The Genomic Basis of Intrinsic and Acquired Antibiotic Resistance in the Genus Serratia

Proteomic profile of multidrug-resistant Serratia marcescens under meropenem challenge

Serratia marcescens is an opportunistic bacterium implicated in the prevalence of serious nosocomial infections and increased outbreaks in Intensive Care Units (ICUs) and Neonatal Intensive Care Units (NICUs). S. marcescens strains are resistant to several antimicrobial classes and express numerous virulence factors that promote pathogenicity. In the present study, the proteomic profile of the multidrug-resistant (MDR) S. marcescens clinical isolate challenged with the antimicrobial meropenem was evaluated. The proteins obtained were analyzed using liquid chromatography coupled with tandem mass spectrometry (LC-MSE). A total of 199 induced proteins were identified revealing that multidrug-resistant S. marcescens promotes increasing of proteins related to energy metabolism and efflux pump and decreases synthesis of proteins related to oxidative stress response and cell mobility upon meropenem challenge, shedding some light on the relationship between expressed proteins and bacterial pathogenicity after antimicrobial induction.

Co-exposure of pyraclostrobin and biochar promoted antibiotic resistance genes transfer from soil to lettuce

The widespread presence of antibiotic resistance genes (ARGs) threatens ecological security and human health. In agricultural production, the simultaneous presence of non-antibiotic substances fungicides and biochar utilized for soil remediation has unclear effects on the spread of ARGs in the soil-vegetable systems. Herein, this study conducted a pots experiment and found that biochar significantly reduced pyraclostrobin accumulation in the soil and lettuce roots. Simultaneously, the co-exposure of pyraclostrobin and biochar increased the microbial community alpha diversity and the abundance of ARGs in soil, while promoting the transfer of ARGs from soil to lettuce. Proteobacteria were identified as potential primary carriers of ARGs. Planting lettuce mitigated the effects of pyraclostrobin or/and biochar on ARGs accumulation in soil. Furthermore, MGEs and bacterial community abundance were the most important direct factors increasing ARGs in soil and lettuce. Overall, these findings evaluated the combined effects of non-antibiotic substances fungicides and soil remediation materials biochar on the generation and transmission of ARGs, providing potential strategies for controlling ARGs transfer in soil-vegetable systems.

Genomic insights into pigmented Serratia marcescens strains isolated from patients in northeast Mexico

Serratia marcescens (SM) is an opportunistic pathogen associated with outbreaks in immunocompromised hosts. While SM is commonly isolated from clinical and environmental sources, prodigiosin production is typically associated with environmental strains rather than clinical isolates. Here, we report the genome sequences of three pigmented SM clinical isolates -HU1848, HU2225, and HU2228- and examine their genomic and phenotypic characteristics. Phylogenetic analysis using 1103 finished public SM genomes revealed that these isolates cluster more closely with environmental SM strains than with those typically associated with clinical settings. Notably, despite their environmental-like genomic background, these isolates harbor multiple virulence genes implicated in colonization and resistance to fertilizers, as well as antimicrobial resistance genes for chloramphenicol, fosfomycin, and tetracycline. MIC determination showed susceptibility to aminoglycosides and fluoroquinolones. Additionally, we observed that the phenolic compound methyl gallate modulates pigment production and motility. The absence of AHL biosynthetic genes in these pigmented strains challenges previous associations between quorum sensing and prodigiosin biosynthesis. These findings suggest that certain SM strains with environmental-like genetic features can persist in clinical settings, underscoring the need to further investigate their potential role in nosocomial infections.

Assessment of spoilage microbial communities in modified atmosphere-packed ready-to-eat salad during cold storage: A comparative study using MALDI-TOF MS identification and PacBio full-length 16S rRNA and ITS sequencing

Effect of storage temperatures and modified atmosphere packaging (MAP) on the shelf-life and spoilage microbial dynamics of industrially produced mayonnaise-based potato salad was studied over two years (Spring 2021, Autumn 2021, Spring 2022). Three salad batches, stored at chilling and abuse temperatures ranging from 0 °C to 12 °C, were analyzed. Microbial communities were evaluated using ISO-standard microbiological methods, MALDI-TOF MS identification, and PacBio full-length 16S rRNA gene and fungal ITS amplicon sequencing. The results showed that sensory and microbiological quality strongly depended on storage temperature, MAP packaging, and salad batch. The recommended upper temperature limit of 6 °C did not preserve salad quality at the end of its shelf-life, while storage below 4 °C extended the seven-day shelf-life to 10 days. Distinct spoilage communities were identified across batches, dominated by Dellaglioa algida, Leuconostoc carnosum, and Latilactobacillus sakei (Spring 2021); Leuconostoc inhae and Leuconostoc gelidum (Autumn 2021); and Lactococcus carnosus (Spring 2022). The microbial communities of ingredients and processing facilities influenced salad microbiota. Comparative analysis showed that full-length 16S rRNA sequencing provided higher resolution, detecting species missed by culturing methods, including psychrotrophic and fastidious lactic acid bacteria. However, fungal community analysis, using full-length ITS amplicons, requires the selection of specific fungal primers. This study provides a comprehensive evaluation of microbial profiles in RTE salads under different storage conditions, highlighting the critical role of temperature and microbial management in preserving MAP salad safety and quality during extended shelf-life.

Phenotypic and in silico characterization of carbapenem-resistant Serratia marcescens clinical strains

BACKGROUND

Serratia marcescens, an opportunistic nosocomial Gram-negative bacterium pathogen, has emerged as an important cause of healthcare-associated infections owing to its acquisition of antimicrobial resistance genes (ARGs) and virulence factor determinants.

METHODS

Four carbapenem-resistant S. marcescens strains were recovered from patients admitted to different hospitals in 2017 and 2018. We assessed the antimicrobial resistance and virulence context, as well as the genetic similarities of four Brazilian S. marcescens strains, and compared the genomes of these S. marcescens isolates with whole genome data of 428 S. marcescens strains available in the NCBI Reference Sequence. Antimicrobial susceptibility testing was performed by disk diffusion and broth microdilution methods according to CLSI recommendations. Whole genome sequencing was performed using Illumina NextSeq 250-bp paired-end sequencing for two isolates, Sm424 and Sm613, which presented representative phenotypes.

RESULTS

The pathogenicity of both sequenced strains was predicted using the Pathogen Finder tool. Both isolates carried efflux system genes (RND, SMR, MFS, ABC-family) and resistance genes (blaSTR-2, aac(6')-Ic, fos). Virulence factor genes involved in motility, regulation, capsule formation, acid resistance, and acriflavine resistance were also found. The Pathogen Finder tool predicted a > 71% probability of being a human pathogen for Sm424 and Sm613.

CONCLUSION

S. marcescens has shown increased adaptive, resistance, and pathogenic potential, being responsible for different nosocomial infections.

A comprehensive analysis of the epidemiological and genomic characteristics of global Serratia Marcescens

BACKGROUND

Serratia marcescens outbreaks present significant challenges in clinical treatment, necessitating a deeper understanding of its epidemiological and genomic traits.

OBJECTIVE

To analyse the epidemiological and genomic characteristics of S. marcescens at a global scale.

METHODS

High-quality genomes of S. marcescens were retrieved from NCBI and annotated using Prodigal. Antibiotic resistance genes (ARGs) were identified via Blastn, sequence types (STs) were determined with a proprietary tool, and phylogenetic analysis was conducted to explore evolutionary relationships.

RESULTS

The study analysed genomes from 33 countries, with major contributions from the USA (27.8%), UK (15.3%), Italy (14.7%), and Japan (10.7%). Human clinical samples accounted for 73.5% of the isolates, primarily from blood (44.8%) and sputum (19.3%). Eleven ARGs were identified, with sde being the most prevalent. Carbapenemase genes included blaSME, blaKPC, and blaNDM-1, though co-occurrence in individual strains was absent. Novel ARGs, including armA, rmtC, and fosA7.2, were reported. Among 855 genomes with identified STs, ST366, ST367, ST365, and ST423 were most common. Phylogenetic analysis highlighted significant genetic diversity and distinct evolutionary lineages.

CONCLUSION

Temporal analysis showed a genome peak in 2019, underscoring the global prevalence and adaptability of S. marcescens. The distribution of ARGs across diverse STs emphasizes horizontal gene transfer as a key driver of resistance. Judicious antibiotic use is essential to mitigate further resistance.

How nanoscale plastics facilitate the evolution of antibiotic resistance?

The plastic can enhance the proliferation of antibiotic resistance genes (ARGs), however, the effect of nanoplastics (NPLs) on bacterial antibiotic resistance has not been clearly explained. Herein, we explored the effects and mechanisms of NPLs of different sizes (200 and 600 nm) on the evolution of antibiotic resistance in Serratia marcescens. The results indicated that the evolution of bacterial antibiotic resistance could be promoted under NPLs exposure, which the median of relative abundance of ARGs was 1.11-1.46 times compared to the treatment without NPLs. Transcriptomic analysis showed that the larger size of NPLs mainly increased the permeability of bacterial cell membranes to efflux antibiotics, thus potentiating antibiotic resistance. While, the smaller NPLs is more than that, its enhanced the expression of antibiotic resistance by modulating bacterial metabolic processes. The genome SNP analysis found that the NPLs could cause the genetic mutation occurrence to alter the membrane transport and metabolism processes, and it increased at a size of 200 nm more than at 600 nm NPLs. Importantly, we demonstrated that the horizontal transfer of ARGs was augmented due to the NPLs could dock to bacterial surface proteins and pull their movement to contact with other bacteria (binding energy of membrane proteins: -8.54 kcal/mol), especially the smaller size. It suggests that NPLs will also contribute to the proliferation of ARGs in the environment. This study provides data for understanding the risk of bacterial resistance.

Impact of the Stress Response on Quaternary Ammonium Compound Disinfectant Susceptibility in Serratia Species

The well-known problem of antibiotic resistance foreshadows a similar threat posed by microbial resistance to biocides such as disinfectants and antiseptics. These products are vital for infection control, yet their overuse during the COVID-19 pandemic has accelerated the development of resistant microorganisms. This study investigates the molecular mechanisms underlying disinfectant resistance in Serratia sp. HRI. The transcriptomic responses of Serratia sp. HRI were used to identify significant gene expression changes during exposure to QACs and revealed increased methionine transport and polyamine synthesis. Polyamines, crucial in cellular stress responses, were notably upregulated, suggesting a pivotal role of the stress response in disinfectant resistance. Further, our susceptibility tests revealed a marked decrease in susceptibility to QACs under various stress conditions, supporting the hypothesis that stress responses, mediated by polyamines, decrease susceptibility to QACs. This research highlights polyamines as key players in disinfectant resistance, offering novel insights into resistance mechanisms and antimicrobial susceptibility. Our findings emphasise the need for continued investigation into disinfectant resistance and the role of stress responses, particularly polyamine-mediated mechanisms, to direct strategies for preserving disinfectant efficacy and developing future antimicrobial agents.

A novel broad-spectrum antibacterial and anti-malarial Anopheles gambiae Cecropin promotes microbial clearance during pupation

Anophelinae mosquitoes are exposed to a variety of microbes including Plasmodium parasites that cause malaria. When infected, mosquitoes mount versatile immune responses, including the production of antimicrobial peptides. Cecropins are one of the most widely distributed families of antimicrobial peptides in insects and all previously studied Anopheles members are playing roles in adult mosquito immunity. We have identified and characterized a novel member of the Anopheles gambiae cecropin family, cecropin D (CecD), that is uniquely expressed and immune-responsive at late larval stages to promote microbial clearance through its broad-spectrum antibacterial activity during larval-pupal developmental transition. Interestingly, Cecropin D also exhibited highly potent activity against Plasmodium falciparum sporozoites, the malaria parasite stage that is transmitted from mosquitoes and infects humans and thereby holds promise as a malaria transmission-blocking agent. Finally, we have defined unequivocal cecropin-specific molecular signatures to systematically organize the diversity of the cecropin family in malaria vectors.

Antimicrobial Resistance in Equines: A Growing Threat to Horse Health and Beyond-A Comprehensive Review

The equine industry holds substantial economic importance not only in the USA but worldwide. The occurrence of various infectious bacterial diseases in horses can lead to severe health issues, economic losses, and restrictions on horse movement and trade. Effective management and control of these diseases are therefore crucial for the growth and sustainability of the equine industry. While antibiotics constitute the primary treatment strategy for any bacterial infections in horses, developing resistance to clinically important antibiotics poses significant challenges to equine health and welfare. The adverse effects of antimicrobial overuse and the escalating threat of resistance underscore the critical importance of antimicrobial stewardship within the equine industry. There is limited information on the epidemiology of antimicrobial-resistant bacterial infections in horses. In this comprehensive review, we focus on the history and types of antimicrobials used in horses and provide recommendations for combating drug-resistant bacterial infections in horses. This review also highlights the epidemiology of antimicrobial resistance (AMR) in horses, emphasizing the public health significance and transmission dynamics between horses and other animals within a One Health framework. By fostering responsible practices and innovative control measures, we can better help the equine industry combat the pressing threat of AMR and thus safeguard equine as well as public health.

Antibiotic Resistance in Enterococci and Enterobacteriaceae from Laboratory-Reared Fresh Mealworm Larvae (Tenebrio molitor L.) and Their Frass

The occurrence of antibiotic-resistant bacteria in foodstuff involves a human health risk. Edible insects are a precious resource; however, their consumption raises food safety issues. In this study, the occurrence of antibiotic resistant bacteria in laboratory-reared fresh mealworm larvae (Tenebrio molitor L.) and frass was assessed. Antibiotics were not used during the rearing. Enterobacteriaceae and enterococci were isolated from 17 larvae and eight frass samples. In total, 62 and 69 isolates presumed to belong to Enterobacteriaceae and Enterococcus spp., respectively, were obtained and tested for antibiotic susceptibility via disk diffusion. Based on the results, isolates were grouped, and representative resistant isolates were identified at species level through 16S rRNA gene sequencing. For enterococci resistance, percentages higher than 15% were observed for vancomycin and quinupristin-dalfopristin, whereas Enterobacteriaceae resistance higher than 25% was found against cefoxitin, ampicillin, and amoxicillin-clavulanic acid. Based on the species identification, the observed resistances seemed to be intrinsic both for enterococci and Enterobacteriaceae, except for some β-lactams resistance in Shigella boydii (cefoxitin and aztreonam). These could be due to transferable genetic elements. This study suggests the need for further investigations to clarify the role of edible insects in the spreading of antibiotic resistance determinants through the food chain.

The ICU environment contributes to the endemicity of the "Serratia marcescens complex" in the hospital setting

Serratia marcescens is an opportunistic pathogen historically associated with sudden outbreaks in intensive care units (ICUs) and the spread of carbapenem-resistant genes. However, the ecology of S. marcescens populations in the hospital ecosystem remains largely unknown. We combined epidemiological information of 1,432 Serratia spp. isolates collected from sinks of a large ICU that underwent demographic and operational changes (2019-2021) and 99 non-redundant outbreak/non-outbreak isolates from the same hospital (2003-2019) with 165 genomic data. These genomes were grouped into clades (1-4) and subclades (A and B) associated with distinct species: Serratia nematodiphila (1A), S. marcescens (1B), Serratia bockelmannii (2A), Serratia ureilytica (2B), S. marcescens/Serratia nevei (3), and S. nevei (4A and 4B). They may be classified into an S. marcescens complex (SMC) due to the similarity between/within subclades (average nucleotide identity >95%-98%), with clades 3 and 4 predominating in our study and publicly available databases. Chromosomal AmpC β-lactamase with unusual basal-like expression and prodigiosin-lacking species contrasted classical features of Serratia. We found persistent and coexisting clones in sinks of subclades 4A (ST92 and ST490) and 4B (ST424), clonally related to outbreak isolates carrying blaVIM-1 or blaOXA-48 on prevalent IncL/pB77-CPsm plasmids from our hospital since 2017. The distribution of SMC populations in ICU sinks and patients reflects how Serratia species acquire, maintain, and enable plasmid evolution in both "source" (permanent, sinks) and "sink" (transient, patients) hospital patches. The results contribute to understanding how water sinks serve as reservoirs of Enterobacterales clones and plasmids that enable the persistence of carbapenemase genes in healthcare settings, potentially leading to outbreaks and/or hospital-acquired infections.IMPORTANCEThe "hospital environment," including sinks and surfaces, is increasingly recognized as a reservoir for bacterial species, clones, and plasmids of high epidemiological concern. Available studies on Serratia epidemiology have focused mainly on outbreaks of multidrug-resistant species, overlooking local longitudinal analyses necessary for understanding the dynamics of opportunistic pathogens and antibiotic-resistant genes within the hospital setting. This long-term genomic comparative analysis of Serratia isolated from the ICU environment with isolates causing nosocomial infections and/or outbreaks within the same hospital revealed the coexistence and persistence of Serratia populations in water reservoirs. Moreover, predominant sink strains may acquire highly conserved and widely distributed plasmids carrying carbapenemase genes, such as the prevalent IncL-pB77-CPsm (pOXA48), persisting in ICU sinks for years. The work highlights the relevance of ICU environmental reservoirs in the endemicity of certain opportunistic pathogens and resistance mechanisms mainly confined to hospitals.

Detection of clinical Serratia marcescens isolates carrying blaKPC-2 in a hospital in China

Serratia marcescens is an opportunistic and nosocomial pathogen found in the intensive care unit (ICU), but its antimicrobial resistance (AMR) is rarely addressed. Here, we reported two blaKPC-2-positive S. marcescens strains, SMBC31 and SMBC50, recovered from the ICU of a hospital in Zhengzhou, China. The minimum inhibitory concentration (MIC) was determined using the broth microdilution method, while S1-PFGE was employed to demonstrate plasmid size approximation. Complete genome sequences were obtained through Illumina NovaSeq 6000 and Oxford Nanopore Technologies. Both strains exhibit resistance to meropenem and harbor the blaKPC-2 and blaSRT-1 resistance genes. The plasmid pSMBC31-39K in strain SMBC31 and pSMBC50-107K in strain SMBC50 were identified as carrying the blaKPC-2 gene. Notably, both of these plasmids were successfully transferred to Escherichia coli strain J53. Phylogenetic analysis based on plasmid sequences revealed that pSMBC31-39K exhibited high homology with plasmids found in Aeromonas caviae, Citrobacter sp., and Pseudomonas aeruginosa, while pSMBC50-107K showed significant similarity to those of E. coli and Klebsiella pneumoniae. Notably, the coexistence of blaKPC-2 and blaSRT-1 was observed in all 94 KPC-2-producing S. marcescens strains by mining all genomes available under the GenBank database, which were mainly isolated from hospitalized patients. The emergence of multidrug-resistant S. marcescens poses significant challenges in treating clinical infections, highlighting the need for increased surveillance of this pathogen.

Taxonomic Diversity and Functional Traits of Soil Bacterial Communities under Radioactive Contamination: A Review

Studies investigating the taxonomic diversity and structure of soil bacteria in areas with enhanced radioactive backgrounds have been ongoing for three decades. An analysis of data published from 1996 to 2024 reveals changes in the taxonomic structure of radioactively contaminated soils compared to the reference, showing that these changes are not exclusively dependent on contamination rates or pollutant compositions. High levels of radioactive exposure from external irradiation and a high radionuclide content lead to a decrease in the alpha diversity of soil bacterial communities, both in laboratory settings and environmental conditions. The effects of low or moderate exposure are not consistently pronounced or unidirectional. Functional differences among taxonomic groups that dominate in contaminated soil indicate a variety of adaptation strategies. Bacteria identified as multiple-stress tolerant; exhibiting tolerance to metals and antibiotics; producing antioxidant enzymes, low-molecular antioxidants, and radioprotectors; participating in redox reactions; and possessing thermophilic characteristics play a significant role. Changes in the taxonomic and functional structure, resulting from increased soil radionuclide content, are influenced by the combined effects of ionizing radiation, the chemical toxicity of radionuclides and co-contaminants, as well as the physical and chemical properties of the soil and the initial bacterial community composition. Currently, the quantification of the differential contributions of these factors based on the existing published studies presents a challenge.

Diversity of antimicrobial-resistant bacteria isolated from Australian chicken and pork meat

Antimicrobial-resistant bacteria are frequently isolated from retail meat and may infect humans. To determine the diversity of antimicrobial-resistant bacteria in Australian retail meat, bacteria were cultured on selective media from raw chicken (n = 244) and pork (n = 160) meat samples obtained from all four major supermarket chains in the ACT/NSW, Australia, between March and June 2021. Antimicrobial susceptibility testing (AST) was performed for 13 critically and 4 highly important antibiotics as categorised by the World Health Organization (WHO) for a wide range of species detected in the meat samples. A total of 288 isolates underwent whole-genome sequencing (WGS) to identify the presence of antimicrobial resistance (AMR) genes, virulence genes, and plasmids. AST testing revealed that 35/288 (12%) of the isolates were found to be multidrug-resistant (MDR). Using WGS data, 232/288 (81%) of the isolates were found to harbour resistance genes for critically or highly important antibiotics. This study reveals a greater diversity of AMR genes in bacteria isolated from retail meat in Australia than previous studies have shown, emphasising the importance of monitoring AMR in not only foodborne pathogenic bacteria, but other species that are capable of transferring AMR genes to pathogenic bacteria.

Fernández-de-Bobadilla M, Serrano-Tomás MI, Sánchez-Díaz AM, Avendaño-Ortiz J, Coque TM, Ruiz-Garbajosa P, del Campo R, Cantón R. A long-term survey of Serratia spp. bloodstream infections revealed an increase of antimicrobial resistance involving adult population

Serratia spp. is a well-recognized pathogen in neonates; however, limited data are available in adults. We studied microbiological and clinical characteristics of Serratia spp. causing bloodstream infections (BSI) in our institution (January 2005-July 2020). Overall, 141 BSI episodes affecting 139 patients were identified and medical records reviewed. Antimicrobial susceptibility was recovered from our informatics system and 118 isolates from 116 patients were available for further microbiological studies. Whole genome sequencing (WGS) was completed in 107 isolates. Incidence of Serratia BSI was 0.3/1000 overall admissions (range 0.12-0.60), with maximum prevalence (27 episodes, 19.1%) during 2017-2018. Relevant patients' clinical characteristics were 71.9% ≥60 years (n = 100), with high comorbidity rates (49%, ≥2), 23 (74.2%) of them died within 1 month of the BSI episode. WGS identified all isolates as Serratia marcescens when Kraken bioinformatics taxonomic tool was used despite some which were identified as Serratia nematodiphila (32/118) or Serratia ureilytica (5/118) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Nevertheless, when using MASH distance, Serratia nevei (63/107), S. ureilytica (38/107), and S. marcescens (6/107) were assigned. Carbapenemase (blaVIM-1) and extended-spectrum β-lactases (ESBL) (blaSHV-12) genes were found in seven and three isolates, respectively, one of them expressing both genes. The worldwide-disseminated IncL/M scaffold plasmid was identified in six VIM producers. Four genotypes were established based on their virulence factors and resistome. Serratia spp. emerged as a relevant nosocomial pathogen causing BSI in elderly patients in our hospital, particularly in recent years with a remarkable increase in antibiotic resistance. ESBL and carbapenemases production related to plasmid dissemination are particularly noteworthy.IMPORTANCESerratia spp. is the third most frequent pathogen involved in outbreaks at neonatal facilities and is primarily associated with bacteremia episodes. In this study, we characterized all causing bloodstream infection (BSI) in patients admitted to our hospital during a 16-year period (2005-2020). Despite having no neonatal intensive care unit in our hospital, this study revealed that Serratia spp. is a relevant pathogen causing BSI in elderly patients with high comorbidity rates. A significant increase of antimicrobial resistance was detected over time, particularly in 2020 and coinciding with the coronavirus disease (COVID-19) pandemic and nosocomial spread of multidrug-resistant Serratia spp. isolates. extended-spectrum β-lactases and carbapenemases genes associated with plasmid dissemination, typically detected in other Enterobacterales species, were also identified, reinforcing the role of Serratia spp. in the antimicrobial resistance landscape. Additionally, this work highlights the need to reclassify the species of Serratia, since discrepancies were observed in the identification when using different tools.

Shotgun Metagenomics Reveals Impacts of Copper and Water Heater Anodes on Pathogens and Microbiomes in Hot Water Plumbing Systems

Hot water building plumbing systems are vulnerable to the proliferation of opportunistic pathogens (OPs), including Legionella pneumophila and Mycobacterium avium. Implementation of copper as a disinfectant could help reduce OPs, but a mechanistic understanding of the effects on the microbial community under real-world plumbing conditions is lacking. Here, we carried out a controlled pilot-scale study of hot water systems and applied shotgun metagenomic sequencing to examine the effects of copper dose (0-2 mg/L), orthophosphate corrosion control agent, and water heater anode materials (aluminum vs magnesium vs powered anode) on the bulk water and biofilm microbiome composition. Metagenomic analysis revealed that, even though a copper dose of 1.2 mg/L was required to reduce Legionella and Mycobacterium numbers, lower doses (e.g., ≤0.6 mg/L) measurably impacted the broader microbial community, indicating that the OP strains colonizing these systems were highly copper tolerant. Orthophosphate addition reduced bioavailability of copper, both to OPs and to the broader microbiome. Functional gene analysis indicated that both membrane damage and interruption of nucleic acid replication are likely at play in copper inactivation mechanisms. This study identifies key factors (e.g., orthophosphate, copper resistance, and anode materials) that can confound the efficacy of copper for controlling OPs in hot water plumbing.

Antimicrobial Resistance in Romania: Updates on Gram-Negative ESCAPE Pathogens in the Clinical, Veterinary, and Aquatic Sectors

Multidrug-resistant Gram-negative bacteria such as Acinetobacter baumannii, Pseudomonas aeruginosa, and members of the Enterobacterales order are a challenging multi-sectorial and global threat, being listed by the WHO in the priority list of pathogens requiring the urgent discovery and development of therapeutic strategies. We present here an overview of the antibiotic resistance profiles and epidemiology of Gram-negative pathogens listed in the ESCAPE group circulating in Romania. The review starts with a discussion of the mechanisms and clinical significance of Gram-negative bacteria, the most frequent genetic determinants of resistance, and then summarizes and discusses the epidemiological studies reported for A. baumannii, P. aeruginosa, and Enterobacterales-resistant strains circulating in Romania, both in hospital and veterinary settings and mirrored in the aquatic environment. The Romanian landscape of Gram-negative pathogens included in the ESCAPE list reveals that all significant, clinically relevant, globally spread antibiotic resistance genes and carrying platforms are well established in different geographical areas of Romania and have already been disseminated beyond clinical settings.

Immunotherapies against human bacterial and fungal infectious diseases: A review

Nations' ongoing struggles with a number of novel and reemerging infectious diseases, including the ongoing global health issue, the SARS-Co-V2 (severe acute respiratory syndrome coronavirus 2) outbreak, serve as proof that infectious diseases constitute a serious threat to the global public health. Moreover, the fatality rate in humans is rising as a result of the development of severe infectious diseases brought about by multiple drug-tolerant pathogenic microorganisms. The widespread use of traditional antimicrobial drugs, immunosuppressive medications, and other related factors led to the establishment of such drug resistant pathogenic microbial species. To overcome the difficulties commonly encountered by current infectious disease management and control processes, like inadequate effectiveness, toxicities, and the evolution of drug tolerance, new treatment solutions are required. Fortunately, immunotherapies already hold great potential for reducing these restrictions while simultaneously expanding the boundaries of healthcare and medicine, as shown by the latest discoveries and the success of drugs including monoclonal antibodies (MAbs), vaccinations, etc. Immunotherapies comprise methods for treating diseases that specifically target or affect the body's immune system and such immunological procedures/therapies strengthen the host's defenses to fight those infections. The immunotherapy-based treatments control the host's innate and adaptive immune responses, which are effective in treating different pathogenic microbial infections. As a result, diverse immunotherapeutic strategies are being researched more and more as alternative treatments for infectious diseases, leading to substantial improvements in our comprehension of the associations between pathogens and host immune system. In this review we will explore different immunotherapies and their usage for the assistance of a broad spectrum of infectious ailments caused by various human bacterial and fungal pathogenic microbes. We will discuss about the recent developments in the therapeutics against the growing human pathogenic microbial diseases and focus on the present and future of using immunotherapies to overcome these diseases. Graphical AbstractThe graphical abstract shows the therapeutic potential of different types of immunotherapies like vaccines, monoclonal antibodies-based therapies, etc., against different kinds of human Bacterial and Fungal microbial infections.

Bioinformatic survey of CRISPR loci across 15 Serratia species

The Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated proteins (CRISPR-Cas) system of prokaryotes is an adaptative immune defense mechanism to protect themselves from invading genetic elements (e.g., phages and plasmids). Studies that describe the genetic organization of these prokaryotic systems have mainly reported on the Enterobacteriaceae family (now reorganized within the order of Enterobacterales). For some genera, data on CRISPR-Cas systems remain poor, as in the case of Serratia (now part of the Yersiniaceae family) where data are limited to a few genomes of the species marcescens. This study describes the detection, in silico, of CRISPR loci in 146 Serratia complete genomes and 336 high-quality assemblies available for the species ficaria, fonticola, grimesii, inhibens, liquefaciens, marcescens, nematodiphila, odorifera, oryzae, plymuthica, proteomaculans, quinivorans, rubidaea, symbiotica, and ureilytica. Apart from subtypes I-E and I-F1 which had previously been identified in marcescens, we report that of I-C and the I-E unique locus 1, I-E*, and I-F1 unique locus 1. Analysis of the genomic contexts for CRISPR loci revealed mdtN-phnP as the region mostly shared (grimesii, inhibens, marcescens, nematodiphila, plymuthica, rubidaea, and Serratia sp.). Three new contexts detected in genomes of rubidaea and fonticola (puu genes-mnmA) and rubidaea (osmE-soxG and ampC-yebZ) were also found. The plasmid and/or phage origin of spacers was also established.

Influence of outer membrane permeabilization on intrinsic resistance to the hydrophobic biocide triclosan in opportunistic Serratia species

Triclosan is a hydrophobic antimicrobial agent commonly employed in health care settings. While it exhibits broad-spectrum antibacterial properties, the gram-negative nosocomial opportunists Pseudomonas aeruginosa and Serratia marcescens are atypically refractory. Intrinsic resistance to triclosan in P. aeruginosa is largely due to its outer membrane impermeability properties for hydrophobic and bulky substances. The present study was undertaken to determine the relationship between triclosan and the outer cell envelopes of thirteen strains of ten Serratia species reported to be opportunistic pathogens in humans. General intrinsic resistance to hydrophobic and other outer membrane impermeant compounds was assessed using cultural selection, disk agar diffusion, and macrobroth dilution bioassays. Uptake of the hydrophobic fluorescent probe 1-N-phenylnapthylamine was assessed in four disparate strains of S. marcescens. Batch culture kinetics in the presence of combinations of triclosan and outer membrane permeabilizer compound 48/80 allowed analysis of outer membrane involvement in intrinsic resistance. Aggregate results revealed that individual species ranged in response to hydrophobic and bulky molecules from generally refractory to extremely susceptible. Moreover, susceptivity to triclosan sensitization by chemical disruption of outer membrane exclusionary properties differed markedly among species which exhibited intrinsic resistance to triclosan. These data suggest that disparate opportunistic pathogens within the genus Serratia differ phenotypically regarding the degree to which outer membrane exclusion contributes to intrinsic resistance for impermeant molecules in general, and triclosan specifically. Ancillary resistance mechanisms appear to contribute in some species and may involve constitutive multi-drug efflux systems. Importance A paucity of knowledge exists regarding the cellular and molecular mechanisms by which opportunistically pathogenic members of the genus Serratia are able to infect immunocompromised and otherwise susceptible individuals, and then evade chemotherapy. This is especially true for species other than Serratia marcescens and Serratia liquefaciens, although much remains to be learned with regard to the nature of key virulence factors and infection mechanisms which allow for the typically nosocomial acquisition of even these species. The research described in the present study will provide a better understanding of the contribution of outer cell envelope permeability properties to the pathogenicity of these opportunistic species in an ever-increasing susceptible patient population. It is our hope that greater knowledge of the basic biology of these organisms will contribute to the mitigation of suffering they cause in patients with underlying diseases.

A symbiotic bacterium of Antarctic fish reveals environmental adaptability mechanisms and biosynthetic potential towards antibacterial and cytotoxic activities

Antarctic microbes are important agents for evolutionary adaptation and natural resource of bioactive compounds, harboring the particular metabolic pathways to biosynthesize natural products. However, not much is known on symbiotic microbiomes of fish in the Antarctic zone. In the present study, the culture method and whole-genome sequencing were performed. Natural product analyses were carried out to determine the biosynthetic potential. We report the isolation and identification of a symbiotic bacterium Serratia myotis L7-1, that is highly adaptive and resides within Antarctic fish, Trematomus bernacchii. As revealed by genomic analyses, Antarctic strain S. myotis L7-1 possesses carbohydrate-active enzymes (CAZymes), biosynthetic gene clusters (BGCs), stress response genes, antibiotic resistant genes (ARGs), and a complete type IV secretion system which could facilitate competition and colonization in the extreme Antarctic environment. The identification of microbiome gene clusters indicates the biosynthetic potential of bioactive compounds. Based on bioactivity-guided fractionation, serranticin was purified and identified as the bioactive compound, showing significant antibacterial and antitumor activity. The serranticin gene cluster was identified and located on the chrome. Furthermore, the multidrug resistance and strong bacterial antagonism contribute competitive advantages in ecological niches. Our results highlight the existence of a symbiotic bacterium in Antarctic fish largely represented by bioactive natural products and the adaptability to survive in the fish living in Antarctic oceans.

Serratia marcescens antibiotic resistance mechanisms of an opportunistic pathogen: a literature review

Serratia marcescens is a ubiquitous bacterium from order Enterobacterales displaying a high genetic plasticity that allows it to adapt and persist in multiple niches including soil, water, plants, and nosocomial environments. Recently, S. marcescens has gained attention as an emerging pathogen worldwide, provoking infections and outbreaks in debilitated individuals, particularly newborns and patients in intensive care units. S. marcescens isolates recovered from clinical settings are frequently described as multidrug resistant. High levels of antibiotic resistance across Serratia species are a consequence of the combined activity of intrinsic, acquired, and adaptive resistance elements. In this review, we will discuss recent advances in the understanding of mechanisms guiding resistance in this opportunistic pathogen.

Antibiotic and metal resistance of Stenotrophomonas maltophilia isolates from Eboling permafrost of the Tibetan Plateau

Whole-genome sequencing of pathogenic bacteria Stenotrophomonas maltophilia from a less polluted environment of permafrost can help understand the intrinsic resistome of both antibiotics and metals. This study aimed to examine the maximum minimum inhibitory concentration (MIC) of both antibiotics and metals, as well as antibiotic resistance genes and metal resistance genes annotated from whole-genome sequences. The permafrost S. maltophilia was sensitive to ciprofloxacin, tetracycline, streptomycin, and bacitracin, and resistant to chloramphenicol, trimethoprim-sulfamethoxazole, erythromycin, Zn²⁺, Ni²⁺, Cu²⁺, and Cr⁶⁺, with a lower maximum MIC, compared with clinical S. maltophilia. The former strain belonged to the lower antibiotic resistance gene (ARG) and metal resistance gene (MRG) clusters compared with the latter ones. The permafrost strain contained no or only one kind of ARG or MRG on a single genomic island, which explained the aforementioned lower maximum MIC and less diversity of ARGs or MRGs. The result indicated that the co-occurrence of antibiotic and metal resistance was due to a certain innate ability of S. maltophilia. The continuous human use of antibiotics or metals induced selective pressure, resulting in higher MIC and more diverse ARGs and MRGs in human-impacted environments.

Bacterial Communities and Antibiotic Resistance of Potential Pathogens Involved in Food Safety and Public Health in Fish and Water of Lake Karla, Thessaly, Greece

Bacterial communities, microbial populations, and antibiotic resistance of potential pathogens in the water and fish (Cyprinus carpio, flesh and gut) from different areas (A1, A2 and A3-A1 was linked with river water, A2 with cattle activity, and A3 with waters of a spring after heavy rains) of Lake Karla (Thessaly, Central Greece) were investigated. The isolated bacteria were identified using Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and were tested for resistance in 21 antibiotics. The microbiota composition of fish flesh was also studied using 16S amplicon-based sequencing Serratia fonticola and several species of Aeromonas (e.g., Aeromonas salmonicida, Aeromonas bestiarium, Aeromonas veronii, etc.) exhibited the highest abundances in all studied samples, while the microbiota profile between the three studied areas was similar, according to the culture-dependent analysis. Of them, S. fonticola was found to be resistant in the majority of the antibiotics for the water and fish (gut and flesh), mainly of the areas A1 and A2. Regarding 16S metabarcoding, the presence of Serratia and Aeromonas at genus level was confirmed, but they found at very lower abundances than those reported using the culture-dependent analysis. Finally, the TVC and the rest of the studied microbiological parameters were found at acceptable levels (4 log cfu/mL or cfu/g and 2-4 log cfu/mL or cfu/g, extremely low levels of E. coli/coliforms) in both water and fish flesh. Based on our findings, the water of Lake Karla would be used for activities such as irrigation, recreation and fishing, however, the development and implementation of a quality management tool for Lake Karla, to ensure environmental hygiene and prevention of zoonosis during the whole year, is imperative.

Occurrence of Serratia marcescens Carrying blaIMP-26 and mcr-9 in Southern China: New Insights in the Evolution of Megaplasmid IMP-26

The spread of multidrug-resistant enterobacteria strains has posed a significant concern in public health, especially when the strain harbors metallo-beta-lactamase (MBL)-encoding and mobilized colistin resistance (mcr) genes as such genetic components potentially mediate multidrug resistance. Here we report an IncHI2/2A plasmid carrying bla_IMP-26 and mcr-9 in multidrug-resistant Serratia marcescens human isolates YL4. Antimicrobial susceptibility testing was performed by the broth microdilution method. According to the results, S. marcescens YL4 was resistant to several antimicrobials, including β-lactams, fluorquinolones, sulfanilamide, glycylcycline, and aminoglycosides, except for amikacin. To investigate the plasmid further, we conducted whole-genome sequencing and sequence analysis. As shown, S. marcescens YL4 possessed a circular chromosome with 5,171,477 bp length and two plasmids, pYL4.1 (321,744 bp) and pYL4.2 (46,771 bp). Importantly, sharing high similarity with plasmids pZHZJ1 and pIMP-26, pYL4.1 has an IncHI2/2A backbone holding a variable region containing bla_IMP-26, mcr-9, and two copies of bla_TEM-1B. After comprehensively comparing relevant plasmids, we proposed an evolutionary pathway originating from ancestor pZHZJ1. Then, via an acquisition of the mcr-9 element and a few recombination events, this plasmid eventually evolved into pYL4.1 and pIMP-26 through two different pathways. In addition, the phage-like plasmid pYL4.2 also carried a bla_TEM-1B gene. Remarkably, this study first identified a multidrug-resistant S. marcescens strain co-harboring bla_IMP-26 and mcr-9 on a megaplasmid pYL4.1 and also included a proposed evolutionary pathway of epidemic megaplasmids carrying bla_IMP-26.

Nano-La2O3 Induces Honeybee (Apis mellifera) Death and Enriches for Pathogens in Honeybee Gut Bacterial Communities

Honeybees (Apis mellifera) can be exposed via numerous potential pathways to ambient nanoparticles (NPs), including rare earth oxide (REO) NPs that are increasingly used and released into the environment. Gut microorganisms are pivotal in mediating honeybee health, but how REO NPs may affect honeybee health and gut microbiota remains poorly understood. To address this knowledge gap, honeybees were fed pollen and sucrose syrup containing 0, 1, 10, 100, and 1000mgkg-1 of nano-La2O3 for 12days. Nano-La2O3 exerted detrimental effects on honeybee physiology, as reflected by dose-dependent adverse effects of nano-La2O3 on survival, pollen consumption, and body weight (p<0.05). Nano-La2O3 caused the dysbiosis of honeybee gut bacterial communities, as evidenced by the change of gut bacterial community composition, the enrichment of pathogenic Serratia and Frischella, and the alteration of digestion-related taxa Bombella (p<0.05). There were significant correlations between honeybee physiological parameters and the relative abundances of pathogenic Serratia and Frischella (p<0.05), underscoring linkages between honeybee health and gut bacterial communities. Taken together, this study demonstrates that nano-La2O3 can cause detrimental effects on honeybee health, potentially by disordering gut bacterial communities. This study thus reveals a previously overlooked effect of nano-La2O3 on the ecologically and economically important honeybee species Apis mellifera.

A Genome-Scale Antibiotic Screen in Serratia marcescens Identifies YdgH as a Conserved Modifier of Cephalosporin and Detergent Susceptibility

Serratia marcescens, a member of the order Enterobacterales, is adept at colonizing health care environments and is an important cause of invasive infections. Antibiotic resistance is a daunting problem in S. marcescens because, in addition to plasmid-mediated mechanisms, most isolates have considerable intrinsic resistance to multiple antibiotic classes. To discover endogenous modifiers of antibiotic susceptibility in S. marcescens, a high-density transposon insertion library was subjected to sub-MICs of two cephalosporins, cefoxitin, and cefepime, as well as the fluoroquinolone ciprofloxacin. Comparisons of transposon insertion abundance before and after antibiotic exposure identified hundreds of potential modifiers of susceptibility to these agents. Using single-gene deletions, we validated several candidate modifiers of cefoxitin susceptibility and chose ydgH, a gene of unknown function, for further characterization. In addition to cefoxitin, deletion of ydgH in S. marcescens resulted in decreased susceptibility to multiple third-generation cephalosporins and, in contrast, to increased susceptibility to both cationic and anionic detergents. YdgH is highly conserved throughout the Enterobacterales, and we observed similar phenotypes in Escherichia coli O157:H7 and Enterobacter cloacae mutants. YdgH is predicted to localize to the periplasm, and we speculate that it may be involved there in cell envelope homeostasis. Collectively, our findings provide insight into chromosomal mediators of antibiotic resistance in S. marcescens and will serve as a resource for further investigations of this important pathogen.

Molecular Characterization of Class 1, 2 and 3 Integrons in Serratia spp. Clinical Isolates in Poland - Isolation of a New Plasmid and Identification of a Gene for a Novel Fusion Protein

Purpose

Gram-negative rods of the genus Serratia play an increasing role as etiological agents of healthcare-associated infections (HAI) in humans. These bacteria are characterized by natural and acquired resistance to several groups of antibacterial agents. The aim of the study was to characterize class 1, 2 and 3 integrons in the clinical isolates of Serratia spp. in Poland.

Methods

The study comprised 112 clinical strains of Serratia, isolated from patients hospitalized in Poland in 2010-2012. Identification of strains was confirmed using MALDI-TOF MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry) system. Detection of class 1, 2 and 3 integrase DNA sequence was performed by multiplex-PCR. Amplicons obtained in the PCR reactions were purified and then sequenced bidirectionally.

Results

Among the analyzed strains, Serratia marcescens was a predominant species (103/112, 92.0%). All three classes of integrase DNA sequence were detected in the analyzed strains of Serratia spp. DNA sequence of class 3 integron, besides integrase gene, revealed three gene cassettes (dfrB3, bla _GES-7,bla _{OXA/aac(6')-Ib-cr}). BLAST analysis of DNA sequence revealed that class 3 integron was carried on 9448 bp plasmid which was named pPCMI3 - whole sequence of its DNA was submitted to GenBank NCBI (National Center for Biotechnology Information) - NCBI MH569711.

Conclusion

In this study, we identified a new plasmid pPCMI3 harboring class 3 integron. This is the first report of a gene oxa/aac(6')-Ib-cr coding for a novel fusion protein, which consists of OXA β-lactamase and acetyltransferase aac(6')-Ib-cr. In the analyzed strains, class 1 and 2 integrons were also detected. Among the strains with class 1 integron, nine contained cassette array 5'CS-aadA2-ORF-dfrA12-3'CS, and two - cassette array 5'CS-aacC1-ORF-ORF-aadA1-3'CS, which were not previously reported in Serratia spp.

First Report of bla IMP-4 and bla SRT-2 Coproducing Serratia marcescens Clinical Isolate in China

Carbapenem-resistant Enterobacterales (CRE) has become a major therapeutic concern in clinical settings, and carbapenemase genes have been widely reported in various bacteria. In Serratia marcescens, class A group carbapenemases including SME and KPC were mostly identified. However, there are few reports of metallo-β-lactamase-producing S. marcescens. Here, we isolated a carbapenem-resistant S. marcescens (S378) from a patient with asymptomatic urinary tract infection which was then identified as an IMP-4-producing S. marcescens at a tertiary hospital in Sichuan Province in southwest of China. The species were identified using MALDI-TOF MS, and carbapenemase-encoding genes were detected using PCR and DNA sequencing. The results of antimicrobial susceptibility testing by broth microdilution method indicated that the isolate S. marcescens S378 was resistant to meropenem (MIC = 32 μg/ml) and imipenem (MIC = 64 μg/ml) and intermediate to aztreonam (MIC = 8 μg/ml). The complete genomic sequence of S. marcescens was identified using Illumina (Illumina, San Diego, CA, United States) short-read sequencing (150 bp paired-end reads); five resistance genes had been identified, including bla_IMP–4, bla_SRT–2, aac(6′)-Ic, qnrS1, and tet(41). Conjugation experiments indicated that the bla_IMP–4-carrying plasmid pS378P was conjugative. Complete sequence analysis of the plasmid pS378P bearing bla_IMP–4 revealed that it was a 48,780-bp IncN-type plasmid with an average GC content of 50% and was nearly identical to pP378-IMP (99% nucleotide identity and query coverage).

Bacterial Antibiotic Resistance: The Most Critical Pathogens

Antibiotics have made it possible to treat bacterial infections such as meningitis and bacteraemia that, prior to their introduction, were untreatable and consequently fatal. Unfortunately, in recent decades overuse and misuse of antibiotics as well as social and economic factors have accelerated the spread of antibiotic-resistant bacteria, making drug treatment ineffective. Currently, at least 700,000 people worldwide die each year due to antimicrobial resistance (AMR). Without new and better treatments, the World Health Organization (WHO) predicts that this number could rise to 10 million by 2050, highlighting a health concern not of secondary importance. In February 2017, in light of increasing antibiotic resistance, the WHO published a list of pathogens that includes the pathogens designated by the acronym ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) to which were given the highest "priority status" since they represent the great threat to humans. Understanding the resistance mechanisms of these bacteria is a key step in the development of new antimicrobial drugs to tackle drug-resistant bacteria. In this review, both the mode of action and the mechanisms of resistance of commonly used antimicrobials will be examined. It also discusses the current state of AMR in the most critical resistant bacteria as determined by the WHO's global priority pathogens list.

Bacterial Antibiotic Resistance: The Most Critical Pathogens

Antibiotics have made it possible to treat bacterial infections such as meningitis and bacteraemia that, prior to their introduction, were untreatable and consequently fatal. Unfortunately, in recent decades overuse and misuse of antibiotics as well as social and economic factors have accelerated the spread of antibiotic-resistant bacteria, making drug treatment ineffective. Currently, at least 700,000 people worldwide die each year due to antimicrobial resistance (AMR). Without new and better treatments, the World Health Organization (WHO) predicts that this number could rise to 10 million by 2050, highlighting a health concern not of secondary importance. In February 2017, in light of increasing antibiotic resistance, the WHO published a list of pathogens that includes the pathogens designated by the acronym ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) to which were given the highest "priority status" since they represent the great threat to humans. Understanding the resistance mechanisms of these bacteria is a key step in the development of new antimicrobial drugs to tackle drug-resistant bacteria. In this review, both the mode of action and the mechanisms of resistance of commonly used antimicrobials will be examined. It also discusses the current state of AMR in the most critical resistant bacteria as determined by the WHO's global priority pathogens list.

Whole Genome Sequencing of Extended-Spectrum- and AmpC- β-Lactamase-Positive Enterobacterales Isolated From Spinach Production in Gauteng Province, South Africa

The increasing occurrence of multidrug-resistant (MDR) extended-spectrum β-lactamase- (ESBL) and/or AmpC β-lactamase- (AmpC) producing Enterobacterales in irrigation water and associated irrigated fresh produce represents risks related to the environment, food safety, and public health. In South Africa, information about the presence of ESBL/AmpC-producing Enterobacterales from non-clinical sources is limited, particularly in the water-plant-food interface. This study aimed to characterize 19 selected MDR ESBL/AmpC-producing Escherichia coli (n=3), Klebsiella pneumoniae (n=5), Serratia fonticola (n=10), and Salmonella enterica (n=1) isolates from spinach and associated irrigation water samples from two commercial spinach production systems within South Africa, using whole genome sequencing (WGS). Antibiotic resistance genes potentially encoding resistance to eight different classes were present, with bla CTX-M-15 being the dominant ESBL encoding gene and bla ACT-types being the dominant AmpC encoding gene detected. A greater number of resistance genes across more antibiotic classes were seen in all the K. pneumoniae strains, compared to the other genera tested. From one farm, bla CTX-M-15-positive K. pneumoniae strains of the same sequence type 985 (ST 985) were present in spinach at harvest and retail samples after processing, suggesting successful persistence of these MDR strains. In addition, ESBL-producing K. pneumoniae ST15, an emerging high-risk clone causing nosocomical outbreaks worldwide, was isolated from irrigation water. Known resistance plasmid replicon types of Enterobacterales including IncFIB, IncFIA, IncFII, IncB/O, and IncHI1B were observed in all strains following analysis with PlasmidFinder. However, bla CTX-M-15 was the only β-lactamase resistance gene associated with plasmids (IncFII and IncFIB) in K. pneumoniae (n=4) strains. In one E. coli and five K. pneumoniae strains, integron In191 was observed. Relevant similarities to human pathogens were predicted with PathogenFinder for all 19 strains, with a confidence of 0.635-0.721 in S. fonticola, 0.852-0.931 in E. coli, 0.796-0.899 in K. pneumoniae, and 0.939 in the S. enterica strain. The presence of MDR ESBL/AmpC-producing E. coli, K. pneumoniae, S. fonticola, and S. enterica with similarities to human pathogens in the agricultural production systems reflects environmental and food contamination mediated by anthropogenic activities, contributing to the spread of antibiotic resistance genes.

The global population structure and beta-lactamase repertoire of the opportunistic pathogen Serratia marcescens

Serratia marcescens is a global spread nosocomial pathogen. This rod-shaped bacterium displays a broad host range and worldwide geographical distribution. Here we analyze an international collection of this multidrug-resistant, opportunistic pathogen from 35 countries to infer its population structure. We show that S. marcescens comprises 12 lineages; Sm1, Sm4, and Sm10 harbor 78.3% of the known environmental strains. Sm5, Sm6, and Sm7 comprise only human-associated strains which harbor smallest pangenomes, genomic fluidity and lowest levels of core recombination, indicating niche specialization. Sm7 and Sm9 lineages exhibit the most concerning resistome; bla_KPC-2 plasmid is widespread in Sm7, whereas Sm9, also an anthropogenic-exclusive lineage, presents highest plasmid/lineage size ratio and plasmid-diversity encoding metallo-beta-lactamases comprising bla_NDM-1. The heterogeneity of resistance patterns of S. marcescens lineages elucidated herein highlights the relevance of surveillance programs, using whole-genome sequencing, to provide insights into the molecular epidemiology of carbapenemase producing strains of this species.

The Virulence of S. marcescens Strains Isolated From Contaminated Blood Products Is Divergent in the C. elegans Infection Model

Bacterial contamination of platelet concentrates (PCs) can occur during blood donation or PC processing, necessitating routine screening to identify contaminated products in efforts to prevent adverse transfusion reactions in recipient patients. Serratia marcescens is a common bacterial contaminant, and its resilient nature coupled with genetic promiscuity imbue this environmental bacterium with resistance to disinfectants and antibiotics enhancing bacterial virulence. In this study, we aim to understand adaptive survival mechanisms through genetic characterization of two S. marcescens strains, CBS11 and CBS12, isolated from PCs by Canadian Blood Services. Genomic analyses of the two strains indicated that CBS11 has one chromosome and one plasmid (pAM01), whereas CBS12 has no plasmids. Phylogenetic analyses show that CBS11 and CBS12 are non-clonal strains, with CBS11 clustering closely with clinical strain CAV1492 and less so with environmental strain PWN146, and CBS12 clustering with a clinical strain AR_0027. Interestingly, pAM01 was most closely related to PWN146p1, a plasmid found in S. marcescens PWN146 strain associated with pinewood nematode Bursaphelenchus xylophilus. Lastly, the genomic diversity of CBS11 and CBS12 was not reflected in the antibiotic resistance profiles as they were remarkably similar to one another, but was reflected in the virulence phenotypes assessed in the Caenorhabditis elegans nematode infection model, with CBS11 being more virulent then CBS12. Taken together, we suggest that S. marcescens environmental isolates that feature evolutionary diverse genomics are better equipped to adapt and thrive in varied environments, such as that of PCs, and therefore is as much of a concern as multi-drug resistance for human infection potential.

Defining chaperone-usher fimbriae repertoire in Serratia marcescens

Chaperone-usher (CU) fimbriae are surface organelles particularly prevalent among the Enterobacteriaceae. Mainly associated to their adhesive properties, CU fimbriae play key roles in biofilm formation and host cell interactions. Little is known about the fimbriome composition of the opportunistic human pathogen Serratia marcescens. Here, by using a search based on consensus fimbrial usher protein (FUP) sequences, we identified 421 FUPs across 39 S. marcescens genomes. Further analysis of the FUP-containing loci allowed us to classify them into 20 conserved CU operons, 6 of which form the S. marcescens core CU fimbriome. A new systematic nomenclature is proposed according to FUP sequence phylogeny. We also established an in vivo transcriptional assay comparing CU promoter expression between an environmental and a clinical isolate of S. marcescens, which revealed that promoters from 3 core CU operons (referred as fgov, fpo, and fps) are predominantly expressed in the two strains and might represent key core adhesion appendages contributing to S. marcescens pathogenesis.

Recent Trends on Biosurfactants With Antimicrobial Activity Produced by Bacteria Associated With Human Health: Different Perspectives on Their Properties, Challenges, and Potential Applications

The attention towards the bacteria associated with human health is growing more and more, above all regarding the bacteria that inhabit the niches offered by the human body, i.e., the gastrointestinal tract, skin, vaginal environment, and lungs. Among the secondary metabolites released by microorganisms associated with human health, little consideration is given to the biosurfactants, molecules with both hydrophobic and hydrophilic nature. Their role in the complex human environment is not only the mere biosurfactant function, but they could also control the microbiota through the quorum sensing system and the antimicrobial activity. These functions protect them and, accordingly, the human body principally from microbial and fungal pathogens. Consequently, nowadays, biosurfactants are emerging as promising bioactive molecules due to their very different structures, biological functions, low toxicity, higher biodegradability, and versatility. Therefore, this review provides a comprehensive perspective of biosurfactants with antimicrobial activity produced by bacteria associated with the human body and related to everything human beings are in contact with, e.g., food, beverages, and food-waste dumping sites. For the first time, the role of an "-omic" approach is highlighted to predict gene products for biosurfactant production, and an overview of the available gene sequences is reported. Besides, antimicrobial biosurfactants' features, challenges, and potential applications in the biomedical, food, and nutraceutical industries are discussed.

Antimicrobials Affect the Fat Body Microbiome and Increase the Brown Planthopper Mortality

Symbionts in the abdomen fat body of brown planthopper (BPH) play an important role in the growth and reproduction of their host, Nilaparvata lugens Stål (Hemiptera: Delphacidae). Thus, controlling BPH infection on rice by inhibiting symbionts with antimicrobials is feasible. However, the effect of antimicrobials on the microbiome in the fat body and the relationship between microbial community and mortality have not been fully elucidated. A decrease in the total number of yeast-like symbiotes in the fat body and elevated mortality were observed after exposure to toyocamycin, tebuconazole, and zhongshengmycin. Additionally, we found that the antimicrobials reduced bacterial diversity and increased fungal diversity in the fat body and altered the bacterial and fungal community structure. Although the total absolute abundance of bacteria and fungi decreased after antimicrobial exposure, the absolute abundance of Serratia increased, indicating that Serratia, which was the most dominant in the fat body, is an important symbiont involved in resistance to antimicrobials. After antimicrobial exposure, seven genera, which probably participated in the nutrition and development function of the host, were totally eliminated from the fat body. Overall, our study enriches the knowledge of microbiomes in the fat body of BPH under antimicrobial treatment and the disturbance of symbionts would be further used to help other pesticides to control pests.

The ABC-Type Efflux Pump MacAB Is Involved in Protection of Serratia marcescens against Aminoglycoside Antibiotics, Polymyxins, and Oxidative Stress

Serratia marcescens is an emerging pathogen with increasing clinical importance due to its intrinsic resistance to several classes of antibiotics. The chromosomally encoded drug efflux pumps contribute to antibiotic resistance and represent a major challenge for the treatment of bacterial infections. The ABC-type efflux pump MacAB was previously linked to macrolide resistance in Escherichia coli and Salmonella enterica serovar Typhimurium. The role of the MacAB homolog in antibiotic resistance of S. marcescens is currently unknown. We found that an S. marcescens mutant lacking the MacAB pump did not show increased sensitivity to the macrolide antibiotic erythromycin but was significantly more sensitive to aminoglycoside antibiotics and polymyxins. We also showed that, in addition to its role in drug efflux, the MacAB efflux pump is required for swimming motility and biofilm formation. We propose that the motility defect of the ΔmacAB mutant is due, at least in part, to the loss of functional flagella on the bacterial surface. Furthermore, we found that the promoter of the MacAB efflux pump was active during the initial hours of growth in laboratory medium and that its activity was further elevated in the presence of hydrogen peroxide. Finally, we demonstrate a complete loss of ΔmacAB mutant viability in the presence of peroxide, which is fully restored by complementation. Thus, the S. marcescens MacAB efflux pump is essential for survival during oxidative stress and is involved in protection from polymyxins and aminoglycoside antibiotics.

IMPORTANCE The opportunistic pathogen Serratia marcescens can cause urinary tract infections, respiratory infections, meningitis, and sepsis in immunocompromised individuals. These infections are challenging to treat due to the intrinsic resistance of S. marcescens to an extensive array of antibiotics. Efflux pumps play a crucial role in protection of bacteria from antimicrobials. The MacAB efflux pump, previously linked to efflux of macrolides in Escherichia coli and protection from oxidative stress in Salmonella enterica serovar Typhimurium, is not characterized in S. marcescens. We show the role of the MacAB efflux pump in S. marcescens protection from aminoglycoside antibiotics and polymyxins, modulation of bacterial motility, and biofilm formation, and we illustrate the essential role for this pump in bacterial survival during oxidative stress. Our findings make the MacAB efflux pump an attractive target for inhibition to gain control over S. marcescens infections.

Ambigols from the Cyanobacterium Fischerella ambigua Increase Prodigiosin Production in Serratia spp

When a library of 573 cyanobacteria extracts was screened for inhibition of the quorum sensing regulated prodigiosin production of Serratia marcescens, an extract of the cyanobacterium Fischerella ambigua (Näg.) Gomont 108b was found to drastically increase prodigiosin production. Bioactivity-guided isolation of the active compounds resulted in the two new natural products ambigol D and E along with the known ambigols A and C. Ambigol C treatment increased prodiginine production of Serratia sp. ATCC 39006 (S39006) by a factor of 10, while ambigols A and D were found to have antibiotic activity against this strain. The RNA-Seq of S39006 treated with ambigol C and subsequent differential gene expression and functional enrichment analyses indicated a significant downregulation of genes associated with the translation machinery and fatty acid biosynthesis in Serratia, as well as increased expression of genes related to the uptake of l-proline. These results suggest that the ambigols increase prodiginine production in S39006 not by activating the SmaIR quorum sensing system but possibly by increasing the precursor supply of l-proline and malonyl-CoA.

Is Long-Term Heavy Metal Exposure Driving Carriage of Antibiotic Resistance in Environmental Opportunistic Pathogens: A Comprehensive Phenomic and Genomic Assessment Using Serratia sp. SRS-8-S-2018

The carriage of both, heavy metal and antibiotic resistance appears to be a common trait in bacterial communities native to long-term contaminated habitats, including the Savannah River Site (SRS). There is widespread soil contamination at the SRS; a United States Department of Energy (DOE) facility with long-term contamination from past industrial and nuclear weapons production activities. To further evaluate the genomic and metabolic traits that underpin metal and antibiotic resistance, a robust mercury (Hg) and uranium (U)-resistant strain- SRS-8-S-2018, was isolated. Minimum inhibitory concentration of this strain revealed resistance to Hg (10 μg/ml) and U (5 mM), the two main heavy metal contaminants at the SRS. Metabolic assessment of strain SRS-8-S-2018 using Biolog metabolic fingerprinting analysis revealed preference for carbohydrate utilization followed by polymers, amino acids, carboxy acids, and esters; this physiological activity diminished when Hg stress was provided at 1 and 3 μg/ml and completely ceased at 5 μg/ml Hg, indicating that continued release of Hg will have negative metabolic impacts to even those microorganisms that possess high resistance ability. Development of antibiotic resistance in strain SRS-8-S-2018 was evaluated at a functional level using phenomics, which confirmed broad resistance against 70.8% of the 48 antibiotics tested. Evolutionary and adaptive traits of strain SRS-8-S-2018 were further assessed using genomics, which revealed the strain to taxonomically affiliate with Serratia marcescens species, possessing a genome size of 5,323,630 bp, 5,261 proteins (CDS), 55 genes for transfer RNA (tRNA), and an average G + C content of 59.48. Comparative genomics with closest taxonomic relatives revealed 360 distinct genes in SRS-8-S-2018, with multiple functions related to both, antibiotic and heavy metal resistance, which likely facilitates the strain’s survival in a metalliferous soil habitat. Comparisons drawn between the environmentally isolated Serratia SRS-8-S-2018 with 31 other strains revealed a closer functional association with medically relevant isolates suggesting that propensity of environmental Serratia isolates in acquiring virulence traits, as a function of long-term exposure to heavy metals, which is facilitating development, recruitment and proliferation of not only metal resistant genes (MRGs) but antibiotic resistant genes (ARGs), which can potentially trigger future bacterial pathogen outbreaks emanating from contaminated environmental habitats.

Alternative drugs against multiresistant Gram-negative bacteria

OBJECTIVES

Enterobacterales and other non-fermenting Gram-negative bacteria have become a threat worldwide owing to the frequency of multidrug resistance in these pathogens. On the other hand, efficacious therapeutic options are quickly diminishing. The aims of this study were to describe the susceptibility of 50 multiresistant Gram-negative bacteria, mostly pan-resistant, against old and less-used antimicrobial drugs and to investigate the presence of antimicrobial resistance genes.

METHODS

A total of 50 genetically distinct isolates were included in this study, including 14 Acinetobacter baumannii (belonging to ST79, ST317, ST835 and ST836), 1 Pseudomonas aeruginosa (ST245), 8 Serratia marcescens and 27 Klebsiella pneumoniae (belonging to ST11, ST340, ST258, ST16, ST23, ST25, ST101, ST234, ST437 and ST442). The isolates were submitted to antimicrobial susceptibility testing and whole-genome sequencing to evaluate lineages and resistance genes.

RESULTS

Our results showed that some strains harboured carbapenemase genes, e.g. bla_KPC-2 (28/50; 56%) and bla_OXA-23 (11/50; 22%), and other resistance genes encoding aminoglycoside-modifying enzymes (49/50; 98%). Susceptibility rates to tigecycline (96%) in all species (except P. aeruginosa), to minocycline (100%) and doxycycline (93%) in A. baumannii, to ceftazidime/avibactam in S. marcescens (100%) and K. pneumoniae (96%), and to fosfomycin in S. marcescens (88%) were high. Chloramphenicol and quinolones (6% susceptibility each) did not perform well, making their use in an empirical scenario unlikely.

CONCLUSIONS

This study involving genetically distinct bacteria showed promising results for tigecycline for all Gram-negative bacteria (except P. aeruginosa), and there was good activity of minocycline against A. baumannii, ceftazidime/avibactam against Enterobacterales, and fosfomycin against S. marcescens.

Characterization of KPC-Producing Serratia marcescens in an Intensive Care Unit of a Brazilian Tertiary Hospital

Serratia marcescens has emerged as an important opportunistic pathogen responsible for nosocomial and severe infections. Here, we determined phenotypic and molecular characteristics of 54 S. marcescens isolates obtained from patient samples from intensive-care-unit (ICU) and neonatal intensive-care-unit (NIUC) of a Brazilian tertiary hospital. All isolates were resistant to beta-lactam group antibiotics, and 92.6% (50/54) were not susceptible to tigecycline. Furthermore, 96.3% showed intrinsic resistance to polymyxin E (colistin), a last-resort antibiotic for the treatment of infections caused by MDR (multidrug-resistant) Gram-negative bacteria. In contrast, high susceptibility to other antibiotics such as fluoroquinolones (81.5%), and to aminoglycosides (as gentamicin 81.5%, and amikacin 85.2%) was found. Of all isolates, 24.1% were classified as MDR. The presence of resistance and virulence genes were examined by PCR and sequencing. All isolates carried KPC-carbapenemase (bla_KPC) and extended spectrum beta-lactamase bla_TEM genes, 14.8% carried bla_OXA–1, and 16.7% carried bla_{CTX–M–1group} genes, suggesting that bacterial resistance to β-lactam antibiotics found may be associated with these genes. The genes SdeB/HasF and SdeY/HasF that are associated with efflux pump mediated drug extrusion to fluoroquinolones and tigecycline, respectively, were found in 88.9%. The aac(6′)-Ib-cr variant gene that can simultaneously induce resistance to aminoglycoside and fluoroquinolone was present in 24.1% of the isolates. Notably, the virulence genes to (i) pore-forming toxin (ShlA); (ii) phospholipase with hemolytic and cytolytic activities (PhlA); (iii) flagellar transcriptional regulator (FlhD); and (iv) positive regulator of prodigiosin and serratamolide production (PigP) were present in 98.2%. The genetic relationship among the isolates determined by ERIC-PCR demonstrated that the vast majority of isolates were grouped in a single cluster with 86.4% genetic similarity. In addition, many isolates showed 100% genetic similarity to each other, suggesting that the S. marcescens that circulate in this ICU are closely related. Our results suggest that the antimicrobial resistance to many drugs currently used to treat ICU and NIUC patients, associated with the high frequency of resistance and virulence genes is a worrisome phenomenon. Our findings emphasize the importance of active surveillance plans for infection control and to prevent dissemination of these strains.

Genomics of Serratia marcescens Isolates Causing Outbreaks in the Same Pediatric Unit 47 Years Apart: Position in an Updated Phylogeny of the Species

The first documented nosocomial outbreak caused by Serratia marcescens in Spain occurred in 1969 at the neonatal intensive care unit (NICU) of the tertiary La Paz Children's Hospital in Madrid, Spain, and based on the available phenotyping techniques at this time, it was considered as a monoclonal outbreak. Only 47 years later, another S. marcescens outbreak of an equivalent dimension occurred at the same NICU. The aim of the present study was to study isolates from these historical and contemporary outbreaks by phenotypic analysis and whole-genome sequencing techniques and to position these strains along with 444 publicly available S. marcescens genomes, separately comparing core genome and accessory genome contents. Clades inferred by both approaches showed high correlation, indicating that core and accessory genomes seem to evolve in the same manner for S. marcescens. Nine S. marcescens clusters were identified, and isolates were grouped in two of them according to sampling year. One exception was isolate 13F-69, the most genetically distant strain, located in a different cluster. Categorical functions in the annotated accessory genes of both collections were preserved among all isolates. No significant differences in frequency of insertion sequences in historical (0.18-0.20)-excluding the outlier strain-versus contemporary isolates (0.11-0.19) were found despite the expected resting effect. The most dissimilar isolate, 13F-69, contains a highly preserved plasmid previously described in Bordetella bronchiseptica. This strain exhibited a few antibiotic resistance genes not resulting in a resistant phenotype, suggesting the value of gene down expression in adaptation to long-term starvation.

Different Effects Of Amniotic Membrane Homogenate On The Growth Of Uropathogenic Escherichia coli, Staphylococcus aureus And Serratia marcescens

PURPOSE

Due to the emergence and spread of bacterial strains resistant to antibiotics, the development of new antimicrobials is imperative. The antimicrobial effect of the amniotic membrane (AM) has been explored to a limited extent so far.

MATERIALS AND METHODS

We collected 12 biological samples of AM homogenates and tested their antimicrobial effect on 4 pathogens, including the clinical strain of uropathogenic Escherichia coli (UPEC), the wild-type strain of Staphylococcus aureus, and the wild-type strain and a clinical strain of Serratia marcescens. To quantify the antibacterial effect of AM, we monitored the effect of AM homogenate on bacterial growth using plate count method and agar diffusion method. Additionally, minimal inhibitory concentrations (MICs) for AM homogenate dilutions were determined and S. marcescens growth in AM homogenate alone was evaluated.

RESULTS

Our results demonstrated that AM homogenate had a bacteriostatic effect on studied UPEC and S. aureus. Interestingly, when used in lower concentrations, the AM homogenate had a bactericidal effect on both strains. In contrast, S. marcescens was completely resistant to the growth-inhibitory substances of AM homogenate. Its growth was slightly accelerated in liquid culture medium in the presence of AM homogenate and the strain was able to grow in undiluted, 2-fold and 4-fold diluted AM homogenate.

CONCLUSION

Obtained results illustrated that AM homogenate could be a candidate for treatments and prevention of UPEC and S. aureus infections, but not that of S. marcescens, whose growth is enhanced by AM homogenate. Moreover, the established liquid culture medium assay can be used as a time- and cost-effective method for a personalized evaluation of drug effect on the growth of chosen bacterial strains with parallel testing of resistance or susceptibility to multiple drugs. The susceptibility of bacteria to AM homogenate in solid and liquid culture media is encouraging for its use in biomedical applications.

Developmental dynamics of antibiotic resistome in aerobic biofilm microbiota treating wastewater under stepwise increasing tigecycline concentrations

This study aimed to investigate the impact of tigecycline, the third generation tetracycline, on the antibiotic resistance development in environmental microbiota. Two biological contact oxidation reactors containing aerobic biofilm microbiota were constructed, one of which was constantly fed with synthetic wastewater spiked with increasing concentrations of tigecycline (0 to 25 mg/L) under a hydrolytic retention time of 24 h. Over a period of 636 days, chemical oxygen demand removal over 90% and complete nitrification were achieved for both the control and tigecycline-exposed reactors, and effluent tigecycline concentrations in the tigecycline-exposed system were always <0.051 mg/L. Significant increases (p < 0.01) in resistome abundance and resistant bacteria ratio were detected at a tigecycline dose of 10 and 25 mg/L, respectively, revealed by metagenomic sequencing and culture-based method. The increase of resistome in the tigecycline system was mainly attributed to the enrichment of tetX, one cooperative tetracycline degrading gene. Partial canonical correspondence analysis showed that the change of resistome was mainly driven by bacterial community shift (vertical pathway). Network and genome binning analyses further suggested that the proliferation of Flavobacterium harboring tetX contributed to a relatively low community-wide resistance development in the aerobic biofilm microbiota under tigecycline selection by reducing the antibiotic concentration. This work provides scientific bases for the management and evaluation of the resistance risk induced by this novel antibiotic.

Characterization of CRISPR-Cas Systems in Serratia marcescens Isolated from Rhynchophorus ferrugineus (Olivier, 1790) (Coleoptera: Curculionidae)

The CRISPR-Cas adaptive immune system has been attracting increasing scientific interest for biological functions and biotechnological applications. Data on the Serratia marcescens system are scarce. Here, we report a comprehensive characterisation of CRISPR-Cas systems identified in S. marcescens strains isolated as secondary symbionts of Rhynchophorus ferrugineus, also known as Red Palm Weevil (RPW), one of the most invasive pests of major cultivated palms. Whole genome sequencing was performed on four strains (S1, S5, S8, and S13), which were isolated from the reproductive apparatus of RPWs. Subtypes I-F and I-E were harboured by S5 and S8, respectively. No CRISPR-Cas system was detected in S1 or S13. Two CRISPR arrays (4 and 51 spacers) were detected in S5 and three arrays (11, 31, and 30 spacers) were detected in S8. The CRISPR-Cas systems were located in the genomic region spanning from ybhR to phnP, as if this were the only region where CRISPR-Cas loci were acquired. This was confirmed by analyzing the S. marcescens complete genomes available in the NCBI database. This region defines a genomic hotspot for horizontally acquired genes and/or CRISPR-Cas systems. This study also supplies the first identification of subtype I-E in S. marcescens.

Whole genome sequence of moderate halophilic marine bacterium Marinobacter litoralis SW-45: Abundance of non-coding RNAs

A report on the de novo Whole Genome Sequence (WGS) of Marinobacter litoralis SW-45, a moderately salt-tolerant bacterium isolated from the seawater in Malaysia is presented. The strain has a genome size of 3.45 Mb and is capable of producing halophilic lipase, protease and esterase enzymes. Computational prediction of non-coding RNA (ncRNA) genes in M. litoralis SW-45 was performed using standalone software known as the non-coding RNA characterization (nocoRNAc). In addition, a phylogenetic tree showing the evolutionary relationship between the strain and other members of the genus Marinobacter was constructed using 16SrRNA sequence information. A total of 385 ncRNA transcripts, 1124 terminator region, and 2350 Stress Induced Duplex Destabilization sites were predicted. The current WGS shotgun project has provided the relevant genetic information that may be useful for the strain's improvement studies. This manuscript gives the first description of M. litoralis with a complete genome.