In vivo evolution of resistant subpopulations of KPC-producing Klebsiella pneumoniae during ceftazidime/avibactam treatment.

Objectives: KPC-producing Klebsiella pneumoniae (KPC-Kp) represent a serious problem worldwide. Herein, we describe the evolution of ceftazidime/avibactam resistance by sequencing longitudinal clinical isolates from a patient with KPC-Kp bloodstream infection undergoing ceftazidime/avibactam treatment. Methods: WGS was performed on one ceftazidime/avibactam-susceptible KPC-Kp (BOT-CA-S) and two phenotypically different ceftazidime/avibactam-resistant KPC-Kp with low (BOT-CA-R) and high (BOT-EMO) carbapenem MICs. The population diversity was assessed by the frequency of allele mutations and population analysis profiles (PAPs). Results: Phylogenetic analysis demonstrated clonal relatedness of the KPC-Kp isolates, all belonging to the clone ST1519. The D179Y mutation in blaKPC-3 was detected in both of the ceftazidime/avibactam-resistant KPC-Kp, whereas it was absent in the ceftazidime/avibactam-susceptible isolate. The mutation emerged independently in the two ceftazidime/avibactam-resistant isolates and was associated with a significant reduction in carbapenem MICs in BOT-CA-R, but not in BOT-EMO. WGS analysis revealed that the frequency of the D179Y mutation was 96.32% and 51.05% in BOT-CA-R and BOT-EMO, respectively. PAP results demonstrated that carbapenem resistance in BOT-EMO was due to the coexistence of mixed subpopulations harbouring WT and mutated blaKPC-3. A bacterial subpopulation with high ceftazidime/avibactam resistance for BOT-EMO KPC-Kp showed low carbapenem MICs, whereas a subpopulation with high meropenem resistance had a low MIC of ceftazidime/avibactam. Conclusions: Our analysis indicates that mixed subpopulations of ceftazidime/avibactam-resistant KPC-Kp emerge after ceftazidime/avibactam treatment. The evolution of different subpopulations that are highly resistant to ceftazidime/avibactam likely contributes to treatment failure, thereby highlighting the need for combination treatment strategies to limit selection of ceftazidime/avibactam-resistant KPC-Kp subpopulations.

Use of Monte Carlo simulation to evaluate the efficacy of tigecycline and minocycline for the treatment of pneumonia due to carbapenemase-producing Klebsiella pneumoniae.

BACKGROUND: Pneumonia caused by carbapenemase-producing Klebsiella pneumoniae (CP-KP) are increasingly encountered in hospitals worldwide, causing high mortality due to lack of treatment options. The goal of this study was to assess the efficacy of tigecycline and minocycline for CP-KP hospital-acquired pneumonia (HAP) by using Monte Carlo simulation. METHODS: A total of 164 non-duplicated CP-KP strains were collected from sputum or blood in patients with HAP. The MICs for antimicrobials were determined by the agar dilution method. A 10,000-patient Monte Carlo Simulation based on a PK/PD model incorporating the MICs and population pharmacokinetic parameters were conducted to calculate probability of target attainment (PTA) at each MIC value and total cumulative fraction of response (CFR). RESULTS: The susceptibility rate of tigecycline and minocycline were 79.9% and 41.5%, respectively. At recommended doses, an optimal PTA of 90% was obtained for treating HAP caused by CP-KP with MICs of tigecycline ≤0.5 mg/L or minocycline ≤4 mg/L. The CFR of tigecycline at the recommended dose and double dose (100 mg q12h) were 71.2% and 90.2%, respectively. The CFR of minocycline at recommended dose and double dose (200 mg q12h) was 53.4% and 77.2%, respectively. CONCLUSIONS: The findings of this study suggest that the recommended dose of tigecycline was not effective in HAP caused by CP-KP, and a higher CFR indicating a better clinical efficacy can be gained by doubling the dose (100 mg q12h). minocycline (200 mg q12h) might be a potential alternative of tigecycline to against strains with MICs ≤ 8 mg/L.

Meropenem for treating KPC-producing Klebsiella pneumoniae bloodstream infections: Should we get to the PK/PD root of the paradox?

The objective of this study was to assess the achievement of pharmacokinetic/pharmacodynamic (PK/PD) targets of meropenem (MEM) in critically-ill patients with bloodstream infections (BSI) due to Klebsiella pneumoniae-carbapenemase-producing Klebsiella pneumoniae (KPC-Kp) with MEM minimum inhibitory concentrations (MICs) ≥16 mg/L. Nineteen critically-ill patients with KPC-Kp BSI were given combination therapy including MEM, tigecycline, plus colistin or gentamicin (according to susceptibility testing). MEM was administered as an extended 3-hour infusion of 2 g every 8 hours, or adjusted according to renal function. MEM plasma concentrations were determined by high-performance liquid chromatography. PK/PD targets for MEM were defined as T > 40% 1×MIC and T > 40% 4×MIC. Possible synergisms between MEM and coadministered agents were assessed by time-kill assays based on plasma levels for MEM and on fixed plasma concentrations for the other agents. In none of 19 patients MEM reached any PK/PD target. The actual MEM MICs were 256, 512, and 1024 mg/L in 1, 3, and 15 isolates, respectively. However, theoretically, the PK/PD target of T > 40% 1×MIC could have been achieved in 95%, 68%, 32% and 0% of the isolates for MIC equal to 8, 16, 32, and 64 mg/L, respectively. No synergisms were observed between MEM and coadministered agents. In conclusion, high-dose MEM failed to reach PK/PD targets in 19 patients with BSI due to KPC-Kp with very high MEM MICs. On a theoretical basis, our results suggest a possible usefulness of MEM against resistant blood isolates with MICs up to 32 mg/L.

The therapeutic effect of tigecycline, unlike that of Ceftazidime, is not influenced by whether the Klebsiella pneumoniae strain produces extended-spectrum ß-lactamases in experimental pneumonia in rats.

The efficacies of tigecycline and ceftazidime against fatal pneumonia in rats caused by an extended-spectrum ß-lactamase (ESBL)-positive Klebsiella pneumoniae strain or its wild-type (WT) progenitor were compared. Ceftazidime at 12.5 or 50 mg/kg of body weight twice daily (b.i.d.) was effective (50% or 100% rat survival) in pneumonia caused by the WT isolate but unsuccessful (100% rat mortality) in pneumonia caused by the ESBL-positive variant. In contrast, tigecycline at 6.25, 12.5, or 25 mg/kg b.i.d. showed dosage-dependent efficacy up to 100% rat survival irrespective of the ESBL character of the infecting organism.

Metabolic response to Klebsiella pneumoniae infection in an experimental rat model.

Bacteremia, the presence of viable bacteria in the blood stream, is often associated with several clinical conditions. Bacteremia can lead to multiple organ failure if managed incorrectly, which makes providing suitable nutritional support vital for reducing bacteremia-associated mortality. In order to provide such information, we investigated the metabolic consequences of a Klebsiella pneumoniae (K. pneumoniae) infection in vivo by employing a combination of (1)H nuclear magnetic resonance spectroscopy and multivariate data analysis. K. pneumoniae was intravenously infused in rats; urine and plasma samples were collected at different time intervals. We found that K. pneumoniae-induced bacteremia stimulated glycolysis and the tricarboxylic acid cycle and also promoted oxidation of fatty acids and creatine phosphate to facilitate the energy-demanding host response. In addition, K. pneumoniae bacteremia also induced anti-endotoxin, anti-inflammatory and anti-oxidization responses in the host. Furthermore, bacteremia could cause a disturbance in the gut microbiotal functions as suggested by alterations in a range of amines and bacteria-host co-metabolites. Our results suggest that supplementation with glucose and a high-fat and choline-rich diet could ameliorate the burdens associated with bacteremia. Our research provides underlying pathological processes of bacteremia and a better understanding of the clinical and biochemical manifestations of bacteremia.

[Protection and mechanism of Fagopyrum cymosum on lung injury in rats with Klebsiella pneumonia].

OBJECTIVE: To study the mechanism of protective effect of Fagopyrum cymosum on lung injury induced by Klebsiella pneumonia in rats. METHODS: The model of rats with Klebsiella pneumonia was established. The male SD rats were randomly divided into control group, model group, Fagopyrum cymosum (6, 3, 1.5 g/kg) three groups, levofloxacin (25 mg/kg) group. The pathological change of lung was observed. The content of IL-1beta, IL-6, IL-8, TNF-alpha, ICAM-1, INF-gamma in serum were measured by radioimmunoassay and Elisa. TNF-alpha, ICAM-1, NF-kappaB p65 protein expressions were measured by immunohistochemistry. MIP-2mRNA expression was detected by in situ hybridization. RESULTS: The rats of model group had obvious lung injury, but those of Fagopyrum cymosum and levofloxacin groups had less injury. The contents of IL-1beta, IL-6, IL-,8, TNF-alpha, ICAM-1 and INF-gamma in serum and the expressions of TNF-a, ICAM-1, NF-kappaB p65 and MIP--2mRNA of model group were significantly higher than those of the control group (P < 0.05 or P < 0.01), while the indexes of Fagopyrum cymosum and levofloxacin groups were significantly lower than those of model group (P < 0.05 or P < 0.01). CONCLUSION: The lung injury induced by Klebsiella pneumonia is related to TNF-alpha, ICAM-1, NF-kappaB p65 and MIP-2mRNA. To decrease the excessive expression of TNF-alpha, ICAM-1, NF-kappaB p65 and MIP-2mRNA might be the main mechanism of protective effect of Fagopyrum cymosum on lung injury.

Bloodstream infections due to extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae: risk factors for mortality and treatment outcome, with special emphasis on antimicrobial therapy.

This study was conducted to evaluate risk factors for mortality and treatment outcome of bloodstream infections due to extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae (ESBL-EK). ESBL production in stored K. pneumoniae and E. coli blood isolates from Jan 1998 to Dec 2002 was phenotypically determined according to NCCLS guidelines and/or the double-disk synergy test. A total of 133 patients with ESBL-EK bacteremia, including 66 patients with ESBL-producing K. pneumoniae and 67 with ESBL-producing E. coli, were enrolled. The overall 30-day mortality rate was 25.6% (34 of 133). Independent risk factors for mortality were severe sepsis, peritonitis, neutropenia, increasing Acute Physiology and Chronic Health Evaluation II score, and administration of broad-spectrum cephalosporin as definitive antimicrobial therapy (P < 0.05 for each of these risk factors). In 117 of the 133 patients, excluding 16 patients who died within 3 days after blood culture sample acquisition, the 30-day mortality rates according to definitive antibiotics were as follows: carbapenem, 12.9% (8 of 62); ciprofloxacin, 10.3% (3 of 29); and others, such as cephalosporin or an aminoglycoside, 26.9% (7 of 26). When patients who received appropriate definitive antibiotics, such as carbapenem or ciprofloxacin, were evaluated, mortality in patients receiving inappropriate empirical antimicrobial therapy was found not to be significantly higher than mortality in those receiving appropriate empirical antimicrobial therapy (18.9 versus 15.5%; P = 0.666). Carbapenem and ciprofloxacin were the most effective antibiotics in antimicrobial therapy for ESBL-EK bacteremia. A delay in appropriate definitive antimicrobial therapy was not associated with higher mortality if antimicrobial therapy was adjusted appropriately according to the susceptibility results. Our data suggest that more prudent use of carbapenem as empirical antibiotic may be reasonable.

Improved efficacy of ciprofloxacin administered in polyethylene glycol-coated liposomes for treatment of Klebsiella pneumoniae pneumonia in rats.

Animal and clinical data show that high ratios of the area under the concentration-time curve and the peak concentration in blood to the MIC of fluoroquinolones for a given pathogen are associated with a favorable outcome. The present study investigated whether improvement of the therapeutic potential of ciprofloxacin could be achieved by encapsulation in polyethylene glycol (PEG)-coated long-circulating sustained-release liposomes. In a rat model of unilateral Klebsiella pneumoniae pneumonia (MIC = 0.1 microg/ml), antibiotic was administered at 12- or 24-h intervals at twofold-increasing doses. A treatment period of 3 days was started 24 h after inoculation of the left lung, when the bacterial count had increased 1,000-fold and some rats had positive blood cultures. The infection was fatal within 5 days in untreated rats. Administration of ciprofloxacin in the liposomal form resulted in delayed ciprofloxacin clearance and increased and prolonged ciprofloxacin concentrations in blood and tissues. The ED(50) (dosage that results in 50% survival) of liposomal ciprofloxacin was 3.3 mg/kg of body weight/day given once daily, and that of free ciprofloxacin was 18.9 mg/kg/day once daily or 5.1 mg/kg/day twice daily. The ED(90) of liposomal ciprofloxacin was 15.0 mg/kg/day once daily compared with 36.0 mg/kg/day twice daily for free ciprofloxacin; 90% survival could not be achieved with free ciprofloxacin given once daily. In summary, the therapeutic efficacy of liposomal ciprofloxacin was superior to that of ciprofloxacin in the free form. PEG-coated liposomal ciprofloxacin was well tolerated in relatively high doses, permitting once daily administration with relatively low ciprofloxacin clearance and without compromising therapeutic efficacy.

Prevention of bacterial infection and LPS-induced lethality by interleukin-1 alpha in mice.

In order to make clear the characteristic biological properties of IL-1 alpha, its protective capabilities on bacteria-induced and LPS-induced lethality were compared with other BRMs in BALB/c mice. Pretreatment with IL-1 alpha (i.p., s.c.) or OK-432 (i.p.), could protect mice from the lethality of a K. pneumoniae infection (i.p.), and pretreatment with IL-1 alpha or TNF alpha could protect mice from LPS (i.p.) lethality. IL-1 alpha could protect mice from both bacteria- and LPS-induced lethality. There was no difference in serum corticosterone levels after the LPS injection between the IL-1 alpha pretreated and untreated groups. However, a more rapid clearance of LPS from the serum and a stronger LPS-neutralizing activity in serum were observed with the LAL assay in IL-1 alpha pretreated mice than in untreated mice. The enhanced LPS-clearance was suggested to be partly responsible for the increased protection against LPS-lethality. IL-1 alpha was indicated to be a unique BRM and to become a useful tool for the prevention of life-threatening bacterial infections and subsequent endotoxin shock.

Influence of dose frequency on the therapeutic efficacies of ciprofloxacin and ceftazidime in experimental Klebsiella pneumoniae pneumonia and septicemia in relation to their bactericidal activities in vitro.

The antibacterial activities of ciprofloxacin versus ceftazidime against Klebsiella pneumoniae in vitro and in vivo were compared. Although there was only a minor difference in MBC values between both drugs ciprofloxacin demonstrated a high and dose-dependent bacterial killing rate in vitro and in lungs of leukopenic rats in contrast to the more time-dependent bactericidal activity of ceftazidime. After treatment of a K.pneumoniae pneumonia and septicemia the efficacy of ciprofloxacin was only slightly influenced by the mode of administration, either at 6-h intervals or continuously, whereas ceftazidime was far more effective after continuous administration. This resulted in a superior efficacy of ciprofloxacin after intermittent treatment as compared to ceftazidime, whereas ceftazidime was more effective after continuous administration as compared to ciprofloxacin. Also ciprofloxacin proved to be bactericidal against bacteria that were not actively growing, both in vitro and in vivo, whereas ceftazidime was not.

Continuous versus intermittent administration of ceftazidime in experimental Klebsiella pneumoniae pneumonia in normal and leukopenic rats.

Experimental Klebsiella pneumoniae pneumonia was used to study the influence of cyclophosphamide-induced leukopenia on the relative therapeutic efficacy of continuous and intermittent (6-h intervals) administration of ceftazidime. The antimicrobial response was evaluated with respect to the calculated daily dose that protected 50% of the animals from death (PD50) until 16 days after the termination of a 4-day treatment. When ceftazidime was administered intermittently to leukopenic rats, the PD50 was 24.37 mg/kg per day, 70 times (P less than 0.001) the PD50 of 0.35 mg/kg per day for normal rats. Continuous administration of ceftazidime to leukopenic rats resulted in a PD50 of 1.52 mg/kg per day, four times (P less than 0.001) the PD50 of 0.36 mg/kg per day for normal rats. Continuous administration of ceftazidime in daily doses that protected 100% of normal and leukopenic rats from death resulted in serum levels of 0.06 and 0.38 micrograms/ml, respectively, whereas the MIC for the infecting K. pneumoniae strain was 0.2 micrograms of ceftazidime per ml. The effect of the duration of ceftazidime treatment by continuous infusion on the therapeutic efficacy in relation to the persistence of leukopenia was then investigated in leukopenic rats. The administration of 3.75 mg of ceftazidime/kg per day for 4 days protected all leukopenic rats from death, provided the circulating leukocytes returned at the end of antibiotic treatment. When leukopenia persisted for 8 days this ceftazidime treatment schedule resulted in the mortality of rats (P less than 0.05). However, when ceftazidime treatment was continued for 8 days, until the return of the leukocytes, there was no significant mortality (P greater than 0.05).

Relevance of serum protein binding of cefoxitin and cefazolin to their activities against Klebsiella pneumoniae pneumonia in rats.

An experimental Klebsiella pneumoniae pneumonia in rats was used to study the effect of protein binding of cefoxitin and cefazolin on their therapeutic activity. Both cephalosporins were similar with respect to their antimicrobial activity against the K. pneumoniae in vitro, but they differed in their degree of protein binding, being 34% for cefoxitin and 89 to 93% for cefazolin in uninfected rats and 24 and 71 to 83%, respectively, in infected rats. Various doses of these agents were administered by continuous infusion, which started 5 h after bacterial inoculation and continued for 65 h. Antimicrobial response was evaluated with respect to the numbers of bacteria recovered from lung and blood at the end of treatment. An inhibitory effect of protein binding on the in vivo antimicrobial activity was demonstrated. Cefoxitin was therapeutically effective at a constant plasma level that reached the MIC. To obtain a similar effect with cefazolin the plasma level of that drug had to be increased to a concentration more than three times the MIC.

A randomized study of tobramycin plus ticarcillin, tobramycin plus cephalothin and ticarcillin, or tobramycin plus mezlocillin in the treatment of infection in neutropenic patients with malignancies.

Two hundred twenty-five patients with 358 febrile episodes were treated with tobramycin and ticarcillin (TT), tobramycin and mezlocillin (TM), or tobramycin, ticarcillin and cephalothin (TTC). There were no statistically significant differences in the response rates for patients who were proven to have infection (67% with TT, 69% with TTC and 53% with TM). Patients were more often cured of their infection if their neutrophil count rose during therapy. In this study, the addition of cephalothin to TT did not increase the frequency of azotemia (10% and 12%, respectively). Although mezlocillin has a broader spectrum of activity in vitro than ticarcillin, it was not more efficacious when combined with tobramycin than ticarcillin plus tobramycin for the treatment of infections in neutropenic patients.