A bacteriocin-based treatment option for Staphylococcus haemolyticus biofilms

Genomic analysis of multi-drug resistant coagulase-negative staphylococci from healthy humans and animals revealed unusual mechanisms of resistance and CRISPR-Cas system

BACKGROUND

Coagulase-negative staphylococci (CoNS) are evolving as major reservoirs and vectors of unusual and critical antimicrobial resistance (AMR) mechanisms.

MATERIALS AND METHODS

In this study, the genomic characterization of 26 multidrug-resistant (MDR)-CoNS (S. borealis, S. saprophyticus, S. sciuri, S. hominis, S. epidermidis, S. pasteuri, S. hyicus, S. simulans, S. haemolyticus, and S. arlettae) previously obtained from the nasal cavity of healthy nestling storks, humans who had no contact with animals, pigs, and pig farmers, as well as dogs and dog owners from Spain was performed. High-quality draft genomes obtained by Illumina sequencing technology were used to determine their resistome, virulome, mobile genetic elements, and CRISPR-Cas types. The relatedness of three CoNS species with publicly available genomes was assessed by core-genome single nucleotide polymorphisms (SNPs).

RESULTS

AMR genes to all classes of antibiotics in staphylococci were detected including unusual ones (mecC, ermT, and cfr), of which their corresponding genetic organizations were analyzed. About 96.1% of the MDR-CoNS strains harbored diverse adherence or immune evasion genes. Remarkably, one enterotoxin-C and -L-carrying S. epidermidis-ST595 strain from a nestling stork was detected. Moreover, various plasmid bound-biocide resistance genes (qacACGJ) were identified in 34.6% of the MDR-CoNS. Two genes that encode for cadmium and zinc resistance (cadD, czrC) were found, of which czrC predominated (42.3%). Complete CRISPR-Cas system was detected in 19.2% of the CoNS strains, of which cas-1, -2, and -9 predominated, especially in 75% of the S. borealis strains. The phylogenetic analysis identified clusters of related S. epidermidis lineages with those of other countries (SNP < 100). Also, highly related S. borealis isolates (SNP < 10) from pigs was confirmed for the first time in Spain.

CONCLUSION

These findings showed that various ecological niches harbor CoNS that presented MDR phenotypes mediated by multiple AMR genes carried by mobile genetic elements with relatively low frequency of intact CRISPR-Cas systems. Furthermore, the transmission of some CoNS species in humans and animals is strongly suggested.

Exploring staphylococcus in urinary tract infections: A systematic review and meta-analysis on the epidemiology, antibiotic resistance and biofilm formation

This study aimed to determine the epidemiology, biofilm formation and antibiotic resistance of staphylococci collected worldwide in the context of UTIs. This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Forty studies from 23 countries were selected for quantitative review. Electronic databases (PubMed, Scopus, Google Scholar, and Web of Sciences) were searched for articles published between 2010 and 2024 on the epidemiology, biofilm formation, and antibiotic resistance of uropathogenic staphylococci. Strict inclusion and exclusion standards were applied during the review of the articles. Forty articles were included in this systematic review. The prevalence of uropathogenic staphylococci varies from country to country, with the pooled prevalence of S. aureus and coagulase-negative staphylococci (CoNS) being 8.71 % (95 %CI: 6.145-11.69) and 13.17 % (95 %CI: 8.08-19.27) respectively. Among CoNS isolates, S. epidermidis was the most common with 19.3 % (95 %CI: 5.88-38.05). The prevalence of methicillin-resistant S. aureus isolates increased significantly from 23 % in 2010-2015 to 47 % in 2021-2024 (p = 0.03). S. haemolyticus is the most antibiotic-resistant species in CoNS, with 45 % of isolates resistant to methicillin, 33 % to gentamicin, and 29 % to tetracycline. Eighty-eight S. aureus strains were biofilm producers, including 35 % moderate biofilm producers and 48 % strong biofilm producers. The combined frequencies of icaA, clfA and fnbpA were 100, 99, and 89 %, respectively. The development of antibiotic resistance and biofilm formation by staphylococci involved in UTIs explains the need for periodic regional surveillance of these infections, which poses a serious public health problem.

Design of Novel Saposin-like Bacteriocins Using a Hybrid Approach

A multitude of approaches will be required to respond to the threat posed by the emergence and spread of antibiotic resistant pathogens. Bacteriocins have gained increasing attention as a possible alternative to antibiotics, as such peptide antimicrobials have mechanisms of action different from antibiotics and are therefore equally potent against antibiotic resistant bacteria as their susceptible counterparts. A group of bacteriocins known as saposin-like bacteriocins is believed to act directly on the bacterial membrane. Based on seven saposin-like leaderless bacteriocins, we have constructed a library of hybrid peptides containing all combinations of the N- and C-terminal halves of the native bacteriocins. All hybrid peptides were synthesized using in vitro protein expression and assayed for antimicrobial activity towards several pathogens. Of the 42 hybrid peptides, antimicrobial activity was confirmed for 11 novel hybrid peptides. Furthermore, several of the hybrid peptides exhibited altered antimicrobial spectra and apparent increase in potency compared to the peptides from which they were derived. The most promising hybrid, termed ISP26, was then obtained synthetically and shown to inhibit most of the Gram-positive species tested, including opportunistic pathogens and food spoilage bacteria. Additionally, ISP26 was shown to inhibit Acinetobacter, a species of Gram-negative bacteria frequently isolated from nosocomial infections. The activity of the hybrid library provides valuable insights into the design and screening of new active bacteriocins.

Staphylococcus haemolyticus: An updated review on nosocomial infections, antimicrobial resistance, virulence, genetic traits, and strategies for combating this emerging opportunistic pathogen

Staphylococcus haemolyticus, a key species of the Staphylococcus genus, holds significant importance in healthcare-associated infections, due to its notable resistance to antimicrobials, like methicillin, and proficient biofilms-forming capabilities. This coagulase-negative bacterium poses a substantial challenge in the battle against nosocomial infections. Recent research has shed light on Staph. haemolyticus genomic plasticity, unveiling genetic elements responsible for antibiotic resistance and their widespread dissemination within the genus. This review presents an updated and comprehensive overview of the clinical significance and prevalence of Staph. haemolyticus, underscores its zoonotic potential and relevance in the one health framework, explores crucial virulence factors, and examines genetics features contributing to its success in causing emergent and challenging infections. Additionally, we scrutinize ongoing studies aimed at controlling spread and alternative approaches for combating it.

Tertiary Plasticity Drives the Efficiency of Enterocin 7B Interactions with Lipid Membranes

The ability of antimicrobial peptides to efficiently kill their bacterial targets depends on the efficiency of their binding to the microbial membrane. In the case of enterocins, there is a three-part interaction: initial binding, unpacking of helices on the membrane surface, and permeation of the lipid bilayer. Helical unpacking is driven by disruption of the peptide hydrophobic core when in contact with membranes. Enterocin 7B is a leaderless enterocin antimicrobial peptide produced from Enterococcus faecalis that functions alone, or with its cognate partner enterocin 7A, to efficiently kill a wide variety of Gram-stain positive bacteria. To better characterize the role that tertiary structural plasticity plays in the ability of enterocin 7B to interact with the membranes, a series of arginine single-site mutants were constructed that destabilize the hydrophobic core to varying degrees. A series of experimental measures of structure, stability, and function, including CD spectra, far UV CD melting profiles, minimal inhibitory concentrations analysis, and release kinetics of calcein, show that decreased stabilization of the hydrophobic core is correlated with increased efficiency of a peptide to permeate membranes and in killing bacteria. Finally, using the computational technique of adaptive steered molecular dynamics, we found that the atomistic/energetic landscape of peptide mechanical unfolding leads to free energy differences between the wild type and its mutants, whose trends correlate well with our experiment.

In-silico genomic characterization of Staphylococcus haemolyticus on a global scale: lineages, resistome, and virulome

BACKGROUND

Staphylococcus haemolyticus belongs to the Coagulase-Negative Staphylococci (CoNS), exhibiting the highest levels of antibiotic resistance within this group of bacteria. This species has been increasingly implicated in nosocomial and animal infections worldwide, with a prevalence of methicillin-resistant Staphylococcus haemolyticus (MRSH). Most information about this organism comes from regional analyzes or with the absence of typing data, thus not revealing the real role of S. haemolyticus strains in world public health.

METHODS

Here, we performed an enhanced global epidemiological analysis considering all available S. haemolyticus genomes from all continents, including genomes of nosocomial, environmental, and animal origin (n = 310). Furthermore, we added original genomic information from a clinical MRSH from the Brazilian Amazon region. The resistome and virulome of the genomes were associated with their mobilome, being inferred based on the presence of specific genes and databases such as CARD, VFDB, and PlasmidFinder, respectively.

RESULTS

Phylogenetic analysis revealed three main groups, the main one covering most of the clinical clonal complex 3 (CC3) genomes in the world. The virulome of some genomes in this cluster showed the complete capsule operon (capA-capM). Importantly, this virulome trait could be associated with the mobilome, since the capsule operon, as well as a whole set of genes of the type VII secretion system, were observed in plasmids. In addition, the resistome of the main cluster (CC3) was larger, characterized mainly by the presence of the mecA gene, in addition to a set of other genes (aad, aac-aph, aph, erm), contrasting with the poor resistome of the other two clusters. Several insertion sequences were identified, some of them linked to specific clusters, and resistance genes, such as the rare cfrA (IS257).

CONCLUSIONS

Therefore, successful lineages of CC3 S. haemolyticus causing human infections are widespread worldwide, raising concern about the impact of this scenario on public health.

Artemisia brevifolia Wall. Ex DC Enhances Cefixime Susceptibility by Reforming Antimicrobial Resistance

(1) Background: A possible solution to antimicrobial resistance (AMR) is synergism with plants like Artemisia brevifolia Wall. ex DC. (2) Methods: Phytochemical quantification of extracts (n-hexane (NH), ethyl acetate (EA), methanol (M), and aqueous (Aq)) was performed using RP-HPLC and chromogenic assays. Extracts were screened against resistant clinical isolates via disc diffusion, broth dilution, the checkerboard method, time-kill, and protein quantification assays. (3) Results: M extract had the maximum phenolic (15.98 ± 0.1 μg GAE/mgE) and flavonoid contents (9.93 ± 0.5 μg QE/mgE). RP-HPLC displayed the maximum polyphenols in the M extract. Secondary metabolite determination showed M extract to have the highest glycosides, alkaloids, and tannins. Preliminary resistance profiling indicated that selected isolates were resistant to cefixime (MIC 20-40 µg/mL). Extracts showed moderate antibacterial activity (MIC 60-100 µg/mL). The checkerboard method revealed a total synergy between EA extract and cefixime with 10-fold reductions in cefixime dose against resistant P. aeruginosa and MRSA. Moreover, A. brevifolia extracts potentiated the antibacterial effect of cefixime after 6 and 9 h. The synergistic combination was non- to slightly hemolytic and could inhibit bacterial protein in addition to cefixime disrupting the cell wall, thus making it difficult for bacteria to survive. (4) Conclusion: A. brevifolia in combination with cefixime has the potential to inhibit AMR.

Prevalence of antimicrobial resistance in a full-scale drinking water treatment plant

Antibiotic resistance in drinking water has received increasing attention in recent years. In this study, the occurrence and abundance of antibiotic resistance genes (ARGs) in a drinking water treatment plant (DWTP) was comprehensively investigated using metagenomics. Bioinformatics analysis showed that 381 ARG subtypes belonging to 15 ARG types were detected, and bacitracin had the highest abundance (from 0.26 × 10-2 to 0.86 copies/cell), followed by multidrug (from 0.57 × 10-1 to 0.47 copies/cell) and sulfonamide (from 0.83 × 10-2 to 0.35 copies/cell). Additionally, 933 ARG-carrying contigs (ACCs) were obtained from the metagenomic data, among which 153 contigs were annotated as pathogens. The most abundant putative ARG host was Staphylococcus (7.9%), which most frequently carried multidrug ARGs (43.2%). Additionally, 38 high-quality metagenome-assembled genomes (MAGs) were recovered, one of which was identified as Staphylococcus aureus (Bin.624) and harboured the largest number of ARGs (n = 16). Using the cultivation technique, 60 isolates were obtained from DWTP samples, and Staphylococcus spp. (n = 11) were found to be dominant in all isolates, followed by Bacillus spp. (n = 17). Antimicrobial susceptibility testing showed that most Staphylococcus spp. were multidrug resistant (MDR). These results deepen our understanding of the distribution profiles of ARGs and antibiotic resistant bacteria (ARB) in DWTPs for potential health risk evaluation. Our study also highlights the need for new and efficient water purification technologies that can be introduced and applied in DWTPs.

Lactiplantibacillus plantarum as a novel platform for production and purification of integral membrane proteins using RseP as the benchmark

The present study describes a detailed procedure for expressing and purifying the integral membrane protein RseP using the pSIP system and Lactiplantibacillus plantarum as an expression host. RseP is a membrane-bound site-2-protease and a known antibacterial target in multiple human pathogens. In the present study, we screened five RseP orthologs from Gram-positive bacteria and found RseP from Enterococcus faecium (EfmRseP) to yield the highest protein levels. The production conditions were optimized and EfmRseP was purified by immobilized metal ion affinity chromatography followed by size-exclusion chromatography. The purification resulted in an overall yield of approximately 1 mg of pure protein per 3 g of wet-weight cell pellet. The structural integrity of the purified protein was confirmed using circular dichroism. We further assessed the expression and purification of RseP from E. faecium in the Gram-negative Escherichia coli. Detection of soluble protein failed in two of the three E. coli strains tested. Purification of EfmRseP expressed in E. coli C43(DE3) resulted in a protein with lower purity compared to EfmRseP expressed in L. plantarum. To our knowledge, this is the first time L. plantarum and the pSIP expression system have been applied for the production of membrane proteins.

Flow cytometric detection of vancomycin-resistant Enterococcus faecium in urine using fluorescently labelled enterocin K1

A urinary tract infection (UTI) occurs when bacteria enter and multiply in the urinary system. The infection is most often caused by enteric bacteria that normally live in the gut, which include Enterococcus faecium. Without antibiotic treatment, UTIs can progress to life-threatening septic shock. Early diagnosis and identification of the pathogen will reduce antibiotic use and improve patient outcomes. In this work, we develop and optimize a cost-effective and rapid (< 40 min) method for detecting E. faecium in urine. The method uses a fluorescently labelled bacteriocin enterocin K1 (FITC-EntK1) that binds specifically to E. faecium and is then detected using a conventional flow cytometer. Using this detection assay, urine containing E. faecium was identified by an increase in the fluorescent signals by 25-73-fold (median fluorescence intensity) compared to control samples containing Escherichia coli or Staphylococcus aureus. The method presented in this work is a proof of concept showing the potential of bacteriocins to act as specific probes for the detection of specific bacteria, such as pathogens, in biological samples.

The role of site-2-proteases in bacteria: a review on physiology, virulence, and therapeutic potential

Site-2-proteases are a class of intramembrane proteases involved in regulated intramembrane proteolysis. Regulated intramembrane proteolysis is a highly conserved signaling mechanism that commonly involves sequential digestion of an anti-sigma factor by a site-1- and site-2-protease in response to external stimuli, resulting in an adaptive transcriptional response. Variation of this signaling cascade continues to emerge as the role of site-2-proteases in bacteria continues to be explored. Site-2-proteases are highly conserved among bacteria and play a key role in multiple processes, including iron uptake, stress response, and pheromone production. Additionally, an increasing number of site-2-proteases have been found to play a pivotal role in the virulence properties of multiple human pathogens, such as alginate production in Pseudomonas aeruginosa, toxin production in Vibrio cholerae, resistance to lysozyme in enterococci and antimicrobials in several Bacillus spp, and cell-envelope lipid composition in Mycobacterium tuberculosis. The prominent role of site-2-proteases in bacterial pathogenicity highlights the potential of site-2-proteases as novel targets for therapeutic intervention. In this review, we summarize the role of site-2-proteases in bacterial physiology and virulence, as well as evaluate the therapeutic potential of site-2-proteases.

The extracellular domain of site-2-metalloprotease RseP is important for sensitivity to bacteriocin EntK1

Enterocin K1 (EntK1), a bacteriocin that is highly potent against vancomycin-resistant enterococci, depends on binding to an intramembrane protease of the site-2 protease family, RseP, for its antimicrobial activity. RseP is highly conserved in both EntK1-sensitive and EntK1-insensitive bacteria, and the molecular mechanisms underlying the interaction between RseP and EntK1 and bacteriocin sensitivity are unknown. Here, we describe a mutational study of RseP from EntK1-sensitive Enterococcus faecium to identify regions of RseP involved in bacteriocin binding and activity. Mutational effects were assessed by studying EntK1 sensitivity and binding with strains of naturally EntK1-insensitive Lactiplantibacillus plantarum–expressing various RseP variants. We determined that site-directed mutations in conserved sequence motifs related to catalysis and substrate binding, and even deletion of two such motifs known to be involved in substrate binding, did not abolish bacteriocin sensitivity, with one exception. A mutation of a highly conserved asparagine, Asn359, in the extended so-called LDG motif abolished both binding of and killing by EntK1. By constructing various hybrids of the RseP proteins from sensitive E. faecium and insensitive L. plantarum, we showed that the extracellular PDZ domain is the key determinant of EntK1 sensitivity. Taken together, these data may provide valuable insight for guided construction of novel bacteriocins and may contribute to establishing RseP as an antibacterial target.

Identification of a Novel Two-Peptide Lantibiotic from Vagococcus fluvialis

Infections caused by multiresistant pathogens have become a major problem in both human and veterinary medicine. Due to the declining efficacy of many antibiotics, new antimicrobials are needed. Promising alternatives or additions to antibiotics are bacteriocins, antimicrobial peptides of bacterial origin with activity against many pathogens, including antibiotic-resistant strains. From a sample of fermented maize, we isolated a Vagococcus fluvialis strain producing a bacteriocin with antimicrobial activity against multiresistant Enterococcus faecium. Whole-genome sequencing revealed the genes for a novel two-peptide lantibiotic. The production of the lantibiotic by the isolate was confirmed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry, which revealed distinct peaks at 4,009.4 m/z and 3,181.7 m/z in separate fractions from reversed-phase chromatography. The combination of the two peptides resulted in a 1,200-fold increase in potency, confirming the two-peptide nature of the bacteriocin, named vagococcin T. The bacteriocin was demonstrated to kill sensitive cells by the formation of pores in the cell membrane, and its inhibition spectrum covers most Gram-positive bacteria, including multiresistant pathogens. To our knowledge, this is the first bacteriocin characterized from Vagococcus. IMPORTANCE Enterococci are common commensals in the intestines of humans and animals, but in recent years, they have been identified as one of the major causes of hospital-acquired infections due to their ability to quickly acquire virulence and antibiotic resistance determinants. Many hospital isolates are multiresistant, thereby making current therapeutic options critically limited. Novel antimicrobials or alternative therapeutic approaches are needed to overcome this global problem. Bacteriocins, natural ribosomally synthesized peptides produced by bacteria to eliminate other bacterial species living in a competitive environment, provide such an alternative. In this work, we purified and characterized a novel two-peptide lantibiotic produced by Vagococcus fluvialis LMGT 4216 isolated from fermented maize. The novel lantibiotic showed a broad spectrum of inhibition of Gram-positive strains, including vancomycin-resistant Enterococcus faecium, demonstrating its therapeutic potential.

Bacterial diversity significantly reduces toward the late stages among filarial lymphedema patients in the Ahanta West District of Ghana: A cross-sectional study

Background

Lymphatic Filariasis (LF), a neglected tropical disease, has been speculated to be complicated by secondary bacteria, yet a systematic documentation of these bacterial populations is lacking. Thus, the primary focus of this study was to profile bacteria diversity in the progression of filarial lymphedema among LF individuals with or without wounds.

Methods

A cross-sectional study design recruited 132 LF individuals presenting with lymphedema with or without wounds from eight communities in the Ahanta West District in the Western Region, Ghana. Swabs from the lymphedematous limbs, ulcers, pus, and cutaneous surfaces were cultured using standard culture-based techniques. The culture isolates were subsequently profiled using Matrix-assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry.

Results

Of the 132 LF participants recruited, 65% (85) had filarial lymphedema with no wounds. In total, 84% (235) of the bacterial isolates were identified. The remaining 16% (46) could not be identified with the method employed. Additionally, 129(55%) of the strains belonged to the phylum Firmicutes, while 61 (26%) and 45 (19%) represented Proteobacteria and Actinobacteria, respectively. Generally, irrespective of the samples type (i.e., wound sample and non-wound samples), there was a sharp increase of bacteria diversity from Stages 1 to 3 and a drastic decrease in these numbers by Stage 4, followed by another surge and a gradual decline in the advanced stages of the disease. The Shannon Diversity Index and Equitability for participants with and without wounds were (3.482, 0.94) and (3.023, 0.75), respectively. Further, Staphylococcus haemolyticus and Escherichia coli showed resistance to tetracycline, chloramphenicol, and penicillin.

Conclusion

The present study reveals a sharp decline in bacterial load at the late stages of filarial lymphedema patients. In addition, we report an emerging antimicrobial resistance trend of S. haemolyticus and E. coli against commonly used antibiotics such as tetracycline, chloramphenicol, and penicillin in communities endemic for LF in the Ahanta West District, Ghana. This could pose a huge challenge to the management of the disease; particularly as current treatments are not quite effective against the infection.

Conserved Proline Residues of Bacillus subtilis Intramembrane Metalloprotease SpoIVFB Are Important for Substrate Interaction and Cleavage

Intramembrane metalloproteases (IMMPs) regulate diverse biological processes by cleaving membrane-associated substrates within the membrane or near its surface. SpoIVFB is an intramembrane metalloprotease of Bacillus subtilis that cleaves Pro-σK during endosporulation. Intramembrane metalloproteases have a broadly conserved NPDG motif, which in the structure of an archaeal enzyme is located in a short loop that interrupts a transmembrane segment facing the active site. The aspartate residue of the NPDG motif acts as a ligand of the zinc ion involved in catalysis. The functions of other residues in the short loop are less well understood. We found that the predicted short loop of SpoIVFB contains two highly conserved proline residues, P132 of the NPDG motif and P135. Mutational analysis revealed that both proline residues are important for Pro-σK cleavage in Escherichia coli engineered to synthesize the proteins. Substitutions for either residue also impaired the Pro-σK interaction with SpoIVFB in copurification assays. Disulfide cross-linking experiments showed that the predicted short loop of SpoIVFB is in proximity to the N-terminal pro-sequence region (Proregion) of Pro-σK. Alanine substitutions for N129 and P132 of the SpoIVFB NPDG motif reduced cross-linking between its predicted short loop and the Proregion more than a P135A substitution. Conversely, the SpoIVFB P135A substitution reduced Pro-σK cleavage more than the N129A and P132A substitutions during sporulation of B. subtilis. We conclude that all three conserved residues of SpoIVFB are important for substrate interaction and cleavage, and we propose that P135 is necessary to position D137 to act as a zinc ligand. IMPORTANCE Intramembrane metalloproteases (IMMPs) function in numerous signaling pathways. Bacterial IMMPs govern stress responses, including the sporulation of some species, thus enhancing the virulence and persistence of pathogens. Knowledge of IMMP-substrate interactions could aid therapeutic design, but structures of IMMP·substrate complexes are unknown. We examined the interaction of the IMMP SpoIVFB with its substrate Pro-σK, whose cleavage is required for Bacillus subtilis endosporulation. We found that conserved proline residues in a short loop predicted to interrupt a SpoIVFB transmembrane segment are important for Pro-σK binding and cleavage. The corresponding residues of the Escherichia coli IMMP RseP have also been shown to be important for substrate interaction and cleavage, suggesting that this is a broadly conserved feature of IMMPs, potentially suitable as a therapeutic target.

Influence of Sub-Inhibitory Dosage of Cefotaxime on Multidrug Resistant Staphylococcus haemolyticus Isolated from Sick Neonatal Care Unit

Staphylococcus haemolyticus has emerged to be a frequently encountered late-onset sepsis pathogen among newborn infants. Critical care of neonates involves substantial usage of antibiotics and these pathogens are often exposed to sub-optimal doses of antibiotics which can augment maintenance of selection determinants and a range of physiological effects, prime among them being biofilm formation. Therefore, in this study, the outcome of a sub-inhibitory dosage of a commonly prescribed third-generation antibiotic, cefotaxime (CTX), on multidrug resistant (MDR) S. haemolyticus, was investigated. A total of 19 CTX-resistant, MDR and 5 CTX-susceptible strains isolated from neonates were included. Biofilm-forming abilities of S. haemolyticus isolates in the presence of sub-optimal CTX (30 μg/mL) were determined by crystal violet assays and extracellular DNA (eDNA) quantitation. CTX was found to significantly enhance biofilm production among the non-susceptible isolates (p-valueWilcoxintest—0.000008) with an increase in eDNA levels (p-valueWilcoxintest—0.000004). Further, in the absence of antibiotic selection in vitro, populations of MDR isolates, JNM56C1 and JNM60C2 remained antibiotic non-susceptible after >500 generations of growth. These findings demonstrate that sub-optimal concentration of CTX induces biofilm formation and short-term non-exposure to antibiotics does not alter non-susceptibility among S. haemolyticus isolates under the tested conditions.

Garvicin KS, a Broad-Spectrum Bacteriocin Protects Zebrafish Larvae against Lactococcus garvieae Infection

Bacteriocins are emerging as a viable alternative to antibiotics due to their ability to inhibit growth or kill antibiotic resistant pathogens. Herein, we evaluated the ability of the bacteriocin Garvicin KS (GarKS) produced by Lactococcus garvieae KS1546 isolated from cow milk to inhibit the growth of fish and foodborne bacterial pathogens. We found that GarKS inhibited the growth of five fish L. garvieae strains isolated from infected trout and eels. Among fish pathogens, GarKS inhibited the growth of Streptococcus agalactiae serotypes Ia and Ib, and Aeromonas hydrophila but did not inhibit the growth of Edwardsiella tarda. In addition, it inhibited the growth of A. salmonicida strain 6421 but not A. salmonicida strain 6422 and Yersinia ruckeri. There was no inhibition of three foodborne bacterial species, namely Salmonella enterica, Klebsiella pneumoniae, and Escherichia coli. In vitro cytotoxicity tests using different GarKS concentrations showed that the highest concentration of 33 µg/mL exhibited low cytotoxicity, while concentrations ≤3.3 µg/mL had no cytotoxicity on CHSE-214 and RTG-2 cells. In vivo tests showed that zebrafish larvae treated with 33 µg/mL and 3.3 µg/mL GarKS prior to challenge had 53% and 48% survival, respectively, while concentrations ≤0.33 µg/mL were nonprotective. Altogether, these data show that GarKS has a broad inhibitory spectrum against Gram positive and negative bacteria and that it has potential applications as a therapeutic agent for a wide range of bacterial pathogens. Thus, future studies should include clinical trials to test the efficacy of GarKS against various bacterial pathogens in farmed fish.

Prevalence of Methicillin-Resistant Staphylococcus Species Among Filarial Lymphedema Patients in Ahanta West District of Ghana

Background

Filarial pathologies such as lymphedema may be associated with complications such as chronic non-healing wounds. Nonetheless, the role of bacterial population colonizing the lymphedematous legs has been posited to worsen the conditions of those living with the infection. These bacteria are usually composed of staphylococcal species partly because they are commensals. Thus, this present study sought to type the methicillin-resistant Staphylococcus aureus (MRSA) prevalence among individuals presenting with filarial lymphedema, particularly as MRSA tends to affect treatments options.

Methods

We recruited individuals (n = 321) with stages I–VII of lymphedema in a cross-sectional study in the Ahanta West district of the Western Region of Ghana. Swabs from lymphedematous limb ulcers, pus, and cutaneous surfaces were cultured using standard culture-based techniques. The culture isolates were later identified using Matrix-assisted Laser Desorption/Ionization Time of Flight (MALDI-TOF) mass spectrometry.

Results

A total of 192 Staphylococci species were isolated, with an overall prevalence of 39.7% (95% CI: 35%–44%; N = 483). S. hominis was the most prevalent species (23.95%), followed by S. haemolyticus (20.83%), S. epidermidis (15.10%), S. aureus (10.41%), and S. saprophyticus (9.32%). The remaining 20.34% were distributed among S. wanneri, S. sciuri, S. pasteuri, S. xylosus, S. simulans, S. cohnii, S. caprae, S. lugdunensis, and S. capitis. MRSA, containing mecA gene, was detected in 21 out of 31 Staphylococci isolates tested, with an overall prevalence of 68% (95% CI: 51%–84%). In addition, a virulent gene, Panton–Valentine leukocidin (PVL), which is usually associated with S. aureus, was detected in 20/31 (64.5%) S. aureus in the study.

Conclusion

These results suggest that MRSA species may pose a challenge to the treatment of filarial lymphedema with antibiotics particularly, as doxycycline is currently being piloted in some endemic areas to treat the infection. Thus, intensive antimicrobial resistance surveillance should be conducted in endemic areas by health authorities to forestall the dilemma of multidrug resistance not only against lymphatic filariasis (LF) infection but other diseases.