High frequency of macrolide resistance mechanisms in clinical isolates of Corynebacterium species

Suboptimal bioinformatic predictions of antimicrobial resistance from whole-genome sequences in multidrug-resistant Corynebacterium isolates

Herein, we combined different bioinformatics tools and databases (BV-BRC, ResFinder, RAST, and KmerResistance) to perform a prediction of antimicrobial resistance (AMR) in the genomic sequences of 107 Corynebacterium striatum isolates for which trustable antimicrobial susceptibility (AST) phenotypes could be retrieved. Then, the reliabilities of the AMR predictions were evaluated by different metrics: area under the ROC curve (AUC); Major Error Rates (MERs) and Very Major Error Rates (VMERs); Matthews Correlation Coefficient (MCC); F1-Score; and Accuracy. Out of 15 genes that were reliably detected in the C. striatum isolates, only tetW yielded predictive values for tetracycline resistance that were acceptable considering Food and Drug Administration (FDA)'s criteria for quality (MER < 3.0% and VMER with a 95% C.I. ≤1.5-≤7.5); this was accompanied by a MCC score higher than 0.9 for this gene. Noteworthy, our results indicate that other commonly used metrics (AUC, F1-score, and Accuracy) may render overoptimistic evaluations of AMR-prediction reliabilities on imbalanced datasets. Accordingly, out of 10 genes tested by PCR on additional multidrug-resistant Corynebacterium spp. isolates (n = 18), the tetW gene rendered the best agreement values with AST profiles (94.11%). Overall, our results indicate that genome-based AMR prediction can still be challenging for MDR clinical isolates of emerging Corynebacterium spp.

Corynebacterium oculi-related bacterium may act as a pathogen and carrier of antimicrobial resistance genes in dogs: a case report

BACKGROUND

The genus Corynebacterium comprises well-known animal and human pathogens as well as commensals of skin and mucous membranes. Species formerly regarded as contaminants are increasingly being recognized as opportunistic pathogens. Corynebacterium oculi has recently been described as a human ocular pathogen but has so far not been reported in dogs.

CASE PRESENTATION

Here we present two cases of infection with a novel Corynebacterium sp., a corneal ulcer and a case of bacteriuria. The two bacterial isolates could not be identified by MALDI-TOF MS. While 16 S rRNA gene (99.3% similarity) and rpoB (96.6% identity) sequencing led to the preliminary identification of the isolates as Corynebacterium (C.) oculi, whole genome sequencing revealed the strains to be closely related to, but in a separate cluster from C. oculi. Antimicrobial susceptibility testing showed high minimal inhibitory concentrations of lincosamides, macrolides, tetracycline, and fluoroquinolones for one of the isolates, which also contained an erm(X) and tet-carrying plasmid as well as a nonsynonymous mutation leading to an S84I substitution in the quinolone resistance determining region of GyrA.

CONCLUSIONS

While the clinical signs of both dogs were alleviated by antimicrobial treatment, the clinical significance of these isolates remains to be proven. However, considering its close relation with C. oculi, a known pathogen in humans, pathogenic potential of this species is not unlikely. Furthermore, these bacteria may act as reservoir for antimicrobial resistance genes also in a One Health context since one strain carried a multidrug resistance plasmid related to pNG3 of C. diphtheriae.

The Prevalence and Antibiotics Susceptibility Patterns of Corynebacterium minutissimum Isolates from Skin Lesions of Patients with Suspected Erythrasma from Tabriz, Iran

Erythrasma is a chronic infection of the skin that appears in the body folds as flat copper spots. The causative agent of this infection is Corynebacterium minutissimum (C. minutissimum). Erythrasma can be treated with antiseptics or topical antibiotics. The study aimed to investigate the antibiotics susceptibility patterns, and the presence of the erythromycin resistance gene (ermX and mefA) in C. minutissimum isolates in skin lesions with suspected erythrasma. From July 2020 to May 2022, 278 skin scrub specimens were collected from patients admitted to the hospital of Tabriz University of Medical Sciences. Specimens were incubated on the blood agar plates and isolates were identified by microbiological laboratory methods. The antibiotic susceptibility patterns were determined by the disk diffusion method and resistance genes of ermX and mefA were detected by the PCR method. Out of 278 specimens, 41 C. minutissimum isolates (14.74%) were recovered. The highest frequency of resistance was observed to a penicillin (75.6%) followed by erythromycin and clarithromycin (39.02%), clindamycin (30.05%), tetracycline (24.2%), and gentamicin and neomycin (19.5%). The frequencies of ermX and mefA genes were 75% and 12.5%, respectively. Resistance to antimicrobial drugs was common and worrying. Resistance to erythromycin in C. minutissimum is mainly related to the ermX gene.

Complete Genome Sequences of Four Macrolide-Resistant Nondiphtheritic Corynebacterium Isolates

This report describes the complete genome sequences of four isolates of the nondiphtheritic Corynebacterium (NDC) species Corynebacterium pseudodiphtheriticum and Corynebacterium propinquum, recovered during investigation of a large diphtheria outbreak in Bangladesh. These data will assist in better delineating the boundary between these related species and understanding their virulence potential.

Corynebacterium striatum-Got Worse by a Pandemic?

The role of Corynebacterium striatum has been demonstrated in different nosocomial infections. An increasing number of publications have demonstrated its virulence in the respiratory tract, especially in the immunosuppressed patient population. The number of these patients has increased significantly during the COVID-19 pandemic. For this reason, we aimed to investigate the prevalence and antimicrobial resistance pattern of this species between 2012 and 2021 at the Clinical Center of the University of Szeged, Hungary. Altogether, 498 positive samples were included from 312 patients during the study period. On the isolates, 4529 antibiotic susceptibility tests were performed. Our data revealed that the prevalence of C. striatum increased during the COVID-19 pandemic, the rise occurred in respiratory, blood culture, and superficial samples. During the study period, the rifampicin resistance significantly increased, but others have also changed dynamically, including linezolid. The species occurred with diverse and changing co-pathogens in the COVID-19 era. However, the increasing rifampicin and linezolid resistance of C. striatum was probably not due to the most commonly isolated co-pathogens. Based on resistance predictions, vancomycin is likely to remain the only effective agent currently in use by 2030.

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.

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.

Whole genome sequence of a non-toxigenic Corynebacterium diphtheriae strain from a hospital in southeastern China

Background

Sporadic cases of infection with non-toxigenic Corynebacterium diphtheriae (C. diphtheriae) isolates have been reported in regions covered by the Diphtheria-Tetanus-Pertussis vaccine, but no information describing the whole genome of non-toxigenic strains collected in China is available. Therefore, in this work, the complete genome of a non-toxigenic strain of C. diphtheriae from a hospital located in southeastern China was performed.

Results

This non-toxigenic isolate belonged to the belfanti biotype and possessed a unique ST (assigned as ST799 in pubMLST). ErmX was present in the genome sequence and this isolate owned the resistance to erythromycin and clindamycin. Genes coding for virulence factors involved in adherence, iron-uptake and regulation of diphtheria toxin were also found. Two genes were involved in the interaction between pathogen and host. The phylogenetic analysis revealed that this newly isolated strain was similar to the strain NCTC10838, CMCNS703 and CHUV2995.

Conclusion

Non-toxigenic C. diphtheriae strain contained virulence factors, thus it is able to cause an infectious disease, aspect that could be clarified by performing the whole genome sequencing analysis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12863-021-00998-9.

Corynebacterium Jeikeium Endocarditis: A Review of the Literature

Corynebacterium jeikeium is a gram-positive, aerobic, pleomorphic, nonspore forming bacillus, commonly present on the skin surface. Infective endocarditis secondary to C. jeikeium most commonly affects left-sided heart valves and has a higher likelihood to require valve replacement compared to other Corynebacterium endocarditis. C. jeikeium endocarditis is extremely difficult to treat as it is characteristically resistant to penicillin, cephalosporins and aminoglycosides, and sensitivity to quinolones, macrolides, tetracyclines and rifampin is variable. Despite treatment, mortality rates as high as 33% have been reported. We hereby review the literature regarding the epidemiology, diagnosis and treatment of this deadly microorganism.

Classification of three corynebacterial strains isolated from a small paddock in North Rhine-Westphalia: proposal of Corynebacterium kalinowskii sp. nov., Corynebacterium comes sp. nov. and Corynebacterium occultum sp. nov

Three novel corynebacterial species were isolated from soil sampled at a paddock in Vilsendorf, North Rhine-Westphalia, Germany. The strains were coccoid or irregular rod-shaped, catalase-positive and pale white to yellow-orange in colour. By whole genome sequencing and comparison of the 16S rRNA genes as well as the whole genome structure, it was shown that all three strains represent novel species of the family Corynebacteriaceae, order Corynebacteriales, class Actinobacteria. This project describes the isolation, identification, sequencing, and phenotypic characterization of the three novel Corynebacterium species. We propose the names Corynebacterium kalinowskii sp. nov. (DSM 110639^T=LMG 31801^T), Corynebacterium comes sp. nov. (DSM 110640^T=LMG 31802^T), and Corynebacterium occultum sp. nov. (DSM 110642^T=LMG 31803^T).

Corynebacterium phoceense, resident member of the urogenital microbiota?

Corynebacterium phoceense is a Gram-positive species previously isolated from human urine. Although other species from the same genus have been associated with urinary tract infections, C. phoceense is currently believed to be a non-pathogenic member of the urogenital microbiota. Prior to our study, only two isolates were described in the literature, and very little is known about the species. Here, we describe C. phoceense UFMG-H7, the first strain of this species isolated from the urine of healthy cattle. The genome for this isolate was produced and compared to the two other publicly available C. phoceense as well as other Corynebacterium genome assemblies. Our in-depth genomic analysis identified four additional publicly available genome assemblies that are representatives of the species, also isolated from the human urogenital tract. Although none of the strains have been associated with symptoms or disease, numerous genes associated with virulence factors are encoded. In contrast to related Corynebacterium species and Corynebacterium species from the bovine vaginal tract, all C. phoceense strains examined code for the SpaD-type pili suggesting adherence is essential for its persistence within the urinary tract. As the other C. phoceense strains analysed were isolated from the human urogenital tract, our results suggest that this species may be specific to this niche.

Antimicrobial susceptibility of Corynebacterium diphtheriae and Corynebacterium ulcerans in Germany 2011-17

BACKGROUND

Diphtheria is mainly caused by diphtheria-toxin-producing strains of Corynebacterium diphtheriae and Corynebacterium ulcerans. The recommended first-line antibiotic is penicillin or erythromycin, but reliable susceptibility data are scarce.

OBJECTIVES

To define WT MIC distributions of 12 antimicrobial agents and provide data for the determination of tentative epidemiological cut-off values (TECOFFs) for potentially toxigenic corynebacteria and to evaluate the potential usefulness of a gradient test (Etest) for susceptibility testing of penicillin, erythromycin and clindamycin.

METHODS

For the 421 human or veterinary isolates from the period 2011-17, MICs of 12 antimicrobial agents were determined. Etest performance was evaluated for penicillin, erythromycin and clindamycin.

RESULTS

MIC distributions were characterized and TECOFFs could be set for 11 out of 24 antibiotic/species combinations. The current EUCAST clinical breakpoints, predominantly determined for Corynebacterium species other than C. diphtheriae and C. ulcerans, divide the WT MIC distributions of penicillin and clindamycin, thereby making reproducible susceptibility testing of C. diphtheriae and C. ulcerans difficult. For erythromycin, 4% of C. diphtheriae and 2% of C. ulcerans had MICs higher than those for WT isolates. Phenotypically detectable resistance to other antibiotics was rare. Etest underestimated MICs of penicillin and lower concentrations needed to be included for erythromycin, while for clindamycin the Etest was not a good surrogate method.

CONCLUSIONS

MIC distributions based on reference broth microdilution for potentially toxigenic Corynebacterium spp. were developed. For five and six agents, TECOFFs were suggested for C. diphtheriae and C. ulcerans, respectively, but for Corynebacterium pseudotuberculosis the number of isolates was too low.

Clinical relevance and antimicrobial susceptibility profile of the unknown human pathogen Corynebacterium aurimucosum

Introduction. Even though Corynebacterium aurimucosum has been described in 2002, this species has long been underestimated due to the unreliability of conventional identification methods and only a few cases of infections have been reported.Hypothesis/Gap Statement. Little is known about clinical significance and antimicrobial susceptibility profile of this uncommon species.Aim. To evaluate the clinical relevance of C. aurimucosum and its antimicrobial susceptibility profile.Methodology. All C. aurimucosum isolates, collected from 2010 to 2019 in 10 French university hospitals, were retrospectively included. Demographic, clinical and microbiological data were collected for all cases. Antimicrobial susceptibility testing was performed according to the 2019 EUCAST guidelines.Results. Fifty-seven clinical isolates of C. aurimucosum were collected in 57 patients (median age, 65.8 years; male/female sex ratio, 1.1), mostly from urine (28 %), blood culture (28 %) and bone/synovial fluid (19 %) samples. Of them, 14 cases of infection were confirmed, mainly bone and joint infections (50 %) followed by urinary tract infections (UTIs) (21 %), bacteremia (14 %), skin and soft-tissue infections (14 %). C. aurimucosum was recovered in pure culture in 36 % of cases (UTIs and bacteremia) while mixed cultures were observed for other infections. By testing 52 clinical isolates in vitro, this species appeared to be fully susceptible to linezolid and vancomycin while most isolates (>80 %) were susceptible to amoxicillin (MIC₉₀, 2 µg ml^-1), gentamicin, tetracycline and rifampicin. Both cefotaxime and ciprofloxacin seemed to have a limited activity (ca. 50 % of susceptible strains). The MIC distribution for ciprofloxacin showed a bimodal profile with a population of highly-resistant strains with MICs >2 µg ml^-1. Most isolates (>90 %) were categorized as resistant to penicillin G and clindamycin.Conclusion. C. aurimucosum should be considered as an actual opportunistic pathogen, and treatment with amoxicillin, vancomycin or linezolid should be preferred.

Current Evidence for Corynebacterium on the Ocular Surface

Corynebacterium species are commonly found in the conjunctiva of healthy adults and are recognized as non-pathogenic bacteria. In recent years, however, Corynebacterium species have been reported to be potentially pathogenic in various tissues. We investigated Corynebacterium species on the ocular surface and reviewed various species of Corynebacterium in terms of their antimicrobial susceptibility and the underlying molecular resistance mechanisms. We identified a risk for Corynebacterium-related ocular infections in patients with poor immunity, such as patients with diabetes or long-term users of topical steroids, and in those with corneal epithelial damage due to trauma, contact lens wear, lagophthalmos, and trichiasis. The predominant strain in the conjunctiva was C. macginleyi, and the species associated with keratitis and conjunctivitis were C. macginleyi, C. propinquum, C. mastitidis, C. pseudodiphtheriticum, C. accolens, C. striatum, C. xerosis, and C. bovis. Overall, Corynebacterium species present on the ocular surface were resistant to quinolones, whereas those in the nasal cavity were more susceptible. The prevalence of fluoroquinolone-resistant Corynebacterium has not changed in the past 10 years; however, Corynebacterium species remain susceptible to third-generation cephems. In conclusion, the use of third-generation cephems should be a reasonable and pragmatic approach for treatment of ocular infections caused by Corynebacterium species.

Antimicrobial Susceptibility and Characterization of Resistance Mechanisms of Corynebacterium urealyticum Clinical Isolates

Corynebacterium urealyticum is a non-diphtherial urease-producing clinically relevant corynebacterial, most frequently involved in urinary tract infections. Most of the C. urealyticum clinical isolates are frequently resistant to several antibiotics. We investigated the susceptibility of 40 C. urealyticum isolated in our institution during the period 2005–2017 to eight compounds representative of the main clinically relevant classes of antimicrobial agents. Antimicrobial susceptibility was determined by the Epsilometer test. Resistance genes were searched by PCR. All strains were susceptible to vancomycin whereas linezolid and rifampicin also showed good activity (MICs₉₀ = 1 and 0.4 mg/L, respectively). Almost all isolates (39/40, 97.5%) were multidrug resistant. The highest resistance rate was observed for ampicillin (100%), followed by erythromycin (95%) and levofloxacin (95%). Ampicillin resistance was associated with the presence of the blaA gene, encoding a class A β-lactamase. The two rifampicin-resistant strains showed point mutations driving amino acid replacements in conserved residues of RNA polymerase subunit β (RpoB). Tetracycline resistance was due to an efflux-mediated mechanism. Thirty-nine PFGE patterns were identified among the 40 C. urealyticum, indicating that they were not clonally related, but producing sporadic infections. These findings raise the need of maintaining surveillance strategies among this multidrug resistant pathogen.

Factors associated with treatment duration and recurrence rate of complicated mastitis

BACKGROUND

The incidence of mastitis has increased, and this disease can lead to long antibiotic courses and complications. Here, we aimed to identify the factors associated with antibiotic duration and recurrence of complicated mastitis.

MATERIALS AND METHODS

This retrospective cohort study was conducted in a tertiary hospital in Taiwan. All hospitalized patients diagnosed with mastitis (ICD-9 code 611.0) from Jan. 1, 2012, to Dec. 31, 2016, were enrolled. Patient characteristics and clinical data were obtained from the medical charts. Recurrence was defined as mastitis within the first year after the discontinuation of antibiotics for at least 7 days.

RESULTS

In total, 214 females with a median age of 37 years old (IQR 33-45) were enrolled. A total of 148 patients (69.2%) underwent debridement, and 122 (57.0%) underwent biopsy. Histopathological examinations revealed granulation tissue in 44.6% (62/139) of the patients. Positive cultures were obtained in 65.9% (141/214) of the patients. Coagulase-negative staphylococci (64/141, 45.4%) was the most common pathogen, followed by Corynebacterium species (42/141, 29.8%). The median hospitalization length and antibiotic course were 7 (IQR 4-13) and 37 days (IQR 22-77), respectively. Three patients died of breast cancer during treatment. The recurrence rate was 18.5% (39/211). Younger age, corynebacterial infection, and pregnancy were associated with longer treatment durations (P < 0.001, 0.003, <0.001). Corynebacterial infection was associated with a 2.16-fold (95% CI: 1.11-4.20) increase in recurrence after adjusting for age.

CONCLUSION

Corynebacterial infection is associated with longer treatment courses and an increased recurrence rate of complicated mastitis. Therefore, specific treatments should be considered.

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.

Pyogenic tenosynovitis of the wrist due to Corynebacterium striatum in a patient with dermatomyositis: A case report

INTRODUCTION

Corynebacterium striatum is common contaminant in clinical specimens. Here, we report a rare case of pyogenic tenosynovitis of the wrist caused by C striatum in a dermatomyositis patient taking oral immunosuppressants.

PATIENT CONCERNS

A 67-year-old Japanese woman with dermatomyositis had a history of multiple intraarticular injections of corticosteroids to the right wrist joint for the treatment of osteoarthritis. She was admitted to our hospital with a painful lump on the right dorsal wrist lasting for three months. MRI revealed cellulitis of the dorsum of the right wrist and hand and fluid collection in the extensor tendon sheath. C striatum was detected in the cultures of three samples of synovial fluid taken from the dorsal hand.

DIAGNOSIS

Pyogenic tenosynovitis of the wrist due to C striatum.

INTERVENTIONS

The infection was successfully controlled with synovectomy and adjuvant antibiotic therapy.

OUTCOMES

There has been no sign of recurrence for 12-months after the surgical treatment.

LESSONS

This is the first reported case of pyogenic tenosynovitis due to C striatum in a patient with dermatomyositis. Clinicians should be aware that patients undergoing immunosuppressive therapy have a risk of C striatum infection.

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.

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).

Corynebacterium coyleae as potential urinary tract pathogen

Corynebacterium coyleae is part of the commensal microflora of the skin, urethra, mucous membranes, and genital tract. Isolates from patients with urinary tract infection (UTI) were reported, but the pathogenic potential of this species has not been defined yet. The aim of the study is to determine whether C. coyleae could be the etiological agent of UTI and to analyze its antibiotic susceptibility. Urine samples were cultured quantitatively according to accepted laboratory procedures. The identification of bacterial isolates was carried out using the Vitek MS (bioMérieux) and antibiotic susceptibility was tested using disc diffusion according to EUCAST guidelines. Between 1 January 2017 and 30 October 2018, a total of 39 C. coyleae strains were isolated. This represented 0.32% of all urine samples cultured in the laboratory during the collection period. The strains were isolated from samples obtained from 35 women and 3 men (age median for all—64 years). One female patient presented with C. coyleae in her urine twice at an interval of 21 months. In six cases of UTI, C. coyleae was isolated in monoculture. The isolates had the same resistance pattern. A total of 11 strains were obtained from cases with a clinical diagnosis of UTI. In 13 cases, the strain was cultured in a monoculture and in 28 cases with accompanying species. All strains were susceptible to vancomycin. However, resistance to ciprofloxacin was observed for 58.4% of the strains. Urine isolates of C. coyleae must be considered as contamination or normal flora in most cases (28/39, 72%). In the remaining cases, it can be considered as potential etiologic agents, mostly in women and especially in the 6 UTI cases where C. coyleae was found as the single culture-positive species. Several of these isolates demonstrate resistance to antibiotics commonly used in empiric treatment of urinary tract infections.

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.

Characterization of Corynebacterium diphtheriae, C. confusum and C. amycolatum isolated from sows with genitourinary infection

Porcine Corynebacterium infection is still poorly studied, even though the pig has been described as an asymptomatic carrier of Corynebacterium species, including the zoonotic species C. ulcerans, C. confusum and C. amycolatum. Here we present the identification, molecular and antimicrobial susceptibility characterization of coryneform bacteria isolated from sows with urinary tract infection. C. diphtheriae, C. confusum and C. amycolatum were isolated from sows with urinary infection and metritis. Corynebacterium species were identified by MALDI-TOF MS and confirmed by 16S rRNA and rpoB sequencing. All porcine C. diphtheriae strains were further characterized as non-toxigenic (tox^-). SE-AFLP genotyping was also performed and enabled not only Corynebacterium species differentiation but also the assessment of C. amycolatum genetic heterogeneity. All studied porcine Corynebacterium strains presented alarming resistance profiles with high MIC values for macrolides/lincosamide, tetracyclines and quinolones, which can be related with high usage in both veterinary and human medicine. Isolation of zoonotic Corynebacterium species from commercial swine is important for assessing the potential zoonotic risk for farmers and further implication for both human and animal treatment.

Microbiology and Biofilm Trends of Silicone Lacrimal Implants: Comparing Infected Versus Routinely Removed Stents

PURPOSE

To investigate the pathogens and biofilms responsible for clinically significant infection of silicone stents implanted within the lacrimal system.

METHODS

Retrospective review of culture results and patient demographics for all silicone lacrimal stents removed early for clinically significant infection and sent to the Bascom Palmer Microbiology Laboratory through the end of year 2010. As a control, routinely removed, clinically noninfected stents from the same institution were prospectively sent for culture over a 6-month period. Four clinically infected and 6 clinically noninfected stents showing mucus within the lumen at removal were sent for scanning electron microscopy. Images were randomized and graded by a microbiologist for the presence of organisms, matrix deposits, organisms within matrix, and overall impression of significant biofilm formation.

RESULTS

Nineteen stents were included in the study; 100% of clinically infected (n = 10) and noninfected (n = 9) stents were culture positive. Culture positivity for nontuberculous mycobacterium was found in 90% of infected stents and none of the noninfected stents (p < 0.001). Of infected stents, 50% grew Gram-positive organisms compared with 89% of noninfected stents (p = 0.07). Fifty percent of infected versus 67% of noninfected stents were culture positive for Gram-negative organisms (p = 0.46). Electron microscopy of stents revealed organisms consistent with culture results (size, shape) in planktonic and biofilm form. Masked observer image grading revealed a statistically significant higher amount of organism and biofilm on infected versus noninfected specimen.

CONCLUSION

Nontuberculous mycobacteria comprise the primary pathogens responsible for clinically significant infection of silicone stents in the lacrimal system in South Florida. Robust biofilm production by this organism likely plays a role in pathogenesis. Further research into biofilm-related lacrimal implant infection may aid in the development of useful prevention and treatment strategies.

Diphtheroids-Important Nosocomial Pathogens

INTRODUCTION

Diphtheroids are defined as aerobic, non-sporulating, pleomorphic Gram-positive bacilli which are more uniformly stained than Corynebacterium diphtheriae, lack the metachromatic granules and are arranged in a palisade manner. They are usually commensals of the skin and mucous membranes. They differ from C.diphtheriae in biochemical rea-ctions as well as in toxin production. Since, they are usually found as commensals on the skin, they are often considered as mere contaminants when isolated from clinical samples. However, there are increasing reports of these organisms being associated with various infections. Hence, we felt the need to study the common species associated with infections and know the properties of these organisms which are otherwise considered as mere laboratory contaminants.

AIM

To identify the various species of diphtheroids isolated as pure growth from clinical specimens whose Gram's smear revealed numerous inflammatory cells with Gram positive bacilli and had clinical evidence.

MATERIALS AND METHODS

A total of 100 isolates of Gram-positive bacilli from 16,242 clinical samples received in the Microbiology Department of Kasturba Medical College were considered for this study from Dec 2013-Dec 2014. Gram-positive bacilli which were seen in the smear along with pus cells, isolated as pure growth and reported as "Corynebacterium spp having clinical significance" were taken for this study while those which were reported as 'Probable skin contaminants' were excluded from this study. Species identification of Gram-positive bacilli was done by biochemical reactions. Antibiotic susceptibility test was done by Kirby-Bauer disk diffusion method. Biofilm production was done by the microtitre plate method of O'Toole and Kolter and statistical analysis was done by using proportion test and Chi-square test.

RESULTS

Various species of diphtheroids were isolated from different clinical specimens. C. pseudotuberculosis, C. renale, C. ulcerans, C. striatum, C. minutissimum, Corynebacterium haemolyticum isolated from catheter tips, sputum, tracheostomy secretions and wound infections were highly resistant to many antibiotics while isolates from blood namely C. pseudotuberculosis, C. minutissimum, C. ulcerans and C. renale were nearly sensitive to most of them. It was also interesting to note that there was an increased rate of biofilm production in these isolates.

CONCLUSION

Corynebacterium pseudotuberculosis, Coryne- bacterium ulcerans, Corynebacterium renale, Corynebacterium bovis, Corynebacterium striatum, Corynebacterium minutissimum, Corynebacterium pseudodiphtheriticum and Corynebacterium haemolyticum may survive in the form of biofilms in hospitals and cause multidrug resistant infections. Hence, we need to judiciously identify these organisms, find their antimicrobial susceptibility, treat them and thus prevent infections in hospitals.

Corynebacterium striatum empyema and osteomyelitis in a patient with advanced rheumatoid arthritis

Corynebacterium striatum, which is a common coloniser of human skin and mucous membranes, is increasingly being recognised as an emerging pathogen. We present a case of a 69-year-old woman with empyema and osteomyelitis caused by C. striatum. To the best of our knowledge, this is the first case where these two infections from this bacterium were identified together in the same individual.

Corinebacterium urealyticum: increased incidence of infection and encrusted uropathy

INTRODUCTION

Corynebacterium urealyticum (CU) affects patients who are immunosuppressed, chronically ill or have undergone numerous operations. Obstructive uropathy (OU) is a complication of infection.

STUDY OBJECTIVE

To demonstrate the growing increase in cases of infection by CU and OU in the past 5 years.

MATERIAL AND METHODS

A descriptive study was conducted of urological patients with CU-positive urine cultures (January 2009-December 2014). We calculated the annual distribution and clinical characteristics of infection by CU and OU. Minimum follow-up: 6 months. We obtained the statistical means and ranges of clinical parameters pre/post-therapy.

RESULTS

The total number of patients with CU was 115 (men, 87; women, 28). The mean age was 67.9 years (range, 6-95 years), and the annual distribution of cases for 2009, 2010, 2011, 2012, 2013 and 2014 was 9 (7.8%), 13 (11.3%), 9 (7.8%), 20 (17.4%), 31 (27%) and 33 (28.7%), respectively. The increase in cases for 2009-2014 was 300%. Multiple urological surgeries were performed in 89 cases (77.3%), with surgical complications in 77 cases (66.9%). Eighteen (15.6%) patients had OU (men, 13; women, 5), 12 had pyelitis (66.7%), 3 had cystopathy (16.6%), 2 had prostatic capsule disease (11.2%) and 1 had mesh calcification (5.5%). The analysis of the 18 cases with OU showed pre/postantibiotic therapy urine pHs of 8 (r, 6-9) vs. 6 (r, 5-7). All postantibiotic cultures were negative. Acidifying solution was applied in 5 cases, and surgery was performed in 13 cases (72.2%). The results from before/after the multimodal therapy showed renal impairment in 12 (66.6%) vs. 9 cases (50%) and glomerular filtration rates (GFR) of 45.8 (r, 6->90) vs. 52.7 (r, 13->90). The improvement in GFR was 6.94 points (T Wilcoxon; P=.102). The radiology results (incrustations) showed improvement in 13 patients (72.2%) and no change in 5 (27.8%). There was no specific mortality for CU.

CONCLUSIONS

The prevalence of infection by CU and OU is increasing. Antibiotic treatment is highly effective. Acidifying solutions are an acceptable option for reducing calcifications.

Corynebacterium urealyticum: a comprehensive review of an understated organism

Corynebacterium urealyticum is a Gram positive, slow-growing, lipophilic, multi-drug resistant, urease positive micro-organism with diphtheroid morphology. It has been reported as an opportunistic nosocomial pathogen and as the cause of a variety of diseases including but not limited to cystitis, pyelonephritis, and bacteremia among others. This review serves to describe C. urealyticum with respect to its history, identification, laboratory investigation, relationship to disease and treatment in order to allow increased familiarity with this organism in clinical disease.

Erm(X)-mediated resistance to macrolides, lincosamides and streptogramins in Actinobaculum schaalii

OBJECTIVES

Actinobaculum schaalii is a Gram-positive bacillus increasingly reported as a causative agent of urinary tract infections as well as invasive infections, mainly in the elderly and patients with underlying urological conditions. Since little is known about the molecular basis of antimicrobial resistance in A. schaalii, the aim of this study was to investigate resistance to macrolides, lincosamides and streptogramins (MLS) in this emerging pathogen.

METHODS

A total of 32 A. schaalii clinical isolates from France and Switzerland were studied. MICs of erythromycin, spiramycin, lincomycin, clindamycin and quinupristin/dalfopristin were determined by the agar dilution method. Resistance genes erm(A), erm(B), erm(C), erm(F), erm(G), erm(X), msr(A) and mef(A) were screened by PCR. The genetic environment was determined by random cloning and PCR mapping.

RESULTS

Out of 32 isolates tested, 21 were highly resistant to erythromycin, spiramycin, lincomycin and clindamycin (MICs >256 mg/L), whereas 11 exhibited low MICs (MICs < 0.12 mg/L). On the other hand, quinupristin/dalfopristin remained active against all the isolates. An inducible MLSB resistance phenotype was noted in all cases. The erm(X) gene was detected among all resistant strains, whereas none was detected in susceptible strains. Analysis of genetic support and environment revealed that erm(X) was probably part of the chromosome of A. schaalii.

CONCLUSIONS

This study is the first molecular characterization of MLS resistance in A. schaalii. In all cases, it was due to the presence of erm(X), a methylase gene previously identified in other clinically relevant Gram-positive bacilli.

The genus corynebacterium and other medically relevant coryneform-like bacteria

Catalase-positive Gram-positive bacilli, commonly called "diphtheroids" or "coryneform" bacteria were historically nearly always dismissed as contaminants when recovered from patients, but increasingly have been implicated as the cause of significant infections. These taxa have been underreported, and the taxa were taxonomically confusing. The mechanisms of pathogenesis, especially for newly described taxa, were rarely studied. Antibiotic susceptibility data were relatively scant. In this minireview, clinical relevance, phenotypic and genetic identification methods, matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) evaluations, and antimicrobial susceptibility testing involving species in the genus Corynebacterium and other medically relevant Gram-positive rods, collectively called coryneforms, are described.