Host defense alteration in Caenorhabditis elegans after evolution under ionizing radiation.

BACKGROUND: Adaptation to a stressor can lead to costs on other traits. These costs play an unavoidable role on fitness and influence the evolutionary trajectory of a population. Host defense seems highly subject to these costs, possibly because its maintenance is energetically costly but essential to the survival. When assessing the ecological risk related to pollution, it is therefore relevant to consider these costs to evaluate the evolutionary consequences of stressors on populations. However, to the best of our knowledge, the effects of evolution in irradiate environment on host defense have never been studied. Using an experimental evolution approach, we analyzed fitness across 20 transfers (about 20 generations) in Caenorhabditis elegans populations exposed to 0, 1.4, and 50.0 mGy.h- 1 of 137Cs gamma radiation. Then, populations from transfer 17 were placed in the same environmental conditions without irradiation (i.e., common garden) for about 10 generations before being exposed to the bacterial parasite Serratia marcescens and their survival was estimated to study host defense. Finally, we studied the presence of an evolutionary trade-off between fitness of irradiated populations and host defense. RESULTS: We found a lower fitness in both irradiated treatments compared to the control ones, but fitness increased over time in the 50.0 mGy.h- 1, suggesting a local adaptation of the populations. Then, the survival rate of C. elegans to S. marcescens was lower for common garden populations that had previously evolved under both irradiation treatments, indicating that evolution in gamma-irradiated environment had a cost on host defense of C. elegans. Furthermore, we showed a trade-off between standardized fitness at the end of the multigenerational experiment and survival of C. elegans to S. marcescens in the control treatment, but a positive correlation between the two traits for the two irradiated treatments. These results indicate that among irradiated populations, those most sensitive to ionizing radiation are also the most susceptible to the pathogen. On the other hand, other irradiated populations appear to have evolved cross-resistance to both stress factors. CONCLUSIONS: Our study shows that adaptation to an environmental stressor can be associated with an evolutionary cost when a new stressor appears, even several generations after the end of the first stressor. Among irradiated populations, we observed an evolution of resistance to ionizing radiation, which also appeared to provide an advantage against the pathogen. On the other hand, some of the irradiated populations seemed to accumulate sensitivities to stressors. This work provides a new argument to show the importance of considering evolutionary changes in ecotoxicology and for ecological risk assessment.

Root Rot Management in Common Bean (Phaseolus vulgaris L.) Through Integrated Biocontrol Strategies using Metabolites from Trichoderma harzianum, Serratia marcescens, and Vermicompost Tea.

Common bean (Phaseolus vulgaris L.) is an essential food staple and source of income for small-holder farmers across Africa. However, yields are greatly threatened by fungal diseases like root rot induced by Rhizoctonia solani. This study aimed to evaluate an integrated approach utilizing vermicompost tea (VCT) and antagonistic microbes for effective and sustainable management of R. solani root rot in common beans. Fourteen fungal strains were first isolated from infected common bean plants collected across three Egyptian governorates, with R. solani being the most virulent isolate with 50% dominance. Subsequently, the antagonistic potential of vermicompost tea (VCT), Serratia sp., and Trichoderma sp. was assessed against this destructive pathogen. Combinations of 10% VCT and the biocontrol agent isolates displayed potent inhibition of R. solani growth in vitro, prompting in planta testing. Under greenhouse conditions, integrated applications of 5 or 10% VCT with Serratia marcescens, Trichoderma harzianum, or effective microorganisms (EM1) afforded up to 95% protection against pre- and post-emergence damping-off induced by R. solani in common bean cv. Giza 6. Similarly, under field conditions, combining VCT with EM1 (VCT + EM1) or Trichoderma harzianum (VCT + Trichoderma harzianum) substantially suppressed disease severity by 65.6% and 64.34%, respectively, relative to untreated plants. These treatments also elicited defense enzyme activity and distinctly improved growth parameters including 136.68% and 132.49% increases in pod weight per plant over control plants. GC-MS profiling of Trichoderma harzianum, Serratia marcescens, and vermicompost tea (VCT) extracts revealed unique compounds dominated by cyclic pregnane, fatty acid methyl esters, linoleic acid derivatives, and free fatty acids like oleic, palmitic, and stearic acids with confirmed biocontrol and plant growth-promoting activities. The results verify VCT-mediated delivery of synergistic microbial consortia as a sustainable platform for integrated management of debilitating soil-borne diseases, enhancing productivity and incomes for smallholder bean farmers through regeneration of soil health. Further large-scale validation can pave the adoption of this climate-resilient approach for securing food and nutrition security.

Whole-genome sequencing analysis of multidrug-resistant Serratia marcescens isolates in an intensive care unit in Brazil.

INTRODUCTION: Serratia marcescens is an opportunistic pathogen found ubiquitously in the environment and associated with a wide range of nosocomial infections. This multidrug-resistant bacterium has been a cause of concern for hospitals and healthcare facilities due to its ability to spread rapidly and cause outbreaks. Next generation sequencing genotyping of bacterial isolates has proven to be a valuable tool for tracking the spread and transmission of nosocomial infections. This has allowed for the identification of outbreaks and transmission chains, as well as determining whether cases are due to endogenous or exogenous sources. Evidence of nosocomial transmission has been gathered through genotyping methods. The aim of this study was to investigate the genetic diversity of carbapenemase-producing S. marcescens in an outbreak at a public hospital in Cuiaba, MT, Brazil. METHODOLOGY: Ten isolates of S. marcenses were sequenced and antibiotic resistance profiles analyzed over 12 days. RESULTS: The isolates were clonal and multidrug resistant. Gentamycin and tigecycline had sensitivity in 90% and 80% isolates, respectively. Genomic analysis identified several genes that encode ß-lactamases, aminoglycoside-modifying enzymes, efflux pumps, and other virulence factors. CONCLUSIONS: Systematic surveillance is crucial in monitoring the evolution of S. marcescens genotypes, as it can lead to early detection and prevention of outbreaks.

A rare case of successful treatment of peritoneal dialysis patient with Serratia marcescens peritonitis without catheter removal: case report and literature review.

Serratia marcescens, as a Gram-negative opportunistic pathogen, is a rare cause of peritonitis and has worse clinical outcomes than Gram-positive peritonitis. In this case report, we describe a case of Serratia marcescens associated peritonitis that was successfully cured without catheter removal. A 40-year-old male patient with peritoneal dialysis who worked in the catering industry was admitted to the hospital for 16 hours after the discovery of cloudy peritoneal dialysate and abdominal pain. Ceftazidime and cefazolin sodium were immediately given intravenously as an empirical antibiotic regimen. After detecting Serratia marcescens in the peritoneal diasate culture, the treatment was switched to ceftazidime and levofloxacin. The routine examination of peritoneal dialysate showed a significant decrease in white blood cells, the peritoneal dialysate became clear, and the peritoneal dialysis catheter was retained. The patient was treated for 2 weeks and treated with oral antibiotics for 1 week. It is necessary to further strengthen the hygiene of work environment to prevent Serratia marcescens infection in peritoneal dialysis patients. We recommend that patients with Serratia marcescens associated peritonitis should be treated with a combination of antibiotics as early as possible empirically, and at the same time, the peritoneal dialysis fluid culture should be improved, and the antibiotic regimen should be timely adjusted according to the drug sensitivity results. For patients with clinical symptoms for more than 3 days, considering the strong virulence of Serratia marcescens, whether to use meropenem directly or not can provide a reference for clinical decision-making. Further clinical studies are needed to achieve more precise anti-infective treatment.

Nosocomial outbreak caused by disinfectant-resistant Serratia marcescens in an adult intensive care unit, Hungary, February to March 2022.

In 2022, an outbreak with severe bloodstream infections caused by Serratia marcescens occurred in an adult intensive care unit (ICU) in Hungary. Eight cases, five of whom died, were detected. Initial control measures could not stop the outbreak. We conducted a matched case-control study. In univariable analysis, the cases were more likely to be located around one sink in the ICU and had more medical procedures and medications than the controls, however, the multivariable analysis was not conclusive. Isolates from blood cultures of the cases and the ICU environment were closely related by whole genome sequencing and resistant or tolerant against the quaternary ammonium compound surface disinfectant used in the ICU. Thus, S. marcescens was able to survive in the environment despite regular cleaning and disinfection. The hospital replaced the disinfectant with another one, tightened the cleaning protocol and strengthened hand hygiene compliance among the healthcare workers. Together, these control measures have proved effective to prevent new cases. Our results highlight the importance of multidisciplinary outbreak investigations, including environmental sampling, molecular typing and testing for disinfectant resistance.

PqqF inhibits T6SS secretion by decreasing the pH in Serratia marcescens FS14.

Pyrroloquinoline quinone (PQQ) is a redox cofactor with numerous important physiological functions, and the type VI secretion system (T6SS) is commonly found in Gram-negative bacteria and plays important roles in physiological metabolism of the bacteria. In this study, we found that the deletion of pqqF enhanced the secretion of Hcp-1 in Serratia marcesens FS14 in M9 medium. Transcriptional analysis showed that the deletion of pqqF almost had no effect on the expression of T6SS-1. Further study revealed that the increased secretion of Hcp-1 was altered by the pH changes of the culture medium through the reaction catalyzed by the glucose dehydrogenases in FS14. Finally, we demonstrated that decreased pH of culture medium has similar inhibition effects as PQQ induced on the secretion of T6SS-1. This regulation mode on T6SS by pH in FS14 is different from previously reported in other bacteria. Therefore, our results suggest a novel pH regulation mode of T6SS in S. marcesens FS14, and would broaden our knowledge on the regulation of T6SS secretion.

Pathogenic fungi synergistically cooperate with Serratia marcescens to increase cockroach mortality.

The abuse of chemical insecticides has led to strong resistance in cockroaches, and biopesticides with active ingredients based on insect pathogens have good development prospects; however, their slow effect has limited their practical application, and improving their effectiveness has become an urgent problem. In this study, the interaction between Serratia marcescens and Metarhizium anisopliae enhanced their virulence against Blattella germanica and exhibited a synergistic effect. The combination of S. marcescens and M. anisopliae caused more severe tissue damage and accelerated the proliferation of the insect pathogen. The results of high-throughput sequencing demonstrated that the gut microbiota was dysbiotic, the abundance of the opportunistic pathogen Weissella cibaria increased, and entry into the hemocoel accelerated the death of the German cockroaches. In addition, the combination of these two agents strongly downregulated the expression of Imd and Akirin in the IMD pathway and ultimately inhibited the expression of antimicrobial peptides (AMPs). S. marcescens released prodigiosin to disrupted the gut homeostasis and structure, M. anisopliae released destruxin to damaged crucial organs, opportunistic pathogen Weissella cibaria overproliferated, broke the gut epithelium and entered the hemocoel, leading to the death of pests. These findings will allow us to optimize the use of insect pathogens for the management of pests and produce more effective biopesticides.

Disinfection of sink drains to reduce a source of three opportunistic pathogens, during Serratia marcescens clusters in a neonatal intensive care unit.

OBJECTIVE: Evaluate the effects of five disinfection methods on bacterial concentrations in hospital sink drains, focusing on three opportunistic pathogens (OPs): Serratia marcescens, Pseudomonas aeruginosa and Stenotrophomonas maltophilia. DESIGN: Over two years, three sampling campaigns were conducted in a neonatal intensive care unit (NICU). Samples from 19 sink drains were taken at three time points: before, during, and after disinfection. Bacterial concentration was measured using culture-based and flow cytometry methods. High-throughput short sequence typing was performed to identify the three OPs and assess S. marcescens persistence after disinfection at the genotypic level. SETTING: This study was conducted in a pediatric hospitals NICU in Montréal, Canada, which is divided in an intensive and intermediate care side, with individual rooms equipped with a sink. INTERVENTIONS: Five treatments were compared: self-disinfecting drains, chlorine disinfection, boiling water disinfection, hot tap water flushing, and steam disinfection. RESULTS: This study highlights significant differences in the effectiveness of disinfection methods. Chlorine treatment proved ineffective in reducing bacterial concentration, including the three OPs. In contrast, all other drain interventions resulted in an immediate reduction in culturable bacteria (4-8 log) and intact cells (2-3 log). Thermal methods, particularly boiling water and steam treatments, exhibited superior effectiveness in reducing bacterial loads, including OPs. However, in drains with well-established bacterial biofilms, clonal strains of S. marcescens recolonized the drains after heat treatments. CONCLUSIONS: Our study supports thermal disinfection (>80°C) for pathogen reduction in drains but highlights the need for additional trials and the implementation of specific measures to limit biofilm formation.

Calcium-induced structural transitions are central to the folding, function, and processing of serratiopeptidase zymogen into mature form.

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

Thermally resistant nuclease in Serratia marcescens hinders PCR reactions and degrades PCR products.

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

Vairimorpha (Nosema) ceranae can promote Serratia development in honeybee gut: an underrated threat for bees?

The genus Serratia harbors opportunistic pathogenic species, among which Serratia marcescens is pathogenic for honeybees although little studied. Recently, virulent strains of S. marcescens colonizing the Varroa destructor mite's mouth were found vectored into the honeybee body, leading to septicemia and death. Serratia also occurs as an opportunistic pathogen in the honeybee's gut with a low absolute abundance. The Serratia population seems controlled by the host immune system, but its presence may represent a hidden threat, ready to arise when honeybees are weakened by biotic and abiotic stressors. To shed light on the Serratia pathogen, this research aims at studying Serratia's development dynamics in the honeybee body and its interactions with the co-occurring fungal pathogen Vairimorpha ceranae. Firstly, the degree of pathogenicity and the ability to permeate the gut epithelial barrier of three Serratia strains, isolated from honeybees and belonging to different species (S. marcescens, Serratia liquefaciens, and Serratia nematodiphila), were assessed by artificial inoculation of newborn honeybees with different Serratia doses (104, 106, and 108 cells/mL). The absolute abundance of Serratia in the gut and in the hemocoel was assessed in qPCR with primers targeting the luxS gene. Moreover, the absolute abundance of Serratia was assessed in the gut of honeybees infected with V. ceranae at different development stages and supplied with beneficial microorganisms and fumagillin. Our results showed that all tested Serratia strains could pass through the gut epithelial barrier and proliferate in the hemocoel, with S. marcescens being the most pathogenic. Moreover, under cage conditions, Serratia better proliferates when a V. ceranae infection is co-occurring, with a positive and significant correlation. Finally, fumagillin and some of the tested beneficial microorganisms could control both Serratia and Vairimorpha development. Our findings suggest a correlation between the two pathogens under laboratory conditions, a co-occurring infection that should be taken into consideration by researches when testing antimicrobial compounds active against V. ceranae, and the related honeybees survival rate. Moreover, our findings suggest a positive control of Serratia by the environmental microorganism Apilactobacillus kunkeei in a in vivo model, confirming the potential of this specie as beneficial bacteria for honeybees.

Assessment of three antibiotic combination regimens against Gram-negative bacteria causing neonatal sepsis in low- and middle-income countries.

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

Integrated Experimental and Theoretical Investigation of Copper Active Site Properties of a Lytic Polysaccharide Monooxygenase from Serratia marcescens.

In this paper, we employed a multidisciplinary approach, combining experimental techniques and density functional theory (DFT) calculations to elucidate key features of the copper coordination environment of the bacterial lytic polysaccharide monooxygenase (LPMO) from Serratia marcescens (SmAA10). The structure of the holo-enzyme was successfully obtained by X-ray crystallography. We then determined the copper(II) binding affinity using competing ligands and observed that the affinity of the histidine brace ligands for copper is significantly higher than previously described. UV-vis, advanced electron paramagnetic resonance (EPR), and X-ray absorption spectroscopy (XAS) techniques, including high-energy resolution fluorescence detected (HERFD) XAS, were further used to gain insight into the copper environment in both the Cu(II) and Cu(I) redox states. The experimental data were successfully rationalized by DFT models, offering valuable information on the electronic structure and coordination geometry of the copper center. Finally, the Cu(II)/Cu(I) redox potential was determined using two different methods at ca. 350 mV vs NHE and rationalized by DFT calculations. This integrated approach not only advances our knowledge of the active site properties of SmAA10 but also establishes a robust framework for future studies of similar enzymatic systems.

Enhancing spinach (Spinacia oleracea L.) resilience in pesticide-contaminated soil: Role of pesticide-tolerant Ciceribacter azotifigens and Serratia marcescens in root architecture, leaf gas exchange attributes and antioxidant response restoration.

This study unveils the detoxification potential of insecticide-tolerant plant beneficial bacteria (PBB), i.e., Ciceribacter azotifigens SF1 and Serratia marcescens SRB1, in spinach treated with fipronil (FIP), profenofos (PF) and chlorantraniliprole (CLP) insecticides. Increasing insecticide doses (25-400 µg kg-1 soil) significantly curtailed germination attributes and growth of spinach cultivated at both bench-scale and in greenhouse experiments. Profenofos at 400 µg kg-1 exhibited maximum inhibitory effects and reduced germination by 55%; root and shoot length by 78% and 81%, respectively; dry matter accumulation in roots and shoots by 79% and 62%, respectively; leaf number by 87% and leaf area by 56%. Insecticide application caused morphological distortion in root tips/surfaces, increased levels of oxidative stress, and cell death in spinach. Application of insecticide-tolerant SF1 and SRB1 strains relieved insecticide pressure resulting in overall improvement in growth and physiology of spinach grown under insecticide stress. Ciceribacter azotifigens improved germination rate (10%); root biomass (53%); shoot biomass (25%); leaf area (10%); Chl-a (45%), Chl-b (36%) and carotenoid (48%) contents of spinach at 25 µg CLP kg-1 soil. PBB inoculation reinvigorated the stressed spinach and modulated the synthesis of phytochemicals, proline, malondialdehyde (MDA), superoxide anions (O2•-), and hydrogen peroxide (H2O2). Scanning electron microscopy (SEM) revealed recovery in root tip morphology and stomatal openings on abaxial leaf surfaces of PBB-inoculated spinach grown with insecticides. Ciceribacter azotifigens inoculation significantly increased intrinsic water use efficiency, transpiration rate, vapor pressure deficit, intracellular CO2 concentration, photosynthetic rate, and stomatal conductance in spinach exposed to 25 µg FIP kg-1. Also, C. azotifigens and S. marcescens modulated the antioxidant defense systems of insecticide-treated spinach. Bacterial strains were strongly colonized to root surfaces of insecticide-stressed spinach seedlings as revealed under SEM. The identification of insecticide-tolerant PBBs such as C. azotifigens and S. marcescens hold the potential for alleviating abiotic stress to spinach, thereby fostering enhanced and safe production within polluted agroecosystems.

Immobilized Dipeptidase in Manganese Ion-Loaded Polyethylenimine-Induced Calcium Phosphate Nanocrystals for Carnosine Synthesis.

Carnosine is a natural bioactive dipeptide with important physiological functions widely used in food and medicine. Dipeptidase (PepD) from Serratia marcescens can catalyze the reverse hydrolytic reaction of ß-alanine with l-histidine to synthesize carnosine in the presence of Mn2+. However, it remains challenging to practice carnosine biosynthesis due to the low activity and high cost of the enzyme. Therefore, the development of biocatalysts with high activity and stability is of significance for carnosine synthesis. Here, we proposed to chelate Mn2+ to polyethylenimine (PEI) that induced rapid formation of calcium phosphate nanocrystals (CaP), and Mn-PEI@CaP was used for PepD immobilization via electrostatic interaction. Mn-PEI@CaP as the carrier enhanced the stability of the immobilized enzyme. Moreover, Mn2+ loaded in the carrier acted as an in situ activator of the immobilized PepD for facilitating the biocatalytic process of carnosine synthesis. The as-prepared immobilized enzyme (PepD-Mn-PEI@CaP) kept similar activity with free PepD plus Mn2+ (activity recovery, 102.5%), while exhibiting elevated thermal stability and pH tolerance. Moreover, it exhibited about two times faster carnosine synthesis than the free PepD system. PepD-Mn-PEI@CaP retained 86.8% of the original activity after eight cycles of batch catalysis without the addition of free Mn2+ ions during multiple cycles. This work provides a new strategy for the co-immobilization of PepD and Mn2+, which greatly improves the operability of the biocatalysis and demonstrates the potential of the immobilized PepD system for efficient carnosine synthesis.

Evaluation of photocatalysis inactivation in indoor air purification of pathogenic microbes by using the different nanomaterials based on TiO2 nanomaterials.

The photocatalytic technology for indoor air disinfection has been broadly studied in the last decade. Selecting proper photocatalysts with high disinfection efficiency remains to be a challenge. By doping with the incorporation of metals, the bandgap can be narrowed while avoiding the recombination of photogenerated charge. Three photocatalysts (Ag-TiO2, MnO2-TiO2, and MnS2-TiO2) were tested in photocatalytic sterilization process. The results revealed that Ag-TiO2 had the best antibacterial performance. Within 20 min, the concentration of Serratia marcescens (the tested bacteria) decreased log number of ln 4.04 under 640 w/m2 light intensity with 1000 µg/mL of Ag-TiO2. During the process of inactivating bacteria, the cell membranes of bacterial was destructed and thus decreasing the activity of enzymes and releasing the cell contents, due to the generation of reactive oxygen species (O2•- and •OH) and thermal effect. Spectral regulation has the greatest impact on the sterilization efficiency of MnO2-TiO2, which reduces the probability of photocatalytic materials being excited.

Pink colored breast milk! Serratia marcescens infection, series of 4 cases.

BACKGROUND: Pink coloration of breast milk is uncommon and it´s associated with colonization by Serratia marcescens, which is most frequently isolated in intensive care settings. Misinterpretation of the pink coloration may lead to premature cessation of breastfeeding. The objective is to present four cases of pink discoloration. METHODS: Two retrospective and two prospective cases of pink discoloration in breast milk are described, which were reported to the lead author. RESULTS: Four healthy mother-infant pairs with documented pink discoloration are presented. S. marcescens was isolated from breast milk samples. All four infants were asymptomatic and underwent enterobacteria cultures. The mothers received outpatient antibiotic treatment, and two infants received treatment as well. Subsequent cultures yielded negative results, and the pink discoloration ceased. All mothers successfully resumed breastfeeding. CONCLUSIONS: There are very few reported cases of pink breast milk in the global literature. Colonization by S. marcescens is not an indication for discontinuation of breastfeeding.

INTRODUCCIÓN: La coloración rosa de la leche materna es poco frecuente y está asociada a colonización por Serratia marcescens. Se aísla con mayor frecuencia en entornos de cuidados intensivos. La desinformación por la coloración rosa puede conducir a una terminación prematura de la lactancia. El objetivo es presentar cuatro casos de coloración rosa de la leche materna. MÉTODOS: Se describen dos casos retrospectivos y dos prospectivos de presentación de leche materna de color rosa. Los casos fueron reportados a la autora principal. RESULTADOS: Se presentan cuatro binomios sanos con reporte de coloración rosa. Se aisló S. marcescens en una muestra de leche materna. Los cuatro lactantes eran asintomáticos y tuvieron cultivos para la enterobacteria. Las madres fueron tratadas con antibiótico ambulatorio. Dos lactantes recibieron tratamiento. Todos los cultivos posteriores fueron negativos y la coloración rosa cesó. Todos reanudaron la lactancia materna de forma exitosa. CONCLUSIONES: Existen muy pocos casos de leche de color rosa reportados en la literatura mundial. La colonización por S. marcescens no es una indicación de suspensión de la lactancia.

Assessment of the Entomopathogenic Potential of Fungal and Bacterial Isolates from Fall Armyworm Cadavers Against Spodoptera frugiperda Caterpillars and the Adult Boll Weevil, Anthonomus grandis.

Increased attention is being focused on the biological control of agricultural pests using microorganisms, owing to their potential as a viable substitute for chemical control methods. Insect cadavers constitute a potential source of entomopathogenic microorganisms. We tested whether bacteria and fungi isolated from Spodoptera frugiperda (JE Smith) cadavers could affect its survival, development, egg-laying pattern, and hatchability, as well as induce mortality in Anthonomus grandis Boheman adults. We isolated the bacteria Enterobacter hormaechei and Serratia marcescens and the fungi Scopulariopsis sp. and Aspergillus nomiae from fall armyworm cadavers and the pest insects were subjected to an artificial diet enriched with bacteria cells or fungal spores to be tested, in the case of S. frugiperda, and only fungal spores in the case of A. grandis. Enterobacter hormaechei and A. nomiae were pathogenic to S. frugiperda, affecting the survival of adults and pupae. The fungus Scopulariopsis sp. does not affect the survival of S. frugiperda caterpillars and pupae; however, due to late action, moths and eggs may be affected. Aspergillus nomiae also increased mortality of A. grandis adults, as well as the development of S. frugiperda in the early stages of exposure to the diet, as indicated by the vertical spore transfer to offspring and low hatchability. Enterobacter hormaechei and A. nomiae are potential biocontrol agents for these pests, and warrant further investigation from a toxicological point of view and subsequently in field tests involving formulations that could improve agricultural sustainability practices.

Purification, functional characterization and enhanced production of serratiopeptidase from Serratia marcescens MES-4: An endophyte isolated from Morus rubra.

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

Impact of Whole Genome Sequencing to investigate transmission of Serratia marcescens in Neonatal Intensive Care Unit.

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