Emergence of Enterobacter cloacae as a common pathogen in neonatal units: pulsed-field gel electrophoresis analysis

Enterobacter spp.: Update on Taxonomy, Clinical Aspects, and Emerging Antimicrobial Resistance

The genus Enterobacter is a member of the ESKAPE group, which contains the major resistant bacterial pathogens. First described in 1960, this group member has proven to be more complex as a result of the exponential evolution of phenotypic and genotypic methods. Today, 22 species belong to the Enterobacter genus. These species are described in the environment and have been reported as opportunistic pathogens in plants, animals, and humans. The pathogenicity/virulence of this bacterium remains rather unclear due to the limited amount of work performed to date in this field. In contrast, its resistance against antibacterial agents has been extensively studied. In the face of antibiotic treatment, it is able to manage different mechanisms of resistance via various local and global regulator genes and the modulation of the expression of different proteins, including enzymes (β-lactamases, etc.) or membrane transporters, such as porins and efflux pumps. During various hospital outbreaks, the Enterobacter aerogenes and E. cloacae complex exhibited a multidrug-resistant phenotype, which has stimulated questions about the role of cascade regulation in the emergence of these well-adapted clones.

Overestimation of an Outbreak of Enterobacter cloacae in a Neonatal Intensive Care Unit in Germany, 2015

BACKGROUND

In August 2015, 17 neonates with Enterobacter cloacae (E. cloacae) colonization were identified in a neonatal intensive care unit (NICU) in Germany. Two developed severe brain abscesses. Despite temporary NICU closure in September, another infant with E. cloacae colonization was detected in October 2015.

METHODS

We defined potential cases as inpatients treated in the NICU or any pediatric/maternity ward in 2015 with E. cloacae in any specimen before molecular typing. Cases were at first confirmed by arbitrarily-primed-polymerase-chain-reaction and later by XbaI-macrorestriction/pulsed-field gel electrophoresis and next-generation-sequencing. Enhanced barrier precautions and cohorting were implemented for all potential cases and microbiologic screening was extended from NICU to all pediatric/maternity wards.

RESULTS

Of 41 potential cases (occurring between 08/04/2015 and 15/11/2015 in 4 wards), the isolates of 23 shared identical arbitrarily-primed-polymerase-chain-reaction patterns; 3 without plausible epidemiologic link. Pulsed-field gel electrophoresis analyses verified only 10 cases (all in the NICU); next-generation-sequencing analysis confirmed these results. In addition 6 cases without isolates available for genotyping were closely linked in place and time.

CONCLUSIONS

Forty-one suspected patients were cohorted and the NICU was temporarily closed. Further analyses revealed that only 16 cases belonged to the outbreak. Only close interdisciplinary collaboration and highly discriminatory genotyping methods allowed to clearly differentiate between cases and noncases in this E. cloacae outbreak.

Outbreak of IMI-1 carbapenemase-producing colistin-resistant Enterobacter cloacae on the French island of Mayotte (Indian Ocean)

The spread of carbapenemase-producing Enterobacteriaceae in the Southwest Indian Ocean islands is poorly known. Here we describe an outbreak of colistin-resistant Enterobacter cloacae harbouring bla_IMI-1 in the French overseas department of Mayotte. Between October 2015 and January 2017, all isolates of imipenem-non-susceptible E. cloacae at Mayotte Medical Center and University Hospital of Reunion Island were screened for carbapenemase production. Positive isolates were typed by pulsed-field gel electrophoresis and whole-genome sequencing (WGS)-based multilocus sequence typing (MLST), and all β-lactamase genes were identified by PCR and sequencing. Resistance profiles were determined by agar diffusion and Etest. Genetic support of the bla_IMI-1 gene was determined by WGS. A total of 18 E. cloacae isolates harbouring bla_IMI-1 were detected in 17 patients from Mayotte. Pulsed-field gel electrophoresis (PFGE) analysis showed 16 of the 18 strains to be clonally related and belonging to ST820. Based on clinical data, this outbreak most likely had a community origin. The bla_IMI-1 gene in the 18 isolates was carried by a new variant of an integrative mobile element involving the Xer recombinases, called EcloIMEX-8. The mcr-1-mcr-5 genes were absent from the collection. The isolates belonged to E. cloacae cluster XI, known to be colistin heteroresistant. Here we report the first outbreak of IMI-1-producing Enterobacteriaceae. IMI-1-producers may be underdetected in microbiology laboratories because of their unusual antimicrobial resistance profile (resistant to imipenem but with intermediate resistance to ertapenem and susceptible to extended-spectrum cephalosporins) and the absence of bla_IMI-1 in the panel of genes targeted by molecular diagnostic kits.

Multidrug-Resistant Gram-Negative Bacilli: Infection Control Implications

Antimicrobial resistance is a common iatrogenic complication of both modern life and medical care. Certain multidrug resistant and extensively drug resistant Gram-negative organisms pose the biggest challenges to health care today, predominantly owing to a lack of therapeutic options. Containing the spread of these organisms is challenging, and in reality, the application of multiple control measures during an evolving outbreak makes it difficult to measure the relative impact of each measure. This article reviews the usefulness of various infection control measures in containing the spread of multidrug-resistant Gram-negative bacilli.

Epidemic microclusters of blood-culture proven sepsis in very-low-birth weight infants: experience of the German Neonatal Network

Introduction

We evaluated blood culture-proven sepsis episodes occurring in microclusters in very-low-birth-weight infants born in the German Neonatal Network (GNN) during 2009–2010.

Methods

Thirty-seven centers participated in GNN; 23 centers enrolled ≥50 VLBW infants in the study period. Data quality was approved by on-site monitoring. Microclusters of sepsis were defined as occurrence of at least two blood-culture proven sepsis events in different patients of one center within 3 months with the same bacterial species. For microcluster analysis, we selected sepsis episodes with typically cross-transmitted bacteria of high clinical significance including gram-negative rods and Enterococcus spp.

Results

In our cohort, 12/2110 (0.6%) infants were documented with an early-onset sepsis and 235 late-onset sepsis episodes (≥72 h of age) occurred in 203/2110 (9.6%) VLBW infants. In 182/235 (77.4%) late-onset sepsis episodes gram-positive bacteria were documented, while coagulase negative staphylococci were found to be the most predominant pathogens (48.5%, 95%CI: 42.01–55.01). Candida spp. and gram-negative bacilli caused 10/235 (4.3%, 95%CI: 1.68% –6.83%) and 43/235 (18.5%) late-onset sepsis episodes, respectively. Eleven microclusters of blood-culture proven sepsis were detected in 7 hospitals involving a total 26 infants. 16/26 cluster patients suffered from Klebsiella spp. sepsis. The median time interval between the first patient’s Klebsiella spp. sepsis and cluster cases was 14.1 days (interquartile range: 1–27 days). First patients in the cluster, their linked cases and sporadic sepsis events did not show significant differences in short term outcome parameters.

Discussion

Microclusters of infection are an important phenomenon for late-onset sepsis. Most gram-negative cluster infections occur within 30 days after the first patient was diagnosed and Klebsiella spp. play a major role. It is essential to monitor epidemic microclusters of sepsis in surveillance networks to adapt clinical practice, inform policy and further improve quality of care.

Late-onset Enterobacter cloacae sepsis in very-low-birth-weight neonates: experience in a medical center

OBJECTIVE

The objective of this study was to review the early clinical profiles and outcomes of very-low-birth-weight (VLBW) neonates with late-onset sepsis caused by Enterobacter cloacae.

METHODS

We reviewed the medical records of VLBW neonates whose blood and/or cerebral spinal fluid yielded E. cloacae after 3 days of hospitalization in our neonatal intensive care unit.

RESULTS

From January 1997 to December 2006, a total of 29 episodes of E. cloacae infection occurred in 28 VLBW neonates. The onset of E. cloacae infection ranged from 4 to 70 days (27.4 +/- 9.6) days after birth. The most common symptoms and signs of sepsis were desaturation (58.6%), tachycardia (58.6%), apnea (55.2%), unstable body temperature (48.3%), and decreased activity (44.8%). The infected neonates had an average of four kinds of symptoms in each sepsis episode. The most common laboratory findings in VLBW neonates with E. cloacae sepsis were thrombocytopenia (65.5%), C-reactive protein > or = 1 mg/dL (55.2%), band-form neutrophils > or = 5% (41.4%), and leucopoenia (20.7%). Empirical intravenous antibiotic therapy comprising piperacillin (or piperacillin and tazobactam) and gentamicin (or amikacin) was successful in the early treatment of 24 episodes of E. cloacae sepsis in 25 patients. Three neonates (10.7%) died due to E. cloacae sepsis. Four neonates (14.3%) developed E. cloacae meningitis, and two of them developed brain abscesses.

CONCLUSIONS

E. cloacae infection in VLBW neonates usually presents with nonspecific symptoms and signs. Early recognition of sepsis and empirical combination of piperacillin (or piperacillin and tazobactam) and gentamicin (or amikacin) may be useful for treatment of sepsis caused by this highly virulent pathogen.

A bacterial population study of commercialized wastewater inoculants

AIMS

To assess the bacterial diversity and safety of wastewater inoculants, which are commercially available products used to improve the aerobic digestion processes of the domestic waste compost in the septic tank.

METHODS AND RESULTS

Eighteen wastewater inoculants were analysed on nonselective and selective media and the cultivable bacteria were identified. In all wastewater inoculants, the number of CFUs were between 10(4) and 10(7) g(-1) powder on nonselective media and Bacillus was the predominant cultivable genus. Culture-independent molecular methods such as sequencing of 16S rRNA clone libraries and denaturating gradient gel electrophoresis demonstrated the high prevalence of interfering chloroplast 16S rRNA from plant material and the presence of Bacillus spp. Only after selective enrichments and cultivation, the presence of one pathogenic strain (Klebsiella pneumoniae subsp. pneumoniae) and one opportunistic strain of (Enterobacter cloacae) bacteria were detected in six different products.

CONCLUSION

The predominant cultivable species of the wastewater inoculants were Bacillus spp. and after enrichment six products were found to contain opportunistic or pathogenic strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

The presence of opportunistic pathogenic strains in the inoculants might represent a risk for immunocompromised, the elderly or children. A clear labelling should therefore be displayed on the product.

Phenotypic and genetic analysis of Enterobacter spp. from a Brazilian oligotrophic freshwater lake

We characterized a population of Enterobacter spp. of the Enterobacter cloacae complex isolated from an oligotrophic lake; most isolates were identified as E. cloacae. Fingerprinting polymerase chain reaction (PCR), along with morphological, biochemical, physiological, and plasmid profiles analyses, including antimicrobial susceptibility testing, were performed on 22 environmental isolates. Misidentification occurred when using the API 20E identification system. Analysis of 16S rDNA sequences confirmed the close relatedness between species of the E. cloacae complex. The tDNA PCR allowed the differentiation and identification of the E. cloacae isolates. Evaluation of genetic diversity by 16S rDNA sequence, tDNA, internal transcribed spacers, and enterobacterial repetitive intergenic concensus profiles revealed nearly identical isolates, although they exhibited different physiological and antimicrobial resistance profiles. Among the Enterobacter isolates, 96% were resistant to at least one antimicrobial; multiple resistance was also found at a high frequency (86%). The antimicrobials against which resistance was found most frequently were beta-lactams, chloramphenicol, and streptomycin. Plasmids were found in 21 of the 22 Enterobacter isolates. This confirms the conception that antibiotic resistance can occur in oligotrophic freshwater lake bacteria, which has important implications for public health.

Failure to control an outbreak of qnrA1-positive multidrug-resistant Enterobacter cloacae infection despite adequate implementation of recommended infection control measures

A large outbreak with an aminoglycoside-resistant Enterobacter cloacae (AREC) clone occurred at the University Medical Center Utrecht beginning in 2001 and continued up through the time that this study was completed. This clone (genotype I) contains a conjugative R plasmid carrying the qnrA1, bla(CTX-M-9), and aadB genes, encoding resistance to quinolones, extended-spectrum beta-lactamases, and aminoglycosides, respectively. The aim of this study was to determine whether this clone was more transmissible than other AREC strains. Therefore, the dissemination of this genotype and of other E. cloacae strains was studied. In addition, infection control measures taken were evaluated. Pulsed-field gel electrophoresis analysis divided the 191 AREC strains into 42 different genotypes, of which 5 (12%) involved at least three patients. Aside from this outbreak (133 patients), only two other small outbreaks occurred, showing that the infection control measures were successful for all strains but one. Among 324 aminoglycoside-susceptible E. cloacae strains, 34/166 (20%) genotypes were identified from at least three patients, but only 4 involved small outbreaks. The outbreak strain was also detected in 11 of 15 other Dutch hospitals and caused outbreaks in at least 4. Evaluation of infection control measures showed that the outbreak strain disseminated throughout the hospital despite adequate implementation of internationally accepted guidelines on the control of multidrug-resistant Enterobacteriaceae (MRE). In conclusion, some MRE strains are better able to spread than others, and these strains may not be controlled by the current infection control guidelines. Strategies to identify such strains in an early phase and adapted guidelines for such "superbugs" are needed to prevent these clones from becoming endemic.

Prevention of catheter-related bloodstream infections in the neonatal intensive care setting

Nosocomial infection causes substantial morbidity and mortality among neonates treated in the neonatal intensive care setting. Colonization and subsequent infection of central venous catheters leading to catheter-related bloodstream infection is among the most common causes of nosocomial sepsis in this patient population. Prevention of catheter-related bloodstream infection is a major challenge and numerous strategies have been attempted in this context with varying success. Given the dynamic epidemiology of nosocomial infection among neonates and the emergence of antimicrobial resistance, novel prevention strategies are urgently required.