Serratia marcescens transmission in a pediatric intensive care unit: a multifactorial occurrence

Implementation of a PCR-based strategy to control an outbreak by Serratia marcescens in a Neonatal Intensive Care Unit

OBJECTIVES

To evaluate the clinical and epidemiological impact of a new molecular surveillance strategy based on qPCR to control an outbreak by Serratia marcescens in a Neonatal Intensive Care Unit (NICU).

METHODS

We design a specific qPCR for the detection of S. marcescens in rectal swabs of patients admitted to a NICU. We divided the surveillance study into two periods: (a) the pre-PCR, from the outbreak declaration to the qPCR introduction, and (b) the PCR period, from the introduction of the qPCR until the outbreak was solved. In all cases, S. marcescens isolates were recovered and their clonal relationship was analysed by PFGE. Control measures were implemented during the outbreak. Finally, the number of bloodstream infections (BSI) was investigated in order to evaluate the clinical impact of this molecular strategy.

RESULTS

Nineteen patients colonized/infected by S. marcescens were detected in the pre-PCR period (October 2020-April 2021). On the contrary, after the PCR implementation, 16 new patients were detected. The PFGE revealed 24 different pulsotypes belonging to 7 different clonal groups, that were not overlapping at the same time. Regarding the clinical impact, 18 months after the qPCR implementation, no more outbreaks by S. marcescens have been declared in the NICU of our hospital, and only 1 episode of BSI has occurred, compared with 11 BSI episodes declared previously to the outbreak control.

CONCLUSIONS

The implementation of this qPCR strategy has proved to be a useful tool to control the nosocomial spread of S. marcescens in the NICU.

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.

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 loop-mediated isothermal amplification assays for rapid detection of blaKPC producing Serratia spp. in clinical specimens: A prospective diagnostic accuracy study

The prevalence of carbapenem-resistant Serratia spp. is increasing owing to the propagation of β lactamase Klebsiella pneumoniae carbapenemase (blaKPC) and it has become one of the major global health concerns. As effective therapies for such resistant pathogens are limited, there is a great need for the rapid and sensitive characterization of the pathogen. In the present study, a loop-mediated isothermal amplification (LAMP) method for the rapid detection of Serratia spp. with blaKPC in pure cultures and clinical specimens was developed. A calcein indicator and real-time turbidity recording system were used to assess the LAMP reaction. The LAMP assay was compared with conventional PCR and real-time PCR kits for the target pathogen. The desired amplification was achieved using selected primers and detection was possible using both the calcein indicator method and the real-time turbity recording system at 65˚C for 60 min. The sensitivity of the detection system for blaKPC-producing Serratia spp. reached a detection limit of 3.92 pg/µl DNA, which was 10 times more sensitive than conventional PCR. Specificity testing indicated that the primers were highly specific. Compared with conventional culture methods and real-time PCR, the LAMP assay was more sensitive, easier for laboratory staff to master and less influenced by the clinical specimen matrix. In conclusion, a LAMP assay for blaKPC-producing Serratia spp. that permitted rapid, sensitive and economical detection for this pathogen was successfully developed. Comparisons with alternative methods indicated that the LAMP assay was more feasible in a clinical setting.

An Outbreak of Serratia marcescens in a Moroccan Neonatal Intensive Care Unit

Serratia marcescens (S. marcescens) is an Enterobacteriaceae microorganism that is widespread in the environment, which may be the source of nosocomial infections, rare in the newborn but severe, and often in the form of outbreaks. The aim of our study is to report our experience, during an outbreak of S. marcescens, to show the severity of this germ, with review of the literature. Our study was retrospective, including 8 newborns with S. marcescens nosocomial infection, collected in the neonatal intensive care unit of Mohammed VI University Medical Hospital, during the epidemic period, over a period of 2 months (July and August 2016). The mean gestational age of the cases was 36 weeks of amenorrhea. Boys accounted for 75% of the cases. The average weight was 1853 grams. All the patients were initially placed under empiric antibiotic therapy based on ceftriaxone and gentamicin. The mean duration of nosocomial infection, diagnosed in all cases by blood cultures, was 7 days. The strains of S. marcescens were in 75% of the cases sensitive to the cephalosporins, intermediate sensitivity in 12.5% of cases and resistant in 12.5% of cases. The outcome was fatal in 62.5% of cases. S. marcescens nosocomial infections are often reported on epidemic series, and their eradication is not always easy.

Serratia marcescensBacteremia: Nosocomial Cluster Following Narcotic Diversion

OBJECTIVE

To describe the investigation and control of a cluster ofSerratia marcescensbacteremia in a 505-bed tertiary-care center.

METHODS

Cluster cases were defined as all patients withS. marcescensbacteremia between March 2 and April 7, 2014, who were found to have identical or related blood isolates determined by molecular typing with pulsed-field gel electrophoresis. Cases were compared using bivariate analysis with controls admitted at the same time and to the same service as the cases, in a 4:1 ratio.

RESULTS

In total, 6 patients developedS. marcescensbacteremia within 48 hours after admission within the above period. Of these, 5 patients had identicalSerratiaisolates determined by molecular typing, and were included in a case-control study. Exposure to the post-anesthesia care unit was a risk factor identified in bivariate analysis. Evidence of tampered opioid-containing syringes on several hospital units was discovered soon after the initial cluster case presented, and a full narcotic diversion investigation was conducted. A nurse working in the post-anesthesia care unit was identified as the employee responsible for the drug diversion and was epidemiologically linked to all 5 patients in the cluster. No further cases were identified once the implicated employee’s job was terminated.

CONCLUSION

Illicit drug use by healthcare workers remains an important mechanism for the development of bloodstream infections in hospitalized patients. Active mechanisms and systems should remain in place to prevent, detect, and control narcotic drug diversions and associated patient harm in the healthcare setting.

Infect Control Hosp Epidemiol2017;38:1027–1031

Serratia marcescens bacteraemia outbreak in haemodialysis patients with tunnelled catheters due to colonisation of antiseptic solution. Experience at 4 hospitals

INTRODUCTION

The application of antiseptic solution for handling tunnelled catheters is recommended in patients undergoing haemodialysis. These routine antiseptic procedures in handling catheters are crucial to avoid complications. We report an outbreak of Serratia marcescens (S. marcescens) bacteraemia in numerous haemodialysis units of the Community of Madrid.

MATERIAL AND METHODS

The first cases of bacteraemia due to S. marcescens were isolated in December 2014. The Preventive Medicine Services were informed of the detection of an atypical pathogen in several patients, suspecting a probable nosocomial outbreak. Information from 4 centres with similar S. marcescens bacteraemia was analysed.

RESULTS

Twenty-one cases of bacteraemia related to S. marcescens were identified. The mean age of affected patients was 72±10 years. The mean time on haemodialysis of affected patients was 33±13 months (range: 3-83 months), the median time of tunnelled catheter was 22±13 months. In 11 cases the clinical picture was similar, with hypotension and general malaise during the haemodialysis session. Fever was present in a further 7 cases. In 3 cases the presentation was asymptomatic and was detected by blood cultures. All patients had tunnelled catheters (12 patients with catheter in the right jugular vein, 5 in the left jugular, 2 in the right femoral artery and 2 in the left subclavian artery). Gentamicin intravenous doses (1mg/kg) with catheter lock solution with ciprofloxacin post-dialysis were administered for 3 weeks in 6 patients. In 12 patients the treatment was ceftazidime (2g IV) plus catheter lock solution with the same antibiotic, for 2 weeks. Four patients received oral ciprofloxacin for 2 weeks, in one case together with IV vancomycin. The patients were asymptomatic and without new episodes 48hours after the treatment. No major complications were observed. The teams informed the health authorities of the situation, which then reported the presence of batches of antiseptic (chlorhexidine 0.05 and 2%) colonised by S. marcescens. Given the routine application of this antiseptic in handling catheters at these units, this was considered the source of contagion and new cases were not observed after the removal of the batches.

CONCLUSIONS

The presence of bacteraemia due to unconventional germs should alert us to a potential outbreak. The application of a solution contaminated by S. marcescens in haemodialysis catheters was the source of bacteraemia. The intravenous antibiotic treatment and the catheter lock solution allowed an excellent survival of patients and catheters.

Rapid Eradication of a Cluster ofSerratia marcescensin a Neonatal Intensive Care Unit: Use of Epidemiologic Chromosome Profiling by Pulsed-Field Gel Electrophoresis

Objective:

To investigate a cluster of patients infected and colonized withSerratia marcescensin a neonatal intensive care unit (NICU).

Methods:

In June 2001, two neonates in the NICU had clinical infections withS. marcescensand one died. Infection control surveillance data for the NICU revealed that S.marcescenswas rarely isolated from clinical specimens. Surveillance and environmental cultures were performed and isolates were typed using pulsed-field gel electrophoresis. Staff and neonates were cohorted and a waterless, alcohol-based handwashing agent was introduced. A case-control study was performed.

Results:

From June 2 through August 20, 2001, 11 neonates withS. marcescensinfection and colonization were identified. The incidence ofS. marcescensinfections increased from 0.19 per 1,000 patient-days in 2000 to 0.52 per 1,000 patient-days in 2001 (P< .0001). In the first 3 weeks of the investigation, there were 2 sets of patients and sinks with indistinguishable strains; however, in subsequent weeks, all isolates were of unique strains, signifying no further transmission of the two initial predominant strains. Neonates withS. marcescenswere more likely to have a lower gestational age and birth weight. There was no association between cases and healthcare workers (HCWs).

Conclusions:

A cluster ofS. marcescenswas quickly terminated after the introduction of preventive measures including cohorting of infected and colonized neonates and HCWs, contact precautions, surveillance cultures, and a waterless, alcohol-based hand antiseptic. Chromosomal typing determined that strains with an indistinguishable pattern were no longer present in the unit after control measures were implemented.

Diversity of bacterial communities of fitness center surfaces in a U.S. metropolitan area

Public fitness centers and exercise facilities have been implicated as possible sources for transmitting community-acquired bacterial infections. However, the overall diversity of the bacterial community residing on the surfaces in these indoor environments is still unknown. In this study, we investigated the overall bacterial ecology of selected fitness centers in a metropolitan area (Memphis, TN, USA) utilizing culture-independent pyrosequencing of the 16S rRNA genes. Samples were collected from the skin-contact surfaces (e.g., exercise instruments, floor mats, handrails, etc.) within fitness centers. Taxonomical composition revealed the abundance of Firmicutes phyla, followed by Proteobacter and Actinobacteria, with a total of 17 bacterial families and 25 bacterial genera. Most of these bacterial genera are of human and environmental origin (including, air, dust, soil, and water). Additionally, we found the presence of some pathogenic or potential pathogenic bacterial genera including Salmonella, Staphylococcus, Klebsiella, and Micrococcus. Staphylococcus was found to be the most prevalent genus. Presence of viable forms of these pathogens elevates risk of exposure of any susceptible individuals. Several factors (including personal hygiene, surface cleaning and disinfection schedules of the facilities) may be the reasons for the rich bacterial diversity found in this study. The current finding underscores the need to increase public awareness on the importance of personal hygiene and sanitation for public gym users.

Application of quantitative microbial risk assessment for selection of microbial reduction targets for hard surface disinfectants

BACKGROUND

This quantitative microbial risk assessment (QMRA) included problem formulation for fomites and hazard identification for 7 microorganisms, including pathogenic Escherichia coli and E coli 0157:H7, Listeria monocytogenes, norovirus, Pseudomonas spp, Salmonella spp, and Staphylococcus aureus. The goal was to address a risk-based process for choosing the log10 reduction recommendations, in contrast to the current US Environmental Protection Agency requirements.

METHOD

For each microbe evaluated, the QMRA model included specific dose-response models, occurrence determination of aerobic bacteria and specific organisms on fomites, exposure assessment, risk characterization, and risk reduction. Risk estimates were determined for a simple scenario using a single touch of a contaminated surface and self-inoculation. A comparative analysis of log10 reductions, as suggested by the US Environmental Protection Agency, and the risks based on this QMRA approach was also undertaken.

RESULTS

The literature review and meta-analysis showed that aerobic bacteria were the most commonly studied on fomites, averaging 100 colony-forming units (CFU)/cm(2). Pseudomonas aeruginosa was found at a level of 3.3 × 10(-1) CFU/cm(2); methicillin-resistant S aureus (MRSA), at 6.4 × 10(-1) CFU/cm(2). Risk estimates per contact event ranged from a high of 10(-3) for norovirus to a low of 10(-9) for S aureus.

CONCLUSION

This QMRA analysis suggests that a reduction in bacterial numbers on a fomite by 99% (2 logs) most often will reduce the risk of infection from a single contact to less than 1 in 1 million.

Current and emergent strategies for disinfection of hospital environments

A significant number of hospital-acquired infections occur due to inefficient disinfection of hospital surfaces, instruments and rooms. The emergence and wide spread of multiresistant forms of several microorganisms has led to a situation where few compounds are able to inhibit or kill the infectious agents. Several strategies to disinfect both clinical equipment and the environment are available, often involving the use of antimicrobial chemicals. More recently, investigations into gas plasma, antimicrobial surfaces and vapour systems have gained interest as promising alternatives to conventional disinfectants. This review provides updated information on the current and emergent disinfection strategies for clinical environments.

Prolonged outbreak of Serratia marcescens in Tartu University Hospital: a case-control study

Background

The aim of our study was to investigate and control an outbreak and identify risk factors for colonization and infection with Serratia marcescens in two departments in Tartu University Hospital.

Methods

The retrospective case–control study was conducted from July 2005 to December 2006. Molecular typing by pulsed field gel electrophoresis was used to confirm the relatedness of Serratia marcescens strains. Samples from the environment and from the hands of personnel were cultured.

Results

The outbreak involved 210 patients, 61 (29%) developed an infection, among them 16 were invasive infections. Multivariate analysis identified gestational age, arterial catheter use and antibiotic treatment as independent risk factors for colonization and infection with Serratia marcescens. Molecular typing was performed on 83 Serratia marcescens strains, 81 of them were identical and 2 strains were different.

Conclusions

Given the occasionally severe consequences of Serratia marcescens in infants, early implementation of aggressive infection control measures involving patients and mothers as well as the personnel is of utmost importance.

Serratia infections: from military experiments to current practice

Serratia species, in particular Serratia marcescens, are significant human pathogens. S. marcescens has a long and interesting taxonomic, medical experimentation, military experimentation, and human clinical infection history. The organisms in this genus, particularly S. marcescens, were long thought to be nonpathogenic. Because S. marcescens was thought to be a nonpathogen and is usually red pigmented, the U.S. military conducted experiments that attempted to ascertain the spread of this organism released over large areas. In the process, members of both the public and the military were exposed to S. marcescens, and this was uncovered by the press in the 1970s, leading to U.S. congressional hearings. S. marcescens was found to be a certain human pathogen by the mid-1960s. S. marcescens and S. liquefaciens have been isolated as causative agents of numerous outbreaks and opportunistic infections, and the association of these organisms with point sources such as medical devices and various solutions given to hospitalized patients is striking. Serratia species appear to be common environmental organisms, and this helps to explain the large number of nosocomial infections due to these bacteria. Since many nosocomial infections are caused by multiply antibiotic-resistant strains of S. marcescens, this increases the danger to hospitalized patients, and hospital personnel should be vigilant in preventing nosocomial outbreaks due to this organism. S. marcescens, and probably other species in the genus, carries several antibiotic resistance determinants and is also capable of acquiring resistance genes. S. marcescens and S. liquefaciens are usually identified well in the clinical laboratory, but the other species are rare enough that laboratory technologists may not recognize them. 16S rRNA gene sequencing may enable better identification of some of the less common Serratia species.

Distribution of bacterial contamination in a teaching hospital in Tehran - a special focus on Staphylococcus aureus

There are documents that confirm the cycle of bacterial transmission between patients, staff, and the inanimate environment. The environment may have more effect on intensive care units (ICUs), because the patients who require intensive care have unstable clinical conditions and are more sensitive to infections. The aim of this study was to determine the prevalence of bacteria in air and inanimate surface in the ICUs and to compare the microbial levels to standard levels.Air and inanimate surface in the four ICUs of a teaching hospital underwent weekly surveillance by means of air sampler and swabs for a period of six-month. Total bacterial counts were evaluated onto trypticase soy agar and mannitol salt agar (MSA).A total of 725 samples [air (168) and inanimate surfaces (557)] were collected. The total mean ± SD CFU/m3 of airborne bacteria in all of the ICUs were 115.93 ± 48.04. The most common bacteria in air of the ICUs were Gram-positive cocci (84.2%). The total mean ± SD airborne of Staphylococcus aureus was 12.10±8.11 CFU/m3. The highest levels of S. aureus contamination were found in ventilators and bed ledges. More suitable disinfection of hospital environments and monthly rotation in utilization of the various disinfectant agents are needed for the prevention of airborne and inanimate transmission of S. aureus.

Outbreak of bloodstream infections because of Serratia marcescens in a pediatric department

BACKGROUND

Serratia marcescens can cause health care-associated infections. We herewith report the investigation and control of an outbreak of S marcescens bloodstream infections (BSI) in a general pediatric department.

METHODS

From April to May 2009, temporally related cases of S marcescens BSI occurred in a 40-bed general pediatric department of a tertiary care hospital. An outbreak investigation including case identification, review of medical records, environmental cultures, patients' surveillance cultures, personnel hand cultures, pulsed-field gel electrophoresis, and a case-control study were conducted. Controls were patients without S marcescens BSI but hospitalized in the department for at least 48 hours during the outbreak. Enhanced infection control measures were immediately implemented by the Infection Control Committee.

RESULTS

During the study period, 4 patients developed BSI because of a S marcescens strain demonstrating the same antimicrobial susceptibility pattern as well as the same molecular profile. Patients' surveillance cultures and personnel hand cultures were negative. In 1 case-patient, S marcescens grew from cultures of intravenous infusion systems. In the case-control study performed, there were no differences in demographics, intravenously administered medications, or place of hospital stay. Case patients had changes in vascular access significantly more frequently than controls. No S marcescens infections occurred in the department during the 18 months following implementation of the enhanced infection control measures.

CONCLUSION

Prompt recognition and strict adherence to infection control measures are of paramount importance in combating an outbreak of S marcescens bloodstream infection.

Health care-associated infection outbreak investigations by the Centers for Disease Control and Prevention, 1946-2005

Since 1946, Centers for Disease Control and Prevention (CDC) personnel have investigated outbreaks of infections and adverse events associated with delivery of health care. CDC Epidemic Intelligence Service officers have led onsite investigations of these outbreaks by systematically applying epidemiology, statistics, and laboratory science. During 1946-2005, CDC Epidemic Intelligence Service officers conducted 531 outbreak investigations in facilities across the United States and abroad. Initially, the majority of outbreaks involved gastrointestinal tract infections; however, in later years, bloodstream, respiratory tract, and surgical wound infections predominated. Among pathogens implicated in CDC outbreak investigations, Staphylococcus aureus, Enterococcus species, Enterobacteriaceae, nonfermentative Gram-negative bacteria, or yeasts predominated, but unusual organisms (e.g., the atypical mycobacteria) were often included. Outbreak types varied and often were linked to transfer of colonized patients or health care personnel between facilities (multihospital outbreaks), national distribution of contaminated products, use of invasive medical devices, or variances in practices and procedures in health care environments (e.g., intensive care units, water reservoirs, or hemodialysis units). Through partnerships with health care facilities and local and state health departments, outbreaks were terminated and lives saved. Data from investigations invariably contributed to CDC-generated guidelines for prevention and control of health care-associated infections.

Risk factors for healthcare-associated infection in pediatric intensive care units: a systematic review

A systematic review of observational studies on risk factors for healthcare-associated infection in pediatric Intensive Care Units (ICU) was carried out. Studies indexed in MEDLINE, LILACS, Cochrane, BDENF, CAPES databases published in English, French, Spanish or Portuguese between 1987 and 2006 were included and cross references added. Key words for search were 'cross infection' and 'Pediatric Intensive Care Units' with others sub-terms included. 11 studies were selected from 419 originally found: four studies had healthcare-associated infection as the main outcome without a specific site; three articles identified factors associated with lower respiratory tract infection (pneumonia or tracheitis); three articles were concerned with laboratory-confirmed bloodstream infection; and a single retrospective study analyzed urinary tract infection. The production of evidence on risk factors Paediatric ICU has not kept up the same pace of that on adult - there are few studies with adequate design and statistical analysis. The methodological diversity of the studies did not allow for a summarized measurement of risk factors.

Serratia marcescens infections and outbreaks in neonatal intensive care units

Serratia marcescens is an important cause of hospital-acquired infections, especially in neonatal intensive care units (NICUs). This review analyzes clinical signs, risk factors, biotyping and sources of infection in newborns exhibited by this bacteria as well as the therapy which is commonly used and management. This review examines the reported cases of outbreaks of S. marcescens in NICUs published in pubmed over the last 10 years (key words: Serratia marcescens infections, outbreaks, Neonatal intensive Care Units). This report highlights the different prevention and control strategies employed in order to eradicate Serratia outbreaks in NICUs, including all healthcare procedures such as hand washing, introduction of alcohol-based antiseptic gel, enhanced cleaning and disinfection of medical equipment and wards, use of single-patient medical instruments, cohorting of colonized and infected infants, periodic screening cultures, earliest discharge of the infants.

Distribution characteristics of airborne bacteria and fungi in the general hospitals of Korea

The objective of this study is to provide fundamental data related to size-based characteristics of bioaerosol distributed in the general hospital. Measurement sites are main lobby, ICU, surgical ward and biomedical laboratory and total five times were sampled with six-stage cascade impactor. Mean concentrations of airborne bacteria and fungi were the highest in main lobby as followed by an order of surgical ward, ICU and biomedical laboratory. The predominant genera of airborne bacteria identified in the general hospital were Staphylococcus spp. (50%), Micrococcus spp. (15-20%), Corynebacterium spp. (5-20%), and Bacillus spp. (5-15%). On the other hand, the predominant genera of airborne fungi identified in the general hospital were Cladosporium spp. (30%), Penicillium spp. (20-25%), Aspergillus spp. (15-20%), and Alternaria spp. (10-20%). The detection rate was generally highest on stage 5 (1.1-2.1 microm) for airborne bacteria and on stage 1 (>7.0 microm) for airborne fungi.

Outbreaks of Serratia marcescens in neonatal and pediatric intensive care units: clinical aspects, risk factors and management

The following recommendations are derived from a systematic analysis of 34 Serratia marcescens outbreaks described in 27 publications from neonatal and pediatric intensive care units (NICU, PICU), in which genotyping methods were used to confirm or exclude clonality. The clinical observation of two or more temporally related cases of nosocomial S. marcescens infection should raise the suspicion of an outbreak, particularly in the NICU or PICU setting. Since colonized or infected patients represent the most important reservoir for cross transmission, hygienic barrier precautions (contact isolation/cohortation, the use of gloves and gowns in addition to strictly performed hand disinfection, enhanced environmental disinfection) should immediately be implemented and staff education given. Well-planned sampling of potential environmental sources should only be performed when these supervised barrier precautions do not result in containment of the outbreak. The current strategy of empiric antibiotic treatment should be reevaluated by a medical microbiologist or an infectious disease specialist. Empiric treatment of colonized children should use combination therapy informed by in vitro susceptibility data; in this context the high propensity of S. marcescens to cause meningitis and intracerebral abscess formation should be considered. In vitro susceptibility patterns do not reliably prove or exclude the clonality of the outbreak isolate. Genotyping of the isolates by pulse-field gel electrophoresis or PCR-based methods should be performed, but any interventions to interrupt further nosocomial spread should be carried out without waiting for the results.

Are we aware how contaminated our mobile phones with nosocomial pathogens?

Background

The objective of this study was to determine the contamination rate of the healthcare workers' (HCWs') mobile phones and hands in operating room and ICU. Microorganisms from HCWs' hands could be transferred to the surfaces of the mobile phones during their use.

Methods

200 HCWs were screened; samples from the hands of 200 participants and 200 mobile phones were cultured.

Results

In total, 94.5% of phones demonstrated evidence of bacterial contamination with different types of bacteria. The gram negative strains were isolated from mobile phones of 31.3% and the ceftazidime resistant strains from the hands were 39.5%. S. aureus strains isolated from mobile phones of 52% and those strains isolated from hands of 37.7% were methicillin resistant. Distributions of the isolated microorganisms from mobile phones were similar to hands isolates. Some mobile phones were contaminated with nosocomial important pathogens.

Conclusion

These results showed that HCWs' hands and their mobile phones were contaminated with various types of microorganisms. Mobile phones used by HCWs in daily practice may be a source of nosocomial infections in hospitals.

Hand washing soap as a source of neonatal Serratia marcescens outbreak

OBJECTIVE

To describe an outbreak of Serratia marcescens infections in a neonatal intensive care unit (NICU) and to report investigations and interventions having led to the cessation of the outbreak.

DESIGN

Observational study of microbiological and epidemiological investigations realised during a S. marcescens outbreak between March and October 2006.

METHODS

Nine cases were observed in a 5 months period. A Serratia outbreak was therefore identified, and all the strains were compared by pulsed-field gel electrophoresis (PFGE). Data from medical notes were gathered retrospectively. Environmental samples were gathered prospectively.

RESULTS

Four infants were colonized and five infants were infected by S. marcescens. PFGE revealed that three different strains were present. Seven of the nine babies were infected by only one of these strains. This same strain was found in a nonantimicrobial soap bottle (NAS) that could be the source of contamination.

CONCLUSION

It is the first time that S. marcescens is found in a NAS during a neonatal nosocomial outbreak. Molecular analysis is a method of choice to compare different strains. Identification and elimination of the nosocomial source and adherence to the infection control policies are essential to succeed in the containment of a nosocomial epidemic.

Multifactorial origin of high incidence of Serratia marcescens in a cardio-thoracic ICU: analysis of risk factors and epidemiological characteristics

OBJECTIVE

A four-fold increase in the incidence of Serratia marcescens occurred in a cardio-thoracic ICU within a 13-month period. Clinical, epidemiological and molecular characteristics were analysed to elucidate the outbreak's origin.

METHODS

Epidemiological data were analysed by mapping clustered cases; isolates were genotyped by AFLP analysis. A case-control study was performed to identify risk factors for the acquisition of S. marcescens. Data were obtained from files and electronic databases of the ICU and Department of Medical Microbiology. The adherence to hygiene protocols on the ICU was reviewed by a medical audit.

RESULTS

Genotyping showed 16 distinct S. marcescens strains. Twenty-one cases and 39 controls were enrolled in the case-control study. Significant differences found by univariate analysis included the duration of surgery, APACHE-II-score on ICU admission, length of ICU stay, duration of mechanical ventilation, tube feeding and the sum of the number of days per invasive device. In a multivariate logistic regression model, the length of ICU stay and tube feeding were independent risk factors. Outbreak strains were not more frequently resistant to gentamicin, ciprofloxacin, meropenem or trimethoprim-sulfamethoxazole as compared to a reference group. Hygiene protocols, including hand washing, were insufficiently practiced by the ICU's medical staff.

CONCLUSIONS

The heterogeneity of the strains points to transmission from various sources. This outbreak of S. marcescens was most probably caused by reduced hand washing and other breaks in infection prevention protocols in combination with the presence of the identified risk factors, which act by affecting the number and intensity of potential transmission events.

Outbreaks of Serratia marcescens bacteriuria in a neurosurgical intensive care unit of a tertiary care teaching hospital: a clinical, epidemiologic, and laboratory perspective

BACKGROUND

Serratia marcescens is an aerobic gram-negative bacillus belonging to the family Enterobacteriacea. Infections caused by S marcescens may be difficult to treat because of their resistance to a variety of antibiotics, including beta-lactams and aminoglycosides.

METHODS

This study aimed to (1) identify the risk factors associated with the development of Serratia marcescens bacteriuria in neurosurgical intensive care units (NSICU); (2) genotype the pathogens to determine the source of infection; (3) compare these results with antibiograms; and (4) determine and implement appropriate control measures. A retrospective case-control study of the epidemiologic data, the surveillance of environmental cultures, and the genotyping of strains using arbitrarily primed polymerase chain reaction (AP-PCR) were performed at a 750-bed, tertiary care teaching hospital. Seventy-four bacteriuria patients were compared with 74 age/sex-matched control patients in the NSICU between March 2002 and March 2004. The factors assessed were patient demographics; duration of hospital stay; duration of indwelling catheter use before and during stay in the NSICU; chronic underlying illnesses (diabetes mellitus, cardiovascular disease, malignancy); other sites of infection; history of trauma; exposure to a nasogastric tube; mechanical ventilation; urinary catheterization; central venous catheterization; surgical drainage; tracheostomy; brain or spine surgery; and receipt of total parenteral nutrition (TPN), antimicrobials (beta-lactams, aminoglycosides, quinolones, carbapenems, vancomycins), or steroids.

RESULTS

Patients with S marcescens bacteriuria were more likely to have a longer NSICU stay and other sites of infection. Environmental surveillance showed the handling of urine jugs to be the point source of contamination. Genotyping and antibiograms of 14 patients were the same except for those of 2 patients.

CONCLUSION

The patient-related risk factors were identified, and a rapid identification of the organism was made. Heightened surveillance, infection control measures, and empiric therapy led to improved methods for handling urine jugs, which terminated the outbreak.

A simultaneous outbreak of Serratia marcescens and Klebsiella pneumoniae in a neonatal intensive care unit

We describe two concurrent outbreaks of Serratia marcescens and Klebsiella pneumoniae in a neonatal intensive care unit (NICU). Over a 16-month period, a total of 27 infants were either colonized (N=14) or infected (N=13). There were 15 cases of S. marcescens and 11 cases of K. pneumoniae. Both micro-organisms were involved in one fatal case. Seven preterm babies developed septicaemia, two had bacteraemia, three had respiratory infections and one had purulent conjunctivitis. The S. marcescens and K. pneumoniae isolates were investigated by three molecular methods: enterobacterial repetitive intergenic consensus polymerase chain reaction (PCR), arbitrary primed PCR with M13 primer, and random amplification of polymorphic DNA. Different patterns were found in the 16 S. marcescens epidemic isolates from 16 newborn infants. The major epidemic-involved genotype was linked to the first nine cases and this was subsequently replaced by different patterns. Eight different typing profiles were also determined for the 13 K. pneumoniae isolates from 12 newborn infants. Four K. pneumoniae bacteraemic strains proved to be identical. In conclusion, the typing results revealed that two different micro-organisms (S. marcescens and K. pneumoniae) were simultaneously involved in invasive nosocomial infections in preterm newborns. Two simultaneous clusters of cases were documented. Heterogeneous genotypes among both species were also demonstrated to be present in the NICU at the same time. A focal source for both micro-organisms was not identified but cross-transmission through handling was probably an important route in this outbreak. Strict adherence to handwashing policies, cohorting, isolation of colonized and infected patients, and rigorous environmental hygiene were crucial measures in the containment of the epidemic.

Outbreak of extended spectrum beta-lactamase-producing Klebsiella pneumoniae infection in a neonatal intensive care unit related to onychomycosis in a health care worker

Four cases of infection by extended spectrum beta-lactamase-producing Klebsiella pneumoniae occurred in the neonatal intensive care unit. Isolation, empiric therapy change and education produced no effect. Newborn weekly colonization rates were 0-18.7%. One health care worker with onychomycosis was positive for extended spectrum beta-lactamase-producing K. pneumoniae. Isolates were identical by molecular typing. Outbreak was controlled when the health care worker was excluded from the neonatal intensive care unit.

Clustering of Serratia marcescens infections in a neonatal intensive care unit

OBJECTIVES

To study clusters of infections caused by Serratia marcescens in a neonatal intensive care unit (NICU) and to determine risk factors for S. marcescens infection or colonization.

DESIGN

Genotyping of S. marcescens isolates was performed by pulsed-field gel electrophoresis (PFGE). A retrospective case-control study was conducted.

SETTING

A tertiary-care pediatric hospital with a 16-bed NICU.

PATIENTS

All neonates with at least one culture positive for S. marcescens in the NICU during December 1999 to July 2002. Case-patients (n = 11) treated in the NICU during December 1999 to February 2000 were included in the case-control study. Neonates treated in the NICU for at least 72 hours during the same period with cultures negative for S. marcescens were used as control-patients (n = 27).

RESULTS

S. marcescens was cultured from 19 neonates; 9 were infected and 10 were colonized. PFGE analysis identified three epidemic strains; each cluster consisted of identical isolates, except one isolate in the first cluster that was different. The risk factors identified were low birth weight, prematurity, prolonged respiratory therapy, prolonged use of antibiotics, and maternal infection prior to delivery. Overcrowding and understaffing were recorded simultaneously with the clusters.

CONCLUSIONS

PFGE analysis showed three independent clusters. Several factors contributed to spread of the epidemic strains: (1) there were many severely premature and susceptible neonates, (2) the NICU was overcrowded during the clusters, and (3) transmission was likely to occur via the hands of staff. Cohorting and improvement of routine infection control measures led to the cessation of each cluster.

Étude cas-témoins d’une épidémie à Serratia marcescens dans un service de réanimation pédiatrique

OBJECTIVES

To identify patient-related risk factors of infection and ways of transmission of extended-spectrum betalactamase (ESBL) producing Serratia marcescens in the paediatric intensive care unit (PICU) of Amiens university hospital (France) between June and July 2002.

METHODS

Five cases (four pulmonary infected and one stool contaminated symptom-free neonates) and 35 controls, admitted in the PICU, are included. S. marcescens ESBL analysed are isolated from respiratory tract and faecal samples for cases and urine and pus samples from two non-paediatric other patients. Univariate and multivariate analysis are performed on EPI INFO 6.04 dFr and SPSS 11.0.1.

RESULTS

S. marcescens ESBL infections or colonisations rate is 12.5% [4.7-27.6]. The incidence is 8.8 [6.7-11.6] per 1000 hospital-stay days. By univariate analysis, cases and controls don't differ with respect of age, sex, and weight at admission or preterm delivery. Cases don't have more often invasive nursing care than controls. But, they were intubated (P <0.03) and hospitalised (P <0.03) for a longer time than controls. Linear regression analysis showed that duration of intubation was independent predictor of acquisition of S. marcescens ESBL (P <0.008). S. marcescens ESBL strains implicated in pulmonary infections, showed the same pattern of multidrug resistant and ERIC-PCR profile. This clone differs from others isolated from stool or other samples from other hospital wards.

CONCLUSION

As S. marcescens cross-colonization appears to be due to lake of hand hygiene and asepsis during invasive nursing care, reinforcing hygiene measures permit to contain the outbreak.

Klebsiella pneumoniae bloodstream infections among neonates in a high-risk nursery in Cali, Colombia

OBJECTIVES

To determine the cause of an outbreak of Klebsiella pneumoniae bloodstream infections (BSIs) among neonates in a high-risk nursery and to institute control measures.

DESIGN

During the on-site investigation, a cohort study to identify risk factors for K. pneumoniae BSI, a point-prevalence study to assess K. pneumoniae colonization, a maternal cohort study to determine maternal K. pneumoniae colonization, and an observational study to evaluate healthcare worker (HCW) compliance with infection control practices were conducted.

PATIENTS AND SETTING

Neonates in a 40-bed high-risk nursery in a 700-bed university hospital in Cali, Colombia.

INTERVENTION

Cohorting of neonates colonized with K. pneumoniae.

RESULTS

The overall K. pneumoniae BSI attack rate was 10 of 105 (9.5%). In the retrospective cohort study, the number of blood transfusions (OR, 3.1 per transfusion; P = .02; CI95, 1.4-9.7) and intravenous injections (OR, 1.2 per injection; P = .04; CI95, 1.0-1.5) were independently associated with K. pneumoniae BSI. The overall prevalence of K. pneumoniae colonization was 61% among neonates and 7% among mothers. During the HCW assessment, suboptimal intravenous therapy practices were observed. A cohorting intervention resulted in a significant reduction in K. pneumoniae colonization (12% vs 61%; RR, 0.19; P < .001). During the intervention period, no K. pneumoniae BSIs occurred.

CONCLUSIONS

This investigation suggested that the outbreak probably occurred due to widespread colonization and suboptimal infection control and intravenous therapy practices. Cohorting successfully reduced the overall prevalence of K. pneumoniae colonization and, along with improved infection control practices, probably prevented K. pneumoniae BSIs

Identification of Serratia marcescens populations of nosocomial origin by RAPD-PCR

BACKGROUND

Serratia marcescens has been increasingly identified as a cause of infection in the immunocompromised host and in high-mortality-rate nosocomial outbreaks. It is thus important to use identification methods that allow study of the dynamics and evolution of nosocomial S. marcescens strains. The aim of this study was to identify S. marcescens strains isolated from nosocomial outbreaks in two pediatric hospitals by random amplification polymorphic DNA polymerase chain reaction (RAPD-PCR).

METHODS

RAPD-PCR was used to study five S. marcescens populations isolated from four different nosocomial outbreaks that occurred in two pediatric hospitals. This method was compared with the widely used biotyping system described by Grimont and Grimont.

RESULTS

The combination of biotypification and RAPD-PCR allowed accurate identification of S. marcescens strains isolated in nosocomial outbreaks at pediatric hospitals; by RAPD-PCR, we were able to analyze clonal variations in S. marcescens populations. We established bacterial dissemination patterns in hospital environments according to hospital administration of medical services and compared changes in bacterial DNA amplification patterns in each hospital related with clonal variations by selective pressures.

CONCLUSIONS

RAPD-PCR is a useful method to identify S. marcescens strains associated with nosocomial outbreaks.

Clinical challenges of nosocomial infections caused by antibiotic-resistant pathogens in pediatrics

Antibiotic resistance in nosocomial infections is an ever-increasing problem as health care institutions provide care for children with more complicated medical and surgical problems. Several mechanisms of antibiotic resistance are reviewed for both gram-negative and gram-positive nosocomial pathogens. These adaptive resistance mechanisms allow organisms to survive in an environment of extensive antibiotic use and result in clinically significant infections. Mobile genetic elements have facilitated the rapid spread of antibiotic resistance within and among species. The clinical challenge faced by many practitioners is to understand these mechanisms of antibiotic resistance and to develop strategies for successfully treating infection caused by resistant pathogens. Nosocomial outbreaks caused by resistant organisms are described, and an approach to empiric therapy based on presumed pathogens, site of infection, and local resistance patterns is discussed.

An outbreak of Serratia marcescens bacteremia after general anesthesia

OBJECTIVE

To investigate an outbreak of Serratia marcescens bacteremia among patients after general anesthesia.

DESIGN

A case-control study.

SETTING

A 304-bed, pediatric teaching hospital.

PATIENTS

Twenty-three pediatric patients who developed S. marcescens bacteremia within 2 weeks after general anesthesia between June 15 and September 22, 1999, were compared with 46 age-matched control-patients who had undergone procedures on the same clinical services of the hospital during the same period.

RESULTS

Cases were distributed over a wide range of surgical services and were not correlated with exposure to any of the surgical, anesthesia, or nursing staff. Case-patients were significantly more likely than control-patients to have received cefazolin (odds ratio [OR], 11.1; 90% confidence interval [CI90], 1.9 to 24.3) or to have had perioperative placement of a central vascular catheter (OR, 4.2; CI90, 1.2 to 18.8). The timing of the procedures of patients who subsequently developed S. marcescens bacteremia was significantly associated with the shifts of one or more of five operating room technicians (OR, 2.9 to 6.8) who were responsible for preparing intravenous fluids used both to reconstitute perioperatively administered antibiotics and to prime central vascular catheter assemblies.

CONCLUSIONS

Our findings are consistent with a pattern of intermittent contamination due to periodic breaches in sterile technique, rather than a point-source of contamination. The unique challenges that such a procedural breakdown presents to an epidemiologic investigation are discussed. This outbreak stresses the importance of providing comprehensive training in antisepsis when multifunctional personnel are incorporated into an operating room work environment.

Comparative surface-to-hand and fingertip-to-mouth transfer efficiency of gram-positive bacteria, gram-negative bacteria, and phage

AIMS

To determine the transfer efficiency of micro-organisms from fomites to hands and the subsequent transfer from the fingertip to the lip.

METHODS AND RESULTS

Volunteers hands were sampled after the normal usage of fomites seeded with a pooled culture of a Gram-positive bacterium (Micrococcus luteus), a Gram-negative bacterium (Serratia rubidea) and phage PRD-1 (Period A). Activities included wringing out a dishcloth/sponge, turning on/off a kitchen faucet, cutting up a carrot, making hamburger patties, holding a phone receiver, and removing laundry from the washing machine. Transfer efficiencies were 38.47% to 65.80% and 27.59% to 40.03% for the phone receiver and faucet, respectively. Transfer efficiencies from porous fomites were <0.01%. In most cases, M.luteus was transferred most efficiently, followed by phage PRD-1 and S. rubidea. When the volunteers' fingertips were inoculated with the pooled organisms and held to the lip area (Period B), transfer rates of 40.99%, 33.97%, and 33.90% occurred with M. luteus, S. rubidea, and PRD-1, respectively.

CONCLUSIONS

The highest bacteral transfer rates from fomites to the hands were seen with the hard, non-porous surfaces. Even with low transfer rates, the numbers of bacteria transferred to the hands were still high (up to 10(6) cells). Transfer of bacteria from the fingertip to the lip is similar to that observed from hard surfaces to hands.

SIGNIFICANCE AND IMPACT OF THE STUDY

Infectious doses of pathogens may be transferred to the mouth after handling an everyday contaminated household object.

An outbreak of Serratia marcescens infection in a special-care baby unit of a community hospital in United Arab Emirates: the importance of the air conditioner duct as a nosocomial reservoir

We report an outbreak of Serratia marcescens infection in a special-care baby unit (SCBU) of a university-affiliated community hospital in the United Arab Emirates. The outbreak involved 36 infants and lasted for 20 weeks. Seven of the colonized infants developed invasive illnesses in the form of bacteraemia (four cases), bacteraemic meningitis (two) and clinical sepsis (one). Three other term infants had purulent conjunctivitis. There were five deaths with an overall mortality of 14%. S. marcescens was cultured from airflow samples from the air conditioning (AC) which was the reservoir of infection in this outbreak. Elimination of the nosocomial source and outbreak containment were eventually achieved by specialized robotic cleaning of the entire AC duct system of the SCBU. Strict adherence to the infection control policies was reinforced to prevent transmission of cross-infection.