Growth and survival of Serratia marcescens under aerobic and anaerobic conditions in the presence of materials from blood bags

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.

Quality assessment of platelet concentrates prepared by platelet-rich plasma, buffy-coat, and apheresis methods in a tertiary care hospital in South India: A cross-sectional study

INTRODUCTION

In blood banking and transfusion medicine, it is of paramount importance to improve transfusion safety and provide a higher quality of product to maximize the therapeutic outcomes and minimize the risk of developing transfusion-associated complications for patients receiving a blood transfusion.

MATERIALS AND METHODS

This was a cross-sectional study conducted at the department of transfusion medicine in a tertiary care hospital of South India from February 2019 to December 2020. The primary objective of the study was to assess the quality of platelet concentrates (PC) prepared by platelet-rich plasma (PRP), buffy-coat (BC), and apheresis method. A total of 760 PCs were subjected to quality assessment, among which 124 were PRP-PC, 176 were BC-PC, and 460 were single donor platelet (SDP).

RESULTS

The total percentage of platelets meeting all the six quality control parameters in PRP, BC and SDP was 78.23%, 81.81%, and 89.96%, respectively. Apheresis PCs showed a significantly higher platelet concentration per µL on comparison with whole-blood-derived platelets. BC-PCs were found to be better than PRP-PC with regard to lower white blood cell (WBC) contamination (P < 0.05) and red blood cell (RBC) contamination (P < 0.01). No statistically significant difference was found with regard to platelet yield, volume, swirling, and pH.

CONCLUSION

Ex vivo quality of PCs prepared by BC-PC, PRP-PC, and apheresis-PC fulfilled the desired quality control parameters. BC-PC was better than PRP-PC in terms of lesser WBC and RBC contamination and comparable in terms of volume, platelet yield, swirling, and pH. Apheresis PCs showed a higher platelet concentration per microliter on comparison with whole-blood-derived platelets; hence in a blood center where facilities for collection of apheresis product are available, SDPs should be the choice of platelet transfusion.

Single-channel characterization of the chitooligosaccharide transporter chitoporin (SmChiP) from the opportunistic pathogen Serratia marcescens

Serratia marcescens is an opportunistic pathogen that can utilize chitin as a carbon source, through its ability to produce chitin-degrading enzymes to digest chitin and membrane transporters to transport the degradation products (chitooligosaccharides) into the cells. Further characterization of these proteins is important to understand details of chitin metabolism. Here, we investigate the properties and function of the S. marcescens chitoporin, namely SmChiP, a chitooligosaccharide transporter. We show that SmChiP is a monomeric porin that forms a stable channel in artificial phospholipid membranes, with an average single-channel conductance of 0.5 ± 0.02 nS in 1 M KCl electrolyte. Additionally, we demonstrated that SmChiP allowed the passage of small molecules with a size exclusion limit of <300 Da and exhibited substrate specificity toward chitooligosaccharides, both in membrane and detergent-solubilized forms. We found that SmChiP interacted strongly with chitopentaose (K_d = 23 ± 2.0 μM) and chitohexaose (K_d = 17 ± 0.6 μM) but did not recognize nonchitose oligosaccharides (maltohexaose and cellohexaose). Given that S. marcescens can use chitin as a primary energy source, SmChiP may serve as a target for further development of nutrient-based antimicrobial therapies directed against multidrug antibiotic-resistant S. marcescens infections.

Assessment on the Fermentation Quality and Bacterial Community of Mixed Silage of Faba Bean With Forage Wheat or Oat

Faba bean (Vicia faba L.), although a kind of high-quality and high-yield forage, could hardly achieve a great quality of silage because of its high buffering capacity. Mixed silage of faba bean with forage wheat (Triticum aestivum L.) or oat (Avena sativa L.) at different ratios could improve the fermentation quality and bacterial community. Compared with 100% faba bean silage (BS), mixed silage improved the fermentation quality, not only increased lactic acid production and reduced pH, but reduced the production of propionic acid and ammonia nitrogen. The chemical compositions of faba bean with forage wheat (BT) mixed silage were better than that of faba bean with oat (BO) mixed silage, and that of 3:7, 5:5 (fresh matter basis) mixing ratios were better than 1:9. However, the fermentation quality of BO mixed silage was better than that of BT, and that of 3:7 mixed silage (BO30) was the best overall. Analysis of the bacterial community showed that mixed silage increased the relative abundance of lactic acid bacteria after ensiling, and the relatively higher abundance of Lactobacillus showed the inhibitory effects on the proliferation of Serratia and Hafnia_Obesumbacterium, so that it alleviated their negative effects on silage and stabilized the fermentation quality. This present study exhibited that mixed silage of faba bean with forage wheat or oat not only had significant effects on chemical compositions and fermentation quality of materials but modified bacterial community so that improved the fermentation quality effectively. The mixed silage of 30% faba bean with 70% oat (BO30) is recommended in the faba bean mixed silage.

Nuclease activity: an exploitable biomarker in bacterial infections

INTRODUCTION

In the increasingly challenging field of clinical microbiology, diagnosis is a cornerstone whose accuracy and timing are crucial for the successful management, therapy, and outcome of infectious diseases. Currently employed biomarkers of infectious diseases define the scope and limitations of diagnostic techniques. As such, expanding the biomarker catalog is crucial to address unmet needs and bring about novel diagnostic functionalities and applications.

AREAS COVERED

This review describes the extracellular nucleases of 15 relevant bacterial pathogens and discusses the potential use of nuclease activity as a diagnostic biomarker. Articles were searched for in PubMed using terms: "nuclease", "bacteria", "nuclease activity" or "biomarker". For overview sections, original and review articles between 2000 and 2019 were searched for using terms: "infections", "diagnosis", "bacterial", "burden", "challenges". Informative articles were selected.

EXPERT OPINION

Using the catalytic activity of nucleases offers new possibilities compared to established biomarkers. Nucleic acid activatable reporters in combination with different transduction platforms and delivery methods can be used to detect disease-associated nuclease activity patterns in vitro and in vivo for prognostic and diagnostic applications. Even when these patterns are not obvious or of unknown etiology, screening platforms could be used to identify new disease reporters.

Global population structure of the Serratia marcescens complex and identification of hospital-adapted lineages in the complex

Serratia marcescens is an important nosocomial pathogen causing various opportunistic infections, such as urinary tract infections, bacteremia and sometimes even hospital outbreaks. The recent emergence and spread of multidrug-resistant (MDR) strains further pose serious threats to global public health. This bacterium is also ubiquitously found in natural environments, but the genomic differences between clinical and environmental isolates are not clear, including those between S. marcescens and its close relatives. In this study, we performed a large-scale genome analysis of S. marcescens and closely related species (referred to as the 'S. marcescens complex'), including more than 200 clinical and environmental strains newly sequenced here. Our analysis revealed their phylogenetic relationships and complex global population structure, comprising 14 clades, which were defined based on whole-genome average nucleotide identity. Clades 10, 11, 12 and 13 corresponded to S. nematodiphila, S. marcescens sensu stricto, S. ureilytica and S. surfactantfaciens, respectively. Several clades exhibited distinct genome sizes and GC contents and a negative correlation of these genomic parameters was observed in each clade, which was associated with the acquisition of mobile genetic elements (MGEs), but different types of MGEs, plasmids or prophages (and other integrative elements), were found to contribute to the generation of these genomic variations. Importantly, clades 1 and 2 mostly comprised clinical or hospital environment isolates and accumulated a wide range of antimicrobial resistance genes, including various extended-spectrum β-lactamase and carbapenemase genes, and fluoroquinolone target site mutations, leading to a high proportion of MDR strains. This finding suggests that clades 1 and 2 represent hospital-adapted lineages in the S. marcescens complex although their potential virulence is currently unknown. These data provide an important genomic basis for reconsidering the classification of this group of bacteria and reveal novel insights into their evolution, biology and differential importance in clinical settings.

Cavitated pulmonary nodules in a female patient with breast cancer: Keep in mind Serratia marcescens' infections

Serratia species are gram-negative bacteria, which could be isolated from soil, water, plants, animals and air. They are responsible for a heterogeneous spectrum of diseases, affecting the central nervous system, the urinary tract, the respiratory tract and the bloodstream.

Pulmonary involvement is rare and typically occurs in immunocompromised patients; radiological appearances include haemorrhagic bronchopneumonia, even with the development of pulmonary abscesses and cavitated parenchymal lesions, or diffuse alveolar damage. Concerning pulmonary cavities, the differential diagnosis should include metastatic lung nodules, rheumatoid arthritis, Langerhans cell histiocytosis, mycotic infections and septic emboli. The knowledge of these radiological features, in association with clinical history and laboratory findings, is mandatory to make the correct diagnosis, suggesting the right treatment and the adequate follow-up. We described a challenging case of a Serratia marcescens’ pulmonary infection, which occurred in a patient with breast cancer: clinical features and main imaging findings have been discussed – in order to help clinicians and radiologists in the management of the disease.

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Breast cancer may involve lung parenchyma with metastatic cavitated nodules.

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Serratia can cause cavitated pulmonary nodules.

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Differential diagnosis of cavitated pulmonary nodules includes infectious and non-infectious diseases.

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Serratia commonly causes haemorrhagic bronchopneumonia or diffuse alveolar damage.

The contest of microbial pigeon neighbors: Interspecies competition between Serratia marcescens and the human pathogen Cryptococcus neoformans

In nature, microorganisms often exhibit competitive behavior for nutrients and limited space, allowing them to alter the virulence determinants of pathogens. The human pathogenic yeast Cryptococcus neoformans can be found organized in biofilms, a complex community composed of an extracellular matrix which confers protection against predation. The aim of this study was to evaluate and characterize antagonistic interactions between two cohabiting microorganisms: C. neoformans and the bacteria Serratia marcescens. The interaction of S. marcescens with C. neoformans expressed a negative effect on biofilm formation, polysaccharide capsule, production of urease, and melanization of the yeast. These findings evidence that competition in mixed communities can result in dominance by one species, with direct impact on the physiological modulation of virulence determinants. Such an approach is key for understating the response of communities to the presence of competitors and, ultimately, rationally designing communities to prevent and treat certain diseases.

Stored Canine Whole Blood Units: What is the Real Risk of Bacterial Contamination?

Background

Bacterial contamination of whole blood (WB) units can result in transfusion‐transmitted infection, but the extent of the risk has not been established and may be underestimated in veterinary medicine.

Objectives

To detect, quantify, and identify bacterial microorganisms in 49 canine WB units during their shelf life.

Animals

Forty‐nine healthy adult dogs.

Methods

Forty‐nine WB units were included in the study. Immediately after collection, 8 sterile samples from the tube segment line of each unit were aseptically collected and tested for bacterial contamination on days 0, 1, 7, 14, 21, 28, 35, and 42 of storage. A qPCR assay was performed on days 0, 21, and 35 to identify and quantify any bacterial DNA.

Results

On bacterial culture, 47/49 blood units were negative at all time points tested, 1 unit was positive for Enterococcus spp. on days 0 and 1, and 1 was positive for Escherichia coli on day 35. On qPCR assay, 26 of 49 blood units were positive on at least 1 time point and the bacterial loads of the sequences detected (Propionobacterium spp., Corynebacterium spp., Caulobacter spp., Pseudomonas spp., Enterococcus spp., Serratia spp., and Leucobacter spp.) were <80 genome equivalents (GE)/μL.

Conclusions and Clinical Importance

Most of the organisms detected were common bacteria, not usually implicated in septic transfusion reactions. The very low number of GE detected constitutes an acceptable risk of bacterial contamination, indicating that WB units have a good sanitary shelf life during commercial storage.

Recent independent emergence of multiple multidrug-resistant Serratia marcescens clones within the United Kingdom and Ireland

Serratia marcescens, a member of the Enterobacteriaceae family, is a Gram-negative bacterium responsible for a wide range of nosocomial infections. The emergence of multidrug-resistant strains is an increasing danger to public health. To design effective means to control the dissemination of S. marcescens, an in-depth analysis of the population structure and variation is required. Utilizing whole-genome sequencing, we characterized the population structure and variation, as well as the antimicrobial resistance determinants, of a systematic collection of antimicrobial-resistant S. marcescens associated with bloodstream infections in hospitals across the United Kingdom and Ireland between 2001 and 2011. Our results show that S. marcescens is a diverse species with a high level of genomic variation. However, the collection was largely composed of a limited number of clones that emerged from this diverse background within the past few decades. We identified potential recent transmissions of these clones, within and between hospitals, and showed that they have acquired antimicrobial resistance determinants for different beta-lactams, ciprofloxacin, and tetracyclines on multiple occasions. The expansion of these multidrug-resistant clones suggests that the treatment of S. marcescens infections will become increasingly difficult in the future.

Carbon-Starvation Induces Cross-Resistance to Thermal, Acid, and Oxidative Stress in Serratia marcescens

The broad host-range pathogen Serratia marcescens survives in diverse host and non-host environments, often enduring conditions in which the concentration of essential nutrients is growth-limiting. In such environments, carbon and energy source starvation (carbon-starvation) is one of the most common forms of stress encountered by S. marcescens. Related members of the family Enterobacteriaceae are known to undergo substantial changes in gene expression and physiology in response to the specific stress of carbon-starvation, enabling non-spore-forming cells to survive periods of prolonged starvation and exposure to other forms of stress (i.e., starvation-induced cross-resistance). To determine if carbon-starvation also results in elevated levels of cross-resistance in S. marcescens, both log-phase and carbon-starved cultures, depleted of glucose before the onset of high cell-density stationary-phase, were grown in minimal media at either 30 °C or 37 °C and were then challenged for resistance to high temperature (50 °C), low pH (pH 2.8), and oxidative stress (15 mM H₂O₂). In general, carbon-starved cells exhibited a higher level of resistance to thermal stress, acid stress, and oxidative stress compared to log-phase cells. The extent of carbon-starvation-induced cross-resistance was dependent on incubation temperature and on the particular strain of S. marcescens. In addition, strain- and temperature-dependent variations in long-term starvation survival were also observed. The enhanced stress-resistance of starved S. marcescens cells could be an important factor in their survival and persistence in many non-host environments and within certain host microenvironments where the availability of carbon sources is suboptimal for growth.

Draft Genome Sequence of a Clinical Isolate of Serratia marcescens, Strain AH0650_Sm1

Serratia marcescens strain AH0650_Sm1 is a clinical multidrug-resistant isolate from Australia. Here, we report its annotated draft genome comprising 20 contigs. We identified chromosomal antimicrobial resistance genes including a tet(41) variant, an aac(6′)-Ic variant, ampC, a metallo-beta-lactamase, and several putative multidrug efflux pumps, as well as a novel prophage.

Measurement of predation and biofilm formation under different ambient oxygen conditions using a simple gasbag-based system

Bdellovibrio bacteriovorus and Micavibrio aeruginosavorus are Gram-negative bacteria characterized by predatory behavior. The aim of this study was to evaluate the ability of the predators to prey in different oxygen environments. When placed on an orbital shaker, a positive association between the rate of aeration and predation was observed. To further examine the effects of elevated ambient oxygen levels on predation, a simple gasbag system was developed. Using the system, we were able to conduct experiments at ambient oxygen levels of 3% to 86%. When placed in gasbags and inflated with air, 50% O2, and 100% O2, positive predation was seen on both planktonic and biofilm-grown prey cells. However, in low-oxygen environments, predatory bacteria were able to attack only prey cells grown as biofilms. To further evaluate the gasbag system, biofilm development of Gram-positive and Gram-negative microorganisms was also measured. Although the gasbag system was found to be suitable for culturing bacteria that require a low-oxygen environment, it was not capable of supporting, with its current configuration, the growth of obligate anaerobes in liquid or agar medium.

Events at blood collection area due to nonconforming blood bags and plateletpheresis kits: need for timely corrective and preventive actions

BACKGROUND

Good blood banking practice requires that every effort should be made to detect any deviation or defect in blood bank products and to identify any potential risk to blood donor or recipient(s). We report the findings of an exercise that provide an insight into why feedback from the user side is crucial.

STUDY DESIGN AND METHODS

Various events involving blood bags and plateletpheresis kits and the corresponding appropriate actions instituted for remedial measures were recorded. These scattered events were recorded for 6 months following the use of a new batch of improved blood bags with add-on features. Several events related to plateletpheresis kits from three different manufacturers were also recorded for 1 year.

RESULTS

The affected blood bags were utilized with no untoward incident. The complaint was closed following satisfactory response from the blood bag manufacturing company that acted in a timely manner in addressing the root causes of the problems. However, corrective and preventive actions (CAPA) could not be implemented for plateletpheresis kits. The rate of undesirable events was higher with plateletpheresis kits as compared with whole blood bags (1.75% vs. 0.06%).

CONCLUSION

As defects or deviations that trigger the need for CAPA can stem from numerous sources, it is important to clearly identify and document the problems and level of risk so that appropriate investigations can be instituted and remedial actions can be taken in a timely manner. This study demonstrates the usefulness of a quality initiative to collate and analyze blood product faults in conjunction with blood product manufacturers.

Serratia marcescens strains implicated in adverse transfusion reactions form biofilms in platelet concentrates and demonstrate reduced detection by automated culture

BACKGROUND AND OBJECTIVES

Serratia marcescens is a gram-negative bacterium that has been implicated in adverse transfusion reactions associated with contaminated platelet concentrates. The aim of this study was to investigate whether the ability of S. marcescens to form surface-attached aggregates (biofilms) could account for contaminated platelet units being missed during screening by the BacT/ALERT automated culture system.

MATERIALS AND METHODS

Seven S. marcescens strains, including biofilm-positive and biofilm-negative control strains and five isolates recovered from contaminated platelet concentrates, were grown in enriched Luria-Bertani medium and in platelets. Biofilm formation was examined by staining assay, dislodging experiments and scanning electron microscopy. Clinical strains were also analysed for their ability to evade detection by the BacT/ALERT system.

RESULTS

All strains exhibited similar growth in medium and platelets. While only the biofilm-positive control strain formed biofilms in medium, this strain and three clinical isolates associated with transfusion reactions formed biofilms in platelet concentrates. The other two clinical strains, which had been captured during platelet screening by BacT/ALERT, failed to form biofilms in platelets. Biofilm-forming clinical isolates were approximately three times (P<0·05) more likely to be missed by BacT/ALERT screening than biofilm-negative strains.

CONCLUSION

S. marcescens strains associated with transfusion reactions form biofilms under platelet storage conditions, and initial biofilm formation correlates with missed detection of contaminated platelet concentrates by the BacT/ALERT system.

Outbreak of Serratia marcescens bloodstream and central nervous system infections after interventional pain management procedures

OBJECTIVES

To determine the cause of an outbreak of Serratia marcescens infections in patients after interventional pain management procedures at an outpatient pain clinic.

METHODS

We conducted a case-control study and collected clinical and environmental samples.

RESULTS

We identified 5 culture-confirmed case-patients and 2 presumptive case-patients who had no bacteria recovered from cultures. The 7 case-patients were compared with 28 controls who underwent procedures at the same clinic but did not develop symptoms of infection. All confirmed case-patients had S. marcescens bloodstream infections; 2 had concurrent S. marcescens central nervous system infections. Case-patients were more likely than controls to have procedures that used contrast solution or entered the epidural or intervertebral disc space (P< or =0.01 for each). All S. marcescens clinical isolates were indistinguishable by pulsed-field gel electrophoresis. We did not isolate S. marcescens from medications or environmental samples; however, S. marcescens was shown to survive and grow in contrast solution that was experimentally contaminated for up to 30 days. Single-dose vials of medication, including contrast solution, were used for multiple procedures; multiple medications were accessed with a common needle and syringe.

DISCUSSION

The findings of this investigation suggest contamination of a common medication, likely contrast solution, as the source of the outbreak. Practices, such as reusing single-dose medication vials and using a common needle and syringe to access multiple medications, could have led to contamination and propagation of S. marcescens and should be avoided in interventional pain management procedures.

Bacterial contamination of blood components

Blood for transfusion is a potential source of infection by a variety of known and unknown transmissible agents. Over the last 20 years, astounding reductions in the risk of viral infection via allogeneic blood have been achieved. As a result of this success, bacterial contamination of blood products has emerged as the greatest residual source of transfusion-transmitted disease. This paper summarizes the current status of detection, prevention, and elimination of bacteria in blood products for transfusion.

Transfusion-related sepsis due to Serratia liquefaciens in the United States

BACKGROUND

Severe, often fatal, transfusion reactions due to bacterial contamination of blood components continue to occur. Serratia liquefaciens, an unusual human pathogen, is a recently recognized potential cause of transfusion-related sepsis.

CASE REPORTS

Five episodes of transfusion-related sepsis and endotoxic shock due to S. liquefaciens were reported to the CDC from July 1992 through January 1999. One episode has been described. The remaining four, all fatal, are described here: three associated with RBC transfusion and one associated with transfusion of platelets. In each instance, the source of contamination could not be found. The implicated units tended to be older (mean RBC age 28 days), and visual discoloration was noted in each RBC unit, although usually in retrospect.

CONCLUSION

S. liquefaciens is an increasingly recognized cause of transfusion-related sepsis and is associated with a high mortality rate. S. liquefaciens can contaminate both RBCs and platelets, but the mechanism(s) of contamination remain unknown. Increased attention to pretransfusion visual inspection may avert the transfusion of some S. liquefaciens-contaminated RBC units. However, more sensitive rapid diagnostic tests are needed to further reduce the risk of transfusion-related sepsis and endotoxic shock.

[Quality assurance of bacterial incidents associated with blood transfusion]

Transfusion associated bacterial sepsis, TABS, may be caused by-donor bacteremia,-bacteria from the donors skin,-bacteria brought by one of the persons handling the donation or the blood product, from collection and components preparation to the actual transfusion,-or bacteria introduced by a defect in one of the disposables used. Quality Assurance relies on the Good Transfusion Practices of the French Blood Agency all along the transfusion chain from the donor to the recipient. Active involvement of personnel, standardisation and controls as well as improvement of technics particularly as regarding donor selection, skin disinfection technics and collection are required. The ultimate control is hemovigilance with proper identification and investigation of all cases of TABS even with mild symptoms. Centralisation of data in the Haemovigilance scheme is a further step toward a better understanding and improvement of blood products bacterial security.

Adherence of Serratia marcescens, Serratia liquefaciens, Pseudomonas aeruginosa and Staphylococcus epidermidis to blood transfusion bags (CPD-SAGMAN sets)

The adherence of 4 isolates of Serratia marcescens, 1 isolate of Serratia liquefaciens, 1 of Pseudomonas aeruginosa, and 2 of Staphylococcus epidermidis to blood transfusion sets (CPD-SAGMAN) consisting of bags and connecting tubing was tested. All strains adhered well to the connecting tubes (polyvinyl chloride) from the transfusion sets from 3 manufacturers. Three isolates from a Swedish outbreak of septicaemia associated with contaminated blood bags showed greater adherence than an isolate from a urinary tract infection. There was no significant adherence of S. marcescens to the blood bags. In general, there were no significant differences in the adherence of a given isolate to the plastics from different manufacturers. Appropriate hygienic procedures for the production of transfusion sets appear to be of greater importance than differences in the plastic material as regards the incidence of transfusion-related bacteremia.