Characterization of the clonal profile of methicillin resistant Staphylococcus aureus isolated from patients with early post-operative orthopedic implant based infections

Whole genome sequencing of methicillin-resistant Staphylococcus aureus clinical isolates from Terengganu, Malaysia, indicates the predominance of the EMRSA-15 (ST22-SCCmec IV) clone

Despite the importance of methicillin-resistant Staphylococcus aureus (MRSA) as a priority nosocomial pathogen, the genome sequences of Malaysian MRSA isolates are currently limited to a small pool of samples. Here, we present the genome sequence analyses of 88 clinical MRSA isolates obtained from the main tertiary hospital in Terengganu, Malaysia in 2016-2020, to obtain in-depth insights into their characteristics. The EMRSA-15 (ST22-SCCmec IV) clone of the clonal complex 22 (CC22) lineage was predominant with a total of 61 (69.3%) isolates. Earlier reports from other Malaysian hospitals indicated the predominance of the ST239 clone, but only two (2.3%) isolates were identified in this study. Two Indian-origin clones, the Bengal Bay clone ST772-SCCmec V (n = 2) and ST672 (n = 10) were also detected, with most of the ST672 isolates obtained in 2020 (n = 7). Two new STs were found, with one isolate each, and were designated ST7879 and ST7883. From the core genome phylogenetic tree, the HSNZ MRSA isolates could be grouped into seven clades. Antimicrobial phenotype-genotype concordance was high (> 95%), indicating the accuracy of WGS in predicting most resistances. Majority of the MRSA isolates were found to harbor more than 10 virulence genes, demonstrating their pathogenic nature.

Effectiveness of nursing intervention in the operating room to prevent wound infections in patients undergoing orthopaedic surgery: A meta-analysis

Surgical site wound infection is one of the most common postoperative complications in orthopaedic clinical practice. This study employed a meta-analysis approach to comprehensively evaluate the effect of operating room nursing interventions on the prevention of surgical site wound infections in orthopaedic surgical patients. A computer search was conducted using PubMed, EMBASE, Cochrane Library, China National Knowledge Infrastructure (CNKI), Chinese Biomedical Literature Database (CBM), VIP, and Wanfang databases from the inception of each database until May 2023 for randomised controlled trials (RCTs) that investigated the application of operating room nursing interventions in orthopaedic surgery. Two reviewers independently screened the literature, extracted data, and assessed study quality. The meta-analysis was conducted using Stata 17.0. A total of 29 studies involving 3567 patients were included, with 1784 patients in the intervention group, and 1783 patients in the control group. The results of the meta-analysis showed that compared with the control group, the use of operating room nursing interventions significantly reduced the incidence of surgical site wound infection after orthopaedic surgery (2.85% vs. 13.24%; odds ratio: 0.18, 95% confidence interval: 0.14-0.25; p < 0.001). Current evidence suggests that operating room nursing interventions reduce the incidence of surgical site wound infections. However, owing to the limited number and low quality of the studies, more high-quality, large-sample RCTs are needed to further verify these findings.

Effectiveness of nursing intervention in the operating room to prevent pressure ulcer and wound infection in patients undergoing intertrochanteric fracture: A meta-analysis

In this study, a meta-analysis was conducted to comprehensively assess the effectiveness of nursing intervention in the operating room to prevent pressure ulcers and wound infections in patients with intertrochanteric fractures. A computerised search of PubMed, Cochrane Library, Embase, China National Knowledge Infrastructure (CNKI), VIP Database of Chinese Technical Periodicals, and Wanfang databases was performed to identify randomised controlled studies (RCTs) on the effectiveness of nursing intervention in the operating room for patients undergoing intertrochanteric fractures from the time of construction of the respective databases to June 2023. Two researchers independently searched and screened the literature, extracted information and performed quality assessments of the included literature. The meta-analysis was performed using RevMan 5.4 software. Eighteen studies were finally included, including 1517 patients, with 757 in the intervention group and 760 in the control group. The results showed that nursing intervention in the operating room significantly reduced the incidence of postoperative pressure ulcers in patients with intertrochanteric femoral fractures compared to the control group (1.69% vs. 6.01%, odds ratio [OR]: 0.32, 95% confidence interval [CI]: 0.18-0.57, p < 0.001) and reduced the incidence of surgical site wound infection (1.00% vs. 6.15%, OR: 0.23, 95% CI: 0.11-0.50, p < 0.001). Current evidence suggests that nursing intervention in the operating room is superior to routine care in reducing the incidence of pressure ulcers and wound infections in patients with intertrochanteric fractures and that such interventions should be promoted for clinical use.

Clonal diversity of Staphylococcus aureus isolates in clinical specimens from selected health facilities in Ethiopia

Staphylococcus aureus is among the top three causative agents of nosocomial infection in Ethiopia. The majority of studies in Ethiopia have focused on the epidemiology of S. aureus in hospital settings, with limited molecular genotyping results. Molecular characterization of S. aureus is essential for identification of strains, and contributes to the control and prevention of S. aureus infection. The aim of the current study was to determine the molecular epidemiology of methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) isolates recovered from clinical specimens in Ethiopia. A total of 161 MSSA and 9 MRSA isolates were characterized using pulsed-field gel electrophoresis (PFGE) and staphylococcal protein A (spa) typing. Based on the PFGE analysis, MSSA isolates were grouped into eight pulso-types groups (from A to I), while MRSA isolates clustered into three (A, B and C) pulso-types with more than 80% similarity. The spa typing analysis showed diversity of S. aureus with 56 distinct spa types. Spa type t355 was most prevalent (56/170, 32.9%), while eleven new spa types were detected including t20038, t20039, and t20042. The identified spa types were clustered into 15 spa-clonal complexes (spa-CCs) using BURP analysis; novel/unknown spa types were further subjected to MLST analysis. The majority of isolates belonged to spa-CC 152 (62/170, 36.4%), followed by spa-CC 121 (19/170, 11.2%), and spa-CC 005 (18 /170, 10.6%). Of the nine MRSA isolates, 2 (22.2%) were spa-CC 239 with staphylococcal cassette chromosome (SCC)mec III. These findings highlight the diversity of S. aureus strains in Ethiopia, as well as the presence of potentially epidemic strains circulating in the country necessitating further characterization of S. aureus for antimicrobial resistance detection and infection prevention purposes.

Molecular Epidemiology and Characterization of Multidrug-Resistant MRSA ST398 and ST239 in Himachal Pradesh, India

Aim

Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of severe and difficult-to-treat infections in humans and animals. We aimed to identify the predominant lineages of methicillin-resistant S. aureus in Himachal Pradesh, India, to understand the genomic epidemiology along with the genotypic and phenotypic characteristics.

Methods

We isolated 250 S. aureus from two district hospitals in Himachal Pradesh, India. Methicillin-Resistant S. aureus (MRSA) isolates were subjected to MLST, SCCmec typing, and resistance as well as virulence determinants were determined by PCR and sequencing. Bio-typing was also performed for source tracking.

Results

A 17.6% (44/250) of isolates were classified as MRSA by both the MRSA detection kit and disc diffusion methods. Antimicrobial Susceptibility Testing of MRSA isolates (n = 44) showed high resistance to oxacillin (77.27%), erythromycin (77.27%), tetracycline (75%), cefoxitin (65.9%), and gentamicin (61.36%), while low resistance was observed for teicoplanin (36.36%), vancomycin and levofloxacin (31.81%) and fusidic acid (18.18%). All isolates were sensitive to linezolid, quinupristin-dulfopristin, dalbavancin, and cefazoline. The SCCmec-II was observed in 20.45% of isolates, SCCmec-I in 11.36%, SCCmec-III in 9%, SCCmec-IV in 40.9% and SCCmec-V in 18.18%. The mecA gene was present in all isolates (n = 44) and 50% also had the vanA gene. 35% of isolates had the lukS-PV/lukf-PV toxin gene and 11.36% had the co-existence of mecA, vanA, and lukS-PV/lukf-PV. The major strain was ST398 (39%) followed by ST239 (27%), ST217 (16%), ST121 (11%), and ST338 (7%). The MRSA isolates produced staphylokinase and β-hemolysis but were negative for bovine plasma coagulation tests.

In Conclusion

The predominant MRSA clones in Himachal Pradesh, India, were hospital-associated multi-drug resistant-MRSA ST239 with PVL and community-associated MRSA ST398.

Characterization of Methicillin-Resistant Staphylococcus aureus Isolates from Periprosthetic Joint Infections

Periprosthetic joint infection (PJI) is a troublesome clinical issue in total joint arthroplasty (TJA). Although methicillin-resistant Staphylococcus aureus (MRSA) is considered to be the most serious pathogen in PJIs, little is known about the genotypic and phenotypic characteristics of MRSA clones isolated from PJI patients. A total of 36 MRSA isolates from PJI patients were collected at the Chang-Gung Memorial Hospital in Taiwan from May 2016 to October 2019. All MRSA isolates were subjected to genome typing. The prevalence of Panton–Valentine leucocidin (PVL), the antibiotic susceptibility profile, and the biofilm formation ability were compared among different MRSA genogroups. Additionally, demographics and clinical manifestations of patients infected with different MRSA genogroups were investigated. Eight sequence types (STs) were identified among 36 isolated from PJIs. According to the incidence of MRSA genotypes in PJIs, in this study, we divided them into four groups, including ST8 (n = 10), ST59 (n = 8), ST239 (n = 11), and other STs (n = 7). For the antibiotic susceptibility testing, we found that all MRSA isolates in the ST239 group were highly resistant to ciprofloxacin, gentamicin trimethoprim-sulfamethoxazole, and levofloxacin. Additionally, ST239 MRSA also had a higher ability to form biofilm than other groups. Importantly, patients with ST239 infection typically had a fever and exhibited higher levels of inflammatory markers, including C-reactive protein (CRP) and white blood cell count (WBC). Epidemiological investigations revealed that knee PJIs were mainly attributed to infection with ST59 MRSA and increasing trends for infection with ST8 and other ST types of MRSAs in PJI patients were observed from 2016 to 2019. The identification of MRSA genotypes in PJIs may be helpful for the management of PJIs.

The Frequency of Occurrence of Resistance and Genes Involved in the Process of Adhesion and Accumulation of Biofilm in Staphylococcus aureus Strains Isolated from Tracheostomy Tubes

Background: Bacterial biofilm on the surface of tracheostomy tubes (TTs) is a potential reservoir of potentially pathogenic bacteria, including S. aureus. For this reason, our study aimed to investigate biofilm production in vitro and the presence of icaAD and MSCRAMM genes in clinical S. aureus strains derived from TTs, with respect to antibiotic resistance and genetic variability. Methods: The clonality of the S. aureus strains was analyzed by the PFGE method. The assessment of drug resistance was based on the EUCAST recommendations. The isolates were evaluated for biofilm production by the microtiter plate method and the slime-forming ability was tested on Congo red agar (CRA). The presence of icaAD genes was investigated by PCR and MSCRAMM genes were detected by multiplex PCR. Results: A total of 60 patients were enrolled in the study. One TT was obtained from each patient (n = 60). Twenty-one TTs (35%) were colonized with S. aureus. A total of 24 strains were isolated as 3 patients showed colonization with 2 SA clones (as confirmed by PFGE). PFGE showed twenty-two unique molecular profiles. Two isolates (8%) turned out to be MRSA, but 50% were resistant to chloramphenicol, 25% to erythromycin and 8% to clindamycin (two cMLS_B and four iMLS_B phenotypes were detected). The microtiter plate method with crystal violet confirmed that 96% of the strains were biofilm formers. Representative strains were visualized by SEM. All isolates had clfAB, fnbA, ebpS and icaAD. Different MSCRAMM gene combinations were observed. Conclusions: the present study showed that the S. aureus isolated from the TTs has a high diversity of genotypes, a high level of antibiotic resistance and ability to produce biofilm.

Unravelling the physiological roles of mazEF toxin-antitoxin system on clinical MRSA strain by CRISPR RNA-guided cytidine deaminase

Background

Curiosity on toxin–antitoxin modules has increased intensely over recent years as it is ubiquitously present in many bacterial genomes, including pathogens like Methicillin-resistant Staphylococcus aureus (MRSA). Several cellular functions of TA systems have been proposed however, their exact role in cellular physiology remains unresolved.

Methods

This study aims to find out the impact of the mazEF toxin–antitoxin module on biofilm formation, pathogenesis, and antibiotic resistance in an isolated clinical ST239 MRSA strain, by constructing mazE and mazF mutants using CRISPR–cas9 base-editing plasmid (pnCasSA-BEC). Transcriptome analysis (RNA-seq) was performed for the mazE antitoxin mutant in order to identify the differentially regulated genes. The biofilm formation was also assessed for the mutant strains. Antibiogram profiling was carried out for both the generated mutants followed by murine experiment to determine the pathogenicity of the constructed strains.

Results

For the first time our work showed, that MazF promotes cidA mediated cell death and lysis for biofilm formation without playing any significant role in host virulence as suggested by the murine experiment. Interestingly, the susceptibility to oxacillin, daptomycin and vancomycin was reduced significantly by the activated MazF toxin in the mazE mutant strain.

Conclusions

Our study reveals that activated MazF toxin leads to resistance to antibiotics like oxacillin, daptomycin and vancomycin. Therefore, in the future, any potential antibacterial drug can be designed to target MazF toxin against the problematic multi-drug resistant bug.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12929-022-00810-5.

Clonal Diversity and Epidemiological Characteristics of ST239-MRSA Strains

Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen associated with severe morbidity and mortality and poses a significant threat to public health worldwide. The genetic diversity based on sequence types of MRSA strains was illustrated in previous studies; meanwhile, the diversity along with the predominant sequence type, especially in Egypt, remains unknown. The purpose of the current study was to determine the diversity of the predominant MRSA clone ST239-MRSA (n = 50) isolated from different hosts and clinical samples and to illustrate the correlation between the resistance patterns, toxin genes, and the genetic background in Port-said and El-Sharkia Governorates, Egypt. The ST239-MRSA clone was analyzed by phenotypic antibiotyping and various genotypic assays comprising SCCmec, agr, spa, coa, and coa-RFLP in addition to toxin gene profiles. Most of the analyzed strains (40/50, 80%) were multidrug resistant (MDR), belonged to SCCmec-III, agr-I, and coa genotype I, and harbored sea and pvl genes. A negative correlation between the toxin gene profiles and antimicrobial resistance was recorded. Meanwhile, the correlation between the toxin gene profiles and the genetic background was not observed in this study. Although ST239-MRSA strains belonged to a single sequence type, they exhibited a high degree of phenotypic and genotypic diversity, indicating weak clonality and adaptability. With such diversity, it is assumed that these strains may have undergone different evolutionary processes during transmission events among and/or within a single host or tissue niche.

Biofilm Formation and Antibiotic Resistance of S. aureus Strains isolated from Chronic Traumatic Wounds

Staphylococcal biofilms are the prominent cause of chronic wound infection and antibiotic resistance. It acts as a reservoir for bacteria, making wound healing difficult. Biofilm infections increase the hospital stays and cost to the patients. The current study explores the phenotypic and genotypic detection of S. aureus biofilm from chronic traumatic wounds and their association with antibiotic resistance. A prospective observational study was conducted from April 2020 to March 2021. S. aureus isolates were identified by the MALDI-TOF. Antibiotic susceptibility was determined by VITEK 2. Biofilm production detected by tissue culture plate method and associated ica genes were diagnosed through multiplex PCR. Overall, 67 isolates were investigated. The frequency of biofilm production in S. aureus was 73.1%, and most of the isolates were moderate biofilm producers (38.8%). The presence of intracellular adhesion (ica) operon among these isolates was 85.7% and also significantly associated with the strength of biofilm mass formation. Ica A was the predominant biofilm-producing gene (42.9%). Biofilm producing Methicillin-resistant S. aureus were as high as 75%, and multidrug resistant strains were significantly associated with biofilm formation. But frequency of ica genes were noted more in Methicillin sensitive S. aureus (65.2%). High frequency of biofilm in S. aureus of isolates was responsible for the development of chronic non-healing traumatic wounds. Biofilm-producing isolates showed greater multidrug-resistance. Phenotypically MRSA expressed more biofilm, but ica operon was documented in MSSA. It emphasized the further need for ica independent pathway exploration for MRSA biofilm synthesis.

Dual-functional antibacterial and osteogenic nisin-based layer-by-layer coatings

Implanted biomaterials can be regarded in a cornerstone in the domain of bone surgery. Their surfaces are expected to fulfil two particular requirements: preventing the settlement and the development of bacteria, and stimulating bone cells in view to foster osseointegration. Therefore, a modern approach consists in the design of dual functional coatings with both antibacterial and osteogenic features. To this end, we developed ultrathin Layer-by-Layer (LbL) coatings composed of biocompatible polyelectrolytes, namely chondroitin sulfate A (CSA) and poly-l-lysine (PLL). The coatings were crosslinked with genipin (GnP), a natural and biocompatible crosslinking agent, to increase their resistance against environmental changes, and to confer them adequate mechanical properties with regards to bone cell behaviors. Antibacterial activity was obtained with nisin Z, an antimicrobial peptide (AMP), which is active against gram-positive bacteria. The coatings had a significant bactericidal impact upon Staphylococcus aureus, with fully maintained bone cell adhesion, proliferation and osteogenic differentiation.

Staphylococcus aureus ST228 and ST239 as models for expression studies of diverse markers during osteoblast infection and persistence

The ability of S. aureus to infect bone and osteoblasts is correlated with its incredible virulence armamentarium that can mediate the invasion/internalization process, cytotoxicity, membrane damage, and intracellular persistence. We comparatively analyzed the interaction, persistence, and modulation of expression of selected genes and cell viability in an ex vivo model using human MG‐63 osteoblasts of two previously studied and well‐characterized S. aureus clinical strains belonging to the ST239‐SCCmecIII‐t037 and ST228‐SCCmecI‐t041 clones at 3 h and 24 h post‐infection (p.i). S. aureus ATCC12598 ST30‐t076 was used as a control strain. Using imaging flow cytometry (IFC), we found that these strains invaded and persisted in MG‐63 osteoblasts to different extents. The invasion was evaluated at 3 h p.i and persistence at 24 h p.i., in particular: ATCC12598 internalized in 70% and persisted in 50% of MG‐63 cells; ST239‐SCCmecIII internalized in 50% and persisted in 45% of MG‐63 cells; and ST228‐SCCmecI internalized in 30% and persisted in 20% of MG‐63 cells. During the infection period, ST239‐III exerted significant cytotoxic activity resulting from overexpression of hla and psmA and increased expression of the genes involved in adhesion, probably due to the release and re‐entry of bacteria inside MG‐63 cells at 24 h p.i. The lower invasiveness of ST228‐I was also associated with non‐cytotoxic activity inside osteoblasts. This clone was unable to activate sufficient cellular reaction and succumbed inside MG‐63 cells. Our findings support the idea of considering new strategies, based on a translational approach—eukaryotic host–pathogen interaction (EHPI)—and to be applied on a large scale, to predict S. aureus /osteoblast interaction and treat bone infections. Such strategies rely on the study of the genetic and biochemical basis of both pathogen and host.

Different Modulatory Effects of Four Methicillin-Resistant Staphylococcus aureus Clones on MG-63 Osteoblast-Like Cells

Staphylococcus aureus is a Gram-positive bacterium responsible for a variety of mild to life-threatening infections including bone infections such as osteomyelitis. This bacterium is able to invade and persist within non-professional phagocytic cells such as osteoblasts. In the present study, four different S. aureus strains, namely, 2SA-ST239-III (ST239), 5SA-ST5-II (ST5), 10SA-ST228-I (ST228), and 14SA-ST22-IVh (ST22), were tested for their ability to modulate cell viability in MG-63 osteoblast-like cells following successful invasion and persistence. Methicillin-sensitive S. aureus (MSSA) ATCC-12598-ST30 (ST30) was used as control strain. Despite being proven that ST30, ST239, and ST22 have a similar ability to internalize and persist in MG-63 osteoblast-like cells under our experimental conditions, we demonstrated that the observed decrease in cell viability was due to the different behavior of the considered strains, rather than the number of intracellular bacteria. We focused our attention on different biochemical cell functions related to inflammation, cell metabolism, and oxidative stress during osteoblast infections. We were able to show the following: (1) ST30 and ST239 were the only two clones able to persist and maintain their number in the hostile environment of the cell during the entire period of infection; (2) ST239 was the only clone able to significantly increase gene expression (3 and 24 h post-infection (p.i.)) and protein secretion (24 h p.i.) of both interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) in MG-63 osteoblast-like cells; (3) the same clone determined a significant up-regulation of the transforming growth factorbeta 1 (TGF-β1) and of the metabolic marker glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNAs at 24 h p.i.; and (4) neither the MSSA nor the four methicillin-resistant S. aureus (MRSA) strains induced oxidative stress phenomena in MG-63 cells, although a high degree of variability was observed for the different clones with regard to the expression pattern of nuclear factor E2-related factor 2 (Nrf2) and its downstream gene heme oxygenase 1 (HO-1) activation. Our results may pave the way for an approach to S. aureus-induced damage, moving towards individualized therapeutic strategies that take into account the differences between MSSA and MRSA as well as the distinctive features of the different clones. This approach is based on a change of paradigm in antibiotic therapy involving a case-based use of molecules able to counteract pro-inflammatory cytokines activity such as selective cytokine signaling inhibitors (IL-6, TNF-α).

Molecular epidemiology of antimicrobial resistant microorganisms in the 21th century: a review of the literature

Healthcare-associated infections (HAIs) are the most frequent and severe complication acquired in healthcare settings with high impact in terms of morbidity, mortality and costs. Many bacteria could be implicated in these infections, but, expecially multidrug resistance bacteria could play an important role. Many microbial typing technologies have been developed until to the the bacterial whole-genome sequencing and the choice of a molecular typing method therefore will depend on the skill level and resources of the laboratory and the aim and scale of the investigation. In several studies the molecular investigation of pathogens involved in HAIs was performed with many microorganisms identified as causative agents such as Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Clostridium difficile, Acinetobacter spp., Enterobacter spp., Enterococcus spp., Staphylococcus aureus and several more minor species. Here, we will describe the most and least frequently reported clonal complex, sequence types and ribotypes with their worldwide geographic distribution for the most important species involved in HAIs.

The Novel Role of Healing from Bacterial Infections of Lower Limb Open Fractures by X-Ray Exposure

Objective

To confirm the role of X-ray exposure in treating infected wound fractures at the lower limb and determine X-ray exposure times.

Methods

Fifty-one wound swabs were collected from patients with infected open fractures at the lower limb with grade II, IIIA, B, and C according to the Gustilo and Anderson classification system and then cultured. The bacterial isolates were identified by biochemical tests and the VITEK-2 System and tested against several antibiotics. The X-ray exposure was done for open fractures by radiography (at kV133 and 5 milliambers).

Results

The higher isolation rate was recorded for Staphylococcus aureus with 21 (41.2%) isolates, and most of them (20, 95.2%) were isolated from grade II fractures. The isolation rate of Gram-negative bacteria was 25.5% for Escherichia coli with 13 isolates, 19.6% for Pseudomonas aeruginosa with 10 isolates, and 13.7% for Klebsiella pneumoniae with 7 isolates, most of which were isolated from grade III fractures. The isolation rate of P. aeruginosa was 60% (6 isolates) from grade IIIA and 71.4% (5 isolates) from grade IIIB for K. pneumoniae, while for E. coli it was 69.2% (9 isolates) from grade IIIC. All the bacterial isolates recorded high levels of antibiotic resistance against most tested antibiotics. Wound cultures of grade II fractures appeared sterile after the first X-ray exposure, and these wounds were infected with S. aureus or P. aeruginosa. However, cultures of grade IIIA and IIIB fractures appeared sterile after the second X-ray exposure for all isolated bacteria, except for S. aureus (grade IIIA fractures) (after the third X-ray exposure). Grade IIIC fractures showed sterile culture after the third X-ray exposure for wounds infected with P. aeruginosa and E. coli.

Conclusions

The study concluded that X-ray exposure showed high effectiveness in treating infected open fractures.

Detection of methicillin-resistant Staphylococcus aureus persistence in osteoblasts using imaging flow cytometry

Methicillin-resistant S. aureus has been reported as the main pathogen involved in chronic infections, osteomyelitis, and prosthetic joint infections. The host/pathogen interaction is dynamic and requires several changes to promote bacterial survival. Here, we focused on the internalization and persistence behavior of well-characterized Staphylococcus aureus invasive strains belonging to the main ST-MRSA-SCCmec clones. To overcome the limitations of the cell culture method, we comparatively analyzed the ability of internalization within human MG-63 osteoblasts with imaging flow cytometry (IFC). After evaluation by cell culture assay, the MRSA clones in the study were all able to readily internalize at 3h postinfection, the persistence of intracellular bacteria was evaluated at 24h both by routine cell culture and IFC assay, after vancomycin-BODIPY staining. A statistical difference of persistence was found in ST5-SCCmecII (26.59%), ST228-SCCmecI (20.25%), ST8-SCCmecIV (19.52%), ST239-SCCmecIII (47.82%), and ST22-SCCmecIVh (50.55%) showing the same ability to internalize as ATCC12598 (51%), the invasive isolate used as control strain for invasion and persistence assays. We demonstrated that the intracellular persistence process depends on the total number of infected cells. Comparing our data obtained by IFC with those of the cell culture assay, we obtained greater reproducibility rates and a number of intracellular bacteria, with the advantage of analyzing live host cells. Moreover, with some limitations related to the lack of whole-genome sequencing analysis, we validated the different proclivities to persist in the main Italian HA-MRSA invasive isolates and our results highlighted the heterogeneity of the different clones to persist during cell infection.

Molecular characterisation of methicillin-resistant Staphylococcus aureus isolated from patients at a tertiary care hospital in Hyderabad, South India

Context

Infections with methicillin-resistant Staphylococcus aureus (MRSA) greatly influence clinical outcome. Molecular characterisation of MRSA can help to predict their spread and to institute treatment and hospital protocols.

Aim

The aim of this study is to understand the diversity of MRSA in a tertiary care hospital in Hyderabad, India.

Settings and Design

Samples collected at Gandhi Medical College, Hyderabad, and designed to assess hospital-or community-associated MRSA (HA-MRSA or CA-MRSA).

Subjects and Methods

MRSA were subjected to antibiotic susceptibility testing, pulsed-field gel electrophoresis (PFGE), spa typing, multi-locus sequence typing and staphylococcal cassette chromosome-mec (SCCmec) typing.

Statistical Analysis Used

Discriminatory index and 95% confidence interval.

Results

Of the 30 MRSA, (a) 18 and 12 were HA-MRSA and CA-MRSA, respectively, and (b) 23.3% and 6.6% displayed induced clindamycin and intermediate vancomycin resistance, respectively. Genetic diversity was evident from the presence of (a) 20 pulsotypes, (b) eight spa types, with the predominance of t064 (n = 9) and (c) seven sequence types (ST), with the preponderance of ST22 and ST8 (9 each). ST22 and ST8 were the most prevalent among HA-MRSA and CA-MRSA, respectively. SCCmec type IV was the most frequent (n = 8). 44.4% of HA-MRSA belonged to SCCmec IV and V, whereas 33.3% of CA-MRSA belonged to SCCmec I and III; 33.3% (5/15) of the isolates harbouring the pvl gene belonged to SCCmec IVC/H.

Conclusions

ST8 was a dominant type along with other previously reported types ST22, ST239, and ST772 from India. The observations highlight the prevalence of genetically diverse clonal populations of MRSA, suggesting potential multiple origins.

Comparison of Antibiotic Resistance Profile and Biofilm Production of Staphylococcus aureus Isolates Derived from Human Specimens and Animal-Derived Samples

Background: The diffusion of antimicrobial resistance is a significant concern for public health worldwide. Staphylococcus aureus represents a paradigm microorganism for antibiotic resistance in that resistant strains appear within a decade after the introduction of new antibiotics. Methods: Fourteen S. aureus isolates from human specimens and twenty-one from samples of animal origin, were compared for their antimicrobial resistance and biofilm capability. In addition, they were characterized at the molecular level to detect the antimicrobial resistance mecA gene and genes related with enterotoxin, toxin, and biofilm production. Results: Both phenotypic and molecular analysis showed main differences among human- and animal-derived isolates. Among the human-derived isolates, more multidrug-resistant isolates were detected and mecA gene, enterotoxin, and toxin genes were more prevalent. Different genes involved in biofilm production were detected with bap present only in animal-derived isolates and sasC present in both isolates, however, with a higher prevalence in the human-derived isolates. Biofilm capability was higher in human-derived isolates mainly associated to the sasC gene. Conclusions: The overall results indicate that human S. aureus isolates are more virulent and resistant than the isolates of animal origin randomly selected with no infection anamnesis. This study confirms that selection for more virulent and resistant S. aureus strains is related to the clinical practice.