IMP-1-producing carbapenem-resistant Acinetobacter ursingii from Japan

Comparative analysis of IMP-4- and OXA-58-containing plasmids of three carbapenemase-producing Acinetobacter ursingii strains in the Netherlands

OBJECTIVES

A recent occurrence of carbapenemase-producing Acinetobacter ursingii was reported in the Netherlands and comprised three unrelated strains carrying the bla_IMP-4 and bla_OXA-58 encoding genes. The objective was to investigate a putative common source of the carbapenemase resistance genes and plasmids in these A. ursingii strains.

METHODS

Hybrid assembly of short-read and long-read sequencing data was performed using Unicycler and assembled genomes were analysed by ResFinder and PlasmidFinder.

RESULTS

Hybrid assemblies of A. ursingii genomes yielded a circular chromosome, a large plasmid harboring bla_IMP-4 and bla_OXA-58 genes (sizes 259-317kb), and four to five other smaller plasmids. ResFinder analyses revealed 16 other acquired resistance genes on the plasmids carrying the bla_IMP-4 and bla_OXA-58 genes. These 18 genes encode resistance towards eight antibiotic classes. The smaller plasmids did not carry acquired resistance genes. Comparative analysis showed that the three bla_IMP-4/bla_OXA-58 plasmids were similar (61%-83%) and shared 13 to 17 of the 18 resistance genes. BLAST analysis showed that the bla_IMP-4/bla_OXA-58 plasmids were not reported before. However, a close match with a 399 kb plasmid from Acinetobacter johnsonii was found (99% similarity, 80% coverage). This A. johnsonii plasmid contains the bla_OXA-58 gene, but lacks bla_IMP-4, and it shares eight other resistance genes with those present on the A. ursingii bla_IMP-4/bla_OXA-58 plasmids.

CONCLUSION

Three bla_IMP-4/bla_OXA-58-carrying plasmids were characterized in three carbapenemase-producing A. ursingii strains. The plasmids were highly similar, suggesting a putative common source or co-selection of resistance genes from A. johnsonii. These results provide initial insights in the dissemination of carbapenem-resistance in A. ursingii in the Netherlands.

Catheter-related bloodstream infection due to Acinetobacter ursingii in a hemodialysis patient: case report and literature review

Acinetobacter ursingii is an anaerobic gram negative opportunistic coccobacillus, rarely isolated in bacteremic patients. It is mainly found in immunocompromised and severely ill patients with no identifiable source of infection. When isolated into the bloodstream, it usually displays resistance to at least two antimicrobial agents. To date only seven cases of bacteremia due to this microorganism have been reported in adults, of which, this accounts for the second one associated to renal replacement therapy and the first case of a documented catheter-related bloodstream infection (CRBSI) in a patient with a hemodialysis catheter. A 78-year-old male presented into the emergency department with acute kidney injury requiring hemodialysis, later developing bacteremia due to Acinetobacter ursingii.

Oral colonisation by antimicrobial-resistant Gram-negative bacteria among long-term care facility residents: prevalence, risk factors, and molecular epidemiology

Background

For residents of long-term care facilities (LTCFs), antimicrobial-resistant bacteria (ARB) are a risk factor, yet their oral colonisation, potentially leading to aspiration pneumonia, remains unclear. This study was undertaken to survey the prevalence, phenotypic characteristics, and molecular epidemiology of antimicrobial-resistant Gram-negative bacteria in the oral cavity of LTCF residents, and to analyse the risk factors for such carriers.

Methods

This study involved 98 residents of a LTCF in Hiroshima City, Japan, aged between 55 and 101 years. Oropharyngeal swabs were collected and plated on screening media for ESBL-producing and carbapenem-resistant bacteria; isolates were identified and tested for antibiotic susceptibility; biofilm formation was tested in vitro; identification of epidemic clones were pre-determined by PCR; resistance genes, sequence types, and whole-genome comparison of strains were conducted using draft genome sequences. Demographic data and clinical characterisations were collected and risk factors analysed.

Results

Fifty-four strains from 38% of the residents grew on screening media and comprised predominantly of Acinetobacter spp. (35%), Enterobacteriaceae spp. (22%), and Pseudomonas spp. (19%). All Escherichia coli isolates carried CTX-M-9 group and belonged to the phylogroup B2, O25:H4 ST131 fimH30 lineage. Six Acinetobacter baumannii isolates presented identical molecular characteristics and revealed more biofilm production than the others, strongly suggesting their clonal lineage. One Acinetobacter ursingii isolate displayed extensive resistance to various ß-lactams due to multiple acquired resistance genes. One Pseudomonas aeruginosa isolate showed exceptional resistance to all ß-lactams including carbapenems, aminoglycosides, and a new quinolone, showing a multidrug-resistant Pseudomonas aeruginosa (MDRP) phenotype and remarkable biofilm formation. Genome sequence analysis revealed this isolate was the bla_IMP-1-positive clone ST235 in Japan. Strokes (cerebral infarction or cerebral haemorrhage) and percutaneous endoscopic gastrostomy tubes were recognised as risk factors for oral colonisation by ARB in the LTCF residents.

Conclusions

ARB, as defined by growth on screening agar plates, which carried mobile resistance genes or elements or conferred high biofilm formation, were already prevalent in the oral cavity of LTCF residents. Health-care workers involved in oral care should be aware of antimicrobial resistance and pay special attention to transmission prevention and infection control measures to diminish ARB or mobile resistance elements dissemination in LTCFs.

Characteristics of invasive Acinetobacter infection: A multicenter investigation with molecular identification of causative organisms

We examined microbiological and clinical characteristics of invasive Acinetobacter infection occurring in four hospitals located in the Minami-Ibaraki Area. Glucose-non-fermentative Gram-negative bacilli isolated from the blood and the cerebrospinal fluid in independent cases between 2001 and 2014 were consecutively collected and those possibly to be Acinetobacter species were re-identified using molecular methods. Of 158 strains identified as Acinetobacter species, 155 were classified into 16 officially designated species, including 42 Acinetobacter pittii and 40 Acinetobacter baumannii. Imipenem non-susceptibility was detected only in 4 strains, none of which demonstrated multidrug resistance. Retrospective analyses of 154 cases for which medical records were fully available showed that the most common cause of infection was primary bloodstream infection (134 cases), of which 128 were related to intravascular catheter use. The mortality on day 28 after the onset was independently associated with cerebrovascular disease, moderate to severe renal disease, the Pitt bacteremia score, and infection other than primary bloodstream infection but not with appropriate empiric antimicrobial therapy. Isolation of A. baumannii was significantly associated with septic shock but not with the 28-day mortality. These findings, obtained in a region where drug-resistant Acinetobacter strains were much less prevailing, indicated that non-baumannii Acinetobacter species were common pathogens, that the most predominant cause of invasive Acinetobacter infection was intravascular catheter-related infection, that virulence of A. baumannii might be higher than those of other species but its association with mortality was unclear, and that administration of broad-spectrum antibiotics targeting Acinetobacter species might be deferrable in a certain situation.

Clinical and Pathophysiological Overview of Acinetobacter Infections: a Century of Challenges

Acinetobacter is a complex genus, and historically, there has been confusion about the existence of multiple species. The species commonly cause nosocomial infections, predominantly aspiration pneumonia and catheter-associated bacteremia, but can also cause soft tissue and urinary tract infections. Community-acquired infections by Acinetobacter spp. are increasingly reported. Transmission of Acinetobacter and subsequent disease is facilitated by the organism's environmental tenacity, resistance to desiccation, and evasion of host immunity. The virulence properties demonstrated by Acinetobacter spp. primarily stem from evasion of rapid clearance by the innate immune system, effectively enabling high bacterial density that triggers lipopolysaccharide (LPS)-Toll-like receptor 4 (TLR4)-mediated sepsis. Capsular polysaccharide is a critical virulence factor that enables immune evasion, while LPS triggers septic shock. However, the primary driver of clinical outcome is antibiotic resistance. Administration of initially effective therapy is key to improving survival, reducing 30-day mortality threefold. Regrettably, due to the high frequency of this organism having an extreme drug resistance (XDR) phenotype, early initiation of effective therapy is a major clinical challenge. Given its high rate of antibiotic resistance and abysmal outcomes (up to 70% mortality rate from infections caused by XDR strains in some case series), new preventative and therapeutic options for Acinetobacter spp. are desperately needed.

Severe Community-Acquired Bloodstream Infection with Acinetobacter ursingii in Person who Injects Drugs

We report a community-acquired bloodstream infection with Acinteobacter ursingii in an HIV-negative woman who injected drugs. The infection was successfully treated with meropenem. Species identification was performed by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Improved identification of Acinetobacter spp. by using this method will help identify clinical effects of this underdiagnosed pathogen.

Bacteremia due to Acinetobacter ursingii in infants: Reports of two cases

Acinetobacter ursingii is an aerobic, gram-negative, opportunistic microorganism which is rarely isolated among Acinetobacter species. We present two immunocompetent infants who developed bacteremia due to A. ursingii. The first patient is a two -month- old boy who had been hospitalized in pediatric surgery unit for suspected tracheo-esophageal fistula because of recurrent aspiration pneumonia unresponsive to antibiotic therapy. The second patient is a fourteen -month- old boy with prolonged vomiting and diarrhea. A. ursingii was isolated from their blood cultures. They were successfully treated with ampicillin-sulbactam. Although A. ursingii has recently been isolated from a clinical specimen; reports of infection with A. ursingii in children are rare. A. ursingii should be kept in mind as an opportunistic microorganism in children.

[Multiresistant gram-negative bacteria. A bacterial challenge of the twenty-first century]

The incidence of human-pathogenic microorganisms with resistance or even complete insensitivity to broad-spectrum antibiotics is increasing. This poses a serious challenge to infection control in hospitals and to hygiene strategies in clinical areas with critically ill patients, particularly intensive care or transplant units. These microorganisms create problems that are seemingly impossible to solve at present. The management of gram-positive pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) has been facilitated by evidence-based recommendations resulting in a measurable decrease in the incidence of infection and, where treatment is concerned, in a selection of reliably effective drugs for clinicians. However, in the more frequent cases of multiresistant gram-negative (MRGN) pathogens, the only option is the use of poorly defined regimens with older drugs, which carry the risk of serious side effects and organ toxicities. This article presents a comparative analysis of hospital hygiene management for MRSA and MRGN pathogens, pointing out both similarities and features which are unique to MRGN pathogens.