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

Designing potential lead compounds targeting aminoglycoside N (6')-acetyltransferase in Serratia marcescens: A drug discovery strategy

Serratia marcescens is an opportunistic human pathogen that causes urinary tract infections, ocular lens infections, and respiratory tract infections. S. marcescens employs various defense mechanisms to evade antibiotics, one of which is mediated by aminoglycoside N-acetyltransferase (AAC). In this mechanism, the enzyme AAC facilitates the transfer and linkage of the acetyl moiety from the donor substrate acetyl-coenzyme A to specific positions on antibiotics. This modification alters the antibiotic's structure, leading to the inactivation of aminoglycoside antibiotics. In the current scenario, antibiotic resistance has become a global threat, and targeting the enzymes that mediate resistance is considered crucial to combat this issue. The study aimed to address the increasing global threat of antibiotic resistance in Serratia marcescens by targeting the aminoglycoside N-acetyltransferase (AAC (6')) enzyme, which inactivates aminoglycoside antibiotics through acetylation. Due to the absence of experimental structure, we constructed a homology model of aminoglycoside N (6')-acetyltransferase (AAC (6')) of S. marcescens using the atomic structure of aminoglycoside N-acetyltransferase AAC (6')-Ib (PDB ID: 1V0C) as a template. The stable architecture and integrity of the modelled AAC (6') structure were analyzed through a 100 ns simulation. Structure-guided high-throughput screening of four small molecule databases (Binding, Life Chemicals, Zinc, and Toslab) resulted in the identification of potent inhibitors against AAC (6'). The hits obtained from screening were manually clustered, and the five hit molecules were shortlisted based on the docking score, which are observed in the range of -17.09 kcal/mol to -11.95 kcal/mol. These selected five molecules displayed acceptable pharmacological properties in ADME predictions. The binding free energy calculations, and molecular dynamics simulations of ligand bound AAC (6') complexes represented higher affinity and stable binding. The selected molecules demonstrated stable binding with AAC (6'), indicating their strong potential to hamper the binding of aminoglycoside in the respective site. and thereby inhibit. This process mitigates enzyme mediated AAC (6') activity on aminoglycosides and reverse the bactericidal function of aminoglycosides, and also this method could serve as a platform for the development of potential antimicrobials.

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.

Synthesis and evaluation of antibacterial and antibiofilm agents based on phenylamino-substituted 1,4-benzoquinones

Aim: This work describes the synthesis and antimicrobial evaluation of 6-aminated 1,4-benzoquinones (6-AQs) against seven resistant pathogens.Materials & methods: The 6-AQs, synthesized via a Michael addition reaction between bromoquinone and p-substituted anilines, were assessed for their antimicrobial activity through both in vitro and in silico analyses.Results: Bromoquinone and 6-AQs with electron-withdrawing groups demonstrated activity against Pseudomonas aeruginosa, with minimum inhibitory concentrations ranging from 16 to 128 μg/ml, comparable to standard antimicrobials. Two derivatives exhibited minimum inhibitory concentrations values against methicillin-resistant Staphylococcus aureus ranging from 64 to 128 μg/ml. These compounds demonstrated both bacteriostatic and bactericidal effects, and antibiofilm features.Conclusion: The 6-AQs 19g and 19f showed a promising antimicrobial profile, indicating their potential as new therapeutic options.

Microbial richness and air chemistry in aerosols above the PBL confirm 2,000-km long-distance transport of potential human pathogens

The existence of viable human pathogens in bioaerosols which can cause infection or affect human health has been the subject of little research. In this study, data provided by 10 tropospheric aircraft surveys over Japan in 2014 confirm the existence of a vast diversity of microbial species up to 3,000 m height, which can be dispersed above the planetary boundary layer over distances of up to 2,000 km, thanks to strong winds from an area covered with massive cereal croplands in Northeast (NE) Asia. Microbes attached to aerosols reveal the presence of diverse bacterial and fungal taxa, including potential human pathogens, originating from sewage, pesticides, or fertilizers. Over 266 different fungal and 305 bacterial genera appeared in the 10 aircraft transects. Actinobacteria, Bacillota, Proteobacteria, and Bacteroidetes phyla dominated the bacteria composition and, for fungi, Ascomycota prevailed over Basidiomycota. Among the pathogenic species identified, human pathogens include bacteria such as Escherichia coli, Serratia marcescens, Prevotella melaninogenica, Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus saprophyticus, Cutibacterium acnes, Clostridium difficile, Clostridium botulinum, Stenotrophomonas maltophilia, Shigella sonnei, Haemophillus parainfluenzae and Acinetobacter baumannii and health-relevant fungi such as Malassezia restricta, Malassezia globosa, Candida parapsilosis and Candida zeylanoides, Sarocladium kiliense, Cladosporium halotolerans, and Cladosporium herbarum. Diversity estimates were similar at heights and surface when entrainment of air from high altitudes occurred. Natural antimicrobial-resistant bacteria (ARB) cultured from air samples were found indicating long-distance spread of ARB and microbial viability. This would represent a novel way to disperse both viable human pathogens and resistance genes among distant geographical regions.

In-host intra- and inter-species transfer of blaKPC-2 and blaNDM-1 in Serratia marcescens and its local and global epidemiology

OBJECTIVES

The aim of this study was to investigate interspecies transfer of resistance gene blaNDM-1 and intraspecies transfer of resistance gene blaKPC-2 in Serratia marcescens, and explore the epidemical and evolutionary characteristics of carbapenemase-producing S. marcescens (CPSM) regionally and globally.

METHODS

Interspecies and intraspecies transfer of blaKPC-2- or blaNDM-1 were identified by antimicrobial susceptibility testing, plasmid conjugation and curing, discovery of transposable units (TUs), outer membrane vesicles (OMVs), qPCR, whole-genome sequencing (WGS) and bioinformatic analysis. The genomic evolution of CPSM strains was explored by cgSNP and maximum-likelihood phylogenetic tree.

RESULTS

CPSM S50079 strain, co-carrying blaKPC-2 and blaNDM-1 on one plasmid, was isolated from the blood of a patient with acute pancreatitis and could generate TUs carrying either blaKPC-2 or blaNDM-1. The interspecies transfer of blaNDM-1-carrying plasmid from Providencia rettgeri P50213, producing the identical blaNDM-1-carrying TUs, to S. marcescens S50079K, an S50079 variant via plasmid curing, was identified through blaNDM-1-harbouring plasmid conjugation and OMVs transfer. Moreover, the intraspecies transfer of blaKPC-2, mediated by IS26 from plasmid to chromosome in S50079, was also identified. In another patient, who underwent lung transplantation, interspecies transfer of blaNDM-1 carried by IncX3 plasmid was identified among S. marcescens and Citrobacter freundii as well as Enterobacter hormaechei via plasmid transfer. Furthermore, 11 CPSM from 349 non-repetitive S. marcescens strains were identified in the same hospital, and clonal dissemination, with carbapenemase evolution from blaKPC-2 to both blaKPC-2 and blaNDM-1, was found in the 8 CPSM across 4 years. Finally, the analysis of 236 global CPSM from 835 non-repetitive S. marcescens genomes, retrieved from the NCBI database, revealed long-term spread and evolution worldwide, and would cause the convergence of more carbapenemase genes.

CONCLUSIONS

Interspecies transfer of resistance gene blaNDM-1 and intraspecies transfer of resistance gene blaKPC-2 in CPSM were identified. Nosocomial and global dissemination of CPSM were revealed and more urgent surveillance was acquired.

In the Depths of Wash Water: Isolation of Opportunistic Bacteria from Fresh-Cut Processing Plants

The fruit and vegetable industry in post-harvest processing plants is characterized by a substantial consumption of water resources. Wash waters may serve as an environment for the periodic or permanent habitation of microorganisms, particularly if biofilm forms on the inner walls of tanks and flushing channels. Despite the implementation of integrated food safety monitoring systems in numerous countries, foodborne pathogens remain a global public health and food safety concern, particularly for minimally processed food products such as vegetables and fruits. This necessitates the importance of studies that will explore wash water quality to safeguard minimally processed food against foodborne pathogen contamination. Therefore, the current study aimed to isolate and identify bacteria contaminating the wash waters of four fresh-cut processing plants (Poland) and to evaluate the phenotypic antibiotic resistance profiles in selected species. Bacteria were isolated using membrane filtration and identified through mass spectrometry, followed by antibiotic susceptibility testing according to EUCAST guidelines. The results revealed that the level of contamination with total aerobic bacteria in the water ranged from 1.30 × 106 cfu/mL to 2.54 × 108 cfu/mL. Among the isolates, opportunistic pathogens including Enterococcus faecalis, Pseudomonas aeruginosa, Klebsiella oxytoca, Klebsiella pneumoniae, Serratia marcescens, and Proteus vulgaris strains were identified. An especially noteworthy result was the identification of cefepime-resistant K. oxytoca isolates. These findings highlight the importance of monitoring the microbial microflora in minimally processed foods and the need for appropriate sanitary control procedures to minimize the risk of pathogen contamination, ensuring that products remain safe and of high quality throughout the supply chain.

Prevalence and distribution of carbapenem-resistant Enterobacterales in companion animals: A nationwide study in the United States using commercial laboratory data

BACKGROUND

Carbapenem-resistant Enterobacterales (CRE) are a concern in both human and animal medicine globally. Despite extensive research in humans, limited data exist on CRE in companion animals, with a lack of nationwide prevalence estimates.

HYPOTHESIS/OBJECTIVES

To assess the occurrence and trends of CRE in cats and dogs across the United States by analyzing 4 years of commercial antimicrobial susceptibility testing (AST) data.

ANIMALS

Between 2019 and 2022, 477 426 ASTs were conducted on Enterobacterales isolates against imipenem. Isolates were derived from 379 598 dogs and 97 828 cats. Animal origin was not disclosed.

METHODS

In this retrospective study, antimicrobial susceptibility test data from IDEXX Laboratories were analyzed. Analysis included resistance estimations to imipenem stratified by sampling site, an assessment of resistance patterns over time and location, and the application of space-time cluster analysis to identify potential outbreaks. Antibiograms were produced for carbapenem-resistant isolates.

RESULTS

Susceptibility to imipenem was high, at 98.86%. Temporal analysis indicated stability in susceptibility, with an unexplained reduction in susceptible isolates in June 2019. Spatial analysis identified 2 high-risk clusters along the Western Coast (relative risk [RR]: 23.26; P < .001) and in Texas (RR: 10.72; P < .001) in that month. Three other clusters were found, in Missouri (RR: 39.55; P = .038), Florida (RR: 4.53; P < .001), and New York (RR: 9.20; P < .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

CRE are present at a low prevalence in dogs and cats across the United States. Variations in prevalence across patient-level and environmental factors highlight the need for tailored stewardship programs.

Microbial cell-free DNA-sequencing as an addition to conventional diagnostics in neonatal sepsis

BACKGROUND

Bloodstream infections remain a challenge for neonatologists, as traditional culture-based methods are time-consuming and rely on adequate blood volume. Next-generation sequencing (NGS) offers an alternative, as it can identify microbial cell-free DNA (mcfDNA) in a small blood sample, providing rapid pathogen detection. This study aimed to assess the diagnostic performance of DISQVER®-NGS compared to blood cultures in neonatal patients with suspected sepsis.

METHODS

In neonates with suspected sepsis, blood cultures and samples for NGS were prospectively collected. Patients were divided into four categories: 1) sepsis, blood culture positive, 2) clinical sepsis, culture negative, 3) suspected sepsis, 4) validation cohort.

RESULTS

NGS detected bacterial, viral or fungal mcfDNA in 24 of 82 samples. Blood cultures were collected in 46 of 84 patients (15/46 positive). DISQVER® correctly identified pathogens in 9/15 patients with a positive blood culture, two with intrinsic resistance to their antibiotic regimen. In seven samples NGS reported the mcfDNA of bacteria that could have theoretically grown in culture but did not.

CONCLUSIONS

NGS may enhance sensitivity in sepsis diagnostics by detecting mcfDNA in neonates with suspected sepsis. Interpreting NGS results requires correlation with clinical data, laboratory values, and routine microbiological tests for a comprehensive understanding of the patient's condition.

IMPACT

Conventional blood culture methods have limitations in accuracy and turnaround time. The study aimed to investigate the diagnostic performance of the Next-Generation Sequencing method DISQVER® compared to traditional blood cultures in neonatal patients with suspected sepsis. Our findings suggest that NGS has the potential to augment the precision of conventional diagnostic techniques, can lead to improved detection of pathogens and targeted treatment approaches in neonatal sepsis. It is emphasized that further validation and integration with clinical and microbiological data are required to ensure optimal clinical utility.

Implications of ad-hoc molecular typing for infection control measures in a multi-cluster, multi-phenotypic Serratia marcescens outbreak in a neonatal intensive care unit

BACKGROUND

Serratia marcescens is known to cause outbreaks in neonatal intensive care units (NICUs). Traditionally epidemiological data, antimicrobial resistance patterns and epidemiological typing have been used to guide infection prevention methods. Whole-genome sequencing (WGS) applications such as core-genome multi-locus sequence typing (cgMLST) applied during an outbreak would potentially yield more information.

AIM

To use cgMLST to acquire detailed information on the source and spread of bacteria, enabling more efficient control measures during an S. marcescens outbreak at a NICU.

METHODS

Neonates admitted to the NICU of the Leiden University Medical Center (LUMC) during an outbreak between September 2023 and January 2024, with S. marcescens being cultured, were included. Environmental samples were taken to search for a common source, antibiotic susceptibility testing was performed, and antimicrobial resistance genes were analysed.

FINDINGS

S. marcescens strains from 17 of the 20 positive patients were available for molecular typing. The cgMLST scheme revealed five different complex types consisting of four separate clusters. Multiple clusters made an unidentified persistent environmental source as cause of the outbreak less likely, leading to a quick downscaling of infection prevention measures. Differences were shown in aminoglycoside resistance patterns of isolates within the same complex types and patients.

CONCLUSION

The use of ad-hoc cgMLST provided timely data for rational decision-making during an S. marcescens outbreak at the NICU. Antibiotic phenotyping alone was found not to be suitable for studying clonal spread during this outbreak with S. marcescens.

Serratia Sacroiliitis Secondary to Intravenous Drug Use: A Case Report

Serratia spp. are ubiquitous, opportunistic, and infectious organisms that have historically been known to infect the upper respiratory, urinary, and circulatory systems. This manuscript presents the case of a 35-year-old White female with a past medical history of polysubstance abuse, intravenous drug use (IVDU), and poor dentition who was admitted to a community hospital with complaints of lower back pain for 10 days following the recent completion of treatment for a suspected epidural abscess. Per her report, her last IVDU with fentanyl was 11 days prior, and she admitted to using various sources of water to inject her drugs. Magnetic resonance imaging with contrast was significant for possible infectious sacroiliitis, and blood cultures grew Serratia marcescens. Due to this patient's extensive IVDU history, in-patient ceftriaxone was chosen over discharging the patient with a peripherally inserted central catheter line. Serratia spp.bacteremia with concomitant septic sacroiliitis in the setting of IVDU is an extremely rare presentation. Due to the nonspecific presentation of sacroiliitis, multidrug resistance profile of Serratia spp., and high mortality rate associated with S. marcescens sepsis, early detection and diagnosis is paramount in similar patients with extensive risk factors.

Amelioration of walnut, peony seed and camellia seed oils against D-galactose-induced cognitive impairment in mice by regulating gut microbiota

Diet adjustment will affect the health of gut microbiota, which in turn influences the development and function of the organism's brain through the gut-brain axis. Walnut oil (WO), peony seed oil (PSO) and camellia seed oil (CSO), as typical representatives of woody plant oils, have been shown to have the potential to improve cognitive impairment in mice, but the function mechanisms are not clear. In this study, we comparatively investigated the neuroprotective effects of these three oils on D-galactose (D-gal)-induced cognitive impairment in mice, and found that the ameliorative effect of WO was more prominent. During the behavioral experiments, supplementation with all three oils would improve spatial learning and memory functions in D-gal mice, with a significant reduction in the error times (p < 0.001) and a significant increase in step-down latency (p < 0.001); walnut oil supplementation also significantly increased the number of hidden platform traversals, the target quadrant spent times and percentage of distance (p < 0.05). The results of biomarker analysis showed that WO, in addition to significantly inhibiting D-gal-induced oxidative stress and neuroinflammation as did PSO, significantly increased the ACh content in the mouse brain (p < 0.05) and modulated neurotransmitter levels. The results of further microbiota diversity sequencing experiments also confirmed that dietary supplementation with all three oils affected the diversity and composition of the gut microbiota in mice. Among them, WO significantly restored the balance of the mouse gut microbiota by increasing the abundance of beneficial bacteria (Bacteroidetes, Actinobacteria, Firmicutes) and decreasing the abundance of harmful bacteria (Clostridium, Shigella, Serratia), which was consistent with the results of behavioral experiments and biomarker analyses. Based on the analysis of the fatty acid composition of the three oils and changes in the gut microbiota, it is hypothesized that there is a correlation between the fatty acid composition of the dietary supplement oils and neuroprotective effects. The superiority of WO over PSO and CSO in improving cognitive impairment is mainly attributed to its balanced composition of omega-6 and omega-3 fatty acids.

Nisin Inhibition of Gram-Negative Bacteria

Aims: This study investigates the activity of the broad-spectrum bacteriocin nisin against a large panel of Gram-negative bacterial isolates, including relevant plant, animal, and human pathogens. The aim is to generate supportive evidence towards the use/inclusion of bacteriocin-based therapeutics and open avenues for their continued development. Methods and Results: Nisin inhibitory activity was screened against a panel of 575 strains of Gram-negative bacteria, encompassing 17 genera. Nisin inhibition was observed in 309 out of 575 strains, challenging the prevailing belief that nisin lacks effectiveness against Gram-negative bacteria. The genera Acinetobacter, Helicobacter, Erwinia, and Xanthomonas exhibited particularly high nisin sensitivity. Conclusions: The findings of this study highlight the promising potential of nisin as a therapeutic agent for several key Gram-negative plant, animal, and human pathogens. These results challenge the prevailing notion that nisin is less effective or ineffective against Gram-negative pathogens when compared to Gram-positive pathogens and support future pursuits of nisin as a complementary therapy to existing antibiotics. Significance and Impact of Study: This research supports further exploration of nisin as a promising therapeutic agent for numerous human, animal, and plant health applications, offering a complementary tool for infection control in the face of multidrug-resistant bacteria.

A novel case of cutaneous, nasal and systemic fusariosis in a goat

The clinical findings associated with nasal, cutaneous and systemic fusariosis in a 3-year-old billy Boer goat are summarised. The clinical features, treatment, postmortem findings and laboratory diagnostics are reported and discussed in the context of existing knowledge on mycoses of small ruminants. The goat presented primarily for respiratory signs (inspiratory dyspnoea) with unilateral left-sided mucopurulent nasal discharge, and multifocal variably ulcerative and necrotic cutaneous nodules. Histopathology of nasal and cutaneous biopsies revealed necrotising pyogranulomatous inflammation with intralesional septate hyphal elements that correlated with culture of Fusarium oxysporum. The patient continued to deteriorate clinically during treatment with oxytetracycline and meloxicam, with the addition of sodium iodide and potassium iodide, and was humanely euthanased. Postmortem examination revealed multifocal nodular lesions throughout the kidneys, abdominal lymph nodes and lungs. These lesions were consistent with those identified antemortem from which F. oxysporum was cultured. Although treatment was unsuccessful, to the author's knowledge, no instance of rhinofacial or systemic caprine infection with Fusarium spp. has been documented in the veterinary literature, making this the first recognised instance of this form of infection in small ruminant species.

Increased Proteolytic Activity of Serratia marcescens Clinical Isolate HU1848 Is Associated with Higher eepR Expression

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.

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.

Neonatal intensive care units: extended spectrum β-lactamase genes and biofilm formation by Serratia marcescens

BACKGROUND

The increasing cases of bloodstream infections among children at neonatal intensive care units (NICUs) led this work to investigate biofilm production, antibiotics and the presence of ESβL genes in Serratia marcescens (S. marcescens) strains isolated from blood.

METHODS

Twenty S. marcescens strains were isolated and identified by the VITEK-2 system over 7 months from late 2022 to mid-2023 from Ibn Al-Balady Hospital in Baghdad. Kirby-Bauer test was used to measure antibiotic susceptibility.

RESULTS

The results revealed that 95% of twenty S. marcescens isolates were non-susceptible to Ampicillin and Amoxicillin-clavulanic. Furthermore, S. marcescens isolates showed a high sensitivity rate 70% toward Imipenem. All S. marcescens strains 100% were produced biofilm. This work clarifies that, out of 20 S. marcescens strains, 80% were harbored ESβL genes. The coexistence of blaTEM, blaCTX and blaSHV genes was shown in 43.75% of strains, while 56.25% of S. marcescens strains harbored single ES[Formula: see text]L genes. The biofilm values increase with the accuracy of EsβL genes. Phylogenetic analyses based on the sequence of blaCTX-M and blaTEM were done with closely related genes in the GenBank using MEGA6 software.

CONCLUSIONS

The distribution of blaTEM, blaCTX and blaSHV genes among local S. marcescens strains may be attributed to the indiscriminate use of antibiotics. The results confirmed the spread of ESβL genes in S. marcescens from blood infections among newborn infants.

Rare post-operative intracranial abscess due to Serratia marcescens: what we can learn from it?

BACKGROUND

Nosocomial infections caused by Serratia marcescens mostly occurred in pediatrics and it was very rarely reported after adult surgery. Here, an intracranial abscess caused by Serratia marcescens was reported. We report a rare case of a postoperative intracranial abscess caused by Serratia marcescens in a 63-year-old male patient with a left parietal mass. The patient underwent resection of the mass on June 1, 2022, and the postoperative pathology revealed an angiomatous meningioma, WHO I. He then experienced recurrent worsening of right limb movements, and repeated cranial CT scans showed oozing blood and obvious low-density shadows around the operation area. Delayed wound healing was considered. Subsequently, a large amount of pus was extracted from the wound. The etiological test showed that Serratia marcescens infection occurred before the removal of the artificial titanium mesh. Antibiotics were initiated based on the results of drug susceptibility tests. At present, the patient is recovering well and is still closely monitored during follow-up.

CONCLUSION

It is rare for Serratia marcescens to cause brain abscesses without any obvious signs of infection. This report provided in detail our experience of a warning postoperative asymptomatic brain abscess caused by an uncommon pathogen.

Salicylic acids and pathogenic bacteria: new perspectives on an old compound

Salicylic acids have been used in human and veterinary medicine for their anti-pyretic, anti-inflammatory, and analgesic properties for centuries. A key role of salicylic acid-immune modulation in response to microbial infection-was first recognized during studies of their botanical origin. The effects of salicylic acid on bacterial physiology are diverse. In many cases, they impose selective pressures leading to development of cross-resistance to antimicrobial compounds. Initial characterization of these interactions was in Escherichia coli, where salicylic acid activates the multiple antibiotic resistance (mar) operon, resulting in decreased antibiotic susceptibility. Studies suggest that stimulation of the mar phenotype presents similarly in closely related Enterobacteriaceae. Salicylic acids also affect virulence in many opportunistic pathogens by decreasing their ability to form biofilms and increasing persister cell populations. It is imperative to understand the effects of salicylic acid on bacteria of various origins to illuminate potential links between environmental microbes and their clinically relevant antimicrobial-resistant counterparts. This review provides an update on known effects of salicylic acid and key derivatives on a variety of bacterial pathogens, offers insights to possible potentiation of current treatment options, and highlights cellular regulatory networks that have been established during the study of this important class of medicines.

Serratia marcescens-associated subcutaneous abscess in a dog

This report describes the clinical presentation and progression of a Serratia marcescens-associated subcutaneous abscess in a dog with hypothyroidism, hyperadrenocorticism and diabetes mellitus. The S. marcescens isolate was resistant to several antibiotics. Treatment with antibiotics and topical antiseptics was not successful.

Cladosporium sphaerospermum extract inhibits quorum sensing associated virulence factors of Serratia marcescens

Serratia marcescens is now becoming a propensity for its highly antimicrobial-resistant clinical infections. Currently, it provides a novel strategy to prevent and control microbial infection by regulating S. marcescens quorum sensing (QS). Deep-sea-derived fungi are rich in QS bioactive constituents. In this work, the extracts from Cladosporium sphaerospermum SCSGAF0054 showed potent QS-related virulence factors and biofilm-inhibiting activities against S. marcescens NJ01. The swimming motility and multiple virulence factors such as prodigiosin, exopolysaccharide (EPS), lipase, protease and hemolysin were moderately inhibited by the extracts at varied concentrations. The confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM) images revealed that C. sphaerospermum extracts moderately arrested biofilm formation and cell viability. Further, real-time quantitative PCR (RT-qPCR) analysis revealed that expressions of genes associated with virulence factors, flhD, fimA, fimC, bsmA, bsmB, pigA, pigC, and shlA, were significantly down-regulated compared with control. In addition, the extracts combined with imipenem inhibited the QS system of S. marcescens NJ01, disrupted its preformed biofilm, released the intra-biofilm bacteria and killed the bacteria gradually. Therefore, the extracts combined with imipenem can partially restore bacterial drug sensitivity. These results suggest that the extracts from SCSGAF0054 effectively interfere with the QS system to treat S. marcescens infection alone or combining with classical antimicrobial drugs.

Serratia marcescens causing recurrent superficial skin infections in an immunosuppressed patient

Serratia marcescens is a gram-negative bacterium found commonly in water and soil. Initially thought to be non-pathogenic, it is now recognised as an important cause of nosocomial and opportunistic infections. Skin infections are rare, but cases of S. marcescens causing ulcers, abscesses and necrotizing fasciitis have been reported. We report an unusual cutaneous presentation of S. marcescens in an immunosuppressed patient. A 77-year-old man under review for non-melanoma skin cancer in the context of a previous cardiac transplant, presented with an asymptomatic scalp eruption. Immunosuppressive medications included ciclosporin 90 mg twice daily (2.5 mg/kg/day) and mycophenolate mofetil 1 g twice daily. Physical examination revealed well-defined annular and polycyclic patches with brownish crusting across his scalp. Bacterial culture demonstrated a heavy growth of Staphylococcus aureus sensitive to flucloxacillin. The patient was treated with 7 days of flucloxacillin 500 mg four times daily. Despite this, the eruption extended. Skin biopsy demonstrated epidermal spongiosis, florid dermal inflammatory cell infiltrate and abundant bacteria and neutrophils in the parakeratotic crust. Fungal stains were negative as was direct immunofluorescence. Repeat culture demonstrated heavy growth of S. marcescens sensitive to ciprofloxacin. The patient was treated with 10 days of oral ciprofloxacin 500 mg twice daily along with 1% hydrogen peroxide cream topically with significant clinical improvement. Microbiological review indicated that a gram-negative organism was present in the initial scalp swab. In addition, S. marcescens had been detected previously on a skin swab from a recent transient eruption on the torso. Further, a heavy growth of a coliform bacillus was demonstrated in a similar eruption on the chest in 2013. It was concluded that the patient was likely colonised with S. marcescens which appeared to have caused recurrent superficial skin infections over several years. We report this case to highlight an unusual clinical presentation of cutaneous S. marcescens infection. This should be considered in the differential diagnosis of skin eruptions in immunocompromised patients. Clinical information detailing a patient's immunosuppressed state must be supplied on microbiology requests to allow accurate interpretation of results, and consideration of organisms which may otherwise be overlooked or considered contaminants.

Systematic analysis of plasmids of the Serratia marcescens complex using 142 closed genomes

Plasmids play important roles in bacterial genome diversification. In the Serratia marcescens complex (SMC), a notable contribution of plasmids to genome diversification was also suggested by our recent analysis of >600 draft genomes. As accurate analyses of plasmids in draft genomes are difficult, in this study we analysed 142 closed genomes covering the entire complex, 67 of which were obtained in this study, and identified 132 plasmids (1.9-244.4 kb in length) in 77 strains. While the average numbers of plasmids in clinical and non-clinical strains showed no significant difference, strains belonging to clade 2 (one of the two hospital-adapted lineages) contained more plasmids than the others. Pangenome analysis revealed that of the 28 954 genes identified, 12.8 % were plasmid-specific, and 1.4 % were present in plasmids or chromosomes depending on the strain. In the latter group, while transposon-related genes were most prevalent (31.4 % of the function-predicted genes), genes related to antimicrobial resistance and heavy metal resistance accounted for a notable proportion (22.7 %). Mash distance-based clustering separated the 132 plasmids into 23 clusters and 50 singletons. Most clusters/singletons showed notably different GC contents compared to those of host chromosomes, suggesting their recent or relatively recent appearance in the SMC. Among the 23 clusters, 17 were found in only clinical or only non-clinical strains, suggesting the possible preference of their distribution on the environmental niches of host strains. Regarding the host strain phylogeny, 16 clusters were distributed in two or more clades, suggesting their interclade transmission. Moreover, for many plasmids, highly homologous plasmids were found in other species, indicating the broadness of their potential host ranges, beyond the genus, family, order, class or even phylum level. Importantly, highly homologous plasmids were most frequently found in Klebsiella pneumoniae and other species in the family Enterobacteriaceae, suggesting that this family, particularly K. pneumoniae, is the main source for plasmid exchanges with the SMC. These results highlight the power of closed genome-based analysis in the investigation of plasmids and provide important insights into the nature of plasmids distributed in the SMC.

Infection of Multiple Tunneled Dialysis Catheters Resulting From the Contamination of the Chlorhexidine Solution by Serratia marcescens

Tunnelled dialysis catheters continue to be a choice in several patients as hemodialysis access. According to Kidney Disease Outcomes Quality Initiative guidelines, its handling implies disinfection, that can be performed using chlorhexidine solutions. Theoretically, these solutions have bactericidal capacity at concentrations greater than 0.12%. We present a curious situation of failure of the antiseptic process due to contamination of the chlorhexidine solution 4% of aqueous base. In this hemodialysis clinic, three cases of infections by the bacteria Serratia marcescens were identified over 2 weeks - in two of the cases, identified in blood culture, and in the other case in the exudate from the exit site of the catheter. Considering the abnormal number of infections by this agent and the fact that these patients were on different shifts, were treated in different rooms, and handled by different nurses, the antiseptic solutions used in the different hemodialysis rooms were analyzed, as well as a closed package from the same batch. After microbiological tests were performed on the antiseptic solution, we identified the growth of Serratia marcescens. This result identified the culprit as being the contamination of the 4% chlorhexidine solution. The competent authorities were notified, and the disinfection method was changed to use a chlorhexidine alcohol-based solution.

The possibility of using Serratia isolates for the production of biopreparations in the protection of plants against diseases and pests

The agriculture is extremely important for the life of human beings. Therefore, it is needed to control the enemies that destroy vast areas of crops causing great economic losses. Chemical pesticides were the option for many decades, but the damage that they cause to environment and human health led to the idea of changing the use of these for more sustainable options such as biopesticides as a biological control. Among microbial pesticides, Serratia species have been found as suitable options to apply against several pests or pathogens. Serratia species produce a wide range of secondary metabolites with several biological activities such as antifungal, antibacterial, and pesticides which can be used in sustainable agriculture. It has been reported that several Serratia species are able to suppress some crop diseases caused by Fusarium oxysporum, Rhizoctonia solani, Phytophthora parasitica, Sclerotinia sclerotiorum, Verticillium dahlia, and Phytophthora capsici among others. Therefore, they have been used as biocontrol agents in agriculture. In this review, we summarized the genus Serratia describing its history and development and the metabolites it secretes, which are responsible for their antibacterial and antifungal activity. We have analyzed the insecticide capacity of several Serratia species as well antifungal properties of Serratia species against most important crops' pathogens. In conclusion, the use of Serratia as a biological control agent against plant pathogens can be a good option for a sustainable agriculture. More work is needed to assess the safety of the isolated new strains and their effectiveness against pathogens in in vivo conditions.

Storage of Extended Boar Semen at 5 °C Inhibits Growth of Multi-Drug Resistant Serratia marcescens and Klebsiella oxytoca while Maintaining High Sperm Quality

Multi-drug antibiotic resistance of Serratia (S.) marcescens and Klebsiella (K.) oxytoca in boar semen is an emerging threat to pig reproduction and the environment. The aim of this study is to examine the efficiency of a novel hypothermic preservation method to inhibit the growth of these bacterial species in extended boar semen and to maintain the sperm quality. The semen samples extended in an antibiotic-free Androstar Premium extender were spiked with ~10² CFU/mL of S. marcescens or K.oxytoca. Storage at 5 °C for 144 h inhibited the growth of both bacterial species and maintained the sperm quality, whereas bacterial counts increased to more than 10¹⁰ CFU/mL in the 17 °C samples used as positive controls. This was accompanied by an increase in the sperm agglutination and the loss of motility and membrane integrity. We conclude that hypothermic storage is a promising tool to combat resistant bacteria in boar semen and to contribute to the One Health approach.

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.

Neonatal Brain Abscess with Serratia marcescens after Intrauterine Infection: A Case Report

Brain abscesses are a possible complication of bacterial sepsis or central nervous system infection but are uncommon in the neonatal period. Gram-negative organisms often cause them, but Serratia marcescens is an unusual cause of sepsis and meningitis in this age group. This pathogen is opportunistic and frequently responsible for nosocomial infections. Despite the existing antibiotics and modern radiological tools, mortality and morbidity remain significant in this group of patients. We report an unusual unilocular brain abscess in a preterm neonate caused by Serratia marcescens. The infection had an intrauterine onset. The pregnancy was achieved through assisted human reproduction techniques. It was a high-risk pregnancy, with pregnancy-induced hypertension, imminent abortion, and required prolonged hospitalization of the pregnant woman with multiple vaginal examinations. The infant was treated with multiple antibiotic cures and percutaneous drainage of the brain abscess associated with local antibiotic treatment. Despite treatment, evolution was unfavorable, complicated by fungal sepsis (Candida parapsilosis) and multiple organ dysfunction syndrome.

Prevalence and Characterization of Serratia marcescens Isolated from Clinical Bovine Mastitis Cases in Ningxia Hui Autonomous Region of China

Purpose

This study aimed to investigate the prevalence and genetic characterization of Serratia marcescens isolates from clinical bovine mastitis in Ningxia Hui Autonomous Region of China.

Methods

S. marcescens was identified by the polymerase-chain reaction of 16S rRNA gene and sequencing. Antimicrobial susceptibility was tested by the disk diffusion method. Genes of resistance and virulence were determined by the PCR.

Results

Overall, S. marcescens were confirmed from 32 of 2897 (1.1%) mastitis milk samples. These isolates showed high resistance to cefazolin (30/32, 93.8%) and chloramphenicol (28/32, 87.5%). A 12.5% (4/32) of the isolates displayed multidrug resistance (MDR). The most prevalent resistant genes found in S. marcescens were TEM (32/32, 100%) and CTX-M (24/32, 75.0%; CTX-M-15, 14/32, 43.8%; CTX-M-14, 8/32, 25.0%; CTX-M-65, 2/32, 6.3%) for extended-spectrum beta-lactamase, cmlA (28/32, 87.5%) and floR (16/32, 50.0%) for chloramphenicol resistance, SIM-1 (2/32, 6.3%) for carbapenemases, and sdeB (28/32, 87.5%), sdeY (26/32, 81.3%), sdeR (26/32, 81.3%) and sdeD (20/32, 62.5%) for efflux pumps. Moreover, all isolates carried virulence genes flhD, entB, and kpn, and most of them contained mrkD (30/32, 93.8%), ycfM (26/32, 81.3%), bsmB (26/32, 81.3%), pigP (26/32, 81.3%), kfu (24/32, 75.0%) and shlB (24/32, 75.0%).

Conclusion

To our knowledge, this is the first report of genetic determinants for antimicrobial resistance and virulence in S. marcescens isolated from bovine mastitis cases in China. These findings are useful for developing strategies for prevention and treatment of bovine mastitis caused by S. marcescens in China.