Emergence of multidrug-resistant Corynebacterium striatum as a nosocomial pathogen in long-term hospitalized patients with underlying diseases

Hard-to-heal peripheral wounds infected with Corynebacterium striatum: a prospective study

OBJECTIVE

To investigate Corynebacterium striatum as a nosocomial pathogen infecting hard-to-heal peripheral wounds, such as skin wounds, soft tissue abscesses and osteomyelitis. As of 2023, the medical community were alerted against the risk of emerging systemic and central infections; on the other hand literature on peripheral cutaneous regions is still scarce.

METHOD

In this study, two groups of patients with similar lesions which were infected were compared: one group with the presence of the coryneform rod, the other without.

RESULTS

In total, Corynebacterium striatum was cultured from 62 patients and 131 samples. Corynebacterium striatum infection correlated well with the presence of: foot ulcer; venous leg ulcer; altered ambulation and/or altered foot loading; peripheral vascular and arterial disease; hospitalisation; malignancy; spinal cord injury; and recent administration of antibiotics (p<0.05 for all associations). Patients with Corynebacterium striatum had a lower overall survival rate compared to patients in the non-Corynebacterium striatum group (28.6 versus 31.6 months, respectively; p=0.0285). Multivariate analysis revealed that Corynebacterium striatum infection was an independent factor for poor prognosis (p<0.0001).

CONCLUSION

In view of the findings of our study, Corynebacterium striatum appears to be an important opportunistic pathogen infecting peripheral tissues and complicating wound healing. Given its numerous and worrying virulence factors (such as multidrug resistance and biofilm production), particular attention should be given to this pathogen by professional wound care providers in nosocomial and outpatient environments.

The Pan-Genomic Analysis of Corynebacterium striatum Revealed its Genetic Characteristics as an Emerging Multidrug-Resistant Pathogen

Corynebacterium striatum is a Gram-positive bacterium that is straight or slightly curved and non-spore-forming. Although it was originally believed to be a part of the normal microbiome of human skin, a growing number of studies have identified it as a cause of various chronic diseases, bacteremia, and respiratory infections. However, despite its increasing importance as a pathogen, the genetic characteristics of the pathogen population, such as genomic characteristics and differences, the types of resistance genes and virulence factors carried by the pathogen and their distribution in the population are poorly understood. To address these knowledge gaps, we conducted a pan-genomic analysis of 314 strains of C. striatum isolated from various tissues and geographic locations. Our analysis revealed that C. striatum has an open pan-genome, comprising 5692 gene families, including 1845 core gene families, 2362 accessory gene families, and 1485 unique gene families. We also found that C. striatum exhibits a high degree of diversity across different sources, but strains isolated from skin tissue are more conserved. Furthermore, we identified 53 drug resistance genes and 42 virulence factors by comparing the strains to the drug resistance gene database (CARD) and the pathogen virulence factor database (VFDB), respectively. We found that these genes and factors are widely distributed among C. striatum, with 77.7% of strains carrying 2 or more resistance genes and displaying primary resistance to aminoglycosides, tetracyclines, lincomycin, macrolides, and streptomycin. The virulence factors are primarily associated with pathogen survival within the host, iron uptake, pili, and early biofilm formation. In summary, our study provides insights into the population diversity, resistance genes, and virulence factors ofC. striatum from different sources. Our findings could inform future research and clinical practices in the diagnosis, prevention, and treatment of C. striatum-associated diseases.

Identification and Characterization of Corynaridin, a Novel Linaridin from Corynebacterium lactis

Genome analysis of Corynebacterium lactis revealed a bacteriocin gene cluster encoding a putative bacteriocin of the linaridin family of ribosomally synthesized and posttranslationally modified peptides (RiPPs). The locus harbors typical linaridin modification enzymes but lacks genes for a decarboxylase and methyltransferase, which is unusual for type B linaridins. Supernatants of Corynebacterium lactis RW3-42 showed antimicrobial activity against Corynebacterium glutamicum. Deletion of the precursor gene crdA clearly linked the antimicrobial activity of the producer strain to the identified gene cluster. Following purification, we observed potent activity of the peptide against Actinobacteria, mainly other members of the genus Corynebacterium, including the pathogenic species Corynebacterium striatum and Corynebacterium amycolatum. Also, low activity against some Firmicutes was observed, but there was no activity against Gram-negative species. The peptide is resilient towards heat but sensitive to proteolytic degradation by trypsin and proteinase K. Analysis by mass spectrometry indicates that corynaridin is processed by cleaving off the leader sequence at a conserved motif and posttranslationally modified by dehydration of all threonine and serin residues, resulting in a monoisotopic mass of 3,961.19 Da. Notably, time-kill kinetics and experiments using live biosensors to monitor membrane integrity suggest bactericidal activity that does not involve formation of pores in the cytoplasmic membrane. As Corynebacterium species are ubiquitous in nature and include important commensals and pathogens of mammalian organisms, secretion of bacteriocins by species of this genus could be a hitherto neglected trait with high relevance for intra- and interspecies competition and infection. IMPORTANCE Bacteriocins are antimicrobial peptides produced by bacteria to fend off competitors in ecological niches and are considered to be important factors influencing the composition of microbial communities. However, bacteriocin production by bacteria of the genus Corynebacterium has been a hitherto neglected trait, although its species are ubiquitous in nature and make up large parts of the microbiome of humans and animals. In this study, we describe and characterize a novel linaridin family bacteriocin from Corynebacterium lactis and show its narrow-spectrum activity, mainly against other actinobacteria. Moreover, we were able to extend the limited knowledge on linaridin bioactivity in general and for the first time describe the bactericidal activity of such a bacteriocin. Interestingly, the peptide, which was named corynaridin, appears bactericidal, but without formation of pores in the bacterial membrane.

Epidemiological Investigation of Hospital Transmission of Corynebacterium striatum Infection by Core Genome Multilocus Sequence Typing Approach

Corynebacterium striatum has recently received increasing attention due to its multiple antimicrobial resistances and its role as an invasive infection/outbreak agent. Recently, whole-genome sequencing (WGS)-based core genome multilocus sequence typing (cgMLST) has been used in epidemiological studies of specific human pathogens. However, this method has not been reported in studies of C. striatum. In this work, we aim to propose a cgMLST scheme for C. striatum. All publicly available C. striatum genomes, 30 C. striatum strains isolated from the same hospital, and 1 epidemiologically unrelated outgroup C. striatum strain were used to establish a cgMLST scheme targeting 1,795 genes (hereinafter referred to as 1,795-cgMLST). The genotyping results of cgMLST showed good congruence with core genome-based single-nucleotide polymorphism typing in terms of tree topology. In addition, the cgMLST provided a greater discrimination than the MLST method based on 6 housekeeping genes (gyrA, gyrB, hsp65, rpoB, secA1, and sodA). We established a clonal group (CG) threshold based on 104 allelic differences; a total of 56 CGs were identified from among 263 C. striatum strains. We also defined an outbreak threshold based on seven allelic differences that is capable of identifying closely related isolates that could give clues on hospital transmission. According to the results of analysis of drug-resistant genes and virulence genes, we identified CG4, CG5, CG26, CG28, and CG55 as potentially hypervirulent and multidrug-resistant CGs of C. striatum. This study provides valuable genomic epidemiological data on the diversity, resistance, and virulence profiles of this potentially pathogenic microorganism. IMPORTANCE Recently, WGS of many human and animal pathogens has been successfully used to investigate microbial outbreaks. The cgMLST schema are powerful genotyping tools that can be used to investigate potential epidemics and provide classification of the strains precise and reliable. In this study, we proposed the development of a cgMLST typing scheme for C. striatum, and then we evaluated this scheme for its applicability to hospital transmission investigations. This report describes the first cgMLST schema for C. striatum. The analysis of hospital transmission of C. striatum based on cgMLST methods has important clinical epidemiological significance for improving nosocomial infection monitoring of C. striatum and in-depth understanding of its nosocomial transmission routes.

Risk of Bronchial Complications After Lung Transplantation With Respiratory Corynebacteria. Results From a Monocenter Retrospective Cohort Study

Corynebacterium spp. are associated with respiratory infections in immunocompromised hosts. A link with bronchial complications after lung transplantation (LTx) has been suggested. We aimed to assess the link between respiratory sampling of Corynebacterium spp. and significant bronchial complication (SBC) after LTx. We performed a single center retrospective study. Inclusion of LTx recipients with at least one respiratory Corynebacterium spp. sample (July 2014 to December 2018). Subjects were matched to unexposed LTx recipients. Primary outcome was SBC occurrence after Corynebacterium spp. isolation. Secondary outcomes were Corynebacterium spp. persistent sampling, chronic lung allograft dysfunction (CLAD) onset and all-cause mortality. Fifty-nine patients with Corynebacterium spp. sampling with 59 without isolation were included. Corynebacterium spp. identification was not associated with SBC occurrence (32.4% vs. 21.6%, p = 0.342). Previous SBC was associated with further isolation of Corynebacterium spp. (OR 3.94, 95% CI [1.72-9.05]). Previous SBC and corticosteroids pulses in the last 3 months were the only factors associated with increased risk of Corynebacterium spp. isolation in multivariate analysis. Corynebacterium spp. sampling was significantly associated with CLAD onset (27.1% vs. 6.9%, p = 0.021). Corynebacterium spp. isolation was not associated with SBC but with higher risk of CLAD. Whether CLAD evolution is affected by Corynebacterium spp. eradication remains to be investigated.

The pan-genome of the emerging multidrug-resistant pathogen Corynebacterium striatum

Corynebacterium striatum, a common constituent of the human skin microbiome, is now considered an emerging multidrug-resistant pathogen of immunocompromised and chronically ill patients. However, little is known about the molecular mechanisms in the transition from colonization to the multidrug-resistant (MDR) invasive phenotype in clinical isolates. This study performed a comprehensive pan-genomic analysis of C. striatum, including isolates from "normal skin microbiome" and from MDR infections, to gain insights into genetic factors contributing to pathogenicity and multidrug resistance in this species. For this, three novel genome sequences were obtained from clinical isolates of C. striatum of patients from Brazil, and other 24 complete or draft C. striatum genomes were retrieved from GenBank, including the ATCC6940 isolate from the Human Microbiome Project. Analysis of C. striatum strains demonstrated the presence of an open pan-genome (α = 0.852803) containing 3816 gene families, including 15 antimicrobial resistance (AMR) genes and 32 putative virulence factors. The core and accessory genomes included 1297 and 1307 genes, respectively. The identified AMR genes are primarily associated with resistance to aminoglycosides and tetracyclines. Of these, 66.6% are present in genomic islands, and four AMR genes, including aac(6')-ib7, are located in a class 1-integron. In conclusion, our data indicated that C. striatum possesses genomic characteristics favorable to the invasive phenotype, with high genomic plasticity, a robust genetic arsenal for iron acquisition, and important virulence determinants and AMR genes present in mobile genetic elements.

Experience in the use of dalbavancin in diabetic foot infection

OBJECTIVE

To describe the clinical experience with dalbavancin in the treatment of diabetic foot infection in a multidisciplinary unit of a second level hospital.

METHODS

A retrospective, descriptive study was made with all patients with diabetic foot infection treated with dalbavancin in the Diabetic Foot Unit of Hospital Universitario Fundación Alcorcón, covering the period from September 2016 to December 2019. Demographic parameters and comorbidities, characteristics of the infection and treatment with dalbavancin were recorded. The cure rate is estimated at 90 days after finishing the treatment.

RESULTS

A total of 23 patients with diabetic foot infection (osteomyelitis) started treatment with dalbavancin, 19 were men and the mean age was 65 years. The microorganisms most frequently isolated for the indication of treatment with dalbavancin were Staphylococcus aureus (11) and Corynebacterium striatum (7). Dalbavancin was used as a second choice therapy in 22 cases, in 11 due to toxicity from other antibiotics. The median duration of treatment was 5 (4-7) weeks; the most frequent dose of dalbavancin (8 patients) was 1000 mg followed by 500 mg weekly for 5 weeks. 3 patients presented mild side effects (nausea and gastrointestinal discomfort). At 90 days after completion of dalbavancin therapy, 87% (20) of the patients were cured (95% CI: 65.2%-94.52%).

CONCLUSION

Patients with osteomyelitis due to gram-positive microorganisms who received as part of the multidisciplinary antibiotic treatment with dalbavancin, had a high rate of cure with adequate tolerance and few side effects. Dalbavancin offers a safe alternative in treating deep diabetic foot infection.

Corynebacterium striatum Bacteremia during SARS-CoV2 Infection: Case Report, Literature Review, and Clinical Considerations

Bacterial infections, especially those in hospital settings, represent a major complication of COVID-19 patients, complicating management and worsening clinical outcomes. Corynebacterium striatum is a non-diphtheric actinobacterium that has been reported as being the causative agent of several different infections, affecting both immunocompetent and immunocompromised patients. Recently, C. striatum has been recognized as a nosocomial pathogen that is responsible for severe infection in critical patients, as well as in fragile and immunocompromised subjects. C. striatum has been described as the etiological agent of bacteremia, central line infections, and endocarditis. We report a case of a 91-year-old woman who was hospitalized due to SARS-CoV-2 infection, who developed C. striatum bacteremia and died despite antimicrobial therapy and clinical efforts. Furthermore, we discuss C. striatum diagnosis and treatment based on evidence from the scientific literature.

Antibiotics Resistance in Escherichia coli Isolated from Livestock in the Emirate of Abu Dhabi, UAE, 2014–2019

Escherichia coli (E. coli) is a zoonotic pathogen that showed growing resistance to antibiotics. No descriptive analysis highlights the threat of antimicrobial-resistant (AMR) of E. coli among livestock in the United Arab Emirates (UAE). Herein, we conducted phenotypic and genotypic resistance studies on E. coli isolates from livestock samples in the Emirate of Abu Dhabi based on routine diagnosis between the periods 2014–2019. Bacterial culture and disk diffusion methods were used for bacterial isolation and phenotypic resistance analysis. Resistance mechanism was studied by PCR targeting the most commonly resistance genes: ampicillin (blaSHV, blaCMY, and blaTEM-1B), tetracyclines (tetA and tetB), co-trimoxazole [sulfamethoxazole (sul1, sul2, and sul3) + trimethoprim (dfrA1 and dfrA17)], aminoglycosides [aph(3'')-Ia, aph(6)-Id, and aac(3)-IV], and fluoroquinolones (qnrA and aac(6’)-Ib-cr). Analysis of 165 E. coli isolates showed resistant to ampicillin, tetracycline, co-trimoxazole, gentamicin, and enrofloxacin by 157/165 (95.4%), 154/165 (93.6%), 141/165 (86%), 139/165 (85%), and 135/165 (82.7%), respectively. Predominant resistance gene/s detected by PCR were blaCMY (119/160, 72%) and blaTEM-1B (154/160, 96.3%) for ampicillin; tetA (162/164, 98.8%) and tetB (112/164, 68.3%) for tetracyclines; sul2 (156/164, 95%), sul3 (138/164, 84%), and dfra17 (74/164, 44.5%) for co-trimoxazole; aph(3'')-Ia (134/164, 82.1%) and aph(6)-Id (161/164, 98.2%) for aminoglycosides; and aac(6’)-Ib-cr (61/61, 100%) for enrofloxacin. Both phenotypic and genotypic analyses revealed that all E. coli isolates were multidrug-resistant (resistance to 3, 4, and 5 antibiotics classes by 3.6%, 57.6%, and 38.8%, respectively) carrying one or more resistance gene/s for the same antibiotic. PCR profiling confirmed the presence of resistance genes corresponding to their antibiotic profile. Results of the study will highlight the knowledge based on E. coli AMR related to livestock in UAE that may call for interventions.

Profile of Bacteria with ARGs Among Real-World Samples from ICU Admission Patients with Pulmonary Infection Revealed by Metagenomic NGS

Background

Treatment of pulmonary infections in the intensive care unit (ICU) represents a great challenge, especially infections caused by antibiotic resistance pathogens. A thorough and up-to-date knowledge of the local spectrum of antibiotic resistant bacteria can improve the antibiotic treatment efficiency. In this study, we aimed to reveal the profile of bacteria with antibiotic resistance genes (ARGs) in real-world samples from ICU admission patients with pulmonary infection in Mainland, China, by metagenomic next-generation sequencing (mNGS).

Methods

A total of 504 different types of clinical samples from 452 ICU admission patients with pulmonary infection were detected by mNGS analysis.

Results

A total of 485 samples from 434 patients got successful mNGS results. Among 434 patients, one or more bacteria with ARGs were detected in 192 patients (44.24%, 192/434), and ≥2 bacteria with ARGs were detected in 85 (19.59%, 85/434) patients. The predominant detected bacteria were Corynebacterium striatum (C. striatum) (11.76%, 51/434), Acinetobacter baumannii (A. baumannii) (11.52%, 50/434) and Enterococcus faecium (E. faecium) (8.99%, 39/434). ermX conferred resistance to MSL_B and cmx to phenicol were the only two ARGs detected in C. striatum; in A. baumannii, most of ARGs were resistance-nodulation-division (RND)-type efflux pumps genes, which conferred resistance to multi-drug; ermB conferred resistance to MSL_B and efmA to multi-drug were the predominant ARGs in E. faecium. Bacteria with ARGs were detected in 50% (140/280) bronchoalveolar lavage fluid (BALF) and 50.5% (48/95) sputum samples, which were significantly higher than in blood and cerebrospinal fluid (CSF) samples.

Conclusion

High level of bacteria with ARGs was observed in clinical samples, especially BALF and sputum samples from ICU admission patients with pulmonary infection in Mainland, China. And C. striatum resistant to MSL_B and/or phenicol, multi-drug resistance A. baumannii and E. faecium were the lead bacteria.

Treat Me Well or Will Resist: Uptake of Mobile Genetic Elements Determine the Resistome of Corynebacterium striatum

Corynebacterium striatum, a bacterium that is part of the normal skin microbiota, is also an opportunistic pathogen. In recent years, reports of infections and in-hospital and nosocomial outbreaks caused by antimicrobial multidrug-resistant C. striatum strains have been increasing worldwide. However, there are no studies about the genomic determinants related to antimicrobial resistance in C. striatum. This review updates global information related to antimicrobial resistance found in C. striatum and highlights the essential genomic aspects in its persistence and dissemination. The resistome of C. striatum comprises chromosomal and acquired elements. Resistance to fluoroquinolones and daptomycin are due to mutations in chromosomal genes. Conversely, resistance to macrolides, tetracyclines, phenicols, beta-lactams, and aminoglycosides are associated with mobile genomic elements such as plasmids and transposons. The presence and diversity of insertion sequences suggest an essential role in the expression of antimicrobial resistance genes (ARGs) in genomic rearrangements and their potential to transfer these elements to other pathogens. The present study underlines that the resistome of C. striatum is dynamic; it is in evident expansion and could be acting as a reservoir for ARGs.

Clinical characteristics and drug susceptibility patterns of Corynebacterium species in bacteremic patients with hematological disorders

The aim of this study was to clarify the clinical and microbiological characteristics of Corynebacterium bacteremia in hematological patients. We retrospectively reviewed the medical records of patients with Corynebacterium bacteremia from April 2013 to June 2018. The causative Corynebacterium species were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Drug susceptibility tests were performed using the broth microdilution method recommended by the Clinical and Laboratory Standards Institute. In total, 147 cases of Corynebacterium bacteremia were identified during the study period. Corynebacterium striatum was the most frequent pathogen. Catheter-related bloodstream infection was diagnosed in 19.7% of all patients, and moderate/severe oral or severe gastrointestinal mucosal impairment was detected in 19.7%. Polymicrobial infection was found in about 20% of cases, with Enterococcus faecium being the most frequent isolate. The overall 30-day mortality was 34.7% (51/147). Multivariate analysis showed that E. faecium co-infection (odds ratio (OR) 9.3; 95% confidence interval (CI) 2.1-40), systemic corticosteroids (OR 3.6; 95% CI 1.4-8.9), other immunosuppressive drugs (OR 0.32; 95% CI 0.13-0.76), and a Pitt bacteremia score ≥4 (OR 12; 95% CI 3.9-40) were significant risk factors for overall 30-day mortality. The drug susceptibility rates for beta-lactam antimicrobial agents were quite low. All isolates were susceptible to glycopeptides and linezolid. However, some C. striatum isolates were resistant to daptomycin. Corynebacterium bacteremia can occur in the presence of several types of mucosal impairment. Our drug susceptibility data indicate that Corynebacterium bacteremia in hematological patients could be treated by glycopeptides or linezolid.

In Silico Prediction and Analysis of Unusual Lantibiotic Resistance Operons in the Genus Corynebacterium

Post-translationally modified, (methyl-)lanthionine-containing peptides are produced by several Gram-positive bacteria. These so-called lantibiotics have potent activity against various bacterial pathogens including multidrug-resistant strains and are thus discussed as alternatives to antibiotics. Several naturally occurring mechanisms of resistance against lantibiotics have been described for bacteria, including cell envelope modifications, ABC-transporters, lipoproteins and peptidases. Corynebacterium species are widespread in nature and comprise important pathogens, commensals as well as environmentally and biotechnologically relevant species. Yet, little is known about lantibiotic biosynthesis and resistance in this genus. Here, we present a comprehensive in silico prediction of lantibiotic resistance traits in this important group of Gram-positive bacteria. Our analyses suggest that enzymes for cell envelope modification, peptidases as well as ABC-transporters involved in peptide resistance are widely distributed in the genus. Based on our predictions, we analyzed the susceptibility of six Corynebacterium species to nisin and found that those without dedicated resistance traits are more susceptible and unable to adapt to higher concentrations. In addition, we were able to identify lantibiotic resistance operons encoding for peptidases, ABC-transporters and two-component systems with an unusual predicted structure that are conserved in the genus Corynebacterium. Heterologous expression shows that these operons indeed confer resistance to the lantibiotic nisin.

Worldwide survey of Corynebacterium striatum increasingly associated with human invasive infections, nosocomial outbreak, and antimicrobial multidrug-resistance, 1976-2020

Corynebacterium striatum is part of microbiota of skin and nasal mucosa of humans and has been increasingly reported as the etiologic agent of community-acquired and nosocomial diseases. Antimicrobial multidrug-resistant (MDR) C. striatum strains have been increasingly related to various nosocomial diseases and/or outbreaks worldwide, including fatal invasive infections in immunosuppressed and immunocompetent patients. Although cases of infections by C. striatum still neglected in some countries, the improvement of microbiological techniques and studies led to the increase of survival of patients with C. striatum nosocomial infections at different levels of magnitude. Biofilm formation on abiotic surfaces contributes for the persistence of virulent C. striatum and dissemination of antimicrobial resistance in hospital environment. Besides that, empirical antibiotic therapy can select multi-resistant strains and transfer intra and interspecies genes horizontally. In this study, a worldwide survey of C. striatum human infections and nosocomial outbreaks was accomplished by the analysis of clinical–epidemiological and microbiological features of reported cases from varied countries, during a 44-year period (1976–2020).

Medical Device Sterilization and Reprocessing in the Era of Multidrug-Resistant (MDR) Bacteria: Issues and Regulatory Concepts

The emergence of multidrug-resistant (MDR) bacteria threatens humans in various health sectors, including medical devices. Since formal classifications for medical device sterilization and disinfection were established in the 1970's, microbial adaptation under adverse environmental conditions has evolved rapidly. MDR microbial biofilms that adhere to medical devices and recurrently infect patients pose a significant threat in hospitals. Therefore, it is essential to mitigate the risk associated with MDR outbreaks by establishing novel recommendations for medical device sterilization, in a world of MDR. MDR pathogens typically thrive on devices with flexible accessories, which are easily contaminated with biofilms due to previous patient use and faulty sterilization or reprocessing procedures. To prevent danger to immunocompromised individuals, there is a need to regulate the classification of reprocessed medical device sterilization. This article aims to assess the risks of improper sterilization of medical devices in the era of MDR when sterilization procedures for critical medical devices are not followed to standard. Further, we discuss key regulatory recommendations for consistent sterilization of critical medical devices in contrast to the risks of disinfection reusable medical devices.

Experience in the use of dalbavancin in diabetic foot infection

OBJECTIVE

To describe the clinical experience with dalbavancin in the treatment of diabetic foot infection in a multidisciplinary unit of a second level hospital.

METHODS

A retrospective, descriptive study was made with all patients with diabetic foot infection treated with dalbavancin in the Diabetic Foot Unit of Hospital Universitario Fundación Alcorcón, covering the period from September 2016 to December 2019. Demographic parameters and comorbidities, characteristics of the infection and treatment with dalbavancin were recorded. The cure rate was estimated at 90 days after finishing the treatment.

RESULTS

A total of 23 patients with diabetic foot infection (osteomyelitis) started treatment with dalbavancin, 19 were men and the mean age was 65 years. The microorganisms most frequently isolated for the indication of treatment with dalbavancin were Staphylococcus aureus (11) and Corynebacterium striatum (7). Dalbavancin was used as a second choice therapy in 22 cases, in 11 due to toxicity from other antibiotics. The median duration of treatment was 5 (4-7) weeks; the most frequent dose of dalbavancin (8 patients) was 1000mg followed by 500mg weekly for 5 weeks. 3 patients presented mild side effects (nausea and gastrointestinal discomfort). At 90 days after completion of dalbavancin therapy, 87% (20) of the patients were cured (95% CI: 65.2%-94.52%).

CONCLUSION

Patients with osteomyelitis due to gram-positive microorganisms who received as part of the multidisciplinary antibiotic treatment with dalbavancin, had a high rate of cure with adequate tolerance and few side effects. Dalbavancin offers a safe alternative in treating deep diabetic foot infection.

Genomic epidemiology of Corynebacterium striatum from three regions of China: an emerging national nosocomial epidemic

BACKGROUND

Corynebacteritum straitum has been considered as an emerging multi-drug-resistant (MDR) pathogen. Isolation of MDR C. striatum as the only organism from respiratory samples from hospitalized patients is increasing in China.

AIM

To elucidate the genomic epidemiology and evolution of C. striatum in China.

METHODS

A total of 260 isolates from 2016 to 2018 were collected from three hospitals in three regions of China. Antibiotic sensitivity testing was performed on all isolates. Whole-genome sequencing was applied to all isolates to assess their genomic diversity and relationships and detect the presence of antimicrobial resistance genes (ARG) and ARG cassettes.

FINDINGS

Almost all isolates (96.2%, 250/260) showed multi-drug-resistance. Genome sequencing revealed four major lineages with lineage IV emerging as the epidemic lineage. Most of the diversity was developed in the last 6 years. Each hospital has its own predominant clones with potential spread between Hebei and Guangdong hospitals. Genomic analysis further revealed multiple antimicrobial resistance genes.

CONCLUSIONS

Our results suggested that four lineages of C. striatum have spread in parallel across China, causing persistent and extensive transmissions within hospitals. MDR C. striatum infection has become a national epidemic. Antibiotic-driven selection pressure may have played significant roles in forming persistent and predominant clones. Our data provide the basis for surveillance and prevention strategies to control the epidemic caused by MDR C. striatum.

Unveiling the biodiversity of lipid species in Corynebacteria- characterization of the uncommon lipid families in C. glutamicum and pathogen C. striatum by mass spectrometry

Uncommon lipids in biotechnologically important Corynebacterium glutamicum and pathogen Corynebacterium striatum in genus Corynebacterium are isolated and identified by linear ion-trap multiple stage mass spectrometry (LIT MSⁿ) with high resolution mass measurement. We redefined several lipid structures that were previously mis-assigned or not defined, including cytidine diphosphate diacylglycerol (CDP-DAG), glucuronosyl diacylglycerol (GlcA-DAG), (α-d-mannopyranosyl)-(1 → 4)-(α-D-glucuronyl diacyglycerol (Man-GlcA-DAG), 1-mycolyl-2-acyl-phosphatidylglycerol (MA-PG), acyl trehalose monomycolate (acyl-TMM). We also report the structures of mycolic acid, phosphatidylglycerol, phosphatidylinositol, cardiolipin, trehalose dimycolate lipids in which many isomeric structures are present. The LIT MSⁿ approaches afford identification of the functional group, the fatty acid substituents and their regiospecificity in the molecules, revealing the biodiversities of the lipid species in two Corynebacterium strains that have played very different and important roles in human nutrition and health.

Corynebacterium Total Hip and Knee Arthroplasy Prosthetic Joint Infections

Prosthetic joint infections (PJIs) are typically caused by Staphylococcus aureus and coagulase-negative Staphylococci species. Corynebacterium species are microorganisms of the human skin and mucous membranes that are often considered contaminants when grown in culture. In the past, Corynebacterium species were often classified as diphtheroids based on growing as gram-positive rods in aerobic environments, but with advances in technology, the identification of Corynebacterium species has improved. Corynebacterium can cause infection, but there are few case reports of orthopaedic infection. We present 3 cases of total hip arthroplasty and 3 cases of total knee arthroplasty PJI caused by Corynebacterium species. We found a high failure rate of surgical treatment of Corynebacterium PJI, defined as reoperation for infection. This information adds to the limited literature on these organisms in total joint arthroplasty PJI.

Whole-Genome Sequencing Reveals a Prolonged and Persistent Intrahospital Transmission of Corynebacterium striatum, an Emerging Multidrug-Resistant Pathogen

Corynebacterium striatum is an emerging multidrug-resistant (MDR) pathogen that occurs primarily among immunocompromised and chronically ill patients. However, little is known about the genomic diversity of C. striatum, which contributes to its long-term persistence and transmission in hospitals. In this study, a total of 192 C. striatum isolates obtained from 14 September 2017 to 29 March 2018 in a hospital in Beijing, China, were analyzed by antimicrobial susceptibility testing and pulsed-field gel electrophoresis (PFGE). Whole-genome sequencing was conducted on 91 isolates. Nearly all isolates (96.3%, 183/190) were MDR. The highest resistance rate was observed for ciprofloxacin (99.0%, 190/192), followed by cefotaxime (90.6%, 174/192) and erythromycin (89.1%, 171/192). PFGE separated the 192 isolates into 79 pulsotypes, and differences in core genome single-nucleotide polymorphisms (SNPs) partitioned the 91 isolates sequenced into four clades. Isolates of the same pulsotype were identical or nearly identical at the genome level, with some exceptions. Two dominant subclones, clade 3a, and clade 4a, were responsible for the hospital-wide dissemination. Genomic analysis further revealed nine resistance genes mobilized by eight unique cassettes. PFGE and whole-genome sequencing revealed that the C. striatum isolates studied were the result mainly of predominant clones spreading in the hospital. C. striatum isolates in the hospital progressively acquired resistance to antimicrobial agents, demonstrating that isolates of C. striatum may adapt rapidly through the acquisition and accumulation of resistance genes and thus evolve into dominant and persistent clones. These insights will be useful for the prevention of C. striatum infection in hospitals.

Bloodstream and catheter-related infections due to different clones of multidrug-resistant and biofilm producer Corynebacterium striatum

BACKGROUND

Corynebacterium striatum is an emerging multidrug-resistant (MDR) pathogen associated with immunocompromised and chronically ill patients, as well as nosocomial outbreaks. In this study, we characterized 23 MDR C. striatum isolated of bloodstream and catheter-related infections from a hospital of Rio de Janeiro.

METHODS

C. striatum isolates were identified by 16S rRNA and rpoB genes sequencing. The dissemination of these isolates was accomplished by pulsed-field gel electrophoresis (PFGE). All isolates were submitted to antimicrobial susceptibility testing by disk diffusion and by minimum inhibitory concentration using E-test strips methods. Antimicrobial resistance genes were detected by polymerase chain reaction. Quantitative tests were performed on four different abiotic surfaces and the ability to produce biofilm on the surface of polyurethane and silicone catheter was also demonstrated by scanning electron microscopy.

RESULTS

Eleven PFGE profiles were found. The PFGE profile I was the most frequently observed among isolates. Five different MDR profiles were found and all PFGE profile I isolates presented susceptibility only to tetracycline, vancomycin, linezolid and daptomycin. Only the multidrug-susceptible isolate did not show mutations in the quinolone-resistance determinant region (QRDR) of the gyrA gene and was negative in the search of genes encoding antibiotic resistance. The other 22 isolates were positive to resistance genes to aminoglycoside, macrolides/lincosamides and chloramphenicol and showed mutations in the QRDR of the gyrA gene. Scanning electron microscopy illustrated the ability of MDR blood isolate partaker of the epidemic clone (PFGE profile I) to produce mature biofilm on the surface of polyurethane and silicone catheter.

CONCLUSIONS

Genotyping analysis by PFGE revealed the permanence of the MDR PFGE profile I in the nosocomial environment. Other new PFGE profiles emerged as etiologic agents of invasive infections. However, the MDR PFGE profile I was also found predominant among patients with hematogenic infections. The high level of multidrug resistance associated with biofilm formation capacity observed in MDR C. striatum is a case of concern.

A novel isothermal amplification-based method for detection of Corynebacterium striatum

Corynebacterium striatum is an emerging multidrug-resistant pathogen causing increasing numbers of infections and nosocomial outbreaks worldwide. Thus, a simple, rapid and accurate method for C. striatum is urgently required for improving diagnosis efficiency. In this study, a C. striatum-multiple cross displacement amplification (MCDA) with visual detection reagent (VR) assay (C. striatum-MCDA-VR), which was a novel isothermal amplification-based method, was established to detect the species-specific ftr1 gene of C. striatum. Amplification was performed at a constant temperature (68 °C) for only 40 min, and the reaction results could be easily elucidated by observation of reaction mixture color when employing the VR. The limit of detection of this method was 10 fg of pure C. striatum DNA. No cross-reaction was observed with non-C. striatum strains. In testing of clinical sputum samples, the C. striatum-MCDA-VR assay showed excellent sensitivity and specificity when compared with sputum smear tests and PCR. The C. striatum-MCDA-VR assay is a simple, rapid and cost-effective approach for identifying C. striatum in microbiological laboratories, especially in resource-limited settings.

New Gene Responsible for Resistance of Clinical Corynebacteria to Macrolide, Lincosamide and Streptogramin B

The subject of the study was phenotypic marking of the antibiotic susceptibility and MLS_B resistance mechanism in Corynebacterium spp. isolated from human skin (18 isolates) and from clinical materials (19 isolates). The strains were tested for the presence of the erm(A), erm(B), erm(C), erm(X), lnu(A), msr(A), msr(B) and mph(C) genes. Clinical isolates showed wide resistance to antibiotics. In 89% clinical isolates and 72% skin microbiota a constitutive type of MLS_B resistance was found. In 12 clinical isolates the erm(C) gene was detected-eight of which had erm(X) as well as erm(C), two harboured erm(X), erm(C) and erm(A) and two demonstrated only erm(C).

A life-threatening infection due to Corynebacterium striatum: a lesson learned

Because the genus Corynebacterium colonize the human skin, detection of Corynebacterium striatum in a sterile blood specimen is sometimes considered as contamination. An 80-year-old man who underwent cardiovascular operation presented with high-grade fever postoperatively. Corynebacterium striatum was detected in the blood and wound exudate, and the patient was diagnosed with mediastinitis due to Corynebacterium striatum. One month earlier, a patient with similar symptoms due to C. striatum-related mediastinitis died in our care. The Corynebacterium striatum isolates from both patients had identical biochemical and genetic characteristics, suggesting that Corynebacterium striatum was acquired nosocomially. We have learnt a lesson from this negative experience: early diagnosis of Corynebacterium striatum-related infection and early administration of glycopeptide antibiotics could have saved this patient. It is notable that C. striatum can cause life-threatening infection after cardiovascular operation.

Molecular epidemiology and clinical significance of Corynebacterium striatum isolated from clinical specimens

Purpose

This study investigated the clinical epidemiology, antimicrobial susceptibility, and molecular epidemiology of Corynebacterium striatum isolates.

Patients and methods

An observational study was conducted at a university hospital in the Republic of Korea from August to December 2016. All subjects were patients who tested positive for C. striatum clinically. Clinical data were analyzed to evaluate the microbiological and genotypic characteristics of C. striatum strains.

Results

Sixty-seven C. striatum isolates recovered from non-duplicated patients were characterized. Patients were classified into three groups according to the infection type: nosocomial infection (71.6%), health care-associated infection (8.7%), and community-acquired infection (18.8%). The most common clinical specimens were urine (35.8%) and skin abscesses (32.8%). Fifty-two (77.6%) isolates showed multidrug resistance, defined as resistance to ≥3 different antibiotic families. All strains were susceptible to vancomycin and linezolid. Resistance to other antibiotics varied: penicillin (n=65; 97.0%), ampicillin (n=63; 94.0%), cefotaxime (n=64; 95.5%), and levofloxacin (n=61; 91.0%). Phylogenetic analysis identified all 16 S rRNA gene sequences of the 67 isolates as those of C. striatum, where 98%–99% were homologous to C. striatum ATCC 6940. In multilocus sequence typing for internal transcribed spacer region, gyrA, and rpoB sequencing, the most predominant sequence types (STs) were ST2, ST3, ST6, and ST5.

Conclusion

C. striatum isolates may cause opportunistic infections associated with nosocomial infections through horizontal transmission. The presence of multidrug resistance and intra-hospital dissemination implicate C. striatum isolates as a potential target pathogen for infection control and antimicrobial stewardship programs.

Comparison between disk diffusion and agar dilution methods to determine in vitro susceptibility of Corynebacterium spp. clinical isolates and update of their susceptibility

OBJECTIVES

Although Corynebacterium spp. are part of the microbiota of the skin and mucous membranes, human infections caused by Corynebacterium spp. have been reported and the multidrug resistance pattern of the recovered isolates was emphasised. Due to the usefulness of disk diffusion in daily practice, the purpose of this study was to compare disk diffusion with agar dilution to determine disk diffusion breakpoints and to review the antimicrobial susceptibility of the most frequent Corynebacterium spp. isolated in clinical samples.

METHODS

Susceptibility to 20 antimicrobial agents of 143 Corynebacterium spp. isolates recovered from relevant clinical samples was determined. Comparison between the disk diffusion and agar dilution methods for eight antimicrobial agents was performed to establish new breakpoints using simple linear regression analysis.

RESULTS

All of the isolates tested were susceptible to vancomycin, minocycline and linezolid. A typical susceptibility profile to β-lactam antibiotics among the different species included was not observed. Almost all isolates showed resistance to macrolides and lincosamides. Using a simple linear regression method, it was possible to establish breakpoints for penicillin, erythromycin, clindamycin, gentamicin and ciprofloxacin. However, the low correlation coefficient obtained for vancomycin, minocycline and trimethoprim/sulfamethoxazole did not allow establishment of breakpoints for the disk diffusion method.

CONCLUSION

The disk diffusion method could only be used to evaluate susceptibility to penicillin, erythromycin, clindamycin, gentamicin and ciprofloxacin. These data show that the presence of a Corynebacterium spp. isolate in a clinical sample demands the performance of antimicrobial susceptibility testing since the susceptibility profile is not predictable.

Multidrug-Resistant Corynebacterium striatum Associated with Increased Use of Parenteral Antimicrobial Drugs

Device-related infections with this pathogen frequently require prolonged parenteral therapy.

Corynebacterium striatum is an emerging multidrug-resistant bacteria. We retrospectively identified 179 isolates in a clinical database. Clinical relevance, in vitro susceptibility, and length of parenteral antimicrobial drug use were obtained from patient records. For patients with hardware- or device-associated infections, those with C. striatum infections were matched with patients infected with coagulase-negative staphylococci for case–control analysis. A total of 87 (71%) of 121 isolates were resistant to all oral antimicrobial drugs tested, including penicillin, tetracycline, clindamycin, erythromycin, and ciprofloxacin. When isolated from hardware or devices, C. striatum was pathogenic in 38 (87%) of 44 cases. Patients with hardware-associated C. striatum infections received parenteral antimicrobial drugs longer than patients with hardware-associated coagulase-negative staphylococci infections (mean ± SD 69 ± 5 days vs. 25 ± 4 days; p<0.001). C. striatum commonly shows resistance to antimicrobial drugs with oral bioavailability and is associated with increased use of parenteral antimicrobial drugs.

Retrospective evaluation of the clinical characteristics associated with Corynebacterium species bacteremia

Objectives

Corynebacterium spp. are becoming recognized as pathogens that potentially cause various infections. We aimed to evaluate the clinical characteristics associated with Corynebacterium spp. bacteremia.

Patients and methods

We retrospectively reviewed the medical records of all adult patients who had positive blood cultures for Corynebacterium spp. in a single university hospital between January 2014 and December 2016. Patients were divided into a bacteremia group and a contamination group based on microbiological test results and clinical characteristics. Patients’ characteristics, antimicrobial susceptibility of isolated species, antimicrobials administered, and patient outcomes were evaluated.

Results

Corynebacterium spp. were isolated from blood samples of 63 patients; Corynebacterium striatum was the predominant isolate. Twenty-eight patients were determined to have bacteremia. Younger age (p = 0.023), shorter time to positivity (p = 0.006), longer hospital stay (p = 0.009), and presence of an indwelling vascular catheter (p = 0.002) were observed more often in the bacteremia group compared to the contamination group. The source of infection in most patients with bacteremia was an intravenous catheter. All tested strains were susceptible to vancomycin. Four of the 27 patients with bacteremia died, despite administration of appropriate antimicrobial therapy.

Conclusions

We found that younger age, shorter time to positivity, and presence of an indwelling catheter were related to bacteremia caused by Corynebacterium spp. Appropriate antimicrobials should be administered once Corynebacterium spp. are isolated from the blood and bacteremia is suspected.

Genomics of Corynebacterium striatum, an emerging multidrug-resistant pathogen of immunocompromised patients

OBJECTIVES

Corynebacterium striatum is an emerging multidrug-resistant (MDR) pathogen of immunocompromised and chronically ill patients. The objective of these studies was to provide a detailed genomic analysis of disease-causing C. striatum and determine the genomic drivers of resistance and resistance-gene transmission.

METHODS

A multi-institutional and prospective pathogen genomics programme flagged seven MDR C. striatum infections occurring close in time, and specifically in immunocompromised patients with underlying respiratory diseases. Whole genome sequencing was used to identify clonal relationships among strains, genetic causes of antimicrobial resistance, and their mobilization capacity. Matrix-assisted linear desorption/ionization-time-of-flight analyses of sequenced isolates provided curated content to improve rapid clinical identification in subsequent cases.

RESULTS

Epidemiological and genomic analyses identified a related cluster of three out of seven C. striatum among lung transplant patients who had common procedures and exposures at an outlying institution. Genomic analyses further elucidated drivers of the MDR phenotypes, including resistance genes mobilized by IS3504 and ISCg9a-like insertion sequences. Seven mobilizable resistance genes were localized to a common chromosomal region bounded by unpaired insertion sequences, suggesting that a single recombination event could spread resistance to aminoglycosides, macrolides, lincosamides and tetracyclines to naive strains.

CONCLUSION

In-depth genomic studies of MDR C. striatum reveal its capacity for clonal spread within and across healthcare institutions and identify novel vectors that can mobilize multiple forms of drug resistance, further complicating efforts to treat infections in immunocompromised populations.

Occurrence of Corynebacterium striatum as an emerging antibiotic-resistant nosocomial pathogen in a Tunisian hospital

Corynebacterium striatum is a nosocomial opportunistic pathogen increasingly associated with a wide range of human infections and is often resistant to several antibiotics. We investigated the susceptibility of 63 C. striatum isolated at the Farhat-Hached hospital, Sousse (Tunisia), during the period 2011–2014, to a panel of 16 compounds belonging to the main clinically relevant classes of antimicrobial agents. All strains were susceptible to vancomycin, linezolid, and daptomycin. Amikacin and gentamicin also showed good activity (MICs₉₀ = 1 and 2 mg/L, respectively). High rates of resistance to penicillin (82.5%), clindamycin (79.4%), cefotaxime (60.3%), erythromycin (47.6%), ciprofloxacin (36.5%), moxifloxacin (34.9%), and rifampicin (25.4%) were observed. Fifty-nine (93.7%) out of the 63 isolates showed resistance to at least one compound and 31 (49.2%) were multidrug-resistant. Twenty-nine resistance profiles were distinguished among the 59 resistant C. striatum. Most of the strains resistant to fluoroquinolones showed a double mutation leading to an amino acid change in positions 87 and 91 in the quinolone resistance-determining region of the gyrA gene. The 52 strains resistant to penicillin were positive for the gene bla, encoding a class A β-lactamase. Twenty-two PFGE patterns were identified among the 63 C. striatum, indicating that some clones have spread within the hospital.

Skin and Soft Tissue Infections

The skin is colonized by a diverse collection of microorganisms which, for the most part, peacefully coexist with their hosts. Skin and soft tissue infections (SSTIs) encompass a variety of conditions; in immunocompromised hosts, SSTIs can be caused by diverse microorganisms-most commonly bacteria, but also fungi, viruses, mycobacteria, and protozoa. The diagnosis of SSTIs is difficult because they may commonly masquerade as other clinical syndromes or can be a manifestation of systemic disease. In immunocompromised hosts, SSTI poses a major diagnostic challenge, and clinical dermatological assessment should be initially performed; to better identify the pathogen and to lead to appropriate treatment, etiology should include cultures of lesions and blood, biopsy with histology, specific microbiological analysis with special stains, molecular techniques, and antigen-detection methodologies. Here, we reviewed the epidemiology, pathophysiology, clinical presentation, and diagnostic techniques, including molecular biological techniques, used for SSTIs, with a focus on the immunocompromised host, such as patients with cellular immunodeficiency, HIV, and diabetic foot infection.

Ceftaroline Plus Ampicillin Against Gram-Positive Organisms: Results from E-Test Synergy Assays

In an era of increasing drug resistance and limited numbers of antimicrobials in the drug production pipeline, healthcare-associated infections represent a growing public health threat. When therapeutic options are limited, clinicians often resort to using antimicrobial combinations that produce a synergistic effect on the target pathogen. Novel antibiotics are therefore welcome in the daily practice of medicine. For example, ceftaroline is a broad-spectrum cephalosporin active against a variety of bacteria, including methicillin-resistant Staphylococcus aureus, but with limited activity against enterococci, particularly Enterococcus faecium. In this study, we tested the efficacy of ceftaroline against clinical isolates of gram-positive bacteria (S. aureus, Enterococcus faecalis, and E. faecium) by the broth microdilution and E-test assays, and then evaluated the synergistic effect of ceftaroline and ampicillin using the E-test method. The time-kill assay was used to confirm the data on selected strains. This drug combination has been recently shown to be effective against E. faecalis and could offer the advantage of cost-effectiveness (compared to other synergistic associations) as well as good tolerability. The E-test was chosen because of its relative simplicity of use that makes it suitable for routine clinical laboratories as a quick tool to guide clinicians when confronted with difficult-to-treat infections that may require an empirical approach. Our results indicate the presence of a synergistic effect of ceftaroline and ampicillin on most of the strains used, especially E. faecium and E. faecalis. The fact that two of those Enterococcus strains were vancomycin resistant suggests that the possible use of this combination for combating the spread of vancomycin-resistant enterococci should be explored.

Corynebacterium striatum Bacteremia Associated with a Catheter-Related Blood Stream Infection

A 49-year-old woman visited our emergency department because of exertional dyspnea due to severe left ventricular functional failure. It progressed to disseminated intravascular coagulation and disturbance of consciousness on day 67 of admission. Gram-positive bacilli were detected from two different blood culture samples on day 67 of admission. An API-Coryne test and sequencing (1~615 bp) of the 16S rRNA gene were performed, and the strain was identified as Corynebacterium striatum. The bacterium was detected from the removed central venous catheter tip too, and the patient was diagnosed with catheter-related bloodstream infection by C. striatum. However, treatment was not effective, and the patient died on day 73 of admission.

Clinical characteristics and predictive factors for mortality in coryneform bacteria bloodstream infection in hematological patients

BACKGROUND

We examined the clinical characteristics and predictive factors for mortality in coryneform bacteria bloodstream infection in hematological patients.

METHODS

We searched for hematological patients who had positive blood cultures for coryneform bacteria at our center between April 2007 and January 2016. Patients with definite bloodstream infections were included. We started species identification in April 2014.

RESULTS

Twenty of twenty-eight cases with a positive blood culture for coryneform bacteria were regarded as definite infections. Sixteen and two patients were allogeneic and autologous hematopoietic stem cell transplantation (HSCT) recipients, respectively. Corynebacterium striatum was identified in all nine of the cases tested and one patient was co-infected with Corynebacterium amycolatum. None of the patients died directly due to coryneform bacteria infection. The survival rates at 30, 60 and 180 days were 100%, 73.7% and 51.3%, respectively. Causes of mortality included progression of the underlying disease (n = 6), other infections (n = 4) and HSCT complications (n = 2). Mixed infection (hazard ratio (HR) 5.47, 95% confidence interval (CI) 1.30-23.0), renal impairment (HR 6.31, 95% CI 1.06-37.4) and absence of a central venous (CV) catheter at the onset (HR 6.39, 95% CI 1.04-39.45) were identified as predictive factors for mortality.

CONCLUSION

Most of the coryneform bacteria bloodstream infections occurred in HSCT recipients. Contamination seemed to be less common when coryneform bacteria were detected in blood in hematological patients. Although coryneform bacteria bloodstream infection seemed to mostly be manageable, the prognosis was not desirable, particularly in patients with mixed infection, renal impairment and absence of a CV catheter.

Susceptibility to Aminoglycosides and Distribution of aph and aac(3)-XI Genes among Corynebacterium striatum Clinical Isolates

Corynebacterium striatum is an opportunistic pathogen, often multidrug-resistant, which has been associated with serious infections in humans. Aminoglycosides are second-line or complementary antibiotics used for the treatment of Corynebacterium infections. We investigated the susceptibility to six aminoglycosides and the molecular mechanisms involved in aminoglycoside resistance in a collection of 64 Corynebacterium striatum isolated in our laboratory during the period 2005–2009. Antimicrobial susceptibility was determined using E-test. The mechanisms of aminoglycoside resistance were investigated by PCR and sequencing. The 64 C. striatum were assessed for the possibility of clonal spreading by Pulsed-field Gel Electrophoresis (PFGE). Netilmicin and amikacin were active against the 64 C. striatum isolates (MICs₉₀ = 0.38 and 0.5 mg/L, respectively). Twenty-seven of the 64 C. striatum strains showed a MIC₉₀ for kanamycin > 256 mg/L, and 26 out the 27 were positive for the aph(3’)-Ic gene. Thirty-six out of our 64 C. striatum were streptomycin resistant, and 23 out of the 36 carried both the aph(3”)-Ib and aph(6)-Id genes. The gene aac(3)-XI encoding a new aminoglycoside 3-N acetyl transferase from C. striatum was present in 44 out of the 64 isolates, all of them showing MICs of gentamicin and tobramycin > 1 mg/L. CS4933, a C. striatum showing very low susceptibility to kanamycin and streptomycin, contains an aminoglycoside resistance region that includes the aph(3’)-Ic gene, and the tandem of genes aph(3”)-Ib and aph(6)-Id. Forty-six major PFGE types were identified among the 64 C. striatum isolates, indicating that they were mainly not clonal. Our results showed that the 64 clinical C. striatum were highly resistant to aminoglycosides and mostly unrelated.

Rare case of Corynebacterium striatum septic arthritis

Corynebacterium species are aerobic, Gram-positive bacilli that are commensal organisms of skin and mucosal membranes. Although its pathogenicity is well established, Corynebacterium striatum is frequently isolated in cultures and generally regarded as a contaminant. Rarely, this bacterium causes septic arthritis. We present a case of right shoulder joint septic arthritis due to C. striatum in a lung-transplant recipient with end-stage renal disease. A brief review of the literature regarding C. striatum septic arthritis is also a part of this report.

Clinical and bacteriological analyses of bacteremia due to Corynebacterium striatum

BACKGROUND

Corynebacterium striatum was recently recognized as a potential pathogen of various infectious diseases. However, the clinical entity of this microorganism has not been clearly identified. Therefore, we analyzed C. striatum isolates from blood culture and explored their clinical determinants.

METHODS

We reviewed the medical records of all patients from whom C. striatum isolates were recovered from blood culture for analysis of the patients' backgrounds and clinical course including response to antimicrobial therapy and prognosis.

RESULTS

During the 5-year study period (January 2010 to December 2014), 24 C. striatum strains were isolated from blood samples, and the frequency of C. striatum bacteremia increased. The majority of the strains were multidrug resistant. All of the tested strains were susceptible to only vancomycin. The age at onset of C. striatum bacteremia encompassed all adult age groups, and at least one underlying condition was documented in all patients. Thirteen of the 24 patients were cured using appropriate antibiotics (true infection group); however, 11 of the 24 patients were cured using inappropriate antibiotic therapy or no antibiotics (contamination group). Malignancy and neutropenia significantly increased the odds of true C. striatum bloodstream infection.

CONCLUSIONS

The Corynebacterium species is often considered a contaminant when isolated in culture. Instead, particularly when the strain is isolated from blood, the species should be considered clinically relevant and identified to the species level; in addition, antimicrobial susceptibility testing is recommended.

Clinical Significance of Commensal Gram-Positive Rods Routinely Isolated from Patient Samples

Commensal bacteria from the skin and mucosal surfaces are routinely isolated from patient samples and considered contaminants. The majority of these isolates are catalase-positive Gram-positive rods from multiple genera routinely classified as diphtheroids. These organisms can be seen upon Gram staining of clinical specimens or can be isolated as the predominant or pure species in culture, raising a priori suspicion of a possible involvement in infection. With the development and adoption of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), suspicious isolates are now routinely identified to the species level. In this study, we performed a retrospective data review (2012 to 2015) and utilized site-specific laboratory criteria and chart reviews to identify species within the diphtheroid classification representative of true infection versus contamination. Our data set included 762 isolates from 13 genera constituting 41 bacterial species. Only 18% represented true infection, and 82% were deemed contaminants. Clinically significant isolates were identified in anaerobic wounds (18%), aerobic wounds (30%), blood (5.5%), urine (22%), cerebrospinal fluid (24%), ophthalmologic cultures (8%), and sterile sites (20%). Organisms deemed clinically significant included multiple Actinomyces species in wounds, Propionibacterium species in joints and cerebrospinal fluid associated with central nervous system hardware, Corynebacterium kroppenstedtii (100%) in breast, and Corynebacterium striatum in multiple sites. Novel findings include clinically significant urinary tract infections by Actinomyces neuii (21%) and Corynebacterium aurimucosum (21%). Taken together, these findings indicate that species-level identification of diphtheroids isolated with a priori suspicion of infection is essential to accurately determine whether an isolate belongs to a species associated with specific types of infection.

Characteristics of Multidrug-Resistant Corynebacterium spp. Isolated from Blood Cultures of Hospitalized Patients in Japan

Corynebacterium is a genus consisting of Gram-positive, rod-shaped bacteria, that is wildly distributed in nature. We report the epidemiological characterization of Corynebacterium spp. isolated from blood specimens at the Kurume University Hospital, between June 2008 and November 2011. Twenty-two strains that were likely Corynebacterium spp. were isolated from 22 hospitalized patients, of which 12 (54.5%) were identified as Corynebacterium striatum. Minimum inhibitory concentration tests were performed after biochemical and genotypic identifications. Biofilm production was detected using a 96-well microplate assay. The dissemination of C. striatum was investigated using pulsed-field gel electrophoresis (PFGE). All strains showed the tendency to be resistant to multiple drugs except vancomycin. Fourteen (82.4%) strains, including 9 C. striatum strains were capable of producing biofilms. Four distinct PFGE patterns were detected among C. striatum strains; 6 of which were identified as dominant pattern A (defined in this study) and had high biofilm production ability. During the 3-year monitoring period, these strains might have repeatedly infected the patients or could have readily colonized the hospital environments. C. striatum appeared to be a potential risk factor for bloodstream infections in hospitalized patients. More surveillance and enhanced control strategies are necessary to decrease Corynebacterium spp. infections in hospitals.

Emergence of High-Level Daptomycin Resistance in Corynebacterium striatum in Two Patients with Left Ventricular Assist Device Infections

INTRODUCTION

We describe the clinical and microbiologic courses of two patients with ventricular assist device infections secondary to Corynebacterium striatum treated with daptomycin. In both cases, the pathogen was initially susceptible to daptomycin (minimum inhibitory concentration [MIC] <0.125 mg/L) but became resistant (MIC >256 mg/L) during therapy.

METHODS

The clonal nature of the isolates was determined by pulse-field gel electrophoresis (PFGE). Daptomycin binding was assessed by fluorescence microscopy using daptomycin-boron-dipyrromethene (bodipy). Induction and stability of daptomycin resistance were assessed by culturing strains in the presence of low concentrations of daptomycin or passage of resistant strains on daptomycin-free medium and repeat MIC testing, respectively.

RESULTS

PFGE revealed that resistant clinical isolates were genetically indistinguishable from their parent strains, but the two pairs were unrelated to each other. The resistant strains had 7.5-15 times lower binding of daptomycin-bodipy compared to the related susceptible strains (p ≤ 0.0002). High-level daptomycin resistance (MIC >256 mg/L) was generated in vitro for both susceptible parent strains after overnight culture in the presence of daptomycin. One of the resistant strains maintained a high-level resistance phenotype up to 5 days of passage on daptomycin-free medium, whereas the other strain reverted back to a susceptible phenotype (MIC = 0.38 mg/L) after one passage on daptomycin-free medium, with a concomitant increase in daptomycin binding.

CONCLUSIONS

High-level daptomycin resistance in C. striatum was readily generated in vitro and during the course of therapy in these patients. This resistance appears to be mediated by reduced daptomycin binding. Providers should be cautious about using long-term daptomycin monotherapy for C. striatum infections.

Biofilm production by multiresistant Corynebacterium striatum associated with nosocomial outbreak

Corynebacterium striatum is a potentially pathogenic microorganism that causes nosocomial outbreaks. However, little is known about its virulence factors that may contribute to healthcare-associated infections (HAIs). We investigated the biofilm production on abiotic surfaces of multidrug-resistant (MDR) and multidrug-susceptible (MDS) strains of C. striatum of pulsed-field gel electrophoresis types I-MDR, II-MDR, III-MDS and IV-MDS isolated during a nosocomial outbreak in Rio de Janeiro, Brazil. The results showed that C. striatum was able to adhere to hydrophilic and hydrophobic abiotic surfaces. The C. striatum 1987/I-MDR strain, predominantly isolated from patients undergoing endotracheal intubation procedures, showed the greatest ability to adhere to all surfaces. C. striatum bound fibrinogen to its surface, which contributed to biofilm formation. Scanning electron microscopy showed the production of mature biofilms on polyurethane catheters by all pulsotypes. In conclusion, biofilm production may contribute to the establishment of HAIs caused by C. striatum.

Postoperative Abdominal Infection Caused by Corynebacterium minutissimum

Corynebacterium minutissimum is a non-spore forming, gram-positive, aerobic or facultative anaerobic bacillus. It is the causative organism of erythrasma, a common superficial infection of skin, which typically presents as reddish-brown macular patches. To date, it has rarely been found to cause invasive disease, although other non-diphtheria corynebacteria are becoming increasingly common as opportunistic pathogens. We report on a rare case of abdominal infection due to C. minutissimum in an immunocompetent adult who was successfully treated with intravenous amoxicillin/sulbactam.

Respiratory infection by Corynebacterium striatum: epidemiological and clinical determinants

The increasing prevalence of advanced chronic respiratory disease, with frequent exposure to broad-spectrum antibiotics for repeated and prolonged hospitalizations, favours the emergence of nosocomial respiratory infection by Gram-positive bacteria, such as outbreaks of Corynebacterium striatum. There is little evidence about patterns of respiratory infection, transmission and adaptive ability of this pathogen. Seventy-two C. striatum isolates from 51 advanced respiratory patients, mainly chronic obstructive pulmonary disease, were studied during 38 months. Patients were 74.8 ± 8.6 years old and 81.9% were men, who had required an average of 2.2 hospitalizations and 63.5 days in the hospital in the previous year. Of 49 isolates from 42 patients we were able to identify 12 clones by multilocus sequence analysis (MLSA), nine phenotypic variants and 22 antibiotic susceptibility patterns, and we determined their clinical and epidemiological determinants. MLSA allows identification of the existence of nosocomial outbreaks by transmission of the same or different clones, the persistence of the same clone in the environment or in patient airways for months. The study showed the high variability and adaptive capacity of the isolates, the antibiotic multidrug-resistance in all of them, and their contribution to a high morbidity and mortality (41%) during the study period.

Antibiotic resistance and detection of the most common mechanism of resistance (MLSB) of opportunistic Corynebacterium

BACKGROUND

Determination of antibiotic resistance of opportunistic Corynebacterium colonizing the nose that cause infections and evaluation of the applicability of a simple method for detecting the most common constitutive-type resistance to macrolides, lincosamides and streptogramin B (MLSB).

METHODS

70 isolates colonizing the nose and 70 clinical isolates of various infection sites were used and identified using APICoryne and 16S rRNA. Minimal inhibitory concentrations (MICs) were determined (Etest) for 12 antibiotics. MLSB was defined based on MIC, a simple method using two disks (erythromycin/clindamycin) and detection of the gene erm X (PCR).

RESULTS

There was a high percentage--in both groups at the same level--of strains with MLSB (88.5% colonizing the nose and 87.1% causing infections). Detection with the phenotypic method MLSB was confirmed genetically (erm X) in all cases. In both groups, a high percentage of resistance was found to trimethoprim/sulfamethoxazole (in both groups 71.4%), chloramphenicol (nose 44.2%/infections 37.1%), tetracycline (28 and 45.7%) and β-lactam antibiotics (18.5 and up to 32.8%).

CONCLUSION

Differences in antibiotic resistance were found between strains colonizing the respiratory tract and various infections. Isolates from infections more frequently exhibited multidrug resistance. The possibility of using a simple method was confirmed for MLSB detection, which can be applied to determine drug resistance in routine microbiological diagnostics of infections caused by opportunistic Corynebacterium.