Comparison of community- and healthcare-associated methicillin-resistant Staphylococcus aureus isolates at a Chinese tertiary hospital, 2012-2017

ST105 Lineage of MRSA: An Emerging Implication for Bloodstream Infection in the American and European Continents

Sequence-type 5 (ST5) of methicillin-resistant Staphylococcus aureus (MRSA), harboring the staphylococcal chromosomal cassette mec type IV (SCCmecIV), was first detected in Portugal. It emerged as a significant cause of healthcare-associated (HA) infection in pediatric units and was hence named the pediatric clone. Another ST5 lineage, which carries SCCmecII, also prevailed in the USA and Japan for multiple years. More recently, another MRSA lineage, ST105-SCCmecII, part of the evolution of clonal complex 5 (CC5) MRSA, has emerged as the cause of hospital-acquired bloodstream infection outbreaks in countries including Portugal, the USA, and Brazil. This article reviews studies on the epidemiology and evolution of these newly emerging pathogens. To this end, a search of PUBMED from inception to 2024 was performed to find articles reporting the occurrence of ST105 MRSA in epidemiologic studies. A second search was performed to find studies on MRSA, CC5, ST5, and SCCmecII. A search of PUBMED from 1999 to 2024 was also performed to identify studies on the genomics and evolution of ST5, CC5, and ST105 MRSA. Further studies were identified by analyzing the references of the previously selected articles from PUBMED. Most articles on ST105 MRSA were included in this review. Only articles written in English were included. Furthermore, only studies that used a reliable genotyping method (e.g., whole genome sequencing, or MLST) to classify the CC5 lineages were selected. The quality and selection of articles were based on the consensus assessment of the three authors in independent evaluations. In conclusion, ST105-SCCmecII is an emerging MRSA in several countries, being the second/third most important CC5 lineage, with a relatively high frequency in bloodstream infections. Of concern is the increased mortality from BSI in patients older than 15 years and the higher prevalence of ST105-SCCmecII in the blood of patients older than 60 years reported in some studies.

Cell-wall-anchored proteins affect invasive host colonization and biofilm formation in Staphylococcus aureus

As a major human and animal pathogen, Staphylococcus aureus can attach to medical implants (abiotic surface) or host tissues (biotic surface), and further establish robust biofilms which enhances resistance and persistence to host immune system and antibiotics. Cell-wall-anchored proteins (CWAPs) covalently link to peptidoglycan, and largely facilitate the colonization of S. aureus on various surfaces (including adhesion and biofilm formation) and invasion into host cells (including adhesion, immune evasion, iron acquisition and biofilm formation). During biofilm formation, CWAPs function in adhesion, aggregation, collagen-like fiber network formation, and consortia formation. In this review, we firstly focus on the structural features of CWAPs, including their intracellular function and interactions with host cells, as well as the functions and ligand binding of CWAPs in different stages of S. aureus biofilm formation. Then, the roles of CWAPs in different biofilm processes with regards in development of therapeutic approaches are clarified, followed by the association between CWAPs genes and clonal lineages. By touching upon these aspects, we hope to provide comprehensive knowledge and clearer understanding on the CWAPs of S. aureus and their roles in biofilm formation, which may further aid in prevention and treatment infection and vaccine development.

Comparative efficacy of vancomycin in treating ST5 and ST764 methicillin-resistant Staphylococcus aureus infections in adult patients

IMPORTANCE

Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium that is resistant to multiple drugs and can cause serious infections. In recent years, one of the most widespread strains of MRSA worldwide has been the clonal complex 5 (CC5) type. Sequence type 5 (ST5) and ST764 are two prevalent CC5 strains. Although ST5 and ST764 are genotypically identical, ST764 is classified as a hybrid variant of ST5 with characteristics of community-associated MRSA (CA-MRSA). In contrast to ST5, ST764 lacks the tst and sec genes but carries the staphylococcal enterotoxin B (seb) gene. Vancomycin is commonly used as the first-line treatment for MRSA infections. However, it is currently unclear whether the genetic differences between the ST5 and ST764 strains have any impact on the efficacy of vancomycin in treating MRSA infections. We conducted a prospective observational study comparing the efficacy of vancomycin against ST5-MRSA and ST764-MRSA in five hospitals in China. There were significant differences in bacteriological efficacy between the two groups, with virulence genes, such as the tst gene, being a risk factor for bacterial persistence (adjusted odds ratio, 4.509; 95% confidence interval, 1.216 to 16.724; P = 0.024). In the future, it may be necessary to consider personalized vancomycin treatment strategies based on the genetic characteristics of MRSA isolates.

Recombination-mediated dissemination of Methicillin-resistant S. aureus clonal complex 1 in the Egyptian health care settings

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is a rapidly evolving pathogen that is frequently associated with outbreaks and sustained epidemics. This study investigated the population structure, resistome, virulome, and the correlation between antimicrobial resistance determinants with phenotypic resistance profiles of 36 representative hospital-acquired MRSA isolates recovered from hospital settings in Egypt.

RESULTS

The community-acquired MRSA lineage, clonal complex 1 (CC1) was the most frequently detected clone, followed by three other globally disseminated clones, CC121, CC8, and CC22. Most isolates carried SCCmec type V and more than half of isolates demonstrated multi-drug resistant phenotypes. Resistance to linezolid, a last resort antibiotic for treating multidrug resistant MRSA, was observed in 11.11% of the isolates belonging to different genetic backgrounds. Virulome analysis indicated that most isolates harboured a large pool of virulence factors and toxins. Genes encoding aureolysin, gamma hemolysins, and serine proteases were the most frequently detected virulence encoding genes. CC1 was observed to have a high pool of AMR resistance determinants including cfr, qacA, and qacB genes, which are involved in linezolid and quaternary ammonium compounds resistance, as well as high content of virulence-related genes, including both of the PVL toxin genes. Molecular clock analysis revealed that CC1 had the greatest frequency of recombination (compared to mutation) among the four major clones, supporting the role of horizontal gene transfer in modulating AMR and hypervirulence in this clone.

CONCLUSIONS

This pilot study provided evidence on the dissemination success of CA-MRSA clone CC1 among Egyptian hospitals. Co-detection of multiple AMR and virulence genes in this lineage pose a broad public health risk, with implications for successful treatment. The results of this study, together with other surveillance studies in Egypt, should be used to develop strategies for controlling MRSA infections in Egyptian health-care settings.

Epidemiology of Staphylococcus aureus Non-Susceptible to Vancomycin in South Asia

Staphylococcus aureus is one of the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens among which multidrug resistance has emerged. Resistance to methicillin has resulted in clinicians using the antibiotic of last resort, vancomycin, to treat infections caused by methicillin-resistant S. aureus (MRSA). However, excessive use and misuse of vancomycin are major causes of resistance among S. aureus strains. South Asia encompasses ~25% of the world's population, and countries in South Asia are often characterized as low- and middle-income with poor healthcare infrastructure that may contribute to the emergence of antibiotic resistance. Here, we briefly highlight the mechanism of vancomycin resistance, its emergence in S. aureus, and the molecular epidemiology of non-susceptible S. aureus to vancomycin in the South Asian region.

Epigenetic and Drug Response Modulation of Epigalocaten-In-3-Gallate in Staphylococcus aureus with Divergent Resistance Phenotypes

Healthcare-associated methicillin-resistant Staphylococcus aureus infections represent extremely high morbidity and mortality rates worldwide. We aimed to assess the antimicrobial potential and synergistic effect between Epigalocatenin-3-gallate (EGCG) and different antibiotics in S. aureus strains with divergent resistance phenotypes. EGCG exposure effects in epigenetic and drug resistance key modulators were also evaluated. S. aureus strains (n = 32) were isolated from infected patients in a Lisbon hospital. The identification of the S. aureus resistance phenotype was performed through automatized methods. The antibiotic synergistic assay was performed through disk diffusion according to EUCAST guidelines with co-exposure to EGCG (250, 100, 50 and 25 µg/mL). The bacteria’s molecular profile was assessed through FTIR spectroscopy. The transcriptional expression of OrfX, SpdC and WalKR was performed by using qRT-PCR. FTIR-spectroscopy analysis enabled the clear discrimination of MRSA/MSSA strains and the EGCG exposure effect in the bacteria’s molecular profiles. Divergent resistant phenotypes were associated with divergent transcriptional expression of the epigenetic modulator OrfX, particularly in MRSA strains, as well as the key drug response modulators SpdC and WalKR. These results clearly demonstrate that EGCG exposure alters the expression patterns of key epigenetic and drug response genes with associated divergent-resistant profiles, which supports its potential for antimicrobial treatment and/or therapeutic adjuvant against antibiotic-resistant microorganisms.

Pet animals as reservoirs for spreading methicillin-resistant Staphylococcus aureus to human health

Methicillin-resistant Staphylococcus aureus (MRSA) is a strain of pathogenic bacteria that is a major problem in the world's health. Due to their frequent interaction with humans, pets are one of the main risk factors for the spread of MRSA. The possibility for zoonotic transmission exists since frequently kept dogs and cats are prone to contract MRSA and act as reservoirs for spreading MRSA. The mouth, nose, and perineum are the primary locations of MRSA colonization, according to the findings of MRSA identification tests conducted on pets. The types of MRSA clones identified in cats and dogs correlated with MRSA clones infecting humans living in the same geographic area. A significant risk factor for the colonization or transmission of MRSA is human-pet contact. An essential step in preventing the spread of MRSA from humans to animals and from animals to humans is to keep hands, clothing, and floor surfaces clean.

Limosilactobacillus fermentum 3872 That Produces Class III Bacteriocin Forms Co-Aggregates with the Antibiotic-Resistant Staphylococcus aureus Strains and Induces Their Lethal Damage

LF3872 was isolated from the milk of a healthy lactating and breastfeeding woman. Earlier, the genome of LF3872 was sequenced, and a gene encoding unique bacteriocin was discovered. We have shown here that the LF3872 strain produces a novel thermolabile class III bacteriolysin (BLF3872), exhibiting antimicrobial activity against antibiotic-resistant Staphylococcus aureus strains. Sequence analysis revealed the two-domain structural (lysozyme-like domain and peptidase M23 domain) organization of BLF3872. At least 25% residues of this protein are expected to be intrinsically disordered. Furthermore, BLF3872 is predicted to have a very high liquid-liquid phase separation. According to the electron microscopy data, the bacterial cells of LF3872 strain form co-aggregates with the S. aureus 8325-4 bacterial cells. LF3872 produced bacteriolysin BLF3872 that lyses the cells of the S. aureus 8325-4 mastitis-inducing strain. The sensitivity of the antibiotic-resistant S. aureus collection strains and freshly isolated antibiotic-resistant strains was tested using samples from women with lactation mastitis; the human nasopharynx and oral cavity; the oropharynx of pigs; and the cows with a diagnosis of clinical mastitis sensitive to the lytic action of the LF3872 strain producing BLF3872. The co-cultivation of LF3872 strain with various antibiotic-resistant S. aureus strains for 24 h reduced the level of living cells of these pathogens by six log. The LF3872 strain was found to be able to co-aggregate with all studied S. aureus strains. The cell-free culture supernatant of LF3872 (CSLF3872) induced S. aureus cell damage and ATP leakage. The effectiveness of the bacteriolytic action of LF3872 strain did not depend on the origin of the S. aureus strains. The results reported here are important for the creation of new effective drugs against antibiotic-resistant strains of S. aureus circulating in humans and animals.

ST7 Becomes One of the Most Common Staphylococcus aureus Clones After the COVID-19 Epidemic in the City of Wuhan, China

Background

Staphylococcus aureus (S. aureus) was able to rapidly evolve and adapt under the pressure of antibiotics, host immune and environmental change. After Corona Virus Disease 2019 (COVID-19) epidemic in Wuhan, China, a large number of disinfectants were used, which might result in rapid evolution of S. aureus.

Methods

A total of 619 S. aureus isolates were collected from Zhongnan Hospital, Wuhan University from 2018 to 2021, including group BEFORE (309 strains collected before COVID-19 pandemic) and group AFTER (310 strains collected after COVID-19 pandemic), for comparing the changes of molecular epidemiology. The molecular characteristics of isolates were analyzed by Multi-locus sequence typing (MLST), spa, chromosomal cassette mec (SCCmec) typing, virulence genes were screened by the PCR, antibiotic susceptibility test was carried out by the VITEK system.

Results

Thirty-six sequence types (STs) belonging to 14 clone complexes (CCs) were identified. ST5 was the most prevalent clone in both groups, and ST7, ranking the sixth in group BEFORE, became the second dominant clone in group AFTER (6.5% vs 10.0%), whereas ST239 decreased from the seventh to the fourteenth (5.8% vs 1.9%). ST7 in group AFTER had a higher positive rate of virulence genes, including hlb, fnbB, seb, lukDE, sdrE and the proportion of ST7-t091 MRSA strains increased from 19.1% to 50% compared with group BEFORE. Though no significant difference of MRSA proportion was found between two groups, SCCmec type-III in group AFTER decreased (p<0.01). Though the rate of multidrug-resistance (MDR) decreased, the virulence genes hlb, hlg, fnbB, seb and pvl carrying rates were significantly elevated in MRSA strains of group AFTER.

Conclusion

After COVID-19 pandemic, ST7 becomes one of the predominant S. aureus clones in Wuhan and the carrying rate of SCCmec and virulence genes is on the rise. Therefore, it is essential to strengthen the surveillance of ST7 S. aureus clone.

An emerging Panton-Valentine leukocidin-positive CC5-meticillin-resistant Staphylococcus aureus-IVc clone recovered from hospital and community settings over a 17-year period from 12 countries investigated by whole-genome sequencing

BACKGROUND

A novel Panton-Valentine leukocidin (PVL)-positive meticillin-resistant Staphylococcus aureus (MRSA) clonal complex (CC)5-MRSA-IVc ('Sri Lankan' clone) was recently described from Sri Lanka. Similar isolates caused a recent Irish hospital outbreak.

AIM

To investigate the international dissemination and diversity of PVL-positive CC5-MRSA-IVc isolates from hospital and community settings using whole-genome sequencing (WGS).

METHODS

Core-genome single nucleotide polymorphism (cgSNP) analysis, core-genome multi-locus sequence typing (cgMLST) and microarray-based detection of antimicrobial-resistance and virulence genes were used to investigate PVL-positive CC5-MRSA-IVc (N = 214 including 46 'Sri Lankan' clone) from hospital and community settings in 12 countries over 17 years. Comparators included 29 PVL-positive and 23 PVL-negative CC5/ST5-MRSA-I/II/IVa/IVc/IVg/V.

RESULTS

Maximum-likelihood cgSNP analysis grouped 209/214 (97.7%) CC5-MRSA-IVc into Clade I; average of 110 cgSNPs between isolates. Clade III contained the five remaining CC5-MRSA-IVc; average of 92 cgSNPs between isolates. Clade II contained seven PVL-positive CC5-MRSA-IVa comparators, whereas the remaining 45 comparators formed an outlier group. Minimum-spanning cgMLST analysis revealed a comparably low average of 57 allelic differences between all CC5/ST5-MRSA-IVc. All 214 CC5/ST5-MRSA-IVc were identified as 'Sri Lankan' clone, predominantly spa type t002 (186/214) with low population diversity and harboured a similar range of virulence genes and variable antimicrobial-resistance genes. All 214 Sri Lankan clone isolates and Clade II comparators harboured a 9616-bp chromosomal PVL-encoding phage remnant, suggesting both arose from a PVL-positive meticillin-susceptible ancestor. Over half of Sri Lankan clone isolates were from infections (142/214), and where detailed metadata were available (168/214), most were community associated (85/168).

CONCLUSIONS

Stable chromosomal retention of pvl may facilitate Sri-Lankan clone dissemination.

Molecular Characterization of Community- and Hospital- Acquired Methicillin-Resistant Staphylococcus aureus Isolates during COVID-19 Pandemic

Methicillin-resistant Staphylococcus aureus (MRSA) is a drug-resistant superbug that causes various types of community- and hospital-acquired infectious diseases. The current study was aimed to see the genetic characteristics and gene expression of MRSA isolates of nosocomial origin. A total of 221 MRSA isolates were identified from 2965 clinical samples. To identify the bacterial isolates, the clinical samples were inoculated on blood agar media plates first and incubated at 37 °C for 18-24 h. For further identification, the Gram staining and various biochemical tests were performed once the colonies appeared on the inoculated agar plates. The phenotypic identification of antibiotic susceptibility patterns was carried out using Kirby-Bauer disk diffusion method by following the Clinical and Laboratory Standards Institute (CLSI) 2019 guidelines. The biofilm-producing potentials of MRSA were checked quantitatively using a spectrophotometric assay. All strains were characterized genotypically by SCCmec and agr typing using the specific gene primers. Furthermore, a total of twelve adhesion genes were amplified in all MRSA isolates. MRSA was a frequently isolated pathogen (44% community acquired (CA)-MRSA and 56% hospital acquired (HA)-MRSA), respectively. Most of the MRSA isolates were weak biofilm producers (78%), followed by moderate (25%) and strong (7%) biofilm producers, respectively. Prominent adhesion genes were clfB (100%), icaAD (91%), fib (91%), sdrC (91%) followed by eno (89%), fnbA (77%), sdrE (67%), icaBC (65%), clfA (65%), fnbB (57%), sdrD (57%), and cna (48%), respectively. The results of the current study will help to understand and manage the spectrum of biofilm-producing MRSA-associated hospital-acquired infections and to provide potential molecular candidates for the identification of biofilm-producing MRSA.

Vancomycin Resistance in Enterococcus and Staphylococcus aureus

Enterococcus faecalis, Enterococcus faecium and Staphylococcus aureus are both common commensals and major opportunistic human pathogens. In recent decades, these bacteria have acquired broad resistance to several major classes of antibiotics, including commonly employed glycopeptides. Exemplified by resistance to vancomycin, glycopeptide resistance is mediated through intrinsic gene mutations, and/or transferrable van resistance gene cassette-carrying mobile genetic elements. Here, this review will discuss the epidemiology of vancomycin-resistant Enterococcus and S. aureus in healthcare, community, and agricultural settings, explore vancomycin resistance in the context of van and non-van mediated resistance development and provide insights into alternative therapeutic approaches aimed at treating drug-resistant Enterococcus and S. aureus infections.

Review of pork and pork products as a source for transmission of methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is an opportunistic bacterium that can cause infection in animals and humans. Recently, MRSA from food-producing or farm animals has been identified as livestock-associated MRSA (LA-MRSA). The spread of LA-MRSA is particularly found in pork and pork products because LA-MRSA has been widely known to infect pigs. The most common type of LA-MRSA identified in pork and pork products is the clonal complex LA-MRSA 398 (LA-MRSA CC398). The MRSA strains on the surface of pork carcasses can be spread during the handling and processing of pork and pork products through human hands, cutting tools, and any surface that comes into direct contact with pork. Food infection is the main risk of MRSA in pork and pork products consumed by humans. Antibiotics to treat food infection cases due to MRSA infection include vancomycin and tigecycline. The spread of MRSA in pork and pork products is preventable by appropriately cooking and cooling the pork and pork products at temperatures above 60°C and below 5°C, respectively. It is also necessary to take other preventive measures, such as having a clean meat processing area and disinfecting the equipment used for processing pork and pork products. This review aimed to explain epidemiology, transmission, risk factors, diagnosis, public health consequences, treatment of food poisoning, and preventing the spread of MRSA in pork and pork products.

Impact of the WHO Integrated Stewardship Policy on the Control of Methicillin-Resistant Staphyloccus aureus and Third-Generation Cephalosporin-Resistant Escherichia coli: Using a Mathematical Modeling Approach

Methicillin-resistant Staphylococcus aureus (MRSA) and third-generation cephalosporin-resistant Escherichia coli (3GCREc) are community and hospital-associated pathogens causing serious infections among populations by infiltrating into hospitals and surrounding environment. These main multi-drug resistant or antimicrobial resistance (AMR) bacterial pathogens are threats to human health if not properly tackled and controlled. Tackling antimicrobial resistance (AMR) is one of the issues for the World Health Organization (WHO) to design a comprehensive set of interventions which also helps to achieve the end results of the developing indicators proposed by the same organization. A deterministic mathematical model is developed and studied to investigate the impact of the WHO policy on integrated antimicrobial stewardship activities to use effective protection measures to control the spread of AMR diseases such as MRSA and 3GCREc in hospital settings by incorporating the contribution of the healthcare workers in a hospital and the environment in the transmission dynamics of the diseases. The model also takes into account the parameters describing various intervention measures and is used to quantify their contribution in containing the diseases. The impact of combinations of various possible control measures on the overall dynamics of the disease under study is investigated. The model analysis suggests that the contribution of the interventions: screening and isolating the newly admitted patients, improving the hygiene in hospital settings, decolonizing the pathogen carriers, and increasing the frequency of disinfecting the hospital environment are effective tools to contain the disease from invading the population. The study revealed that without any intervention, the diseases will continue to be a major cause of morbidity and mortality in the affected communities. In addition, the study indicates that a coordinated implementation of the integrated control measures suggested by WHO is more effective in curtailing the spread of the diseases than piecemeal strategies. Numerical experiments are provided to support the theoretical analysis.

Characteristics of Virulence Genes of Clinically Isolated Staphylococci in Jingzhou Area

Purpose

The aim of this study was to further understand the distribution characteristics of staphylococcal virulence genes in the Jingzhou area, in order to provide a basis for clinically effective treatments and prevention and control measures.

Methods

A total of 181 strains of staphylococci were collected from Jingzhou Hospital Affiliated to Yangtze University from April 2013 to April 2021, which were divided into the methicillin-resistant Staphylococcus aureus (MRSA) strains and the methicillin-sensitive Staphylococcus aureus (MSSA) strains and coagulase-negative staphylococci (CoNS) by an antimicrobial susceptibility test and PCR method. The 73 MRSA strains were classified by staphylococcal cassette chromosome mec (SCCmec) and Staphylococcus protein A (Spa). Sea, sec, seh, sek, seb, seq, sep, Tsst-1, clfA, clfB, fnbA, hla, hld, hlg, lukE, bbp, cna, eap, ebpS, sdrC, sdrD, sdrE, and Pvl genes were also detected in all strains. The χ² test was used for statistical analysis for comparison between groups.

Results

The 181 strains of staphylococci were divided into 97 strains of MRSA, 54 strains of MSSA, and 30 strains of CoNS. 73 MRSA strains were derived from clinical specimens such as lower respiratory tract, secretions, sepsis secreted by tissue infection, urine, and hydrothorax. There were 70 strains that can be identified including SCCmec types and 15 Spa types of all strains, while the most popular types were SCCmecIII-t030 and SCCmecIV-t437 from lower respiratory tract specimens. There were four virulence genes that were detected including seb, seq, clfB, and hld in CoNS strains, while the detection rates of these four virulence genes in Staphylococcus aureus were higher than that of CoNS, and the differences were statistically significant, P < 0.05(P=0.004, P=0.001, P=0.001, P=0.001). 23 virulence genes were detected in 151 strains of Staphylococcus aureus, among which the detection rate of the Tsst-1 gene was the lowest and that of the clfB gene was the highest, and the other genes were 4.6%∼98.0%. The detection rates of sea, sek, seb, seq, sep, cna, eap, ebpS, sdrC, and sdrE virulence genes in MRSA were higher than that of MSSA, and the differences were statistically significant, P < 0.05 (P=0.001, P=0.001, , P=0.001, P=0.001, P=0.009, , P=0.019, P=0.001, , P=0.001, P=0.001, , P=0.003).

Conclusion

The mainly prevalent type of MRSA strains in Jingzhou is SCCmecIII-t030 in lower respiratory tract specimens. Virulence genes of Staphylococcus aureus and antibiotic drug resistance rates are also different from other regions. In this experiment, virulence genes were also detected in CoNS, suggesting that more attention should be paid to the prevention and treatment of these strains clinically.

High prevalence of Panton-Valentine leukocidin positive, multidrug resistant, Methicillin-resistant Staphylococcus aureus strains circulating among clinical setups in Adamawa and Far North regions of Cameroon

Staphylococcus aureus (S. aureus) is one of the earliest pathogens involved in human infections, responsible for a large variety of pathologies. Methicillin was the first antibiotic used to treat infections due to S. aureus but infections due to Methicillin resistant Staphylococcus aureus (MRSA) originated from hospital settings. Later, severe infections due to MRSA without any contact with the hospital environment or health care workers arose. Prevalence of MRSA has shown an alarming increase worldover including Cameroon. This Cross-sectional study was designed to evaluate the occurrence of MRSA infections in five different, most frequented Hospitals in northern Cameroon. Socio demographic data was recorded through questionnaire and different clinical specimens were collected for bacterial isolation. Identification of S. aureus was confirmed via 16s rRNA amplification using S. aureus specific primers. Molecular characterisation was performed through mecA gene, Luk PV gene screening and SCCmec typing. A total of 380 S. aureus clinical isolates were obtained of which 202 (53.2%) were nonduplicate multidrug resistant isolates containing, 45.5% MRSA. Higher number of MRSA was isolated from pus (30.4%) followed by blood culture (18.5%), and urine (17.4%). Patients aged 15 to 30 years presented high prevalence of MRSA (30.4%). Majority isolates (97.8%) carried the mecA gene, PVL toxin screening indicated 53.3% isolates carried the lukPV gene. Based on PVL detection and clinical history, CA-MRSA represented 53.3% of isolates. SCCmec typing showed that the Type IV was most prevalent (29.3%), followed by type I (23.9%). Amongst MRSA isolates high resistance to penicillin (91.1%), cotrimoxazole (86.7%), tetracycline (72.2%), and ofloxacin (70.0%) was detected. Meanwhile, rifampicin, fusidic acid, lincomycin and minocycline presented high efficacy in bacterial control. This study revealed a high prevalence of MRSA among infections due to S. aureus in Northern Cameroon. All MRSA recorded were multidrug resistant and the prevalence of CA MRSA are subsequently increasing, among population.

Performance Evaluation of the IR Biotyper® System for Clinical Microbiology: Application for Detection of Staphylococcus aureus Sequence Type 8 Strains

Background: Methicillin-resistant S. aureus (MRSA) clonal lineages have been classified based on sequence type (ST) and pulsotype associated with human infection. Providing rapid and accurate epidemiological insight is important to address proper infection control in both community-acquired and nosocomial hospital settings. In this regard, this study was performed to evaluate the IR Biotyper^® (IRBT^®) for strain typing of S. aureus clinical isolates on three media. Methods: A total of 24 S. aureus clinical isolates comprising 15 MRSA isolates (six ST5, three ST72, three ST8, and three ST188 isolates) and nine methicillin-susceptible S. aureus (MSSA) isolates (three ST5, three ST72, and three ST8 isolates) were included for evaluating the IRBT^®. Molecular characterization of all S. aureus isolates was performed by conventional PCR and sequencing methods. The IRBT^® was evaluated according to manufacturer instructions and a modified sample procedure on commonly used BAP, MHA, and TSA media. Subsequently, the spectra obtained by IRBT^® software were compared with dendrograms of PFGE analysis. Results: In this study, the modified sample procedure for reducing the amount of bacteria and bacterial concentration improved the acquisition quality pass rate of the IRBT^®. Each spectrum of S. aureus ST5, ST72, and ST188 isolates on all three media could not be clustered by IRBT^®. However, the dendrogram obtained from the spectra of S. aureus ST8 isolates on TSA medium were in concordance with that obtained by PFGE analysis. In addition, the visual distribution of S. aureus ST8 isolates on TSA medium in a 2D scatter plot appeared as separated point set from those of S. aureus ST5, ST72, and ST188 isolates. Conclusions: The IRBT^® system is a rapid strain typing tool using the FTIR spectroscopic method. This system demonstrated the possibility of discriminating the strain types of S. aureus clinical isolates. Indeed, S. aureus ST8 isolates on TSA medium were successfully differentiated from other strain type isolates.

Staphylococcal Cassette Chromosome mec Typing and Multilocus Variable Number Tandem Repeat Analysis of Methicillin Resistant Staphylococcus aureus Clinical Isolates with Vancomycin Creep Phenomenon

Background

The association of treatment failure and mortality with vancomycin minimum inhibitory concentration creep (MIC) is a matter of serious concern in patients with severe methicillin resistant Staphylococcus aureus (MRSA) infections. The purpose of the study was to identify and characterize staphylococcal cassette chromosome mec (SCCmec) and clonal types of MRSA strains, exhibiting the vancomycin MIC creep phenomenon.

Methods

A total of 3305 S. aureus strains were isolated from various clinical samples of Lahore General Hospital, Lahore, Pakistan. MRSA strains were identified by cefoxitin resistant (≤21mm) followed by mecA and mecC gene genotyping. Vancomycin MIC creep was determined by E-test. Isolates having MIC values >1.5 µg/mL were further subjected for SCCmec typing (I–V and XI) and multiple-locus variable number tandem repeat analysis (MLVA) by amplification of spa, sspA, clfA, clfB, and sdrCDE genes. A dendrogram was created based on the similarity index using bioneumerics software.

Results

About 13.3% (440/3305) isolates were MRSA with 99.3% (437/440) and 0.7% (3/440) carried mecA and mecC genes, respectively. In 120 MRSA isolates, the MIC of vancomycin was >1.5µg/mL. In MRSA isolates with high vancomycin MIC (>1.5µg/mL), the most common SCCmec type was SCCmec III (38.3%), followed by SCCmec IVa (15.8%), SCCmec IIIa (13.3%,), SCCmec IVc (7.5%), SCCmec IVe (5.8%), SCCmec IVd (5.8%), SCCmec IVb (4.2%), SCCmec II (2.5%), SCCmec V (1.7%), SCCmec I (1.7%) and SCCmec XI (1.7%). MLVA revealed 60 genotypic groups of MRSA isolates having a 92% similarity index.

Conclusion

SCCmec III was the most common type in genetically related MRSA isolates showing vancomycin MIC creep. The presence of SCCmec XI may further add burden to infection control measures.

Antimicrobial resistance pattern of methicillin-resistant Staphylococcus aureus isolated from sheep and humans in Veterinary Hospital Maiduguri, Nigeria

Background and Aim: Methicillin-resistant Staphylococcus aureus (MRSA), an important opportunistic pathogen, is a Gram-positive coccus known to be resistant to β-lactam antibiotics. Its virulence depends on a large range of factors, mainly extracellular proteins, such as enzymes and exotoxins, that contribute to causing a wide range of diseases in human and animal species. The major reasons for the success of this pathogen are its great variability, which enables it to occur and thrive at different periods and places with diverse clonal types and antibiotic resistance patterns within regions and countries. Infections caused by antibiotic-resistant S. aureus bring about serious problems in the general population (humans and animals). Infections with these pathogens can be devastating, particularly for the very young, adults and immunocompromised patients in both humans and animals. This study aimed to determine the presence of MRSA in both apparently healthy and sick sheep brought to the veterinary hospital as well as veterinary staff and students on clinical attachment in the hospital. Materials and Methods: A total of 200 nasal swab samples were collected aseptically from sheep and humans (100 each) for the isolation of MRSA. The samples were processed by appropriately transporting them to the laboratory, then propagated in nutrient broth at 37°C for 24 h followed by subculturing on mannitol salt agar at 37°C for 24 h, to identify S. aureus. This was followed by biochemical tests (catalase and coagulase tests) and Gram staining. MRSA was isolated using Clinical Laboratory Standard Institute (CLSI) guideline and confirmed by plating onto Oxacillin (OX) Resistance Screening Agar Base agar. The antimicrobial susceptibility pattern of the MRSA isolates was determined using the disk diffusion method against 12 commonly used antimicrobial agents. Results: The total rate of nasal carriage of S. aureus and MRSA was found to be 51% and 43% in sheep and humans, respectively. The MRSA prevalence in male and female sheep was 18% and 8%, while 9% and 8% were for male and female human samples, respectively. The antimicrobial susceptibility test showed 100% resistance to OX, cefoxitin, oxytetracycline, cephazolin, and penicillin-G (Pen) by MRSA isolates from humans. Conversely, there was 100% susceptibility to ciprofloxacin, imipenem, and gentamicin; for linezolid (LZD), it was 87.5%, norfloxacin (NOR) (71%), and erythromycin (ERY) (50%) susceptibility was recorded. The MRSA isolates from sheep recorded 100% resistance to the same set of drugs used for human MRSA isolates and were equally 100% susceptible to gentamicin, imipenem, LZD, ciprofloxacin, NOR (92%), and ERY (50%). Conclusion: This study determined the presence of MRSA in sheep and humans from the Veterinary Hospital, Maiduguri. It appears that certain drugs such as ciprofloxacin, imipenem, and gentamicin will continue to remain effective against MRSA associated with humans and sheep. Reasons for the observed patterns of resistance must be explored to reduce the burdens of MRSA resistance. Furthermore, the present study did not confirm the MRSA resistance genes such as mecA and spa typing to ascertain the polymorphism in the X-region using appropriate molecular techniques. Hence more studies need to be conducted to elucidate these findings using robust techniques.

Role of horizontally transferred copper resistance genes in Staphylococcus aureus and Listeria monocytogenes

Bacteria have evolved mechanisms which enable them to control intracellular concentrations of metals. In the case of transition metals, such as copper, iron and zinc, bacteria must ensure enough is available as a cofactor for enzymes whilst at the same time preventing the accumulation of excess concentrations, which can be toxic. Interestingly, metal homeostasis and resistance systems have been found to play important roles in virulence. This review will discuss the copper homeostasis and resistance systems in Staphylococcus aureus and Listeria monocytogenes and the implications that acquisition of additional copper resistance genes may have in these pathogens.

Draft Genome Sequences of 27 Hospital-Associated Methicillin-Resistant Staphylococcus aureus Strains Isolated in Minnesota

Infections caused by hospital-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) strains have higher morbidity and mortality rates and require longer hospital stays than do those caused by hospital-associated methicillin-sensitive Staphylococcus aureus strains. To gain insight into their genomic makeup, antimicrobial resistance, biofilm formation, and virulence potentials, here we present the draft whole-genome sequences of 27 HA-MRSA strains isolated in Minnesota.

Staphylococcus aureus Isolated from the Oral Cavity: Phage Susceptibility in Relation to Antibiotic Resistance

Nowadays, research on bacteriophage therapy and its potential use in combination with antibiotics has been gaining momentum. One hundred and ten oral Staphylococcus aureus isolates were phage-typed and their antibiotic resistance was determined by standard and molecular methods. The prevalence of MSSA and MRSA strains was 89.1% and 10.9%, respectively. Nearly all (91.8%) analyzed isolates, whether MSSA or MRSA, were susceptible to the phages used from the international set. The highest lytic activity showed phages 79 and 52 A from lytic group I. The predominant phage groups were mixed, the I+III group and a mixed group containing phages from at least three various lytic groups. S. aureus strains sensitive to phage group I were usually resistant to penicillin and susceptible to ciprofloxacin, whereas the strains typeable with group V or group V with the 95 phage were susceptible to most antibiotics. Epidemic CA-MRSA strains (SCCmecIV) of phage type 80/81 carried Panton–Valentine leucocidin genes. Considering the high sensitivity of oral S. aureus to the analyzed phages and the promising results of phage therapies reported by other authors, phage cocktails or phage-antibiotic combinations may potentially find applications in both the prevention and eradication of staphylococcal infections.

Methicillin-resistant Staphylococcus aureus colonization of infectious and non-infectious skin and soft tissue lesions in patients in Tehran

Background

The most common clinical manifestations of Staphylococcus aureus strains in the community are skin and soft-tissue infections. S. aureus could colonize the body sites and complicate the pathogenesis of skin diseases. S. aureus colonization is a risk factor for severe conditions such as bone and joint infections, pneumonia, bacteremia, and endocarditis. This study aimed to investigate the prevalence of S. aureus strains in skin and soft tissue infections and other skin disorders in patients referring to dermatology clinics and to evaluate the antibiotic resistance pattern and molecular characteristics of S. aureus isolates.

Methods

Skin swabs were collected from the lesional sites in 234 outpatients referring to dermatology clinics in three hospitals in Tehran. Antibiotic susceptibility, biofilm formation, and hemolysis tests were performed for isolates. PCR was done for SCCmec typing, agr grouping, and virulence genes detecting.

Results

The prevalence of S. aureus strains among patients with skin and soft-tissue infections and other skin lesions was 44.77% (30/67) and 44.91% (75/167), respectively. Also, 59 (56.19%) isolates were MRSA, 35.57% were HA-MRSA, and 30.5% were CA-MRSA. The psmα gene was more prevalent (62.8%) among isolates, followed by hlaα (56.1%), tsst-1 (15.2%) eta (13.3%), etb (6.6%), and pvl (2.8%). The agr specificity groups I, II, III, and IV were identified in 49.5, 21.9, 11.4, and 14.2% of S. aureus isolates, respectively. Most (56%) S. aureus isolates produced a moderate biofilm, and 23.8% of them produced strong biofilms. α-hemolysin (46.6%), β-hemolysin (25.7%), γ-hemolysin (19%), and both α and β-hemolysin (5.7%) were also produced by isolates.

Conclusion

The present study results indicated high colonization of skin lesions by HA-MRSA and CA-MRSA clones; MRSA strains were more resistant to antibiotics, contained various toxin genes, and were able to form biofilms. Therefore, they could play a vital role in the pathogenesis of various skin diseases; also, they could spread and cause infections in other body sites. Eradication and decolonization strategies could prevent recurrent infections and the spread of resistant strains and improve skin conditions.

Molecular Diversity of Methicillin-Resistant and -Susceptible Staphylococcus aureus Detected in Animals: A Focus on Aquatic Animals

Staphylococcus aureus (S. aureus) are one of the best-known opportunistic pathogens capable of causing different types of infections in animals. Furthermore, it has the ability to acquire resistance to various antibiotics very easily. Methicillin-resistant S. aureus (MRSA) are currently of great concern as they are the leading cause of infections in humans and animals, with a major impact on health and the economy. Several studies already demonstrate that the spread of MRSA is constantly increasing due to its ability to form reservoirs in humans, animals and the environment. In fact, several works have already identified the presence of these bacteria in animals, including domestic animals, farm animals and even wild animals. Furthermore, the incidence of various S. aureus strains in aquatic animals has also been reported by different authors, although it is still a rarely discussed topic. Some of these strains have previously been associated with humans and other animals. Strain 398 is the strain that manages to infect a wider spectrum of hosts, having been identified in several different species. Aside from this strain, many others have yet to be identified. In addition, many of these strains have virulence factors and antibiotic resistance genes that worsen the situation. The present work is a review of studies that intend to investigate the epidemiology of this agent in samples of aquatic animals from different origins, in order to better understand its distribution, prevalence and the molecular lineages associated with these species.

Ecology and Genetic Lineages of Nasal Staphylococcus aureus and MRSA Carriage in Healthy Persons with or without Animal-Related Occupational Risks of Colonization: A Review of Global Reports

In this conceptual review, we thoroughly searched for appropriate English articles on nasal staphylococci carriage among healthy people with no reported risk of colonization (Group A), food handlers (Group B), veterinarians (Group C), and livestock farmers (Group D) published between 2000 and 2021. Random-effects analyses of proportions were performed to determine the pooled prevalence of S. aureus, MRSA, MRSA-CC398, and MSSA-CC398, as well as the prevalence of PVL-positive S. aureus from all eligible studies. A total of 166 eligible papers were evaluated for Groups A/B/C/D (n = 58/31/26/51). The pooled prevalence of S. aureus and MRSA in healthy humans of Groups A to D were 15.9, 7.8, 34.9, and 27.1%, and 0.8, 0.9, 8.6, and 13.5%, respectively. The pooled prevalence of MRSA-CC398 nasal carriage among healthy humans was as follows: Group A/B (<0.05%), Group C (1.4%), Group D (5.4%); and the following among Group D: pig farmers (8.4%) and dairy farmers (4.7%). The pooled prevalence of CC398 lineage among the MSSA and MRSA isolates from studies of the four groups were Group A (2.9 and 6.9%), B (1.5 and 0.0%), C (47.6% in MRSA), and D (11.5 and 58.8%). Moreover, MSSA-CC398 isolates of Groups A and B were mostly of spa-t571 (animal-independent clade), while those of Groups C and D were spa-t011 and t034. The MRSA-CC398 was predominately of t011 and t034 in all the groups (with few other spa-types, livestock-associated clades). The pooled prevalence of MSSA and MRSA isolates carrying the PVL encoding genes were 11.5 and 9.6% (ranges: 0.0-76.9 and 0.0-28.6%), respectively. Moreover, one PVL-positive MSSA-t011-CC398 isolate was detected in Group A. Contact with livestock and veterinary practice seems to increase the risk of carrying MRSA-CC398, but not in food handlers. Thus, this emphasizes the need for integrated molecular epidemiology of zoonotic staphylococci.

Systematic review and meta-analysis of the epidemiology of vancomycin-resistance Staphylococcus aureus isolates

BACKGROUND

Vancomycin‑resistant Staphylococcus aureus (VRSA) is a serious public health challenging concern worldwide.

OBJECTIVES

Therefore, the objective of present study of 62 published studies was to evaluate the prevalence of VRSA based on different years, areas, isolate source, antimicrobial susceptibility testing, and the genetic determinants.

METHODS

We searched the relevant articles that focused on the prevalence rates of VRSA in PubMed, Scopus, Embase, and Web of Science from 2000 to 2019. Statistical analyses were conducted using STATA software (version 14.0).

RESULTS

The prevalence of VRSA was 2% before 2006, 5% in 2006-2014, and 7% in 2015-2020 that showed a 3.5-fold increase in the frequency of VRSA between before 2006 and 2020 years. The prevalence of VRSA was 5% in Asia, 1% in Europe, 4% in America, 3% in South America, and 16% in Africa. The frequencies of VRSA isolated from clinical, non-clinical, and mixed samples were 6%, 7%, and 14%, respectively. The prevalence of VRSA was 12% using disk diffusion agar method, 7% using MIC-base methods, and 4% using mixed-methods. The prevalence of vanA, vanB, and vanC1 positive were 71%, 26%, and 4% among VRSA strains. The most prevalent genotype was staphylococcal cassette chromosomemec (SCCmec) II, which accounted for 57% of VRSA. The most prevalent staphylococcal protein A (spa) types were t002, t030, and t037.

CONCLUSION

The prevalence of VRSA has been increasing in recent years particularly in Africa/Asia than Europe/America. The most prevalent of genetic determinants associated with VRSA were vanA and SCCmec II. This study clarifies that the rigorous monitoring of definite antibiotic policy, regular surveillance/control of nosocomial-associated infections and intensive surveillance of vancomycin-resistance are required for preventing emergence and further spreading of VRSA.

Molecular Characteristics of Staphylococcus aureus From Food Samples and Food Poisoning Outbreaks in Shijiazhuang, China

As an opportunistic pathogen worldwide, Staphylococcus aureus can cause food poisoning and human infections. This study investigated the sequence typing, the penicillin (blaZ) and methicillin (mec) resistance profiles of S. aureus from food samples and food poisoning outbreaks in Shijiazhuang City, and the staphylococcal enterotoxin (SE) types of the S. aureus isolates from food poisoning. A total of 138 foodborne S. aureus isolates were distributed into 8 clonal complexes (CCs) and 12 singletons. CC1, CC5, CC8, CC15, CC97, CC59, CC398, CC88, and CC7 were the predominant CCs of foodborne S. aureus isolates. Moreover, CC59, CC15, and CC5 were the most prevalent CCs in food poisoning outbreaks. SEE was the most commonly detected SE in food poisoning isolates. One hundred thirty-three S. aureus isolates harbored the penicillin-resistant gene blaZ, and nine isolates carried the mec gene. The present study further explained the relationship between S. aureus and foods and food poisoning and indicated the potential risk of S. aureus infection.

The genetic feature and virulence determinant of highly virulent community-associated MRSA ST338-SCCmec Vb in China

ST59 is the predominant pathotype of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in China. As a variant of ST59, there is relatively little known about the detailed information of ST338. To address this issue, here, we described thirteen ST338 CA-MRSA strains isolated from severe bloodstream infection cases, and focused on their epidemiology, genetic features and virulence potential. Phylogenetic analysis showed the earliest isolated strain of this study is likely a predecessor of recent ST338 lineage (after year of 2014). Furthermore, the phylogenetic reconstruction and time estimation suggested that ST338 evolved from ST59 in 1991. Notably, the carrying patten of virulence factors of all ST338 strains were similar, and the genomic islands νSaα, νSaγ and SaPI and the core virulence factors like hla and psm were detected in ST338 isolates. However, all ST338 isolates lacked some adhesion factors such as clfA, clfB, eap, cna and icaD. Additionally, among these ST338 strains, one PVL-negative ST338 isolate was detected. Experiment on mice nose and human alveolar epithelial cell showed that the nasal colonization ability of ST338 was weaker than that of CA-MRSA MW2. In a mouse bloodstream infection model and skin infection model, PVL+ and PVL− strains had the similar virulence, which was dependent on upregulation of toxin genes rather than the presence of mobile genetic elements such as ΦSa2 carrying PVL. Our findings provide important insight into the epidemiology and pathogenicity of the novel and highly virulent ST338-SCCmec Vb clone.

Exploring the possible targeting strategies of liposomes against methicillin-resistant Staphylococcus aureus (MRSA)

Multi antibiotic-resistant bacterial infections are on the rise due to the overuse of antibiotics. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the pathogens listed under the category of serious threats where vancomycin remains the mainstay treatment despite the availability of various antibacterial agents. Recently, decreased susceptibility to vancomycin from clinical isolates of MRSA has been reported and has drawn worldwide attention as it is often difficult to overcome and leads to increased medical costs, mortality, and longer hospital stays. Development of antibiotic delivery systems is often necessary to improve bioavailability and biodistribution, in order to reduce antibiotic resistance and increase the lifespan of antibiotics. Liposome entrapment has been used as a method to allow higher drug dosing apart from reducing toxicity associated with drugs. The surface of the liposomes can also be designed and enhanced with drug-release properties, active targeting, and stealth effects to prevent recognition by the mononuclear phagocyte system, thus enhancing its circulation time. The present review aimed to highlight the possible targeting strategies of liposomes against MRSA bacteremia systemically while investigating the magnitude of this effect on the minimum inhibitory concentration level.

Design, synthesis and antibacterial evaluation of ocotillol derivatives with polycyclic nitrogen-containing groups

Aim: With the increasing abuse of antibacterial drugs, multidrug-resistant bacteria have become a burden on human health and the healthcare system. To find alternative compounds effective against hospital-acquired methicillin-resistant Staphylococcus aureus (HA-MRSA), novel derivatives of ocotillol were synthesized. Methods & Results: Ocotillol derivatives with polycyclic nitrogen-containing groups were synthesized and evaluated for in vitro antibacterial activity. Compounds 36-39 exhibited potent antibacterial activity against HA-MRSA, with MIC = 8-64 μg/ml. Additionally, a combination of compound 37 and the commercially available antibiotic kanamycin showed synergistic inhibitory effects, with a fractional inhibitory concentration index of ≤0.375. Conclusion: Compound 37 has a strong inhibitory effect, and this derivative has potential for use as a pharmacological tool to explore antibacterial mechanisms.

Constellation of methicillin-resistant genomic islands (SCCmec) among nasal meticillin-resistant Staphylococcus aureus isolates

The apprehensiveness for the knowledge vacuum on existential threat of nasal carriage of pvl+ healthcare-acquired meticillin-resistant Staphylococcus aureus (HA-MRSA) strains amongst subjects in hospitals have led us to pursue a grasp on the constellation of staphylococcal cassette chromosome mec (SCCmec) types and pvl gene among mecA positive MRSA nasal strains. This was accomplished by phenotypic (catalase, coagulase, Microgen staph ID, ORSAB) and genotypic (polymerase chain reaction) biotyping techniques. All the mecA+ strains harboured the SCCmec gene; SCCmec type I prevailed in 43.75% and pvl was found in 42.1% of the isolates. Dual carriage of mecA and pvl genes occurred in six (37.5%, n = 6/16) strains. Overall, majority of the mecA+ MRSA strains documented in this study carried SCCmec elements of the HA genotype with a hint of community-acquired (CA)genotype suggesting a possible coexistence of both HA-MRSA and community-acquiredhealthcare-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) strains. Consequently, the implementation of methodical surveillance is needed for the evaluation of potential shifts in directionality of (HA-MRSA/CA-MRSA) pvl+ MRSA clones in our hospitals for effective and prudent antimicrobial stewardship.

T Cell Immunity and the Quest for Protective Vaccines against Staphylococcus aureus Infection

Staphylococcus aureus is a wide-spread human pathogen, and one of the top causative agents of nosocomial infections. The prevalence of antibiotic-resistant S. aureus strains, which are associated with higher mortality and morbidity rates than antibiotic-susceptible strains, is increasing around the world. Vaccination would be an effective preventive measure against S. aureus infection, but to date, every vaccine developed has failed in clinical trials, despite inducing robust antibody responses. These results suggest that induction of humoral immunity does not suffice to confer protection against the infection. Evidence from studies in murine models and in patients with immune defects support a role of T cell-mediated immunity in protective responses against S. aureus. Here, we review the current understanding of the mechanisms underlying adaptive immunity to S. aureus infections and discuss these findings in light of the recent S. aureus vaccine trial failures. We make the case for the need to develop anti-S. aureus vaccines that can specifically elicit robust and durable protective memory T cell subsets.

Exploring Virulence Factors and Alternative Therapies against Staphylococcus aureus Pneumonia

Pneumonia is an acute pulmonary infection associated with high mortality and an immense financial burden on healthcare systems. Staphylococcus aureus is an opportunistic pathogen capable of inducing S. aureus pneumonia (SAP), with some lineages also showing multidrug resistance. Given the high level of antibiotic resistance, much research has been focused on targeting S. aureus virulence factors, including toxins and biofilm-associated proteins, in an attempt to develop effective SAP therapeutics. Despite several promising leads, many hurdles still remain for S. aureus vaccine research. Here, we review the state-of-the-art SAP therapeutics, highlight their pitfalls, and discuss alternative approaches of potential significance and future perspectives.

Resistance profile to antimicrobials agents in methicillin-resistant Staphylococcus aureus isolated from hospitals in South Brazil between 2014-2019

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) is a common pathogen causing healthcare-associated infections. Owing to the restricted use of beta-lactams in MRSA infections, non-beta-lactam antimicrobials are required for treatment. However, MRSA can develop resistance mechanisms to non-beta-lactam antimicrobials, which reduces viable treatment options. Here, we evaluated the antimicrobial susceptibility and resistance genes of MRSA isolated from hospitalized patients in South Brazil.

METHODS

The antimicrobial susceptibilities of hospital MRSA (217) isolates were determined by disk diffusion or microdilution methods. Additionally, the presence of 14 resistance genes and SCCmec typing was performed by PCR.

RESULTS

Among the antimicrobials tested, we observed high erythromycin (74.2%), ciprofloxacin (64.5%), and clindamycin (46.1%) resistance rates and complete susceptibility to linezolid and vancomycin. Seventeen different patterns of MRSA antimicrobial resistance were observed, of which 42.9% represented multidrug resistance. Among erythromycin-resistant MRSA, 53.4%, 45.3%, 37.9%, 13.0%, and 6.8% carried ermA, msrA, msrB, ermC, and ermB genes, respectively. Among clindamycin-resistant MRSA, 83%, 17%, 10%, 4%, and 2% carried ermA, ermC, ermB, linA, and linB genes, respectively. Among gentamicin-resistant MRSA, 96.8%, 83.9%, and 9.7% carried aac(6')/aph(2''), aph(3')-IIIa, and ant(4')-Ia genes, respectively. Among tetracycline-resistant MRSA, 6.5% and 93.5% carried tetK and tetM genes, respectively. Lastly, among trimethoprim/sulfamethoxazole-resistant MRSA, 13.3% and 100% carried dfrA and dfrG genes, respectively. The SCCmec type IV isolates were detected more frequently, whereas the SCCmec type III isolates exhibited higher multidrug resistance.

CONCLUSIONS

The study data provides information regarding the MRSA resistance profile in South Brazil that is associated with the clinical conditions of patients and can contribute to clinical decision-making.

Prevalence of fosfomycin resistance and gene mutations in clinical isolates of methicillin-resistant Staphylococcus aureus

Background

Fosfomycin exhibits excellent in vitro activity against multidrug-resistant pathogens, including methicillin-resistant Staphylococcus aureus (MRSA). Increasing fosfomycin resistance among clinical MRSA isolates was reported previously, but little is known about the relative abundance of Fosfomycin resistance genes in MRSA isolates circulating in Taiwan.

Methods

All MRSA isolates, collected in 2002 and 2012 by the Taiwan Surveillance of Antimicrobial Resistance (TSAR) program, were used in this study. Susceptibility to various antimicrobial agents, including fosfomycin, was determined by broth microdilution. Genetic determinants of fosfomycin resistance, including fosB carriage and murA, glpT and uhpT mutations, were investigated using PCR and sequencing of amplicons. Staphylococcal protein A (spa) typing was also performed to determine the genetic relatedness of MRSA isolates.

Results

A total of 969 MRSA strains, 495 in the year 2002 and 474 in the year 2012, were analyzed. The overall in vitro susceptibility was 8.2% to erythromycin, 18.0% to clindamycin, 29.0% to tetracycline, 44.6% to ciprofloxacin, 57.5% to trimethoprim/sulfamethoxazole, 86.9% to rifampicin, 92.9% to fosfomycin and 100% to linezolid and vancomycin. A significant increase in the fosfomycin resistance rate was observed from 3.4% in 2002 to 11.0% in 2012. Of 68 fosfomycin-resistant MRSA isolates, several genetic backgrounds probably contributing to fosfomycin resistance were identified. Twelve isolates harbored the fosB gene, and various mutations in murA, uhpT, and glpT genes were noted in 11, 59, and 66 isolates, respectively. The most prevalent gene mutations were found in the combination of uhpT and glpT genes (58 isolates). The vast majority of the fosfomycin-resistant MRSA isolates belonged to spa type t002.

Conclusions

An increased fosfomycin resistance rate of MRSA isolates was observed in our present study, mostly due to mutations in the glpT and uhpT genes. Clonal spread probably contributed to the increased fosfomycin resistance.

Molecular analysis of methicillin-resistant Staphylococcus aureus isolates from four teaching hospitals in Iran: the emergence of novel MRSA clones

Background

The global spread of methicillin-resistant Staphylococcus aureus (MRSA) infections necessitates the use of validated methods for the identification and typing of this bacterium. This study aimed to determine the distribution of main molecular types of MRSA strain circulating among hospitalized patients in teaching hospitals in Isfahan and Kashan.

Methods

A total of 146 Staphylococcus aureus strains were isolated from patients in four teaching hospitals in Isfahan and Kashan during June 2017 to September 2018. The antimicrobial resistance patterns of Staphylococcus aureus strains were performed by disc diffusion method. The MRSA strains were identified phenotypically and confirmed by PCR assay. The prevalence of microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) genes among MRSA strains was evaluated by multiplex PCR. The genotypes of MRSA strains were determined by multilocus sequence typing and SCCmec typing.

Results

Of 146 Staphylococcus aureus isolates, 24 (16.4%) isolates were identified as MRSA strains. According to antimicrobial susceptibility testing the highest resistance rates were seen for tetracycline, erythromycin, ciprofloxacin and gentamicin. All of Staphylococcus aureus isolates were susceptible to vancomycin whereas 3 (2.1%) isolates were resistant to linezolid. Three different SCCmec types were obtained among MRSA strains including 16 (66.7%) SCCmec type V, 3 (12.5%) SCCmec type III and 5 (20.8%) SCCmec type II. Of 24 MRSA isolates 20 (83.3%) carried MSCRAMMs genes including eno (70.8%), fib (54.1%), cna (25.0%), fnbB (16.6%), ebps 5 (20.8%), and the fnbA, bbp and clfA genes were not detected in any MRSA isolate. MLST analysis revealed 11 sequence types among MRSA isolates as follows: ST239, ST291, ST22, ST861, ST889, ST8, ST59, ST343, ST772, ST6 and ST1465. Also seven MLST-based clonal complexes (CCs) were identified among MRSA strains including: CC8, CC7, CC398, CC59, CC22, CC1 and CC5.

Conclusions

A relatively high diversity was found in MRSA genotypes in Kashan and Isfahan hospitals, and seven clonal complexes were identified. Pandemic MRSA clones including CC8 and CC22 were the most prevalent clones and the novel ST types including ST1465, ST861, ST 889 and ST772 are reported for the first time in Iran in the present study. In addition the high prevalence of MSCRAMMs genes in MRSA isolates demonstrates the high potential of these strains for pathogenicity.

Understanding the Fight Against Resistance: Hospital-Acquired Methicillin-Resistant Staphylococcus Aureus vs. Community-Acquired Methicillin-Resistant Staphylococcus Aureus

Since the identification of Staphylococcus (S.) aureus, penicillin was exclusively used to combat its disastrous toxic effects. Shortly thereafter, resistant strains arose, which were no longer susceptible to penicillin or methicillin treatments. These strands were later identified as methicillin-resistant Staphylococcus aureus (MRSA). Two particular MRSA strands that are discussed below are the hospital-acquired methicillin-resistant Staphylococcus aureus (HA-MRSA) strands and the community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strands. Despite arising from a single bacterium, S. aureus, each of these two strands possesses quite different resistance and virulence factors. These differences contribute to the type of population in which they affect, their ability to resist traditional treatment approaches, and their overall morbidity and mortality rates. We explore these differences by reviewing several review articles published on various reputable scientific online databases. Findings include sources from studies conducted in the United States, China, Nepal, and Uganda, ranging from 2006 to 2019. These resistance and virulence factors, the Staphylococcal cassette cartridge mecA resistance gene (SCCmec) and the Panton-Valentine Leukocidin toxin gene (PVL), were identified and isolated in each of these studies in order to appreciate similarities and differences in how they impact human beings.

Eleucanainones A and B: Two Dimeric Structures from the Bulbs of Eleutherine americana with Anti-MRSA Activity

Two naphthoquinone-derived heterodimers with unprecedented carbon skeletons, eleucanainones A (1) and B (2), were isolated from the bulbs of Eleutherine americana. Their structures were elucidated by comprehensive spectroscopic methods. The structures of 1 and 2 were determined to be the first examples of dibenzofuran- and naphthalenone-containing naphthoquinone dimers. Compound 1 exhibited significant anti-MRSA activity in vitro with minimum inhibitory concentration (MIC) values of 0.78 μg/mL by downregulation of basal expression of agrA, cidA, icaA and sarA in methicillin-resistant S. aureus (MRSA).

Rare presentation of sepsis caused by necrotizing scalp infection

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is a rising cause of skin and soft tissue infections over the last decade with potentially serious complications. In this article, we describe a case of a large scalp and post-auricular abscess complicated by bacteremia. This is a case of a 73-year-old female who presented with altered mental status was found to have two fluctuant scalp abscesses, bacteremia with necrosis. The patient was promptly treated with intravenous antibiotics, multiple operative debridements without calvarial periosteum involvement defects requiring split-thickness skin grafts for wound closure. This case highlights the severity of a CA-MRSA skin infection in an atypical location.

Molecular characterization of methicillin-resistant Staphylococcus aureus clinical strains from the endotracheal tubes of patients with nosocomial pneumonia

BACKGROUND

Among all cases of nosocomial pneumonia, Staphylococcus aureus is the second most prevalent pathogen (17.8%). In Europe, 29.9% of the isolates are oxacillin-resistant. The changing epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) nosocomial infections and the decreasing susceptibility to first-line antibiotics leave clinicians with few therapeutic options. The objective of our study was to determine the antimicrobial susceptibility, the associated molecular mechanisms of resistance and the epidemiological relatedness of MRSA strains isolated from the endotracheal tubes (ETT) of intubated critically ill patients in the intensive care unit (ICU) with nosocomial pneumonia caused by Staphylococcus aureus.

METHODS

The antimicrobial susceptibility to vancomycin, linezolid, ciprofloxacin, clindamycin, erythromycin, chloramphenicol, fusidic acid, gentamicin, quinupristin-dalfopristin, rifampicin, sulfamethoxazole/trimethoprim, and tetracycline were measured. Resistance mechanisms were then analyzed by polymerase chain reaction and sequencing. Molecular epidemiology was carried out by multi-locus sequence typing.

RESULTS

S. aureus isolates were resistant to ciprofloxacin, erythromycin, gentamicin, tetracycline, clindamycin, and fusidic acid. The most frequent mutations in quinolone-resistant S. aureus strains were S84L in the gyrA gene, V511A in the gyrB gene, S144P in the grlA gene, and K401R/E in the grlB gene. Strains resistant to erythromycin carried the ermC, ermA, and msrA genes; the same ermC and ermA genes were detected in strains resistant to clindamycin. The aac(6')-aph(2″) gene was related to gentamicin resistance, while resistance to tetracycline was related to tetK (efflux pump). The fusB gene was detected in the strain resistant to fusidic acid. The most frequent sequence types were ST22, ST8, and ST217, which were distributed in four clonal complexes (CC5, CC22, CC45, and CC59).

CONCLUSIONS

High levels of resistance to second-line antimicrobials threatens the treatment of nosocomial respiratory infections due to methicillin-resistant S. aureus with decreased susceptibility to linezolid and vancomycin. The wide genotypic diversity found reinforces the central role of ICU infection control in preventing nosocomial transmission.

Molecular Characterization of Methicillin- Resistant Staphylococcus aureus in a Tertiary Care hospital in Kuwait

Methicillin-resistant Staphylococcus aureus (MRSA) are a major cause of healthcare and community- associated infections due to their ability to express a variety of virulence factors. We investigated 209 MRSA isolates obtained from 1 January to 31 December 2016 using a combination of phenotypic and genotypic methods to understand the genetic backgrounds of MRSA strains obtained in a General hospital in Kuwait. Antibiotics susceptibility was performed with disk diffusion, and MIC was measured with Etest strips. Molecular typing was performed using SCCmec typing, spa typing, and DNA microarray for antibiotic resistance and virulence genes. The isolates were susceptible to vancomycin, teicoplanin, rifampicin, ceftaroline, and linezolid but were resistant to gentamicin, tetracycline, erythromycin, fusidic acid, chloramphenicol and ciprofloxacin. Molecular typing revealed six SCCmec types, 56 spa types and 16 clonal complexes (CC). The common SCCmec types were type IV (39.5%), type III (34.4%), type V (25.8%) and type VI (3.8%). The dominant spa types were t860 (23.9%), t945 (8.6%), t127 (6.7%), t688 (6.7%), t304 (6.2) and t044 (5.7%). The other spa types occurred sporadically. Genes for PVL was detected in 59 (28.2%) of the isolates. CC8-ST239-MRSA-III + SCCmer (23.3%) was the most prevalent clone, followed by CC6-MRSA-IV (8.3%), CC80-MRSA-IV [PVL+] (5.8%), CC5-MRSA-VI + SCCfus (5.0%), CC30-MRSA-IV[PVL+] (4.1%), CC1-MRSA-V + SCCfus [PVL+] (4.1%), CC5-MRSA-V + SCCfus (4.1%) and CC22-MRSA-IV[PVL+] (4.1%). The study revealed that despite the emergence of MRSA with diverse genetic backgrounds over the years, ST239-MRSA-III remained the dominant clone in the hospital. This warrants reassessment of infection prevention and control procedures at this hospital.

Characterization of a community-acquired methicillin-resistant sequence type 338 Staphylococcus aureus strain containing a staphylococcal cassette chromosome mec type VT

OBJECTIVES

To determine the molecular characteristics of a sequence type 338 community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strain and the relationship among MRSA strains from various lineages and areas.

METHODS

Whole-genome sequencing, genomic comparison, antimicrobial susceptibility testing, and hemolysis analysis were performed to identify the resistance determinants and virulence factors of strain ZY05 and the relationships among CC59 clones.

RESULTS

MRSA strain ZY05 was resistant to tetracycline, erythromycin, and clindamycin, and the resistance genes erm(B) and tet(K) were detected in the genome. ZY05 harbors the genomic islands νSaα, νSaβ, νSaγ, and ΦSa2, the pathogenicity island νSa1, and virulence factors such as Panton-Valentine leukocidin, phenol-soluble modulins, alpha-hemolysin, enterotoxin B, enterotoxin K, and enterotoxin Q, which are the same as those present in ST59 strains. In addition, the virulence potential of ST338 did not differ from that of ST59. This strain contains the staphylococcal cassette chromosome mec (SCCmec) type V_T, a distinct SCCmec type previously reported from Taiwan. The results of core genome multilocus sequence typing (cgMLST) analysis showed that the gene distances between ST59 and ST338 were close among CC59 isolates, while strains from Taiwan were identical to isolates from the Chinese mainland with respect to these two sequence types.

CONCLUSIONS

The ST338 strain ZY05, which has a close genetic relationship to ST59 strains, is multidrug-resistant and highly virulent. Strains of two identical lineages, ST59 and ST338, from Taiwan and the Chinese mainland may have the same genetic background.

Molecular characteristics and virulence gene profiles of Staphylococcus aureus isolates in Hainan, China

Background

There have been no reports regarding the molecular characteristics, virulence features, and antibiotic resistance profiles of Staphylococcus aureus (S. aureus) from Hainan, the southernmost province of China.

Methods

Two hundred twenty-seven S. aureus isolates, consisting of 76 methicillin-resistant S. aureus (MRSA) and 151 methicillin-susceptible S. aureus (MSSA), were collected in 2013–2014 and 2018–2019 in Hainan, and investigated for their molecular characteristics, virulence genes, antibiotic resistance profiles and main antibiotic resistance genes.

Results

Forty sequence types (STs) including three new STs (ST5489, ST5492 and ST5493), and 79 Staphylococcal protein A (spa) types were identified based on multilocus sequence typing (MLST) and spa typing, respectively. ST398 (14.1%, 32/227) was found to be the most prevalent, and the prevalence of ST398-MSSA increased significantly from 2013 to 2014 (5.5%, 5/91) to 2018–2019 (18.4%, 25/136). Seventy-six MRSA isolates were subject to staphylococcus chromosomal cassette mec (SCCmec) typing. SCCmec-IVa was the predominant SCCmec type, and specifically, ST45-SCCmec IVa, an infrequent type in mainland China, was predominant in S. aureus from Hainan. The antibiotic resistance profiles and antibiotic resistance genes of S. aureus show distinctive features in Hainan. The resistant rates of the MRSA isolates to a variety of antibiotics were significantly higher than those of the MSSA isolates. The predominant erythromycin and tetracycline resistance genes were ermC (90.1%, 100/111) and tetK (91.8%, 78/85), respectively. Eleven virulence genes, including the Panton-Valentine leukocidin (pvl) and eta, were determined, and the frequency of eta and pvl were found to be 57.3 and 47.6%. Such high prevalence has never been seen in mainland China before.

Conclusion

S. aureus isolates in Hainan have unique molecular characteristics, virulence gene and antibiotic resistance profiles, and main antibiotic resistance genes which may be associated with the special geographical location of Hainan and local trends in antibiotic use.

Molecular typing revealed the emergence of pvl-positive sequence type 22 methicillin-susceptible Staphylococcus aureus in Urumqi, Northwestern China

Background

Staphylococcus aureus is among the most common causes of health care- and community-associated infections worldwide. The distributions of different S. aureus clones change over time and also vary geographically. The purpose of this study was to determine the molecular type and antimicrobial resistance profiles of clinical S. aureus strains isolated in Urumqi, Northwestern China.

Methods

A total of 605 clinical S. aureus isolates were collected from Xinjiang Military General Hospital, in Urumqi. Protein A-encoding (spa) typing, multilocus sequence typing, staphylococcal chromosomal cassette mec typing, Panton-Valentine leucocidin (pvl) gene detection, and antimicrobial resistance profiling were performed.

Results

Among these strains, 271 isolates (44.7%) were methicillin-resistant S. aureus (MRSA) and 334 (55.3%) were methicillin-susceptible S. aureus (MSSA). The MRSA strains consisted of 22 spa types and 14 sequence types (STs). ST239-MRSA-III-t030 (73.1%, 198/271) and ST59-MRSA-IV-t437 (11.8%, 32/271) were the most common, and ST22-MRSA-IV-t309 was the rarest (2.02%, 6/271). The MSSA strains consisted of 93 spa types and 29 STs. ST22, ST121, ST398, ST5, ST7, ST188, and ST15 were the main MSSA STs, and ST22-MSSA-t309 was most common (26.0%, 87/334). The pvl gene was present in 20.3% of all S.aureus strains, and 80.8% (88/99) of ST22-MSSA strains harbored the pvl gene. A total of 85.7% pvl-positive ST22-MSSA strains were spa t309 (85/99), and 87.5% of pvl-positive ST22-MSSA strains were from abscesses or wounds (skin and soft tissue infections). All ST239-MRSA strains were resistant to gentamicin (GEN), levofloxacin (LEV), ciprofloxacin (CIP), moxifloxacin (MXF), rifampicin (RIF), and tetracycline (TET). Among the ST59-MRSA strains, over 70.0% were resistant to erythromycin (ERY), clindamycin (CLI), and TET. ST22-MSSA remained susceptible to most antibiotics, but was resistant to PEN (97.0%), ERY (57.6%), and CLI (15.2%).

Conclusion

Our major results indicated that the antimicrobial resistance profiles and pvl genes of S. aureus isolates from Urumqi were closely associated with clonal lineage. ST239-MRSA-III-t030 and pvl-positive ST22-MSSA-t309 were the most common clones in this region of Northwestern China.