Risk factors for mortality in patients with Serratia marcescens bacteremia

Cultivation and sequencing-free protocol for Serratia marcescens detection and typing

Serratia marcescens is an opportunistic pathogen that survives in inhospitable environments causing large outbreaks, particularly in neonatal intensive care units (NICUs). Genomic studies revealed that most S. marcescens nosocomial infections are caused by a specific clone (here "Infectious clone"). Whole genome sequencing (WGS) is the only portable method able to identify this clone, but it requires days to obtain results. We present a cultivation-free hypervariable-locus melting typing (HLMT) protocol for the fast detection and typing of S. marcescens, with 100% detection capability on mixed samples and a limit of detection that can reach the 10 genome copies. The protocol was able to identify the S. marcescens infectious clone with 97% specificity and 96% sensitivity when compared to WGS, yielding typing results portable among laboratories. The protocol is a cost and time saving method for S. marcescens detection and typing for large environmental/clinical surveillance screenings, also in low-middle income countries.

Antimicrobial and anti-virulence activities of 4-shogaol from grains of paradise against gram-negative bacteria: Integration of experimental and computational methods

ETHNOPHARMACOLOGICAL RELEVANCE

Bacterial resistance to antibiotics is a growing global concern, highlighting the urgent need for new antimicrobial candidates. Aframomum melegueta was traditionally used for combating urinary tract and soft tissue infections, which implies its potential as an antimicrobial agent.

AIM OF STUDY

This study was designed to explore the antibacterial and anti-virulence capabilities of 4-shogaol isolated from A. melegueta seeds versus gram-negative bacteria: Serratia marcescens, Klebsiella pneumoniae, Acinetobacter baumannii, and the clinically important pathogen Pseudomonas aeruginosa.

MATERIALS AND METHODS

4-Shogeol was isolated from A. melegueta seeds and its MICs were determined for Acinetobacter baumannii (ATCC-17978), Pseudomonas aeruginosa (ATCC-27853), Klebsiella pneumoniae (ATCC-700603), and Serratia marcescens clinical isolate. The anti-efflux activity and effect on the bacterial cell membrane for the compound were evaluated. Furthermore, the anti-virulence activities of the compound were evaluated. The effects of 4-shogeol at sub-MIC on bacterial motility, biofilm formation, and production of virulent enzymes and pigments were assessed. The anti-quorum sensing activities of 4-shogeol were evaluated virtually and by quantification its effect on the expression of quorum sensing encoding genes. The in vivo protection assay was conducted to evaluate the effect of 4-shogaol on the P. aeruginosa capacity to induce pathogenesis in mice. Finally, the effect of shogaol-antibiotics combination was assessed.

RESULTS

The research revealed that 4-shogaol's antibacterial action primarily involves disrupting the bacterial cell membrane and efflux pumps. It also exhibited significant anti-virulence effects by reducing biofilm development and repressing virulence factors production, effectively protecting mice against P. aeruginosa infection. Furthermore, when combined with antibiotics, 4-shogaol demonstrated synergistic effects, leading to reduced minimum inhibitory concentrations (MICs) against P. aeruginosa. Its anti-virulence properties were linked to its ability to disrupt bacterial quorum sensing (QS) mechanisms, as evidenced by its interaction with QS receptors and downregulation of QS-related genes. Notably, in silico analysis indicated that 4-shogaol exhibited strong binding affinity to different P. aeruginosa QS targets.

CONCLUSION

These findings suggest that 4-shogaol holds promise as an effective anti-virulence agent that can be utilized in combination with antibiotics for treating severe infections caused by gram-positive bacteria.

Morbidity and mortality of Serratia marcescens bacteraemia during the substance use epidemic

BACKGROUND

Serratia marcescens (S. marcescens) is an Enterobacterales species present throughout the environment and causes a range of infections. Historically, S. marcescens has been associated with persons who inject drugs (PWID), but literature is scarce. This study aimed to compare treatment characteristics and clinical outcomes between PWID and non-PWID with Serratia marcescens bacteraemia.

METHODS

This was a retrospective cohort study of patients hospitalised with S. marcescens bacteraemia from 1 January 2013 to 31 December 2019 at a tertiary medical centre. Patients were included if they were aged ≥ 18 years and had at least one positive blood culture for S. marcescens.

RESULTS

Of the 67 patients who met inclusion criteria, 14 were identified as PWID (21%) and 53 were non-PWID (79%). Persons who inject drugs were younger (median age: PWID 32 years, non-PWID 67 years) and less likely to have renal disease (PWID 7%, non-PWID 34%). Persons who inject drugs had a higher incidence of infective endocarditis (IE) (PWID 48%, non-PWID 0%) and were more likely to receive combination antimicrobial therapy (PWID 29%, non-PWID 2%). All-cause mortality at 12 months was comparable between groups (PWID 21%, non-PWID 21%).

CONCLUSION

This study demonstrates that long-term outcomes of PWID are comparable with non-PWID, despite PWID being a younger cohort with fewer comorbidities. Clinicians should have high suspicion of IE in PWID with S. marcescens bacteraemia.

Outbreak of Serratia marcescens in the Neonatal Intensive Care Unit of a Tertiary Care Hospital in Mexico

Introduction

We describe an outbreak of Serratia marcescens (S. marcescens) infection in the neonatal intensive care unit at Women's Hospital in Sinaloa, Mexico.

Methods

In April 2021, an outbreak of S. marcescens infection was identified. A case was identified as any patient who tested positive for S. marcescens and showed signs of an infectious process.

Results

S. marcescens was isolated from the blood cultures of 15 neonates with clinical signs of neonatal sepsis. Statistical analysis showed that all neonates had an invasive medical device. The problem was controlled after hospital hygiene and sanitation measures were strengthened.

Conclusion

The study provides evidence of an outbreak of nosocomial bacteremia due to the cross-transmission of S. marcescens. The findings highlight the need for hospitals to implement strict hygiene measures, especially regarding hand washing, to prevent future outbreaks.

The Effects of Doxapram Blocking the Response of Gram-Negative Bacterial Toxin (LPS) at Glutamatergic Synapses

Lipopolysaccharides (LPS) associated with Gram-negative bacteria are one factor responsible for triggering the mammalian immune response. Blocking the action of LPS is key to reducing its downstream effects. However, the direct action of LPS on cells is not yet fully addressed. LPS can have rapid, direct effects on cells in the absence of a systemic immune response. Recent studies have shown that doxapram, a blocker of a subset of K2P channels, also blocks the acute actions of LPS. Doxapram was evaluated to determine if such action also occurs at glutamatergic synapses in which it is known that LPS can increase synaptic transmission. Doxapram at 5 mM first enhanced synaptic transmission, then reduced synaptic response, while 10 mM rapidly blocked transmission. Doxapram at 5 mM blocked the excitatory response induced by LPS. Enhancing synaptic transmission with LPS and then applying LPS combined with doxapram also resulted in retarding the response of LPS. It is possible doxapram and LPS are mediated via a similar receptor or cellular responses. The potential of designing pharmacological compounds with a similar structure to doxapram and determining the binding of such compounds can aid in addressing the acute, direct actions by LPS on cells.

Medical Astro-Microbiology: Current Role and Future Challenges

The second and third decades of the twenty-first century are marked by a flourishing of space technology which may soon realise human aspirations of a permanent multiplanetary presence. The prevention, control and management of infection with microbial pathogens is likely to play a key role in how successful human space aspirations will become. This review considers the emerging field of medical astro-microbiology. It examines the current evidence regarding the risk of infection during spaceflight via host susceptibility, alterations to the host's microbiome as well as exposure to other crew members and spacecraft's microbiomes. It also considers the relevance of the hygiene hypothesis in this regard. It then reviews the current evidence related to infection risk associated with microbial adaptability in spaceflight conditions. There is a particular focus on the International Space Station (ISS), as one of the only two  crewed objects in low Earth orbit. It discusses the effects of spaceflight related stressors on viruses and the infection risks associated with latent viral reactivation and increased viral shedding during spaceflight. It then examines the effects of the same stressors on bacteria, particularly in relation to changes in virulence and drug resistance. It also considers our current understanding of fungal adaptability in spaceflight. The global public health and environmental risks associated with a possible re-introduction to Earth of invasive species are also briefly discussed. Finally, this review examines the largely unknown microbiology and infection implications of celestial body habitation with an emphasis placed on Mars. Overall, this review summarises much of our current understanding of medical astro-microbiology and identifies significant knowledge gaps.

Graphical Abstract

Diminishing the Pathogenesis of the Food-Borne Pathogen Serratia marcescens by Low Doses of Sodium Citrate

Protecting food from bacterial contamination is crucial for ensuring its safety and avoiding foodborne illness. Serratia marcescens is one of the food bacterial contaminants that can form biofilms and pigments that spoil the food product and could cause infections and illness to the consumer. Food preservation is essential to diminish such bacterial contaminants or at least reduce their pathogenesis; however, it should not affect food odor, taste, and consistency and must be safe. Sodium citrate is a well-known safe food additive and the current study aims to evaluate its anti-virulence and anti-biofilm activity at low concentrations against S. marcescens. The anti-virulence and antibiofilm activities of sodium citrate were evaluated phenotypically and genotypically. The results showed the significant effect of sodium citrate on decreasing the biofilm formation and other virulence factors, such as motility and the production of prodigiosin, protease, and hemolysins. This could be owed to its downregulating effect on the virulence-encoding genes. An in vivo investigation was conducted on mice and the histopathological examination of isolated tissues from the liver and kidney of mice confirmed the anti-virulence activity of sodium citrate. In addition, an in silico docking study was conducted to evaluate the sodium citrate binding ability to S. marcescens quorum sensing (QS) receptors that regulates its virulence. Sodium citrate showed a marked virtual ability to compete on QS proteins, which could explain sodium citrate’s anti-virulence effect. In conclusion, sodium citrate is a safe food additive and can be used at low concentrations to prevent contamination and biofilm formation by S. marcescens and other bacteria.

New insights into the antibacterial mode of action of quercetin against uropathogen Serratia marcescens in-vivo and in-vitro

In the course of a quest for therapeutic agents inhibiting uropathogens, the rise and universal blowout of antibiotic-resistant organisms is a wide problem. To overcome this matter, exploration of alternative antimicrobials is necessary. The antimicrobial potential of quercetin has been widely described against some pathogenic microorganisms, but to the best of our knowledge, no report exists against the pathogenicity of uropathogenic Serratia marcescens. Hence, the present study focused on the antibacterial mechanism of action of quercetin, a flavonoid against the uropathogen Serratia marcescens. Quercetin was evaluated for its anti-QS activity, and the attained outcomes showed that quercetin inhibited QS-mediated virulence factors such as biofilm formation, exopolysaccharides, swarming motility and prodigiosin in Serratia marcescens. The proposed mechanism of action of quercetin greatly influences cell metabolism and extracellular polysaccharide synthesis and damages the cell membrane, as revealed through global metabolome profiling. In vivo experiments revealed that treatment with quercetin prolonged the life expectancy of infected Caenorhabditis elegans and reduced the colonization of Serratia marcescens. Hence, the current study reveals the use of quercetin as a probable substitute for traditional antibiotics in the treatment of uropathogen infections driven by biofilms.

Evaluation of the whole proteome to design a novel mRNA-based vaccine against multidrug-resistant Serratia marcescens

Serratia marcescens, a Gram-negative bacterium, is one of the known disease-causing pathogens. It is resistant to ampicillin, macrolides, cephalosporins, cefotaxime, and ceftazidime. The only antibiotic that has been proven to be effective against S. marcescens is gentamicin. By causing epigenetic alterations, bacteria can also become resistant to all antibiotics. Many epigenetically related proteins were studied, and four proteins were selected in this regard for epitope evaluation and their subsequent use in the development of a messenger ribonucleic acid (mRNA) vaccine. A series of immune-informatics tools used to build this mRNA vaccine elicited cellular and humoral immunity. Molecular docking between epitopes and alleles of the major histocompatibility complex (MHC) was performed. The vaccine was developed using 37 epitopes, an adjuvant that is a TLR-4 agonist known as resuscitation-promoting factor E (RpfE), subcellular trafficking structures, secretion boosters, and linkers. This proposed architecture was found to cover 99.6% of the population during testing. During testing, it was proven that it was both effective and safe. To confirm our idea, we performed an in silico immunological simulation of vaccination. The codon was also optimized to ensure that the mRNA reached the cytoplasm of a human host and underwent efficient translation. TLR-4 and TLR-3 were also docked against the secondary and tertiary structures of the vaccine peptide. Furthermore, the vaccine's stability was confirmed by molecular dynamics simulation. In summary, this vaccine construct can be a potential candidate against S. marcescens and is suitable for in vitro analyses to validate its effectiveness.

Remedial Aspect of Zinc Oxide Nanoparticles Against Serratia Marcescens and Enterococcus Faecalis

Zinc oxide nanoparticles (ZnO NPs) have been widely used in biomedical applications due to their high biocompatibility and low toxicity to humans. The present work aimed to investigate the antibacterial effects of different concentrations of ZnO NPs on two opportunistic pathogens, Serratia marcescens and Enterococcus faecalis. The surface interaction between nanoparticles and bacterial cell wall, and the subsequent morphological alterations on the bacterial surface, were examined through Fourier transform infrared spectroscopy and scanning electron microscope. The energy dispersive X-ray analysis was used to confirm the elemental composition of ZnO NPs and the cellular accumulation of ZnO NPs in bacteria. The growth-inhibitory test demonstrated a dose-dependent growth inhibitory effect of ZnO NPs against both the test bacteria, as the higher concentration of nanoparticles caused the higher bacterial growth inhibition. The results showed that ZnO NPs caused a higher growth inhibition (63.50 ± 2.50%) on the Gram-positive bacterium E. faecalis compared to the Gram-negative bacterium S. marcescens (51.27 ± 4.56%). Fourier transform infrared spectrum revealed the possible involvement of hydroxyl, carboxyl, amides, methylene, and phosphate groups from the biomolecules of bacterial cell wall such as proteins, carbohydrates, lipids, and phospholipids in the interaction of ZnO NPs on bacterial cell surface. Energy dispersive X-ray analysis showed the higher accumulation of ZnO NPs in E. faecalis than S. marcescens analogous to the bacterial growth inhibition. Scanning electron microscopy images confirmed the antibacterial properties of ZnO NPs, showing the loss of integrity of cell membrane and distortion of bacterial cells. Hence, the potential of ZnO NP as an antibacterial agent against S. marcescens and E. faecalis has been confirmed.

Mutations in AR or SRD5A2 Genes: Clinical Findings, Endocrine Pitfalls, and Genetic Features of Children with 46,XY DSD

OBJECTIVE

Androgen insensivity syndrome (AIS) and 5α-reductase deficiency (5α-RD) present with indistinguishable phenotypes among the 46,XY disorders of sexual development (DSD) that usually necessitate molecular analyses for the definitive diagnosis in the prepubertal period. The aim was to evaluate the clinical, hormonal and genetic findings of 46,XY DSD patients who were diagnosed as AIS or 5α-RD.

METHODS

Patients diagnosed as AIS or 5α-RD according to clinical and hormonal evaluations were investigated. Sequence variants of steroid 5-α-reductase type 2 were analyzed in cases with testosterone/dihydrotestosterone (T/DHT) ratio of ≥20, whereas the androgen receptor (AR) gene was screened when the ratio was <20. Stepwise analysis of other associated genes were screened in cases with no causative variant found in initial analysis. For statistical comparisons, the group was divided into three main groups and subgroups according to their genetic diagnosis and T/DHT ratios.

RESULTS

A total of 128 DSD patients from 125 non-related families were enrolled. Birth weight SDS and gestational weeks were significantly higher in 5α-RD group than in AIS and undiagnosed groups. Completely female phenotype was higher in all subgroups of both AIS and 5α-RD patients than in the undiagnosed subgroups. In those patients with stimulated T/DHT <20 in the prepubertal period, stimulated T/DHT ratio was significantly lower in AIS than in the undiagnosed group, and higher in 5α-RD. Phenotype associated variants were detected in 24% (n=18 AIS, n=14 5α-RD) of the patients, revealing four novel AR variants (c.94G>T, p.Glu32*, c.330G>C, p.Leu110=; c.2084C>T, p.Pro695Leu, c.2585_2592delAGCTCCTG, p.(Lys862Argfs*16), of these c.330G>C with silent status remained undefined in terms of its causative effects.

CONCLUSION

T/DHT ratio is an important hormonal criterion, but in some cases, T/DHT ratio may lead to diagnostic confusion. Molecular diagnosis is important for the robust diagnosis of 46,XY DSD patients. Four novel AR variants were identified in our study.

A Systematic Immuno-Informatic Approach to Design a Multiepitope-Based Vaccine Against Emerging Multiple Drug Resistant Serratia marcescens

Serratia marcescens is now an important opportunistic pathogen that can cause serious infections in hospitalized or immunocompromised patients. Here, we used extensive bioinformatic analyses based on reverse vaccinology and subtractive proteomics-based approach to predict potential vaccine candidates against S. marcescens. We analyzed the complete proteome sequence of 49 isolate of Serratia marcescens and identified 5 that were conserved proteins, non-homologous from human and gut flora, extracellular or exported to the outer membrane, and antigenic. The identified proteins were used to select 5 CTL, 12 HTL, and 12 BCL epitopes antigenic, non-allergenic, conserved, hydrophilic, and non-toxic. In addition, HTL epitopes were able to induce interferon-gamma immune response. The selected peptides were used to design 4 multi-epitope vaccines constructs (SMV1, SMV2, SMV3 and SMV4) with immune-modulating adjuvants, PADRE sequence, and linkers. Peptide cleavage analysis showed that antigen vaccines are processed and presented via of MHC class molecule. Several physiochemical and immunological analyses revealed that all multiepitope vaccines were non-allergenic, stable, hydrophilic, and soluble and induced the immunity with high antigenicity. The secondary structure analysis revealed the designed vaccines contain mainly coil structure and alpha helix structures. 3D analyses showed high-quality structure. Molecular docking analyses revealed SMV4 as the best vaccine construct among the four constructed vaccines, demonstrating high affinity with the immune receptor. Molecular dynamics simulation confirmed the low deformability and stability of the vaccine candidate. Discontinuous epitope residues analyses of SMV4 revealed that they are flexible and can interact with antibodies. In silico immune simulation indicated that the designed SMV4 vaccine triggers an effective immune response. In silico codon optimization and cloning in expression vector indicate that SMV4 vaccine can be efficiently expressed in E. coli system. Overall, we showed that SMV4 multi-epitope vaccine successfully elicited antigen-specific humoral and cellular immune responses and may be a potential vaccine candidate against S. marcescens. Further experimental validations could confirm its exact efficacy, the safety and immunogenicity profile. Our findings bring a valuable addition to the development of new strategies to prevent and control the spread of multidrug-resistant Gram-negative bacteria with high clinical relevance.

Infective endocarditis by Serratia species: a systematic review

Serratia species are facultative anaerobes, non-spore-forming, motile Gram-negative bacteria. Serratia spp. are currently thought to cause a variety of infections, such as bacteremia, urinary tract infections, and pneumonia, as well as other, less common infections, including ocular infections or skin and soft tissue infections. On the other hand, Infective Endocarditis (IE) is an infrequent disease with notable morbidity and mortality. Even though IE is rarely caused by Serratia spp., these infections can be quite problematic due to the lack of experience in their management. This study aimed to systematically review all published cases of IE by Serratia spp. in the literature. A systematic review of PubMed, Scopus, and Cochrane library (through 13^th May 2021) for studies providing epidemiological, clinical, microbiological data as well as data on treatment and outcomes of IE by Serratia spp. was performed. In total, 50 studies, containing data for 72 patients, were included. A prosthetic valve was present in 18.1%. The mitral valve was the most commonly infected site, followed by the aortic valve. The diagnosis was facilitated by transthoracic echocardiography in 34.7%, while the diagnosis was set at autopsy in 22.4%. Fever, sepsis, and embolic phenomena were the most common clinical presentations, followed by heart failure. Aminoglycosides, cephalosporins, and carbapenems were the most commonly used antimicrobials. Clinical cure was noted only in 53.5%, while overall mortality was 47.2%. Having surgery along with antimicrobial treatment was independently associated with reduced overall mortality. IE by Serratia spp. was more likely to be associated with intravenous drug use, and to present with heart failure and embolic phenomena compared to IE by other non-HACEK Gram-negative bacilli, while mortality was also higher in IE by Serratia spp.

Rapid and Direct Action of Lipopolysaccharide (LPS) on Skeletal Muscle of Larval Drosophila

The endotoxin lipopolysaccharide (LPS) from Gram-negative bacteria exerts a direct and rapid effect on tissues. While most attention is given to the downstream actions of the immune system in response to LPS, this study focuses on the direct actions of LPS on skeletal muscle in Drosophila melanogaster. It was noted in earlier studies that the membrane potential rapidly hyperpolarizes in a dose-dependent manner with exposure to LPS from Pseudomonas aeruginosa and Serratia marcescens. The response is transitory while exposed to LPS, and the effect does not appear to be due to calcium-activated potassium channels, activated nitric oxide synthase (NOS), or the opening of Cl- channels. The purpose of this study was to further investigate the mechanism of the hyperpolarization of the larval Drosophila muscle due to exposure of LPS using several different experimental paradigms. It appears this response is unlikely related to activation of the Na-K pump or Ca2+ influx. The unknown activation of a K+ efflux could be responsible. This will be an important factor to consider in treatments of bacterial septicemia and cellular energy demands.

Antibacterial Activity of Biosynthesized Selenium Nanoparticles Using Extracts of Calendula officinalis against Potentially Clinical Bacterial Strains

The use of selenium nanoparticles (SeNPs) in the biomedical area has been increasing as an alternative to the growing bacterial resistance to antibiotics. In this research, SeNPs were synthesized by green synthesis using ascorbic acid (AsAc) as a reducing agent and methanolic extract of Calendula officinalis L. flowers as a stabilizer. Characterization of SeNPs was performed by UV-vis spectrophotometry, infrared spectrophotometry (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) techniques. SeNPs of 40–60 nm and spherical morphologies were obtained. The antibacterial activity of marigold extracts and fractions was evaluated by disk diffusion methodology. The evaluation of SeNPs at different incubation times was performed through the colony-forming unit (CFU) count, in both cases against Serratia marcescens, Enterobacter cloacae, and Alcaligenes faecalis bacteria. Partial antibacterial activity was observed with methanolic extracts of marigold leaves and flowers and total inhibition with SeNPs from 2 h for S. marcescens, 1 h for E. cloacae, and 30 min for A. faecalis. In addition, SeNPs were found to exhibit antioxidant activity. The results indicate that SeNPs present a potentiated effect of both antimicrobial and antioxidant activity compared to the individual use of marigold extracts or sodium selenite (Na₂SeO₃). Their application emerges as an alternative for the control of clinical pathogens.

A complicated case of Serratia marcescens catheter-related bloodstream infection misdiagnosed as hypersensitivity reactions to bicarbonate dialysate containing acetate

Recurrent fever during/post-dialysis can occur due to infectious or non-infectious causes. We present the case of a 79-year-old patient who had persistent post-dialysis fever after long-term tunneled central venous catheterization with acetate-containing bicarbonate dialysate. Drug-induced lymphocyte stimulation test (DLST) was positive for acetate dialysate, and he was suspected of having acetate dialysate-induced hypersensitivity reaction. However, switching to acetate-free dialysate did not attenuate the fever. Since Serratia marcescens had been isolated twice from the blood, catheter-related bloodstream infection (CRBSI) was suspected. The culture of the catheter tip confirmed CRBSI caused by S. marcescens. Elevation of β-d-glucan levels and appearance of pulmonary nodular shadow on chest computed tomography images indicated complicated fungal infections. Administration of antibiotics and antifungals led to resolution of the pulmonary nodular shadow with attenuation of fever and C-reactive protein levels. DLST for acetate dialysate was negative, and its reuse did not aggravate the symptoms; hence, the first result was considered false-positive. An indwelling catheter is a risk factor for S. marcescens-related CRBSI, which leads to post-dialysis fever. Hypersensitivity reactions to dialysates must be diagnosed considering the clinical course and DLST results.

Carbapenem-resistant Serratia marcescens bloodstream infection in hematopoietic stem cell transplantation patients: Will it be the next challenge?

Surveillance programs have been reporting decreasing rates of carbapenem-sensitivity in Serratia marcescens, leading to a concern regarding the few remaining therapeutic options to treat these multidrug-resistant (MDR) organisms. Here, we describe a case series of 11 stem cell hematopoietic transplantation patients infected (N = 6) or colonized (N = 5) by carbapenem-resistant S marcescens (CrSm) from 2010 to 2013. The comorbidities found were acute renal insufficiency (3/11), neutropenia (7/11), and mucositis (8/11), and the mortality rate was 64%. KPC was the most prevalent carbapenemase detected (8/11) and tigecycline and gentamicin were the antimicrobials used as treatment.

Serrating through vascular access catheters: a great masquerader with severe systemic manifestations

Serratia marcescens, time and again, has demonstrated its ability to easily adhere and infect vascular access catheters, making them a bona fide source of hospital outbreaks and contributing to adverse patient outcomes. We present a unique case of a severe recurrent Serratia infection, leading to persistent bacteria in the blood, haematogenous dissemination and subsequent development of abscesses, to a degree not reported in the literature before. These infections are exceedingly challenging to eradicate, owing to multiple virulence mechanisms and the deep seeding ability of this microorganism. Serratia infections require a multifaceted approach with intricacies in identification, therapeutics and surveillance, all of which are sparsely reported in the literature and reviewed in this report.

Successful treatment of Serratia Marcescens peritonitis in a patient receiving peritoneal dialysis

An old man receiving peritoneal dialysis was diagnosed with Serratia marcescens peritonitis, a rare case with poor prognosis. Powerful antibiotics based on culture results and enough duration cured the case successfully despite its high virulence.

Draft Genome Sequence of Serratia marcescens Strain ZZCCN01, Isolated from the Cardiac Blood of a Beef Cow

Serratia marcescens strain ZZCCN01 was isolated from the cardiac blood of a dead beef cow with a lung infection and a foam-like secretion from the nostril. Here, we introduce the 5.1-Mb draft genome sequence, which comprises 105 scaffolds, and the corresponding annotation.

Blood urea nitrogen to serum albumin ratio independently predicts 30-day mortality and severity in patients with Escherichia coli bacteraemia

BACKGROUND

Elevated blood urea nitrogen to serum albumin (BUN/ALB) ratio had been identified as an independent risk factor related to mortality in community-acquired and hospital-acquired pneumonia. This study aimed to investigate whether this clinical index can predict the clinical outcomes of E. coli bacteraemia.

MATERIAL AND METHODS

Clinical data were collected from patients with E. coli bacteraemia attended at our hospital between January 2012 and December 2018. The endpoints were mortality within 30 days after the diagnosis of E. coli bacteraemia and intensive care (IC) requirement. Cox regression analysis was performed to evaluate the risk factors.

RESULTS

A total of 398 patients with E. coli bacteraemia were enrolled in this study and 56 patients died within 30 days after bacteraemia onset. Multivariate Cox regression analysis showed that age greater than 65 years, lymphocyte count<.8×10e9/L, elevated BUN/ALB ratio, increased SOFA score, carbapenem resistance, central venous catheterization before onset of bacteraemia, and infection originating from abdominal cavity were independent risk factors for 30-day mortality (P<.05). The risk factors associated with IC requirement were similar to those for 30-day mortality except central venous catheterization before onset of bacteraemia. The area under the receiver-operating characteristic curve for BUN/ALB ratio predicting 30-day mortality and IC requirement was similar to that for SOFA score, but higher than that for lymphocyte count. The cut-off points of BUN/ALB ratio to predict 30-day mortality and IC requirement were both .3.

CONCLUSIONS

BUN/ALB ratio is a simple but independent predictor of 30-day mortality and severity in E. coli bacteraemia. A higher BUN/ALB ratio at the onset of bacteraemia predicts a higher mortality rate and IC requirement.

The Effect of Bacterial Endotoxin LPS on Serotonergic Modulation of Glutamatergic Synaptic Transmission

The release of the endotoxin lipopolysaccharides (LPS) from gram-negative bacteria is key in the induction of the downstream cytokine release from cells targeting cells throughout the body. However, LPS itself has direct effects on cellular activity and can alter synaptic transmission. Animals experiencing septicemia are generally in a critical state and are often treated with various pharmacological agents. Since antidepressants related to the serotonergic system have been shown to have a positive outcome for septicemic conditions impacting the central nervous system, the actions of serotonin (5-HT) on neurons also exposed to LPS were investigated. At the model glutamatergic synapse of the crayfish neuromuscular junction (NMJ), 5-HT primarily acts through a 5-HT2A receptor subtype to enhance transmission to the motor neurons. LPS from Serratia marcescens also enhances transmission at the crayfish NMJ but by a currently unknown mechanism. LPS at 100 µg/mL had no significant effect on transmission or on altering the response to 5-HT. LPS at 500 µg/mL increased the amplitude of the evoked synaptic excitatory junction potential, and 5-HT in combination with 500 µg/mL LPS continued to promote enhanced transmission. The preparations maintained responsiveness to serotonin in the presence of low or high concentrations of LPS.

Epidemiology of Serratia Bloodstream Infections Among Hospitalized Children in the United States, 2009-2016

Serratia can cause serious bloodstream infections (BSIs). This retrospective cohort study identified 5,312 pediatric inpatient encounters with BSIs from 2009 to 2016, of which 82 (0.01%) had Serratia BSIs. The rate among hospitalized patients increased significantly from 0.4 in 2009 to 1.0 in 2016 per 10,000 admissions. Risk factors differed and outcomes were worse for Serratia BSIs compared with non-Serratia BSIs.

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.

Proteomic profiling of Serratia marcescens by high-resolution mass spectrometry

Introduction: Serratia marcescens, an opportunistic human pathogen, is reported as an important cause of nosocomial infection and outbreaks. Although the genome of S. marcescens (ATCC 13880) was completely sequenced by 2014, there are no studies on the proteomic profile of the organism. The objective of the present study is to analyze the protein profile of S. marcescens (ATCC 13880) using a high resolution mass spectrometry (MS). Methods: Serratia marcescens ATCC 13880 strain was grown in Luria-Bertani broth and the protein extracted was subjected to trypsin digestion, followed by basic reverse phase liquid chromatography fractionation. The peptide fractions were then analysed using Orbitrap Fusion Mass Spectrometry and the raw MS data were processed in Proteome Discoverer software. Results: The proteomic analysis identified 15 009 unique peptides mapping to 2541 unique protein groups, which corresponds to approximately 54% of the computationally predicted protein-coding genes. Bioinformatic analysis of these identified proteins showed their involvement in biological processes such as cell wall organization, chaperone-mediated protein folding and ATP binding. Pathway analysis revealed that some of these proteins are associated with bacterial chemotaxis and beta-lactam resistance pathway. Conclusion: To the best of our knowledge, this is the first high-throughput proteomics study of S. marcescens (ATCC 13880). These novel observations provide a crucial baseline molecular profile of the S. marcescens proteome which will prove to be helpful for the future research in understanding the host-pathogen interactions during infection, elucidating the mechanism of multidrug resistance, and developing novel diagnostic markers or vaccine for the disease.

In vivo acquisition and risk of inter-species spread of bla KPC-3-plasmid from Klebsiella pneumoniae to Serratia marcescens in the lower respiratory tract

In recent years, Serratia marcescens has emerged as an important agent of hospital-acquired infections, such as pneumonia, urinary tract infection, septicaemia and meningitis, particularly in vulnerable patients. Compared to Klebsiella pneumoniae and Escherichia coli, S. marcescens is less commonly associated with bla _KPC genes, yet few cases of plasmid transmission at the gastrointestinal level from K. pneumoniae carbapenemase (KPC)-producing Enterobacterales to S. marcescens have been described. Here we report a case of in vivo acquisition, during a 3-month period of hospitalization in the intensive care unit, of a bla _KPC-3 gene carried by a pKpQIL-IT plasmid, and its probable transmission at the bronchial level among different species of Enterobacterales, including K. pneumoniae and S. marcescens. By using whole genome sequence analyses we were able provide insight into the dynamics of carbapenem-resistance determinants acquisition in the lower respiratory tract, a novel anatomical region for such plasmid transmission events, that usually involve the gastrointestinal tract. The co-presence at the same time of both wild-type and resistant Enterobacterales could have been the critical factor leading to the spread of plasmids harbouring carbapenem-resistance genes, of particular importance during surveillance screenings. The possibility of such an event may have significant consequences in terms of antimicrobial treatment, with a potential limitation of therapeutic options, thereby further complicating the clinical management of high-risk critically ill patients.

Extracted chitosan disrupts quorum sensing mediated virulence factors in Urinary tract infection causing pathogens

Quorum sensing (QS) plays an important role during the aetiology of urinary tract infection (UTI), as several virulence factors are under the regulation of QS. Pseudomonas aeruginosa and Serratia marcescens, the primary causative agents of UTI, employ acyl homoserine lactone (AHL) as signal molecules to coordinate various virulence factors. In this present study, chitosan extracted from the marine crab Portunus sanguinolentus was screened for its ability to inhibit the QS-signaling molecules of P. aeruginosa (PA01) and few clinical isolates of P. aeruginosa and S. marcescens. The extracted chitosan on comparison with a commercial chitosan showed significant inhibition of several QS-dependent virulence factors in P. aeruginosa and S. marscenes. Furthermore, qPCR analysis was carried out to confirm the down-regulation of fimA, fimC and flhD genes involved in adhesion and pathogenesis of S. marcescens and lasI and rhlI genes that governs the P. aeruginosa quorum sensing system. Moreover, the chitosan when coated on a catheter was also able to disrupt the mature biofilms which was revealed by scanning electron microscopy. Collectively, the present study showcases the QS inhibitory property of extracted chitosan from crab shells which is being discarded as a recalcitrant biowaste.

The effects of bacterial endotoxin LPS on synaptic transmission at the neuromuscular junction

The direct action of bacterial lipopolysaccharides (LPS) endotoxin was shown to enhance synaptic transmission and hyperpolarize the membrane potential at low doses, but block glutamatergic receptors and decrease observable spontaneous events at a high dosage. The dosage effects are LPS type specific. The hyperpolarization is not due to voltage-gated potassium channels or to activation of nitric oxide synthase (NOS). The effects are induced directly by LPS, independent of an immune response.

Whole-genome-based analysis reveals multiclone Serratia marcescens outbreaks in a non-Neonatal Intensive Care Unit setting in a tertiary care hospital in India

We report the use of next generation sequencing (NGS) for investigating an outbreak of 13 cases of Serratia marcescens blood stream infections in a non-Neonatal Intensive Care Unit (non-NICU) setting in a tertiary care hospital in India over 5 months. Thirteen cases of sepsis due to S. marcescens were identified in various Intensive Care Units (ICUs) over 5 months. Environmental surveillance identified isolates in the adult ICU (AICU). Antibiogram did not correlate with timeline. Sequencing libraries were prepared using Nextera XT chemistry (Illumina). Based on NGS, two clusters were identified. Cluster 1 had environmental and clinical isolates from the AICU and cluster 2 were isolates from the Coronary Care Unit (CCU). NICU and Paediatric ICU isolates did not belong to any cluster. Polyclonal outbreaks best identified by NGS can occur simultaneously. Good infection prevention practices like hand hygiene for compounded medicines and surface cleaning helped end the outbreak.

Molecular dynamics simulation analysis of conessine against multi drug resistant Serratia marcescens

Ornithine decarboxylase (ODC) is an immediate precursor of polyamine biosynthesis in Serratia marcescens and a potential target for inhibition of its growth. We predicted the 3D structural conformation of ODC enzyme and validated it using MDS in our previous study. In this current study, the potential inhibitors of ODC were obtained by virtual screening of potential inhibitors from ZINC database and studied in depth for their different binding pose. Among the ten virtually screened inhibitors, Conessine exhibited the best binding with ODC and its inhibition property was studied further by MDS studies. The natural compound conessine is isolated from plant Holarrhena antidysenterica and it is studied against ODC of Serratia marcenses for its inhibitory potentials. This revealed unforeseen twisted position in root mean square fluctuation (RMSF) and ODC modelled conformation that influenced ligand binding. Both predicted model and ligand bound model were compared and found to be stable with Root Mean Square Deviation (RMSD) of approximately 7 nm and 0.25 nm to that of crystallographic structure over simulation time of 55 ns and 70 ns respectively. This work paves the way for future development of new drugs against nosocomial diseases caused by Serratia marcescens.

Clinical characteristics of patients with Ochrobactrum anthropi bloodstream infection in a Chinese tertiary-care hospital: A 7-year study

BACKGROUND

Ochrobactrum anthropi has become an emerging pathogen for bloodstream infection (BSI).

METHODS

From January 1st 2010 to June 30th 2017, inpatients with one or more blood cultures positive for O. anthropi isolates at Chinese People's Liberation Army General Hospital in Beijing, China, were enrolled in this study. Clinical and laboratory data were collected by reviewing electronic records.

RESULTS

A total of 11 patients with O. anthropi BSI were identified, of which 10 patients survived. There were 6 males and 5 females, whose age ranged from 2 to 83 years. 7 infections were hospital-acquired. In 8 cases O. anthropi was the only pathogen. The most common symptoms of O. anthropi BSI were fever (100%) and disorders of consciousness (45.5%). All patients had undergone indwelling catheter placement. O. anthropi isolates in this study were most susceptible to levofloxacin (100%), ciprofloxacin (85.7%), imipenem (85.7%) and cotrimoxazole (85.7%), while they were widely resistant to penicillins and cephalosporins.

CONCLUSIONS

O. anthropi BSI usually happens in patients with indwelling catheters, and often begins with no distinctive symptom or laboratory finding. O. anthropi seldom form polymicrobial BSIs. Quinolones and carbapenems are optimal antibiotics for O. anthropi BSI. Catheter removal is essential when O. anthropi BSI happens recurrently.

Dynamic Course of Serratia marcescens Pulmonic Valve Endocarditis Resulting in Submassive PE and Valve Replacement

This report illustrates a case of a 42-year-old male with a history of intravenous drug abuse who presented with septic shock. Diagnostic studies, including a transthoracic echocardiogram, chest computed tomography angiography, transesophageal echocardiogram, and blood cultures ultimately revealed Serratia marcescens pulmonic valve infective endocarditis that was treated with intravenous antibiotics. In addition to the rare form of endocarditis and bacterium involved, this case brings into awareness the dynamic nature of the hospital course that requires vigilance in responding to hypotensive episodes for consideration of pulmonary embolism. Surgical valve replacement was opted for due to such a complication in addition to the large size of the vegetation, 2.5 cm.

Sudden death of an Indian peafowl (Pavo cristatus) at a zoo due to non-pigmented Serratia marcescens infection

A 16-year-old female Indian peafowl (Pavo cristatus) died two days after recognition of conjunctivitis in the right eye, anorexia and depression. Gross necropsy revealed a thick pseudomembrane under the eyelid and hydropericardium. Histopathological examination revealed hepatocellular necrosis, sinusoidal and vascular congestion and infiltrated inflammatory cells. Infiltration by inflammatory cells was noted in the epicardium. The lungs had mild interstitial pneumonia with the extensive congestion within the capillaries of the air sacs. Tubular interstitial congestion and necrosis was noted in the kidneys. Bacterial culture and nucleotide sequencing of the inflammatory specimens identified the causative agent as Serratia marcescens, an uncommon bacterium in birds. In summary, this study describes the sudden death of an Indian peafowl due to S. marcescens infection, which is rarely seen in animals.

The sword of Damocles for the splenectomised: death by OPSI

The overwhelming post splenectomy infection (OPSI) in splenectomised patients is a rare but severe infection mostly caused by encapsulated bacteria.

We analyse the case of a 65-year-old female patient who was presented with clinical and laboratory findings indicating gastroenteritis. Two years years before admission, the patient underwent a splenectomy for a two stage splenic rupture following resuscitation for pulmonary embolism. Immunisation of the patient was complete and timely. As a result of the unspecific clinical presentation, there was a delay in administration of antibiotics. However, administration of antibiotics induced a fulminant shock. The patient died 4 hours after attending the hospital due to a pneumococcal sepsis.

The discussion highlights epidemiological and pathophysiological aspects and potential prevention strategies in the international context. Vaccination failed in our patient as the isolated pneumococcal strain (serogroup: 12F) is usually covered by the 23-valent pneumococcal polysaccharide vaccination (Pneumovax^®). The case reported here indicates that there may be a potential benefit of prophylactic antibiotic treatment within the first 3 years after splenectomy for patients above the age of 65 years. Awareness of OPSI (prevention strategies, symptoms and treatment) among patients and their treating physicians is crucial for the improvement of prognosis. We partly address these issues in a standard operating procedure for the assessment of splenectomised patients in our departments of emergency medicine.