mL colistin-treated groups, the viability of chick primary neurons significantly decreased at 12 and 24h, respectively; caspase-3 activities were significantly increased to 5.1 and 7.4 fold at 6h, more earlier than the changes of ROS, which was significant increased to 124.5% and 143.5% (P<0.01) of control at 12h, respectively. The apoptosis of neuron cells was revealed by both nuclear morphological observations and internucleosomal DNA fragmentation in the 4.15 and 8.3μg/mL colistin-treated groups at 6, 12 and 24h. Our data demonstrated that colistin can induce apoptosis in primary chick cortex neurons through caspase-3 activation, which may be contributed with ROS-dependent and independent mechanism.

Global survey of polymyxin use: A call for international guidelines

Polymyxins (polymyxin B and colistin) are older bactericidal antibiotics that are increasingly used to treat infections caused by multidrug-resistant (MDR) Gram-negative bacteria. However, dosing and clinical use of these drugs vary widely. This survey was undertaken to reveal how polymyxins are used worldwide. Data were collected through a structured online questionnaire consisting of 24 questions regarding colistin usage patterns and indications as well as colistin dosage for adult patients. The questionnaire was disseminated in 2011 to relevant experts worldwide and was completed by 284 respondents from 56 different countries. Respondents from 11/56 countries (20%) had no access to colistin; 58/284 respondents (20.4%) reported that in 2010 they experienced that colistin was not available when needed. Formulations of polymyxins used were reported as: colistimethate sodium (48.6%); colistin sulfate (14.1%); both (1.4%); polymyxin B (1.4%); and unknown. Intravenous formulations were used by 84.2%, aerosolised or nebulised colistin by 44.4% and oral colistin for selective gut decontamination by 12.7%. Common indications for intravenous colistin were ventilator-associated pneumonia, sepsis and catheter-related infections with MDR Gram-negative bacteria. Only 21.2% of respondents used a colistin-loading dose, mainly in Europe and North America. This survey reveals that the majority of respondents use colistin and a few use polymyxin B. The survey results show that colistin is commonly underdosed. Clear guidance is needed on indications, dosing and antibiotic combinations to improve clinical outcomes and delay the emergence of resistance. Colistin should be considered a last-resort drug and its use should be controlled. International guidelines are urgently needed.

Multicomponent antibiotic substances produced by fermentation: implications for regulatory authorities, critically ill patients and generics

Teicoplanin and polymyxin E (colistin) are antibiotics consisting of multiple, closely related subcomponents, produced by fermentation. The principal components comprise a complex mixture of chemically related, active substances (teicoplanin A(2-1)-A(2-5) and polymyxin E(1-2), respectively), which might be required to be present in specific ratios to ensure optimal antibacterial and clinical efficacy. These subcomponents differ in their fatty acid and amino acid composition and, as such, the lipophilic and protein binding characteristics differ between components. This has therapeutic implications for critically ill patients, as the volume of distribution of the teicoplanin A2 and polymyxin E analogues at the onset of an intravenous infusion may impact on expected pharmacokinetics and influence outcome.

Simultaneous quantification of antimicrobial agents for multidrug-resistant bacterial infections in human plasma by ultra-high-pressure liquid chromatography-tandem mass spectrometry

Antibiotic-resistant bacterial infection is one of the most serious clinical problems worldwide. Vancomycin, teicoplanin, daptomycin, and colistin are glycopeptide and lipopeptide antibiotics that are frequently used to treat multidrug-resistant bacterial infections. Therapeutic drug monitoring is recommended to ensure both safety and efficacy and to improve clinical outcomes. This study developed a fast, simple, and sensitive ultra-high-pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for the simultaneous determination of the concentrations of these four drugs in human plasma. The sample preparation process includes a simple protein denaturation step using acetonitrile, followed by an 11-fold dilution with 0.1% formic acid. Eight target peaks for the four drugs can be analyzed within 3 min using a Kinetex™ 2.6 μm C18 column. The mass spectrometry parameters were optimized, and two transitions for each target peak were used for multiple reaction monitoring, which provided high sensitivity and specificity. The UHPLC-MS/MS method was validated over clinical concentration ranges. The intra-day and inter-day precisions for the ratio of the peak area of each analyte to the peak area of the internal standard were all below 12.7 and 14.7% relative standard deviations, respectively. The accuracy at low, medium, and high concentrations of the eight target peaks was between 89.3 and 110.7%. The standard curves for the analytes were linear and had coefficients of determination higher than 0.997. The limits of detection were all below 70 ng mL(-1). The use of this method to analyze patient plasma samples confirmed that it is effective for the therapeutic drug monitoring of these four drugs and can be used to improve the therapeutic efficacy and safety of treatment with antibiotics.

Differences in pharmacokinetics and pharmacodynamics of colistimethate sodium (CMS) and colistin between three different CMS dosage regimens in a critically ill patient infected by a multidrug-resistant Acinetobacter baumannii

Use of colistin has re-emerged for the treatment of infections caused by multidrug-resistant (MDR) Gram-negative bacteria, but information on its pharmacokinetics and pharmacodynamics is limited, especially in critically ill patients. Recent data from pharmacokinetic/pharmacodynamic (PK/PD) population studies have suggested that this population could benefit from administration of higher than standard doses of colistimethate sodium (CMS), but the relationship between administration of incremental doses of CMS and corresponding PK/PD parameters as well as its efficacy and toxicity have not yet been investigated in a clinical setting. The objective was to study the PK/PD differences of CMS and colistin between three different CMS dosage regimens in the same critically ill patient. A critically ill patient with nosocomial pneumonia caused by a MDR Acinetobacter baumannii received incremental doses of CMS. During administration of the different CMS dosage regimens, CMS and colistin plasma concentrations were determined and PK/PD indexes were calculated. With administration of the highest CMS dose once daily (720 mg every 24h), the peak plasma concentration of CMS and colistin increased to 40.51 mg/L and 1.81 mg/L, respectively, and the AUC0-24/MIC of colistin was 184.41. This dosage regimen was efficacious, and no nephrotoxicity or neurotoxicity was observed. In conclusion, a higher and extended-interval CMS dosage made it possible to increase the exposure of CMS and colistin in a critically ill patient infected by a MDR A. baumannii and allowed a clinical and microbiological optimal response to be achieved without evidence of toxicity.

Polymyxins and Doripenem Combination Against KPC-Producing Klebsiella pneumoniae

BACKGROUND

Most KPC-producing organisms have maintained susceptibility to polymyxins; however, development of resistance to polymyxins has been increasingly reported. One potential treatment modality is to optimize the use of combination therapy. Therefore, we evaluated the in vitro activity of doripenem, colistin sulfate, polymyxin B alone and in combination against KPC- producing K. pneumoniae.

METHODS

In-vitro time-kill assays were performed for four non-duplicate KPC-3 producing K. pneumoniae isolates with the following antibiotics: doripenem, polymyxin B and colistin sulfate alone and in combination. Bacterial densities were determined at 0, 4, 8, 12, 24 and 48 hours. Bactericidal activity was defined as ≥ 3-log10 CFU/mL reduction from the starting inoculum. Synergism was defined as ≥ 2-log10 reduction with the combination when compared to the most active single agent at 24 hours.

RESULTS

Minimum inhibitory concentrations (MICs) for polymyxin B and colistin sulfate ranged from 0.0625 to 0.25 µg/mL, and all isolates were resistant to doripenem (MICs ranged 16 - 32 µg/mL). Monotherapy with colistin sulfate and polymyxin B displayed bacterialcidal activity within 12 hours; however, significant re-growth occurred by 24 hours in all isolates. Monotherapy with doripenem did not show bactericidal activity in any isolate. Synergy occurred with combinations of both colistin sulfate and polymyxin B with doripenem against all isolates and was sustained at 48 hours. Combinations of colistin sulfate or polymyxin B with doripenem demonstrated rapid bactericidal activity by 4 hours in all isolates and was sustained for 24 hours.

CONCLUSION

Polymyxin B and colistin sulfate in combination with doripenem may be an important treatment modality in treating KPC-producing organisms.

Successful management of nosocomial ventriculitis and meningitis caused by extensively drug-resistant Acinetobacter baumannii in Austria

Nosocomial infections caused by the Gram-negative coccobacillus Acinetobacter baumannii have substantially increased over recent years. Because Acinetobacter is a genus with a tendency to quickly develop resistance to multiple antimicrobial agents, therapy is often complicated, requiring the return to previously used drugs. The authors report a case of meningitis due to extensively drug-resistant A baumannii in an Austrian patient who had undergone neurosurgery in northern Italy. The case illustrates the limits of therapeutic options in central nervous system infections caused by extensively drug-resistant pathogens.

Prognostic differences between VAP from Acinetobacter baumanii and VAP from other microorganisms

Nosocomial infection, in particular pneumonia, is an important risk factor for hospital mortality and morbidity. Acinetobacter baumanii is a common multi-resistant microorganism responsible of Ventilator Associated Pneumonia (VAP). Currently Colistin is a rescue therapy for this pathogen. The purpose of this retrospective study is to compare the outcome of VAP caused by Acinetobacter baumanii and VAP from other microorganisms in critical patients. Comorbidity, prognostic scores, mortality and eradication frequency did not turn out significantly different between the two study groups. Colistin safety was tested.

Utilization of colistin for treatment of multidrug-resistant Pseudomonas aeruginosa

BACKGROUND

Colistin is uncommonly used in clinical practice; however, the emergence of multidrug-resistant organisms has rekindled interest in this potentially toxic therapeutic option. The present study describes the authors' experience with colistin in the management of patients who were infected with metallo-beta-lactamase (MBL)-producing Pseudomonas aeruginosa within the Calgary Health Region (Calgary, Alberta).

METHOD

Adult patients who received colistimethate sodium (colistin) between January 2000 and December 2005 were identified via pharmacy records, and their charts were reviewed retrospectively. Patients with cystic fibrosis were excluded. Patient demographics, clinical course and relevant laboratory data were extracted.

RESULTS

Twenty-eight courses of colistin were received by 22 patients. The majority of these treatments were directed at MBL-producing Pseudomonas. One-half of the patients received nebulized colistin. Intravenous (IV) colistin was administered to 12 patients for a mean +/- SD of 14.7+/-13.8 days (range 3.7 to 46 days). The highest IV dose used was 125 mg every 6 h or 6 mg/kg/day. Eight of 12 patients (67%) treated with IV colistin responded either fully or partially. Two patients received IV colistin as outpatients. Adverse effects considered to be due to colistin included drug fever, nephrotoxicity and neurotoxicity. Five of nine patients (56%) who had complete data available for evaluation had at least a doubling of creatinine levels from baseline.

CONCLUSION

Patients in the present study received both IV and nebulized colistin for multidrug-resistant P aeruginosa. The use of IV colistin was associated with a favourable response, but mild nephrotoxicity occurred in two-third of patients. It was concluded that colistin may be a useful drug when choices are limited.

The outcomes of using colistin for treating multidrug resistant Acinetobacter species bloodstream infections

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 ≥ 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.