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Methicillin-Resistant Staphylococcus aureus (MRSA) is a significant threat to human health. Additionally, biofilm forming bacteria becomes more tolerant to antibiotics and act as bacterial reservoir leading to chronic infection. In this study, we characterised the antibiotic susceptibility, biofilm production and sequence types (ST) of 74 randomly selected clinical isolates of S. aureus causing ocular infections. Antibiotic susceptibility revealed 74% of the isolates as resistant against one or two antibiotics, followed by 16% multidrug-resistant isolates (MDR), and 10% sensitive. The isolates were characterized as MRSA (n = 15), Methicillin-sensitive S. aureus (MSSA, n = 48) and oxacillin susceptible mecA positive S. aureus (OS-MRSA, n = 11) based on oxacillin susceptibility, mecA gene PCR and PBP2a agglutination test. All OS-MRSA would have been misclassified as MSSA on the basis of susceptibility test. Therefore, both phenotypic and genotypic tests should be included to prevent strain misrepresentation. In addition, in-depth studies for understanding the emerging OS-MRSA phenotype is required. The role of fem XAB gene family has been earlier reported in OS-MRSA phenotype. Sequence analysis of the fem XAB genes revealed mutations in fem  × (K3R, H11N, N18H and I51V) and fem B (L410F) genes. The fem XAB genes were also found down-regulated in OS-MRSA isolates in comparison to MRSA. In OS-MRSA isolates, biofilm formation is regulated by fibronectin binding proteins A & B. Molecular typing of the isolates revealed genetic diversity. All the isolates produced biofilm, however, MRSA isolates with strong biofilm phenotype represent a worrisome situation and may even result in treatment failure.

Staphylococcus aureus or methicillin-resistant Staphylococcus aureus (MRSA) is an important issue associated with significant morbidity and mortality and well known as a predominant pathogen causing bloodstream infection (BSIs) globally. To estimate the antibiotic resistance and molecular characteristics of S. aureus causing BSIs in Shanghai, 120  S. aureus isolates (20 isolates each year) from the patients with S. aureus BSIs from 2013 to 2018 were randomly selected and enrolled in this study. Fifty-three (44.2%) MRSA isolates were determined, and no isolate was found resistant to vancomycin, daptomycin, synercid, linezolid and ceftaroline. The toxin genes tst , sec , seg and sei were found more frequently among MRSA isolates compared with MSSA isolates (all P  < 0.0001). Twenty-nine sequence types (STs) were identified, and ST5 (23.3%) was the most common ST, followed by ST398 (11.7%) and ST764 (10.0%). SCC mec II (73.6%) was the most frequent SCC mec type among MRSA isolates. The dominant clonal complexes (CCs) were CC5 (ST5, ST764, ST965 and ST3066; 36.7%) and the livestock-associated clone CC398 (ST398, 11.7%). MRSA-CC5 was the predominant CC among MRSA isolates (37/53, 69.8%), and CC5-II MRSA was found in 34 isolates accounting for 91.9% (34/37) among CC5 MRSA isolates. In addition, all 29 tst -positive MRSA isolates were CC5-MRSA as well. Our study provided the properties and genotypes of S. aureus causing BSIs at Ruijin Hospital in Shanghai from 2013 to 2018, and might suggest of value clues for the further study insights into pathogenic mechanisms intrinsically referring to the development of human-adapted S. aureus clones and their diffusions.

Introduction Seafood contamination by bacteria is a pervasive issue, contributing to foodborne illnesses. This study investigates the prevalence, virulence factors, and antibiotic resistance in Staphylococcus aureus ( S. aureus ) isolated from various seafood products. Methods A total of 460 samples, including fresh, smoked, salted, and dried fish, as well as oysters, crab, lobster, and shrimp, were collected in Shahrekord, Iran. S. aureus isolation followed ISO standards, with confirmation via PCR for 16S rRNA and nuc genes. Antibiotic susceptibility was determined via Kirby-Bauer disc diffusion, while PCR detected enterotoxin and antibiotic resistance genes. Findings S. aureus was prevalent in all seafood types, with 27.83% positivity. Methicillin-resistant S. aureus (MRSA) was found in most samples, except oysters and crabs. Virulence genes were common, with Sea , Seb , Sed , Sec , and See being the most prevalent. High resistance to penicillin G and ampicillin (70%- 100%) was observed. Resistance varied for other antibiotics, with linezolid showing 100% susceptibility. The mecA gene was present in over 50% of isolates, with blaZ being the most detected resistance gene. Conclusion The study underscores the need for Good Hygiene Practices (GHP) in seafood processing to mitigate S. aureus transmission. While specific comparisons between sample types were limited, the findings emphasize the prevalence of virulence factors and antibiotic resistance in seafood-associated S. aureus, highlighting the importance of vigilant food safety measures.

Background Foot infections are a major cause of morbidity in people with diabetes and the most common cause of diabetes-related hospitalization and lower extremity amputation. Staphylococcus aureus is by far the most frequent species isolated from these infections. In particular, methicillin-resistant S. aureus (MRSA) has emerged as a major clinical and epidemiological problem in hospitals. MRSA strains have the ability to be resistant to most β-lactam antibiotics, but also to a wide range of other antimicrobials, making infections difficult to manage and very costly to treat. To date, there are two fifth-generation cephalosporins generally efficacious against MRSA, ceftaroline and ceftobripole, sharing a similar spectrum. Biofilm formation is one of the most important virulence traits of S. aureus. Biofilm growth plays an important role during infection by providing defence against several antagonistic mechanisms. In this study, we analysed the antimicrobial susceptibility patterns of biofilm-producing S. aureus strains isolated from diabetic foot infections. The antibiotic minimum inhibitory concentration (MIC) was determined for ten antimicrobial compounds, along with the minimum biofilm inhibitory concentration (MBIC) and minimum biofilm eradication concentration (MBEC), followed by PCR identification of genetic determinants of biofilm production and antimicrobial resistance. Results Results demonstrate that very high concentrations of the most used antibiotics in treating diabetic foot infections (DFI) are required to inhibit S. aureus biofilms in vitro, which may explain why monotherapy with these agents frequently fails to eradicate biofilm infections. In fact, biofilms were resistant to antibiotics at concentrations 10–1000 times greater than the ones required to kill free-living or planktonic cells. The only antibiotics able to inhibit biofilm eradication on 50 % of isolates were ceftaroline and gentamicin. Conclusions The results suggest that the antibiotic susceptibility patterns cannot be applied to biofilm established infections. Selection of antimicrobial therapy is a critical step in DFI and should aim at overcoming biofilm disease in order to optimize the outcomes of this complex pathology.

Staphylococcus aureus colonizes patients with atopic dermatitis (AD) and exacerbates disease by promoting inflammation. The present study investigated the safety and mechanisms of action of Staphylococcus hominis A9 ( Sh A9), a bacterium isolated from healthy human skin, as a topical therapy for AD. Sh A9 killed S. aureus on the skin of mice and inhibited expression of a toxin from S. aureus ( psm α) that promotes inflammation. A first-in-human, phase 1, double-blinded, randomized 1-week trial of topical Sh A9 or vehicle on the forearm skin of 54 adults with S. aureus -positive AD (NCT03151148) met its primary endpoint of safety, and participants receiving Sh A9 had fewer adverse events associated with AD. Eczema severity was not significantly different when evaluated in all participants treated with Sh A9 but a significant decrease in S. aureus and increased Sh A9 DNA were seen and met secondary endpoints. Some S. aureus strains on participants were not directly killed by Sh A9, but expression of mRNA for psm α was inhibited in all strains. Improvement in local eczema severity was suggested by post-hoc analysis of participants with S. aureus directly killed by Sh A9. These observations demonstrate the safety and potential benefits of bacteriotherapy for AD. First-in-human test of topical application of a commensal bacterium on skin of individuals with atopic dermatitis reduces colonization by proinflammatory Staphylococcus aureus .

Background The COVID-19 pandemic has dramatically impacted in patients from Intensive Care Units (ICUs), making them more vulnerable to infection/colonization by clinically relevant pathogens. However, little is known about the  Staphylococcus aureus  isolates that colonized these patients during the pandemic. Methods Consecutive  S. aureus  isolates from surveillance swabs of patients of two ICUs of a hospital in Rio de Janeiro, between September 2020 and September 2021, were evaluated for phenotypic antimicrobial resistance. Methicillin-resistant  S. aureus  (MRSA) isolates were evaluated for resistance and virulence genes, biofilm production, and their genotypic profiles. Medical records were accessed for clinical and demographic data. Results Among 255 patients colonized by  S. aureus , 79 (30.9%) were in the cICU (COVID-19 ICU) and 176 (69.1%) in the ncICU (non-COVID-19 ICU). COVID-19 patients made greater use of antimicrobials during hospitalization ( p <  0.05). Higher rates of resistance for erythromycin and clindamycin, as well as the inducible macrolide-lincosamide-streptogramin B resistance phenotype and multidrug resistance were found in cICU isolates ( p <  0.05). An overall rate of 36.5% of MRSA isolates was detected, with 41.7% in cICU and 34% in ncICU ( p  = 0.22). SCC mec  types II (22.6%) and IV (71%) were the most found, and the latter was more frequent in the ncICU ( p <  0.01). More than 50% of the isolates carried the resistance genes  erm (C),  msr (A),  mrs (B),  mph (C),  aph (3’)-III3a and  smr , and the virulence genes  ica A,  sas G,  ebp S,  scn , egc cluster,  fnbp B and  cna . The cICU presented isolates that primarily carried the  erm (C),  smr , and  cna  genes and that showed strong biofilm production ( p <  0.05). Clonal complex (CC) 5 was prevalent (65.6%) and associated with the hospital clones USA800/ST5-IV and USA100/ST105-II, which were most found in ncICU and cICU, respectively ( p <  0.05). Community MRSA comprised 31.2% of isolates and mainly included the USA300/ST8-IV lineage (18.3%), with all isolates carrying the  pvl  genes. Conclusions The significant impact on antimicrobial resistance rates and the emergence of virulent lineages among  S. aureus  isolates during the COVID-19 pandemic highlights the close relationship between this disease and antimicrobial resistance and the importance of constant microbiological surveillance to reduce the risks associated with future pandemics.

Objective The purpose of this study is a new update on the resistance profile, Macrolide–Lincosamide–Streptogramin B resistance mechanisms and biofilm formation in the Staphylococcus aureus isolated from health care workers (HCWs) nasal carriage at a children’s teaching hospital in Babol (Northern Iran). Results A total of 143 non-repetitive nasal swab samples were collected from volunteers, where 53.8% (n; 77/143) were HCWs, 33.6% (n; 48/143) medical students, and 12.6% (n; 18/143) resident students. The prevalence of nasal carriers of S. aureus was 22.4% (n; 32/143), among them, 40.6% (n; 13/32) were identified as methicillin-resistant Staphylococcus aureus (MRSA( carriers. Antimicrobial susceptibility testing showed that erythromycin (68.8%, n; 22/32) and ciprofloxacin (15.6%, n; 5/32) had the highest and lowest resistance rate, respectively. The frequency of resistance genes in the strains was as follows; ermC (n; 17/32, 53.1%), ermA (n; 11/32, 34.4%), ermB (n; 6/32, 18.7%), ereA (n; 3/32, 9.4%). Moreover, 50.0% (n; 16/32), 28.1% (n; 9/32) and 21.8% (n; 7/32) of isolates were strongly, weakly and moderately biofilm producer, respectively. Macrolides-lincosamides-streptogramins B (MLSB) antibiotic resistance among S. aureus isolates from HCWs nasal carriage have found significant prevalence rates throughout the globe. It is crucial to remember that the development of biofilms and MLS B antibiotic resistance are both dynamic processes.

Background COVID-19 is known as a new viral infection. Viral-bacterial co-infections are one of the biggest medical concerns, resulting in increased mortality rates. To date, few studies have investigated bacterial superinfections in COVID-19 patients. Hence, we designed the current study on COVID-19 patients admitted to ICUs. Methods Nineteen patients admitted to our ICUs were enrolled in this study. To detect COVID-19, reverse transcription real-time polymerase chain reaction was performed. Endotracheal aspirate samples were also collected and cultured on different media to support the growth of the bacteria. After incubation, formed colonies on the media were identified using Gram staining and other biochemical tests. Antimicrobial susceptibility testing was carried out based on the CLSI recommendations. Results Of nineteen COVID-19 patients, 11 (58%) patients were male and 8 (42%) were female, with a mean age of ~ 67 years old. The average ICU length of stay was ~ 15 days and at the end of the study, 18 cases (95%) expired and only was 1 case (5%) discharged. In total, all patients were found positive for bacterial infections, including seventeen Acinetobacter baumannii (90%) and two Staphylococcus aureus (10%) strains. There was no difference in the bacteria species detected in any of the sampling points. Seventeen of 17 strains of Acinetobacter baumannii were resistant to the evaluated antibiotics. No metallo-beta-lactamases -producing Acinetobacter baumannii strain was found. One of the Staphylococcus aureus isolates was detected as methicillin-resistant Staphylococcus aureus and isolated from the patient who died, while another Staphylococcus aureus strain was susceptible to tested drugs and identified as methicillin-sensitive Staphylococcus aureus . Conclusions Our findings emphasize the concern of superinfection in COVID-19 patients due to Acinetobacter baumannii and Staphylococcus aureus . Consequently, it is important to pay attention to bacterial co-infections in critical patients positive for COVID-19.

Objectives Diabetic foot ulcers (DFUs) often lead to hospital admissions, amputations and deaths; however, there is no up-to-date information on microbial isolates from DFUs and no mention of utilization of molecular techniques in Sub-Saharan Africa. We conducted a cross-sectional study among 83 adult patients at a tertiary hospital in Kenya over 12 months. The study aimed to isolate, identify bacteria, their antibiotic susceptibility patterns in active DFUs, and to compare standard microbiological methods versus a real-time PCR commercial kit in the detection of Staphylococcus aureus DNA and methicillin-resistant S. aureus (MRSA) DNA. Results Eighty swabs (94%) were culture-positive; 29% were Gram-positive and 65% were Gram-negative. The main organisms isolated were S. aureus (16%), Escherichia coli (15%), Proteus mirabilis (11%), Klebsiella pneumoniae (7%) and Pseudomonas aeruginosa (7%). The bacterial isolates showed resistance to commonly used antibiotics such as ampicillin, amoxicillin, cefepime, ceftazidime, cefuroxime, clindamycin, erythromycin, piperacillin–tazobactam, tetracycline and trimethoprim–sulphamethoxazole (TMPSMX). Thirty-one percent of the S. aureus isolated and 40% of the Gram-negatives were multi-drug resistant organisms (MDROs). There was a high prevalence of nosocomial bacteria. MRSA were not identified using culture methods but were identified using PCR. PCR was more sensitive but less specific than culture-based methods to identify S. aureus.

Background Staphylococcus aureus ( S. aureus ) associated with COVID-19 has not been well documented. This cross-sectional study evaluated the association between nasal S. aureus carriage and COVID-19. Methods and results Nasopharyngeal samples were collected from 391 participants presenting for COVID-19 test in Lagos, Nigeria, and S. aureus was isolated from the samples. Antimicrobial susceptibility test was done by disc diffusion method. All S. aureus isolates were screened for the presence of mecA , panton-valentine leucocidin (PVL) and toxic shock syndrome toxin (TSST) virulence genes by polymerase chain reaction. Staphylococcal protein A (spa) typing was conducted for all the isolates. Participants with COVID-19 had double the prevalence of S. aureus (42.86%) compared to those who tested negative (20.54%). A significant association was seen between S. aureus nasal carriage and COVID-19 ( p  = 0.004). Antimicrobial sensitivity results showed resistance to oxacillin (100%), cefoxitin (53%), and vancomycin (98.7%). However, only 41% of the isolates harbored the mecA gene, with SCCmecV being the most common SCCmec type. There was no association between the carriage of virulence genes and COVID-19. A total of 23 Spa types were detected, with t13249 and t095 being the two most common spa types. Conclusion This study examined the association between nasal S. aureus carriage and SARS-COV-2 infection. Further research is required to fully explore the implications of S. aureus co-infection with COVID-19.