Gram-positive Clinical Isolates Research Articles

Current Status of Drug-resistant Patterns of Gram-positive Clinical Isolates Collected from Renowned Diagnostic Centers of Dhaka, Bangladesh

Background: Antimicrobial resistance is a serious concern and life threat in public health globally. Gram-positive clinical isolates are one of the leading etiological agents showing drug resistance traits. This study aimed to detect the antimicrobial resistance pattern of clinically isolated Gram-positive bacterial isolates collected from various renowned diagnostic centers of Dhaka city, Bangladesh. Methods: A laboratory-based cross-sectional study was conducted at the Microbiological Laboratory of the Department of Microbiology, Stamford University Bangladesh. A total of 104 clinical specimens (wound swab, pus, blood, urine, ear discharge, nasal swab, sputum, nipple discharge, breast milk, catheter tip, umbilical swab, and throat swab) from different age groups were collected from some renowned diagnostic centers of Dhaka city for analyzing the cultural and drug sensitivity patterns from January 2023 to April 2023. According to the study plan, only the Gram-positive bacteria were collected and transported to the laboratory of the Department of Microbiology, Stamford University Bangladesh following WHO guidelines, and the antimicrobial susceptibility tests were carried out by Kirby–Bauer disk diffusion method and the results were interpreted as per CLSI guidelines, 2022. Results: This study highlights the presence of Staphylococcus aureus (65.4%), Streptococcus spp. (23.1%), and Enterococcus spp. (11.5%) as causative agents of Gram-positive bacterial infections from overall 104 clinical specimens. Most of our isolates were found multidrug-resistant. For S. aureus isolates, cefixime (100%); for Streptococcus spp., doxycycline (95.83%); and for Enterococcus spp., amoxicillin (100%), cefixime (100%), colistin (100%), and cotrimoxazole (100%) were found to be the most ineffective drug when compared to other antibiotics. Conclusion: Our study portrayed the remarkable antibiotic resistance feature of Gram-positive bacterial isolates which is a matter of public health concern. It is necessary to carry out a continuous assessment of antibiotic sensitivity patterns of resistant Gram-positive bacteria; otherwise, it will become an uncontrollable problem not only in Bangladesh but also worldwide in the near future.

Antibacterial activity of Hypericum perforatum L. (St. John’s wort) extracts against Gram-positive bacteria and characterisation of its secondary metabolites

This study aimed to determine the secondary metabolite profiles and antibacterial activity of H. perforatum L extracts against Gram-positive clinical isolates. The plant materials (Sample A and Sample B) were macerated with n-hexane, ethyl acetate and methanol (MeOH). The antibacterial activitiy of plant extracts and routinely used antibiotics were tested against Gram-positive bacteria. The secondary metabolite profiles of Sample A were determined by LC-Q-TOF-MS. The MIC values for n-hexane and ethyl acetate extracts of Sample A were lower than the susceptibility breakpoints of most broad-spectrum antibiotics (e.g. vancomycin, teicoplanin and linezolid) in a certain proportion of Gram-positive bacteria. The n-hexane extract of Sample A showed good antibacterial activity with MICs lower than the susceptibility breakpoint of teicoplanin in 58% of coagulase-negative staphylococci. The n-hexane and ethyl acetate extracts of Sample A had rich phloroglucinol constituents. The n-hexane and ethyl acetate extracts of Sample A could be alternative antibacterial agents against Gram-positive bacteria.

Antibiogram Pattern and Biofilm for the Potential of Gram-Positive Clinical Isolates from Karachi

Antibiogram Pattern and Biofilm for the Potential of Gram-Positive Clinical Isolates from Karachi

Comparative Activity of Lipoglycopeptide Antibiotics Against Gram-Positive Bacteria

Lipoglycopeptide antibiotics are semi-synthetic derivatives of glycopeptides and are characterized by a pronounced bactericidal activity against gram-positive pathogens. The aim of the study was comparative assessment of the sensitivity of gram-positive clinical isolates to lipoglycopeptide antibiotics (telavancin, dalbavancin, oritavancin). The following isolates were included in the work: methicillin-resistant Staphylococcus aureus (MRSA, n=780), methicillin-resistant coagulase-negative Staphylococcus spp. (MRCoNS, n=163), and vancomycin-resistant Enterococcus faecium (VREf, n=93). Serial dilutions were used to assess sensitivity with the addition of 0.002% polysorbate 80 to the medium. Lipoglycopeptides showed more pronounced antibacterial activity against MRSA compared to vancomycin, teicoplanin, and daptomycin, and had a MIC₅₀/MIC₉₀ (µg/ml): for telavancin — 0.06 /0.125, for dalbavancin — 0.016/0.06, and for oritavancin — 0.06/0.125. A trend towards an increase in the MIC of lipoglycopeptides and daptomycin was established in MRSA with the MIC of 2 µg/ml for vancomycin, the proportion of which was 13%. For MRCoNS, MIC₅₀ and MIC₉₀ of lipoglycopeptides did not exceed 0.06 µg/ml and 0.125 µg/ml, respectively. Oritavancin showed strong activity against VREf at MIC range of 0.03 µg/ml to 0.5 µg/ml, and at MIC₉₀ of 0.25 µg/ml. Thus, lipoglycopeptide antibiotics are a plausible alternative to vancomycin and daptomycin; they are characterized by pronounced activity and can be used to treat severe forms of staphylococcal infections.

662. In vitro antibacterial activity of contezolid compared to linezolid and vancomycin in clinical isolates from China

Abstract Background Linezolid and vancomycin are insufficient in the treatment of drug-resistant Gram-positive bacteria due to adverse drug reactions and drug resistance, and new antibiotics are needed, especially for patients with myelosuppression and vancomycin-resistant Enteroccocus (VRE) infection. Contezolid (CZD) is a novel oral oxazolidinone with potent activity against Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) and VRE. We evaluate the in vitro antibacterial activity of contezolid compared to linezolid and vancomycin in Gram-positive clinical isolates. Methods 176 clinical isolates were obtained from 176 sterile body fluids from patients at 3 tertiary care hospitals in China, and the minimal inhibitory concentrations (MICs) of contezolid, linezolid and vancomycin determined by broth microdilution assay. Results Contezolid exhibits excellent antibacterial activity against prevalent Gram-positive bacteria, Staphylococcus spp. and Enterococcus spp., including methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant and coagulase-negative Staphylococcus (MRCNS), and vancomycin-resistant Enterococcus (VRE). MIC90 values of contezolid were 2 mg/L for all MRSA and VRE isolates and 1 mg/L for MRCNS isolates. The antibacterial activity of contezolid against Staphylococcus spp., including S. aureus, was essentially similar to linezolid, and slightly higher than or similar to vancomycin. Antibacterial activity of contezolid against Enterococcus, including VRE, was similar to linezolid, while being slightly lower than for vancomycin in vancomycin-susceptible isolates. Consistent with the shared antibacterial mode of action, bacterial strains resistant to linezolid were cross-resistant to contezolid. Table 1.Antimicrobial susceptibility testing results of clinical bacterial strains (MICs, mg/L) Conclusion Contezolid, a novel oxazolidinone drug, exhibits potent in vitro antibacterial activity against clinical isolates of common Gram-positive pathogens, including multidrug-resistant (MDR) Gram-positive bacteria, MRSA, MRCNS, and VRE. Contezolid has antibacterial activity similar to standard-of-care antibiotics linezolid and vancomycin. Results suggest that contezolid can play an important role in treatment of MDR Gram-positive bacterial infections. Figure 1.Distribution of MICs of CZD or LZD against 48 strains of MRSAFigure 2.Distribution of MICs of CZD or LZD against 29 strains of MRCNSFigure 3.Distribution of MICs of CZD or LZD against 17 strains of VRE Disclosures All Authors: No reported disclosures.

1714. In Vitro Activity of Tebipenem Against Clinically Significant Gram-Positive Bacteria Isolated from Patients with Cancer

Abstract Background Carbapenems represent the most potent and broad-spectrum β-lactams and are minimally affected by most β-lactamase enzymes. however, all carbapenems currently in use including meropenem and ertapenem, are parenterally administered. Tebipenem pivoxil (TBPM-PI-HBr) is a new broad-spectrum orally-administered antibiotic, from the carbapenem subgroup of β-lactam antibiotics. It is the only oral carbapenem and could be an alternative to intravenous injection carbapenem antibiotic therapy. This study aimed to evaluate the in vitro activity of tebipenem, a novel oral carbapenem, against recent gram-positive clinical isolates from cancer patients. Methods We tested 300 gram-positive isolates are recently isolated (2019-2021) from our cancer patients, collected from blood cultures against tebipenem and comparators. Clinical and laboratory Standards Instituted (CLSI) approved broth microdilution method was used with appropriate ATCC controls. MIC50, MIC90, MIC ranges and percent of susceptibility calculations were made using FDA breakpoints when available. There is no tebipenem susceptibility breakpoint for gram-positive isolates currently. MIC90 and MICs range of tebipenem and comparators against 300 gram-positive isolates from cancer patients Results MIC90 and range of tebipenem and comparators are shown in table(1). Tebipenem gave the lowest MIC90 and MIC ranges against most gram-positive isolates including Bacillus species, Corynebacterium species, Enterococcus faecalis, Micrococcus species, MSSA S.aureus, Staphylococcus lugdunensis. β-hemolytic Streptococcus, Streptococcus pneumonie, Viridans group streptococci, and Rothia species. The comparative potency of tebipenem vs meropenem as a carbapenem in this study showed that, tebipenem MIC values were generally lower at least 2-4 fold. Conclusion Our data demonstrate that oral tebipenem has promising activity against clinically significant bacterial pathogens isolated from cancer patients and it has compatible activity to that of meropenem as a carbapenem in this study. Further clinical evolution for oral carbapenem treatment of bacterial infections is warranted. Disclosures All Authors: No reported disclosures.

Efficacy of Vaporized Hydrogen Peroxide Combined with Silver Ions against Multidrug-Resistant Gram-Negative and Gram-Positive Clinical Isolates.

Antimicrobial resistance (AMR) is a serious public health problem that results in high morbidity and mortality rates. In particular, multidrug-resistant (MDR) strains circulating in hospital settings pose a major threat as they are associated with serious nosocomial infections. Therefore, regular cleaning and disinfection procedures, usually using chemical disinfectants, must be implemented in these facilities. Hydrogen peroxide (HP)-based disinfectants have proven high microbicidal activity and several comparative advantages over conventional disinfectants. We assessed the in vitro biocidal activity of an 8% HP solution combined with 30 mg/L silver ions (HP + Ag) against MDR clinical isolates of Klebsiella pneumoniae (MDRKp) and Pseudomonas aeruginosa (MDRPa), and methicillin-resistant Staphylococcus aureus (MRSA). Accordingly, the in vitro antibacterial activity was determined using the macrodilution method, and the efficacy was determined for 30 min in terms of (1) activity on bacteria in suspension and (2) activity on surfaces using vaporized HP + Ag on a 20 cm2 stainless steel surface. A strong bactericidal effect of HP + Ag was observed against MDRKp, MDRPa, and MRSA strains, with minimum inhibitory concentrations and minimum bactericidal concentrations between 362.5 and 5800 mg/L. A strong effect was observed during the 30 min of HP + Ag exposure to the resistant clinical isolates, with over 4-Log10 reduction in CFUs. Regarding the efficacy of the disinfectant on surfaces, bacterial load reductions of >99% were observed. These results suggest that HP + Ag is potentially useful as an effective disinfectant for decontaminating surfaces in hospital settings suspected of contamination with MDR bacteria.

Antibacterial and anti-biofilm activity of plumbagin against multi-drug resistant clinical bacterial isolates.

To evaluate the antibacterial activity of plumbagin (PGN) against multidrug resistance (MDR) clinical isolates. This study was carried out at the Department of Clinical Lab Sciences, King Khalid University from October 6, 2021 to December 14, 2021. We investigated the antibacterial and anti-virulence activity of PGN against MDR Gram-negative (Escherichia coli, Klebsiella pneumoniae, Salmonella Typhi, and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus [S. aureus], Staphylococcus saprophyticus [S. saprophyticus], Streptococcus pyogenes, and Enterococcus faecalis) clinical bacterial isolates. Agar well diffusion, microdilution assay, colony count method, biofilm formation, and time-kill kinetics were employed to probe the MIC, MBC, and anti-virulence activity of PGN. Plumbagin inhibited the growth of all tested isolates, with S. saprophyticus exhibiting the highest sensitivity. MIC values ranged from 0.029 to 0.117 µg/mL whereas MBC ranged from 0.235 to 0.94 µg/mL, with 79% to 99% growth inhibition. Moreover, all tested isolates showed a marked decrease in biofilm formation, with S. saprophyticus and S. aureus being the most sensitive. Plumbagin is a stand-alone, broad spectrum antibacterial with promising potential against the rising threat of antimicrobial resistance.

Five-year analysis of the in vitro activity of tedizolid against a worldwide collection of indicated species causing clinical infections: results from the Surveillance of Tedizolid Activity and Resistance (STAR) programme.

ObjectivesThe Surveillance of Tedizolid Activity and Resistance (STAR) programme monitored the tedizolid activity against Staphylococcus aureus, Enterococcus faecalis, Streptococcus pyogenes, Streptococcus agalactiae and Streptococcus anginosus group. We evaluated the antimicrobial susceptibility of 47 400 unique Gram-positive clinical isolates from the STAR programme collected from USA (21 243), Europe (17 674), Asia-Pacific (4954) and Latin America (3529) medical centres (2015–19).MethodsAll isolates were tested for susceptibility by reference broth microdilution method. WGS and in silico analysis were performed on linezolid-non-susceptible (NS) isolates.ResultsTedizolid was active against ≥99.9% of S. aureus (100.0% of MSSA and >99.9% of MRSA), E. faecalis, S. pyogenes, S. agalactiae and S. anginosus group isolates, with MIC50 values ranging from 0.12 to 0.25 mg/L and MIC90 values of 0.25 mg/L. Linezolid, vancomycin and daptomycin were also active agents against these organisms. Tedizolid inhibited all VRE and 73.1% of linezolid-NS E. faecalis isolates. Ampicillin and daptomycin retained 100.0% activity against VRE and linezolid-NS E. faecalis isolates. Linezolid-NS E. faecalis isolates carried mostly the optrA gene. G2576T alterations in the 23S rRNA were observed in one linezolid-NS S. aureus isolate and one linezolid-NS E. faecalis isolate.ConclusionsNo resistance trends were observed for tedizolid during the study period.

Tedizolid in vitro activity against Gram-positive clinical isolates causing bone and joint infections in hospitals in the USA, Europe, Latin America, and the Asia-Pacific region (2015-2019)

As bone and joint infections (BJIs) frequently require prolonged, systemic antibiotic use, tedizolid is an attractive candidate for BJI therapy in adults and children. Tedizolid activity was evaluated against 1,193 Gram-positive isolates causing BJI in American (USA), European (EUR), Latin American (LATAM), and Asian-Pacific (APAC) medical centers. Isolates consecutively collected from 2015 to 2019 were susceptibility tested by CLSI broth microdilution. Staphylococcus aureus (69.2%) was the most common pathogen with a 25.9% MRSA rate and tedizolid MIC50/90 of 0.12/0.25 mg/L (100% susceptible). Tedizolid exhibited MIC50/90 values of 0.12/0.12 mg/L (98.9% susceptible) for CoNS (7.5% of BJI), 0.12/0.25 mg/L for streptococci, and 0.25/0.25 mg/L for enterococci. Overall, high susceptibility rates (100.0%) for linezolid, daptomycin, and vancomycin were observed. In summary, tedizolid had potent in vitro activity against contemporary Gram-positive cocci causing BJI in adults and children in USA, EUR, LATAM, and APAC hospitals.

Retention of Minocycline Susceptibility When Gram-Positive Periprosthetic Joint Infection Isolates Are Non-Susceptible to Doxycycline.

Background: The treatment of hardware infections often utilizes chronic oral suppression antibiotics to prevent infection recurrence. However, when methicillin-resistant Staphylococcus aureus and other bacteria are non-susceptible to doxycycline, limited oral antibiotic options can be available that do not cause significant side effects and drug–drug interactions. Consequently, the purpose of this study was to evaluate the ability of Gram-positive clinical prosthetic joint infection isolates that were non-susceptible to doxycycline and to retain susceptibility to minocycline. Methods: Twenty-six Gram-positive prosthetic joint infection isolates that were not susceptible to doxycycline were evaluated for retained minocycline susceptibility with the use of minocycline gradient diffusion test strips. Results: All five of the coagulase-negative staphylococcal isolates and eight of the eleven methicillin-resistant S. aureus isolates were susceptible to minocycline, despite being doxycycline non-susceptible. None of the five Enterococcus faecium PJI isolates retained susceptibility to minocycline and only two of the five E. faecalis isolates (n = 5) were susceptible to minocycline. Conclusions: The findings have direct clinical implications supporting minocycline susceptibility testing for patients with PJI and other hardware-associated infections, which have isolates that are doxycycline non-susceptible to thereby provide alternative suppression antibiotic options.

Heteroaryl-Ethylenes as New Effective Agents for High Priority Gram-Positive and Gram-Negative Bacterial Clinical Isolates

The World Health Organization has identified antimicrobial resistance as a public health emergency and developed a global priority pathogens list of antibiotic-resistant bacteria that can be summarized in the acronym ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacterales species), reminding us of their ability to escape the effect of antibacterial drugs. We previously tested new heteroaryl-ethylene compounds in order to define their spectrum of activity and antibacterial capability. Now, we focus our attention on PB4, a compound with promising MIC and MBC values in all conditions tested. In the present study, we evaluate the activity of PB4 on selected samples of ESKAPE isolates from nosocomial infections: 14 S. aureus, 6 E. faecalis, 7 E. faecium, 12 E. coli and 14 A. baumannii. Furthermore, an ATCC control strain was selected for all species tested. The MIC tests were performed according to the standard method. The PB4 MIC values were within very low ranges regardless of bacterial species and resistance profiles: from 0.12 to 2 mg/L for S. aureus, E. faecalis, E. faecium and A. baumannii. For E. coli, the MIC values obtained were slightly higher (4–64 mg/L) but still promising. The PB4 heteroaryl-ethylenic compound was able to counteract the bacterial growth of both high-priority Gram-positive and Gram-negative clinical strains. Our study contributes to the search for new molecules that can fight bacterial infections, in particular those caused by MDR bacteria in hospitals. In the future, it would be interesting to evaluate the activity of PB4 in animal models to test for its toxicity.

Complete Genome Sequences of Gram-Positive Opportunistic Pathogens Isolated from Hospitals in Almaty, Kazakhstan.

ABSTRACTThe appearance of drug-resistant pathogens reduces the therapeutic applicability of antibiotics and increases the rate of hospital infections among patients. Complete genome sequences of four Gram-positive clinical isolates of Streptococcus and Staphylococcus were obtained and analyzed to serve as model microorganisms for further studies on drug-induced antibiotic resistance reversion.

Exploring the structure-activity relationships of diphenylurea as an antibacterial scaffold active against methicillin- and vancomycin-resistant Staphylococcus aureus

A set of structurally related diphenylurea derivatives bearing aminoguanidine moiety were synthesized, and their antibacterial activity was assessed against a panel of multi-drug resistant Gram-positive clinical isolates. Two compounds 6 and 24 were identified with better bacteriological profile than the lead compound I. The multi-step resistance development studies indicated that MRSA are less likely to develop resistance toward diphenylurea compounds. Moreover, these compounds demonstrated a prolonged post-antibiotic effect than that of vancomycin. Furthermore, compounds 6 and 24 were able to re-sensitize VRSA to vancomycin, resulting in 8- to more than 32-fold improvement in vancomycin MIC values against clinical VRSA isolates. Finally, when assessed in an in vivo skin infection mouse model, the efficacy of compound 24 was very comparable to that of the commercially available fusidic acid ointment. Additionally, the diphenylurea 24 did not have a pronounced effect on the animal weights along the experiment indicating its safety and tolerability to mice. Taken together, these results indicate that the diphenylurea scaffold merits further investigation as a promising anti-staphylococcal treatment option.

1224. In vitro Activities of Ceftaroline and Comparator Agents against Gram-positive Bacterial Pathogens Causing Blood Stream Infections in a Global Population: ATLAS Surveillance Program 2012-2019

BackgroundTypical gram-positive organisms causing bloodstream infections (BSI) include Staphylococcus aureus (methicillin-susceptible [MSSA] and -nonsusceptible [MRSA]), coagulase negative staphylococci, Streptococcus pneumoniae and beta hemolytic streptococci. The parenteral cephem ceftaroline fosamil is approved for treatment of patients with community-acquired bacterial pneumonia caused by S. pneumoniae (including cases with concurrent bacteremia), MSSA, Haemophilus influenzae, and some species of Enterobacterales. Limited data have been published on the in vitro activity of ceftaroline against recent gram-positive clinical isolates known to be frequent bacterial causes of blood stream infections.MethodsStandard CLSI broth microdilution MIC determinations (M07) were performed with ceftaroline and comparator agents. MICs were interpreted using 2021 CLSI MIC breakpoints. Clinically relevant, non-duplicate, isolates cultured from blood by clinical laboratories in 2012-2019 were tested by the ATLAS (Antimicrobial Testing Leadership and Surveillance) program central laboratory (IHMA, Inc., Schaumburg, IL, USA). In total, 21,967 non-duplicate isolates of S. aureus, S. epidermidis, S. pneumoniae and beta hemolytic streptococci from BSI collected between 2012 and 2019 were tested. Isolates came from (n/%): Asia/South Pacific (2,970/13.5%), Europe (13,691/62.3%), Latin America (2,824/12.9%), MidEast/Africa (1,498/6.8%), and North America (Canada only) (984/4.5%).ResultsCeftaroline and comparator agent activities are summarized in the following table.Results Table ConclusionGreater than 99% of S. pneumoniae, beta-hemolytic streptococci and MSSA isolates included in a 2012-2019 collection of gram-positive blood stream pathogens were susceptible to ceftaroline. 90.8% of MRSA were susceptible, and 9.1% isolates categorized as susceptible-dose dependent (MIC, 2-4 µg/mL); four isolates (two from Thailand and one each from China and S. Korea) were resistant to ceftaroline (MIC >4 µg/mL). The ceftaroline MIC90 for S. epidermidis was 0.5 µg/mL, with 97.7% of MICs ≤1 µg/mL. Ceftaroline continues to demonstrate potent in vitro activity against clinically relevant pathogens associated with BSI.Disclosures Meredith Hackel, PhD MPH, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Gregory Stone, PhD, AztraZeneca (Shareholder, Former Employee)Pfizer, Inc. (Employee) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor)

1566. In vitro Activities of Ceftaroline and Comparator Agents against Gram-positive Bacterial Pathogens Causing Blood Stream Infections in a Global Population: ATLAS Surveillance Program 2012-2018

BackgroundTypical gram-positive organisms causing bloodstream infections (BSI) include Staphylococcus aureus (methicillin-susceptible [MSSA] and -nonsusceptible [MRSA]), coagulase negative staphylococci, Streptococcus pneumoniae and beta hemolytic streptococci. The parenteral cephem ceftaroline fosamil is approved for treatment of patients with community-acquired bacterial pneumonia caused by S. pneumoniae (including cases with concurrent bacteremia), MSSA, Haemophilus influenzae, and some species of Enterobacterales. Limited data have been published on the in vitro activity of ceftaroline against recent gram-positive clinical isolates known to be frequent bacterial causes of blood stream infections.MethodsStandard CLSI broth microdilution MIC determinations (M07) were performed with ceftaroline and comparator agents. MICs were interpreted using 2020 CLSI MIC breakpoints. Clinically relevant, non-duplicate, isolates cultured from blood by clinical laboratories in 2012-2018 were tested by the ATLAS (Antimicrobial Testing Leadership and Surveillance) program central laboratory (IHMA, Inc., Schaumburg, IL, USA). In total, 10,998 non-duplicate isolates of S. aureus, S. epidermidis, S. pneumoniae and beta hemolytic streptococci from BSI collected between 2012 and 2018 were tested. Isolates came from (n/%): Asia/South Pacific (1,739/15.8%), Europe (5,448/49.5%), Latin America (1,805/16.4%), MidEast/Africa (861/7.8%), and North America (1,145/10.4%).ResultsCeftaroline and comparator agent activities are summarized in the following table.Table ConclusionGreater than 98% of S. pneumoniae, S. epidermidis, beta-hemolytic streptococci and MSSA isolates included in a 2012-2018 collection of gram-positive blood stream pathogens were susceptible to ceftaroline. 91.4% of MRSA were susceptible, and 8.6% isolates categorized as susceptible-dose dependent (MIC, 2-4 ug/mL); two isolates (one each from Thailand and S. Korea) were resistant to ceftaroline (MIC >4 ug/mL). Ceftaroline continues to demonstrate potent in vitro activity against clinically relevant pathogens associated with BSI.Disclosures Greg Stone, PhD, AztraZeneca (Shareholder, Former Employee)Pfizer, Inc. (Employee) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Consultant)Shionogi & Co., Ltd. (Independent Contractor)

1547. Activity of Tedizolid and Comparator Agents against Gram-Positive Bacterial Isolates Causing Skin and Skin Structure Infections in Pediatric Patients during 2015-2019 in the US

BackgroundNew strategies to treat acute bacterial skin and skin structure infections (ABSSSI) are needed due to the spread of methicillin-resistant Staphylococcus aureus (MRSA), a common multidrug resistant pathogen of ABSSSIs. Tedizolid (TZD) was approved by the US FDA for treating ABSSSI in adults and is under evaluation for treating pediatric patients. Accordingly, the activity of TZD and comparators was evaluated against clinical surveillance isolates collected from pediatric patients with SSSI in the US.MethodsA total of 2,758 Gram-positive isolates were collected from pediatric patients with SSSIs in 33 sites in the US between 2015 and 2019 as part of the Surveillance of Tedizolid Activity and Resistance (STAR) Program. Bacterial identification was confirmed by MALDI-TOF MS and susceptibility (S) testing performed by the CLSI reference broth microdilution method. Current CLSI interpretative criteria was applied.Results S. aureus (SA; n=2,163; 78.4%) was the most frequent pathogen recovered from all age groups (≤ 1y; 2-5y; 6-12y; 13-17y), followed by β-hemolytic streptococci (BHS; n=460; 16.7%), and coagulase-negative staphylococci (CoNS; n=70; 2.5%). TZD was active against all SA (MIC50/90, 0.12/0.25 mg/L; 100% S). Equivalent TZD MIC50/90 values (0.12/0.25 mg/L) were observed against MRSA (n=886; 41.0%; MIC50/90, 0.12/0.25 mg/L) and methicillin susceptible (MSSA; MIC50/90, 0.12/0.25 mg/L) isolates, regardless the age group. TZD also was very active against BHS (MIC50/90, 0.12/0.25 mg/L; 100% S, regardless of species). TZD, linezolid, and daptomycin had 100.0% S rates against the main Gram-positive species and organism groups (Figure). Ceftaroline and clindamycin showed S rates of >90% against MRSA, MSSA, S. pyogenes and S. dysgalactiae. Lower S rates were observed for clindamycin against VGS (88.2%) and S. agalactiae (64.1%). TZD was the most potent agent (MIC90, 0.25 mg/L) against Enterococcus faecalis (n=30, 1.1%), and a vancomycin-resistance phenotype was observed in 1 (3.3%) isolate.ConclusionTZD was highly active against Gram-positive clinical isolates responsible for SSSI in pediatric patients across US hospitals from a 5-year period. TZD was equipotent or more potent than comparators against MSSA and MRSA isolates.Table 1 DisclosuresCecilia G. Carvalhaes, MD, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Pfizer (Research Grant or Support) Helio S. Sader, MD, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Melinta (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support)Pfizer (Research Grant or Support) Paul R. Rhomberg, n/a, Cidara Therapeutics (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)Merck (Research Grant or Support) Mariana Castanheira, PhD, 1928 Diagnostics (Research Grant or Support)A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Amplyx Pharmaceuticals (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support)Pfizer (Research Grant or Support)Qpex Biopharma (Research Grant or Support) Rodrigo E. Mendes, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Basilea Pharmaceutica International, Ltd (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Department of Health and Human Services (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Pfizer (Research Grant or Support)

1595. Ceftobiprole Activity against Gram-Positive Pathogens Causing Bone and Joint Infections in the United States from 2016 through 2019

BackgroundBone and joint infections (BJIs) cause serious morbidity and mortality and present significant treatment challenges. Ceftobiprole medocaril, the prodrug of ceftobiprole, is an advanced cephalosporin approved in many European and non-European countries for the treatment of adults with community- and hospital-acquired pneumonia, excluding ventilator-associated pneumonia. Ceftobiprole medocaril is not approved in the United States (USA) but has qualified infectious disease product (QIDP) status, and is being evaluated in two phase 3 clinical trials in patients with acute bacterial skin and skin structure infections (completed) or Staphylococcus aureus bacteremia (ongoing). In this study, the activity of ceftobiprole and comparators was evaluated against recent Gram-positive clinical isolates collected from BJIs in the USA.Methods306 Gram-positive pathogens were collected from patients with BJIs at 27 US medical centers from 2016 through 2019. Susceptibility to ceftobiprole and comparator agents was tested using current CLSI methods. CLSI and EUCAST interpretive criteria were applied according to current guidelines.ResultsThe major Gram-positive species and pathogen groups included S. aureus (67.0%; methicillin-resistant S. aureus [MRSA], 35.1%), β-hemolytic streptococci (BHS; 13.7%), coagulase-negative staphylococci (CoNS; 9.5%), and Enterococcus faecalis (6.9%). Ceftobiprole was highly active against S. aureus (MIC50/90 values, 0.5/1 mg/L; 100.0% susceptible by EUCAST criteria), including MRSA (MIC50/90 values, 1/2 mg/L). Ceftobiprole also exhibited potent activity against other Gram-positive cocci, including BHS (MIC50/90 values, 0.015/0.03 mg/L; 100% inhibited at ≤ 4 mg/L, which is the EUCAST PK-PD non-species-related breakpoint), CoNS (MIC50/90 values, 1/4 mg/L; 100% inhibited at ≤4 mg/L), and E. faecalis (MIC50/90 values, 0.5/2 mg/L; 100.0% inhibited at ≤ 4 mg/L).ConclusionCeftobiprole was highly active against clinical BJI isolates from the major Gram-positive pathogen groups collected at US medical centers during 2016–2019. The broad-spectrum activity of ceftobiprole, including potent activity against MRSA, supports its further evaluation for this potential indication.DisclosuresLeonard R. Duncan, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Basilea Pharmaceutica International, Ltd. (Research Grant or Support)Dept of Health and Human Services (Research Grant or Support) Kamal Hamed, n/a, Basilea Pharmaceutica International Ltd. (Employee) Jennifer Smart, PhD, Basilea Pharmaceutica International, Ltd (Employee)Department of Health and Human Services (Research Grant or Support) Michael A. Pfaller, MD, Amplyx Pharmaceuticals (Research Grant or Support)Basilea Pharmaceutica International, Ltd (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Department of Health and Human Services (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support) Robert K. Flamm, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Amplyx Pharmaceuticals (Research Grant or Support)Basilea Pharmaceutica International, Ltd (Research Grant or Support)Department of Health and Human Services (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support) Rodrigo E. Mendes, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Basilea Pharmaceutica International, Ltd (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Department of Health and Human Services (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Pfizer (Research Grant or Support)

Purification, De Novo Characterization and Antibacterial Properties of a Novel, Narrow-Spectrum Bacteriostatic Tripeptide from Geotrichum candidum OMON-1

Antibiotic resistance and need for novel antibiotics have seen focus on antimicrobial peptides (AMPs) increase in recent years. The study investigated purification and de novo characterization of an AMP compound produced by bioactive Geotrichum candidum OMON-1. Antimicrobial extract of G. candidum OMON-1 was purified via reverse-phase high-performance liquid chromatography (RP-HPLC). Purified compound (GP-2B) was characterized on liquid chromatography–mass spectrometry (LC–MS) and MALDI-TOF tandem mass spectrometry (MS/MS), and spectra were interpreted using de novo peptide sequencing protocols. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of GP-2B were determined in vitro against Gram-positive clinical isolates and time-kill kinetics against Staphylococcus aureus investigated, while antimicrobial activity was also observed on scanning electron microscope (SEM). GP-2B was successfully purified on RP-HPLC with trifluoroacetic acid-buffered acetonitrile. LC–MS confirmed GP-2B as pure and positively charged with molecular mass 409.23 amu, while characterization of MS/MS spectrum via de novo peptide sequencing described it a tripeptide with carboxymethylcystyl–asparagyl–aspartate amino acid sequence. GP-2B had MIC 8 and 32 µg/mL against antibiotic-sensitive and -resistant S. aureus, respectively, and 64 µg/mL for Enterococci strains. MBC was fourfold MIC, while GP-2B reduced S. aureus by 21.8% and 30% at 5× and 10× MIC, respectively, in time-kill kinetics. SEM images also confirmed bacteriostasis of S. aureus cells. This study successfully purified and characterized via de novo sequencing, a novel bacteriostatic AMP from G. candidum OMON-1.

In Vitro Activity and Potency of the Novel Oxazolidinone Contezolid (MRX-I) Tested against Gram-Positive Clinical Isolates from the United States and Europe.

Contezolid, a new oxazolidinone antibacterial agent currently in development for the treatment of skin and skin structure infections, was susceptibility tested against Gram-positive clinical isolates (n = 1,211). Contezolid demonstrated potent activity against Staphylococcus aureus (MIC50/90, 0.5/1 mg/liter), coagulase-negative Staphylococcus (MIC50/90, 0.25/0.5 mg/liter), Enterococcus spp. (MIC50/90, 0.5/1 mg/liter), and streptococci (MIC50/90, 1/1 mg/liter). Moreover, methicillin-resistant S. aureus and vancomycin-resistant Enterococcus faecium isolates were all inhibited by contezolid at ≤1 mg/liter. These results support the clinical development of contezolid.