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

[Risk factors associated with osteomyelitis due to Corynebacterium striatum in patients with diabetic foot]

OBJECTIVE

Corynebacterium striatum (CS) is an emerging micro-organism in diabetic foot infection for which there are currently few studies. The objective was to analyze the risk factors (RF) related to CS osteomyelitis in patients with diabetic foot.

METHODS

A case-control study was conducted in the Diabetic Foot Unit between 2015 and 2021. Forty-four patients with osteomyelitis due to CS (cases) and 44 patients with osteomyelitis due a different micro-organism (controls) were included.

RESULTS

Peripheral artery disease (OR: 2.8, p = 0.037), atrial fibrillation (OR: 3.7, p = 0.034), ischemic diabetic foot (OR: 3.3, p = 0.020) and previous prolonged antibiotic therapy more than 14 days (OR: 3.4, p = 0.012) were identified as RF for osteomyelitis due to CS. When performing the multivariate analysis antibiotic therapy >14 days was independent RF (OR: 3.46; p = 0.017).

CONCLUSIONS

Previous antibiotic therapy received more than 14 days is an independent and statistically significant RF for CS osteomyelitis in patients with diabetic foot.

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.

Targeted Antibiotics for Lower Respiratory Tract Infection with Corynebacterium striatum

Purpose

To assess the impact of targeted antibiotic therapy on clinical outcomes of patients with lower respiratory tract (LRT) infection with Corynebacterium striatum (C. striatum).

Methods

A new propensity score-inverse probability of treatment weighting (IPTW) cohort study was conducted by using 10-year data. The study included LRT infection patients with respiratory secretions cultured positive for C. striatum simultaneously. The primary outcome was all-cause hospital mortality; the secondary outcomes included hospital stay, ICU stay and ventilation time. The safety outcomes were drug-related serum creatinine (Cr) increase and thrombocytopenia.

Results

A total of 339 patients were included in the cohort, and 84 (24.78%) initiated vancomycin or linezolid therapy. In the new IPTW cohort, targeted antibiotic therapy did not improve all-cause hospital mortality (P=0.632), and the OR (95% CI) was 0.879 (0.519-1.488). Moreover, targeted antibiotic therapy was not associated with hospital stay (P=0.415), ICU stay (P=0.945) or ventilation time (P=0.885). The side effects of drug-related higher serum Cr (P=0.044) and thrombocytopenic levels (P=0.038) cannot be ignored.

Conclusion

Clinical benefits by vancomycin or linezolid targeted against LRT infection with C. striatum were limited and with drug-related side effects. A prospectively designed study is needed to further confirm the results.

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.

Identification and Evolutionary Relationship of Corynebacterium striatum Clinical Isolates

Corynebacterium striatum has developed into a new community-acquired and hospital-acquired multi-drug resistance (MDR) bacterium, and is a potential target pathogen for infection control and antibacterial management projects. In this study, non-duplicate samples of inpatients were collected from a local central hospital. Mass spectrometry showed that 54 C. striatum isolates mainly appeared in secretion and sputum from 14 departments. Protein fingerprint cluster analysis showed that the isolates were divided into four groups, most of which appeared in summer. The drug resistance test showed that all strains had multi-drug resistance, with high resistance rates to lincosamides, quinolones and tetracycline detected. Further analysis of the phylogenetic tree of C. striatum was conducted by cloning the 16S rRNA gene. It was found that isolates in the same department had high homology and tended to be located in the same branch or to be crossed in the same main branch. The strains in the same evolutionary branch group had the same drug resistance. Screening of site-specific recombinant elements revealed that 18 strains had integrase genes with the same sequence. This study shows that there may be mobile genetic elements in clinical isolates that drive gene exchange among strains, thus causing the cross-infection, spread and evolution of pathogenic bacteria in the hospital.

In vitro Studies of Non-Diphtheriae Corynebacterium Isolates on Antimicrobial Susceptibilities, Drug Resistance Mechanisms, and Biofilm Formation Capabilities

Objective

This study aimed to investigate the antimicrobial susceptibilities, drug resistance mechanisms, and biofilm formation capacities of non-diphtheriae Corynebacterium strains isolated from sterile midstream urine of hospitalized patients with clinical urinary tract infections (UTIs).

Methods

A total of 45 non-diphtheriae Corynebacterium isolates were recovered from sterile midstream urine. The available data of 45 patients were collected. Minimum inhibitory concentrations (MICs) of 10 commonly used antibiotics were determined. Meanwhile, the molecular resistance mechanisms of each agent were performed through PCR with specific primers. Moreover, the biofilm formation capability of each isolate on abiotic surfaces was detected with the MTT method.

Results

In this study, the most prevalent three species were C. striatum (15/45, 33.3%), C. glucuronolyticum (9/45, 20.0%) and C. urealyticum (8/45, 17.8%). These three species also accounted for most renal and ureteral calculi cases. Male patients older than 50 years, especially those with underlying diseases, were more susceptible to non-diphtheriae Corynebacterium infection. All the 45 isolates were 100% susceptible to vancomycin and linezolid, but highly resistant to macrolide–lincosamide–streptogramin B (MLSB), fluoroquinolones, tetracyclines and β-lactams with corresponding mechanisms. The detection rate of multidrug–resistant (MDR) non-diphtheriae Corynebacterium is 91.1%. All isolates are able to form biofilm on abiotic surfaces, except those of C. urealyticum, C. tuberculostearicum and C. jeikeium. Isolates of C. glucuronolyticum and C. Striatum possessed the strongest biofilm formation capacity. C. amycolatum could form biofilm, but varied greatly among different isolates.

Conclusion

C. striatum, C. glucuronolyticum and C. urealyticum were the most prevalent species relevant to UTIs. The high occurrence of MDR isolates and high diversities in resistance profiles, and the distinctive abilities of biofilm formation highlighted the urgency for identification to species level. We should pay more attention to the drug resistance profiles of non-diphtheriae Corynebacterium, which would help improve empirical antibiotic therapy and reduce drug resistance transmission.

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.

Antimicrobial treatment of Corynebacterium striatum invasive infections: a systematic review

The aim of this study was to establish an evidence-based guideline for the antibiotic treatment of Corynebacterium striatum infections. Several electronic databases were systematically searched for clinical trials, observational studies or individual cases on patients of any age and gender with systemic inflammatory response syndrome, harboring C. striatum isolated from body fluids or tissues in which it is not normally present. C. striatum had to be identified as the only causative agent of the invasive infection, and its isolation from blood, body fluids or tissues had to be confirmed by one of the more advanced diagnostic methods (biochemical methods, mass spectrometry and/or gene sequencing). This systematic review included 42 studies that analyzed 85 individual cases with various invasive infections caused by C. striatum. More than one isolate of C. striatum exhibited 100% susceptibility to vancomycin, linezolid, teicoplanin, piperacillin-tazobactam, amoxicillin-clavulanate and cefuroxime. On the other hand, some strains of this bacterium showed a high degree of resistance to fluoroquinolones, to the majority majority of β-lactams, aminoglycosides, macrolides, lincosamides and cotrimoxazole. Despite the antibiotic treatment, fatal outcomes were reported in almost 20% of the patients included in this study. Gene sequencing methods should be the gold standard for the identification of C. striatum, while MALDI-TOF and the Vitek system can be used as alternative methods. Vancomycin should be used as the antibiotic of choice for the treatment of C. striatum infections, in monotherapy or in combination with piperacillin-tazobactam. Alternatively, linezolid, teicoplanin or daptomycin may be used in severe infections, while amoxicillin-clavulanate may be used to treat mild infections caused by C. striatum.

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.

Antimicrobial Resistance and Molecular Epidemiology of Corynebacterium striatum Isolated in a Tertiary Hospital in Turkey

Although Corynebacterium striatum is part of the human flora, it has recently drawn attention both for its multidrug resistance and its role as an invasive infection/outbreak agent. This cross-sectional study aimed to determine the antimicrobial resistance and clonal relationships among C. striatum strains. In total, 81 C. striatum strains were identified using Phoenix-100^TM (BD, Sparks, MD, USA). The antimicrobial resistance of the strains was determined using the Kirby–Bauer disk diffusion method. Clonal relatedness among the strains was performed via arbitrarily primed polymerase chain reaction (AP-PCR). All 81 C. striatum strains were resistant to penicillin, cefotaxime, ciprofloxacin, and tetracycline, but susceptible to vancomycin and linezolid. The resistance rates to gentamicin, erythromycin, and clindamycin were 34.6%, 79%, and 87.7% respectively. AP-PCR results showed no predominant clone among the C. striatum strains. Corynebacterium striatum is reportedly the cause of an increasing number of invasive infections/outbreaks. Moreover, treatment options are limited. The study showed that vancomycin, linezolid, and gentamicin can be selected for the empirical treatment of C. striatum infections. Although no single-clone outbreak was observed in our hospital, small clonal circulations were observed within some units, indicating cross-contamination. Therefore, a comprehensive infection control program is warranted in future.

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.