Brote de Serratia marcescens producido por clorhexidina acuosa al 2% contaminada

Nosocomial outbreak caused by Serratia marcescens in a neonatology intensive care unit in a regional hospital. Analysis and improvement proposals

OBJECTIVES

Serratia marcescens (SM) may cause nosocomial outbreaks in Neonatal Intensive Care Units (NICU). We describe an outbreak of SM in a NICU and propose additional prevention and control recommendations.

METHODS

Between March 2019 and January 2020, samples were taken from patients in the NICU (rectal, pharyngeal, axillary and other locations) and from 15 taps and their sinks. Control measures were implemented including thorough cleaning of incubators, health education to staff and neonates'relatives, and use of single-dose containers. PFGE was performed in 19 isolates from patients and in 5 environmental samples.

RESULTS

From the first case in March 2019 to the detection of the outbreak, a month elapsed. Finally, 20 patients were infected and 5 colonized. 80% of infected neonates had conjunctivitis, 25% bacteremia, 15% pneumonia, 5% wound infection, and 5% urinary tract infection. Six neonates had two foci of infection. Among the 19 isolates studied, 18 presented the same pulsotype and only one of the isolates from the sinkhole showed a clonal relationship with those of the outbreak. Initial measures established were ineffective to control de outbreak and were implemented with exhaustive cleaning, use of individual eye drops, environmental sampling and changing sinks.

CONCLUSION

This outbreak presented a high number of neonates affected due to its late detection and torpid evolution. The microorganisms isolated from the neonates were related to an environmental isolate. Additional prevention and control measures are proposed, including routine weekly microbiological sampling.

Disinfectants and antiseptics: mechanisms of action and resistance

Chemical biocides are used for the prevention and control of infection in health care, targeted home hygiene or controlling microbial contamination for various industrial processes including but not limited to food, water and petroleum. However, their use has substantially increased since the implementation of programmes to control outbreaks of methicillin-resistant Staphylococcus aureus, Clostridioides difficile and severe acute respiratory syndrome coronavirus 2. Biocides interact with multiple targets on the bacterial cells. The number of targets affected and the severity of damage will result in an irreversible bactericidal effect or a reversible bacteriostatic one. Most biocides primarily target the cytoplasmic membrane and enzymes, although the specific bactericidal mechanisms vary among different biocide chemistries. Inappropriate usage or low concentrations of a biocide may act as a stressor while not killing bacterial pathogens, potentially leading to antimicrobial resistance. Biocides can also promote the transfer of antimicrobial resistance genes. In this Review, we explore our current understanding of the mechanisms of action of biocides, the bacterial resistance mechanisms encompassing both intrinsic and acquired resistance and the influence of bacterial biofilms on resistance. We also consider the impact of bacteria that survive biocide exposure in environmental and clinical contexts.

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

Introduction

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

Methods

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

Results

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

Conclusion

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

Antimicrobial activities of polyhexamethylene biguanide against biofilm-producing Prototheca bovis causing bovine mastitis

Prototheca spp. is a frequent cause of bovine mastitis and is highly resistant to commonly used disinfectants. This study aimed to: (1) evaluate the antimicrobial activity of polyhexamethylene biguanide (PHMB) against mastitis-causing Prototheca spp., and (2) evaluate the biofilm production ability of Prototheca spp. A total of 85 Prototheca bovis and 2 Prototheca blaschkeae isolates from bovine mastitis cases were submitted to biofilm production assays and antimicrobial susceptibility tests against PHMB and disinfectants commonly used in dairy herds (chlorhexidine digluconate, povidone-iodine, sodium dichloroisocyanurate, and sodium hypochlorite). The minimal inhibitory concentration (MIC) and minimal algicidal concentration (MAC) were determined by microdilution assays. We observed that PHMB (MIC₉₀: ≥2 µg/mL and MAC₉₀: ≥4 µg/mL) and chlorhexidine gluconate (MIC₉₀ and MAC₉₀: ≥2 µg/mL) presented the highest antimicrobial activity against P. bovis isolates, followed by sodium dichloroisocyanurate (MIC₉₀ and MAC₉₀: ≥1,400 µg/mL), sodium hypochlorite (MIC₉₀ and MAC₉₀: ≥2,800 µg/mL), and povidone-iodine (MIC₉₀ and MAC₉₀: ≥3,200 µg/mL). Concerning P. blaschkeae isolates, PHMB (MIC and MAC ≥1 µg/mL) and chlorhexidine gluconate (MIC and MAC ≥1 µg/mL) were the disinfectants that presented the lowest concentration values required to inhibit the isolates. Regarding biofilms formation, 63.5% (n = 54/85) of the P. bovis isolates were classified as strong, 28.3% (n = 24/85) moderate, and 8.2% (n = 7/85) weak biofilm producers. In contrast, the P. blaschkeae isolates were classified as weak and moderate biofilm producers. These findings suggest that PHMB has the potential to be used for teat and milking-equipment disinfection for the prevention of mastitis-causing Prototheca spp. in dairy herds.

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.

Healthcare-associated infections caused by chlorhexidine-tolerant Serratia marcescens carrying a promiscuous IncHI2 multi-drug resistance plasmid in a veterinary hospital

The bacterium Serratia marcescens can cause opportunistic infections in humans and in animals. In veterinary settings, the diversity, reservoirs and modes of transmission of this pathogen are poorly understood. The phenotypes and genotypes of Serratia spp. isolated from dogs, cats, horses, a bird and a rabbit examined at an Australian veterinary hospital between 2008 and 2019 were characterised. The isolates were identified as S. marcescens (n = 15) or S. ureilytica (n = 3) and were placed into four distinct phylogenetic groups. Nine quasi-clonal isolates associated with post-surgical complications in different patients displayed high levels of resistance to the antimicrobials fluoroquinolones, cephalosporins, aminoglycosides, and to the disinfectant chlorhexidine. A Serratia sp. with a similar resistance profile was also isolated from chlorhexidine solutions used across the Hospital, suggesting that these infections had a nosocomial origin. A genomic island encoding a homolog of the Pseudomonas MexCD-OprJ biocide efflux system was detected in the chlorhexidine-tolerant Serratia. The nine multi-drug resistant Serratia isolates also possessed a Ser-83-Ile mutation in GyrA conferring fluoroquinolone resistance, and carried a large IncHI2 conjugative plasmid encoding antimicrobial and heavy metal resistances. This replicon was highly similar to a plasmid previously detected in a strain of Enterobacter hormaechei recovered from the Hospital environment. IncHI2 plasmids are commonly found in Enterobacteriaceae, but are rarely present in Serratia spp., suggesting that this plasmid was acquired from another organism. A chlorhexidine-tolerant Serratia isolate which lacked the IncHI2 plasmid was used in mating experiments to demonstrate the transfer of multi-drug resistance from a E. hormaechei donor. This study illustrates the importance of environmental surveillance of biocide-resistance in veterinary hospitals.

A Genome-Scale Antibiotic Screen in Serratia marcescens Identifies YdgH as a Conserved Modifier of Cephalosporin and Detergent Susceptibility

Serratia marcescens, a member of the order Enterobacterales, is adept at colonizing health care environments and is an important cause of invasive infections. Antibiotic resistance is a daunting problem in S. marcescens because, in addition to plasmid-mediated mechanisms, most isolates have considerable intrinsic resistance to multiple antibiotic classes. To discover endogenous modifiers of antibiotic susceptibility in S. marcescens, a high-density transposon insertion library was subjected to sub-MICs of two cephalosporins, cefoxitin, and cefepime, as well as the fluoroquinolone ciprofloxacin. Comparisons of transposon insertion abundance before and after antibiotic exposure identified hundreds of potential modifiers of susceptibility to these agents. Using single-gene deletions, we validated several candidate modifiers of cefoxitin susceptibility and chose ydgH, a gene of unknown function, for further characterization. In addition to cefoxitin, deletion of ydgH in S. marcescens resulted in decreased susceptibility to multiple third-generation cephalosporins and, in contrast, to increased susceptibility to both cationic and anionic detergents. YdgH is highly conserved throughout the Enterobacterales, and we observed similar phenotypes in Escherichia coli O157:H7 and Enterobacter cloacae mutants. YdgH is predicted to localize to the periplasm, and we speculate that it may be involved there in cell envelope homeostasis. Collectively, our findings provide insight into chromosomal mediators of antibiotic resistance in S. marcescens and will serve as a resource for further investigations of this important pathogen.

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.

Defining chaperone-usher fimbriae repertoire in Serratia marcescens

Chaperone-usher (CU) fimbriae are surface organelles particularly prevalent among the Enterobacteriaceae. Mainly associated to their adhesive properties, CU fimbriae play key roles in biofilm formation and host cell interactions. Little is known about the fimbriome composition of the opportunistic human pathogen Serratia marcescens. Here, by using a search based on consensus fimbrial usher protein (FUP) sequences, we identified 421 FUPs across 39 S. marcescens genomes. Further analysis of the FUP-containing loci allowed us to classify them into 20 conserved CU operons, 6 of which form the S. marcescens core CU fimbriome. A new systematic nomenclature is proposed according to FUP sequence phylogeny. We also established an in vivo transcriptional assay comparing CU promoter expression between an environmental and a clinical isolate of S. marcescens, which revealed that promoters from 3 core CU operons (referred as fgov, fpo, and fps) are predominantly expressed in the two strains and might represent key core adhesion appendages contributing to S. marcescens pathogenesis.

Clinical study of an outbreak of postoperative mediastinitis caused by Serratia marcescens in adult cardiac surgery

OBJECTIVES

Nosocomial infection caused by Serratia marcescens after cardiac surgery is rare but causes high rates of morbidity and mortality. Knowledge about postoperative mediastinitis due to S. marcescens is limited. The purpose of this work was to study the clinical presentation, management and outcome of an outbreak of postoperative sternal infection due to S. marcescens.

METHODS

During a 7-week period, a total of 54 patients underwent open heart procedures in our hospital. A postoperative wound infection caused by S. marcescens was diagnosed in 10 patients. We performed a clinical study to investigate patient characteristics and outcomes as well as the possible source of the infection.

RESULTS

The mean age of the infected patients was 74.5 ± 10 years. Mediastinitis was present in 6 cases, superficial wound infection in 3 and isolated bacteraemia in 1. Purulent exudate through the sternal incision was observed in all infected cases except in 1 patient, who presented only with bacteraemia. Serratia marcescens was isolated from the samples taken from all infected wounds. The mean time elapsed between the operation and the isolation S. marcescens was 5.9 ± 2.4 days. Response to treatment was favourable in all cases except 1, who died. Contamination of the aqueous chlorhexidine solution used to prepare the patients' skin with S. marcescens was reported. Microbiological studies demonstrated that S. marcescens strains isolated from patients and from the aqueous chlorhexidine solution belonged to the same clone.

CONCLUSIONS

The use of an aqueous chlorhexidine solution contaminated with S. marcescens caused an outbreak of postoperative sternal wound infections. The time elapsed between wound contamination and signs of infection was brief, but the systemic inflammatory response and tissue necrosis were limited. Alcohol-based solutions are recommended for the prevention of surgical site infections.

Sink traps as the source of transmission of OXA-48-producing Serratia marcescens in an intensive care unit

BACKGROUND

Carbapenemase-producing Enterobacteriaceae (CPE) outbreaks are mostly attributed to patient-to-patient transmission via healthcare workers.

OBJECTIVE

We describe successful containment of a prolonged OXA-48-producing S. marcescens outbreak after recognizing the sink traps as the source of transmission.

METHODS

The Sheba Medical Center intensive care unit (ICU), contains 16 single-bed, semi-closed rooms. Active CPE surveillance includes twice-weekly rectal screening of all patients. A case was defined as a patient detected with OXA-48 CPE >72 hours after admission. A root-cause analysis was used to investigate the outbreak. All samples were inoculated on chrom-agar CRE, and carbapenemase genes were detected using commercial molecular Xpert-Carba-R. Environmental and patient S. marcescens isolates were characterized using PFGE.

RESULTS

From January 2016 to May 2017, 32 OXA-48 CPE cases were detected, and 81% of these were S. marcescens. A single clone was the cause of all but the first 2 cases. The common factor in all cases was the use of relatively large amounts of tap water. The outbreak clone was detected in 2 sink outlets and 16 sink traps. In addition to routine strict infection control measures, measures taken to contain the outbreak included (1) various sink decontamination efforts, which eliminated the bacteria from the sink drains only temporarily and (2) educational intervention that engaged the ICU team and lead to high adherence to 'sink-contamination prevention guidelines.' No additional cases were detected for 12 months.

CONCLUSIONS

Despite persistence of the outbreak clones in the environmental reservoir for 1 year, the outbreak was rapidly and successfully contained. Addressing sink traps as hidden reservoirs played a major role in the intervention.