MRSA Isolates Research Articles

Methicillin- and Vancomycin-Resistant Staphylococcus aureus From Humans and Ready-To-Eat Meat: Characterization of Antimicrobial Resistance and Biofilm Formation Ability.

Methicillin-resistant and vancomycin-resistant Staphylococcus aureus (MRSA and VRSA) are zoonotic life-threatening pathogens, and their presence in food raises a public health concern. Yet, scarce data are available regarding MRSA and VRSA in both ready-to-eat (RTE) meat and food handlers. This study was undertaken to determine the frequency, antimicrobial resistance, and biofilm-forming ability of MRSA and VRSA isolated from RTE meat (shawarma and burger) and humans (food handlers, and hospitalized patients) in Zagazig city, Sharkia Governorate, Egypt. We analyzed 176 samples (112 human samples: 72 from hospitalized patients and 40 from food handlers, 64 RTE meat samples: 38 from shawarma and 26 from burger). Using phenotypic, PCR-based identification of nuc gene and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), 60 coagulase-positive S. aureus (COPS) isolates were identified in the samples as follow: RTE meat (15/64, 23.4%), hospitalized patients (33/72, 45.8%) and food handlers (12/40, 30%). All the COPS isolates were mecA positive (and thus were classified as MRSA) and multidrug resistant with multiple antibiotic resistance indices ranging from 0.25 to 0.92. Overall, resistance to cefepime (96.7%), penicillin (88.3%), were common, followed by ampicillin-sulbactam (65%), ciprofloxacin (55%), nitrofurontoin (51.7%), and gentamicin (43.3%). VRSA was detected in 30.3% of COPS hospitalized patient’s isolates, 26.7% of COPS RTE meat isolates and 25% of COPS food handler’s isolates. VanA, vanB, or both genes were detected in 64.7, 5.9, and 29.4% of all VAN-resistant isolates, respectively. The majority of the COPS isolates (50/60, 83.3%) have biofilm formation ability and harbored icaA (76%), icaD (74%), icaC (50%), and icaB (46%) biofilm-forming genes. The bap gene was not detected in any of the isolates. The ability of MRSA and VRSA isolates to produce biofilms in addition to being resistant to antimicrobials highlight the danger posed by these potentially virulent microorganisms persisting in RTE meat, food handlers, and patients. Taken together, good hygiene practices and antimicrobial surveillance plans should be strictly implemented along the food chain to reduce the risk of colonization and dissemination of MRSA and VRSA biofilm-producing strains.

The alarming coincidence of toxin genes with staphylococcal cassette Chromosome mec (SCCmec) in clinical MRSA isolates

Staphylococcus aureus is an opportunistic pathogen causing infections with high morbidity and mortality. MRSA isolates which harbor Staphylococcal Cassette Chromosome mec (SCCmec) and express various types of toxins are the most serious strains. Type of SCCmec and common toxin genes (TGs) among MRSA isolates were investigated in the current study. SCCmec and TGs were detected by multiplex-PCR. Possible correlations between SCCmec and TGs were elucidated statistically using IBM-SPSS software. Staphylococcus-enterotoxins (SEs) were sequenced to investigate their genetic relatedness using Sanger-sequencing, and MEGAX software.MRSA were detected in 124 isolates, 67 of MRSA isolates (54 %) were harboring a single SCCmec with 40, 21, 5 and 1 isolate for SCCmec II, SCCmec III, SCCmec IV, and SCCmec V, respectively. Furthermore, Four isolates (3.2 %) had both SCCmec II and SCCmec IV. The highest incidence of TGs was recorded for sea (40.3%) and etb (34.6%) genes. Statistically, moderate correlation between toxins and SCCmec type and between presence of toxin genes and severity of infections were detected. All SEs sequences were correlated, sea and see genes were more conserved. Isolates from serious cases revealed different degrees of nucleotide and amino acid substitution among seb, sec, and tsst genes, which might contribute to their increased virulence. This study improves our understanding of S. aureus toxin profile in relation to SCCmec type, and highlight their possible roles in virulence.

Investigating the relation between resistance pattern and type of Staphylococcal cassette chromosome mec (SCCmec) in methicillin-resistant Staphylococcus aureus.

Background and Objectives:MRSA became a widely recognized cause of mortality worldwide with necessity of its epidemiological pattern study. Typing of MRSA isolates was performed molecularly based on SCCmec type and relation to resistance pattern was investigated.Materials and Methods:Out of 200 clinical specimens, S. aureus was detected phenotypically and confirmed as MRSA by PCR in 124 isolates obtained from associated laboratories of different hospitals of Zagazig, during 2018–2019. Antimicrobial resistance pattern was detected and MRSA SCCmec was typed by two methods.Results:S. aureus rate was high in wounds, sputum, blood, and urine isolates. Antimicrobial resistance rates against cefotaxime, tetracycline, gentamicin, ciprofloxacin, erythromycin, azithromycin, clindamycin, chloramphenicol, sulfamethoxazole-trimethoprim, linezolid and vancomycin were 82.3%, 65.3%, 56.4%, 45.1%, 37.1%, 32.3%, 32.3%, 25%, 7.3%, 2.4% and 0%, respectively. Multiplex-PCR(M-PCR) was able to detect SCCmec element among 57% of isolates classified as SCCmec II (n=40), III (n=21), IVa (n=3), IVd (n=2), V(n=1), and four isolates contain both SCCmec II and SCCmec IV. Traditional typing by PCR for mec and ccr gene complexes was almost concordant with M-PCR. Furthermore, it was able to identify SCCmec types VI, IX, and XIV among 1, 3 and 18 isolates, respectively. No Statistical correlation was established between type of cassette and rate of antimicrobial resistance. Phylogenetic analysis reveals that all ccr types were related to each other and no significant variation in the same ccr type of different SCCmec cassettes.Conclusion:Most MRSA isolates were MDR reflecting antimicrobials misuse. Detection of various SCCmec types among MRSA isolates indictae the complexity of MRSA epidemiology and increase chance for gene sharing creating new types. The presented investigation was important in understanding MRSA epidemiology and diversity in Egypt providing advice for improving therapeutic protocols.

STUDY OF METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS IN POSTSURGICAL SUTURE INFECTIONS IN A TERTIARY CARE CENTRE OF NORTH INDIA.

Introduction: MRSA has been recognised as an important nosocomial pathogen globally and is endemic in India. Its incidence varies from 25 % in 3 western part to 50 % in Southern part of India . Post operative wound infections continues to be a major source of morbidity and mortality for patients undergoing operative procures. To nd out the incidence of MRSA in post-surgic Aim and Objectives: al suture infections and to determine its susceptibility pattern by using a battery of antibiotics. Tota Material and method: l 100 pus samples were collected from surgical site infections of admitted patients applying inclusion and exclusion criteria of department of surgery and processed in department of microbiology of Darbhanga Medical College and Hospital. Isolation of MRSA is done by routine laboratory culture method by using Mannitol Salt Agar and Cefoxitin disc 30µg(Hi-media). Out of 100 samples collected from patients from 54, Result: Staph. aureus were isolated i.e., 54%. Whereas, out of 54 isolated Staph. aureus, 24 (44.4%) were MRSA, whereas it constitutes 24% of total study subjects. MRSA infected Male (62.5%) more than female (37.5%). During antibiotic sensitivity testing MRSA found sensitive against Vancomycin and Linezolid. Conclusion: This study shows that MRSA is one of the major infectant in post operative wound infection and this is worrisome as very limited antibiotic shows sensitivity against it.

Genomic analyses of Staphylococcus aureus isolated from yaks in Ganzi Tibetan Autonomous Prefecture, China.

To investigate the transmission and origination of MRSA in livestock with limited antimicrobial use. Yak (Bos grunniens) herds in Ganzi Tibetan Autonomous Prefecture, China were chosen for sampling. The yaks from all 18 districts of Ganzi were sampled (anal swabs, n = 657; nasal swabs, n = 634). Based on the WGS data of 83 Staphylococcus aureus isolates, the novel structure of the yak S. aureus population was described. Phylogenetic analyses were utilized for determining the origin of the MRSA lineage in yaks. The yak S. aureus population consisted of 11 STs, 6 of which were previously undescribed, with ST6267 being the predominant novel ST. These isolates were generally susceptible to most of the tested antibiotics and lacked the associated antimicrobial resistance genes (ARGs) but showed high penicillin MIC values (MIC90 = 32 mg/L), which were consistent with the high positivity rate for blaZ (61/83). The MRSA identified in yaks were all ST59 and most likely of human origin. The yak ST59 MRSA each carried the human immune evasion cluster (IEC) while lacking the ARGs that are identified in the majority of reported Chinese human ST59 MRSA isolates [erm(B), ant6-Ia and aph(3″)-III]. The yak herds living on the Qinghai-Tibet Plateau are important livestock and follow the traditional free-grazing farming model. We surveyed the yak S. aureus population and found that all the yak MRSA isolates belonged to the lineage that might originate from the prevalent community-acquired MRSA ST59 in China. From a 'One Health' perspective, the transmission of human MRSA to farming animals with limited antimicrobial exposure highlights the multiple roles of animals in the expansion of MRSA.

ARE THE DISINFECTANTS USED IN HOSPITALS ALSO EFFECTIVE ON BACTERIA THAT CAUSE NOSOCOMIAL INFECTIONS?: A UNIVERSITY HOSPITAL INVESTIGATION

Objective: Determining the disinfectant activity regularly will result in proper disinfection. In our study, it was aimed to determine the efficacy, effective concentrations and durations of some disinfectants used in Trakya University Hospital against nosocomial bacteria isolated from the same center. Material and Method: MRSA, VRE, Klebsiella pneumoniae and Acinetobacter baumannii isolates and 10 different disinfectants supplied from the same center were included in the study. Susceptibility tests and Qualitative Suspension Test were applied through the guidelines of CLSI M100-S25 and TS/EN/1040:2005 (formerly TS/EN/1040:1999), respectively. Qualitative Suspension Test was modified by using D/E Neutralizing Broth instead of adding a neutralizing agent. Result and Discussion: As a result, it was determined that all isolates were susceptible in the application conditions. However, peracetic acid, sodium dichloroisocyanurate, non-ionic active agent and sodium hypochlorite containing disinfectants being used in the hospital were not effective against some strains isolated from the hospital. Even the resistance of a single isolate to the application conditions of a disinfectant may lead to selection and proliferation of the strains and this may cause hospital infections. Our results might provide a reference to indicate the importance of selecting appropriate disinfectants and appropriate conditions for cleaning and disinfection in hospitals.

New update on molecular diversity of clinical Staphylococcus aureus isolates in Iran: antimicrobial resistance, adhesion and virulence factors, biofilm formation and SCCmec typing.

Staphylococcus aureus is often considered as a potential pathogen and resistant to a wide range of antibiotics. The pathogenicity of this bacterium is due to the presence of multiple virulence factors and the ability to form biofilm. SCCmec types I, II and III are mainly attributed to HA-MRSA, while SCCmec types IV and V have usually been reported in CA-MRSA infections. In this study, we performed a cross-sectional study to determine the antimicrobial resistance, adhesion and virulence factors, biofilm formation and SCCmec typing of clinical S. aureus isolates in Iran. S. aureus isolates were identified using microbiological standard methods and antibiotic susceptibility tests were performed as described by the Clinical and Laboratory Standards Institute (CLSI) guidelines. Inducible resistance phenotype and biofilm formation were determined using D-test and tissue culture plate methods, respectively. Multiplex-PCRs were performed to detect adhesion and virulence factors, antibiotic resistance genes, biofilm formation and SCCmec typing by specific primers. Among 143 clinical samples, 67.8% were identified as MRSA. All isolates were susceptible to vancomycin. The prevalence of cMLSB, iMLSB and MS phenotypes were 61.1%, 22.2% and 14.8%, respectively. The TCP method revealed that 71.3% of isolates were able to form biofilm. The predominant virulence and inducible resistance genes in both MRSA and MSSA isolates were related to sea and ermC respectively. SCCmec type III was the predominant type. Data show the high prevalence rates of virulence elements among S. aureus isolates, especially MRSA strains. This result might be attributed to antibiotic pressure, facilitating clonal selection.

Identifying a therapeutic target for vancomycin against staphylococci in young infants.

To determine the therapeutic target of vancomycin in young infants with staphylococcal infections. Retrospective data were collected for infants aged 0 to 90 days with CoNS or MRSA bacteraemia over a 4 year period at the Royal Children's Hospital Melbourne, Australia. Vancomycin broth microdilution MICs were determined. A published pharmacokinetic model was externally validated using the study dataset and a time-to-event (TTE) pharmacodynamic model developed to link the AUC of vancomycin with the event being the first negative blood culture. Simulations were performed to determine the trough vancomycin concentration that correlates with a 90% PTA of the target AUC24. Thirty infants, 28 with CoNS and 2 with MRSA bacteraemia, who had 165 vancomycin concentrations determined were included. The vancomycin broth microdilution MIC was determined for 24 CoNS and 1 MRSA isolate, both with a median MIC of 1 mg/L (CoNS range = 0.5-4.0). An AUC0-24 target of ≥300 mg/L·h or AUC24-48 of ≥424 mg/L·h. increased the chance of bacteriological cure by 7.8- and 7.3-fold, respectively. However, AUC0-24 performed best in the pharmacokinetic-pharmacodynamic model. This correlates with 24 to 48 h trough concentrations of >15-18 mg/L and >10-15 mg/L for 6- and 12-hourly dosing, respectively, and can be used to guide vancomycin therapy in this population. An AUC0-24 ≥300 mg/L·h or AUC24-48 ≥424 mg/L·h was associated with an increase in bacteriological cure in young infants with staphylococcal bloodstream infections.

Molecular characterization of methicillin-resistant Staphylococcus aureus (MRSA)isolated from bovine wounds

Staphylococcus aureus (S. aureus) is a Gram-positive coccus with golden-colored colonies 0.5-1.5 ?m in diameter. It is an opportunistic pathogen and colonizes as healthy flora. When the host defense system is breached it provides a source for the introduction of (Methicillin-resistant S. aureus) MRSA. The incorporation of the mecA gene shift S. aureus into MRSA, mecA is a primary gene for the confirmation of MRSA, so, it is used as a useful marker to determine Methicillin resistance in S. aureus. In this study, we investigated the molecular characterization of mecA, Panton-Valentine Leukocidin (PVL), and 16S rRNA genes in MRSA to determine diversity, phylogenetic analysis, and multidrug resistance (MDR) of MRSA isolated from chronic bovine wounds. A total of 8 antibiotics were used for MDR profiling and the results obtained are as follows: 100% of MRSA isolates were resistant to Augmentin and Cefipime, 81.8% to Vancomycin and Tetracyclin, 36.4% to Streptomycin and Ciprofloxacin, Azithromycin 54.5 and 0% to Chloramphenicol which warrants that it?s the best antibiotic according to this study. Multiplex PCRs were performed for the confirmation of targeted genes and diversity analysis. The diversity of MRSA in the bovine population was 22% (11/50) on the microbiological scale that considered high as compared to reported data. When the PCR of MRSA isolates was performed, there was a unique phenomenon observed i.e., no mecA gene was present in 2 isolates 18.18% (2/11) which connotes the importance of molecular methods/PCR for the identification of microbes. The prevalence of the PVL gene was 18.18%, comparatively high as compared to previous studies conducted on bovine chronic wounds. When the Sanger sequencing of 16S rRNA of MRSA isolates was performed there was a change of one nucleotide identified (C>T) at position 1031. After performing phylogenetic analysis with S. aureus of different countries distinct and separate dendrogram was obtained which differentiates the Pakistani S. aureus isolates from other countries.

Biofilm-forming ability and methicillin resistance among Staphylococci isolated from various surfaces in community settings

Biofilm-forming ability and sensitivity to antibiotic methicillin of staphylococci outside the healthcare facilities is not sufficiently explored. The aim of this study was to examine the biofilm-forming capacity of staphylococci on various metal, plastic and leather surfaces in our living and working environment and the association between their biofilm production and methicillin resistance. Detection of methicillin resistance in staphylococci isolates were examined by cefoxitin disc diffusion test. Production of bacterial biofilms was investigated by two phenotypic methods: crystal violet (CV) tube-adherence method and Congo red agar (CRA) plate method. A total of 88 staphylococci isolates, 47 (53.41%) of S. aureus and 41 (46.59 %) of S. epidermidis strains were recovered from 100 collected samples. Among them, 35 methicillin-resistant strains (20 MRSA and 15 MRSE) were detected. Applying the CV tube adherence method, 21 (39.62%) MRSA and MRSE isolates were positive for biofilm production, while using the CRA method 15 (44.12%) MRSA and MRSE strains were detected as biofilm producers. Statistical analysis did not find association between biofilm production ability and methicillin resistance in both applied methods for a significance level of 0.05. The study shows that different objects and surfaces contaminated with biofilm-forming staphylococci, including MRSA and MRSE, may serve as environmental source of infection for long periods of time.

MRSA in Raw Milk: Isolation, Molecular Characterization, and Antibiotic Profiling

A total of 100 milk samples were randomly collected from dairy cows before milking to investigate the presence of MRSA using selective medium (ORSAB) beside detection of some resistance genes by PCR and finally determine the antibiotic profile of the recovered isolates. It was found that the overall percentage of isolation of MRSA was 24% (24/100), (25.8%) 16/62 in milk samples of mastitic cows and (21.1%) 8/38 in raw milk samples of free cows. Molecular characterization of MRSA strains showed that 79.2% (19/24) were harbored mecA gene while none of them harbored mecC gene. In addition, MRSA isolates showed high resistance to cefoxitin (79.2) followed by Tetracycline (33.3%), Vancomycin (20.8%) and Linezolid (15.5%). Whereas the tested MRSA strains showed higher susceptibility to Linezolid (87.5%) followed by Vancomycin (79.2%) and Tetracycline (66.7%). According to the recorded results in the present study, it is concluded that cow’s milk played a significant role in transmission and dissemination of MRSA that may create the opportunity for the transmission of such bacteria to consumers.

The antimicrobial activity of ceftobiprole against Methicillin-resistant Staphylococcus aureus and multi-drug resistant Pseudomonas aeruginosa: A large tertiary care university hospital experience in Riyadh, Saudi Arabia.

Objectives:To assess the antibacterial activity of ceftobiprole against Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (P. aeruginosa) from various body specimen types and different patterns of resistance.Methods:A retrospective cohort study with a total of 49 MRSA and 99 P. aeruginosa isolated in the Microbiology Laboratory at King Saud University Medical City, Riyadh, Saudi Arabia, between 2018-2019, were used. Isolates were randomly selected from various specimen types. The minimum inhibition concentration (MIC) of ceftobiprole was determined by E-test. Breakpoints carried out by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) were used to assess antibiotic susceptibility.Results:Approximately 100% of the MRSA isolates were susceptible with MIC50/90 value of 1/1.5 mg/L while 69.8% of multi-drug resistant (MDR) P. aeruginosa isolates were resistant with MIC50/90 value of 16/32 mg/L.Conclusion:The excellent activity of ceftobiprole against MRSA would have major implications in management of the patients with serious infections, as an empirical treatment or alternative to vancomycin. Ceftobiprole has a very low activity against MDR P. aeruginosa, and its susceptibility should be tested prior to use for treatment.

First isolation of ST398 methicillin-resistant Staphylococcus aureus carrying staphylococcal cassette chromosome mec type IVd from pig ears in Japan.

The emergence and increasing prevalence of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) are a global concern. To investigate the prevalence and characteristics of sequence type 398 (ST398) MRSA in pig ears, 102 pig’s ears were collected from 102 animals shipped from 51 farms at an abattoir. Eight ST398 MRSA isolates were isolated from the ears of eight pigs shipped from seven farms. Of the eight ST398 isolates, seven had the staphylococcal cassette chromosome mec (SCCmec) type IVd and these were obtained from seven pigs shipped from six farms. Single nucleotide polymorphisms ranging from 13 to 26 were observed in the core-genome regions in the seven SCCmec type IVd isolates. We believe that this is the first report on the isolation of ST398 MRSA SCCmec type IVd in Japan.

Prevalence of Staphylococci in Environmental Surfaces and Characterization of Isolates by Antibiotic Susceptibility

Objectives: The purpose of the study was to determine the extent of staphylococcal contamination in various environmental sites and to characterize the isolates by antibiotic susceptibility. Methods: A cross-sectional study was conducted and 123 samples were collected from 9 different sites around Kathmandu valley. Isolation of S. aureus was done through cultural and biochemical analysis. Kirby-Bauer disc diffusion test was employed to test the susceptibility of isolates to antibiotics. Results: A total of 25 S. aureus (20.33%) were isolated; among which 12 isolates exhibited methicillin resistance i.e. 48% (MRSA) and 13 isolates were methicillin susceptible, 52% (MSSA). Similarly, 53 Coagulase Negative Staphylococci (CoNS) were isolated; among which 17(32.07%) were resistant to methicillin. The antibiotic resistance patterns of MRSA were reported as: erythromycin(n=2;16.6%.), clindamycin (n=2;16.6%), cotrimoxazole (n=2;16.6%), ciprofloxacin (n=2;16.6%) and gentamicin (n = 1;8.3%). MRCoNS showed high resistance to erythromycin (n=6; 35.2%), followed by co-trimoxazole (n=4; 23.5%), novobiocin (n=4; 23.5%) and ciprofloxacin (n=3; 17.6%). All MRSA and MRCoNS isolates were susceptible to linezolid and clindamycin. Conclusion: This study reports relatively high prevalence of MRSA on environmental surfaces, pre-dominating in areas having heavy crowds. There may be a likely connection between humans and the environment to share MRSA and MSSA.

A Review of Global Epidemiology and Antibiotic Resistance of Staphylococcus Aureus

Background: Staphylococcus aureus is gram-positive cocci, which causes multiple complications such as bone, skin, joint and soft tissue infections. Penicillin was the first antibiotic that showed resistance to S. aureus; however, following penicillin, S. aureus became resistant to Methicillin and became a problem in many parts of the world. Worldwide epidemiology of S. aureus varies by country. In Austria, CA-MRSA accounts for 10% of all MRSA isolates. Many clones of S. aureus were discovered in Asian and as well as in European countries. Many patients in Southeast Asia are infected with various S. aureus variants. Aim: The aim of this study was to review epidemiology and antibiotic resistance of S. aureus in different countries. Results: Previous findings revealed that Panton-Valentine leukeocidin (PVL) genes were present in S. aureus strains. Furthermore, most widely accepted antibiotic resistance genes in clinical isolates of S. aureus strains are mecA. S. aureus spread throughout the hospital and into the community as well. They differ from one another in some ways, such as PVL genes and staphylococcal Chromosomal Cassette Mec (SCCmec) subtyping. Conclusion: It is concluded based on previously published research as well as review articles that different clones are of S. aureus are present in different regions of the world which further shows similar characteristics in some regions while totally different from the clones found in other countries. S. aureus infection can be treated by combining some antibiotics such as Vancomycin with Rifampin and Gentamicin. It can also be avoided by practicing good hand hygiene and avoiding intravenous drugs, which can cause a variety of infections. Keywords: Staphylococcus aureus, MRSA, CA-MRSA, HA-MRSA, Resistance

Phenotypic and Genotypic Characterization of Methicillin, Vancomycin, and Erythromycin-resistant Staphylococcus aureus Isolated from Milk and Dairy Products

Detailed information on the resistance patterns of Staphylococcus aureus (S. aureus) in milk and cheese is strongly required to facilitate risk assessment analysis in case of food poisoning context and to improve therapeutic approaches used in dairy farms. The present study aimed to perform phenotypic and genotypic antimicrobial characterizations of methicillin, vancomycin, and erythromycin-resistant S. aureus isolated from milk and dairy products through screening mecA, vanA, and ermC using molecular PCR amplification technology. Moreover, the association between each genotypic and its related antibiotic resistance phenotypic features within the isolated S. aureus strains were analyzed. Moreover, the current study aimed to study MRSA's ability to form biofilms. Out of 226 milk and dairy product samples collected from different retailers in Giza Governorate, 69.5% of the samples were positive for the presence of S. aureus. The isolation rate of S. aureus strains from cattle milk, sheep milk, white cheese, flamenco, and mesh samples were 79.7%, 76.5%, 56.0%, 40.0%, and 94.7%, respectively. Multidrug-resistant S. aureus (MDR) was detected in 51% of all isolated S. aureus strains. All tested S. aureus strains were sensitive to trimethoprim-sulfamethoxazole, linezolid, ciprofloxacin, and gentamycin. However, their resistance rates against penicillin, oxacillin, vancomycin, erythromycin, tetracycline, clindamycin and chloramphenicol were 62.4%, 65.0%, 44.6%, 45.9%, 21.0%, 14.0%, and 2.5%, respectively. Of the isolated S. aureus strains, 72.6%, 40.1%, and 48.4% were carriers for mecA, vanA, and ermC genes and the amplified products were at 310, 1030, and 295 bp, respectively. Methicillin-resistant S. aureus isolates were detected in 47.1% of all isolated S. aureus strains. The results indicated that 35.0% of the tested S. aureus strains were genotypic vanA gene carriers and phenotypic resistant to vancomycin representing vancomycin-resistant S. aureus strains. Moreover, 42.7% of all isolated S. aureus strains were carriers for ermC gene and were phenotypic resistant to erythromycin representing erythromycin-resistant S. aureus. The presence of mecA, vanA, and ermC genes in S. aureus was statistically associated with their related phenotypic resistance patterns against both penicillin and oxacillin, vancomycin, and erythromycin, respectively. Moreover, along with an increase in the frequency of mecA, vanA, and ermC genes, their phenotypic antibiotic resistance patterns sharply increased with an odd ratio >1. Of MRSA isolates, 6.8% indicated weak biofilm-formation ability, while 93.2% exhibit no biofilm-forming ability.

IDENTIFICATION OF METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS USING TOUCHDOWN PCR AND PHENOTYPIC METHODS FROM PATIENTS AND HOSPITALS ENVIRONMENTS IN DIFFERENT IRAQI CITIES

The study was aimed to evaluate the prevalence of MRSA in some Iraqi hospitals and determine the most powerful methods for identification of MRSA, in order to achieve the, 278 samples were collected from different hospitals in Iraq in various intervals, 204 out of 287 were identified as Staphylococcus aureus by conventional cultural methods and microscopic characteristics and 177 isolates are identified as MRSA by using HiCrome MeReSa Agar Base medium, but 154 of 177 (87%) isolates are methicillin resistance in sensitivity test. MRSA isolates were highly resistant to β-lactam antibiotics and considered multidrug resistant (MDR) in percent of (94.9%). Touchdown PCR used to identify the isolates, 97.05% were identified as Staphylococcus aureus, while 80.88% as MRSA.

1369. Oritavancin Activity Against Methicillin-Resistant S. aureus (MRSA) Isolates Causing Skin and Skin Structure Infections in US Hospitals (2017-2019)

Abstract Background MRSA remains an important cause of community-onset (CA) and nosocomial (NA)- SSSI. Oritavancin (ORI) is a lipoglycopeptide antibiotic with activity against S. aureus, including MRSA and multidrug-resistant (MDR) strains. ORI was approved for clinical use by the US FDA to treat ABSSSI with a single 1,200 mg infusion over 1 (Kimyrsa) or 3 (Orbactiv) hours. This study evaluated the activity of ORI against MRSA isolates causing SSSI from US medical centers. Methods A total of 3,792 S. aureus isolates were consecutively collected (1 per patient) from 31 medical centers in 2017-2019 and tested for susceptibility (S) to ORI and comparators using CLSI broth microdilution methods. Among 1,582 (41.7%) MRSA isolates, 1,379 (87.2%) were reported as CA-MRSA and 203 (12.8%) as NA-MRSA. CA-MRSA isolates were evaluated by resistance (R) subgroups, including clindamycin (CLI-R; n=283; 20.5%), levofloxacin (LEV-R; n=831; 60.3%), MDR (non-susceptible to ≥3 classes of agents; n=816; 59.2%), and extensively drug resistant (XDR; non-susceptible to ≥5 classes; n=47; 3.4%). Results Overall, ORI inhibited 99.9% of all S. aureus isolates at the susceptible breakpoint (≤0.12 mg/L; 99.9% of MSSA and 100% of MRSA; Table). S rates were generally comparable between NA-MRSA and CA-MRSA isolates for ORI (100%S) and linezolid (LZD, 100%S) but lower susceptibility was observed for NA-MRSA compared to CA-MRSA for CLI (71.9%S vs. 79.1%S), LEV (31.0%S vs. 39.4%S), and trimethoprim-sulfamethoxazole (TMP-SMX; 91.1%S vs. 96.9%S). ORI was active against MRSA (MIC50/90, 0.03/0.03 mg/L), regardless of infection status (NA, MIC50/90, 0.03/0.06 mg/L; CA, MIC50/90, 0.03/0.03 mg/L). ORI and LZD remained active (100%S) against all CA-MRSA subsets: CLI-R, LEV-R, MDR, and XDR. Limited activity of CLI (69.9%S) and LEV (13.1%S) was observed against MRSA and each R subset, whereas TMP-SMX had >90%S for all MSSA, MRSA, and R subsets, except XDR. Conclusion ORI exhibited potent in vitro activity against MRSA, regardless of the infection onset or R subset, in contrast to many comparators that lack activity against both, CA-MRSA and NA-MRSA. This in vitro activity, combined with the infusion time options provided to clinicians, suggests ORI is a favorable agent for treating SSSI in the US caused by MRSA, including MDR and XDR strains. Disclosures Cecilia G. Carvalhaes, MD, PhD, AbbVie (formerly Allergan) (Research Grant or Support)Cidara Therapeutics, Inc. (Research Grant or Support)Cipla Therapeutics (Research Grant or Support)Cipla USA Inc. (Research Grant or Support)Melinta Therapeutics, LLC (Research Grant or Support)Pfizer, Inc. (Research Grant or Support) Helio S. Sader, MD, PhD, FIDSA, AbbVie (formerly Allergan) (Research Grant or Support)Basilea Pharmaceutica International, Ltd. (Research Grant or Support)Cipla Therapeutics (Research Grant or Support)Cipla USA Inc. (Research Grant or Support)Department of Health and Human Services (Research Grant or Support, Contract no. HHSO100201600002C)Melinta Therapeutics, LLC (Research Grant or Support)Nabriva Therapeutics (Research Grant or Support)Pfizer, Inc. (Research Grant or Support)Shionogi (Research Grant or Support)Spero Therapeutics (Research Grant or Support) Dee Shortridge, PhD, AbbVie (formerly Allergan) (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, LLC (Research Grant or Support)Shionogi (Research Grant or Support) Jennifer M. Streit, BS, GlaxoSmithKline, LLC (Research Grant or Support)Melinta Therapeutics, LLC (Research Grant or Support)Shionogi (Research Grant or Support)Spero Therapeutics (Research Grant or Support) Rodrigo E. Mendes, PhD, AbbVie (Research Grant or Support)AbbVie (formerly Allergan) (Research Grant or Support)Cipla Therapeutics (Research Grant or Support)Cipla USA Inc. (Research Grant or Support)ContraFect Corporation (Research Grant or Support)GlaxoSmithKline, LLC (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, LLC (Research Grant or Support)Nabriva Therapeutics (Research Grant or Support)Pfizer, Inc. (Research Grant or Support)Shionogi (Research Grant or Support)Spero Therapeutics (Research Grant or Support)

1059. In vitro Activity of Exebacase (CF-301) against Staphylococcus aureus Causing Bacteremia in the United States, Including Multidrug-resistant Subsets

1059. <i>In vitro</i> Activity of Exebacase (CF-301) against <i>Staphylococcus aureus</i> Causing Bacteremia in the United States, Including Multidrug-resistant Subsets

1110. In Vivo Pharmacodynamics of Vancomycin Against Staphylococci in Young Infants

BackgroundCoagulase-negative staphylococci are the predominant pathogen causing late onset sepsis in young infants, however, the pharmacodynamic target for vancomycin therapy is unknown. This study aimed to determine the pharmacodynamic target of vancomycin in young infants with staphylococcal infections.MethodsRetrospective data were collected for infants aged 0-90 days with methicillin-resistant Staphylococcus aureus (MRSA or coagulase-negative staphylococci (CoNS) bacteraemia over a 4-year period at the Royal Children’s Hospital Melbourne, Australia. Vancomycin broth microdilution minimum inhibitory concentrations (MIC) were determined. A published pharmacokinetic model was externally validated using the study dataset and a time-to-event pharmacodynamic model developed using non-linear mixed effects modelling, with the event being the first negative blood culture. Simulations were performed to determine the 24-hour trough vancomycin concentration correlating with a 90% probability target attainment (PTA) of the area under the curve in the first 24-hours (AUC0-24) exceeding the identified target.ResultsThirty infants, 28 with CoNS and two with MRSA bacteraemia, who had 165 vancomycin concentrations determined were included. The vancomycin broth microdilution MIC was determined for 24 CoNS and one MRSA isolate, both with a median MIC of 1 mg/L (CoNS range 0.5 to 4). An AUC0-24 ≥3 00 mg/L·h was associated with a 7.8-fold increase in the chance of bacteriological cure for all staphylococci at any time point compared to an AUC0-24 < 300 mg/L·h (hazard ratio 95% CI: 3.21-18.8). The 24-hour trough concentrations associated with a 90% PTA of achieving this target were > 13-16 mg/L and > 8-12 mg/L for 6 and 12-hourly dosing, respectively. ConclusionOur study found that an AUC0-24 ≥ 300 mg/L·h was associated with a 7.8-fold increase in bacteriological cure in young infants with staphylococcal bloodstream infections. Disclosures All Authors: No reported disclosures