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

Host and antibiotic jointly select for greater virulence in Staphylococcus aureus

Widespread antibiotic usage has resulted in the rapid evolution of drug-resistant bacterial pathogens and poses significant threats to public health. Resolving how pathogens respond to antibiotics under different contexts is critical for understanding disease emergence and evolution going forward. The impact of antibiotics has been demonstrated most directly through in vitro pathogen passaging experiments. Independent from antibiotic selection, interactions with hosts have also altered the evolutionary trajectories and fitness landscapes of pathogens, shaping infectious disease outcomes. However, it is unclear how interactions between hosts and antibiotics impact the evolution of pathogen virulence. Here, we evolved and re-sequenced Staphylococcus aureus, a major bacterial pathogen, varying exposure to host and antibiotics to tease apart the contributions of these selective pressures on pathogen adaptation. After 12 passages, S. aureus evolving in Caenorhabditis elegans nematodes exposed to a sub-minimum inhibitory concentration of antibiotic (oxacillin) became highly virulent, regardless of whether the ancestral pathogen was methicillin-resistant (MRSA) or methicillin-sensitive (MSSA). Host and antibiotic exposure selected for reduced drug susceptibility in MSSA lineages while increasing MRSA total growth outside hosts. We identified mutations in genes involved in complex regulatory networks linking virulence and metabolism, including codY , agr , and gdpP , suggesting that rapid adaptation to infect hosts may have pleiotropic effects. In particular, MSSA populations under selection from host and antibiotic accumulated mutations in the global regulator gene codY , which controls biofilm formation in S. aureus. These populations had indeed evolved more robust biofilms-a trait linked to both virulence and antibiotic resistance-suggesting evolution of one trait can confer multiple adaptive benefits. Despite evolving in similar environments, MRSA and MSSA populations proceeded on divergent evolutionary paths, with MSSA populations exhibiting more similarities across replicate populations. Our results underscore the importance of considering multiple and concurrent selective pressures as drivers of pervasive pathogen traits.

Methicillin-resistant Staphylococcus aureus prevalence in food-producing animals and food products in Saudi Arabia: A review

In Saudi Arabia, the occurrence of methicillin-resistant Staphylococcus aureus (MRSA) in food and livestock represents a major public health hazard. The emergence of livestock-associated MRSA has heightened the risk of human infection with comparable virulence traits. The lack of information about MRSA transmission in our region hinders accurate risk assessment, despite its detection in food animals and retail foods. Adopting a One Health approach is essential for effectively combating MRSA in Saudi Arabia. This method unites actions in the human, animal, and environmental spheres. To combat MRSA contamination, surveillance measures need strengthening; interdisciplinary collaboration among healthcare professionals, veterinarians, and environmental scientists is crucial, and targeted interventions must be implemented in local food chains and animal populations. Through a holistic strategy, public health and sustainable food production in the region are protected. This review aims to improve public health interventions by increasing understanding of MRSA prevalence and related risks in local food chains and animal populations.

Time-calibrated phylogenetic and chromosomal mobilome analyses of Staphylococcus aureus CC398 reveal geographical and host-related evolution

An international collection of Staphylococcus aureus of clonal complex (CC) 398 from diverse hosts spanning all continents and a 30 year-period is studied based on whole-genome sequencing (WGS) data. The collection consists of publicly available genomic data from 2994 strains and 134 recently sequenced Swiss methicillin-resistant S. aureus (MRSA) CC398 strains. A time-calibrated phylogeny reveals the presence of distinct phylogroups present in Asia, North and South America and Europe. European MRSA diverged from methicillin-susceptible S. aureus (MSSA) at the beginning of the 1950s. Two major European phylogroups (EP4 and EP5), which diverged approximately 1974, are the main drivers of MRSA CC398 spread in Europe. Within EP5, an emergent MRSA lineage spreading among the European horse population (EP5-Leq) diverged approximately 1996 from the pig lineage (EP5-Lpg), and also contains human-related strains. EP5-Leq is characterized by staphylococcal cassette chromosome mec (SCCmec) IVa and spa type t011 (CC398-IVa-t011), and EP5-Lpg by CC398-SCCmecVc-t011. The lineage-specific antibiotic resistance and virulence gene patterns are mostly mediated by the acquisition of mobile genetic elements like SCCmec, S. aureus Genomic Islands (SaGIs), prophages and transposons. Different combinations of virulence factors are present on S. aureus pathogenicity islands (SaPIs), and novel antimicrobial resistance gene containing elements are associated with certain lineages expanding in Europe. This WGS-based analysis reveals the actual evolutionary trajectory and epidemiological trend of the international MRSA CC398 population considering host, temporal, geographical and molecular factors. It provides a baseline for global WGS-based One-Health studies of adaptive evolution of MRSA CC398 as well as for local outbreak investigations.

Genome mining of Lactiplantibacillus plantarum PA21: insights into its antimicrobial potential

BACKGROUND

The dramatic increase of antimicrobial resistance in the healthcare realm has become inexorably linked to the abuse of antibiotics over the years. Therefore, this study seeks to identify potential postbiotic metabolites derived from lactic acid bacteria such as Lactiplantibacillus plantarum that could exhibit antimicrobial properties against multi-drug resistant pathogens.

RESULTS

In the present work, the genome sequence of Lactiplantibacillus plantarum PA21 consisting of three contigs was assembled to a size of 3,218,706 bp. Phylogenomic analysis and average nucleotide identity (ANI) revealed L. plantarum PA21 is closely related to genomes isolated from diverse niches such as dairy products, food, and animals. Genome mining through the BAGEL4 and antiSMASH database revealed four bacteriocins in a single cluster and four regions of biosynthetic gene clusters responsible for the production of bioactive compounds. The potential probiotic genes indirectly responsible for postbiotic metabolites production were also identified. Additionally, in vitro studies showed that the L. plantarum PA21 cell-free supernatant exhibited antimicrobial activity against all nine methicillin-resistant Staphylococcus aureus (MRSA) and three out of 13 Klebsiella pneumoniae clinical isolates tested.

CONCLUSION

Results in this study demonstrates that L. plantarum PA21 postbiotic metabolites is a prolific source of antimicrobials against multi-drug resistant pathogens with potential antimicrobial properties.

Preparation and characterization of spiked gold nanobipyramids and its antibacterial effect on methicillin-resistant Staphylococcus aureus and methicillin-sensitive Staphylococcus aureus

BACKGROUND

This paper reports the preparation of a new family of spiked gold nanoparticles, spiked gold nanobipyramids (SNBPs). This protocol includes the process to synthesize gold nanobipyramids (NBPs) using combined seed-mediated and microwave-assisted method and procedure to form spikes on whole surface of gold nanobipyramid. We also evaluated the antibacterial activity against both methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) in various concentrations of SNBPs and NBPs by well diffusion assay, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) determination. The effect of SNBPs on exposed bacteria was observed by scanning electron microscopy.

RESULTS

The UV-Vis of purified NBPs exhibited two absorption bands located at 550 nm and 849 nm with yield of bipyramidal particles more than 90%. The average size of NBPs was 76.33 ± 10.11 nm in length and 26.57 ± 2.25 nm in diameter, respectively, while SNBPs were prolongated in length and achieved 182.37 ± 21.74 nm with multi-branches protruding whole surface areas. In antibacterial evaluations, SNBPs and NBPs showed antibacterial activity with MIC of 6.25 μl/ml and 12.5 μl/ml, respectively, for MSSA while 12.5 μl/ml and 25 μl/ml, respectively, for MRSA. Besides, MBC values of SNBPs and NBPs were found to be 12.5 μl/ml and 25 μl/ml, respectively, against MSSA while 25 μl/ml and 50 μl/ml, respectively, against MRSA. Furthermore, scanning electron microscopy observation showed the mechanism that SNBPs damaged the outer membrane, released cytoplasm, and altered the normal morphology of MRSA and MSSA, leading to bacterial death.

CONCLUSIONS

This report suggests that these SNBPs are potential antibacterial agents that can be applied as antibacterial materials to inhibit the growth of human bacterial pathogen infections related to antibiotic-resistant bacteria.

A review of new emerging livestock-associated methicillin-resistant Staphylococcus aureus from pig farms

Methicillin-resistant Staphylococcus aureus (MRSA) is a S. aureus strain resistant to β-lactam antibiotics and is often associated with livestock, known as livestock-associated (LA)-MRSA. Using molecular typing with multi-locus sequence typing, MRSA clones have been classified in pigs, including clonal complex 398. Livestock-associated-methicillin-resistant S. aureus was first discovered in pigs in the Netherlands in 2005. Since then, it has been widely detected in pigs in other countries. Livestock-associated-methicillin-resistant S. aureus can be transmitted from pigs to pigs, pigs to humans (zoonosis), and humans to humans. This transmission is enabled by several risk factors involved in the pig trade, including the use of antibiotics and zinc, the size and type of the herd, and the pig pen management system. Although LA-MRSA has little impact on the pigs' health, it can be transmitted from pig to pig or from pig to human. This is a serious concern as people in direct contact with pigs are highly predisposed to acquiring LA-MRSA infection. The measures to control LA-MRSA spread in pig farms include conducting periodic LA-MRSA screening tests on pigs and avoiding certain antibiotics in pigs. This study aimed to review the emerging LA-MRSA strains in pig farms.

Molecular Epidemiology of Community-Acquired Methicillin-Resistant Staphylococcus aureus and Clinical Characteristics of Different Sites of Infection

Purpose

Since community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) was recognized, the molecular epidemiology of CA-MRSA in China has been diverse. It is unclear whether different sites of CA-MRSA infection differ in antimicrobial resistance and clinical characteristics. The purpose of this study was to identify the molecular types, virulence factors and antimicrobial resistance of CA-MRSA strains and to analyze the clinical characteristics of different sites of CA-MRSA infection.

Methods

26 CA-MRSA strains were screened from Beijing Chao-Yang Hospital from 2014 to 2022. SCCmec type, MLST type, spa type, Panton-Valentine leukocidin (PVL), hemolysin α (Hla), phenolic soluble regulatory protein α (PSMα), toxic shock syndrome toxin-1 (TSST-1), and enterotoxin (SE) A to E were detected by PCR and gene sequencing. Antimicrobial susceptibility tests and the clinical features of CA-MRSA infection cases were collected for statistical analysis.

Results

The predominant type of CA-MRSA was ST59-t437-IV. New non-epidemic types, SCCmec VII, were also found. PVL was seen in 65.4% of CA-MRSA strains and TSST-1 was only be detected in 3.8% of CA-MRSA strain which caused poor prognosis. There were three types of infections: pneumonia (61.5%), infective endocarditis (7.7%), and skin and soft tissue infections (SSTIs) (30.8%). CA-MRSA pneumonia cases were secondary to influenza infection (37.5%). Patients with CA-MRSA-associated infective endocarditis were more likely to have underlying cardiac diseases. Patients with CA-MRSA-associated SSTIs were more likely to have a history of diabetes mellitus, and strains in this group were more susceptible to erythromycin and clindamycin.

Conclusion

ST59-t437-IV was the primary CA-MRSA type in our research and in China. We proposed that TSST-1 might be one of the indicators to predict the severity and prognosis of CA-MRSA infection. Different sites of CA-MRSA infection had difference in antibiotics susceptibility testing and underlying diseases of patients. It could provide a new perspective on treating different types of CA-MRSA infection.

Molecular characterization and virulence gene profiling of methicillin-resistant Staphylococcus aureus associated with bloodstream infections in southern China

Methicillin-resistant Staphylococcus aureus (MRSA) causes an enormous illness burden, including skin and soft tissue infections (SSTIs), pneumonia, bloodstream infections (BSI), and sepsis. BSI are associated with significant patient morbidity and mortality worldwide. However, limited information is available on MRSA-related BSI in China. This study aimed to investigate the molecular characterization of 77 MRSA isolates recovered from hospitalized patients with BSI between 2012 and 2020 at three first-class tertiary hospitals in southern China based on multilocus sequence typing (MLST), spa typing, and staphylococcal cassette chromosome mec (SCCmec) typing. Overall, 13 clonal complexes (CCs) were identified, with CC59 and CC5 being the largest clusters, indicating high genetic diversity among BSI-causing MRSA isolates. ST59 was the most prevalent MLST type (22.1%). ST5/ST764-MRSA SCCmec II was the predominant adult MRSA clone, whereas ST59-MRSA SCCmec IV was the most common pediatric MRSA clone. ST5-t2460, ST764-t1084, and ST59-t437 were the most common types of adult MRSA isolates, whereas ST59-t437 and ST59-t172 were the predominant types of children’s MRSA isolates. ST59-SCCmec IV/V represented the most common clone among community acquired-MRSA isolates. ST5/ST764-SCCmec II was the most common type of hospital-associated MRSA isolate. The most prevalent toxin-encoding genes detected were hla, hld, icaA, and clfA (96.1–100%). Forty-three (100%, 43/43) isolates harbored more than 18 of the tested virulence genes in adults and eight virulence genes (23.5%, 8/34) in children. Virulence gene analysis revealed diversity among different clones: the positivity rates for the Panton-Valentine leukocidin (PVL) gene were 55.8 and 35.3% in adult and pediatric MRSA isolates, respectively; the genes seb–sei were present in all adult strains; seb–seg–sei–seo were present in all ST5, ST59, ST15, ST45, and ST22 adult strains; and seg–sei–sem–sen–seo were present in different clones, including ST15, ST45, and ST22 adult MRSA isolates and ST25, ST30, ST546, and ST72 children’s MRSA isolates. Adult MRSA isolates had significantly higher antibiotic resistance rates and virulence gene prevalence than pediatric MRSA isolates. For 8 years, this study provided epidemiological data on the molecular characteristics and virulence genes in different groups of MRSA BSI in China. Our findings may provide critical information for a better understanding of MRSA BSI.

Molecular Characterization of Staphylococcus aureus Strains Isolated from Mobile Phones

The widespread use of mobile phones (MP) among healthcare personnel might be considered as an important source of contamination. One of the most pathogenic bacteria to humans is Staphylococcus aureus, which can be transmitted through the constant use of MP. Nevertheless, which specific type of strains are transmitted and which are their sources have not been sufficiently studied. The aim of this study is to determine the source of contamination of MP and characterize the corresponding genotypic and phenotypic properties of the strains found. Nose, pharynx, and MP samples were taken from a group of health science students. We were able to determinate the clonality of the isolated strains by pulsed-field gel electrophoresis (PFGE) and spa gene typing (spa-type). Adhesin and toxin genes were detected, and the capacity of biofilm formation was determined. Several of the MP exhibited strains of S. aureus present in the nose and/or pharynx of their owners. methicillin-susceptible Staphylococcus aureus (MSSA), hospital-acquired methicillin-resistant S. aureus (HA-MRSA), and community-acquired methicillin-resistant S. aureus (CA-MRSA) strains were found, which indicated a variety of genotypes. This study concludes that MP can be contaminated with the strains of S. aureus present in the nose and/or pharynx of the owners; these strains can be of different types and there is no dominant genotype.

Frequency and Molecular Characterization of Staphylococcus aureus from Placenta of Mothers with Term and Preterm Deliveries

Globally, prematurity is the leading cause of neonatal mortality (babies in the first four weeks of life) and now the second leading cause of mortality after pneumonia in children under age five. The neonatal gut microbial colonization is crucial in the human life cycle. Placental microbiota transmits from the gut microbiota plays a significant role in association with kinship. Simultaneously, this transition is being made from mother to infant. This comparative study explored the diversity of microbiota associated with term and preterm neonates by evaluating the placental samples. The study found that 16/68 (23.5%) full-term placental samples were positive for S. aureus; on the other hand, 4/16 (25%) preterm placental samples confirmed culture growth for S. aureus. Antimicrobial susceptibility patterns showed that Staphylococcusaureus (S. aureus) isolates from both types of samples were resistant to Ofloxacin, Trimethoprim-sulfamethoxazole, Oxacillin, and Cefoxitin. However, Methicillin-Resistant Staphylococcus aureus (MRSA) detection was 43.75% in full-term and 75% in preterm placental samples. Moreover, two isolates were positive for both mecA and PVL virulent genes, and the rest were positive only for the mecA gene. Interestingly few isolates lacked both characteristic MRSA genes, mecA and PVL. Notably, resistances were more inclined towards preterm samples for antimicrobial susceptibility and MRSA screening. It may be concluded that there is a significant presence of S. aureus in the placenta of mothers with term and preterm deliveries which might be responsible for preterm deliveries. Therefore, judicious use of antibiotics during pregnancies may help prevent preterm births.

Graphene-based fluorometric determination of agrD gene transcription in methicillin-resistant Staphylococcus aureus using exonuclease III-aided target recycling and DNA walker cascade amplification

A graphene-based bioassay is described for the fluorometric determination of agrD gene transcription (mRNA) in methicillin-resistant Staphylococcus aureus (MRSA). This method includes exonuclease III (Exo III)-assisted target recycling and DNA walker cascade amplification. Hairpin1 (HP1) consists of a capture probe (CP) and DNA walker sequence. In the absence of the target, 5'-amino modified hairpin2 (HP2) labeled with carboxyfluorescein (FAM) at its 3' terminus is covalently linked to graphene via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide (EDC/NHS) catalysis, resulting in the quenching of the FAM signal. The stem-loop structure of HP1 opens when the target is added to form partially complementary DNA/RNA hybrids. Exo III then initiates the target recycling process by cleaving the CP and DNA walker cascade reaction by automatic walking. This iterative reaction causes the FAM to dissociate from the graphene, and the fluorescence can be measured at excitation/emission wavelengths of 480/514 nm. Therefore, the target can be assayed by fluorescence. This method has a linear relationship with the concentration of target within the range 1 fM to 100 pM with a detection limit of 1 fM. The developed bioassay was used to monitor biofilm formation and investigate the mechanism of drug action with satisfactory results. Schematic representation of the graphene-based fluorescent bioassay for agrD gene transcription in methicillin-resistant Staphylococcus aureus by using exonuclease III-aided target recycling and DNA walker cascade amplification.