scholarly journals In Vitro Resistance Selection in Shigella flexneri by Azithromycin, Ceftriaxone, Ciprofloxacin, Levofloxacin, and Moxifloxacin

2017 ◽  
Vol 61 (7) ◽  
Author(s):  
George P. Allen ◽  
Kayla A. Harris

ABSTRACT Shigella flexneri continues to be a major cause of diarrhea-associated illness, and increasing resistance to first-line antimicrobials complicates the treatment of infections caused by this pathogen. We investigated the pharmacodynamics of current antimicrobial treatments for shigellosis to determine the likelihood of resistance promotion with continued global antimicrobial use. The mutant prevention concentration (MPC) and mutant selection window (MSW) were determined for azithromycin, ceftriaxone, ciprofloxacin, levofloxacin, and moxifloxacin against a wild-type strain of S. flexneri (ATCC 12022) and an isogenic gyrA mutant (m-12022). Time-kill assays were performed to determine antimicrobial killing. Concentrations of approved doses of ciprofloxacin, levofloxacin, and moxifloxacin are predicted to surpass the MPC for a majority of the dosage interval against ATCC 12022. However, against m-12022, concentrations of all fluoroquinolones are predicted to fall below the MPC and remain in the MSW for a majority of the dosage interval. Concentrations of ceftriaxone fall within the MSW for the majority of the dosage interval for both strains. All agents other than azithromycin displayed bactericidal activity in time-kill assays. Results of pharmacodynamic analyses suggest that all tested fluoroquinolones would achieve a favorable area under the concentration-time curve (AUC)/MPC ratio for ATCC 12022 and would restrict selective enrichment of mutants but that mutant selection in m-12022 would be likely if ciprofloxacin were used. Based on pharmacodynamic analyses, azithromycin and ceftriaxone are predicted to promote mutant selection in both strains. Confirmation of these findings and examination of novel treatment regimens using in vivo studies are warranted.

2019 ◽  
Vol 63 (10) ◽  
Author(s):  
Seong Eun Kim ◽  
Hee Kyung Kim ◽  
Su-Mi Choi ◽  
Yohan Yu ◽  
Uh Jin Kim ◽  
...  

ABSTRACT The mortality rate associated with Vibrio vulnificus sepsis remains high. An in vitro time-kill assay revealed synergism between tigecycline and ciprofloxacin. The survival rate was significantly higher in mice treated with tigecycline plus ciprofloxacin than in mice treated with cefotaxime plus minocycline. Thus, combination treatment with tigecycline-ciprofloxacin may be an effective novel antibiotic regimen for V. vulnificus sepsis.


2012 ◽  
Vol 56 (12) ◽  
pp. 6291-6297 ◽  
Author(s):  
Azzam Saleh-Mghir ◽  
Oana Dumitrescu ◽  
Aurélien Dinh ◽  
Yassine Boutrad ◽  
Laurent Massias ◽  
...  

ABSTRACTCommunity-associated methicillin-resistantStaphylococcus aureus(CA-MRSA) can cause osteomyelitis with severe sepsis and/or local complications in which a Panton-Valentine leukocidin (PVL) role is suspected.In vitrosub-MIC antibiotic effects on growth and PVL production by 11 PVL+MRSA strains, including the major CA-MRSA clones (USA300, including the LAC strain; USA400; and USA1000), and 11 PVL+methicillin-susceptibleS. aureus(MSSA) strains were tested in microplate culture. Time-kill analyses with ceftobiprole at its MIC were also run with LAC. Efficacies of ceftobiprole (40 mg/kg of body weight subcutaneously [s.c.] four times a day [q.i.d.]) or vancomycin (60 mg/kg intramuscularly [i.m.] twice a day [b.i.d.]) alone or combined with rifampin (10 mg/kg b.i.d.) against rabbit CA-MRSA osteomyelitis, induced by tibial injection of 3.4 × 107CFU of LAC, were compared. Treatment, started 14 days postinoculation, lasted 14 days.In vitro, 6/11 strains cultured with sub-MICs of ceftobiprole produced 1.6- to 4.8-fold more PVL than did the controls, with no link to specific clones. Rifampin decreased PVL production by all tested strains. In time-kill analyses at the LAC MIC (0.75 mg/liter), PVL production rose transiently at 6 and 8 h and then declined 2-fold at 16 h, concomitant with a 2-log10-CFU-count decrease.In vivo, the mean log10CFU/g of bone for ceftobiprole (1.44 ± 0.40) was significantly lower than that for vancomycin (2.37 ± 1.22) (P= 0.034), with 7/10 versus 5/11 bones sterilized, respectively. Combination with rifampin enhanced ceftobiprole (1.16 ± 0.04 CFU/g of bone [P= 0.056], 11/11 sterile bones) and vancomycin (1.23 ± 0.06 CFU/g [P= 0.011], 11/11 sterile bones) efficacies. Ceftobiprole bactericidal activity and the rifampin anti-PVL effect could play a role in these findings, which should be of interest for treating CA-MRSA osteomyelitis.


2016 ◽  
Vol 60 (5) ◽  
pp. 3001-3006 ◽  
Author(s):  
Akihiro Morinaka ◽  
Yuko Tsutsumi ◽  
Keiko Yamada ◽  
Yoshihiro Takayama ◽  
Shiro Sakakibara ◽  
...  

ABSTRACTGram-negative bacteria are evolving to produce β-lactamases of increasing diversity that challenge antimicrobial chemotherapy. OP0595 is a new diazabicyclooctane serine β-lactamase inhibitor which acts also as an antibiotic and as a β-lactamase-independent β-lactam “enhancer” againstEnterobacteriaceae. Here we determined the optimal concentration of OP0595 in combination with piperacillin, cefepime, and meropenem, in addition to the antibacterial activity of OP0595 alone and in combination with cefepime, inin vitrotime-kill studies and anin vivoinfection model against five strains of CTX-M-15-positiveEscherichia coliand five strains of KPC-positiveKlebsiella pneumoniae. An OP0595 concentration of 4 μg/ml was found to be sufficient for an effective combination with all three β-lactam agents. In bothin vitrotime-kill studies and anin vivomodel of infection, cefepime-OP0595 showed stronger efficacy than cefepime alone against all β-lactamase-positive strains tested, whereas OP0595 alone showed weaker or no efficacy. Taken together, these data indicate that combinational use of OP0595 and a β-lactam agent is important to exert the antimicrobial functions of OP0595.


2020 ◽  
Vol 64 (8) ◽  
Author(s):  
Shaoyan Zhang ◽  
Yuzhen Zou ◽  
Qi Guo ◽  
Jianhui Chen ◽  
Liyun Xu ◽  
...  

ABSTRACT Therapeutic options for Mycobacterium abscessus infections are extremely limited. New or repurposed drugs are needed. The anti-M. abscessus activity of AR-12 (OSU-03012), reported to express broad-spectrum antimicrobial effects, was investigated in vitro and in vivo. Antimicrobial susceptibility testing was performed on 194 clinical isolates. Minimum bactericidal concentration and time-kill kinetics assays were conducted to distinguish the bactericidal versus bacteriostatic activity of AR-12. Synergy between AR-12 and five clinically important antibiotics was determined using a checkerboard synergy assay. The activity of AR-12 against intracellular M. abscessus residing within macrophage was also evaluated. Finally, the potency of AR-12 in vivo was determined in a neutropenic mouse model that mimics pulmonary M. abscessus infection. AR-12 exhibited high anti-M. abscessus activity in vitro, with an MIC50 of 4 mg/liter (8.7 μM) and an MIC90 of 8 mg/liter (17.4 μM) for both subsp. abscessus and subsp. massiliense. AR-12 and amikacin exhibited comparable bactericidal activity against extracellular M. abscessus in culture. AR-12, however, exhibited significantly greater intracellular antibacterial activity than amikacin and caused a significant reduction in the bacterial load in the lungs of neutropenic mice infected with M. abscessus. No antagonism between AR-12 and clarithromycin, amikacin, imipenem, cefoxitin, or tigecycline was evident. In conclusion, AR-12 is active against M. abscessus in vitro and in vivo and does not antagonize the most frequently used anti-M. abscessus drugs. As such, AR-12 is a potential candidate to include in novel strategies to treat M. abscessus infections.


2020 ◽  
Vol 64 (6) ◽  
Author(s):  
Maria-Ioanna Beredaki ◽  
Panagiota-Christina Georgiou ◽  
Maria Siopi ◽  
Lamprini Kanioura ◽  
David Andes ◽  
...  

ABSTRACT CLSI and EUCAST susceptibility breakpoints for voriconazole and Candida albicans differ by one dilution (≤0.125 and ≤0.06 mg/liter, respectively) whereas the epidemiological cutoff values for EUCAST (ECOFF) and CLSI (ECV) are the same (0.03 mg/liter). We therefore determined the pharmacokinetic/pharmacodynamic (PK/PD) breakpoints of voriconazole against C. albicans for both methodologies with an in vitro PK/PD model, which was validated using existing animal PK/PD data. Four clinical wild-type and non-wild-type C. albicans isolates (voriconazole MICs, 0.008 to 0.125 mg/liter) were tested in an in vitro PK/PD model. For validation purposes, mouse PK were simulated and in vitro PD were compared with in vivo outcomes. Human PK were simulated, and the exposure-effect relationship area under the concentration-time curve for the free, unbound fraction of a drug from 0 to 24 h (fAUC0–24)/MIC was described for EUCAST and CLSI 24/48-h methods. PK/PD breakpoints were determined using the fAUC0–24/MIC associated with half-maximal activity (EI50) and Monte Carlo simulation analysis. The in vitro 24-h PD EI50 values of voriconazole against C. albicans were 2.5 to 5 (1.5 to 17) fAUC/MIC. However, the 72-h PD were higher at 133 (51 to 347) fAUC/MIC for EUCAST and 94 (35 to 252) fAUC/MIC for CLSI. The mean (95% confidence interval) probability of target attainment (PTA) was 100% (95 to 100%), 97% (72 to 100%), 83% (35 to 99%), and 49% (8 to 91%) for EUCAST and 100% (97 to 100%), 99% (85 to 100%), 91% (52 to 100%), and 68% (17 to 96%) for CLSI for MICs of 0.03, 0.06, 0.125, and 0.25 mg/liter, respectively. Significantly, >95% PTA values were found for EUCAST/CLSI MICs of ≤0.03 mg/liter. For MICs of 0.06 to 0.125 mg/liter, trough levels 1 to 4 mg/liter would be required to attain the PK/PD target. A PK/PD breakpoint of C. albicans voriconazole at the ECOFF/ECV of 0.03 mg/liter was determined for both the EUCAST and CLSI methods, indicating the need for breakpoint harmonization for the reference methodologies.


2011 ◽  
Vol 55 (7) ◽  
pp. 3453-3460 ◽  
Author(s):  
Arnold Louie ◽  
Weiguo Liu ◽  
Robert Kulawy ◽  
G. L. Drusano

ABSTRACTTorezolid phosphate (TR-701) is the phosphate monoester prodrug of the oxazolidinone TR-700 which demonstrates potentin vitroactivity against Gram-positive bacteria, including methicillin-susceptibleStaphylococcus aureus(MSSA) and methicillin-resistantS. aureus(MRSA). The pharmacodynamics of TR-701 or TR-700 (TR-701/700) againstS. aureusis incompletely defined. Single-dose pharmacokinetic studies were conducted in mice for TR-701/700. Forty-eight-hour dose range and 24-hour dose fractionation studies were conducted in a neutropenic mouse thigh model ofS. aureusinfection using MRSA ATCC 33591 to identify the dose and schedule of administration of TR-701/700 that was linked with optimized antimicrobial effect. Additional dose range studies compared the efficacies of TR-701/700 and linezolid for one MSSA strain and one community-associated MRSA strain. In dose range studies, TR-701/700 was equally bactericidal against MSSA and MRSA. Mean doses of 37.6 and 66.9 mg/kg of body weight/day of TR-701/700 resulted in stasis and 1 log CFU/g decreases in bacterial densities, respectively, at 24 h, and mean doses of 35.3, 46.6, and 71.1 mg/kg/day resulted in stasis and 1 and 2 log CFU/g reductions, respectively, at 48 h. Linezolid administered at doses as high as 150 mg/kg/day did not achieve stasis at either time point. Dose fractionation studies demonstrated that the area under the concentration-time curve over 24 h in the steady state divided by the MIC (AUC/MIC ratio) was the pharmacodynamic index for TR-701/700 that was linked with efficacy. TR-701/700 was highly active against MSSA and MRSA,in vivo, and was substantially more efficacious than linezolid, although linezolid's top exposure has half the human exposure. Dose fractionation studies showed that AUC/MIC was the pharmacodynamic index linked with efficacy, indicating that once-daily dosing in humans is feasible.


2012 ◽  
Vol 56 (12) ◽  
pp. 6192-6200 ◽  
Author(s):  
Shrenik Mehta ◽  
Christopher Singh ◽  
Konrad B. Plata ◽  
Palas K. Chanda ◽  
Arundhati Paul ◽  
...  

ABSTRACTMethicillin-resistantStaphylococcus aureus(MRSA) has emerged to be one of the most important pathogens both in health care and in community-onset infections. Daptomycin (DAP) is a cyclic anionic lipopeptide recommended for treatment of skin infections, bacteremia, and right-sided endocarditis caused by MRSA. Resistance to DAP (DAPr) has been reported in MRSA and is mostly accompanied by a parallel decrease in oxacillin resistance, a process known as the “seesaw effect.” Our study provides evidence that the seesaw effect applies to other β-lactams and carbapenems of clinical use, including nafcillin (NAF), cefotaxime (CTX), amoxicillin-clavulanic (AMC), and imipenem (IMP), in heterogeneous DAPrMRSA strains but not in MRSA strains expressing homogeneous β-lactam resistance. The antibacterial efficacy of DAP in combination with β-lactams was evaluated in isogenic DAP-susceptible (DAPs)/DaprMRSA strains originally obtained from patients that failed DAP monotherapy. Bothin vitro(MIC, synergy-kill curve) andin vivo(wax worm model) approaches were used. In these models, DAP and a β-lactam proved to be highly synergistic against both heterogeneous and homogeneous clinical DAPrMRSA strains. Mechanistically, β-lactams induced a reduction in the cell net positive surface charge, reverting the increased repulsion provoked by DAP alone, an effect that may favor the binding of DAP to the cell surface. The ease ofin vitromutant selection was observed when DAPsMRSA strains were exposed to DAP. Importantly, the combination of DAP and a β-lactam prevented the selection of DAPrvariants. In summary, our data show that the DAP–β-lactam combination may significantly enhance both thein vitroandin vivoefficacy of anti-MRSA therapeutic options against DAPrMRSA infections and represent an option in preventing DAPrselection in persistent or refractory MRSA infections.


2011 ◽  
Vol 55 (6) ◽  
pp. 2755-2759 ◽  
Author(s):  
Hung-Jen Tang ◽  
Wen-Chien Ko ◽  
Chi-Chung Chen ◽  
Po-Lin Chen ◽  
Han Siong Toh ◽  
...  

ABSTRACTSalmonellais an important, worldwide food-borne pathogen. Resistance to fluoroquinolones and cephalosporins has been increasingly reported, and new therapeutic agents are desperately needed. In this study, we evaluated thein vitroantimicrobial susceptibility of clinical nontyphoidalSalmonellaisolates to tigecycline. Antibacterial activity of tigecycline, ceftriaxone, and ciprofloxacin were investigated by time-kill studies and the murine peritonitis model. The MIC50/MIC90values of tigecycline, ceftriaxone, and ciprofloxacin against 76Salmonellaisolates were 0.25/0.5, 1/8, and 0.125/0.5 μg/ml, respectively. The intracellular inhibitory activity of tigecycline at 0.5 μg/ml (1× MIC) againstSalmonellaisolates in human peripheral blood mononuclear cells was sustained for 24 h. In a mouse peritonitis model, tigecycline reduced the extracellular and intracellular bacterial counts from 107CFU/ml and 105CFU/ml, respectively, to an undetectable level within 96 h. The results were similar to those obtained with ceftriaxone. The survival rate of mice exposed to tigecycline after being infected by an inoculum of 1 × 105CFU was 80%, and that of mice exposed to ceftriaxone was 100%. When the inoculum was increased to 1.3 × 106CFU, the survival rate of mice treated by tigecycline was 20%, and that of mice exposed to ceftriaxone was 0% (P= 0.2). When a ceftriaxone- and ciprofloxacin-resistant but tigecycline-susceptible isolate was tested, mice treated by tigecycline had a higher survival rate than those treated by ceftriaxone (15/20 [75%] versus 6/20 [30%];P= 0.011). Our results suggest that tigecycline is at least as effective as ceftriaxone for murineSalmonellainfections and warrants further clinical investigations to delineate its potential against humanSalmonellainfections.


2015 ◽  
Vol 59 (6) ◽  
pp. 3252-3256 ◽  
Author(s):  
Liana C. Chan ◽  
Li Basuino ◽  
Etyene C. Dip ◽  
Henry F. Chambers

ABSTRACTTedizolid, the active component of the prodrug tedizolid phosphate, is a novel oxazolidinone that is approximately 4 times more active by weight than linezolid againstStaphylococcus aureusin vitro. Thein vivoefficacy of tedizolid phosphate (15 mg/kg body weight intravenous [i.v.] twice a day [b.i.d.]) was compared to those of vancomycin (30 mg/kg i.v. b.i.d.) and daptomycin (18 mg/kg i.v. once a day [q.d.]) in a rabbit model of aortic valve endocarditis (AVE) caused by methicillin-resistantS. aureusstrain COL (infection inoculum of 107CFU). Median vegetation titers of daptomycin-treated rabbits were significantly lower than those of rabbits treated with tedizolid phosphate (15 mg/kg b.i.d.) (P= 0.016), whereas titers for vancomycin-treated compared to tedizolid-treated rabbits were not different (P= 0.984). The numbers of organisms in spleen and kidney tissues were similar for all treatment groups. A dose-ranging experiment was performed with tedizolid phosphate (2, 4, and 8 mg/kg b.i.d.) compared to vancomycin (30 mg/kg b.i.d.), using a higher infecting inoculum (108CFU) to determine the lowest efficacious dose of tedizolid phosphate. Tedizolid phosphate (2 mg/kg) (equivalent to 60% of the area under the concentration-time curve from 0 to 24 h (AUC0–24) for the human 200-mg dose approved by the U.S. Food and Drug Administration) was not efficacious. Tedizolid phosphate at 4 mg/kg (equivalent to 75% of the AUC0–24for the human 400-mg dose) and 8 mg/kg produced lower vegetation titers than the control, but neither was as efficacious as vancomycin.


2019 ◽  
Vol 63 (4) ◽  
Author(s):  
S. S. Bhagwat ◽  
H. Periasamy ◽  
S. S. Takalkar ◽  
S. R. Palwe ◽  
H. N. Khande ◽  
...  

ABSTRACTWCK 5222 is a combination of cefepime and the high-affinity PBP2-binding β-lactam enhancer zidebactam. The cefepime-zidebactam combination is active against multidrug-resistant Gram-negative bacteria, including carbapenemase-expressingAcinetobacter baumannii. The mechanism of action of the combination involves concurrent multiple penicillin binding protein inhibition, leading to the enhanced bactericidal action of cefepime. The aim of the present study was to assess the impact of the zidebactam-mediated enhancedin vitrobactericidal action in modulating the percentage of the time that the free drug concentration remains above the MIC (percentfT>MIC) for cefepime required for thein vivokilling ofA. baumannii. Cefepime and cefepime-zidebactam MICs were comparable and ranged from 2 to 16 mg/liter for theA. baumanniistrains (n = 5) employed in the study. Time-kill studies revealed the improved killing of these strains by the cefepime-zidebactam combination compared to that by the constituents alone. Employing a neutropenic mouse lung infection model, exposure-response analyses for all theA. baumanniistrains showed that the cefepimefT>MIC required for 1-log10kill was 38.9%. In the presence of a noneffective dose of zidebactam, the cefepimefT>MIC requirement dropped significantly to 15.5%, but it still rendered a 1-log10kill effect. Thus, zidebactam mediated the improvement in cefepime’s bactericidal effect observed in time-kill studies, manifestedin vivothrough the lowering of cefepime’s pharmacodynamic requirement. This is a first-ever study demonstrating a β-lactam enhancer role of zidebactam that helps augment thein vivoactivity of cefepime by reducing the magnitude of its pharmacodynamically relevant exposures againstA. baumannii.


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