Prevalence of virulent and biofilm forming ST88-IV-t2526 methicillin-resistant Staphylococcus aureus clones circulating in local retail fish markets in Assam, India

Genomic portraits of methicillin-resistant staphylococci (MRS) from food fish unveiled the genes associated with staphylococcal food poisoning (SFP), virulence and antimicrobial resistance

BACKGROUND

Characteristics of non-clinical strains of methicillin-resistant Staphylococcus aureus (MRSA) especially from fishery environment are poorly understood. This research, in addition to comprehensive characterisation, sought to delineate the genetic relatedness between the MRSA strains originating from clinical as well as non-clinical settings. Out of 39 methicillin-resistant staphylococcal isolates from 197 fish samples, 6 (Three each of methicillin-resistant S. haemolyticus (MRSH) and MRSA) with distinct resistance profiles were selected for whole-genome sequencing. Using respective bioinformatics tools, MRSA genomes were comprehensively characterized for resistome, virulomes, molecular epidemiology and phylogenetic analysis. Simultaneously, MRSH genomes were specifically examined to characterize antimicrobial resistance genes (ARGs), owing to the fact that MRSH is often recognized as a reservoir for resistance determinants.

RESULTS

Three MRSA clones identified in this study include ST672-IVd/t13599 (sequence type-SCCmec type/spa type), ST88-V/t2526, and ST672-IVa/t1309. Though, the isolates were phenotypically vancomycin-sensitive, five of the six genomes carried vancomycin resistance genes including the VanT (VanG cluster) or VanY (VanM cluster). Among the three MRSA, only one harbored the gene encoding Panton-Valentine Leukocidin (PVL) toxin, while staphylococcal enterotoxin (SEs) genes such as sea and seb, associated with staphylococcal food poisoning were identified in two other MRSA. Genomes of MRSH carried a composite of type V staphylococcal cassette chromosome mec (SCCmec) elements (5C2 & 5). This finding may be explained by the inversion and recombination events that may facilitate the integration of type V elements to the SCC elements of S. aureus with a methicillin-susceptible phenotype. Phylogenetically, MRSA from a non-clinical setting displayed a considerable relatedness to that from clinical settings.

CONCLUSION

This study highlights the genetic diversity and resistance profiles of MRSA and MRSH, with non-clinical MRSA showing notable relatedness to clinical strains. Future research should explore resistance gene transfer mechanisms and environmental reservoirs to better manage MRSA spread.

Methicillin-Resistant Staphylococcus aureus (MRSA) in Different Food Groups and Drinking Water

Methicillin-resistant Staphylococcus aureus (MRSA) has been included by the World Health Organization in its list of "priority pathogens" because of its widespread prevalence and the severity of the infections it causes. The role of food in infections caused by MRSA is unknown, although strains of this microorganism have been detected in various items for human consumption. In order to gain an overview of any possible role of food in MRSA infections, a review was undertaken of studies published between January 2001 and February 2024 relating to MRSA. These comprised research that focused on fish and shellfish, eggs and egg products, foods of vegetable origin, other foodstuffs (e.g., honey or edible insects), and drinking water. In most of these investigations, no prior enrichment was carried out when isolating strains. Three principal methods were used to confirm the presence of MRSA, namely amplification of the mecA gene by PCR, amplification of the mecA and the mecC genes by PCR, and disc diffusion techniques testing susceptibility to cefoxitin (30 μg) and oxacillin (1 μg). The great diversity of methods used for the determination of MRSA in foods and water makes comparison between these research works difficult. The prevalence of MRSA varied according to the food type considered, ranging between 0.0% and 100% (average 11.7 ± 20.3%) for fish and shellfish samples, between 0.0% and 11.0% (average 1.2 ± 3.5%) for egg and egg products, between 0.0% and 20.8% (average 2.5 ± 6.8%) for foods of vegetable origin, between 0.6% and 29.5% (average 28.2 ± 30.3%) for other foodstuffs, and between 0.0% and 36.7% (average 17.0 ± 14.0%) for drinking water.

Nasal carriage of Staphylococcus aureus in healthy dairy cows in Algeria: antibiotic resistance, enterotoxin genes and biofilm formation

BACKGROUND

Staphylococcus aureus can colonize and infect a variety of animal species. In dairy herds, it is one of the leading causes of mastitis cases. The objective of this study was to characterize the S. aureus isolates recovered from nasal swabs of 249 healthy cows and 21 breeders of 21 dairy farms located in two provinces of Algeria (Tizi Ouzou and Bouira).

METHODS

The detection of enterotoxin genes was investigated by multiplex PCRs. Resistance of recovered isolates to 8 antimicrobial agents was determined by disc-diffusion method. The slime production and biofilm formation of S. aureus isolates were assessed using congo-red agar (CRA) and microtiter-plate assay. Molecular characterization of selected isolates was carried out by spa-typing and Multi-Locus-Sequence-Typing (MLST).

RESULTS

S. aureus was detected in 30/249 (12%) and 6/13 (28.6%) of nasal swabs in cows and breeders, respectively, and a total of 72 isolates were recovered from positive samples (59 isolates from cows and 13 from breeders). Twenty-six of these isolates (36.1%) harbored genes encoding for staphylococcal enterotoxins, including 17/59 (28.8%) isolates from cows and 9/13 (69.2%) from breeders. Moreover, 49.1% and 92.3% of isolates from cows and breeders, respectively, showed penicillin resistance. All isolates were considered as methicillin-susceptible (MSSA). Forty-five (76.3%) of the isolates from cows were slime producers and 52 (88.1%) of them had the ability to form biofilm in microtiter plates. Evidence of a possible zoonotic transmission was observed in two farms, since S. aureus isolates recovered in these farms from cows and breeders belonged to the same clonal lineage (CC15-ST15-t084 or CC30-ST34-t2228).

CONCLUSIONS

Although healthy cows in this study did not harbor methicillin-resistant S. aureus isolates, the nares of healthy cows could be a reservoir of enterotoxigenic and biofilm producing isolates which could have implications in human and animal health.

The CRISPR/Cas system as an antimicrobial resistance strategy in aquatic ecosystems

With the growing population, demand for food has dramatically increased, and fisheries, including aquaculture, are expected to play an essential role in sustaining demand with adequate quantities of protein and essential vitamin supplements, employment generation, and GDP growth. Unfortunately, the incidence of emerging/re-emerging AMR pathogens annually occurs because of anthropogenic activities and the frequent use of antibiotics in aquaculture. These AMR pathogens include the WHO's top 6 prioritized ESKAPE pathogens (nosocomial pathogens: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.), extended-spectrum beta lactases (ESBLs) and carbapenemase-producing E. coli, which pose major challenges to the biomagnification of both nonnative and native antibiotic-resistant bacteria in capture and cultured fishes. Although implementing the rational use of antibiotics represents a promising mitigation measure, this approach is practically impossible due to the lack of awareness among farmers about the interplay between antimicrobial use and the emergence of antimicrobial resistance (AMR). Nevertheless, to eradicate these 'superbugs,' CRISPR/Cas (clustered regularly interspersed short palindromic repeats/CRISPR associate protein) has turned out to be a novel approach owing to its ability to perform precise site-directed targeting/knockdown/reversal of specific antimicrobial resistance genes in vitro and to distinguish AMR-resistant bacteria from a plethora of commensal aquatic bacteria. Along with highlighting the importance of virulent multidrug resistance genes in bacteria, this article aims to provide a holistic picture of CRISPR/Cas9-mediated genome editing for combating antimicrobial-resistant bacteria isolated from various aquaculture and marine systems, as well as insights into different types of CRISPR/Cas systems, delivery methods, and challenges associated with developing CRISPR/Cas9 antimicrobial agents.

Phenotypic and Genotypic Characterization of Staphylococcus aureus Isolated from Nasal Samples of Healthy Dairy Goats in Algeria

The present study aimed to determine the phenotypic and genotypic characteristics of S. aureus isolates from the nasal swabs of goats. A total of 232 nasal samples (one per animal) were collected from goats on 13 farms located in two regions of Algeria and were analyzed for the presence of S. aureus. The detection of virulence factors was carried out using PCR. The antibiotic susceptibility of the recovered isolates was assessed using the disc diffusion method. The biofilm formation ability was assessed by the Congo red agar method and a microtiter plate assay, and the molecular characterization of isolates was carried out by spa-typing, and for selected isolates also by multilocus sequence typing (MLST). Overall, 36 out of 232 nasal swabs (15.5%) contained S. aureus, and 62 isolates were recovered. Regarding the virulence factors, at least one staphylococcal enterotoxin gene was detected in 30 (48.4%) isolates. The gene tst encoding the toxic shock syndrome toxin was detected in fifteen isolates (24.2%), but none of the isolates harbored the gene of Panton-Valentine leukocidin (lukF/S-PV). Nine different spa-types were identified, including the detection of a new one (t21230). The recovered isolates were assigned to three clonal complexes, with CC5 (51.8%) being the most common lineage. Two isolates were methicillin-resistant (MRSA) and belonged to ST5 (CC5) and to spa-types t450 and t688. Moreover, 27 (43.5%) of the S. aureus isolates were found to be slime producers in Congo red agar, and all of the recovered isolates could produce biofilms in the microtiter plate assay. Our study showed that the nares of healthy goats could be a reservoir of toxigenic and antibiotic-resistant strains of S. aureus isolates, including MRSA, which could have implications for public health.

Bioactive Analysis of Antibacterial Efficacy and Antioxidant Potential of Aloe barbadensis Miller Leaf Extracts and Exploration of Secondary Metabolites Using GC-MS Profiling

Aloe barbadensis Miller (ABM) is a traditional medicinal plant all over the world. Numerous studies were conducted to exhibit its medicinal properties and most of them were concentrated on its metabolites against human pathogens. The current research work evaluates the attributes of different polar-based extracts (ethanol, methanol, ethyl acetate, acetone, hexane, and petroleum ether) of dried Aloe barbadensis leaf (ABL) to investigate its phytochemical constituents, antioxidant potential (DPPH, ABTS), phenolic, tannin, flavonoid contents, identification of bioactive compounds, and functional groups by gas chromatography-mass spectrometry (GC-MS) and fourier transform infrared spectroscopy (FT-IR) respectively, and comparing antibacterial efficacy against human pathogens, aquatic bacterial pathogens, and zoonotic bacteria associated with fish and human. The present results showed that the methanolic extract of ABL showed higher antioxidant activity (DPPH-59.73 ± 2.01%; ABTS-74.1 ± 1.29%), total phenolic (10.660 ± 1.242 mg GAE/g), tannin (7.158 ± 0.668 mg TAE/g), and flavonoid content (49.545 ± 1.928 µg QE/g) than that of other solvent extracts. Non-polar solvents hexane and petroleum ether exhibited lesser activity among the extracts. In the case of antibacterial activity, higher inhibition zone was recorded in methanol extract of ABL (25.00 ± 0.70 mm) against Aeromonas salmonicida. Variations in antibacterial activity were observed depending on solvents and extracts. In the current study, polar solvents revealed higher antibacterial activity when compared to the non-polar and the mid-polar solvents. Diverse crucial bioactive compounds were detected in GC-MS analysis. The vital compounds were hexadecanoic acid (30.69%) and 2-pentanone, 4-hydroxy-4-methyl (23.77%) which are responsible for higher antioxidant and antibacterial activity. Similar functional groups were identified in all the solvent extracts of ABL with slight variations in the FT-IR analysis. Polar-based solvent extraction influenced the elution of phytocompounds more than that of the other solvents used in this study. The obtained results suggested that the ABM could be an excellent source for antioxidant and antibacterial activities and can also serve as a potential source of effective bioactive compounds to combat human as well as aquatic pathogens.

Collaterally Sensitive β-Lactam Drugs as an Effective Therapy against the Pre-Existing Methicillin Resistant Staphylococcus aureus (MRSA) Biofilms

Methicillin-resistant Staphylococcus aureus (MRSA) is among the leading causes of nosocomial infections and forms biofilms, which are difficult to eradicate because of their increasing resistance to antimicrobial agents. This is especially true for pre-existing biofilms. The current study focused on evaluating the efficacy of three β-lactam drugs, meropenem, piperacillin, and tazobactam, alone and in combination against the MRSA biofilms. When used individually, none of the drugs exhibited significant antibacterial activity against MRSA in a planktonic state. At the same time, the combination of meropenem, piperacillin, and tazobactam showed a 41.7 and 41.3% reduction in planktonic bacterial cell growth, respectively. These drugs were further assessed for biofilm inhibition and removal. The combination of meropenem, piperacillin, and tazobactam caused 44.3% biofilm inhibition, while the rest of the combinations did not show any significant effects. Results also revealed that piperacillin and tazobactam exhibited the best synergy against the pre-formed biofilm of MRSA, with 46% removal. However, adding meropenem to the piperacillin and tazobactam combination showed a slightly reduced activity towards the pre-formed biofilm of MRSA and removed 38.7% of it. Although the mechanism of synergism is not fully understood, our findings suggest that these three β-lactam drugs can be used in combination as very effective therapeutic agents for the treatment of pre-existing MRSA biofilms. The in vivo experiments on the antibiofilm activity of these drugs will pave the way for applying such synergistic combinations to clinics.

Evaluation of Phytochemical Screening, Pigment Content, In Vitro Antioxidant, Antibacterial Potential and GC-MS Metabolite Profiling of Green Seaweed Caulerpa racemosa

Exploration of seaweeds to unravel their bioactive metabolites from the perspective of wider applications gained substantial importance. The present study was performed to investigate the total phenolic, flavonoid, tannin content, antioxidant activity and antibacterial potential of various solvent extracts of green seaweed Caulerpa racemosa. The methanolic extract showed higher phenolic (11.99 ± 0.48 mg gallic acid equivalents/g), tannin (18.59 ± 0.54 mg tannic acid equivalents/g) and flavonoid (33.17 ± 0.76 mg quercetin equivalents/g) content than other extracts. Antioxidant activity was determined by using 2,2-diphenylpicrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay with different concentrations of C. racemosa extracts. The methanolic extract showed higher scavenging potential in both the DPPH and ABTS activity with the inhibition value of 54.21 ± 1.39% and 76.62 ± 1.08%, respectively. Bioactive profiling was also identified by using Gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared (FT-IR) techniques. These studies revealed the presence of valuable bioactive compounds in C. racemosa extracts and these compounds might be responsible for antimicrobial, antioxidant, anticancer and anti-mutagenic properties. Major compounds identified in GC-MS were 3,7,11,15-Tetramethyl-2-hexadecen-1-ol, 3-hexadecene and Phthalic acid. In terms of antibacterial activity, C. racemosa has promising antibacterial potential against aquatic pathogens Aeromonas hydrophila, Aeromonas veronii and Aeromonas salmonicida. Further evaluation studies focusing aquatic related aspects would reveal the novel bioproperties and applications of C. racemosa.

Genotypes and phenotypes of methicillin-resistant staphylococci isolated from shrimp aquaculture farms

The population of methicillin-resistant (MR) staphylococci in aquatic environment is rarely investigated. Here, we characterized a collection of MR staphylococci recovered from shrimp aquaculture farms (n = 37) in Kerala, India. A total of 261 samples yielded 47 MR isolates (16 S. aureus, 13 S. haemolyticus, 11 S. epidermidis, 3 S. saprophytics and 2 each of S.intermedius and S. kloosii). Multi-drug resistance was evident in 72.3% of the isolates, with resistance mainly towards erythromycin (78.7%), norfloxacin and trimethoprim-sulfamethoxazole (53.2%), and gentamicin (34%). Major resistance genes identified included mecA (100%), ermC (38.3%), aacA-aphD (21.3%), tetK (14.9%) and tetM (21.3%). Almost 60% of the isolates carried type V SCCmec (Staphylococcal Cassette Chromosome mec), and the remaining harboured untypeable SCCmec elements. Comprehensive genotyping of the methicillin-resistant Staphylococcus aureus isolates revealed high prevalence of ST772-t345-V (sequence type-spa type-SCCmec type) (75%), followed by minor representations of ST6657-t345-V and ST3190-t12353. The isolates of S. haemolyticus and S. epidermidis were genotypically diverse as shown by their pulsed-field gel electrophoresis (PFGE) profiles. Genes encoding staphylococcal enterotoxins were observed in 53.2% of the isolates. Various genes involved in adhesion and biofilm formation were also identified. In conclusion, our findings provide evidence that shrimp aquaculture settings can act as reservoirs of methicillin-resistant staphylococci.

Surveillance and prevalence of antimicrobial resistant bacteria from public settings within urban built environments: Challenges and opportunities for hygiene and infection control

Antimicrobial resistant (AMR) bacteria present one of the biggest threats to public health; this must not be forgotten while global attention is focussed on the COVID-19 pandemic. Resistant bacteria have been demonstrated to be transmittable to humans in many different environments, including public settings in urban built environments where high-density human activity can be found, including public transport, sports arenas and schools. However, in comparison to healthcare settings and agriculture, there is very little surveillance of AMR in the built environment outside of healthcare settings and wastewater. In this review, we analyse the existing literature to aid our understanding of what surveillance has been conducted within different public settings and identify what this tells us about the prevalence of AMR. We highlight the challenges that have been reported; and make recommendations for future studies that will help to fill knowledge gaps present in the literature.

Virulence and intermediate resistance to high-end antibiotic (teicoplanin) among coagulase-negative staphylococci sourced from retail market fish

This study reports the distribution of enterotoxigenic determinants among staphylococci and the susceptibility of staphylococci to various classes of antibiotics. We observed all the isolates as resistant to beta-lactam antibiotics and a few as resistant to non-beta-lactam antibiotics such as clindamycin (47.4%), erythromycin (44.7%), gentamicin (23.7%), norfloxacin (34.2%), tetracycline (26.3%), trimethoprim-sulfamethoxazole (15.8%) etc. The resistance of S. sciuri (n = 1) and S. haemolyticus (n = 1) to rifampicin and intermediate resistance of S. gallinarum (n = 2) to teicoplanin, a high-end antibiotic, are also observed in this study. The multidrug-resistance (≥ 3 classes of antibiotics) was recorded in 23 (60.5%) isolates. The virulomes such as sea, seb, seg and sei were identified predominantly in S. haemolyticus. Surprisingly, certain isolates which were phenotypically confirmed as biofilm-producers by Congo red agar (CRA) test did not harbor biofilm-associated loci. This implies the protein-mediated mechanism of biofilm formation as an alternative to polysaccharide intercellular adhesin (PIA) in staphylococci. However, icaAD locus which encodes PIA was identified in 10 (26.3%) isolates and the eno locus, encoding elastin-binding protein which can accelerate the biofilm production, is identified in all the isolates. The possession of type V SCCmec elements by the S. haemolyticus (15.8%) raised the concern about the rapid dissemination of mecA gene to other species of staphylococci including the virulent S. aureus. In short, this study acknowledges the toxigenicity of coagulase-negative staphylococci (CoNS). Through this study, surveillance of antimicrobial resistance and transference of virulomes in staphylococci is warranted.