CLSI Broth Microdilution Research Articles

1284. Outcomes by Baseline Pathogens and Susceptibility in the STRIVE Phase 2 Trial of Once-Weekly Rezafungin for Treatment of Candidemia and Invasive Candidiasis Compared with Caspofungin

BackgroundRezafungin (RZF) is a novel echinocandin in Phase 3 development for treatment of candidemia and invasive candidiasis (IC) and for prevention of invasive fungal disease caused by Candida, Aspergillus, and Pneumocystis in blood and marrow transplant recipients. This analysis of the completed Phase 2 STRIVE trial (NCT02734862) of RZF treatment was conducted to evaluate outcomes based on baseline pathogen and susceptibility.MethodsIn STRIVE, adults (≥ 18 y) with systemic signs and mycological evidence of candidemia and/or IC were randomized to either RZF once weekly or caspofungin (CAS) once daily for ≥ 14 days (Fig. 1). The primary efficacy endpoint was Overall Response (resolution of clinical signs of infection + mycological eradication) at Day 14. For this analysis, outcomes by treatment group were stratified by Candida species and by its in vitro susceptibility (CLSI broth microdilution MIC values; M27-Ed4).Figure 1. Treatment Groups of the Phase 2 STRIVE Trial ResultsA total of 196 Candida isolates were recovered from 183 patients across all treatment groups (Fig. 2). C. albicans was the most common species, followed by C. glabrata, C. parapsilosis, and C. tropicalis; non-albicans Candida comprised 54% of all baseline isolates (Fig. 2). Among all clinical isolates, MIC distributions and ranges for RZF were generally lower than or comparable to those for CAS (Table 1). The rate of Overall Response (as defined above) against C. parapsilosis was lower for CAS than for RZF (Table 2). Overall, outcomes by Candida species and MIC did not appear to be affected by MIC values for either RZF or CAS (Table 1).Figure 2. Candida Species Distribution and MIC ranges in the Phase 2 STRIVE Trial (mITT) Table 1. Overall Response Rates (%) for Most Frequently Isolated Candida Species at Baseline by Treatment Group and MIC Values (mITT) Table 2. Overall Response Rates (%) for Most Frequently Isolated Candida Species at Baseline by Treatment Group (mITT) ConclusionThis analysis demonstrated RZF efficacy across multiple Candida species. RZF outcomes were similar to or better than those for CAS regardless of species identified. There was no clear correlation between increased MICs and clinical outcomes although, based on MICs, all isolates exhibited a wild-type in vitro susceptibility profile. These findings from STRIVE, together with future analyses from the ongoing Phase 3 trial of RZF treatment of candidemia and IC (ReSTORE; NCT03667690), will further our understanding of the relationships between MIC values and clinical outcomes in patients with candidemia or IC.Disclosures Jeffrey B. Locke, PhD, Cidara Therapeutics, Inc. (Employee, Shareholder) Rolando Viani, MD, Cidara Therapeutics, Inc. (Employee, Shareholder) Peter Pappas, MD, SCYNEXIS, Inc. (Consultant, Advisor or Review Panel member, Research Grant or Support) Mahmoud Ghannoum, PhD, Amplyx (Grant/Research Support)Cidara (Grant/Research Support)Scynexis (Consultant, Grant/Research Support) Taylor Sandison, MD, MPH, Cidara Therapeutics, Inc. (Employee, Shareholder)

Assessment of the in vitro activity of ceftazidime/avibactam against a global collection of multidrug-resistant Klebsiella spp. from the INFORM surveillance programme (2015–2017)

Infections caused by Klebsiella spp. are difficult to treat when these pathogens exhibit multidrug resistance (resistance to ≥3 drug classes). This study determined rates of multidrug-resistant (MDR) Klebsiella spp. among clinical isolates collected globally (Africa/Middle East, Asia, Oceania, Europe and Latin America, but not the USA) as part of the INFORM surveillance programme (2015-2017). In vitro antimicrobial activities of ceftazidime/avibactam (CAZ/AVI) and comparator antimicrobials against these MDR isolates were determined using CLSI broth microdilution methodology. MICs were interpreted using EUCAST 2019 breakpoints. By species, 38.4% (4555/11 864) of Klebsiella pneumoniae isolates were MDR, followed by 28.3% (452/1598) of Klebsiella aerogenes. The majority (69.5%) of MDR K. pneumoniae isolates were extended-spectrum β-lactamase (ESBL)-positive and carbapenemase-negative compared with 1.3% of MDR K. aerogenes. Globally, >92% of MDR K. pneumoniae isolates were resistant to amoxicillin/clavulanic acid, aztreonam, cefepime, ceftazidime or ceftriaxone. CAZ/AVI, colistin and tigecycline MIC90 values were 1-2 mg/L against the global collection of MDR K. pneumoniae and MDR K. aerogenes. Approximately 5% (216/4555) of all MDR K. pneumoniae isolates and 1.1% (5/452) of all MDR K. aerogenes isolates were resistant to CAZ/AVI. Rates of resistance to CAZ/AVI and colistin were low for MDR, ESBL-positive, carbapenemase-negative K. pneumoniae (0.1% and 3.0%, respectively). Resistance to CAZ/AVI was highest among MDR, carbapenemase-positive, metallo-β-lactamase (MBL)-positive K. pneumoniae (98.0%), whereas colistin resistance was highest among MDR, carbapenemase-positive, MBL-negative isolates (30.2%). The results of this study suggest that CAZ/AVI, colistin and tigecycline are potential treatment options for nosocomial infections caused by MDR Klebsiella spp. isolates.

Evaluation of the Haemophilus influenzae EUCAST and CLSI disc diffusion methods to recognize aminopenicillin and amoxicillin/clavulanate resistance.

Implementation of EUCAST susceptibility testing in an Australian hospital laboratory demonstrated higher rates of aminopenicillin and amoxicillin/clavulanate resistance in Haemophilus influenzae than previously recognized. This study aimed to better define the variability in the detection of β-lactam resistance based on EUCAST and CLSI disc diffusion (DD) methodology, by comparison with the recommended reference method, broth microdilution (BMD), and by concordance with genomic analysis. A total of 100 random H. influenzae isolates were assessed for ampicillin and amoxicillin/clavulanate susceptibility by EUCAST and CLSI DD and BMD. WGS was used to analyse the ftsI gene of a subset of isolates with β-lactam resistance, other than that due to isolated β-lactamase production. Of the 100 isolates, 32 were categorized as either β-lactamase negative, ampicillin resistant (BLNAR) (n = 18) or β-lactamase positive, amoxicillin/clavulanate resistant (BLPACR) (n = 14) by EUCAST DD. All 18 EUCAST BLNAR isolates were genotypically confirmed by WGS. Five of 18 BLNAR isolates were concordant by CLSI DD, 12 by EUCAST BMD and 4 by CLSI BMD. Nine of 14 EUCAST BLPACR isolates were confirmed by WGS; the remaining 5 were 1 mm below the EUCAST DD breakpoint. Only one isolate was detected as BLPACR by CLSI DD. Group III mutations associated with high-level ampicillin resistance were identified in 10/32 isolates. The EUCAST DD susceptibility method is more reliable than either CLSI or BMD for the detection of genotypically defined BLNAR resistance. However, accurate categorization of amoxicillin/clavulanate resistance remains problematic. Continuous and reproducible surveillance of resistance is needed; for this to be possible, robust susceptibility methods are required.

Analysis of Susceptibilities of Carbapenem Resistant Enterobacterales to Colistin in Intra-Abdominal, Respiratory and Urinary Tract Infections from 2015 to 2017.

PurposeTo evaluate the susceptibility rates of carbapenem-resistant (CR)-Enterobacterales strains from Chinese intra-abdominal infections (IAI), respiratory tract infections (RTI) and urinary tract infections (UTI) between 2015 and 2017 to colistin.MethodsIn total, 7138 Enterobacterales including 1074 CR-Enterobacterales strains were isolated from IAI+UTI+RTI samples and collected in 21 hospitals across 7 regions of China. Antimicrobial susceptibilities were determined at a central laboratory using CLSI broth microdilution and interpretive standards.ResultsFrom 2015 to 2017, E. coli (51.4%) and K. pneumoniae (30.0%) accounted for the majority of Enterobacterales isolated from IAIs, UTIs and RTIs. The percentage of CR strains within the species was highest for S. marcescens (27.9%), followed by K. pneumoniae (24.8%), P. mirabilis (22.6), K. oxytoca (19.5%), E. cloacae (17.7%), C. freundii (12.5%), K. aerogenes (11.0%) and lowest for E. coli (6.9%). Colistin susceptibilities were generally higher in CS than in CR isolates and were 83.5% for CR-E. coli, 88.6% for CR-K. pneumoniae, 79.2% for CR-E. cloacae and 87.5% for CR-K. aerogenes. For IAI and UTI isolates in particular, CR-E. coli and CR-K. pneumoniae showed a trend of decreasing susceptibility, which was especially noted for CR-E. coli in UTI isolates, and for both organisms in IAI isolates susceptibility dropped markedly in 2017.ConclusionColistin was a last resort antibiotics for empirical CR-Enterobacterales treatments, since especially the percentage of CR-K. pneumoniae was 30.0% of all IAI, UTI and RTI isolates, with an incidence of 24.8% CR strains, of which 88.6% were susceptible to colistin. Also other analyzed CR-Enterobacterales showed colistin susceptibilities of ≥80.0%. However, resistance rates of IAI derived CR-K. pneumoniae and CR-E. coli, and CR-K. pneumoniae UTI isolates to colistin increased between 2015 and 2017, which should further be closely monitored.

Results from the Survey of Antibiotic Resistance (SOAR) 2015-17 in Pakistan: data based on CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints.

To determine antibiotic susceptibility of community-acquired respiratory tract infection (CA-RTI) isolates of Streptococcus pneumoniae and Haemophilus influenzae collected in 2015-17 from Pakistan. MICs were determined by CLSI broth microdilution and susceptibility was assessed using CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints. A total of 94 S. pneumoniae and 122 H. influenzae isolates were collected. Susceptibility to penicillin was noted in 23.4% of the S. pneumoniae isolates by CLSI oral/EUCAST low-dose IV breakpoints, although by CLSI IV and EUCAST high-dose breakpoints all isolates were characterized as susceptible. Susceptibility to trimethoprim/sulfamethoxazole (10.6%), macrolides (33%) and cefaclor (28.7%) was low but higher susceptibility was observed to ceftriaxone (100%), amoxicillin and amoxicillin/clavulanic acid (98.9%), cefuroxime (oral, 97.9%), cefpodoxime (96.8%), fluoroquinolones (93.6%-96.8%) and cefdinir (76.6%) by CLSI breakpoints. However, using EUCAST breakpoints, susceptibility to cefpodoxime (70.2%) and cefuroxime (oral, 61.7%) was reduced. H. influenzae isolates were almost all β-lactamase negative (96.7%). Using CLSI breakpoints, ≥93.4% of isolates were susceptible to all antibiotics tested except fluoroquinolones (75.4%-77.1%) and trimethoprim/sulfamethoxazole (41%). The proportion of isolates susceptible using EUCAST breakpoints was similar or identical for penicillins, trimethoprim/sulfamethoxazole and the cephalosporins that have EUCAST breakpoints; the proportion of isolates susceptible using EUCAST breakpoints was similar or identical to that using CSLI breakpoints except for cefuroxime (oral), where only 1.6% of isolates were considered susceptible. Susceptibility of H. influenzae to fluoroquinolones was also lower by EUCAST breakpoints (33.6%-34.4%). The application of different EUCAST breakpoints for low and higher doses for some of the antibiotics (amoxicillin, amoxicillin/clavulanic acid, ampicillin, penicillin, ceftriaxone, clarithromycin, erythromycin, levofloxacin and trimethoprim/sulfamethoxazole) allowed, for the first time in a SOAR study, the effect of raising the dosage on susceptibility to be quantified. Antibiotic susceptibility in these important respiratory tract pathogens varied in Pakistan based on different breakpoints. These data are important for empirical therapy choices in the treatment of CA-RTIs.

Results from the Survey of Antibiotic Resistance (SOAR) 2016-18 in Vietnam, Cambodia, Singapore and the Philippines: data based on CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints.

To determine antibiotic susceptibility of Streptococcus pneumoniae and Haemophilus influenzae isolates collected from community-acquired respiratory tract infections (CA-RTIs) in 2016-18 in four Asian countries. MICs were determined by CLSI broth microdilution and susceptibility was assessed using CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints. In total, 260 S. pneumoniae and 258 H. influenzae isolates were tested. Pneumococci from Vietnam (n = 161) were the least susceptible, with rates of susceptibility >90% for fluoroquinolones by CLSI breakpoints, ∼60% for amoxicillin, amoxicillin/clavulanic acid and ceftriaxone but <14% for most other agents. Pneumococcal isolates from Cambodia (n = 48) and Singapore (n = 34) showed susceptibilities ranging from ∼30% for trimethoprim/sulfamethoxazole and oral penicillin to 100% for fluoroquinolones. Among isolates of H. influenzae from Cambodia (n = 30), the Philippines (n = 59) and Singapore (n = 80), rates of susceptibility using CLSI breakpoints were >90% for amoxicillin/clavulanic acid, cephalosporins [except cefaclor in Singapore (77.5%)], macrolides and fluoroquinolones; for isolates from Vietnam (n = 89) the rates of susceptibility were >85% only for amoxicillin/clavulanic acid (95.5%), ceftriaxone (100%) and macrolides (87.6%-89.9%). Susceptibility to other antibiotics ranged from 7.9% (trimethoprim/sulfamethoxazole) to 57.3%-59.6% (fluoroquinolones) and 70.8% (cefixime). The application of different EUCAST breakpoints for low and higher doses for some of the antibiotics (amoxicillin, amoxicillin/clavulanic acid, ampicillin, penicillin, ceftriaxone, clarithromycin, erythromycin, levofloxacin and trimethoprim/sulfamethoxazole) allowed, for the first time in a SOAR study, the effect of raising the dosage on susceptibility to be quantified. A limitation of the study was the small sample sizes and only one or two sites participating per country; however, since susceptibility data are scarce in some of the participating countries any information concerning antibiotic susceptibility is of value. Antibiotic susceptibility varied across countries and species, with isolates from Vietnam demonstrating the lowest susceptibility. Knowledge of resistance patterns can be helpful for clinicians when choosing empirical therapy options for CA-RTIs.

Results from the Survey of Antibiotic Resistance (SOAR) 2015–17 in Latin America (Argentina, Chile and Costa Rica): data based on CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints

To determine antibiotic susceptibility of Streptococcus pneumoniae and Haemophilus influenzae isolates from community-acquired respiratory tract infections (CA-RTIs) collected in 2015-17 from Argentina, Chile and Costa Rica. MICs were determined by CLSI broth microdilution and susceptibility was assessed using CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints. A total of 170 S. pneumoniae and 218 H. influenzae isolates were collected at five centres in Argentina, Chile and Costa Rica in 2015-17. Small S. pneumoniae isolate numbers from Costa Rica (n = 2) meant that these could only be included in the penicillin susceptibility analysis; they were excluded from further country analyses. Around one-third of pneumococcal isolates from Argentina and two-thirds from Chile were non-susceptible to penicillin by CLSI oral or EUCAST low-dose IV breakpoints, but most (≥89%) were susceptible by CLSI IV or EUCAST high-dose breakpoints. Amongst pneumococci from Argentina, about 80% or more were susceptible to most other antibiotics except cefaclor (all breakpoints), cefixime (PK/PD breakpoints), cefuroxime (EUCAST breakpoints) and trimethoprim/sulfamethoxazole (CLSI and PK/PD breakpoints). S. pneumoniae isolates from Chile showed significantly lower susceptibility (P < 0.05) using CLSI breakpoints compared with those from Argentina for many of the antibiotics tested. Among isolates of H. influenzae from Latin America, more than 90% were susceptible to amoxicillin/clavulanic acid (high dose), cefixime, cefpodoxime, ceftriaxone and fluoroquinolones, irrespective of the breakpoints used. The application of different EUCAST breakpoints for low and higher doses for some of the antibiotics (amoxicillin, amoxicillin/clavulanic acid, ampicillin, penicillin, ceftriaxone, clarithromycin, erythromycin, levofloxacin and trimethoprim/sulfamethoxazole) allowed, for the first time in a SOAR study, the effect of raising the dosage on susceptibility to be quantified. Antibiotic susceptibility of H. influenzae isolates was generally high in the Latin American countries studied; however, susceptibility profiles varied for S. pneumoniae by country and depending on the breakpoints used, especially for cefaclor. These factors are important in decision making for empirical therapy of bacterial infections.

Results from the Survey of Antibiotic Resistance (SOAR) 2015-17 in the Middle East (Kuwait, Lebanon and Saudi Arabia): data based on CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints.

To determine antibiotic susceptibility of Streptococcus pneumoniae and Haemophilus influenzae isolates from community-acquired respiratory tract infections (CA-RTIs) collected in 2015-17 from Kuwait, Lebanon and Saudi Arabia. MICs were determined by CLSI broth microdilution and susceptibility was assessed using CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints. A total of 139 S. pneumoniae isolates were collected from four centres in Kuwait, Lebanon and Saudi Arabia in 2015-17 and 55 H. influenzae isolates were collected and analysed from Saudi Arabia over the same time period. Pneumococci from all three countries were commonly non-susceptible to penicillin based on CLSI oral or low-dose IV penicillin using EUCAST breakpoints (39% in Kuwait to 57.1% in Lebanon) but by CLSI IV and EUCAST high-dose breakpoints most isolates were susceptible (∼90% in Kuwait and Saudi Arabia, and 100% in Lebanon). Isolates from Lebanon were highly susceptible to most other antibiotics (>90%) except cefaclor, oral cefuroxime and cefpodoxime (EUCAST breakpoints only). Overall, susceptibility was significantly lower in Kuwait and Saudi Arabia than Lebanon. Although all H. influenzae isolates (Saudi Arabia only) were β-lactamase negative, 3.6% and 12.7% were ampicillin resistant by CLSI and EUCAST breakpoints, respectively. Otherwise susceptibility was high in H. influenzae. The application of different EUCAST breakpoints for low and higher doses for some of the antibiotics (amoxicillin, amoxicillin/clavulanic acid, ampicillin, penicillin, ceftriaxone, clarithromycin, erythromycin, levofloxacin and trimethoprim/sulfamethoxazole) allowed, for the first time in a SOAR study, the effect of raising the dosage on susceptibility to be quantified. Relatively low antibiotic susceptibility was observed in S. pneumoniae from Kuwait and Saudi Arabia in contrast to Lebanon, where rates of susceptibility were generally higher. Isolates of H. influenzae from Saudi Arabia were susceptible to most antibiotics. These factors are important in decision making for empirical therapy of CA-RTIs.

Results from the Survey of Antibiotic Resistance (SOAR) 2016-17 in Ukraine: data based on CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints.

To determine antibiotic susceptibility of Streptococcus pneumoniae and Haemophilus influenzae isolates from community-acquired respiratory tract infections (CA-RTIs) collected in 2016-17 from Ukraine. MICs were determined by CLSI broth microdilution and susceptibility was assessed using CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints. A total of 177 viable clinical isolates, including 78 S. pneumoniae and 99 H. influenzae, were collected. Overall, ∼98% of S. pneumoniae isolates were susceptible to penicillin by CLSI IV or EUCAST high-dose breakpoints and 73.1% were susceptible by CLSI oral or EUCAST low-dose IV breakpoints. Susceptibility rates of 76.9%-100% were observed for most antibiotics by all breakpoints except trimethoprim/sulfamethoxazole (41%-69.2%) and cefaclor, which showed the greatest difference between breakpoints: 0% by EUCAST, 28.2% by PK/PD and 73.1% by CLSI. All S. pneumoniae isolates were susceptible to amoxicillin/clavulanic acid by CLSI and PK/PD breakpoints. H. influenzae isolates were almost all β-lactamase negative (90.9%). One isolate was β-lactamase negative and ampicillin resistant (BLNAR) by CLSI and four isolates were BLNAR by EUCAST criteria. Susceptibility of isolates was high (≥90.9%) by CLSI breakpoints for all antibiotics tested except trimethoprim/sulfamethoxazole (61.6%). Susceptibility using EUCAST breakpoints was similar for ampicillin (90.9%) and amoxicillin/clavulanic acid (95%) but was low for cefuroxime (oral), where only 10.1% of isolates were susceptible. All S. pneumoniae and H. influenzae isolates were susceptible to the fluoroquinolones by all breakpoints. Susceptibility to ceftriaxone was also 100% for H. influenzae and ≥91% for S. pneumoniae isolates by all breakpoints. The application of different EUCAST breakpoints for low and higher doses for some of the antibiotics (amoxicillin, amoxicillin/clavulanic acid, ampicillin, penicillin, ceftriaxone, clarithromycin, erythromycin, levofloxacin and trimethoprim/sulfamethoxazole) allowed, for the first time in a SOAR study, the effect of raising the dosage on susceptibility to be quantified. Antibiotic susceptibility in these respiratory tract pathogens was generally high in Ukraine. These data are important for empirical therapy choices in the treatment of CA-RTIs.

Results from the Survey of Antibiotic Resistance (SOAR) 2015-18 in Tunisia, Kenya and Morocco: data based on CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints.

To determine antibiotic susceptibility of community-acquired respiratory tract infection (CA-RTI) isolates of Streptococcus pneumoniae and Haemophilus influenzae collected in 2015-18 from Tunisia, Kenya and Morocco. MICs were determined by CLSI broth microdilution and susceptibility was assessed using CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints. S. pneumoniae isolates from Tunisia (n = 79), Kenya (n = 44) and Morocco (n = 19) and H. influenzae isolates (n = 74) from Tunisia only were collected and analysed. Low antibiotic susceptibility was observed in S. pneumoniae from Tunisia, with >90% susceptible only to the fluoroquinolones (all breakpoints), penicillin (CLSI IV and EUCAST high-dose) and ceftriaxone (CLSI, EUCAST high-dose and PK/PD breakpoints). In addition, isolate susceptibility in Kenya was >90% to amoxicillin and amoxicillin/clavulanic acid (CLSI and PK/PD breakpoints). Antibiotic activity was highest in Morocco, where ≥89.5% of pneumococci were susceptible to most antibiotics, excluding trimethoprim/sulfamethoxazole (68.4% by CLSI or PK/PD and 79%-84.2% by EUCAST), macrolides (79%-84.2% by all breakpoints) and cefaclor (0% by EUCAST and 52.6% by PK/PD). The majority (≥86.5%) of H. influenzae isolates from Tunisia were susceptible to most antibiotics by all available breakpoints, except ampicillin and amoxicillin (almost one-third were β-lactamase positive), trimethoprim/sulfamethoxazole (51.4%-56.8%), cefaclor (1.4% by PK/PD), cefuroxime (4.1% by EUCAST), macrolides (1.4%-2.7% by PK/PD) and cefdinir (66.2% by PK/PD). The application of different EUCAST breakpoints for low and higher doses for some of the antibiotics (amoxicillin, amoxicillin/clavulanic acid, ampicillin, penicillin, ceftriaxone, clarithromycin, erythromycin, levofloxacin and trimethoprim/sulfamethoxazole) allowed, for the first time in a SOAR study, the effect of raising the dosage on susceptibility to be quantified. Low antibiotic susceptibility was observed in S. pneumoniae from Tunisia, but susceptibility was higher in isolates from Kenya and highest in those from Morocco. H. influenzae from Tunisia were highly susceptible to most antibiotics. These factors are important in decision making for empirical therapy of CA-RTIs.

Results from the Survey of Antibiotic Resistance (SOAR) 2015-17 in Turkey: data based on CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints.

To determine antibiotic susceptibility of Streptococcus pneumoniae and Haemophilus influenzae isolates from community-acquired respiratory tract infections (CA-RTIs) collected in 2015-17 from Turkey. MICs were determined by CLSI broth microdilution and susceptibility was assessed using CLSI, EUCAST (dose-specific) and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints. A total of 179 S. pneumoniae and 239 H. influenzae isolates were collected. Few (27.9%) pneumococci were penicillin susceptible by CLSI oral or EUCAST low-dose breakpoints, but by EUCAST high-dose or CLSI IV breakpoints 84.4% were susceptible. The most active antibiotics (excluding penicillin IV) by CLSI breakpoints were fluoroquinolones (98.9% of isolates susceptible), ceftriaxone (83.2%), amoxicillin (78.8%) and amoxicillin/clavulanic acid (78.8%). Pneumococcal susceptibility to amoxicillin and amoxicillin/clavulanic acid was lower using EUCAST low-dose breakpoints (49.7%), although susceptibility increased when using EUCAST high-dose (57.0%-58.1%) and PK/PD (78.8%-87.7%) breakpoints. Twenty-three H. influenzae isolates were β-lactamase positive, with 11 characterized as β-lactamase negative and ampicillin resistant following EUCAST criteria and 5 by CLSI criteria. Generally antibiotic susceptibility was high using CLSI breakpoints: ≥92.9% for all antibiotics except ampicillin (87% by CLSI and EUCAST breakpoints) and trimethoprim/sulfamethoxazole (67.4% and 72% by CLSI and EUCAST breakpoints, respectively). Susceptibility using EUCAST breakpoints (where these are published) was similar, except for cefuroxime (oral) with 3.8% of isolates susceptible. PK/PD breakpoints indicated low susceptibility to macrolides (5.9%-10%) and cefaclor (13%). The application of different EUCAST breakpoints for low and higher doses for some of the antibiotics (amoxicillin, amoxicillin/clavulanic acid, ampicillin, penicillin, ceftriaxone, clarithromycin, erythromycin, levofloxacin and trimethoprim/sulfamethoxazole) allowed, for the first time in a SOAR study, the effect of raising the dosage on susceptibility to be quantified. Antibiotic susceptibility of S. pneumoniae was generally low, which is in keeping with evidence of inappropriate and high antibiotic use in Turkey. H. influenzae susceptibility was high. These data are important for empirical therapy of CA-RTIs.

Emergence of Terbinafine Resistant Trichophyton mentagrophytes in Iran, Harboring Mutations in the Squalene Epoxidase (SQLE) Gene.

IntroductionTrichophyton mentagrophytes and T. interdigitale are important causative agents of superficial mycoses, demonstrating emergent antifungal drug resistance. We studied the antifungal susceptibility profiles in Iranian isolates of these two species.MethodsA total of 96 T. interdigitale and 45 T. mentagrophytes isolates were subjected to molecular typing by ribosomal ITS region. Antifungal susceptibility profiles for terbinafine, griseofulvin, clotrimazole, efinaconazole, luliconazole, amorolfine and ciclopirox were obtained by CLSI broth microdilution method. The squalene epoxidase (SQLE) gene was subjected to sequencing for mutations, if any, in isolates exhibiting elevated MICs for terbinafine.ResultsLuliconazole and efinaconazole showed the lowest MIC values against T. mentagrophytes and T. interdigitale isolates. There were five isolates with terbinafine MICs ≥32 µg/mL in our sample. They belonged to T. mentagrophytes type VIII and harbored two alternative SQLE gene sequence variants, leading to Phe397Leu and Ala448Thr or Leu393Ser and Ala448Thr substitutions in the enzyme. All terbinafine resistant strains could be inhibited by luliconazole and efinaconazole.ConclusionThis study documented a step in the global spread of resistance mechanisms in T. mentagrophytes. However, treatment alternatives for resistant isolates were available.

In Vitro Activity of Eravacycline against Gram-Negative Bacilli Isolated in Clinical Laboratories Worldwide from 2013 to 2017.

Eravacycline is a novel, fully synthetic fluorocycline antibiotic developed for the treatment of serious infections, including those caused by multidrug-resistant (MDR) pathogens. Here, we evaluated the in vitro activities of eravacycline and comparator antimicrobial agents against a global collection of frequently encountered clinical isolates of Gram-negative bacilli. The CLSI broth microdilution method was used to determine MIC data for isolates of Enterobacterales (n = 13,983), Acinetobacter baumannii (n = 2,097), Pseudomonas aeruginosa (n = 1,647), and Stenotrophomonas maltophilia (n = 1,210) isolated primarily from respiratory, intra-abdominal, and urinary specimens by clinical laboratories in 36 countries from 2013 to 2017. Susceptibilities were interpreted using both CLSI and EUCAST breakpoints. Multidrug-resistant (MDR) isolates were defined by resistance to agents from ≥3 different antimicrobial classes. The MIC90s ranged from 0.25 to 1 μg/ml for Enterobacteriaceae and were 1 μg/ml for A. baumannii and 2 μg/ml for S. maltophilia, Proteus mirabilis, and Serratia marcescens Eravacycline's potency was up to 4-fold greater than that of tigecycline against genera/species of Enterobacterales, A. baumannii, and S. maltophilia The MIC90s for five of six individual genera/species of Enterobacterales and A. baumannii were within 2-fold of the MIC90s for their respective subsets of MDR isolates, while the MDR subpopulation of Klebsiella spp. demonstrated 4-fold higher MIC90s. Eravacycline demonstrated potent in vitro activity against the majority of clinical isolates of Gram-negative bacilli, including MDR isolates, collected over a 5-year period. This study further underscores the potential benefit of eravacycline in the treatment of infections caused by MDR Gram-negative pathogens.

In Vitro Activity of Eravacycline against Gram-Positive Bacteria Isolated in Clinical Laboratories Worldwide from 2013 to 2017.

Eravacycline is a novel, fully synthetic fluorocycline antibiotic being developed for the treatment of serious infections, including those caused by resistant Gram-positive pathogens. Here, we evaluated the in vitro activities of eravacycline and comparator antimicrobial agents against a recent global collection of frequently encountered clinical isolates of Gram-positive bacteria. The CLSI broth microdilution method was used to determine in vitro MIC data for isolates of Enterococcus spp. (n = 2,807), Staphylococcus spp. (n = 4,331), and Streptococcus spp. (n = 3,373) isolated primarily from respiratory, intra-abdominal, urinary, and skin specimens by clinical laboratories in 37 countries on three continents from 2013 to 2017. Susceptibilities were interpreted using both CLSI and EUCAST breakpoints. There were no substantive differences (a >1-doubling-dilution increase or decrease) in eravacycline MIC90 values for different species/organism groups over time or by region. Eravacycline showed MIC50 and MIC90 results of 0.06 and 0.12 μg/ml, respectively, when tested against Staphylococcus aureus, regardless of methicillin susceptibility. The MIC90 values of eravacycline for Staphylococcus epidermidis and Staphylococcus haemolyticus were equal (0.5 μg/ml). The eravacycline MIC90s for Enterococcus faecalis and Enterococcus faecium were 0.06 μg/ml and were within 1 doubling dilution regardless of the vancomycin susceptibility profile. Eravacycline exhibited MIC90 results of ≤0.06 μg/ml when tested against Streptococcus pneumoniae and beta-hemolytic and viridans group streptococcal isolates. In this surveillance study, eravacycline demonstrated potent in vitro activity against frequently isolated clinical isolates of Gram-positive bacteria (Enterococcus, Staphylococcus, and Streptococcus spp.), including isolates collected over a 5-year period (2013 to 2017), underscoring its potential benefit in the treatment of infections caused by common Gram-positive pathogens.

MIC distributions for amphotericin B, fluconazole, itraconazole, voriconazole, flucytosine and anidulafungin and 35 uncommon pathogenic yeast species from the UK determined using the CLSI broth microdilution method.

Epidemiological cut-off values and clinical interpretive breakpoints have been developed for a number of antifungal agents with the most common Candida species that account for the majority of infections due to pathogenic yeasts species. However, less-common species, for which susceptibility data are limited, are increasingly reported in high-risk patients and breakthrough infections. The UK National Mycology Reference Laboratory performs routine antifungal susceptibility testing of clinical yeast isolates submitted from across the UK. Between 2002 and 2016, >32 000 isolates representing 94 different yeast species were referred to the laboratory. Here we present antifungal susceptibility profiles generated over this period for amphotericin B, fluconazole, voriconazole, itraconazole, anidulafungin and flucytosine against 35 species of uncommon yeast using CLSI methodologies. MIC data were interpreted against epidemiological cut-off values and clinical breakpoints developed with Candida albicans, in order to identify species with unusually skewed MIC distributions that potentially indicate resistance. Potential resistance to at least one antifungal agent (>10% of isolates with MICs greater than the epidemiological cut-off or clinical breakpoint) was evidenced for 29/35 species examined here. Four species exhibited elevated MICs with all of the triazole antifungal drugs against which they were tested, and 21 species exhibited antifungal resistance to agents from at least two different classes of antifungal agent. This study highlights a number of yeast species with unusual MIC distributions and provides data to aid clinicians in deciding which antifungal regimens may be appropriate when confronted with infections with rarer yeasts.

Candida blankii: an emerging yeast in an outbreak of fungaemia in neonates in Delhi, India

ObjectiveOutbreaks of fungal sepsis due to emerging and rare multidrug-resistant Candida species are increasingly reported in health-care settings. We report an outbreak of fungaemia due to the rare multidrug-resistant yeast Candida blankii in an Indian neonatal unit. Materials and methodsBlood cultures grew C. blankii in nine neonates in the Neonatal Intensive Care Unit of a multispecialty hospital in Delhi during a period of 7 months. Isolates were identified by internal transcribed spacer and D1/D2 region sequencing. Antifungal susceptibility testing was performed by M27-A3 CLSI broth microdilution. To determine genetic relatedness among C. blankii isolates we undertook amplified fragment length polymorphism analysis and DNA sequencing using the Illumina NextSeq500 platform. ResultsCandida blankii fungaemia occurred at 2–3 postnatal days in nine low birthweight/very low birthweight neonates. All neonates were treated with fluconazole and four of the nine neonates died, resulting in a case fatality rate of 45%. Candida blankii was misidentified or not identified by automated identification systems. Fluconazole had higher geometric mean (GM) MICs (8 mg/L) than the other azoles. Also, anidulafungin (GM-MIC 2 mg/L) had high MICs. Genome sequencing confirmed transmission of genetically mostly indistinguishable strains. The C. blankii genome showed an altered 1,3-β-d-glucan synthase protein and several larger deletions in the echinocandin target FKS1 gene, suggesting potential for development of antifungal resistance. ConclusionsThe study emphasizes the emergence of a rare and uncommon yeast, C. blankii, with reduced susceptibility to one or more antifungal agents, in nosocomial fungaemia. Genomic insights of this rare yeast are reported using whole-genome sequence typing.

Study on Vulvovaginal Candidiasis: Clinical Epidemiology and &lt;i&gt;in vitro&lt;/i&gt; Susceptibility of Pathogenic Yeasts in China

Background: Vulvovaginal candidiasis (VVC) is a common vaginal infection. We aim to investigate the clinical epidemiology of VVC and the in vitro antifungal susceptibility of Candida spp. collected from different regions of China, so as to provide a guideline for the appropriate use of antifungals in clinical settings. Methods: Candida isolates from VVC patients and questionnaires were collected from 12 hospitals across the China from September 2017 to March 2018. Species were identified by germ tube test, clamydospore formation, CHROMagar medium and DNA sequencing. Susceptibility to fluconazole (FLC), itraconazole (ITC), voriconazole (VOC), posaconazole (POS), miconazole (MIC), econazole (ECO), clotrimazole (CLZ), nystatin (NYS), amphotericin B (AMB), caspofungin (CAS), and terbinafine (TBF) was determined using the CLSI broth microdilution method (M27-E4). The in vitro data were also evaluated with updated clinical breakpoints and epidemiological cut-off values. Findings: A total of 602 cases were enrolled in this study, of which 253 (42%) were uncomplicated VVC and 349 (58%) were complicated. Among complicated VVC, 26% were RVVC. The subjects were between 16 and 64 years of age, of which 60% were between 25 and 35 years of age. A total of 543 strains were isolated from these VVC patients. The most commonly identified species was C.albicans (84.71%), followed by C.glabrata (8.66%), Meyerozyma caribbica (1.29%), Pichia guilliermondii (1.29%), C.tropicalis (0.92%), Pichia kudriavzevii (0.92%), C.parapsilosis (0.55%), Candida nivariensis (0.55%), Issatchenkia orientailis (0.55%) and less common yeasts(0.55%). The overall susceptibility rates of C.albicans to FLC, VOC and CAS were all greater than 80%, and the resistance rates were less than 10%. Most of C.albicans isolates were WT to ITC (86%), POS (95%) and AMB (98%). Most of C.glabrata (98%) were dose-dependently susceptible to FLC. All of C.glabrata isolates were WT to both ITC and AMB, while most were WT to both VOC (85%) and POS (91.5%).The proportion of NWT strains to FLC in RVVC was much higher than that in other types of VVC(33% vs . 23%, P <0.05). The proportions of WT strains to ITC in complicated VVC and RVVC were all over 80%, which were much higher than that to FLC( P <0.01). CLZ showed the lowest MIC 90 (0.06ug/ml)against C.albicans, and the MICs of CLZ among non-albicans Candida (NAC) were all <2ug/ml. Interpretation: VVC was more frequent in women of childbearing age. C.albicans (84.71%) was still the predominant species of VVC in China, while C.glabrata (56.6%) was the main species in NAC. Most C.albicans strains isolated from uncomplicated VVC in different regions of China were still susceptible to the commonly used azoles, including FLC and ITC, which could be used as empirical treatment. However, FLC may not be the first choice for the treatment of complicated VVC, especially RVVC. In both cases, ITC was more appropriate treatment. CLZ could be recommended as a good choice of topical drugs for VVC. As for new drugs, POS is promising for the refractory cases. Funding Statement: This study was supported by National Science and Technology Major Project (2018ZX10734404), the CAMS Initiative for Innovative Medicine (2016-I2M-3-021), National Natural Science Foundation of China (Grant No. 81573059), the Basical Scientific Research Fund Projects of Chinese Academy of Medical Sciences (No. 2018PT31013) and Nanjing Clinical Medicine Research Center Project (No.2019060001). Declaration of Interests: All authors declare that they have no conflicts of interest. Ethics Approval Statement: The study has been approved by the ethics committee of the hospital, and all patients have signed informed consent (version number and date:1.0, 2017.02.16).

Molecular Identification, Genotyping, Phenotyping, and Antifungal Susceptibilities of Medically Important Trichosporon, Apiotrichum, and Cutaneotrichosporon Species.

Recently, Trichosporon taxonomy has been reevaluated and new genera of the Trichosporonaceae family have been described. Here, 26 clinical isolates were submitted for identification via sequencing of the intergenic space 1 (IGS1) region, genotyping, and investigation of virulence factors. Antifungal susceptibility was determined using the CLSI broth microdilution method for fluconazole (FLC), itraconazole (ITC), and amphotericin B (AMB). Of these, 24 isolates were identified, including 12 T. asahii, 4 T. inkin, 3 T. faecale, 1 T. coremiiforme, 1 T. japonicum, 2 Cutaneotrichosporon dermatis (formerly T. dermatis), and 1 Apiotrichum mycotoxinivorans (formerly T. mycotoxinivorans). Species-level identification of 2 isolates was not successful; they were described as Trichosporon sp. We observed optimal colonial development at 35-40°C. Lipase was the major extracellular enzyme produced (100%); caseinase was not produced (0%). Biofilms were produced by all isolates (classified as low). High AMB minimum inhibitory concentration (MIC) was observed, with all strains resistant. Fluconazole was the most active drug among the antifungals tested. However, high MICs for FLC were observed in C. dermatis and A. mycotoxinivorans species, which also showed resistance toITC and AMB. This study, conducted in the Northern region of Brazil, identified 5 Trichosporon species along with C. dermatis and A. mycotoxinivorans and demonstrated their pathogenic potential through their ability to produce important virulence factors. This may contribute to our understanding of the epidemiology and factors related to the pathogeneses of species in the Trichosporonaceae family.

1482. Microbiological Analysis from a Phase II Study Evaluating Gepotidacin (GSK2140944) in the Treatment of Uncomplicated Urinary Tract Infections

BackgroundGepotidacin (GEP), a first in class novel triazaacenaphthylene bacterial topoisomerase inhibitor, inhibits bacterial replication and has in vitro activity against key pathogens, including drug-resistant strains, associated with a range of infections.MethodsThis phase IIa single-center study evaluated the safety, tolerability, pharmacokinetics, and efficacy of oral GEP 1,500 mg BID for 5 days in female subjects with acute cystitis. Clean catch mid-stream urine specimens were obtained for quantitative culture by standard methods. Susceptibility testing by CLSI broth microdilution and gradient diffusion (fosfomycin only) was conducted. Inclusion in the microbiological intent-to-treat population (micro-ITT) required growth of a qualifying baseline uropathogen (≥ 105 CFU/mL). Microbiological success was defined as culture-confirmed eradication (no growth, <103 CFU/mL) of the qualifying baseline uropathogen.ResultsOf 22 participants, 8 (36%) had a baseline qualifying uropathogen (5 E. coli, 1 S. saprophyticus, 1 K. pneumoniae, and 1 C. koseri) and were included in the micro-ITT. GEP MICs against the 8 qualifying uropathogens ranged from 0.06 to 4 µg/mL. Two E. coli isolates were multidrug-resistant (defined as resistance to ≥3 antibiotic classes) due to resistance to ampicillin, trimethoprim-sulfamethoxazole and ciprofloxacin/levofloxacin or cefazolin. One additional E. coli isolate was ampicillin-resistant. Of the 8 participants in the micro-ITT, 7 (88%), and 6 (75%) were microbiological successes at the Test of Cure (TOC) and Follow-up Visits, respectively. The one microbiological failure at TOC (E. coli) was due to an unreportable (out of stability) urine specimen. For the 4 participants with available steady-state PK, qualifying Enterobacteriaceae uropathogens and who were microbiological successes at TOC, plasma fAUC24h/MICs ranged from 7 to 90.5 and urine AUC24h/MICs from 1292 to 121,698. The participant with the lowest plasma fAUC/MIC (7) and urine AUC24h/MIC (1292) had a K. pneumoniae with a gepotidacin MIC of 4 µg/mL.ConclusionThis first report of microbiological efficacy in the treatment of acute cystitis supports further clinical study of GEP as a first-in-class, novel mechanism of action antibacterial.Disclosures All authors: No reported disclosures.

706. In Vitro Activity of Ceftazidime–Avibactam and Comparator Agents Against MDR Enterobacteriaceae and Pseudomonas aeruginosa Collected in Latin America During the ATLAS Global Surveillance Program 2016–2017

BackgroundCeftazidime–avibactam (CAZ-AVI) is a β-lactam/non-β-lactam β-lactamase inhibitor combination that can inhibit class A, C and some class D β-lactamases. Resistance caused by these β-lactamases often results in multidrug-resistance (MDR). This study evaluated the in vitro activity of CAZ-AVI and comparators against MDR Enterobacteriaceae and Pseudomonas aeruginosa isolates collected from patients in Latin America.MethodsNonduplicate clinical isolates were collected in 2016–2017 in 6 countries in Latin America. Susceptibility testing was performed using CLSI broth microdilution and interpreted using CLSI 2019 and FDA (tigecycline) breakpoints. MDR was defined as nonsusceptible (NS) (intermediate or resistant) to ≥3 of 7 sentinel drugs: amikacin, aztreonam, cefepime, levofloxacin, colistin, meropenem, and piperacillin–tazobactam.ResultsThe activity of CAZ-AVI and comparators against all isolates and MDR subsets is shown in the table. MDR rates ranged from 28.4% among E. cloacae to 41.5% among K. pneumoniae. CAZ-AVI was active against >97% of Enterobacteriaceae isolates and maintained activity against >92% of MDR isolates of the examined species. No other tested drug consistently exceeded this activity. Among P. aeruginosa, CAZ-AVI was active against 87% of all isolates and 63% of MDR isolates; only colistin was more active. The two most common MDR phenotypes among Enterobacteriaceae were (1) NS to aztreonam, cefepime, and levofloxacin (n = 580, 41% of all MDR Enterobacteriaceae; 100% susceptible to CAZ-AVI) and (2) NS to aztreonam, cefepime, levofloxacin, and piperacillin–tazobactam (n = 301, 21% of all MDR isolates; 99.7% susceptible to CAZ-AVI). The two most common MDR phenotypes among P. aeruginosa were (1) NS to all sentinel drugs except colistin (n = 154, 33% of all MDR isolates; 30.5% susceptible to CAZ-AVI) and (2) NS to all drugs except colistin and amikacin (n = 97, 21% of all MDR isolates; 70.1% susceptible to CAZ-AVI).ConclusionThese in vitro data suggest that CAZ-AVI can be an effective treatment option for infections caused by MDR Enterobacteriaceae and P. aeruginosa collected in Latin America. Disclosures All authors: No reported disclosures.