Emergence of daptomycin resistance in daptomycin-naïve rabbits with methicillin-resistant Staphylococcus aureus prosthetic joint infection is associated with resistance to host defense cationic peptides and mprF polymorphisms.

BackgroundPrevious studies of both clinically-derived and in vitro passage-derived daptomycin-resistant (DAP-R) Staphylococcus aureus strains demonstrated the coincident emergence of increased DAP MICs and resistance to host defense cationic peptides (HDP-R).MethodsIn the present investigation, we studied a parental DAP-susceptible (DAP-S) methicillin-resistant Staphylococcus aureus (MRSA) strain and three isogenic variants with increased DAP MICs which were isolated from both DAP-treated and DAP-untreated rabbits with prosthetic joint infections. These strains were compared for: in vitro susceptibility to distinct HDPs differing in size, structure, and origin; i.e.; thrombin-induced platelet microbicidal proteins [tPMPs] and human neutrophil peptide-1 [hNP-1]; cell membrane (CM) phospholipid and fatty acid content; CM order; envelope surface charge; cell wall thickness; and mprF single nucleotide polymorphisms (SNPs) and expression profiles.ResultsIn comparison with the parental strain, both DAP-exposed and DAP-naive strains exhibited: (i) significantly reduced susceptibility to each HDP (P<0.05); (ii) thicker cell walls (P<0.05); (iii) increased synthesis of CM lysyl-phosphatidylglycerol (L-PG); (iv) reduced content of CM phosphatidylglycerol (PG); and (v) SNPs within the mprF locus No significant differences were observed between parental or variant strains in outer CM content of L-PG, CM fluidity, CM fatty acid contents, surface charge, mprF expression profiles or MprF protein content. An isolate which underwent identical in vivo passage, but without evolving increased DAP MICs, retained parental phenotypes and genotype.ConclusionsTHESE RESULTS SUGGEST: i) DAP MIC increases may occur in the absence of DAP exposures in vivo and may be triggered by organism exposure to endogenous HDPs: and ii) gain-in-function SNPs in mprF may contribute to such HDP-DAP cross-resistance phenotypes, although the mechanism of this relationship remains to be defined

Efficacy of colistin alone and in various combinations for the treatment of experimental osteomyelitis due to carbapenemase-producing Klebsiella pneumoniae

Objectives: In a new experimental model of carbapenemase-producing Klebsiella pneumoniae osteomyelitis we evaluated the efficacy of colistin alone and in various combinations and examined the emergence of colistin-resistant strains and cross- resistance to host defence peptides (HDPs).Methods: KPC-99YC is a clinical strain with intermediate susceptibility to meropenem (MIC = 4 mg/L) and full susceptibility to gentamicin, colistin and tigecycline (MICs = 1 mg/L) and fosfomycin (MIC = 32 mg/L). Time–kill curves were performed at 4× MIC. Osteomyelitis was induced in rabbits by tibial injection of 2 × 108 cfu. Treatment started 14 days later for 7 days in seven groups: (i) control; (ii) colistin; (iii) colistin + gentamicin; (iv) colistin + tigecycline; (v) colistin + meropenem; (vi) colistin + meropenem + gentamicin; and (vii) colistin +  fosfomycin.Results: In vitro, colistin was rapidly bactericidal, but regrowth occurred after 9 h. Combinations of colistin with meropenem or fosfomycin were synergistic, whereas combination with tigecycline was antagonistic. In vivo, colistin alone was not effective. Combinations of colistin with meropenem or fosfomycin were bactericidal (P  < 0.001) and the addition of gentamicin enhanced the efficacy of colistin + meropenem (P = 0.025). Tigecycline reduced the efficacy of colistin (P = 0.007). Colistin-resistant strains emerged in all groups except colistin + fosfomycin and two strains showed cross-resistance to HDP LL-37.Conclusions: In this model, combinations of colistin plus meropenem, with or without gentamicin, or colistin plus fosfomycin were the only effective therapies. The combination of colistin and tigecycline should be administered with caution, as it may be antagonistic in vitro and in vivo

A Novel Antibacterial Compound Decreases MRSA Biofilm Formation Without the Use of Antibiotics in A Murine Model

Despite significant advancements in material science, surgical site infection (SSI) rates remain high and prevention is key. This study aimed to demonstrate the in-vivo safety and antibacterial efficacy of titanium implants treated with a novel broad-spectrum biocidal compound (DBG21) against methicillin-resistant Staphylococcus aureus (MRSA). Titanium (Ti) discs were covalently bound with DBG21. Untreated Ti discs were used as controls. All discs were implanted either untreated for 44 control mice or DBG21-treated for 44 treated mice. After implantation, 1x107 colony forming units (CFU) of MRSA were injected into the operating site. Mice were sacrificed at day 7 and 14 to determine the number of adherent bacteria (biofilm) on implants and in the peri-implant surrounding tissues. Systemic and local toxicity were assessed. At both 7 and 14 days, DBG21-treated implants yielded a significant decrease in MRSA biofilm (3.6 median log10 CFU (99.97%) reduction (p<0.001) and 1.9 median log10 CFU (98.7%) reduction (p=0.037), respectively) and peri-implant surrounding tissues (2.7 median log10 CFU/g (99.8%) reduction (p<0.001) and 5.6 median log10 CFU/g (99.9997%) reduction (p<0.001), respectively). There were no significant differences between control and treated mice in terms of systemic and local toxicity. DBG-21 demonstrated a significant decrease in the number of biofilm bacteria without associated toxicity in a small animal implant model of SSI. Preventing biofilm formation has been recognized as a key element of preventing implant-related infections

Bactericidal Activity of the Combination of Levofloxacin with Rifampin in Experimental Prosthetic Knee Infection in Rabbits Due to Methicillin-Susceptible Staphylococcus aureus▿

The combination of levofloxacin and rifampin has been recommended for the treatment of staphylococcal prosthetic infection. In a rabbit model of prosthetic knee infection due to a susceptible clinical strain of Staphylococcus aureus, the combination of levofloxacin and rifampin was bactericidal, significantly reduced bacterial titers in bone compared with levels for rifampin and controls (P < 0.05), sterilized 6 of 12 animals, and prevented the selection of resistant mutants that was observed with rifampin alone, validating clinical recommendations

Teicoplanin-Containing Cement Spacers for Treatment of Experimental Staphylococcus aureus Joint Prosthesis Infection

Using a rabbit model of methicillin-resistant Staphylococcus aureus knee-prosthesis infection, we studied the efficacy of teicoplanin cement alone or in combination with systemic intramuscular (i.m.) injections of teicoplanin. Seven days after infection, surgical debridement and removal of the infected prostheses were performed, and five rabbits were randomly assigned to one of five different treatment groups: untreated controls, prosthesis replacement by drug-free cement spacer, prosthesis replacement by teicoplanin-loaded cement spacer (1.2 g of teicoplanin/40 g of cement), i.m. injections of teicoplanin (20 mg/kg of body weight, twice a day for 7 days), or systemic antibiotic treatment combined with teicoplanin-loaded spacers. The most effective regimen combined systemic teicoplanin and antibiotic spacers

In vivo daptomycin efficacy against experimental vancomycin-resistant Enterococcus faecium endocarditis

International audienceObjectives - Daptomycin has become a first-line therapeutic option for vancomycin-resistant Enterococcus faecium infective endocarditis (IE). Although high doses (≥8 mg/kg) are often recommended, optimal doses, particularly for strains with MICs close to the susceptibility breakpoint (4 mg/L), are still debated.Methods - Daptomycin efficacy at doses equivalent to 8 mg/kg daptomycin (DAP8) and 12 mg/kg daptomycin (DAP12) in humans was evaluated in a rabbit model of aortic valve IE induced by 108 cfu of E. faecium reference strain Aus0004 (daptomycin MIC = 2 mg/L) or its in vitro mutant strain Mut4 (daptomycin MIC = 4 mg/L). Treatment began 48 h post-inoculation and lasted 5 days.Results - With Aus0004, the median log10 cfu/g of vegetations was significantly lower after DAP8 and DAP12 versus controls [6.05 (n = 12) and 2.15 (n = 10) versus 9.14 (n = 11), respectively; P Conclusions - DAP12 was the most successful strategy against IE due to a WT E. faecium strain (daptomycin MIC = 2 mg/L). To treat IE strains with MIC = 4 mg/L, DAP8 or DAP12 monotherapy was poorly effective with the risk of resistant mutant emergence. Reassessment of the daptomycin susceptibility breakpoint for enterococci seems necessary.<br

Efficacy of ceftazidime-avibactam in various combinations for the treatment of experimental osteomyelitis due to Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae

International audienceBackground: : Optimal treatment of carbapenemase-producing Enterobacterales (CPE) bone infections is poorly defined. This study evaluated the efficacy of the novel beta-lactam-beta-lactamase inhibitor—ceftazidime-avibactam (CAZ-AVI)—with different antibiotic combinations in an experimental model of CPE osteomyelitis. Methods: : KPC-99YC is a clinical strain of Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae with intermediate susceptibility to meropenem (MIC 4 mg/L), gentamicin (MIC 0.25 mg/L), colistin (MIC 0.25 mg/L), fosfomycin (MIC 4 mg/L) and ceftazidime-avibactam (MIC 1 mg/L). Time-kill curves were performed at 4x MIC. Osteomyelitis was induced in rabbits by tibial injection of 2×108 CFU of KPC-99YC. Six groups started treatment 14 days later for 7 days: control, colistin, CAZ-AVI, CAZ-AVI plus gentamicin, CAZ-AVI plus colistin and CAZ-AVI plus fosfomycin. Antibiotic dosages were selected to simulate plasma concentrations obtained in humans. Treatment was evaluated according to bone cultures quantified in log10 CFU. Results: : In vitro, CAZ-AVI plus colistin or gentamicin were rapidly bactericidal in contrast with CAZ-AVI plus fosfomycin. In vivo, compared with controls, colistin alone (P = 0.045) and CAZ-AVI alone or in combination significantly lowered bone bacterial counts (P &lt; 0.001). Bone sterilisation was achieved in 67% and 100% of animals with combinations of CAZ-AVI plus colistin or gentamicin (P = 0.001 and P &lt; 0.001, respectively) whereas other treatments were no different from controls. CAZ-AVI plus gentamicin provided greater bone bacterial reduction than CAZ-AVI plus colistin (P = 0.033). No CAZ-AVI-resistant strains emerged in treated rabbits, regardless of combination. Conclusions: : CAZ-AVI plus gentamicin was the best effective combination therapy. Combinations with CAZ-AVI appear to be a promising treatment of KPC-producing Klebsiella pneumoniae osteomyelitis

Efficacy of ceftazidime-avibactam in various combinations for the treatment of experimental osteomyelitis due to Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae

International audienceBackground: : Optimal treatment of carbapenemase-producing Enterobacterales (CPE) bone infections is poorly defined. This study evaluated the efficacy of the novel beta-lactam-beta-lactamase inhibitor—ceftazidime-avibactam (CAZ-AVI)—with different antibiotic combinations in an experimental model of CPE osteomyelitis. Methods: : KPC-99YC is a clinical strain of Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae with intermediate susceptibility to meropenem (MIC 4 mg/L), gentamicin (MIC 0.25 mg/L), colistin (MIC 0.25 mg/L), fosfomycin (MIC 4 mg/L) and ceftazidime-avibactam (MIC 1 mg/L). Time-kill curves were performed at 4x MIC. Osteomyelitis was induced in rabbits by tibial injection of 2×108 CFU of KPC-99YC. Six groups started treatment 14 days later for 7 days: control, colistin, CAZ-AVI, CAZ-AVI plus gentamicin, CAZ-AVI plus colistin and CAZ-AVI plus fosfomycin. Antibiotic dosages were selected to simulate plasma concentrations obtained in humans. Treatment was evaluated according to bone cultures quantified in log10 CFU. Results: : In vitro, CAZ-AVI plus colistin or gentamicin were rapidly bactericidal in contrast with CAZ-AVI plus fosfomycin. In vivo, compared with controls, colistin alone (P = 0.045) and CAZ-AVI alone or in combination significantly lowered bone bacterial counts (P &lt; 0.001). Bone sterilisation was achieved in 67% and 100% of animals with combinations of CAZ-AVI plus colistin or gentamicin (P = 0.001 and P &lt; 0.001, respectively) whereas other treatments were no different from controls. CAZ-AVI plus gentamicin provided greater bone bacterial reduction than CAZ-AVI plus colistin (P = 0.033). No CAZ-AVI-resistant strains emerged in treated rabbits, regardless of combination. Conclusions: : CAZ-AVI plus gentamicin was the best effective combination therapy. Combinations with CAZ-AVI appear to be a promising treatment of KPC-producing Klebsiella pneumoniae osteomyelitis