Telavancin activity tested against a contemporary collection of Gram-positive pathogens from USA Hospitals (2007–2009)

Prevalence, Mechanism, Genetic Diversity, and Cross-Resistance Patterns of Methicillin-Resistant Staphylococcus Isolated from Companion Animal Clinical Samples Submitted to a Veterinary Diagnostic Laboratory in the Midwestern United States

Methicillin-resistant Staphylococcus (MRS) is a leading cause of skin and soft tissue infections in companion animals, with limited treatment options available due to the frequent cross-resistance of MRS to other antibiotics. In this study, we report the prevalence, species distribution, genetic diversity, resistance mechanism and cross-resistance patterns of MRS isolated from companion animal (mostly dog and cat) clinical cases submitted to Iowa State University Veterinary Diagnostic Laboratory (ISU VDL) between 2012 and 2019. The majority of isolates were identified as Staphylococcus pseudintermedius (68.3%; 2379/3482) and coagulase-negative Staphylococcus (CoNS) (24.6%; 857/3482), of which 23.9% and 40.5% were phenotypically resistant to methicillin, respectively. Cross resistance to other β-lactams (and to a lesser extent to non-β-lactams) was common in both methicillin-resistant S. pseudintermedius (MRSP) and CoNS (MRCoNS), especially when oxacillin MIC was ≥4 μg/mL (vs. ≥0.5−<4 μg/mL). The PBP2a protein was detected by agglutination in 94.6% (521/551) MRSP and 64.3% (146/227) MRCoNS. A further analysis of 31 PBP2a-negative MRS isolates (all but one MRCoNS) indicated that 11 were mecA gene-positive while 20 were negative for mecA and other mec genes by PCR. The resistance to last-resort anti-staphylococcal human drugs (e.g., tigecycline, linezolid, vancomycin) among the MRS tested was none to very low. Even though genotyping indicated an overall high level of genetic diversity (87 unique PFGE patterns and 20 MLST types) among a subset of MRSP isolates tested (n = 106), certain genotypes were detected from epidemiologically connected cases at the same or different time points, suggesting persistence and/or nosocomial transmission. These results indicate a relatively high prevalence of MRS from companion animals in the Midwestern US; therefore, it is important to perform routine susceptibility testing of Staphylococcus in veterinary clinical settings for the selection of appropriate antimicrobial therapy.

The global prevalence of Daptomycin, Tigecycline, Quinupristin/Dalfopristin, and Linezolid-resistant Staphylococcus aureus and coagulase-negative staphylococci strains: a systematic review and meta-analysis

Objective

Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative Staphylococcus (MRCoNS) are among the main causes of nosocomial infections, which have caused major problems in recent years due to continuously increasing spread of various antibiotic resistance features. Apparently, vancomycin is still an effective antibiotic for treatment of infections caused by these bacteria but in recent years, additional resistance phenotypes have led to the accelerated introduction of newer agents such as linezolid, tigecycline, daptomycin, and quinupristin/dalfopristin (Q/D). Due to limited data availability on the global rate of resistance to these antibiotics, in the present study, the resistance rates of S. aureus, Methicillin-resistant S. aureus (MRSA), and CoNS to these antibiotics were collected.

Method

Several databases including web of science, EMBASE, and Medline (via PubMed), were searched (September 2018) to identify those studies that address MRSA, and CONS resistance to linezolid, tigecycline, daptomycin, and Q/D around the world.

Result

Most studies that reported resistant staphylococci were from the United States, Canada, and the European continent, while African and Asian countries reported the least resistance to these antibiotics. Our results showed that linezolid had the best inhibitory effect on S. aureus. Although resistances to this antibiotic have been reported from different countries, however, due to the high volume of the samples and the low number of resistance, in terms of statistical analyzes, the resistance to this antibiotic is zero. Moreover, linezolid, daptomycin and tigecycline effectively (99.9%) inhibit MRSA. Studies have shown that CoNS with 0.3% show the lowest resistance to linezolid and daptomycin, while analyzes introduced tigecycline with 1.6% resistance as the least effective antibiotic for these bacteria. Finally, MRSA and CoNS had a greater resistance to Q/D with 0.7 and 0.6%, respectively and due to its significant side effects and drug-drug interactions; it appears that its use is subject to limitations.

Conclusion

The present study shows that resistance to new agents is low in staphylococci and these antibiotics can still be used for treatment of staphylococcal infections in the world.

Efficacy of Telavancin Alone and in Combination with Ampicillin in a Rat Model of Enterococcus faecalis Endocarditis

We first assessed telavancin (TLV) pharmacokinetics in rats after a single subcutaneous dose of 35 mg/kg of body weight. The pharmacokinetic data were used to predict a TLV dose that simulates human exposure, and the efficacy of TLV was then evaluated using a TLV dose of 21 mg/kg every 12 h against Enterococcus faecalis OG1RF (TLV MIC of 0.06 μg/ml) in a rat endocarditis model with an indwelling catheter. Therapy was given for 3 days with TLV, daptomycin (DAP), or ampicillin (AMP) monotherapy and with combinations of TLV plus AMP, AMP plus gentamicin (GEN), and AMP plus ceftriaxone (CRO); rats were sacrificed 24 h after the last dose. Antibiotics were given to simulate clinically relevant concentrations or as used in other studies. TLV treatment resulted in a significant decrease in bacterial burden (CFU per gram) in vegetations from 6.0 log₁₀ at time 0 to 3.1 log₁₀ after 3 days of therapy. Bacterial burdens in vegetations were also significantly lower in the TLV-treated rats than in the AMP (P = 0.0009)- and AMP-plus-GEN (P = 0.035)-treated rats but were not significantly different from that of the AMP-plus-CRO-treated rats. Bacterial burdens from vegetations in TLV monotherapy and TLV-plus-AMP-and-DAP groups were similar to each other (P ≥ 0.05). Our data suggest that further study of TLV as a therapeutic alternative for deep-seated infections caused by vancomycin-susceptible E. faecalis is warranted.

Telavancin demonstrates activity against methicillin-resistant Staphylococcus aureus isolates with reduced susceptibility to vancomycin, daptomycin, and linezolid in broth microdilution MIC and one-compartment pharmacokinetic/pharmacodynamic models

Methicillin-resistant Staphylococcus aureus (MRSA) isolates have arisen with reduced susceptibility to several anti-MRSA agents. Telavancin (TLV), a novel anti-MRSA agent, retains low MICs against these organisms. Our objective was to determine the MICs for TLV, daptomycin (DAP), vancomycin (VAN), and linezolid (LZD) against daptomycin-nonsusceptible (DNS) S. aureus, vancomycin-intermediate S. aureus (VISA), heteroresistant VISA (hVISA), and linezolid-resistant (LZD(r)) S. aureus. We also evaluated these agents against each phenotype in pharmacokinetic/pharmacodynamic (PK/PD) models. Seventy DNS, 100 VISA, 180 hVISA, and 25 LZD(r) MRSA isolates were randomly selected from our library and tested to determine their MICs against TLV, DAP, VAN, and LZD via broth microdilution and a Trek panel. Four isolates were randomly selected for 168-h in vitro models to evaluate treatment with TLV at 10 mg/kg of body weight/day, DAP at 10 mg/kg/day, VAN at 1 g every 12 h (q12h), and LZD at 600 mg q12h. The MIC50/90 for TLV, DAP, VAN, and LZD against 70 DNS S. aureus isolates were 0.06/0.125 μg/ml, 2/4 μg/ml, 1/2 μg/ml, and 2/2 μg/ml, respectively. Against 100 VISA isolates, the MIC50/90 were 0.06/0.125 μg/ml, 1/1 μg/ml, 4/8 μg/ml, and 1/2 μg/ml, respectively. Against 170 hVISA isolates, the MIC50/90 were 0.06/0.125 μg/ml, 0.5/1 μg/ml, 1/2 μg/ml, and 1/2 μg/ml, respectively. Against 25 LZD(r) isolates, the MIC50/90 were 0.03/0.06 μg/ml, 1/1 μg/ml, 2/2 μg/ml, and 8/8 μg/ml, respectively. The TLV MIC was >0.125 μg/ml for 10/365 (2.7%) isolates. In PK/PD models, TLV was universally bactericidal at 168 h and statistically superior to all antibiotics against DNS S. aureus strain R2334. These data further establish the potency of TLV against resistant MRSA. The model data demonstrate in vitro bactericidal activity of TLV against hVISA, VISA, DNS S. aureus, and LZD(r) S. aureus strains. Further clinical research is warranted.

Potential role for telavancin in bacteremic infections due to gram-positive pathogens: focus on Staphylococcus aureus

Staphylococcus aureus bacteremia (SAB) is one of the most common serious bacterial infections and the most frequent invasive infection due to methicillin-resistant S. aureus (MRSA). Treatment is challenging, particularly for MRSA, because of limited treatment options. Telavancin is a bactericidal lipoglycopeptide antibiotic that is active against a range of clinically relevant gram-positive pathogens including MRSA. In experimental animal models of sepsis telavancin was shown to be more effective than vancomycin. In clinically evaluable patients enrolled in a pilot study of uncomplicated SAB, cure rates were 88% for telavancin and 89% for standard therapy. Among patients with infection due to only gram-positive pathogens enrolled in the 2 phase 3 studies of telavancin for treatment of hospital-acquired pneumonia, cure rates for those with bacteremic S. aureus pneumonia were 41% (9/22, telavancin) and 40% (10/25, vancomycin) with identical mortality rates. These data support further evaluation of telavancin in larger, prospective studies of SAB.

Update of the telavancin activity in vitro tested against a worldwide collection of Gram-positive clinical isolates (2013), when applying the revised susceptibility testing method

A revised broth microdilution susceptibility testing method for telavancin was approved by the Food and Drug Administration (FDA). Telavancin activity was assessed against Gram-positive pathogens collected worldwide (2013) using the revised method. A total of 12,346 isolates from 90 sites were included as part of the Telavancin International Surveillance Program for the Americas, Europe, and Asia-Pacific. Telavancin had MIC50 and MIC90 values of 0.03 and 0.06 μg/mL, respectively, against staphylococci, regardless of methicillin susceptibility, and inhibited all Staphylococcus aureus at ≤0.12 μg/mL (revised FDA breakpoint). Telavancin was 8-fold more active than daptomycin (MIC50/90, 0.25/0.5 μg/mL) and 16- to 32-fold more active than vancomycin (MIC50/90, 1/1 μg/mL) and linezolid (MIC50/90, 1/1 μg/mL) against methicillin-resistant S. aureus. All 692 vancomycin-susceptible Enterococcus faecalis were inhibited by telavancin (MIC50/90, 0.12/0.12 μg/mL) at ≤0.25 μg/mL (FDA breakpoint), except for 1 strain (MIC, 0.5 μg/mL). All Enterococcus faecium and E. faecalis with telavancin MIC values of ≥0.5 and ≥1 μg/mL, respectively, had a VanA phenotype. A comparison data analysis based on the MIC90 demonstrated that telavancin was at least 8-fold more potent than comparators against vancomycin-susceptible enterococci. Streptococci showed telavancin MIC50 values of ≤0.015 μg/mL, except for Streptococcus agalactiae (MIC50, 0.03 μg/mL). These in vitro results obtained by the recently approved susceptibility testing method establish a new benchmark of telavancin activity worldwide.

Baseline activity of telavancin against Gram-positive clinical isolates responsible for documented infections in U.S. hospitals (2011-2012) as determined by the revised susceptibility testing method

Telavancin had MIC50 and MIC90 values of 0.03 and 0.06 μg/ml (100.0% susceptible), respectively, against methicillin-resistant and -susceptible Staphylococcus aureus. Telavancin was active against vancomycin-susceptible Enterococcus faecalis (MIC50/90, 0.12/0.12 μg/ml; 100% susceptible) and Enterococcus faecium (MIC50/90, 0.03/0.06 μg/ml), while higher MIC values were obtained against vancomycin-resistant E. faecium (MIC50/90, 1/2 μg/ml) and E. faecalis (MIC50/90, >2/>2 μg/ml). Streptococci showed telavancin modal MIC results of ≤ 0.015 μg/ml, except against Streptococcus agalactiae (i.e., 0.03 μg/ml). This study reestablishes the telavancin spectrum of activity against isolates recovered from the United States (2011-2012) using the revised broth microdilution method.

Revised reference broth microdilution method for testing telavancin: effect on MIC results and correlation with other testing methodologies

The reference broth microdilution (BMD) antimicrobial susceptibility testing method for telavancin was revised to include dimethyl sulfoxide (DMSO) as a solvent and diluent for frozen-form panel preparation, following the CLSI recommendations for water-insoluble agents. Polysorbate 80 (P-80) was also added to the test medium to minimize proven drug losses associated with binding to plastic surfaces. Four hundred sixty-two Gram-positive isolates, including a challenge set of organisms with reduced susceptibilities to comparator agents, were selected and tested using the revised method for telavancin, and the MIC results were compared with those tested by the previously established method and several Sensititre dry-form BMD panel formulations. The revised method provided MIC results 2- to 8-fold lower than the previous method when tested against staphylococci and enterococci, resulting in MIC50 values of 0.03 to 0.06 μg/ml for staphylococci and 0.03 and 0.12 μg/ml for Enterococcus faecium and Enterococcus faecalis, respectively. Less-significant MIC decreases (1 to 2 log2 dilution steps) were observed when testing streptococci in broth supplemented with blood, which showed similar MIC50 values for both methods. However, Streptococcus pneumoniae had MIC50 results of 0.008 and 0.03 μg/ml when tested by the revised and previous methods, respectively. Highest essential agreement rates (≥94.0%) were noted for one candidate dry-form panel formulation compared to the revised test. The revised BMD method provides lower MIC results for telavancin, especially when tested against staphylococci and enterococci. This is secondary to the use of DMSO for panel production and the presence of P-80, which ensure the proper telavancin testing concentration and result in a more accurate MIC determination. Moreover, earlier studies where the previous method was applied underestimated the in vitro drug potency.

Treatment of infections due to resistant Staphylococcus aureus

This chapter reviews data on the treatment of infections caused by drug-resistant Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA). This review covers findings reported in the English language medical literature up to January of 2013. Despite the emergence of resistant and multidrug-resistant S. aureus, we have seven effective drugs in clinical use for which little resistance has been observed: vancomycin, quinupristin-dalfopristin, linezolid, tigecycline, telavancin, ceftaroline, and daptomycin. However, vancomycin is less effective for infections with MRSA isolates that have a higher MIC within the susceptible range. Linezolid is probably the drug of choice for the treatment of complicated MRSA skin and soft tissue infections (SSTIs); whether it is drug of choice in pneumonia remains debatable. Daptomycin has shown to be non-inferior to either vancomycin or β-lactams in the treatment of staphylococcal SSTIs, bacteremia, and right-sided endocarditis. Tigecycline was also non-inferior to comparator drugs in the treatment of SSTIs, but there is controversy about whether it is less effective than other therapeutic options in the treatment of more serious infections. Telavancin has been shown to be non-inferior to vancomycin in the treatment of SSTIs and pneumonia, but has greater nephrotoxicity. Ceftaroline is a broad-spectrum cephalosporin with activity against MRSA; it is non-inferior to vancomycin in the treatment of SSTIs. Clindamycin, trimethoprim-sulfamethoxazole, doxycycline, rifampin, moxifloxacin, and minocycline are oral anti-staphylococcal agents that may have utility in the treatment of SSTIs and osteomyelitis, but the clinical data for their efficacy is limited. There are also several drugs with broad-spectrum activity against Gm-positive organisms that have reached the phase II and III stages of clinical testing that will hopefully be approved for clinical use in the upcoming years: oritavancin, dalbavancin, omadacycline, tedizolid, delafloxacin, and JNJ-Q2. Thus, there are currently many effective drugs to treat resistant S. aureus infections and many promising agents in the pipeline. Nevertheless, S. aureus remains a formidable adversary, and despite our deep bullpen of potential therapies, there are still frequent treatment failures and unfortunate clinical outcomes. The following discussion summarizes the clinical challenges presented by MRSA, the clinical experience with our current anti-MRSA antibiotics, and the gaps in our knowledge on how to use these agents to most effectively combat MRSA infections.

Multidrug-resistant bacteria in organ transplantation: an emerging threat with limited therapeutic options

Multidrug-resistant organisms (MDROs) are an emerging threat in solid organ transplantation (SOT). The changing epidemiology of these MDROs is reviewed along with the growing evidence regarding risk factors and outcomes associated with both colonization and infection in SOT. The management of these infections is complicated by the lack of antimicrobial agents available to treat these infections, and only a handful of new agents, especially for the treatment of MDR GNR infections, are being evaluated in clinical trials. Due to the increased prevalence of MDROs and limited treatment options, as well as organ shortages, transplant candidacy and use of organs from donors with evidence of MDRO colonization and/or infection remain controversial. Increasing collaboration between transplant programs, individual practitioners, infection control programs, and researchers in antimicrobial development will be needed to face this challenge.

Telavancin in therapy of experimental aortic valve endocarditis in rabbits due to daptomycin-nonsusceptible methicillin-resistant Staphylococcus aureus

A number of cases of both methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) strains that have developed daptomycin resistance (DAP-R) have been reported. Telavancin (TLV) is a lipoglycopeptide agent with a dual mechanism of activity (cell wall synthesis inhibition plus depolarization of the bacterial cell membrane). Five recent daptomycin-susceptible (DAP-S)/DAP-R MRSA isogenic strain pairs were evaluated for in vitro TLV susceptibility. All five DAP-R strains (DAP MICs ranging from 2 to 4 μg/ml) were susceptible to TLV (MICs of ≤0.38 μg/ml). In vitro time-kill analyses also revealed that several TLV concentrations (1-, 2-, and 4-fold MICs) caused rapid killing against the DAP-R strains. Moreover, for 3 of 5 DAP-R strains (REF2145, A215, and B(2.0)), supra-MICs of TLV were effective at preventing regrowth at 24 h of incubation. Further, the combination of TLV plus oxacillin (at 0.25× or 0.50× MIC for each agent) increased killing of DAP-R MRSA strains REF2145 and A215 at 24 h (∼2-log and 5-log reductions versus TLV and oxacillin alone, respectively). Finally, using a rabbit model of aortic valve endocarditis caused by DAP-R strain REF2145, TLV therapy produced a mean reduction of >4.5 log(10) CFU/g in vegetations, kidneys, and spleen compared to untreated or DAP-treated rabbits. Moreover, TLV-treated rabbits had a significantly higher percentage of sterile tissue cultures (87% in vegetations and 100% in kidney and spleen) than all other treatment groups (P < 0.0001). Together, these results demonstrate that TLV has potent bactericidal activity in vitro and in vivo against DAP-R MRSA isolates.