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1.
Nat Commun ; 15(1): 3947, 2024 May 10.
Article En | MEDLINE | ID: mdl-38729951

Gram-negative bacteria (GNB) are a major cause of neonatal sepsis in low- and middle-income countries (LMICs). Although the World Health Organization (WHO) reports that over 80% of these sepsis deaths could be prevented through improved treatment, the efficacy of the currently recommended first- and second-line treatment regimens for this condition is increasingly affected by high rates of drug resistance. Here we assess three well known antibiotics, fosfomycin, flomoxef and amikacin, in combination as potential antibiotic treatment regimens by investigating the drug resistance and genetic profiles of commonly isolated GNB causing neonatal sepsis in LMICs. The five most prevalent bacterial isolates in the NeoOBS study (NCT03721302) are Klebsiella pneumoniae, Acinetobacter baumannii, E. coli, Serratia marcescens and Enterobacter cloacae complex. Among these isolates, high levels of ESBL and carbapenemase encoding genes are detected along with resistance to ampicillin, gentamicin and cefotaxime, the current WHO recommended empiric regimens. The three new combinations show excellent in vitro activity against ESBL-producing K. pneumoniae and E. coli isolates. Our data should further inform and support the clinical evaluation of these three antibiotic combinations for the treatment of neonatal sepsis in areas with high rates of multidrug-resistant Gram-negative bacteria.


Acinetobacter baumannii , Anti-Bacterial Agents , Gram-Negative Bacteria , Gram-Negative Bacterial Infections , Klebsiella pneumoniae , Microbial Sensitivity Tests , Neonatal Sepsis , Humans , Anti-Bacterial Agents/therapeutic use , Anti-Bacterial Agents/pharmacology , Neonatal Sepsis/microbiology , Neonatal Sepsis/drug therapy , Infant, Newborn , Gram-Negative Bacteria/drug effects , Gram-Negative Bacteria/genetics , Gram-Negative Bacteria/isolation & purification , Gram-Negative Bacterial Infections/drug therapy , Gram-Negative Bacterial Infections/microbiology , Acinetobacter baumannii/drug effects , Acinetobacter baumannii/isolation & purification , Acinetobacter baumannii/genetics , Klebsiella pneumoniae/drug effects , Klebsiella pneumoniae/isolation & purification , Klebsiella pneumoniae/genetics , Amikacin/pharmacology , Amikacin/therapeutic use , Fosfomycin/pharmacology , Fosfomycin/therapeutic use , beta-Lactamases/genetics , beta-Lactamases/metabolism , Escherichia coli/drug effects , Escherichia coli/genetics , Escherichia coli/isolation & purification , Developing Countries , Drug Resistance, Multiple, Bacterial/genetics , Drug Therapy, Combination , Serratia marcescens/drug effects , Serratia marcescens/genetics , Serratia marcescens/isolation & purification , Enterobacter cloacae/drug effects , Enterobacter cloacae/genetics , Enterobacter cloacae/isolation & purification , Bacterial Proteins/genetics , Bacterial Proteins/metabolism
2.
FEBS J ; 291(9): 1958-1973, 2024 May.
Article En | MEDLINE | ID: mdl-38700222

Serratia marcescens is an emerging health-threatening, gram-negative opportunistic pathogen associated with a wide variety of localized and life-threatening systemic infections. One of the most crucial virulence factors produced by S. marcescens is serratiopeptidase, a 50.2-kDa repeats-in-toxin (RTX) family broad-specificity zinc metalloprotease. RTX family proteins are functionally diverse exoproteins of gram-negative bacteria that exhibit calcium-dependent structural dynamicity and are secreted through a common type-1 secretion system (T1SS) machinery. To evaluate the impact of various divalent ligands on the folding and maturation of serratiopeptidase zymogen, the protein was purified and a series of structural and functional investigations were undertaken. The results indicate that calcium binding to the C-terminal RTX domain acts as a folding switch, triggering a disordered-to-ordered transition in the enzyme's conformation. Further, the auto-processing of the 16-amino acid N-terminal pro-peptide results in the maturation of the enzyme. The binding of calcium ions to serratiopeptidase causes a highly cooperative conformational transition in its structure, which is essential for the enzyme's activation and maturation. This conformational change is accompanied by an increase in solubility and enzymatic activity. For efficient secretion and to minimize intracellular toxicity, the enzyme needs to be in an unfolded extended form. The calcium-rich extracellular environment favors the folding and processing of zymogen into mature serratiopeptidase, i.e., the holo-form required by S. marcescens to establish infections and survive in different environmental niches.


Calcium , Enzyme Precursors , Peptide Hydrolases , Protein Folding , Serratia marcescens , Calcium/metabolism , Serratia marcescens/enzymology , Serratia marcescens/genetics , Enzyme Precursors/metabolism , Enzyme Precursors/chemistry , Enzyme Precursors/genetics , Metalloendopeptidases/chemistry , Metalloendopeptidases/metabolism , Metalloendopeptidases/genetics , Models, Molecular , Protein Conformation , Bacterial Proteins/chemistry , Bacterial Proteins/metabolism , Bacterial Proteins/genetics , Protein Binding
3.
Cell Biochem Funct ; 42(4): e4032, 2024 Jun.
Article En | MEDLINE | ID: mdl-38736209

Polymerase chain reaction (PCR) is an important tool for exogenous gene acquisition and recombinants identification. There exist two problems when using Serratia marcescens as a template for PCR amplification: amplified PCR products are rapidly degraded, and the results of PCR amplification are unstable. The aim of the present work was to elucidate the reasons for this. By mixing PCR products amplified from Escherichia coli DH5α with S. marcescens supernatant or pellet, we found that the DNA-degrading substance in S. marcescens is thermally resistant and present both intracellularly and extracellularly. We then determined that it is protein, and most likely S. marcescens nuclease, that degrades PCR products since the addition of SDS and EDTA can effectively inhibit or block the degradation of PCR products. By knocking out the S. marcescens nuclease encoding gene, nucA, we confirmed that the nuclease is responsible for the degradation of PCR products and the instability of PCR amplification. This work is the first to show that the S. marcescens nuclease is temporarily and partially inhibited by high temperatures during PCR and recovers rapidly at room temperature after PCR.


Polymerase Chain Reaction , Serratia marcescens , Serratia marcescens/enzymology , Serratia marcescens/genetics , Serratia marcescens/metabolism , Bacterial Proteins/metabolism , Bacterial Proteins/genetics , Escherichia coli/metabolism , Escherichia coli/genetics , Hot Temperature , Temperature
4.
mBio ; 15(5): e0305423, 2024 May 08.
Article En | MEDLINE | ID: mdl-38564701

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 ß-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.


Cross Infection , Intensive Care Units , Serratia Infections , Serratia marcescens , Serratia marcescens/genetics , Serratia marcescens/isolation & purification , Serratia marcescens/classification , Serratia Infections/epidemiology , Serratia Infections/microbiology , Humans , Cross Infection/microbiology , Cross Infection/epidemiology , Disease Outbreaks , Genome, Bacterial , Hospitals , Phylogeny , Anti-Bacterial Agents/pharmacology , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , beta-Lactamases/genetics , Microbial Sensitivity Tests
5.
Molecules ; 29(7)2024 Mar 26.
Article En | MEDLINE | ID: mdl-38611746

Spodoptera frugiperda, the fall armyworm (FAW), is a highly invasive polyphagous insect pest that is considered a source of severe economic losses to agricultural production. Currently, the majority of chemical insecticides pose tremendous threats to humans and animals besides insect resistance. Thus, there is an urgent need to develop new pest management strategies with more specificity, efficiency, and sustainability. Chitin-degrading enzymes, including chitinases, are promising agents which may contribute to FAW control. Chitinase-producing microorganisms are reported normally in bacteria and fungi. In the present study, Serratia marcescens was successfully isolated and identified from the larvae of Spodoptera frugiperda. The bacterial strain NRC408 displayed the highest chitinase enzyme activity of 250 units per milligram of protein. Subsequently, the chitinase gene was cloned and heterologously expressed in E. coli BL21 (DE3). Recombinant chitinase B was overproduced to 2.5-fold, driven by the T7 expression system. Recombinant chitinase B was evaluated for its efficacy as an insecticidal bioagent against S. frugiperda larvae, which induced significant alteration in subsequent developmental stages and conspicuous malformations. Additionally, our study highlights that in silico analyses of the anticipated protein encoded by the chitinase gene (ChiB) offered improved predictions for enzyme binding and catalytic activity. The effectiveness of (ChiB) against S. frugiperda was evaluated in laboratory and controlled field conditions. The results indicated significant mortality, disturbed development, different induced malformations, and a reduction in larval populations. Thus, the current study consequently recommends chitinase B for the first time to control FAW.


Chitinases , Insecticides , Animals , Humans , Chitinases/genetics , Chitinases/pharmacology , Larva , Serratia marcescens/genetics , Zea mays , Spodoptera , Escherichia coli , Cloning, Molecular , Crops, Agricultural , Insecticides/pharmacology
6.
Commun Biol ; 7(1): 468, 2024 Apr 17.
Article En | MEDLINE | ID: mdl-38632370

Bacterial species often comprise well-separated lineages, likely emerged and maintained by genetic isolation and/or ecological divergence. How these two evolutionary actors interact in the shaping of bacterial population structure is currently not fully understood. In this study, we investigate the genetic and ecological drivers underlying the evolution of Serratia marcescens, an opportunistic pathogen with high genomic flexibility and able to colonise diverse environments. Comparative genomic analyses reveal a population structure composed of five deeply-demarcated genetic clusters with open pan-genome but limited inter-cluster gene flow, partially explained by Restriction-Modification (R-M) systems incompatibility. Furthermore, a large-scale research on hundred-thousands metagenomic datasets reveals only a partial habitat separation of the clusters. Globally, two clusters only show a separate gene composition coherent with ecological adaptations. These results suggest that genetic isolation has preceded ecological adaptations in the shaping of the species diversity, an evolutionary scenario coherent with the Evolutionary Extended Synthesis.


Genetic Variation , Serratia marcescens , Serratia marcescens/genetics , Ecosystem , Gene Flow , Genomics
7.
J Biotechnol ; 387: 58-68, 2024 May 20.
Article En | MEDLINE | ID: mdl-38582407

Serratiopeptidase, a proteolytic enzyme serves as an important anti-inflammatory and analgesic medication. Present study reports the production and purification of extracellular serratiopeptidase from an endophyte, Serratia marcescens MES-4, isolated from Morus rubra. Purification of the enzyme by Ion exchange chromatography led to the specific activity of 13,030 U/mg protein of serratiopeptidase, showcasing about 3.1 fold enhanced activity. The catalytic domain of the purified serratiopeptidase, composed of Zn coordinated with three histidine residues (His 209, His 213, and His 219), along with glutamate (Glu 210) and tyrosine (Tyr 249). The molecular mass, as determined by SDS-PAGE was ∼51 kDa. The purified serratiopeptidase displayed optimal activity at pH 9.0, temperature 50°C. Kinetic studies revealed Vmax and Km values of 33,333 U/mL and 1.66 mg/mL, respectively. Further, optimized conditions for the production of serratiopeptidase by Taguchi design led to the productivity of 87 U/mL/h with 87.9 fold enhanced production as compared to the previous conditions.


Endophytes , Peptide Hydrolases , Serratia marcescens , Serratia marcescens/enzymology , Serratia marcescens/genetics , Peptide Hydrolases/metabolism , Peptide Hydrolases/isolation & purification , Peptide Hydrolases/chemistry , Peptide Hydrolases/genetics , Endophytes/enzymology , Hydrogen-Ion Concentration , Kinetics , Temperature , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Bacterial Proteins/chemistry , Bacterial Proteins/isolation & purification
8.
Biochem Biophys Res Commun ; 710: 149877, 2024 May 28.
Article En | MEDLINE | ID: mdl-38581956

OxyR, a LysR family transcriptional regulator, plays vital roles in bacterial oxidative stress response. In this study, we found that the deletion of oxyR not only inhibited the antioxidant capacity of S. marcescens FS14, but also decreased the production of prodigiosin. Further study revealed that OxyR activated the prodigiosin biosynthesis at the transcriptional level. Complementary results showed that not only the wild-type OxyR but also the reduced form OxyRC199S could activate the prodigiosin biosynthesis. We further demonstrated that reduced form of wild type OxyR could bind to the promoter of pig gene cluster, and identified the binding sites which is different from oxidized OxyR binding sites in E. coli. Our results demonstrated that OxyR in FS14 uses oxidized form to regulate the expression of the antioxidant related genes and utilizes reduced form to activate prodigiosin production. Further in silico analysis suggested that the activation of prodigiosin biosynthesis by reduced OxyR should be general in S. marcesencs. To our knowledge, this is the first report to show that OxyR uses the reduced form to activate the gene's expression, therefore, our results provide a novel regulation mechanism of OxyR.


Prodigiosin , Serratia marcescens , Animals , Swine , Serratia marcescens/genetics , Serratia marcescens/metabolism , Escherichia coli/metabolism , Antioxidants/metabolism , Bacterial Proteins/genetics , Bacterial Proteins/metabolism
9.
J Infect Public Health ; 17(5): 918-921, 2024 May.
Article En | MEDLINE | ID: mdl-38574416

Newborns admitted to neonatal intensive care units (NICU) are at increased risk of health care-associated infections. Serratia marcescens represent the third most common pathogen in NICU outbreaks. Here we present an outbreak investigation performed using Whole Genome Sequencing (WGS) analyses and the control measures implemented to limit the spread of S. marcescens in the NICU of an Italian hospital. In February 2023 S. marcescens was isolated from six newborns, when in 2022 this pathogen was isolated only from two samples in the same ward. Measures for infection prevention were adopted. Routinary surveillance screening, performed with rectal swabs collected at admission and weekly thereafter, was implemented to search for S. marcescens presence. Environmental samples were collected. All the isolates, obtained from the conjunctival swab of six newborns, from rectal swab of two newborns who did not develop infections, as well as from the aerators of two faucets, were sequenced. WGS analyses showed no correlation between the isolates from newborns and environmental isolates. The implementation of the measures for infection prevention and control had enabled us to successfully control the outbreak within a short period. WGS analyses proved to be crucial in outbreak investigation to limit the spreading of the pathogens.


Cross Infection , Serratia Infections , Humans , Infant, Newborn , Intensive Care Units, Neonatal , Serratia marcescens/genetics , Serratia Infections/diagnosis , Cross Infection/prevention & control , Disease Outbreaks/prevention & control , Whole Genome Sequencing
10.
Emerg Infect Dis ; 30(13): S41-S48, 2024 04.
Article En | MEDLINE | ID: mdl-38561639

Serratia marcescens is an environmental gram-negative bacterium that causes invasive disease in rare cases. During 2020-2022, an outbreak of 21 invasive Serratia infections occurred in a prison in California, USA. Most (95%) patients had a history of recent injection drug use (IDU). We performed whole-genome sequencing and found isolates from 8 patients and 2 pieces of IDU equipment were closely related. We also identified social interactions among patients. We recovered S. marcescens from multiple environmental samples throughout the prison, including personal containers storing Cell Block 64 (CB64), a quaternary ammonium disinfectant solution. CB64 preparation and storage conditions were suboptimal for S. marcescens disinfection. The outbreak was likely caused by contaminated CB64 and propagated by shared IDU equipment and social connections. Ensuring appropriate preparation, storage, and availability of disinfectants and enacting interventions to counteract disease spread through IDU can reduce risks for invasive Serratia infections in California prisons.


Cross Infection , Disinfectants , Prisoners , Serratia Infections , Humans , Serratia marcescens/genetics , Serratia Infections/epidemiology , Prisons , Cross Infection/microbiology , Disease Outbreaks , California/epidemiology
11.
Pestic Biochem Physiol ; 201: 105864, 2024 May.
Article En | MEDLINE | ID: mdl-38685240

MicroRNAs (miRNAs) are noncoding small regulatory RNAs involved in diverse biological processes. Odontotermes formosanus (Shiraki) is a polyphagous pest that causes economic damage to agroforestry. Serratia marcescens is a bacterium with great potential for controlling this insect. However, knowledge about the miRNA pathway and the role of miRNAs in O. formosanus defense against SM1 is limited. In this study, OfAgo1, OfDicer1 and OfDrosha were differentially expressed in different castes and tissues. SM1 infection affected the expression of all three genes in O. formosanus. Then, we used specific double-stranded RNAs to silence OfAgo1, OfDicer1 and OfDrosha. Knockdown of these genes enhanced the virulence of SM1 to O. formosanus, suggesting that miRNAs were critical in the defense of O. formosanus against SM1. Furthermore, we sequenced miRNAs from SM1-infected and uninfected O. formosanus. 33 differentially expressed (DE) miRNAs were identified, whereby 22 were upregulated and 11 were downregulated. Finally, the miRNA-mRNA networks were constructed, which further suggested the important role of miRNAs in the defense of O. formosanus against SM1. Totally, O. formosanus miRNA core genes defend against SM1 infection by regulating miRNA expression. This study elucidates the interactions between O. formosanus and SM1 and provides new theories for biological control.


MicroRNAs , Serratia marcescens , MicroRNAs/genetics , MicroRNAs/metabolism , Serratia marcescens/genetics , Serratia marcescens/pathogenicity , Animals , Coleoptera/microbiology , Coleoptera/genetics
12.
In Vivo ; 38(3): 1229-1235, 2024.
Article En | MEDLINE | ID: mdl-38688617

BACKGROUND/AIM: Given the characteristics of Serratia marcescens (S. marcescens), this study aimed at investigating its presence in the hands and contact lens cases of orthokeratology wearers, along with the status of bacterial contamination. PATIENTS AND METHODS: The 39 patients received the questionnaires about the background of orthokeratology and hygiene habits. A total of 39 contact lens cases and 39 hand samples from the patients were collected at Show Chwan Memorial Hospital from June to August in 2020 and sent to National Chung Cheng University for DNA extraction and PCR identification. RESULTS: The results indicated a detection rate of 5.13% for S. marcescens in the contact lens cases and 12.82% in the hand samples. Additionally, 66.67% of contact lens case samples and 30.77% of hand samples found positive for 16s bacterial amplicons. The relationship between hand contamination and the duration of contact lens usage were revealed for both S. marcescens (p=0.021) and 16s bacterial amplicons (p=0.048). CONCLUSION: The results indicated that hand hygiene is more critical than focusing on contact lens hygiene when it comes to preventing S. marcescens infections. Nevertheless, both proper hand and contact lens hygiene practices can reduce the detection of bacterial eye pathogens, especially a common intestinal bacterium.


Serratia Infections , Serratia marcescens , Humans , Serratia marcescens/isolation & purification , Serratia marcescens/genetics , Male , Female , Serratia Infections/microbiology , Serratia Infections/epidemiology , Serratia Infections/diagnosis , Orthokeratologic Procedures/methods , Contact Lenses/microbiology , Contact Lenses/adverse effects , Child , Adolescent , Hygiene , Hand Hygiene , Adult , Hand/microbiology
13.
Int J Antimicrob Agents ; 63(5): 107149, 2024 May.
Article En | MEDLINE | ID: mdl-38508537

OBJECTIVES: blaKPC-carrying Enterobacterales have post great challenges to global healthcare systems. In this study, we reported the evolution and spread of blaKPC between Serratia marcescens and Klebsiella pneumoniae. METHODS: Four S. marcescens and one K. pneumoniae strains were isolated from the sputum samples of the patient. Antimicrobial susceptibility tests and whole genome sequencing were performed to investigate the phenotype & genotype of strains. Conjugation assays, cloning experiment and kinetic parameters measuring were performed to explore the spread and antimicrobial resistance mechanisms. RESULTS: The evolution and transmission of blaKPC-2 occurred during the treatment of ceftazidime-avibactam and trimethoprim-sulfamethoxazole. Analysis of the antimicrobial susceptibility and genetic profiles of the clinical strains showed that blaKPC-2 evolved into blaKPC-71 and blaKPC-44, together with resistance to ceftazidime-avibactam and carbapenems susceptibility recovery under antimicrobial pressure. Cloning and expression of blaKPC-44 & blaKPC-71 in E. coli DH5α showed that KPC-44 and KPC-71 resulted in a 64∼128-fold increase in the MIC value for ceftazidime-avibactam. Meanwhile, the kinetic assays also showed that the enzyme activity of KPC-44 and KPC-71 towards carbapenems was destroyed and couldn't be inhibited by avibactam. Based on the conjugation assay and whole genome sequence analyses, we provided evolutionary insights into the transmission pathway trace of blaKPC-bearing plasmids between S. marcescens and K. pneumoniae. CONCLUSIONS: Mixed-species co-infection is one of the risk factors leading to the spread of plasmids carrying carbapenem-resistant genes, and increased surveillance of multidrug-resistant Enterobacterales is urgently needed.


Anti-Bacterial Agents , Klebsiella Infections , Klebsiella pneumoniae , Microbial Sensitivity Tests , Plasmids , Serratia Infections , Serratia marcescens , Whole Genome Sequencing , beta-Lactamases , Serratia marcescens/genetics , Serratia marcescens/drug effects , Serratia marcescens/isolation & purification , Serratia marcescens/enzymology , Klebsiella pneumoniae/genetics , Klebsiella pneumoniae/drug effects , Humans , Plasmids/genetics , beta-Lactamases/genetics , Serratia Infections/microbiology , Serratia Infections/epidemiology , Anti-Bacterial Agents/pharmacology , Klebsiella Infections/microbiology , Klebsiella Infections/epidemiology , Ceftazidime/pharmacology , Drug Combinations , Drug Resistance, Multiple, Bacterial/genetics , Azabicyclo Compounds/pharmacology , Sputum/microbiology , Evolution, Molecular , Gene Transfer, Horizontal , Carbapenems/pharmacology
14.
Pol J Microbiol ; 73(1): 11-20, 2024 Mar 01.
Article En | MEDLINE | ID: mdl-38437469

Serratia marcescens is a global opportunistic pathogen. In vitro cytotoxicity of this bacterium is mainly related to metalloprotease serralysin (PrtS) activity. Proteolytic capability varies among the different isolates. Here, we characterized protease production and transcriptional regulators at 37°C of two S. marcescens isolates from bronchial expectorations, HU1848 and SmUNAM836. As a reference strain the insect pathogen S. marcescens Db10 was included. Zymography of supernatant cultures revealed a single (SmUNAM836) or double proteolytic zones (HU1848 and Db10). Mass spectrometry confirmed the identity of PrtS and the serralysin-like protease SlpB from supernatant samples. Elevated proteolytic activity and prtS expression were evidenced in the HU1848 strain through azocasein degradation and qRT-PCR, respectively. Evaluation of transcriptional regulators revealed higher eepR expression in HU1848, whereas cpxR and hexS transcriptional levels were similar between studied strains. Higher eepR expression in HU1848 was further confirmed through an in vivo transcriptional assay. Moreover, two putative CpxR binding motifs were identified within the eepR regulatory region. EMSA validated the interaction of CpxR with both motifs. The evaluation of eepR transcription in a cpxR deletion strain indicated that CpxR negatively regulates eepR. Sequence conservation suggests that regulation of eepR by CpxR is common along S. marcescens species. Overall, our data incorporates CpxR to the complex regulatory mechanisms governing eepR expression and associates the increased proteolytic activity of the HU1848 strain with higher eepR transcription. Based on the global impact of EepR in secondary metabolites production, our work contributes to understanding virulence factors variances across S. marcescens isolates.


Ataxia , Chondrodysplasia Punctata , Genetic Diseases, X-Linked , Mental Retardation, X-Linked , Seizures , Serratia marcescens , Humans , Serratia marcescens/genetics , Peptide Hydrolases/genetics
15.
J Environ Manage ; 356: 120684, 2024 Apr.
Article En | MEDLINE | ID: mdl-38531133

Microbial biotransformation is a recommended and reliable method in face of formidable tetracycline (TC) with broad-spectrum antibacterial activity. Herein, comprehensive characteristics of a newfound strain and its molecular mechanism in process of TC bioremediation were involved in this study. Specifically, Serratia marcescens MSM2304 isolated from pig manure sludge grew well in presence of TC and achieved optimal removal efficiency of 61% under conditions of initial TC concentration of 10 mg/L, pH of 7.0, cell inoculation amount of 5%, and tryptone of 10 g/L as additional carbon. The pathways of biotransformation include EPS biosorption, cell surface biosorption and biodegradation, which enzymatic processes of biodegradation were occurred through TC adsorbed by biofilms was firstly broken down by extracellular enzymes and part of TC migrated towards biofilm interior and degraded by intracellular enzymes. Wherein extracellular polysaccharides in extracellular polymeric substances (EPS) from biofilm of strain MSM2304 mainly performed extracellular adsorption, and changes in position and intensity of CO, =CH and C-O-C/C-O of EPS possible further implied TC adsorption by it. Biodegradation accounting for 79.07% played a key role in TC biotransformation and could be fitted well by first-order model that manifesting rapid and thorough removal. Potential biodegradation pathway including demethylation, dihydroxylation, oxygenation, and ring opening possibly involved in TC disposal process of MSM2304, TC-degrading metabolites exhibited lower toxicity to indicator bacteria relative to parent TC. Whole genome sequencing as underlying molecular evidence revealed that TC resistance genes, dehydrogenases-encoding genes, monooxygenase-encoding genes, and methyltransferase-encoding genes of strain MSM2304 were positively related to TC biodegradation. Collectively, these results favored a theoretical evaluation for Serratia marcescens MSM2304 as a promising TC-control agent in environmental bioremediation processes.


Serratia marcescens , Tetracycline , Animals , Swine , Serratia marcescens/genetics , Anti-Bacterial Agents/analysis , Biotransformation , Genomics
16.
ACS Synth Biol ; 13(3): 969-972, 2024 Mar 15.
Article En | MEDLINE | ID: mdl-38340070

Serratia marcescens has garnered increasing attention as a promising host for valuable compound production. However, the lack of an efficient gene regulation toolkit severely hampers its applications. Here, a library of stationary phase promoters was screened in S. marcescens HBA7 using RNA-seq and RT-qPCR, revealing a 43-fold regulatory range with the red fluorescent protein mKate2 as the reporter. The ß-galactosidase was employed to demonstrate the universality in driving the expression of different proteins. The wide-ranging utility of these promoters in different hosts was demonstrated in Escherichia coli. Moreover, to assess their potential application, the strongest promoter, P2, was employed to express the swrW gene, resulting in a roughly 20-fold increase in serrawettin W1 production in S. marcescens HBQA7ΔswrW. In summary, this study successfully constructed a gradient-strength stationary phase promoter library, providing an effective toolkit for gene regulation and secondary metabolite production in diverse prokaryotes, including S. marcescens and E. coli.


Escherichia coli , Serratia marcescens , Serratia marcescens/genetics , Escherichia coli/genetics , Escherichia coli/metabolism , Promoter Regions, Genetic/genetics , Gene Expression Regulation
17.
Int Immunopharmacol ; 129: 111559, 2024 Mar 10.
Article En | MEDLINE | ID: mdl-38330794

Antibiotic-resistant Serratia marcescens (Sm) is known to cause bloodstream infections, pneumonia, etc. The nod-like receptor family, pyrin domain-containing 3 (NLRP3), has been implicated in various lung infections. Yet, its role in Sm-induced pneumonia was not well understood. In our study, we discovered that deletion of Nlrp3 in mice significantly improved Sm-induced survival rates, reduced bacterial loads in the lungs, bronchoalveolar lavage fluid (BALF), and bloodstream, and mitigated the severity of acute lung injury (ALI) compared to wild-type (WT) mice. Mechanistically, we observed that 24 h post-Sm infection, NLRP3 inflammasome activation occurred, leading to gasdermin D NH2-terminal (GSDMD-NT)-induced pyroptosis in macrophages and IL-1ß secretion. The NLRP3 or NLRP3 inflammasome influenced the expression PD-L1 and PD-1, as well as the count of PD-L1 or PD-1-expressing macrophages, alveolar macrophages, interstitial macrophages, PD-L1-expressing neutrophils, and the count of macrophage receptors with collagenous structure (MARCO)-expressing macrophages, particularly MARCO+ alveolar macrophages. The frequency of MARCO+ alveolar macrophages, PD-1 expression, particularly PD-1+ interstitial macrophages were negatively or positively correlated with the Sm load, respectively. Additionally, IL-1ß levels in BALF correlated with three features of acute lung injury: histologic score, protein concentration and neutrophil count in BALF. Consequently, our findings suggest that Nlrp3 deletion offers protection agaisnt acute Sm pneumonia in mice by inhibiting inflammasome activation and reducing Sm infection-induced PD-L1/PD-1 or MARCO expression, particularly in macrophages. This highlights potential therapeutic targets for Sm and other gram-negative bacteria-induced acute pneumonia.


Acute Lung Injury , Pneumonia , Mice , Animals , NLR Family, Pyrin Domain-Containing 3 Protein/genetics , NLR Family, Pyrin Domain-Containing 3 Protein/metabolism , Inflammasomes/metabolism , Programmed Cell Death 1 Receptor/metabolism , Serratia marcescens/genetics , Serratia marcescens/metabolism , B7-H1 Antigen/genetics , B7-H1 Antigen/metabolism , Pneumonia/metabolism , Macrophages/metabolism , Acute Lung Injury/chemically induced , Interleukin-1beta/metabolism , Lipopolysaccharides/pharmacology , Mice, Knockout
18.
BMC Infect Dis ; 24(1): 266, 2024 Feb 28.
Article En | MEDLINE | ID: mdl-38418981

BACKGROUND: Serratia marcescens is a gram-negative bacterium that is widespread in the environment. S. marcescens bacteremia can be fatal during pregnancy and cause persistent chorioamnionitis. This study reports an outbreak of Serratia marcescens bloodstream infection (BSI) among high-risk pregnant women in an obstetric ward. The purpose of this study is to report our experience with the usefulness of the ATP test in hospital environmental management and to confirm that bloodstream infections of patients with the same strain were correlated by WGS testing. METHODS: This retrospective study collected the data of inpatients with S. marcescens bacteremia in obstetric ward for high-risk pregnant women from August 22, 2021, to October 14, 2021. We performed: an adenosine triphosphate (ATP) bioluminescence test in the environment with a high-contact area; environmental culture; on-site monitoring and staff education; and whole-genome sequencing (WGS) to evaluate genetic relationships among S. marcescens isolates. RESULTS: S. marcescens BSI occurred in four consecutive patients. None of the patients had central venous catheters. An ATP bioluminescence test revealed that high-contact areas and areas for injection preparation were not clean (≥ 1000 relative light units). However, S. marcescens was not identified in the environmental cultures, likely due to intensive environmental cleaning and discarding of potentially contaminated specimens before the culture test. On-site monitoring and education were conducted for 1 month. There were no further reports of BSI until 6 months after the last patient was discharged. WGS performed on three isolates from three patients indicated that the isolated S. marcescens was likely from the same strain. CONCLUSIONS: We controlled an S. marcescens outbreak by improving environmental cleaning as well as education of and behavior changes in healthcare workers. Using the ATP bioluminescence test can provide feedback on environmental cleaning and education. WGS played a role in determining the spread of BSI caused by the same strain.


Bacteremia , Cross Infection , Sepsis , Serratia Infections , Pregnancy , Humans , Female , Infant, Newborn , Cross Infection/epidemiology , Cross Infection/microbiology , Pregnant Women , Serratia marcescens/genetics , Retrospective Studies , Serratia Infections/epidemiology , Serratia Infections/microbiology , Sepsis/epidemiology , Disease Outbreaks , Bacteremia/epidemiology , Bacteremia/microbiology , Hospitals , Adenosine Triphosphate , Intensive Care Units, Neonatal
19.
Evolution ; 78(5): 1005-1013, 2024 May 01.
Article En | MEDLINE | ID: mdl-38416416

Behavioral avoidance of parasites is a widespread strategy among animal hosts and in human public health. Avoidance has repercussions for both individual and population-level infection risk. Although most cases of parasite avoidance are viewed as adaptive, there is little evidence that the basic assumptions of evolution by natural selection are met. This study addresses this gap by testing whether there is a heritable variation in parasite avoidance behavior. We quantified behavioral avoidance of the bacterial parasite Serratia marcescens for 12 strains of the nematode host Caenorhabditis elegans. We found that these strains varied in their magnitude of avoidance, and we estimated the broad-sense heritability of this behavior to be in the range of 11%-26%. We then asked whether avoidance carries a constitutive fitness cost. We did not find evidence of one. Rather, strains with higher avoidance had higher fitness, measured as population growth rate. Together, these results direct future theoretical and empirical work to identify the forces maintaining genetic variation in parasite avoidance.


Caenorhabditis elegans , Genetic Fitness , Genetic Variation , Serratia marcescens , Animals , Serratia marcescens/genetics , Serratia marcescens/physiology , Caenorhabditis elegans/genetics , Caenorhabditis elegans/physiology , Host-Parasite Interactions , Avoidance Learning
20.
Bull Entomol Res ; 114(2): 190-202, 2024 Apr.
Article En | MEDLINE | ID: mdl-38328866

Reticulitermes chinensis Snyder is an important pest in forestry and construction and is widely distributed in China. We found that Serratia marcescens Bizio strain SM1 has insecticidal activity to R. chinensis, but the pathogenic mechanism of SM1 to R. chinensis is not clear. Therefore, full-length transcriptome sequencing was performed on R. chinensis infected with SM1 and the control group. A total of 230 differentially expressed genes were identified by comparing SM1 infection group and the control group, among which 103 were downregulated and 127 were upregulated. We found downregulated genes in nine metabolic pathway categories, among which carbohydrate metabolism had the most downregulated genes, followed by energy metabolism and amino acid metabolism. We also found that some downregulated genes were related to pattern recognition receptors, cellular immunity, and humoral immunity, indicating that R. chinensis immunity was negatively affected by SM1 infection. In addition, some genes in signal transduction and genetic information processing pathways were downregulated. In this study, high-throughput full-length transcriptome analysis was used to analyse the pathogenic mechanism of SM1 to R. chinensis. The results of this study provide useful information for exploring the relationship between SM1 and R. chinensis, and provide theoretical support for the future application of SM1 and the prevention and treatment of R. chinensis.


Serratia marcescens , Transcriptome , Serratia marcescens/genetics , Animals , Moths/microbiology , Moths/genetics , Moths/immunology , Gene Expression Profiling
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