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.

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.

Association Between Serratia marcescens Contamination and Hygiene Compliance in Orthokeratology.

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

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

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

Spread and evolution of blaKPC-plasmid between Serratia marcescens and Klebsiella pneumoniae.

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

Outbreak investigation of Serratia marcescens bloodstream infection in an obstetric ward for high-risk pregnant women.

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

Genomic characterization of two carbapenem-resistant Serratia marcescens isolates causing bacteremia: Emergence of KPC-2-encoding IncR plasmids.

The occurrence and transmission of carbapenemase-producing-Enterobacterales (CPE) on a global scale has become a major issue. Clinical reports are rarely providing information on the genomic and plasmid features of carbapenem-resistant Serratia marcescens. Our objective was to investigate the resistance and transmission dynamics of two carbapenem-resistant S. marcescens that are resistant to carbapenem and have caused bacteremia in China. Blood specimens were taken from two individuals with bacteremia. Multiplex PCR was employed to identify genes that code for carbapenemase. Antimicrobial susceptibility tests and plasmid analysis were conducted on S. marcescens isolates SM768 and SM4145. The genome of SM768 and SM4145 were completely sequenced using NovaSeq 6000-PE150 and PacBio RS II platforms. Antimicrobial resistance genes (ARGs) were predicted using the ResFinder tool. S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) and southern blotting were employed to analyze plasmids. Two S. marcescens that produced KPC-2 were identified from bloodstream infections. The antimicrobial susceptibility testing demonstrated that both of the isolates had a resistance to various antibiotics. The whole-genome sequence (WGS) and plasmid analysis revealed the presence of bla KPC-2-bearing IncR plasmids and multiple plasmid-borne antimicrobial resistance genes in the isolates. Our comparative plasmid analysis suggested that the two IncR plasmids identified in this study could be derived from a common ancestor. Our findings revealed the emergence of bla KPC-2-bearing IncR plasmid in China, which could be a hindrance to the transmission of KPC-2-producing S. marcescens in clinical settings.

Epidemiology of Serratia marcescens infections in NICU of a Teaching and Research Hospital in Northern Italy.

BACKGROUND: Serratia marcescens (Sm) is a known cause of infection and colonization in neonates receiving intensive care. The aim of this study was to identify the risk factors for colonization and infection with Sm in Neonatal Intensive Care Unit (NICU) of a tertiary care Hospital. METHODS: A case-control study was conducted from January to December 2011 in neonates admitted to the NICU. Cases are patients with a microbiologically confirmed infection or colonization, controls were randomly chosen among patients admitted to the same NICU. RESULTS: Globally, 39 acquired infections or colonizations were identified. Among factors related to pregnancy, only premature delivery was independently associated to the risk of infection; as well as mechanical ventilation and catheterization for parenteral nutrition, considering indwelling devices. Prolonged administration with antibiotics were also related to the risk of infection. Among Sm strains which have been tested to antibiotics, all have been resistant to amoxicillin/clavulanic acid and to colistin. CONCLUSIONS: This study confirms the association between Sm infection or colonization and low gestational age. Invasive medical devices and medications, strictly necessary in care-support of preterm neonates, are likely related to Sm infection too. Preventive control strategies are expected to be effective in the control of Sm spread in NICUs.

Successful control of Serratia marcescens outbreak in a neonatal unit of a tertiary-care hospital in Spain.

OBJECTIVE: Serratia marcescens is a Gram-negative bacterium that is found in hospital environments and commonly associated with outbreaks in neonatal units. One S. marcescens isolate was detected from a bloodstream culture from a neonate in our hospital that was followed by an outbreak. The aim of this study was to describe the molecular epidemiology of a S. marcescens outbreak in the neonatal unit. METHODS: In order to investigate the outbreak, weekly surveillance rectal swabs were submitted for culture from all patients admitted in this unit from August to September 2018. Environmental samples were obtained from potential sources in September 2018. Typing of isolates was performed by pulsed field gel electrophoresis (PFGE). In addition, we studied the in vitro activity of chlorhexidine against S. marcescens. RESULTS: During this period, 146 infants were hospitalised in our neonatal unit, of which 16 patients had a S. marcescens-positive sample. A total of 36 environmental surveillance samples were collected, and one sample from a stethoscope from an incubator of a colonized baby was positive for S. marcescens. All the 18 isolates, including the isolate from the stethoscope, belonged to a single PFGE cluster. We found that very low concentrations of chlorhexidine, even with application times close to 0 achieved significant reductions in the amount of S. marcescens. CONCLUSION: A unique clone of S. marcescens caused this outbreak, including isolates from patients and from one stethoscope. The outbreak was controlled with the early implementation of specific control measures.

Evaluation of CHROMagar™-Serratia agar, a new chromogenic medium for the detection and isolation of Serratia marcescens.

A comparative analysis of the performance of the new selective chromogenic CHROMagar™-Serratia culture medium for detection and isolation of Serratia marcescens was undertaken. A total of 134 clinical isolates (95 S. marcescens with and without carbapenemase production and 39 non-S. marcescens isolates) and 96 epidemiological samples (46 rectal swabs and 50 from environmental surfaces) were studied. Diagnostic values when compared with CHROMagar™-Orientation medium were 96.8% sensitivity, 100% specificity, 100% positive predictive value and 88.5% negative predictive value. In conclusion, CHROMagar™-Serratia shows an excellent ability for differentiation of S. marcescens among clinical isolates and in environmental samples.

Vertical Transmission at the Pathogen-Symbiont Interface: Serratia symbiotica and Aphids.

Many insects possess beneficial bacterial symbionts that occupy specialized host cells and are maternally transmitted. As a consequence of their host-restricted lifestyle, these symbionts often possess reduced genomes and cannot be cultured outside hosts, limiting their study. The bacterial species Serratia symbiotica was originally characterized as noncultured strains that live as mutualistic symbionts of aphids and are vertically transmitted through transovarial endocytosis within the mother's body. More recently, culturable strains of S. symbiotica were discovered that retain a larger set of ancestral Serratia genes, are gut pathogens in aphid hosts, and are principally transmitted via a fecal-oral route. We find that these culturable strains, when injected into pea aphids, replicate in the hemolymph and are pathogenic. Unexpectedly, they are also capable of maternal transmission via transovarial endocytosis: using green fluorescent protein (GFP)-tagged strains, we observe that pathogenic S. symbiotica strains, but not Escherichia coli, are endocytosed into early embryos. Furthermore, pathogenic S. symbiotica strains are compartmentalized into specialized aphid cells in a fashion similar to that of mutualistic S. symbiotica strains during later stages of embryonic development. However, infected embryos do not appear to develop properly, and offspring infected by a transovarial route are not observed. Thus, cultured pathogenic strains of S. symbiotica have the latent capacity to transition to lifestyles as mutualistic symbionts of aphid hosts, but persistent vertical transmission is blocked by their pathogenicity. To transition into stably inherited symbionts, culturable S. symbiotica strains may need to adapt to regulate their titer, limit their pathogenicity, and/or provide benefits to aphids that outweigh their cost.IMPORTANCE Insects have evolved various mechanisms to reliably transmit their beneficial bacterial symbionts to the next generation. Sap-sucking insects, including aphids, transmit symbionts by endocytosis of the symbiont into cells of the early embryo within the mother's body. Experimental studies of this process are hampered by the inability to culture or genetically manipulate host-restricted, symbiotic bacteria. Serratia symbiotica is a bacterial species that includes strains ranging from obligate, heritable symbionts to gut pathogens. We demonstrate that culturable S. symbiotica strains, which are aphid gut pathogens, can be maternally transmitted. Cultured S. symbiotica therefore possesses a latent capacity for evolving a host-restricted lifestyle and can be used to understand the transition from pathogenicity to beneficial symbiosis.

The Rcs Stress Response System Regulator GumB Modulates Serratia marcescens-Induced Inflammation and Bacterial Proliferation in a Rabbit Keratitis Model and Cytotoxicity In Vitro.

In this study, we tested the hypothesis that the conserved bacterial IgaA-family protein, GumB, mediates microbial pathogenesis associated with Serratia marcescens ocular infections through regulation of the Rcs stress response system. The role of the Rcs system and bacterial stress response systems for microbial keratitis is not known, and the role of IgaA proteins in mammalian pathogenesis models has only been tested with partial-function allele variants of Salmonella. Here, we observed that an Rcs-activated gumB mutant had a >50-fold reduction in proliferation compared to the wild type within rabbit corneas at 48 h and demonstrated a notable reduction in inflammation based on inflammatory signs, including the absence of hypopyons, and proinflammatory markers measured at the RNA and protein levels. The gumB mutant phenotypes could be complemented by wild-type gumB on a plasmid. We observed that bacteria with an inactivated Rcs stress response system induced high levels of ocular inflammation and restored corneal virulence to the gumB mutant. The high virulence of the ΔrcsB mutant was dependent upon the ShlA cytolysin transporter ShlB. Similar results were found for testing the cytotoxic effects of wild-type and mutant bacteria on a human corneal epithelial cell line in vitro. Together, these data indicate that GumB regulates virulence factor production through the Rcs system, and this overall stress response system is a key mediator of a bacterium's ability to induce vision-threatening keratitis.

Repurposing of antidiabetics as Serratia marcescens virulence inhibitors.

BACKGROUND: Serratia marcescens becomes an apparent nosocomial pathogen and causes a variety of infections. S. marcescens possess various virulence factors that are regulated by intercellular communication system quorum sensing (QS). Targeting bacterial virulence is a proposed strategy to overcome bacterial resistance. Sitagliptin anti-QS activity has been demonstrated previously and we aimed in this study to investigate the effects of antidiabetic drugs vildagliptin and metformin compared to sitagliptin on S. marcescens pathogenesis. METHODS: We assessed the effects of tested drugs in subinhibitory concentrations phenotypically on the virulence factors and genotypically on the virulence encoding genes' expressions. The protection of tested drugs on S. marcescens pathogenesis was performed in vivo. Molecular docking study has been conducted to evaluate the interference capabilities of tested drugs to the SmaR QS receptor. RESULTS: Vildagliptin reduced the expression of virulence encoding genes but did not show in vitro or in vivo anti-virulence activities. Metformin reduced the expression of virulence encoding genes and inhibited bacterial virulence in vitro but did not show in vivo protection. Sitagliptin significantly inhibited virulence factors in vitro, reduced the expression of virulence factors and protected mice from S. marcescens. Docking study revealed that sitagliptin is more active than metformin and fully binds to SmaR receptor, whereas vildagliptin had single interaction to SmaR. CONCLUSION: The downregulation of virulence genes was not enough to show anti-virulence activities. Hindering of QS receptors may play a crucial role in diminishing bacterial virulence.

Serratia Chorioamnionitis and Culture Proven Sepsis in a Preterm Neonate: A Case Report and Review of the Literature.

BACKGROUND: Serratia marcescens is a well-known cause of nosocomial infectious outbreaks in the neonatal intensive care unit, with a high mortality rate in the vulnerable preterm population. However, it is not typically associated with neonatal sepsis secondary to intrapartum vertical transmission. We present the case of a preterm male born at 25 weeks and 4 days of gestation in Okinawa, Japan with culture-proven S. marcescens chorioamnionitis and sepsis, as well as a review of the previously published literature. METHODS: We conducted a literature search utilizing MeSH indexing with the headings [chorioamnionitis], [Serratia], and [infant, newborn] limited to "humans" with a publication date range between 1950 and 2020. RESULTS: All reported cases of preterm S. marcescens chorioamnionitis occurred in coastal locations. The majority of cases resulted in spontaneous abortion, and we found no published reports of confirmed S. marcescens chorioamnionitis in conjunction with viable preterm delivery and positive neonatal cultures. In the case presented herein, S. marcescens chorioamnionitis with associated neonatal sepsis was confirmed by positive placental and blood cultures. Bacterial clearance was achieved following an antibiotic course consisting of 5 days of gentamicin and 14 days of meropenem therapy. CONCLUSIONS: S. marcescens is an uncommon cause of chorioamnionitis that can have devastating neonatal consequences, especially in the at-risk preterm population.

Identifying the Molecular Targets of an Anti-pathogenic Hydroalcoholic Extract of Punica granatum Peel Against Multidrug-resistant Serratia marcescens.

BACKGROUND: Antibiotic-resistant members of the family Enterobacteriaceae are among the serious threats to human health globally. This study reports the anti-pathogenic activity of Punica granatum peel extract (PGPE) against a multi-drug resistant, beta-lactamase producing member of this family i.e. Serratia marcescens. OBJECTIVE: This study aimed at assessing the anti-pathogenic activity of PGPE against the gramnegative bacterial pathogen S. marcescens and identifying the molecular targets of this extract in the test bacterium. METHODS: Effect of PGPE on S. marcescens growth and quorum sensing (QS)-regulated pigment production was assessed through broth dilution assay. In vivo anti-infective and prophylactic activity of PGPE was assessed employing the nematode worm Caenorhabditis elegans as a model host. Differential gene expression in PGPE-exposed S. marcescens was studied through a whole transcriptome approach. RESULTS: PGPE was able to modulate QS-regulated pigment production in S. marcescens without exerting any heavy growth-inhibitory effect at concentrations as low as ≥2.5 µg/mL. It could attenuate the virulence of the test bacterium towards the worm host by 22-42% (p≤0.01) at even lower concentrations (≥0.5 µg/mL). PGPE also exerted a post-extract effect on S. marcescens. This extract was found to offer prophylactic benefit too, to the host worm, as PGPE-pre-fed worms scored better (34-51%; p≤0.001) survival in face of subsequent bacterial attack. Differential gene expression analysis revealed that PGPE affected the expression of a total of 66 genes in S. marcescens by ≥1.5 fold. CONCLUSION: The anti-virulence effect of PGPE against S. marcescens is multifaceted, affecting stress-response machinery, efflux activity, iron homeostasis, and cellular energetics of this bacterium notably. Among the major molecular targets identified in this study are LPS export transporter permease (LptF), t-RNA pseudouridine synthase (TruB), etc.

SMRT sequencing of the full-length transcriptome of Odontotermes formosanus (Shiraki) under Serratia marcescens treatment.

Odontotermes formosanus (Shiraki) is an important pest in the world. Serratia marcescens have a high lethal effect on O. formosanus, but the specific insecticidal mechanisms of S. marcescens on O. formosanus are unclear, and the immune responses of O. formosanus to S. marcescens have not been clarified. At present, genetic database resources of O. formosanus are extremely scarce. Therefore, using O. formosanus workers infected by S. marcescens and the control as experimental materials, a full-length transcriptome was sequenced using the PacBio Sequel sequencing platform. A total of 10,364 isoforms were obtained as the final transcriptome. The unigenes were further annotated with the Nr, Swiss-Prot, EuKaryotic Orthologous Groups (KOG), Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) Ortholog public databases. In a comparison between the control group and a Serratia marcescens-infected group, a total of 259 differentially expressed genes (DEGs) were identified, including 132 upregulated and 127 downregulated genes. Pathway enrichment analysis indicated that the expression of the mitogen-activated protein kinase (MAPK) pathway, oxidative stress genes and the AMP-activated protein kinase (AMPK) pathway in O. formosanus may be associated with S. marcescens treatment. This research intensively studied O. formosanus at the high-throughput full-length transcriptome level, laying a foundation for further development of molecular markers and mining of target genes in this species and thereby promoting the biological control of O. formosanus. Furthermore, these results will be helpful to clarify the action mechanisms of S. marcescens on O. formosanus, and also explore the relationship between O. formosanus and S. marcescens. In addition, this study will identify the immune response of O. formosanus to S. marcescens, which will provide a theoretical foundation for the development of new immunosuppressants for O. formosanus.

Lytic lesion of skull: a rare presentation of chronic granulomatous disease.

An 18-month-old boy presented with lytic lesion of skull and recurrent abscesses with Serratia marcescens The extensive work up revealed a gene mutation confirming the diagnosis of chronic granulomatous disease (CGD). This case scenario underscores the importance of exploring the possibility of immunodeficiency if there is a history of recurrent abscesses with atypical organism. The case also demonstrates that CGD can present as lytic lesion of skull.

Late-onset Subconjunctival Abscess Secondary to Serratia marcescens Associated With Unexposed Ahmed Glaucoma Valve Implant.

PURPOSE: The purpose of this study was to report a rare case of late-onset subconjunctival abscess associated with an unexposed Ahmed glaucoma valve implant secondary to Serratia marcescens, a rare conjunctival pathogen. METHODS: Case description including clinical imaging and literature review of glaucoma drainage device (GDD)-related infections. CASE PRESENTATION: A 73-year-old man presented with blurring of vision, redness, and pain on his right eye 2 months after Ahmed glaucoma valve implantation for advanced postpenetrating-keratoplasty glaucoma. The patient was nonsmoker, had fairly controlled type 2 diabetes mellitus on insulin, and had undergone multiple eye surgeries on the right eye. On ocular examination, the conjunctiva was injected with fairly delineated yellowish-white subconjunctival material in the superotemporal quadrant with no associated tube exposure or leak, and the anterior chamber was quiet. The patient was assessed with Ahmed glaucoma valve infection with subconjunctival abscess and was treated by Ahmed glaucoma valve explant with directed systemic and topical antimicrobial therapy. The culture and sensitivity results revealed S. marcescens sensitive to ciprofloxacin, ceftazidime, gentamicin, and amikacin. Despite the virulence of the pathogen, the eye was saved. CONCLUSIONS: Ahmed glaucoma valve infection with subconjunctival abscess secondary to S. marcescens is rare. GDD-related infections should be suspected in patients presenting with blurring of vision, pain, and redness even in the absence of tube exposure. Early diagnosis and treatment with culture-guided antimicrobial therapy combined with GDD explant is fundamental in optimizing the visual outcome.

Synergistic effects of Cinnamomum cassia L. essential oil in combination with polymyxin B against carbapenemase-producing Klebsiella pneumoniae and Serratia marcescens.

Multidrug resistance prompts the search for new sources of antibiotics with new targets at bacteria cell. To investigate the antibacterial activity of Cinnamomum cassia L. essential oil (CCeo) alone and in combination with antibiotics against carbapenemase-producing Klebsiella pneumoniae and Serratia marcescens. The antimicrobial susceptibility of the strains was determined by Vitek® 2 and confirmed by MALDI-TOF/TOF. The antibacterial activity of CCeo and its synergism with antibiotics was determined using agar disk diffusion, broth microdilution, time-kill, and checkboard methods. The integrity of the bacterial cell membrane in S. marcescens was monitored by protein leakage assay. CCeo exhibited inhibitory effects with MIC = 281.25 µg.mL-1. The association between CCeo and polymyxin B showed a decrease in terms of viable cell counts on survival curves over time after a 4 hour-treatment with a FIC index value of 0.006. Protein leakage was observed with increasing concentrations for CCeo and CCeo + polymyxin B treatments. CCeo showed antibacterial activity against the studied strains. When associated with polymyxin B, a synergistic effect was able to inhibit bacterial growth rapidly and consistently, making it a potential candidate for the development of an alternative treatment and drug delivery system for carbapenemase-producing strains.