MSSA Isolates Research Articles

In vitro activity of Exebacase (CF-301) against clinical Staphylococcus aureus surveillance isolates from the United States, Europe, and Latin America, 2015–2017

Lysins are direct lytic agents which act through enzymatic cell-wall-hydrolysis and represent a potential new class of antimicrobial agents in development to treat antibiotic-resistant bacterial infections. Exebacase (CF-301) is a first-in-class lysin now in clinical development for the treatment of Staphylococcus aureus (S. aureus) bacteremia and infective endocarditis (IE) when used in addition to conventional antibiotics. Exebacase and comparator antibiotics were tested by broth microdilution against a set of 535 clinical MSSA and MRSA isolates collected from 2015 to 2017 throughout the United States, Europe and South America. All S. aureus isolates were inhibited by ≤1 mg/L exebacase (MIC50/90, 0.5/1 mg/L) with a range of 0.25–1 mg/L. No difference in susceptibility was observed between the MSSA and MRSA isolates. Exebacase was uniformly and equivalently active against all recent clinical MSSA and MRSA surveillance isolates from a broad survey across 3 continents.

Molecular Typing and Variations in Amount of tst Gene Expression of TSST-1-Producing Clinical Staphylococcus aureus Isolates.

The toxic shock syndrome toxin-1 (TSST-1), encoded by tst gene, has been proposed to cause staphylococcal toxic shock syndrome (TSS) in a susceptible host, which highlights the need to evaluate the level of tst gene expression and molecular genetic characteristics of the tst-positive isolates. A total of 916 S. aureus isolates collected from seven hospitals in China were screened for the tst gene. The tst positive isolates were characterized by spa, SCCmec, PFGE, and agr typing. Representative strains were also subjected to MLST typing. qRT-PCR was used to quantify tst and major virulence regulator genes expression. We also sequenced the regions of promoter and open reading frame (ORF) of tst to investigate whether they correlate with the variation in tst expression. We found 208 (22.7%) of surveyed isolates including 198 (29.8%) of MRSA and 10 (4.0%) of MSSA isolates harbored the tst gene. The most common clone among tst positive MRSA isolates belonged to ST5 (CC5)-agr2-t002-SCCmecII. The amount of tst mRNA varied 8.4-folds among clinical S. aureus isolates. Sequencing the tst promoter revealed a base T deletion in tst high expressed isolates. As for major virulence regulators, srrA, sarT, RNAIII, and ccpA in four tst differentially expressed strains were detected to be highly expressed, respectively. Our study revealed high prevalence of ST5 (CC5)-agr2-t002-SCCmecII clone among tst positive MRSA in hospitals from China. The levels of tst expression among clinical S. aureus isolates varied, which may be associated with tst promoter and variations in specific virulence regulators.

Phenotypic and genotypic characterization of PVL-positive Staphylococcus aureus isolated from retail foods in China

Staphylococcus aureus encodes numerous toxins that are known or strongly suspected to cause specific diseases or symptoms. Panton-Valentine leukocidin (PVL) is one of these important toxins that is associated with high mortality rates. In our previous study, 1581 S. aureus strains were isolated from 4300 samples of retail foods obtained from most of the provincial capitals in China from 2011 to 2016. This study aimed to investigate the prevalence of PVL-positive S. aureus isolates from retail foods in China and characterize these isolates by antibiotic resistance testing, spa typing, multilocus sequence typing (MLST) and enterotoxin gene analyses. In total, seventy-two isolates (72/1581, 4.6%) possessed pvl genes, including 24.1% MRSA isolates (26/108) and 3.1% MSSA isolates (46/1473), covering different types of food. The strains were divided into seventeen sequence types (STs) and twenty-seven spa types, and 43.1% (31/72) of the PVL-positive S. aureus isolates belonged to CC59-t437. These isolates contained at least one of the following enterotoxin genes: sei (97.2%), sem (86.1%), seq (80.6%), seg (68.1%), sek (68.1%), seb (62.5%), sel (52.8%), sej (50.0%), seh (48.6%), sep (45.8%), sea (38.9%), ser (37.5%), sen (27.8%), sec (16.7%), see (16.7%), sed (6.9%), seo (6.9%) and seu (6.7%). A total of 87.5% of the S. aureus isolates (63/72) harboured the classic SE genes (sea, seb, sec, sed, and see), whereas all the S. aureus isolates harboured the genes of the egc cluster (seg, sei, sem, sen, seo, and seu). In antimicrobial susceptibility tests, 98.6% of the isolates (71/72) exhibited resistance to at least one antibiotic, including 47 multi-drug-resistant isolates. Resistance to penicillin (94.4%), erythromycin (83.4%), clindamycin (63.9%), kanamycin (61.1%), telithromycin (58.3%), streptomycin (51.4%), tetracycline (47.2%), chloramphenicol (27.8%), fusidic acid (27.8%) and other antibiotics (<20%) was observed. All the PVL-positive MRSA isolates belonged to CC59-t437, which is the predominant type of community-associated (CA)-MRSA in China. The presence of these isolates in food represents a potential health risk for consumers and warrants further attention.

Antibiotic resistance pattern and spa types of Staphylococcus aureus strains isolated from food business and hospital kitchen employees in Çanakkale, Turkey

Background/aim The aim of this study was to determine antibiotic resistance profiles and spa types of Staphylococcus aureus strains isolated from food business employees in Çanakkale, Turkey.Materials and methods S. aureus isolates were collected from hand and nasal swabs of 300 individuals working in 17 food businesses and 9 hospital kitchens. All S. aureus isolates obtained from each carrier were typed by staphylococcal protein A (spa) typing method.Staphylococcal cassette chromosome mec (SCCmec) and multilocus sequence typing (MLST) of MRSA were performed by sequencing method.Results Of the 300 individuals, 125 (41.6%) were found to be carriers of S. aureus, 215 isolates of which were obtained in total. Three (1.4%) of 215 isolates were identified as MRSA. Sixty spa types were identified among the 121 MSSA isolates, the most common being t084 (9%). A novel spa type was discerned and added to the Ridom SpaServer database as t14963. The MLST type of the MRSA strains identified as spa type t786 was ST88 and as spa type t223 was ST22. All MRSA were determined to be SCCmec type IVa.Conclusion spa typing can be performed to screen for transmission of S. aureus. t786, ST88, and SCCmec IVa MRSA strains were identified for the first time in Turkey.

Molecular epidemiology and resistance profiles among healthcare- and community-associated Staphylococcus aureus keratitis isolates.

PurposeTo characterize the molecular, epidemiological, and resistance profiles of methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) keratitis isolates.Patients and methodsWe used a combination of standard microbiological techniques and DNA microarray analysis to characterize the molecular and antibiotic resistance profiles of 75 Staphylococcus aureus keratitis isolates collected over an 11-year period (2006–2016).ResultsTwo major USA clonal complexes (CC), CC5 (n=30, 40%) and CC8 (n=28, 37.3%), accounted for 77.3% of the collected S. aureus isolates. USA100, traditionally healthcare associated (n=18/47, 38.3%), and USA300, traditionally community associated (n=12/47, 25.5%), were the dominant MRSA strains. Four (22.2%) of the USA100 MRSA isolates were recovered from patients with no prior healthcare exposure. Eleven (91.7%) of the USA300 isolates were recovered from patients with documented healthcare risk factors. MSSA isolates were polyclonal (n=13). Ninety-three percent of MSSA infections were of healthcare origin. Thirty-seven of 61 (60.6%) healthcare- and 11 of 14 (78.6%) community-associated strains were resistant to three or more antibiotic classes. Sixty-eight percent (n=51) of isolates harbored three of more resistance determinants (genes). The Panton-Valentine Leucocidin gene was detected in 11 (14.7%) of the study isolates. The majority (72.7%) of the strains were members of the USA300 MRSA clone.ConclusionClonal complexes CC5 and CC8 were the most frequent clones detected among both the MSSA and the MRSA keratitis isolates. USA100 and USA300 clones were the dominant MRSA genotypes. The USA300 MRSA clone has become a leading cause of healthcare-associated keratitis in South Florida. The USA100 MRSA clone has emerged as an increasing cause of community-associated corneal infections in our outpatient population. This shifting epidemiology coupled with the increasing prevalence of multidrug resistance among both MSSA and MRSA keratitis is a cause of concern.

Nasal colonization of SCCmec II, III and tst-1 positive Methiticillin resistance Staphylococcal aureus isolated from patients in a hemodialysis unit, Tehran, Iran

Patients with end stage renal disease undergoing dialysis are at the high risk of infections or colonization with MRSA We evaluated the status colonization of two hemodialysis patients and determined their phenotype by using oxacillin and cefoxitin disks and also studied their genotypes by using PCR We found the MRSA strains in our cases were healthcare associated harboring SCCmec II amp III and tst or PVL gene positive This report emphasizes the importance of S aureus status colonization in this group due to MSSA and MRSA isolates can harbor the mobile genetic element of tst gene and also the acquisition of the SCCmec for changing MSSA to MRSA is possible nbsp

Outbreak report of investigation and control of an outbreak of Panton-Valentine Leukocidin-positive methicillin-sensitive Staphylococcus aureus (PVL-MSSA) infection in neonates and mothers

BackgroundIn January 2011, there was an outbreak of Panton-Valentine Leukocidin-positive methicillin-sensitive Staphylococcus aureus (PVL-MSSA) infection in a neonatal unit (NNU).We describe the investigation and control of an outbreak of PVL-MSSA infection in neonates. Setting: Neonatal unit in West London.MethodsWe performed descriptive and analytical (case-control study) epidemiological investigations. Microbiological investigations including screening of MSSA isolates by PCR for the presence of the luk-PV, mecA and mecC genes and comparison of isolate with Pulsed field gel electrophoresis (PFGE). Control measures were also introduced.ResultsSixteen babies were infected/colonised with the outbreak strain. Of these, one baby developed blood stream infection, 12 developed skin pustules and four babies were colonised.Four mothers developed breast abscesses. Eighty-seven babies in the unit were screened and 16 were found to have same PVL-MSSA strain (spa type t005, belonging to MLST clonal complex 22). Multivariate analysis showed gestational age was significantly lower in cases compared to controls (mean gestational age: 31.7 weeks v 35.6 weeks; P = 0.006). Length of stay was significantly greater for cases, with a median of 25 days, compared to only 6 days for controls (P = 0.01). Most (88%) cases were born through caesarean section, compared to less than half of controls. (P = 0.002).No healthcare worker carriers and environmental source was identified. The outbreak was controlled by stopping new admissions to unit and reinforcing infection control precautions. The outbreak lasted for seven weeks. No further cases were reported in the following year.ConclusionsInfection control teams have to be vigilant for rising prevalence of particular S. aureus clones in their local community as they may cause outbreaks in vulnerable populations in healthcare settings such as NNUs.

A ten year study of prevalence, antimicrobial susceptibility pattern, and genotypic characterization of Methicillin resistant Staphylococcus aureus causing ocular infections in a tertiary eye care hospital in South India

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of vision threatening ocular infections. This study aimed to determine the prevalence and antimicrobial susceptibility pattern of MRSA and their genotypic characterization in ocular infections. The study period was from January 2007 to December 2017 in Aravind Eye Hospital, Madurai. Retrospective analysis of clinical records found a total of 1306 Staphylococcus aureus in various ocular infections. Among these, 274 (21%) were found to be MRSA with an increased incidence from 9% in 2007 to 38% in 2017 (P = .007). MRSA was isolated commonly from lacrimal sac infection 89 (32%), lid infection 55 (20%), keratitis 45 (16%) and orbital infection 34 (12%). MRSA isolates showed 100% sensitivity to vancomycin, 91% to chloramphenicol and majority of MRSA isolates were resistant to all fluoroquinolones. MSSA strains showed very minimal resistance to chloramphenicol (5%) and also there was no resistance to vancomycin. In case of the MSSA isolates, resistance to fluroquinolones (ciprofloxacin, gatifloxacin, moxifloxacin, ofloxacin and levofloxacin) was found to increase during study period. Methicillin-resistance is conferred by the carriage of Staphylococcal Cassette Chromosome mec (SCCmec) and most of our isolates were belonged to SCCmec type V and IV which is known to be community acquired MRSA. MLST sequencing on seven housekeeping genes revealed, sequence type ST772 was predominant followed by ST22. Agr typing identified most of the isolates (69) were agr type II (77%). By spa typing, there are 16 spa types were identified, among which 60% of the isolates had t657 spa type.

Detection of MRSA of Lineages CC130-mecC and CC398-mecA and Staphylococcus delphini-lnu(A) in Magpies and Cinereous Vultures in Spain.

The aim of this study was to determine the carriage rate of coagulase-positive staphylococci (CoPS) in wild birds and to characterize recovered isolates. Tracheal samples from 324 wild birds, obtained in different Spanish regions during 2015-2016, were screened for CoPS carriage. The antimicrobial resistance profile and the virulence gene content were investigated. Molecular typing was performed by spa, agr, MLST, SCCmec, and S. delphini group classification. CoPS were recovered from 26 samples of wild birds (8.3%), and 27 isolates were further characterized. Two CoPS species were detected: S. aureus (n = 15; eight cinereous vultures and seven magpies) and S. delphini (n = 12; 11 cinereous vultures and one red kite). Thirteen S. aureus were methicillin-resistant (MRSA) and the remaining two strains were methicillin-susceptible (MSSA). Twelve MRSA were mecC-positive, typed as t843-ST1583/ST1945/ST1581/ST1571 (n = 11) and t1535-ST1945 (n = 1) (all of clonal-complex CC130); they were susceptible to the non-β-lactams tested. The remaining MRSA strain carried the mecA gene, was typed as t011-ST398-CC398-agrI-SCCmec-V, and showed a multiresistance phenotype. MSSA isolates were ascribed to lineages ST97-CC97 and ST425-CC425. All S. aureus lacked the studied virulence genes (lukS/F-PV, tst, eta, etb, and etd), and the IEC type E (with scn and sak genes) was detected in four mecC-positive and one MSSA isolates. S. delphini strains were methicillin-susceptible but showed resistance to at least one of the antimicrobials tested, with high penicillin (75%, with blaZ gene) and tetracycline [58%, with tet(K)± tet(L)] resistance rates. All S. delphini isolates presented the virulence genes lukS-I, siet, and se-int, and four carried the clindamycin-resistance lnu(A) gene.

Efficacy of silver nanoparticles against multidrug resistant clinical Staphylococcus aureus isolates from Nigeria

ABSTRACTMultidrug resistant (MDR) S. aureus infections continue to account for excess mortality in hospital and community settings and constitute a rising global health problem. However, data on the efficacy and mechanism of actions of alternative solutions like silver nanoparticles in developing countries are lacking. This study investigated anti-staphylococcal activity of silver nanoparticles (AgNP) against local strains from Nigeria. A total 119 clinical isolates of S. aureus from five Nigerian laboratories categorized as MRSA (n = 52) and MSSA (n = 67) by PCR were studied. The MIC of AgNP produced by chemical reduction method and characterized by surface plasmon resonance absorbance and size equivalence by scanning electron microscopy was determined by microbroth dilution method. Its effect on protease activity and plasmids were also investigated. Baseline characteristics of the isolates revealed MDR phenotype of the isolates, carriage of diverse plasmids (15–32 kb) among the MDR MSSA, and mean extracellular protease activity of 24.8–55.7 U/mL. The chemically synthesized AgNP had a peak absorbance at 400 nm with a size equivalence of 4.58 nm. The MICs of AgNP against the isolates were 4.7 μg/mL and 4.9 μg/mL, respectively, for MRSA and MSSA (P > 0.05). The bactericidal effect of AgNP at 2.5–5 μg/mL on the MSSA and MRSA isolates was observed at 2.7–5.5 h post exposure in vitro. Further analysis revealed plasmid eviction in the MDR MSSA isolates exposed to 5 μg/mL AgNP and dose-dependent reduction in extracellular protease activity by 84.6–93.1%. Hemolysis of human erythrocytes by AgNP was not observed at the MIC range. Conclusion: This study revealed safety and efficacy of AgNP against clinical MDR S. aureus isolates from Nigeria, using plasmid eviction and protease inhibition as mechanisms of action.

A novel multidrug-resistant PVL-negative CC1-MRSA-IV clone emerging in Ireland and Germany likely originated in South-Eastern Europe

This study investigated the recent emergence of multidrug-resistant Panton-Valentine leukocidin (PVL)-negative CC1-MRSA-IV in Ireland and Germany.Ten CC1-MSSA and 139 CC1-MRSA isolates recovered in Ireland between 2004 and 2017 were investigated. These were compared to 21 German CC1-MRSA, 10 Romanian CC1-MSSA, five Romanian CC1-MRSA and two UAE CC1-MRSA, which were selected from an extensive global database, based on similar DNA microarray profiles to the Irish isolates. All isolates subsequently underwent whole-genome sequencing, core-genome single nucleotide polymorphism (cgSNP) analysis and enhanced SCCmec subtyping.Two PVL-negative clades (A and B1) were identified among four main clades. Clade A included 20 German isolates, 119 Irish isolates, and all Romanian MRSA and MSSA isolates, the latter of which differed from clade A MRSA by 47–130 cgSNPs. Eighty-six Irish clade A isolates formed a tight subclade (A1) exhibiting 0–49 pairwise cgSNPs, 80 of which harboured a 46 kb conjugative plasmid carrying both ileS2, encoding high-level mupirocin resistance, and qacA, encoding chlorhexidine resistance. The resistance genes aadE, aphA3 and sat were detected in all clade A MRSA and the majority (8/10) of clade A MSSA isolates. None of the clade A isolates harboured any enterotoxin genes other than seh, which is universally present in CC1. Clade B1 included the remaining German isolate, 17 Irish isolates and the two UAE isolates, all of which corresponded to the Western Australia MRSA-1 (WA MRSA-1) clone based on genotypic characteristics. MRSA within clades A and B1 differed by 188 cgSNPs and clade-specific SCCmec characteristics were identified, indicating independent acquisition of the SCCmec element.This study demonstrated the existence of a European PVL-negative CC1-MRSA-IV clone that is distinctly different from the well-defined PVL-negative CC1-MRSA-IV clone, WA MRSA-1. Furthermore, cgSNP analysis revealed that this newly defined clone may have originated in South-Eastern Europe, before spreading to both Ireland and Germany.

Antimicrobial Activity of Ethanol Extract of Abrus precatorius L. Roots against Planktonic Cells and Biofilm of Urine and Blood Methicillin Sensitive Staphylococcus aureus (MSSA) Isolate

The purpose of this study was to to compare the antibiofim activity of ethanol extract of Abrus precatorius L. roots at various concentrations of the Indonesian isolate of Staphylococcus aureus biofilm. The method used included inhibition test of planktonic bacteria and inhibition test of bacterial biofilm. The variable measured is the optical density (OD) of biofilm formation tested by ELISA reader. Inhibition test of biofilm formation is carried out using the microtiter plate method. The results showed that ethanol extract of A. precatorius L. roots had a significant differences in the inhibitory effect on biofilm formation between treatment group and positive control. The linear regression test showed that antibiofilm activity of ethanol extract of A. precatorius L. roots was slightly stronger on blood MSSA isolate. Therefore, the ethanol extract of A. precatorius L. roots have antibiofilm activity for MSSA isolate.

Design and synthesis of biaryloxazolidinone derivatives containing a rhodanine or thiohydantoin moiety as novel antibacterial agents against Gram-positive bacteria

Novel biaryloxazolidinone derivatives containing a rhodanine or thiohydantoin moiety were designed, synthesized and evaluated for their antibacterial activity. The key compounds 7 and 9 were synthesized by the knoevenagel condensation of intermediate aldehyde 5 with rhodanine derivatives 6a−6b. The preliminary study showed that compounds 7, 9 and 10e exhibited potent antibacterial activity with MIC values of 0.125 µg/mL against S. aureus, MRSA, MSSA, LREF and VRE pathogens, using linezolid and radezolid as the positive controls. The most promising compound 10e exhibited potent antibacterial activity against tested clinical isolates of MRSA, MSSA, VRE and LREF with MIC values in the range of 0.125–0.5 µg/mL, and the potency of 10e against clinical isolates of LREF was 64-fold higher than that of linezolid. Moreover, compound 10e was non-cytotoxic with an IC50 value of 91.04 μM against HepG2 cell. Together, compound 10e might serve as a novel antibacterial agent for further investigation.

1217. Staphylococcus Protein A (spa) Typing Demonstrates Genetic Heterogeneity of Methicillin-Susceptible Staphyloccus aureus (MSSA) in a Neonatal Intensive Care Unit (NICU)

BackgroundIn the NICU, MSSA is a more prevalent pathogen than MRSA, but optimal infection prevention and control strategies for MSSA are not yet well understood. There are likely multiple routes of MSSA acquisition given its role as normal flora and its detection in the anovaginal tract of pregnant women. We describe the molecular epidemiology of MSSA in our NICU during a yearlong surveillance effort.MethodsIncluded infants were hospitalized in a university-affiliated level III-IV NICU from January to December 2017 (1032 admissions) and had positive clinical and/or surveillance cultures for MSSA. Infants admitted at ≥7 days of age were screened for MSSA colonization by culturing the anterior nares and three skin sites. All infants in the NICU were screened twice monthly. Spa typing was performed to genetically characterize isolates.ResultsDuring the study period, MSSA was identified in 187 infants (18 at admission, 145 by twice monthly surveillance, and 24 from clinical cultures). In all, 269 MSSA isolates (245 surveillance and 24 clinical isolates) from 166 infants were spa typed. Sixty-two MSSA spa types were identified; 31 (50%) were each detected in only one infant. The incidence of the nine most common spa types is shown (Figure 1); t279 (13%), t002 (8%), and t1451 (6%) had the highest incidence. t1451 and t571 belong to ST398, a common MSSA clone in the local community. The epidemiology of spa types varied; e.g., incident cases of t279 was detected in 10 months, t1451 was detected in 6 months and t148 in 3 months. Among the 14 sets of twins and triplets with MSSA isolates, 12 (86%) shared the same spa type as their sibling(s). Of the 58 infants with >1 MSSA isolate, 12 (21%) acquired new spa-types. No spa type(s) predominated in the 19 episodes of invasive infections. In 6 infants with both colonizing and invasive isolates, colonizing and invasive isolates were the same spa type(s) in 5.ConclusionSpa typing demonstrated that MSSA isolates in our NICU exhibited substantial genetic heterogeneity. While these data do not elucidate acquisition route(s), they suggest infants are acquiring MSSA from multiple sources, likely including family members and the local community. Ongoing sequencing studies are examining common spa types to further understand transmission dynamics.Figure 1.Disclosures A. C. Uhlemann, Merck: Investigator, Grant recipient

1342. Comparison of Lysin CF-301 (Exebacase) Activity Against S. aureus Isolates From Bacteremic Patients Enrolled in a Phase 2 Study (CF-301-102) to Contemporary Surveillance Isolates

BackgroundCF-301 (exebacase) is a novel, recombinantly produced, bacteriophage-derived lysin (cell wall hydrolase) which is the first lysin to enter Phase 2 (Ph2) in the United States and is being studied for the treatment of S. aureus bacteremia including endocarditis. We examined the activity of CF-301 against methicillin-sensitive and methicillin-resistant S. aureus (MSSA and MRSA) isolates from participants in the ongoing, CF-301 “first in-patient’ Ph2 study (NCT03163446) in comparison to activity reported in a recent surveillance study.MethodsPatients with complicated bacteremia or endocarditis caused by S. aureus were enrolled into Study CF-301-102 at study centers in the United States and Guatemala between 2017 and 2018. Baseline isolates from blood cultures were collected prior to administration of CF-301. The activity of CF-301 activity against the first 36 isolates of MRSA (14) and MSSA (22) was determined at a central laboratory. Surveillance data for CF-301 were generated against 300 isolates of MRSA (150) and MSSA (150) collected between 2016 and 2017 from patients with various infection types at US centers. CF-301 MICs were determined using the modified broth microdilution method approved by the CLSI for CF-301.Results In vitro activity of CF-301 against S. aureus isolates from Ph2 Study CF-301-102 and surveillance MIC (µg/mL) Organism Source N 0.125 0.25 0.5 1 2 MIC 50 MIC 90 MSSAPh222161320.50.5Surveillance150291570.51MRSAPh21431010.50.5Surveillance1505108370.51The CF-301 MICs of baseline patient isolates from the Ph2 study ranged from 0.125 – 1 µg/mL. CF-301 MIC50/90 values for all MSSA and MRSA isolates were 0.5 µg/mL. CF-301 MICs reported in a recent the surveillance study ranged from 0.25–1 µg/mL, with MIC50/90 values of 0.5/1 µg/mL.ConclusionThe activity of CF-301 against baseline S. aureus isolates from blood cultures obtained from bacteremic patients enrolled in the Ph2 study was similar to that observed in the surveillance study. Based on data from previously presented exposure target attainment animal studies, PK/PD modeling and preliminary non-clinical breakpoint assessments, we expect that strains with MIC values of ≤1 µg/mL will be susceptible to the clinical CF-301 dose (0.25mg/kg) under study in Ph2.Disclosures D. Anastasiou, ContraFect Corporation: Consultant, Consulting fee. A. Jandourek, ContraFect Corporation: Employee, Salary. C. Cassino, ContraFect Corporation: Employee, Salary. R. Schuch, ContraFect Corporation: Employee, Salary.

1388. Dose Discrimination for ASN100: Bridging from Rabbit Survival Data to Predicted Activity in Humans Using a Minimal Physiologically Based Pharmacokinetic (mPBPK) Model

BackgroundASN100 is a combination of two co-administered fully human monoclonal antibodies (mAbs), ASN-1 and ASN-2, that together neutralize the six cytotoxins critical to S. aureus pneumonia pathogenesis. ASN100 is in development for prevention of S. aureus pneumonia in mechanically ventilated patients. A pharmacometric approach to dose discrimination in humans was taken in order to bridge from dose-ranging, survival studies in rabbits to anticipated human exposures using a mPBPK model derived from data from rabbits (infected and noninfected) and noninfected humans [IDWeek 2017, Poster 1849]. Survival in rabbits was assumed to be indicative of a protective effect through ASN100 neutralization of S. aureus toxins.MethodsData from studies in rabbits (placebo through 20 mg/kg single doses of ASN100, four strains representing MRSA and MSSA isolates with different toxin profiles) were pooled with data from a PK and efficacy study in infected rabbits (placebo and 40 mg/kg ASN100) [IDWeek 2017, Poster 1844]. A Cox proportional hazards model was used to relate survival to both strain and mAb exposure. Monte Carlo simulation was then applied to generate ASN100 exposures for simulated patients given a range of ASN100 doses and infection with each strain (n = 500 per scenario) using a mPBPK model. Using the Cox model, the probability of full protection from toxins (i.e., predicted survival) was estimated for each simulated patient.ResultsCox models showed that survival in rabbits is dependent on both strain and ASN100 exposure in lung epithelial lining fluid (ELF). At human doses simulated (360–10,000 mg of ASN100), full or substantial protection is expected for all four strains tested. For the most virulent strain tested in the rabbit pneumonia study (a PVL-negative MSSA, Figure 1), the clinical dose of 3,600 mg of ASN100 provides substantially higher predicted effect relative to lower doses, while doses above 3,600 mg are not predicted to provide significant additional protection.ConclusionA pharmacometric approach allowed for the translation of rabbit survival data to infected patients as well as discrimination of potential clinical doses. These results support the ASN100 dose of 3,600 mg currently being evaluated in a Phase 2 S. aureus pneumonia prevention trial. Disclosures C. M. Rubino, Arsanis, Inc.: Research Contractor, Research support. L. Stulik, Arsanis Biosciences GmbH: Employee, Salary. H. Rouha, 3Arsanis Biosciences GmbH: Employee, Salary. Z. Visram, Arsanis Biosciences GmbH: Employee, Salary. A. Badarau, Arsanis Biosciences GmbH: Employee, Salary. S. A. Van Wart, Arsanis, Inc.: Research Contractor, Research support. P. G. Ambrose, Arsanis, Inc.: Research Contractor, Research support. M. M. Goodwin, Arsanis, Inc.: Employee, Salary. E. Nagy, Arsanis Biosciences GmbH: Employee, Salary.

2376. In Vitro Activities of Ceftaroline and Comparator Agents Against Bacterial Pathogens Collected From Patients With Skin and Skin Structure Infections in Latin America: AWARE Surveillance Program 2017

BackgroundThe parenteral cephem ceftaroline (CPT) fosamil is approved for the treatment of patients with skin and skin structure infections (SSSIs) caused by Staphylococcus aureus (both methicillin-susceptible [MSSA] and methicillin-resistant [MRSA] isolates), β-hemolytic streptococci (Streptococcus pyogenes, Streptococcus agalactiae), and select species of Enterobacteriaceae (Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca). Limited data have been published on the in vitro activity of CPT against recent clinical isolates cultured from patients with SSSIs in Latin America (LA).MethodsStandard CLSI broth microdilution MIC determinations (M07) were performed with CPT and comparator agents. MICs were interpreted using current CLSI M100 MIC breakpoints. Clinically relevant, non-duplicate, isolates cultured from patients with SSSIs in 6 countries in LA in 2017 were tested by the AWARE Surveillance Program central laboratory (IHMA). In total, 1,435 non-duplicate isolates of MSSA, MRSA, β-hemolytic streptococci, and Enterobacteriaceae were tested: Argentina (n = 349/24.3% of all isolates tested), Brazil (114/7.9%), Chile (153/10.7%), Columbia (175/12.2%), Mexico (339/23.6%), and Venezuela (305/21.3%).ResultsCPT activity is summarized in the following table.CPT MIC Breakpoints (µg/mL)CPT MIC (µg/mL)CPT MIC InterpretationBacteria n S | I | RMIC50MIC90% S% I% RMSSA354≤1 | 2 | ≥40.250.510000MRSA389≤1 | 2 | ≥40.5195.14.90β-Hemolytic streptococcia130≤0.5 | − | −0.0080.015100−−Enterobacteriaceae, All562≤0.5 | 1 | ≥20.5>12855.33.940.8 Enterobacteriaceae, ESBL screen-negative358≤0.5 | 1 | ≥20.12186.65.97.5 a S. pyogenes (n = 90), S. agalactiae (n = 26), and S. dysgalactiae (n = 14).ConclusionOverall, 100% of MSSA and 95.1% of MRSA from LA were susceptible to CPT (MIC ≤1 µg/mL); 19 isolates of MRSA were CPT-intermediate (MIC 2 µg/mL) with 17 of the 19 isolates being from Chile; no CPT-resistant MRSA were observed. All β-hemolytic streptococci and 86.6% of ESBL-negative Enterobacteriaceae were also susceptible to CPT. CPT continues to demonstrate potent in vitro activity against clinically relevant pathogens associated with SSSIs for patients in LA.Disclosures M. Hackel, Pfizer Inc.: Consultant, Consulting fee. IHMA, Inc.: Employee, Salary. J. Karlowsky, IHMA, Inc.: Consultant, Consulting fee. D. Sahm, Pfizer Inc.: Consultant, Consulting fee. IHMA, Inc.: Employee, Salary. G. G. Stone, Pfizer Inc.: Employee, Salary. AstraZeneca: Former Employee and Shareholder, Salary.

Prevalence and Characterization of Staphylococcus aureus Isolated From Women and Children in Guangzhou, China.

The prevalent Staphylococcus aureus clones and antibiotic susceptibility profiles are known to change dynamically and geographically; however, recent S. aureus strains causing infections in women and children in China have not been characterized. In this study, we analyzed the molecular epidemiology and antimicrobial resistance of S. aureus isolated from patients in four centers for women and children in Guangzhou, China. In total, 131 S. aureus isolates (100 from children and 31 from women) were analyzed by spa typing, multi-locus sequence typing, virulence gene and antimicrobial resistance profiling, staphylococcal chromosomal cassette mec typing, and mutation analyses of rpoB. A total of 58 spa types, 27 sequence types (STs), and 10 clonal complexes (CCs) were identified. While CC59 (ST59-IV, 48.8%; ST338-III, 35.7%) and CC45 (ST45-IV, 100%) were the major clones (84.4%) among MRSA isolates, CC5 (ST188, 24.3%; ST1, 21.6%) and CC398 (ST398, 70%) were the major ones (70.1%) among MSSA isolates. ST338-MRSA-III mostly found in pus but hardly in respiratory tract samples while ST45-MRSA-IV was on the opposite, even though they both found in blood and cerebrospinal fluid sample frequently. Staphylococcal enterotoxin genes seb-seq-sek were strongly associated with ST59 and ST338, while sec was associated with ST45, ST121, ST22, and ST30. All ST338, ST1232, and SCCmec III isolates carried lukF/S-PV genes. A total of 80% of ST338 isolates were resistant to erythromycin, clindamycin, and tetracycline. All ST45 isolates exhibited intermediate or complete resistance to rifampicin. In total, 481 HIS/ASN mutations in rpoB were found in rifampicin-resistant or intermediate-resistant isolates. ST338-III and ST45-IV emerged as two of three major clones in MRSA isolates from women and children in Guangzhou, China, though ST59-MRSA-IV remained the most prevalent MRSA clone. Clonal distribution of S. aureus varied, depending on the specimen source. Virulence genes and antibiograms were closely associated with the clonal lineage. These results clarified the molecular epidemiology of S. aureus from women and children in Guangzhou, China, and provide critical information for the control and treatment of S. aureus infections.

Staphylococcus aureus osteoarticular infections in children: an 8-year review of molecular microbiology, antibiotic resistance and clinical characteristics

To investigate the clinical, phenotypic and genotypic characteristics of Staphylococcus aureus strains causing osteoarticular infections in a large paediatric series. Medical records of children who were hospitalized with the diagnosis of community-associated S. aureus (CA-SA) osteomyelitis and/or septic arthritis in the two major tertiary paediatric hospitals of Athens during an 8-year period (2007-2015) were reviewed, and S. aureus isolates were analysed regarding antimicrobial resistance, detection of pathogenicity genes and genotyping using SCCmec, agr typing, PFGE and MLST. During the study period, 123 children with CA-SA osteoarticular infections were identified, and methicillin-resistant S. aureus (MRSA) accounted for 44 of these (35.8 %). Children with MRSA infection had a significantly higher admission rate to the ICU (5.7 vs 0 %, P=0.04) and longer duration of hospitalization (21.6 vs 16.7 days, P=0.04). Sixty-eight isolates [42 (methicillin-sensitive S. aureus) MSSA and 26 MRSA] were available for molecular analysis. All MRSA strains were mecA-positive and most carried the SCCmec IV cassette (23/26, 88 %) and belonged to the PFGE type C (24/26, 92.3 %), agr type 3 (24/26, 92.3 %) and the MLST ST80 clone (24/26, 92.3 %). In contrast, MSSA strains showed polyclonality by PFGE and agr typing. Regarding pathogenicity genes, MRSA vs MSSA isolates showed higher detection rates of PVL (96.2 vs 4.8 %, P<0.0001) and fib (80.8 vs 50 %, P=0.02). In our study a considerable number of S. aureus osteoarticular infections were due to CA-MRSA isolates, most of which belonged to the ST80 clone and had a higher incidence of specific virulence factors, entailing higher ICU admission rates and a longer duration of hospitalization.

Investigating the potential use of an Antarctic variant of Janthinobacterium lividum for tackling antimicrobial resistance in a One Health approach

The aim of this paper is to describe a new variant of Janthinobacterium lividum - ROICE173, isolated from Antarctic snow, and to investigate the antimicrobial effect of the crude bacterial extract against 200 multi-drug resistant (MDR) bacteria of both clinical and environmental origin, displaying various antibiotic resistance patterns. ROICE173 is extremotolerant, grows at high pH (5.5–9.5), in high salinity (3%) and in the presence of different xenobiotic compounds and various antibiotics. The best violacein yield (4.59 ± 0.78 mg·g−1 wet biomass) was obtained at 22 °C, on R2 broth supplemented with 1% glycerol. When the crude extract was tested for antimicrobial activity, a clear bactericidal effect was observed on 79 strains (40%), a bacteriostatic effect on 25 strains (12%) and no effect in the case of 96 strains (48%). A very good inhibitory effect was noticed against numerous MRSA, MSSA, Enterococci, and Enterobacteriaceae isolates. For several environmental E. coli strains, the bactericidal effect was encountered at a violacein concentration below of what was previously reported. A different effect (bacteriostatic vs. bactericidal) was observed in the case of Enterobacteriaceae isolated from raw vs. treated wastewater, suggesting that the wastewater treatment process may influence the susceptibility of MDR bacteria to violacein containing bacterial extracts.