Ω76: A designed antimicrobial peptide to combat carbapenem- and tigecycline-resistant Acinetobacter baumannii.
ABSTRACT: Drug resistance is a public health concern that threatens to undermine decades of medical progress. ESKAPE pathogens cause most nosocomial infections, and are frequently resistant to carbapenem antibiotics, usually leaving tigecycline and colistin as the last treatment options. However, increasing tigecycline resistance and colistin's nephrotoxicity severely restrict use of these antibiotics. We have designed antimicrobial peptides using a maximum common subgraph approach. Our best peptide (Ω76) displayed high efficacy against carbapenem and tigecycline-resistant Acinetobacter baumannii in mice. Mice treated with repeated sublethal doses of Ω76 displayed no signs of chronic toxicity. Sublethal Ω76 doses co-administered alongside sublethal colistin doses displayed no additive toxicity. These results indicate that Ω76 can potentially supplement or replace colistin, especially where nephrotoxicity is a concern. To our knowledge, no other existing antibiotics occupy this clinical niche. Mechanistically, Ω76 adopts an α-helical structure in membranes, causing rapid membrane disruption, leakage, and bacterial death.
Project description:Emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) strains that also exhibit resistance to tigecycline and colistin have become a major clinical concern, as these two agents are the last-resort antibiotics used for treatment of CRKP infections. A leukemia patient infected with CRKP was subjected to follow-up analysis of variation in phenotypic and genotypic characteristics of CRKP strains isolated from various specimens at different stages of treatment over a period of 3 years. Our data showed that (1) carbapenem treatment led to the emergence of CRKP in the gastrointestinal (GI) tract of the patient, which subsequently caused infections at other body sites as well as septicemia; (2) treatment with tigecycline led to the emergence of tigecycline-resistant CRKP, possibly through induction of the expression of a variant tet(A) gene located in a conjugative plasmid; (3) colistin treatment was effective in clearing CRKP from the bloodstream but led to the emergence of mcr-1-positive Enterobacteriaceae strains as well as colistin-resistant CRKP in the GI tract due to inactivation of the mgrB gene; and (4) tigecycline- and colistin-resistant CRKP could persist in the human GI tract for a prolonged period even without antibiotic selection pressure. In conclusion, clinical CRKP strains carrying a conjugative plasmid that harbors the blaKPC-2 and tet(A) variant genes readily evolve into tigecycline- and colistin-resistant CRKP upon treatment with these two antibiotics and persist in the human GI tract.
Project description:Colistin is one of the last-resort options for carbapenem-resistant Klebsiella pneumoniae (CRKP) infections if novel antibiotics are unavailable, where the development of colistin resistance during treatment represents a major challenge for clinicians. We aimed to investigate the risk factors associated with the development of colistin resistance in patients with CRKP infections following colistin treatment. We conducted a retrospective case-control study of patients with CRKP strains available before and after colistin treatment at a medical center in Taiwan, between October 2016 and November 2020. Cases (<i>n</i> = 35) included patients with an initial colistin-susceptible CRKP (ColS-CRKP) strain and a subsequent colistin-resistant CRKP (ColR-CRKP) strain. Controls (<i>n</i> = 18) included patients with ColS-CRKP as both the initial and subsequent strains. The 30-day mortality rate after the subsequent CRKP isolation was not different between cases and controls (12/35 [34%] versus 5/18 [28%] [<i>P</i> = 0.631]). <i>bla</i><sub>KPC</sub> (<i>n</i> = 38) and <i>bla</i><sub>OXA-48</sub> (<i>n</i> = 11) accounted for the major mechanisms of carbapenem resistance. Alterations in <i>mgrB</i> were found in 18/35 (51%) ColR-CRKP strains, and <i>mcr-1</i> was not detected in any of the strains. More patients received combination therapy in the control group than in the case group (17/18 versus 21/35 [<i>P</i> = 0.008]). The logistic regression model indicated that combination therapy with tigecycline was protective against the acquisition of colistin resistance (odds ratio, 0.17; 95% confidence interval, 0.05 to 0.62 [<i>P </i>= 0.008]). We observed that the inclusion of tigecycline in colistin treatment mitigated the risk of acquiring colistin resistance. These results offer insight into using the combination of tigecycline and colistin for the treatment of CRKP infections in antimicrobial stewardship. <b>IMPORTANCE</b> Treatment of carbapenem-resistant Klebsiella pneumoniae (CRKP) infections is challenging due to the limited options of antibiotics. Colistin is one of the last-resort antibiotics if novel antimicrobial agents are not available. It is crucial to identify modifiable clinical factors associated with the emergence of resistance during colistin treatment. Here, we found that the addition of tigecycline to colistin treatment prevented the acquisition of colistin resistance. Colistin-tigecycline combination therapy is therefore considered a hopeful option in antimicrobial stewardship to treat CRKP infections.
Project description:Carbapenemase-producing Enterobacterales have become a severe public health concern because of their rapidly transmissible resistance elements and limited treatment options. The most effective antimicrobial combinations against carbapenemase-producing Enterobacterales are currently unclear. Here, we aimed to assess the therapeutic effects of seven antimicrobial combinations (colistin-meropenem, colistin-tigecycline, colistin-rifampicin, colistin-erythromycin, meropenem-tigecycline, meropenem-rifampicin, and meropenem-tigecycline-colistin) against twenty-four carbapenem-producing Enterobacterales (producing bla KPC, bla NDM, coexisting bla NDM and bla IMP, and coexisting mcr-1/8/9 and bla NDM genes) and one carbapenem-susceptible Enterobacterales using the checkerboard assay, time-kill curves, and scanning electron microscopy. None of the combinations were antagonistic. The combination of colistin-rifampicin showed the highest synergistic effect of 76% (19/25), followed by colistin-erythromycin at 60% (15/25), meropenem-rifampicin at 24% (6/25), colistin-meropenem at 20% (5/25), colistin-tigecycline at 20% (5/25), and meropenem-tigecycline at 4% (1/25). The triple antimicrobial combinations of meropenem-tigecycline-colistin had a synergistic effect of 100%. Most double antimicrobial combinations were ineffective on isolates with coexisting bla NDM and bla IMP genes. Meropenem with tigecycline showed no synergistic effect on isolates that produced different carbapenemase genes and were highly resistant to meropenem (92% meropenem MIC ? 16 mg/mL). Colistin-tigecycline showed no synergistic effect on Escherichia coli producing bla NDM - 1 and Serratia marcescens. Time-kill curves showed that antimicrobial combinations achieved an eradication effect (? 3 log10 decreases in colony counts) within 24 h without regrowth, based on 1 × MIC of each drug. The synergistic mechanism of colistin-rifampicin may involve the colistin-mediated disruption of bacterial membranes, leading to severe alterations in their permeability, then causes more rifampicin to enter the cell and induces cell death. In conclusion, the antimicrobial combinations evaluated in this study may facilitate the successful treatment of patients infected with carbapenemase-producing pathogens.
Project description:Infections due to carbapenem-resistant NDM-producing Escherichia coli represent a major therapeutic challenge, especially in situations of pre-existing colistin resistance. The aim of this study was to investigate combinatorial pharmacodynamics of colistin and tigecycline against E. coli harboring bla NDM- 5 and mcr-1, with possible mechanisms explored as well. Colistin disrupted the bacterial outer-membrane and facilitated tigecycline uptake largely independent of mcr-1 expression, which allowed a potentiation of the tigecycline-colistin combination. A concentration-dependent decrease in colistin MIC and EC50 was observed with increasing tigecycline levels. Clinically relevant concentrations of colistin and tigecycline combination significantly decreased bacterial density of colistin-resistant E. coli by 3.9 to 6.1-log10 cfu/mL over 48 h at both inoculums of 106 and 108 cfu/mL, and were more active than each drug alone (P < 0.01). Importantly, colistin and tigecycline combination therapy was efficacious in the murine thigh infection model at clinically relevant doses, resulting in >2.0-log10cfu/thigh reduction in bacterial density compared to each monotherapy. These data suggest that the use of colistin and tigecycline combination can provide a therapeutic alternative for infection caused by multidrug-resistant E. coli that harbored both bla NDM- 5 and mcr-1.
Project description:Objective:Here, we report a case of severe infection caused by Escherichia coli that harbored mcr-1, bla NDM-5, and acquired resistance to tigecycline during tigecycline salvage therapy. Methods:Antimicrobial susceptibility testing, Southern blot hybridization, and complete genome sequence of the strains were carried out. The genetic characteristics of the mcr-1 and bla NDM-5 plasmids were analyzed. The whole genome sequencing of mcr-1-containing plasmid was completed. Finally, putative single nucleotide polymorphisms and deletion mutations in the tigecycline-resistant strain were predicted. Results:Three E. coli isolates were obtained from ascites, pleural effusion, and stool of a patient; they were resistant to almost all the tested antibiotics. The first two strains separated from ascites (E-FQ) and hydrothorax (E-XS) were susceptible to amikacin and tigecycline; however, the third strain from stool (E-DB) was resistant to tigecycline after nearly 3 weeks' treatment with tigecycline. All three isolates possessed both mcr-1 and bla NDM-5. The bla NDM-5 gene was found on the IncX3 plasmid, whereas the mcr-1, fosA3 and blaCTX-M-14 were located on the IncHI2 plasmid. Mutations in acrB and lon were the reason for the resistance to tigecycline. Conclusion:This is the first report of a colistin-, carbapenem-, and tigecycline-resistant E. coli in China. Tigecycline resistance acquired during tigecycline therapy is of great concern for us because tigecycline is a drug of last resort to treat carbapenem-resistant Gram-negative bacterial infections. Furthermore, the transmission of such extensively drug-resistant isolates may pose a great threat to public health.
Project description:The spread of carbapenem-non-susceptible Klebsiella pneumoniae strains bearing different resistance determinants is a rising problem worldwide. Especially infections with KPC (Klebsiella pneumoniae carbapenemase) - producers are associated with high mortality rates due to limited treatment options. Recent clinical studies of KPC-blood stream infections revealed that colistin-based combination therapy with a carbapenem and/or tigecycline was associated with significantly decreased mortality rates when compared to colistin monotherapy. However, it remains unclear if these observations can be transferred to K. pneumoniae harboring other mechanisms of carbapenem resistance. A three-dimensional synergy analysis was performed to evaluate the benefits of a triple combination with meropenem, tigecycline and colistin against 20 K. pneumoniae isolates harboring different ?-lactamases. To examine the mechanism behind the clinically observed synergistic effect, efflux properties and outer membrane porin (Omp) genes (ompK35 and ompK36) were also analyzed. Synergism was found for colistin-based double combinations for strains exhibiting high minimal inhibition concentrations against all of the three antibiotics. Adding a third antibiotic did not result in further increased synergistic effect in these strains. Antagonism did not occur. These results support the idea that colistin-based double combinations might be sufficient and the most effective combination partner for colistin should be chosen according to its MIC.
Project description:UNLABELLED:Colistin is increasingly used as an antibiotic of last resort for the treatment of carbapenem-resistant Gram-negative infections. The plasmid-borne colistin resistance gene mcr-1 was initially identified in animal and clinical samples from China and subsequently reported worldwide, including in the United States. Of particular concern is the spread of mcr-1 into carbapenem-resistant bacteria, thereby creating strains that approach pan-resistance. While several reports of mcr-1 have involved carbapenem-resistant strains, no such isolates have been described in the United States. Here, we report the isolation and identification of an Escherichia coli strain harboring both mcr-1 and carbapenemase gene blaNDM-5 from a urine sample in a patient without recent travel outside the United States. The isolate exhibited resistance to both colistin and carbapenems, but was susceptible to amikacin, aztreonam, gentamicin, nitrofurantoin, tigecycline, and trimethoprim-sulfamethoxazole. The mcr-1- and blaNDM-5-harboring plasmids were completely sequenced and shown to be highly similar to plasmids previously reported from China. The strain in this report was first isolated in August 2014, highlighting an earlier presence of mcr-1 within the United States than previously recognized. IMPORTANCE:Colistin has become the last line of defense for the treatment of infections caused by Gram-negative bacteria resistant to multiple classes of antibiotics, in particular carbapenem-resistant Enterobacteriaceae (CRE). Resistance to colistin, encoded by the plasmid-borne gene mcr-1, was first identified in animal and clinical samples from China in November 2015 and has subsequently been reported from numerous other countries. In April 2016, mcr-1 was identified in a carbapenem-susceptible Escherichia coli strain from a clinical sample in the United States, followed by a second report from a carbapenem-susceptible E. coli strain originally isolated in May 2015. We report the isolation and identification of an E. coli strain harboring both colistin (mcr-1) and carbapenem (blaNDM-5) resistance genes, originally isolated in August 2014 from urine of a patient with recurrent urinary tract infections. To our knowledge, this is the first report in the United States of a clinical bacterial isolate with both colistin and carbapenem resistance, highlighting the importance of active surveillance efforts for colistin- and carbapenem-resistant organisms.
Project description:BACKGROUND AND OBJECTIVES:Despite colistin's longstanding reported association with nephrotoxicity, the attributable risk and timing of toxicity onset are still unknown. Whether substantial toxicity occurs during the initial 72 hours of exposure has important implications for early treatment decisions. The objective of this study was to compare colistin-exposed patients with a matched control group given other broad spectrum antibiotics. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS:We conducted a retrospective cohort study in patients treated for multidrug-resistant Pseudomonas, Klebsiella, or Acinetobacter spp. Colistin-exposed patients were matched to unexposed controls using propensity scores. AKI was defined according to the Kidney Disease Improving Global Outcomes creatinine criteria. Incidence rate ratios and risk differences of AKI in the matched cohort were estimated with the generalized estimating equation Poisson regression model. Risk factors for AKI were tested for effect modification in the matched cohort. RESULTS:The study included 150 propensity-matched pairs with similar types of infection, similar delays to effective treatment, and similar baseline characteristics. Incidence of AKI was 77 of 150 (51%) in the colistin group versus 33 of 150 (22%) in matched controls (risk difference, 29%; 95% confidence interval, 19 to 39), corresponding to a number needed to harm of 3.5. Early toxicity was apparent, because AKI risk was higher in colistin-exposed patients at 72 hours of exposure (incidence rate ratio, 1.9; 95% confidence interval, 1.1 to 3.5). In both groups, hospital mortality in patients who experienced AKI was lower if kidney function returned to baseline during hospitalization. The effect of colistin exposure on AKI risk varied inversely according to baseline hemoglobin concentration. CONCLUSIONS:Colistin is associated with substantial excess AKI that is apparent within the first 72 hours of treatment. Colistin's toxicity varied according to baseline hemoglobin concentration. PODCAST:This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2018_03_15_CJASNPodcast_18_4_M.mp3.
Project description:Colistin and tigecycline are the last options against carbapenem-resistant hypervirulent <i>Klebsiella pneumoniae</i> (CR-hvKP). Intersecting resistance determinants have been detected between these antibiotics; however, there is only limited evidence of such association. Here, we describe a colistin-resistant CR-hvKP isolated from a patient with severe neonatal bacteremia treated with tigecycline as opposed to colistin before isolation of this strain, providing a clinical clue to colistin resistance under tigecycline pressure. Furthermore, an ST11-K64 KPC-2-producing, colistin-susceptible CR-hvKP strain was subjected to experimental evolution toward colistin resistance under tigecycline and colistin pressure to verify this phenomenon <i>in vitro</i>. The biological impact of acquiring colistin resistance on fitness and virulence was also studied. As expected, the parental strain rapidly developed colistin resistance under both tigecycline and colistin selection. However, different from the colistin resistance mechanism in the clinical strain that was due to an IS<i>Kpn26</i> insertion in the <i>mgrB</i> gene, the mutants in this study developed colistin resistance through a ∼4.4 or ∼4.6 kb deletion including the <i>mgrB</i> locus as well as the <i>kdgR</i>, <i>yobH</i>, <i>yebO</i>, <i>yobF</i>, <i>cspC</i>, <i>ftsI</i>, and <i>rlmA</i> genes. Although the virulence of the colistin-resistant mutants, as determined in the <i>Galleria mellonella</i> model, decreased compared with that of the parent strain, it was still higher than that of NTUH-K2044. This suggests a slight virulence cost when CR-hvKP develops colistin resistance under tigecycline or colistin pressure. Together, our results provide clinical and experimental evidence for the association between colistin resistance and tigecycline pressure in CR-hvKP, highlighting a critical issue in the clinical setting.
Project description:Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-Kp) poses a major threat to human health worldwide. Combination therapies of antibiotics with different mechanisms have been recommended in literatures. This study assessed in vitro antibacterial activities and synergistic activities of ceftazidime/avibactam alone and in combinations against KPC-Kp. In total, 70 isolates from 2 hospitals in Beijing were examined in our study. By using the agar dilution method and broth dilution method, we determined the minimum inhibitory concentration (MIC) of candidate antibiotics. Ceftazidime/avibactam demonstrated promising susceptibility against KPC-Kp (97.14%). Synergistic activities testing was achieved by checkerboard method and found ceftazidime/avibactam-amikacin displayed synergism in 90% isolates. Ceftazidime/avibactam-colistin displayed partial synergistic in 43% isolates, and ceftazidime/avibactam-tigecycline displayed indifference in 67% isolates. In time-kill assays, antibiotics at 1-fold MIC were mixed with bacteria at 1 × 105 CFU/ml and Mueller-Hinton broth (MHB). Combinations of ceftazidime/avibactam with amikacin and tigecycline displayed better antibacterial effects than single drug. Ceftazidime/avibactam-colistin combination did not exhibit better effect than single drug. In KPC-Kp infections, susceptibility testing suggested that ceftazidime/avibactam may be considered as first-line choice. However, monotherapy is often inadequate in infection management. Thus, our study revealed that combination therapy including ceftazidime/avibactam colistin and ceftazidime/avibactam tigecycline may benefit than monotherapy in KPC-Kp treatment. Further pharmacokinetic/pharmacodynamic and mutant prevention concentration studies should be performed to optimize multidrug-regimens.