Staphylococcal Cassette Chromosome Mec Research Articles

The Emergence of Linezolid-Resistant Staphylococcus Epidermidis in the COVID-19 Hospitalized Intubated Patients in North Khorasan, Iran.

The present study aimed to investigate secondary bacterial infections among patients infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Coagulase-negative Staphylococci can infect immunocompromised patients. Linezolid resistance among Staphylococcus epidermidis is one of the most critical issues. In 2019, 185 SARS-CoV-2-positive patients who were admitted to North Khorasan Province Hospital (Bojnurd, Iran), were investigated. Patients having positive SARS-CoV-2 reverse transcriptase real-time polymerase chain reaction (RT-PCR) test results, who had a history of intubation, mechanical ventilation, and were hospitalized for more than 48 hours were included. After microbiological evaluation of pulmonary samples, taken from intubated patients with clinical manifestation of pneumonia, co-infections were found in 11/185 patients (5.94%) with S. epidermidis, Staphylococcus aureus, and Acinetobacter baumani, respectively. Remarkably, seven out of nine S. epidermidis isolates were linezolid resistant. Selected isolates were characterized using antimicrobial resistance patterns and molecular methods, such as Staphylococcal cassette chromosome mec (SCCmec) typing, and gene detection for ica, methicillin resistance (mecA), vancomycin resistance (vanA), and chloramphenicol-florfenicol resistance (cfr) genes. All of the isolates were resistant to methicillin, and seven isolates were resistant to linezolid. Nine out of 11 isolated belonged to the SCCmec I, while two belonged to the SCCmec IV. It should be noted that all patients had the underlying disease, and six patients had already passed away. The increasing linezolid resistance in bacterial strains becomes a real threat to patients, and monitoring such infections, in conjunction with surveillance and infection prevention programs, is very critical for reducing the number of linezolid-resistant Staphylococcal strains. A preprint of this study was published at https://europepmc.org/article/ppr/ppr417742.

Prevalence, characterization, and implications of methicillin-resistant Staphylococcus aureus (MRSA) in ready-to-eat foods from Delta, Nigeria: a concern for consumer safety

Abstract Ready-to-eat (RTE) foods are susceptible to contamination with methicillin-resistant Staphylococcus aureus (MRSA), presenting significant health risks to consumers. This study aimed to isolate, identify, and characterize MRSA from RTE foods in Delta, Nigeria, and assess their implications for consumer safety. Four hundred RTE food samples were collected from food outlets, and MRSA presence was determined using oxacillin resistance screening agar supplemented with polymyxin B and oxacillin. Polymerase chain reaction confirmed and characterized MRSA isolates for virulence potentials and antimicrobial resistance genes. Out of the 400 samples, 57(14.25%) tested positive for MRSA. The prevalence of virulence genes varied, with Panton-Valentine Leukocidin (pvl) detected in 40.51% of isolates, along with the detection of several staphylococcal enterotoxin genes. Antimicrobial resistance genes, including tetracycline (tetM, 43.04%), erythromycin (ermC, 32.91%), and methicillin (mecA, 100%; mecC, 29.11%) were detected. Staphylococcal cassette chromosome mec (SCCmec) typing revealed diverse profiles, with type V being predominant (32.9%). MRSA isolates exhibited resistance to multiple antibiotics, with 83.54% of them classified as multidrug-resistant. Extracellular virulence factors were common, with strong biofilm producers observed in 69.62% of isolates. These findings underscore the complexity of MRSA contamination in RTE foods, highlighting the need for enhanced surveillance and control measures to safeguard public health.

Prevalence and genetic characteristics ofStaphylococcus aureus isolates from cellphones of medical students from Iran.

Although mobile phones as a rapid communication vehicle can lead to improved quality of healthcare, they can also facilitate the transmission of pathogens to patients. This current research focuses on genetic diversity, and genes involved in resistance and biofilm production of Staphylococcus aureus isolates from mobile phones of medical students. Antibiotic resistance profiling and polymerase chain reaction (PCR) amplification of antibiotic resistance and biofilm-related genes were investigated and statistically analyzed. Staphylococcal cassette chromosome mec (SCCmec) types were analyzed by multiplex PCR, and S. aureus protein A gene typing (spa typing) was done using PCR and sequencing. Sixty-four S. aureus isolates (16.8%) were obtained from 380 medical students' mobile phones who were working in hospitals. The findings showed that 71.9% of the isolates were MRSA and 78.1% were classified as MDR. All isolates exhibited sensitivity to vancomycin and linezolid. Overall, 7.8% of the isolates displayed an inducible clindamycin resistance phenotype, while 26.7% showed resistance to mupirocin. The results indicated that 68.8% of the isolates were biofilm producers, with 7 isolates (15.9%) classified as strong producers, 22 isolates (50%) as moderate producers, and 15 isolates (34.1%) as weak producers. The most prevalent type was CC8-MRSA III/t030 (18.7%), followed by CC8-MRSA III/t037 (12.5%), CC/ST22-MSSA/t790 (10.9%), CC1-MRSA IV-t114 (9.4%), CC1-MRSA IV-t127 (7.8%), CC8-MRSA V/t064 (7.8%), CC/ST15-MSSA-t360 (7.8%), CC30-MSSA/t021(6.3%), MRSA V-t355 (6.3%), CC8-MRSA III/t421 (4.7%), CC1-MRSA V-t267 (4.7%), and CC/ST15-MSSA-t084 (3.1%). The genetic diversity and prevalent multidrug resistance indicate that the resistance situation of S. aureus recovered from mobile phones in Tehran is severe, posing a potential threat to patients, the community, and healthcare settings.

Identification of the novel fosfomycin resistance gene fosSC in Staphylococcus capitis

ObjectivesFosfomycin has regained attention for treating infections caused by methicillin-resistant Staphylococcus aureus and multidrug-resistant coagulase-negative staphylococci. In this research, our objective was to investigate the mechanisms underlying fosfomycin resistance in Staphylococcus capitis. MethodsThe minimum inhibitory concentrations (MICs) of fosfomycin were assessed in 109 clinical S. capitis isolates by the agar dilution method. By cloning the fos-like genes into the shuttle vector, pTSSCm-Pcap, and observing the change in fosfomycin MICs, the gene function was verified. Core genome multilocus sequence typing and comparative genomics analysis were conducted to determine the population characteristics of S. capitis isolates and analyse the genetic environment of the fos-like genes. ResultsWe identified a novel fosfomycin resistance gene, fosSC, on the chromosome in 58 out of 109 (53.2%) S. capitis isolates. The deduced products of the fosSC genes shared 67.15–67.88% amino acid sequence identity with FosB. The RN-pT-fosSC transformants carrying fosSC showed a 512-fold increase in the fosfomycin MICs. The fosSC gene was embedded in a conserved genetic context, but IS431mec was located to the left of the fosSC gene in cluster L due to the insertion of staphylococcal cassette chromosome mec. ConclusionsThe chromosomal fosSC genes in some lineages of S. capitis explained their high-level fosfomycin resistance. Ongoing surveillance is crucial for monitoring the potential threat of horizontal transfer, which could be facilitated by the presence of mobile genetic elements surrounding the fosSC gene.

High prevalence of ST5-SCCmec II-t311 clone of methicillin-resistant Staphylococcus aureus isolated from bloodstream infections in East China

ObjectivesMethicillin-resistant Staphylococcus aureus (MRSA) is a challenging global health threat, resulting in significant morbidity and mortality worldwide. This study aims to determine the molecular characteristics and antimicrobial susceptibility of 263 MRSA isolates in Zhejiang Province, east China.MethodsFrom 2014 to 2019, a total of 263 MRSA isolates from bloodstream infections (BSIs) were collected from 6 hospitals in 4 cities in Zhejiang province, east China. Antimicrobial susceptibility tests were conducted according to the guidelines set forth by the Clinical and Laboratory Standards Institute (CLSI). To characterize and analyze these isolates, multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec) typing, staphylococcal protein A (spa) typing and virulence genes gene profiles were performed.ResultsThe most predominant clone was ST5-SCCmec II-t311, which accounted for 41.8% (110/263), followed by ST59 (44/263, 16.7%). Compared with non-ST5-II-t311 isolates, ST5-II-t311 isolates were more resistant to erythromycin, tetracycline, levofloxacin, moxifloxacin, and ciprofloxacin, but more susceptible to clindamycin. Moreover, the rates of multidrug resistance were higher in ST5-II-t311 isolates compared to the non-ST5-II-t311 isolates. In comparison to the non-ST5-II-t311 isolates, ST5-II-t311 isolates showed no significant difference in virulence genes detected.ConclusionsMRSA ST5-II-t311 clone has become the most predominant clone in Zhejiang Province, east China and has higher rates of multidrug resistance than other isolates, that should be kept in mind when treating BSI. Moreover, MRSA ST59 clone shows an upward trend and has begun to spread into hospitals. Our findings highlight the importance of epidemiological studies of S. aureus carriage in the eastern region.

Detection of mecA Genes in Hospital-Acquired MRSA and SOSA Strains Associated with Biofilm Formation.

Methicillin-resistant (MR) Staphylococcus aureus (SA) and others, except for Staphylococcus aureus (SOSA), are common in healthcare-associated infections. SOSA encompass largely coagulase-negative staphylococci, including coagulase-positive staphylococcal species. Biofilm formation is encoded by the icaADBC operon and is involved in virulence. mecA encodes an additional penicillin-binding protein (PBP), PBP2a, that avoids the arrival of β-lactams at the target, found in the staphylococcal cassette chromosome mec (SCCmec). This work aims to detect mecA, the bap gene, the icaADBC operon, and types of SCCmec associated to biofilm in MRSA and SOSA strains. A total of 46% (37/80) of the strains were S. aureus, 44% (35/80) S. epidermidis, 5% (4/80) S. haemolyticus, 2.5% (2/80) S. hominis, 1.25% (1/80) S. intermedius, and 1.25% (1/80) S. saprophyticus. A total of 85% were MR, of which 95.5% showed mecA and 86.7% β-lactamase producers; thus, Staphylococcus may have more than one resistance mechanism. Healthcare-associated infection strains codified type I-III genes of SCCmec; types IV and V were associated to community-acquired strains (CA). Type II prevailed in MRSA mecA strains and type II and III in MRSOSA (methicillin-resistant staphylococci other than Staphylococcus aureus). The operon icaADBC was found in 24% of SA and 14% of SOSA; probably the arrangement of the operon, fork formation, and mutations influenced the variation. Methicillin resistance was mainly mediated by the mecA gene; however, there may be other mechanisms that also participate, since biofilm production is related to genes of the icaADBC operon and methicillin resistance was not associated with biofilm production. Therefore, it is necessary to strengthen surveillance to prevent the spread of these outbreaks both in the nosocomial environment and in the community.

The molecular epidemiology and clinical implication of methicillin-resistant Staphylococcus aureus (MRSA) sequence types in pediatric bacteremia: a restrospective observational study, 2016-2021.

While there is a high burden of methicillin-resistant Staphylococcus aureus (MRSA) infections among pediatric patients, studies on the molecular epidemiology of MRSA infections in Korean children since the 2010s are lacking. This study aimed to investigate the molecular genotypes and clinical characteristics of MRSA isolates from children with MRSA bacteremia at Asan Medical Center Children's Hospital from 2016 to 2021. Clinical data were retrospectively reviewed, and the molecular types of MRSA were determined using multilocus sequence typing (MLST) and Staphylococcal cassette chromosome mec (SCCmec) typing. The overall methicillin resistance rate of S. aureus bacteremia was 44.8% (77/172); 49.5% in the period 2016-2018 (period 1) and 37.3% in the period 2019-2021 (period 2) (P = 0.116). Community-acquired infections accounted for only 3.9% of cases. The predominant ST group was ST72 group (67.6%), followed by ST5 group (18.9%) and ST1 group (5.4%). The proportion of ST5 was significantly lower in period 2 compared to period 1 (P = 0.02). Compared to the ST5 and ST1 groups, the ST72 group exhibited lower overall antibiotic resistance and multidrug-resistant (MDR) rates (12.0% [6/50] in ST72 group vs. 100.0% [14/14] in ST5 group vs. 50.0% [2/4] in ST1 group; P < 0.001). In the multivariate analysis, the ST1 group was an independent risk factor for 30-day all-cause mortality (aOR, 44.12; 95% CI, 3.46-562.19). The ST72-MRSA strain remained the most frequently isolated genotype in Korean children, while the ST1 group emerged as an independent risk factor for 30-day all-cause mortality in pediatric MRSA bacteremia. Ongoing efforts to uncover the evolving epidemiology of MRSA are essential for developing effective strategies for prevention and treatment.

SCCmec transformation requires living donor cells in mixed biofilms

Methicillin-resistant Staphylococcus aureus (MRSA) is an important human pathogen that has emerged through the horizontal acquisition of the staphylococcal cassette chromosome mec (SCCmec). Previously, we showed that SCCmec from heat-killed donors can be transferred via natural transformation in biofilms at frequencies of 10−8-10−7. Here, we show an improved transformation assay of SCCmec with frequencies up to 10−2 using co-cultured biofilms with living donor cells. The Ccr-attB system played an important role in SCCmec transfer, and the deletion of ccrAB recombinase genes reduced the frequency ∼30-fold. SCCmec could be transferred from either MRSA or methicillin-resistant coagulase-negative staphylococci to some methicillin-sensitive S. aureus recipients. In addition, the transformation of other plasmid or chromosomal genes is enhanced by using living donor cells. This study emphasizes the role of natural transformation as an evolutionary ability of S. aureus and in MRSA emergence.

Optical Mapping: Detecting Genomic Resistance Cassettes in MRSA.

Methicillin-resistant Staphylococcus aureus (MRSA) is a multidrug-resistant bacterium with a global presence in healthcare facilities as well as community settings. The resistance of MRSA to beta-lactam antibiotics can be attributed to a mobile genetic element called the staphylococcal cassette chromosome mec (SCCmec), ranging from 23 to 68 kilobase pairs in length. The mec gene complex contained in SCCmec allows MRSA to survive in the presence of penicillin and other beta-lactam antibiotics. We demonstrate that optical mapping (OM) is able to identify the bacterium as S. aureus, followed by an investigation of the presence of kilobase pair range SCCmec elements by examining the associated OM-generated barcode patterns. By employing OM as an alternative to traditional DNA sequencing, we showcase its potential for the detection of complex genetic elements such as SCCmec in MRSA. This approach holds promise for enhancing our understanding of antibiotic resistance mechanisms and facilitating the development of targeted interventions against MRSA infections.

Occurrence and Characteristics of Toxigenic Staphylococcus aureus in Retail Foods in Iran.

Staphylococcus aureus causes various toxigenic and invasive diseases in humans worldwide. This study examined the prevalence, virulence genes, and antibiotic resistance of S. aureus isolates collected from 894 retail food samples in Ardabil, Iran. Staphylococcal cassette chromosome mec (SCCmec), spa, and multilocus sequence typing methods were employed to further investigate the molecular characteristics of methicillin-resistant S. aureus (MRSA) isolates. The results revealed that 11.18% (n = 100) of food samples exhibited contamination with S. aureus (10.50% methicillin-sensitive S. aureus [MSSA] and 0.67% MRSA). Notably, raw minced meat (29.41%), Faloodeh (25%), and Olivier salad (21.42%) emerged as the most frequently contaminated food items. Among the 100 isolates of S. aureus, 94% were characterized as MSSA, with the remaining 6% identified as MRSA. The highest resistance was observed for penicillin (12%). MRSA isolates exhibited significantly higher resistance rates. Seventy-nine percent of the isolates were positive for sea, 14% for seb, 8% for a sec, and 0% for sed enterotoxin-encoding genes. Sixteen percent of isolates harbored two or more staphylococcal enterotoxin genes, simultaneously. Moreover, 97%, 94%, 24%, and 22% of isolates were positive for hla, hld, tst, and pvl virulence-encoding genes, respectively. No isolate was positive for the exfoliative toxins encoding eta and etb genes. MRSA isolates belonged to CC8 (n = 4) and CC22 (n = 2). Isolates in CC8 belonged to lineage ST239-MRSA-III and spa type t030; the isolates in CC22 belonged to ST22-MRSA-IV and spa types t310 and t223. In conclusion, a relatively high proportion of our retail food samples were contaminated with S. aureus. The high incidence of isolates with toxigenic genes raises serious health concerns. Furthermore, the presence of MRSA lineages linked to humans suggests that retail foods may be contaminated with human origin.

Atopic dermatitis pediatric patients show high rates of nasal and intestinal colonization by methicillin-resistant Staphylococcus aureus and coagulase-negative staphylococci

BackgroundAtopic dermatitis (AD) patients have high rates of colonization by Staphylococcus aureus, which has been associated with worsening of the disease. This study characterized Staphylococcus spp isolates recovered from nares and feces of pediatric patients with AD in relation to antimicrobial susceptibility, staphylococcal cassette chromosome mec (SCCmec) type, presence of pvl genes and clonality. Besides, gut bacterial community profiles were compared with those of children without AD.ResultsAll 55 AD patients evaluated had colonization by Staphylococcus spp. Fifty-three (96.4%) patients had colonization in both clinical sites, whereas one patient each was not colonize in the nares or gut. Staphylococcus aureus was identified in the nostrils and feces of 45 (81.8%) and 39 (70.9%) patients, respectively. Methicillin-resistant Staphylococcus spp. isolates were found in 70.9% of the patients, and 24 (43.6%) had methicillin-resistant S. aureus (MRSA). S. aureus (55.6%) and S. epidermidis (26.5%) were the major species found. The prevalent lineages of S. aureus were USA800/SCCmecIV (47.6%) and USA1100/SCCmecIV (21.4%), and 61.9% of the evaluated patients had the same genotype in both sites. Additionally, gut bacterial profile of AD patients exhibits greater dissimilarity from the control group than it does among varying severities of AD.ConclusionsHigh rates of nasal and intestinal colonization by S. aureus and methicillin-resistant staphylococci isolates were found in AD patients. Besides, gut bacterial profiles of AD patients were distinctly different from those of the control group, emphasizing the importance of monitoring S. aureus colonization and gut microbiome composition in AD patients.

Methicillin Resistance Elements in the Canine Pathogen Staphylococcus pseudintermedius and Their Association with the Peptide Toxin PSM-mec.

Staphylococcus pseudintermedius is a frequent cause of infections in dogs. Infectious isolates of this coagulase-positive staphylococcal species are often methicillin- and multidrug-resistant, which complicates therapy. In staphylococci, methicillin resistance is encoded by determinants found on mobile genetic elements called Staphylococcal Chromosome Cassette mec (SCCmec), which, in addition to methicillin resistance factors, sometimes encode additional genes, such as further resistance factors and, rarely, virulence determinants. In this study, we analyzed SCCmec in a collection of infectious methicillin-resistant S. pseudintermedius (MRSP) isolates from predominant lineages in the United States. We found that several lineages characteristically have specific types of SCCmec elements and Agr types and harbor additional factors in their SCCmec elements that may promote virulence or affect DNA uptake. All isolates had SCCmec-encoded restriction-modification (R-M) systems of types I or II, and sequence types (STs) ST84 and ST64 had one type II and one type I R-M system, although the latter lacked a complete methylation enzyme gene. ST68 isolates also had an SCCmec-encoded CRISPR system. ST71 isolates had a psm-mec gene, which, in all but apparently Agr-dysfunctional isolates, produced a PSM-mec peptide toxin, albeit at relatively small amounts. This study gives detailed insight into the composition of SCCmec elements in infectious isolates of S. pseudintermedius and lays the genetic foundation for further efforts directed at elucidating the contribution of identified accessory SCCmec factors in impacting SCCmec-encoded and thus methicillin resistance-associated virulence and resistance to DNA uptake in this leading canine pathogen.

Enhanced Biofilm Formation by Tetracycline in a Staphylococcus aureus Naturally Lacking ica Operon and atl.

Staphylococcus aureus is a major, widespread pathogen, and its biofilm-forming characteristics make it even more difficult to eliminate by biocides. Tetracycline (TCY) is a major broad-spectrum antibiotic, the residues of which can cause deleterious health impacts, and subinhibitory concentrations of TCY have the potential to increase biofilm formation in S. aureus. In this study, we showed how the biofilm formation of S. aureus 123786 is enhanced in the presence of TCY at specific subinhibitory concentrations. S. aureus 123786 used in this study was identified as Staphylococcal Cassette Chromosome mec III, sequence type239 and naturally lacking ica operon and atl gene. Two assays were performed to quantify the formation of S. aureus biofilm. In the crystal violet (CV) assay, the absorbance values of biofilm stained with CV at optical density (OD)540 nm increased after 8 and 16 hr of incubation when the concentration of TCY was 1/2 minimum inhibitory concentration (MIC), whereas at the concentration of 1/16 MIC, the absorbance values increased after 16 and 24 hr of incubation. In tetrazolium salt reduction assay, the absorbance value at OD490 nm of S. aureus 123786 biofilms mixed with 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium solution increased after 8 hr when the concentration of TCY was 1/4 MIC, which may be correlated with the higher proliferation and maturation of biofilm. In conclusion, the biofilm formation of S. aureus 123786 could be enhanced in the presence of TCY at specific subinhibitory concentrations.

Epidemiological characterization of clinical isolates of meticillin resistant Staphylococcus aureus through multilocus sequence typing and staphylococcal cassette chromosome mec typing in Northwest Iran.

Methicillin-resistant Staphylococcus aureus (MRSA), is considered a potential and aggressive nosocomial pathogen. It accounts for 50% of S. aureus isolates in tertiary hospitals in Iran, however, there is no sufficient evolutionary and epidemiological investigation about this medically important bacterium. We aimed to study the lineage and evolution of MRSA in Northwest Iran during 2021-2022 based on the obtained phenotypic and genotypic characteristics. Seventy-two non-duplicate MRSA isolates were collected from 3 referral hospitals in Tabriz, Ardebil, and Urmia cities. The antimicrobial susceptibility patterns were determined by disk diffusion test and micro broth dilution methods. Thereafter 4 virulence genes (eta, etb, pvl, tst) and 5 types of staphylococcal cassette chromosome mec (SCCmec) were detected by PCR. In the final step, representative isolates were selected to be studied by Multilocus sequence typing (MLST). The highest resistance was observed to erythromycin and clindamycin at a rate of 76.4%, followed by ciprofloxacin (61.1%), gentamicin (54.2%), rifampin (38.9%), and co-trimoxazole (27.8%). All isolates were susceptible to vancomycin. The virulence genes of etb, pvl, tst, and eta were detected in 50%, 29.2%, 21.8%, and 13.9% of isolates, respectively. SCCmec types III and I were the most prevalent types, followed by types IV, II, and V. MLST analysis revealed 6 sequence types: ST6854, ST5282, ST127, ST7804, ST1607, and ST7784. Two MLST-based clonal complexes (CC8, and CC97) were identified as well. The ST numbers were non-repetitive. CC8 as a pandemic clone and an individual lineage and clinically significant clade was reported as the most prevalent clonal complex. It is essential periodic evaluations of antibiotic susceptibility patterns and study the evolutionary characteristics of medical-challenging microorganisms in particular MRSA to effectively treat and restrict the outbreaks.

Puerperal mastitis caused by limited community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) clones.

To outline the epidemiology of puerperal mastitis caused by methicillin-resistant Staphylococcus aureus (MRSA) and evaluate the effect of an infection control bundle on its incidence. A surge in MRSA puerperal mastitis was noted in a community hospital in September 2009. MRSA samples from mastitis cases and the environment underwent typing using multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec), gene encoding surface protein A (spa), accessory gene regulator (agr), and pulsed-field gel electrophoresis (PFGE). The phenotypic characteristics, including superantigen toxin profiles, gene encoding Panton-Valentine leucocidin (pvl), and minimal inhibitory concentration (MIC) against vancomycin, were ascertained. Subsequently, an infection control bundle emphasizing contact precautions was introduced, and mastitis incidence rates pre- and post-intervention were compared. The majority of cases occurred within 6 weeks post-delivery in first-time mothers. Of the 42 S. aureus isolates (27 from mastitis and 15 from colonized staff and environmental sources), 25 (92.6%) clinical and 3 (20%) colonized MRSA were identified as ST59-SCCmecVT-spa t437-agr group I with a vancomycin MIC of 1 mg/L, pvl-positive, and predominantly with a consistent toxin profile (seb-selk-selr). PFGE revealed 13 patterns; pulsotype B exhibited clonal relatedness between two clinical and three colonized MRSA samples. Post-intervention, the incidence of both mastitis and MRSA mastitis notably decreased from 13.01 to 1.78 and from 3.70 to 0.99 episodes per 100 deliveries, respectively. Distinct community-associated MRSA (CA-MRSA) clones were detected among puerperal mastitis patients and colonized staff. The outbreak was effectively controlled following the implementation of a targeted infection control bundle.

Genetic characterization of methicillin-resistant / susceptible Staphylococcus aureus (MRSA/MSSA) and Staphylococcus argenteus clinical isolates in Bangladesh: Dominance of ST6-MRSA-IV/t304 and detection of cfr/fexA in ST8-MSSA/t008

ObjectivesCoagulase-positive staphylococcus (CoPS), represented by Staphylococcus aureus, is a major cause of infections in humans. This study aimed to investigate molecular epidemiological characteristics, antimicrobial resistance, and their trends of CoPS in Bangladesh. MethodsClinical isolates of CoPS were collected from two medical institutions in Bangladesh for a 2-year period and analyzed for their species, genotypes, virulence factors, antimicrobial susceptibility, and resistance determinants. Results172 CoPS isolates collected were identified as S. aureus or S. argenteus (170 and two, respectively). Methicillin-resistant S. aureus (MRSA) accounted for 36% (n = 61), having Staphylococcal cassette chromosome mec (SCCmec)-IV (82%) or V (18%). Panton-Valentine leukocidin (PVL) genes were detected at higher rate in methicillin-susceptible S. aureus (MSSA) (62%) than MRSA (26%). MRSA comprised 11 STs, including a dominant type ST6 (46%) associated with mostly SCCmec-IVa/spa-t304, and one isolate had genetic features of the USA300 clone (ST8/SCCmec-IVa/coa-IIIa/spa-t008/ACME-I/ΦSa2USA). STs of CC1, CC88, and CC398 were common in MSSA, with CC88 showing the highest PVL-positive rate. One MSSA isolate (ST8/spa-t008) harbored fexA and cfr showing susceptibility to linezolid. S. argenteus was methicillin-susceptible and belonged to ST2250/coa-XId. ConclusionsGenetic characteristics of current MRSA/MSSA in Bangladesh were revealed, with first identification of S. argenteus at low prevalence.

Whole-Genome Investigation of Zoonotic Transmission of Livestock-Associated Methicillin-Resistant Staphylococcus aureus Clonal Complex 398 Isolated from Pigs and Humans in Thailand.

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) has been widespread globally in pigs and humans for decades. Nasal colonization of LA-MRSA is regarded as an occupational hazard to people who are regularly involved in livestock production. Our previous study suggested pig-to-human transmission caused by LA-MRSA clonal complex (CC) 398, using traditional molecular typing methods. Instead, this study aimed to investigate the zoonotic transmission of LA-MRSA CC398 using whole genome sequencing (WGS) technologies. A total of 63 LA-MRSA isolates were identified and characterized in Thailand. Further, the 16 representatives of LA-MRSA CC9 and CC398, including porcine and worker isolates, were subjected to WGS on the Illumina Miseq platform. Core-genome single nucleotide polymorphism (SNP)-based analyses verify the zoonotic transmission caused by LA-MRSA CC398 in two farms. WGS-based characterization suggests the emergence of a novel staphylococcal cassette chromosome (SCC) mec type, consisting of multiple cassette chromosome recombinase (ccr) gene complexes via genetic recombination. Additionally, the WGS analyses revealed putative multi-resistant plasmids and several cross-resistance genes, conferring resistance against drugs of last resort used in humans such as quinupristin/dalfopristin and linezolid. Significantly, LA-MRSA isolates, in this study, harbored multiple virulence genes that may become a serious threat to an immunosuppressive population, particularly for persons who are in close contact with LA-MRSA carriers.

Methicillin-resistant staphylococci in clinical bovine mastitis: occurrence, molecular analysis, and biofilm production.

Staphylococcus aureus is an important pathogen that causes mastitis in cattle, and the emergence of methicillin-resistant S. aureus (MRSA) poses a threat to veterinary and human medicine. The aims of the study were to investigate the prevalence of MRSA and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) isolated from clinical mastitis, their ability to form biofilms, and the antimicrobial susceptibility of S. aureus strains. In addition, the Staphylococcal Cassette Chromosome mec (SCCmec) type, spa type and the presence of Panton-Valentine Leucocidin in MRSA were evaluated. A total of 326 staphylococcal strains were screened by multiplex-PCR for S. aureus and Staphylococcus intermedius group (SIG) identification. The S. aureus strains (n = 163) were subjected to phenotypic testing for antimicrobial susceptibility and biofilm formation. Molecular analysis was performed on MRSA mecA-positive strains. Of 163 S. aureus isolates, 142 strains (87.1%) were resistant to at least one antibiotic, and all 19 MRSA strains were resistant to at least four out of five antibiotics tested. All S. aureus strains harboured the icaA gene and were biofilm producers. Nineteen MR-CoNS strains were also isolated. The most prevalent spa types among MRSA were t001 (57.9%) and t037 (31.6%), while one MRSA was type t008 and one was type t041. Most MRSA were SCCmec type I (63.2%) and III (31.6%) and only one strain was type IV. None of the MRSA isolates had the PVL gene. The prevalence of multidrug-resistant S. aureus in bovine mastitis is a serious concern. The finding of MRSA with spa types predominant in humans and infrequent in Italian cows and with SCCmec infrequently found in bovine milk or cheese suggest a human origin of these strains. The ability of MRSA and MR-CoNS involved in bovine mastitis to be transferred to humans and vice versa poses a public health concern.

Molecular and Clinical Features of Heterogeneous Vancomycin-Intermediate Staphylococcus aureus in Tertiary Care Hospitals in South India

Objectives: This study aimed to detect heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) among methicillin-resistant S. aureus (MRSA) isolated from healthcare-associated infections and identify staphylococcal cassette chromosome mec (SCCmec) types. Methods: This study was conducted from February 2019 to March 2020 and included patients admitted in 4 tertiary care hospitals in Karnataka, India. Isolation and identification of MRSA were done using standard bacteriological methods. Antimicrobial susceptibility testing was done using Kirby–Bauer disc diffusion; macrolide-lincosamide-streptogramin B phenotypes were identified using the D test. The minimum inhibitory concentration (MIC) of vancomycin was determined using agar dilution. hVISA were confirmed by the modified population analysis profile-area under the curve test. SCCmec types and the Panton- Valentine leukocidin (pvl) gene were detected using multiplex polymerase chain reaction. Results: Of 220 MRSA stains, 14 (6.4%) were hVISA. None of the MRSA isolates was vancomycin-intermediate or -resistant and all hVISA were susceptible to linezolid and teicoplanin. The macrolide-streptogramin B phenotype was present in 42.9% of hVISA; 92.9% of the hVISA strains had vancomycin MIC in the range of 1–2 μg/mL. Majority of the hVISA and vancomycin-susceptible MRSA were isolated from patients with skin and soft tissue infections. SCCmec III and IV were present in 50% and 35.7% of hVISA, respectively; 14.3% of the hVISA harboured SCCmec V. Conclusion: The prevalence rate of hVISA among MRSA was 6.4%. Therefore, MRSA strains should be tested for hVISA before starting vancomycin treatment. None of the isolates was vancomycin-intermediate or -resistant and all the hVISA strains were susceptible to linezolid and teicoplanin. The majority of the hVISA were isolated from patients with skin and soft tissue infections and harboured SCCmec III and IV. Keywords: MRSA; Hospital Infection; Molecular Typing; Vancomycin; India.

2177. Characterization of community-acquired methicillin-resistant Staphylococcus aureus isolated from patients with skin and soft tissue infections in selected health facilities, in Kenya

Abstract Background Colonization of the skin, mucus membrane, and nose of humans by Staphylococcus aureus (S. aureus) is more common than infection. The lack of proper microbiological surveillance systems in Africa may underestimate the burden of Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA), while little is known about its incidence. In Kenya, there is a paucity of data on prevalence and circulating CA-MRSA strains. Methods Cross-sectional study design was employed with a sample size of 228 wound swabs from community-acquired skin and soft tissue infections, collected from 5 AMR surveillance sites in Kenya. S. aureus isolation, identification, and antimicrobial susceptibility tests were carried out according to standard bacteriology methods. Molecular characterization for MRSA isolates was performed by whole genome sequencing. Results Descriptive and inferential statistics were computed using the R program. Total S. aureus isolated was 29.38 % while MRSA isolation varied within study sites, with a CA-MRSA prevalence of 1.8 %. Phenotypic resistance observed did not match genotypic resistance for some isolates. Resistance mostly reported in nosocomial infections and resistance to reserved antibiotics was observed, which raises concern. Mutations within resistance genes, Inducible-Macrolide-Lincosamide-Streptogramin b resistance (MLSBi), 23S ribosome resistance and also erythromycin resistance by efflux pump was observed. Staphylococcal chromosomal cassette mec (SCCmec) type IV was the most prevalent while the sequence types (STs) obtained were ST 30, 8 and the novel STs 7460 and 7635. Only one isolate had intact mecA and its regulatory genes, but still conferred methicillin resistance. IS 1272 was detected in mecA regulatory genes. Conclusion The resistance patterns observed in this study further highlight the burden of antimicrobial resistance in community isolates of S. aureus. There is need for more research on CA-MRSA within Antimicrobial resistance (AMR) surveillance in Kenya in order to better understand the molecular epidemiology as well as the drivers of resistance Disclosures All Authors: No reported disclosures