scholarly journals Clinical Significance and Pathogenesis of Staphylococcal Small Colony Variants in Persistent Infections

2016 ◽  
Vol 29 (2) ◽  
pp. 401-427 ◽  
Author(s):  
Barbara C. Kahl ◽  
Karsten Becker ◽  
Bettina Löffler
Keyword(s):  
Molecular Mechanisms ◽  
Diagnostic Procedures ◽  
Resistance Mechanisms ◽  
Future Research ◽  
Coagulase Negative Staphylococci ◽  
Small Colony Variants ◽  
Content Type ◽  
Staphylococcal Infections ◽  
Airway Infections ◽  
Small Colony

SUMMARYSmall colony variants (SCVs) were first described more than 100 years ago forStaphylococcus aureusand various coagulase-negative staphylococci. Two decades ago, an association between chronic staphylococcal infections and the presence of SCVs was observed. Since then, many clinical studies and observations have been published which tie recurrent, persistent staphylococcal infections, including device-associated infections, bone and tissue infections, and airway infections of cystic fibrosis patients, to this special phenotype. By their intracellular lifestyle, SCVs exhibit so-called phenotypic (or functional) resistance beyond the classical resistance mechanisms, and they can often be retrieved from therapy-refractory courses of infection. In this review, the various clinical infections where SCVs can be expected and isolated, diagnostic procedures for optimized species confirmation, and the pathogenesis of SCVs, including defined underlying molecular mechanisms and the phenotype switch phenomenon, are presented. Moreover, relevant animal models and suggested treatment regimens, as well as the requirements for future research areas, are highlighted.

scholarly journals Identification of Point Mutations in Clinical Staphylococcus aureus Strains That Produce Small-Colony Variants Auxotrophic for Menadione

2014 ◽  
Vol 82 (4) ◽  
pp. 1600-1605 ◽  
Author(s):  
Melissa A. Dean ◽  
Randall J. Olsen ◽  
S. Wesley Long ◽  
Adriana E. Rosato ◽  
James M. Musser
Keyword(s):  
Staphylococcus Aureus ◽  
Pathway Analysis ◽  
Molecular Mechanisms ◽  
Point Mutations ◽  
Biosynthesis Pathway ◽  
Wild Type ◽  
Small Colony Variants ◽  
Content Type ◽  
Genes Encoding ◽  
Small Colony

ABSTRACTStaphylococcus aureussmall-colony variants (SCVs) are implicated in chronic and relapsing infections that are difficult to diagnose and treat. Despite many years of study, the underlying molecular mechanisms and virulence effect of the small-colony phenotype remain incompletely understood. We sequenced the genomes of fiveS. aureusSCV strains recovered from human patients and discovered previously unidentified nonsynonymous point mutations in three genes encoding proteins in the menadione biosynthesis pathway. Analysis of genetic revertants and complementation with wild-type alleles confirmed that these mutations caused the SCV phenotype and decreased virulence for mice.

scholarly journals Low Prevalence of Gram-Positive Isolates Showing Elevated Lefamulin MIC Results during the SENTRY Surveillance Program for 2015–2016 and Characterization of Resistance Mechanisms

2019 ◽  
Vol 63 (4) ◽  
Author(s):  
Rodrigo E. Mendes ◽  
Susanne Paukner ◽  
Timothy B. Doyle ◽  
Steven P. Gelone ◽  
Robert K. Flamm ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Resistance Mechanisms ◽  
Surveillance Program ◽  
Wild Type ◽  
Coagulase Negative Staphylococci ◽  
High Genetic Diversity ◽  
Content Type ◽  
Low Prevalence ◽  
Viridans Group Streptococci

ABSTRACT This study investigated the molecular mechanisms possibly associated with non-wild-type MICs for lefamulin among staphylococci and streptococci included in the lefamulin surveillance program from 2015 to 2016. A total of 2,919 Staphylococcus aureus, 276 coagulase-negative staphylococci (CoNS), 3,923 Streptococcus pneumoniae, 389 β-hemolytic, and 178 viridans group streptococci isolates were included in the surveillance studies. Eleven (0.3% of all S. aureus) S. aureus isolates with lefamulin MICs above the staphylococcal epidemiological cutoff (ECOFF) value (>0.25 μg/ml) were selected for this study. Eight (72.7%) S. aureus (lefamulin MIC, 0.5 to 4 μg/ml) isolates carried vga(A or E), one isolate (MIC, 32 μg/ml) carried lsa(E), one isolate (MIC, 16 μg/ml) had an alteration in L4, and one strain (MIC, 0.5 μg/ml) did not carry any of the investigated resistance mechanisms. A total of 14 (5.1% of all CoNS) CoNS isolates had lefamulin MICs (0.5 to >32 μg/ml) above the ECOFF. Similar to S. aureus, 8 (57.1%) CoNS (lefamulin MIC, 1 to 8 μg/ml) isolates carried vga(A or B), while 2 isolates (MIC, 4 to 32 μg/ml) carried cfr. High genetic diversity was observed among staphylococci, although 3 S. aureus isolates belonged to sequence type 398 (ST398). Among the 3 Streptococcus agalactiae and 3 viridans group streptococci (0.1% of all streptococci surveyed) isolates selected for additional characterization, all but 1 isolate carried lsa(E). This study documents a low occurrence of surveillance isolates exhibiting a non-wild-type MIC for lefamulin, and among these isolates, vga and lsa(E) prevailed in staphylococci and streptococci, respectively.

scholarly journals Influence of IS256 on Genome Variability and Formation of Small-Colony Variants in Staphylococcus aureus

2017 ◽  
Vol 61 (8) ◽  
Author(s):  
Franziska Kleinert ◽  
René Kallies ◽  
Michael Hort ◽  
Annegret Zweynert ◽  
Christiane Szekat ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Acquired Resistance ◽  
Laboratory Strain ◽  
Resistance Mechanisms ◽  
Transposition Frequency ◽  
Related Sequence ◽  
Small Colony Variants ◽  
Content Type ◽  
Small Colony ◽  
Insertion Sites

ABSTRACT Staphylococcus aureus has acquired resistance to nearly all antibiotics used in clinical practice. Whereas some resistance mechanisms are conferred by uptake of resistance genes, others evolve by mutation. In this study, IS256 has been shown to play a role, e.g., in S. aureus strains displaying intermediate resistance to vancomycin (VISA). To characterize the IS256 insertion sites in the genomes of two closely related sequence type 247 (ST247) VISA strains, all insertions were mapped in both VISA and a susceptible control strain. The results showed that the three ST247 strains contained the highest number so far of IS256 insertions for all sequenced S. aureus strains. Furthermore, in contrast to the case with the other IS elements in these genomes, the IS256 insertion sites were not identical in the closely related strains, indicating a high transposition frequency of IS256. When IS256 was introduced into a laboratory strain which was then cultured in the presence of antibiotics, it was possible to isolate small-colony variants (SCVs) that possessed IS256 insertions in guaA and hemY that displayed increased resistance to vancomycin and aminoglycosides, respectively. For these clones, a very rapid reversion to the wild type that resembled the fast reversion of clinical SCVs was observed. The reversion was caused by excision of IS256 in a small number of fast-growing clones that quickly outcompeted the SCVs in broth cultures. In conclusion, the presence of IS256 confers a strong genomic plasticity that is useful for adaptation to antibiotic stress.

Small-colony Variants (SCVs) of Staphylococci: A Role in Foreign Body-associated Infections

2007 ◽  
Vol 30 (9) ◽  
pp. 778-785 ◽  
Author(s):  
C. Von Eiff ◽  
K. Becker
Keyword(s):  
Foreign Body ◽  
Defense Mechanisms ◽  
Susceptibility Testing ◽  
Slow Growth ◽  
Clinical Laboratory ◽  
Coagulase Negative Staphylococci ◽  
Small Colony Variants ◽  
The Past ◽  
Small Colony ◽  
Antibacterial Chemotherapy

Staphylococci have various strategies for resisting therapy that extend beyond classic mechanisms. Clinical experience with device-associated infections as well as with infections due to small-colony variants (SCVs) clearly shows that both antibacterial chemotherapy and host defense mechanisms are often unable to eliminate the pathogens and cure these infections. Of particular interest is the fact that in the past few years an increasing number of various foreign body-related infections due to staphylococcal SCVs have been reported. In this overview, the characteristics of SCVs recovered from clinical specimens and of defined mutants displaying the SCV phenotype are described. Their slow growth and changing biochemical and physiological features represent a challenge to clinical laboratory personnel, because recovery, identification, as well as susceptibility testing of these variants need particular efforts. In addition, the reduced susceptibility to aminoglycosides and the ability of SCVs to persist intracellularly require specific attention for the treatment of these infections. Thus, special efforts to search for these variants formed by Staphylococcus aureus or by coagulase-negative staphylococci should be considered when an infection is particularly resistant to therapy, persists for a long period or fails to respond to apparently adequate therapy with antimicrobial compounds.

Characterization of Staphylococcus epidermidis and Staphyloccocus warneri small-colony variants associated with prosthetic-joint infections

2014 ◽  
Vol 63 (2) ◽  
pp. 176-185 ◽  
Author(s):  
Agnieszka Bogut ◽  
Justyna Niedźwiadek ◽  
Maria Kozioł-Montewka ◽  
Dagmara Strzelec-Nowak ◽  
Jan Blacha ◽  
...  
Keyword(s):  
Antimicrobial Susceptibility ◽  
Staphylococcus Epidermidis ◽  
Hip Prosthesis ◽  
Joint Infection ◽  
Coagulase Negative Staphylococci ◽  
Sensitivity Testing ◽  
Small Colony Variants ◽  
Prosthetic Joint ◽  
Prosthetic Joint Infections ◽  
Small Colony

We determined the frequency of isolation of staphylococcal small-colony variants (SCVs) from 31 culture-positive patients undergoing revision of total hip prosthesis for aseptic loosening or presumed prosthetic-joint infection (PJI). We analysed auxotrophy of cultured SCVs, their antimicrobial susceptibility profiles and their biofilm-forming capacity. Eight SCV strains were cultivated from six (19 %) patients. All SCVs were coagulase-negative staphylococci (CNS) with Staphylococcus epidermidis as the predominant species; there was also one Staphylococcus warneri SCV. The SCVs were auxotrophic for haemin, with one strain additionally auxotrophic for menadione. We noted the presence of two phenotypically (differences concerning antimicrobial susceptibility) and genetically distinct SCV strains in one patient, as well as the growth of two genetically related SCVs that differed in terms of their morphology and the type of auxotrophy in another. Seven out of eight SCVs were resistant to meticillin and gentamicin. In addition, antibiotic sensitivity testing revealed three multidrug-resistant SCV–normal-morphology isolate pairs. One S. epidermidis SCV harboured icaADBC genes and was found to be a proficient biofilm producer. This paper highlights the involvement of CNS SCVs in the aetiology of PJIs, including what is believed to be the first report of a S. warneri SCV. These subpopulations must be actively sought in the routine diagnosis of implant-associated infections. Moreover, in view of the phenotypic and genetic diversity of some SCV pairs, particular attention should be paid to the investigation of all types of observed colony morphologies, and isolates should be subjected to antimicrobial susceptibility testing.

scholarly journals Inactivation of thyA in Staphylococcus aureus Attenuates Virulence and Has a Strong Impact on Metabolism and Virulence Gene Expression

mBio ◽  
2014 ◽  
Vol 5 (4) ◽  
Author(s):  
Andre Kriegeskorte ◽  
Desiree Block ◽  
Mike Drescher ◽  
Nadine Windmüller ◽  
Alexander Mellmann ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Thymidylate Synthase ◽  
Molecular Basis ◽  
De Novo ◽  
Strong Impact ◽  
Small Colony Variants ◽  
Content Type ◽  
Long Term Treatment ◽  
Small Colony ◽  
The Impact

ABSTRACTStaphylococcus aureusthymidine-dependent small-colony variants (TD-SCVs) are frequently isolated from patients with chronicS. aureusinfections after long-term treatment with trimethoprim-sulfamethoxazole (TMP-SMX). While it has been shown that TD-SCVs were associated with mutations in thymidylate synthase (TS;thyA), the impact of such mutations on protein function is lacking. In this study, we showed that mutations inthyAwere leading to inactivity of TS proteins, and TS inactivity led to tremendous impact onS. aureusphysiology and virulence. Whole DNA microarray analysis of the constructed ΔthyAmutant identified severe alterations compared to the wild type. Important virulence regulators (agr,arlRS,sarA) and major virulence determinants (hla,hlb,sspAB, andgeh) were downregulated, while genes important for colonization (fnbA,fnbB,spa,clfB,sdrC, andsdrD) were upregulated. The expression of genes involved in pyrimidine and purine metabolism and nucleotide interconversion changed significantly. NupC was identified as a major nucleoside transporter, which supported growth of the mutant during TMP-SMX exposure by uptake of extracellular thymidine. The ΔthyAmutant was strongly attenuated in virulence models, including aCaenorhabditis eleganskilling model and an acute pneumonia mouse model. This study identified inactivation of TS as the molecular basis of clinical TD-SCV and showed thatthyAactivity has a major role forS. aureusvirulence and physiology.IMPORTANCEThymidine-dependent small-colony variants (TD-SCVs) ofStaphylococcus aureuscarry mutations in the thymidylate synthase (TS) gene (thyA) responsible forde novosynthesis of thymidylate, which is essential for DNA synthesis. TD-SCVs have been isolated from patients treated for long periods with trimethoprim-sulfamethoxazole (TMP-SMX) and are associated with chronic and recurrent infections. In the era of community-associated methicillin-resistantS. aureus, the therapeutic use of TMP-SMX is increasing. Today, the emergence of TD-SCVs is still underestimated due to misidentification in the diagnostic laboratory. This study showed for the first time that mutational inactivation of TS is the molecular basis for the TD-SCV phenotype and that TS inactivation has a strong impact onS. aureusvirulence and physiology. Our study helps to understand the clinical nature of TD-SCVs, which emerge frequently once patients are treated with TMP-SMX.

scholarly journals Pseudomonas aeruginosa Rugose Small-Colony Variants Have Adaptations That Likely Promote Persistence in the Cystic Fibrosis Lung

2009 ◽  
Vol 191 (11) ◽  
pp. 3492-3503 ◽  
Author(s):  
Melissa Starkey ◽  
Jason H. Hickman ◽  
Luyan Ma ◽  
Niu Zhang ◽  
Susan De Long ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Intracellular Signaling ◽  
Tricarboxylic Acid Cycle ◽  
Gene Clusters ◽  
Wild Type ◽  
Phenotypic Analysis ◽  
Small Colony Variants ◽  
Airway Infections ◽  
Small Colony

ABSTRACT Pseudomonas aeruginosa is recognized for its ability to colonize diverse habitats, ranging from soil to immunocompromised people. The formation of surface-associated communities called biofilms is one factor thought to enhance colonization and persistence in these diverse environments. Another factor is the ability of P. aeruginosa to diversify genetically, generating phenotypically distinct subpopulations. One manifestation of diversification is the appearance of colony morphology variants on solid medium. Both laboratory biofilm growth and chronic cystic fibrosis (CF) airway infections produce rugose small-colony variants (RSCVs) characterized by wrinkled, small colonies and an elevated capacity to form biofilms. Previous reports vary on the characteristics attributable to RSCVs. Here we report a detailed comparison of clonally related wild-type and RSCV strains isolated from both CF sputum and laboratory biofilm cultures. The clinical RSCV had many characteristics in common with biofilm RSCVs. Transcriptional profiling and Biolog phenotypic analysis revealed that RSCVs display increased expression of the pel and psl polysaccharide gene clusters, decreased expression of motility functions, and a defect in growth on some amino acid and tricarboxylic acid cycle intermediates as sole carbon sources. RSCVs also elicited a reduced chemokine response from polarized airway epithelium cells compared to wild-type strains. A common feature of all RSCVs analyzed in this study is increased levels of the intracellular signaling molecule cyclic di-GMP (c-di-GMP). To assess the global transcriptional effects of elevated c-di-GMP levels, we engineered an RSCV strain that had elevated c-di-GMP levels but did not autoaggregate. Our results showed that about 50 genes are differentially expressed in response to elevated intracellular c-di-GMP levels. Among these genes are the pel and psl genes, which are upregulated, and flagellum and pilus genes, which are downregulated. RSCV traits such as increased exopolysaccharide production leading to antibiotic tolerance, altered metabolism, and reduced immunogenicity may contribute to increased persistence in biofilms and in the airways of CF lungs.

scholarly journals Genomic investigation of clinically significant coagulase-negative staphylococci

2021 ◽  
Author(s):  
Kevin Cole ◽  
Bridget Atkins ◽  
Martin Llewelyn ◽  
John Paul
Keyword(s):  
High Resolution ◽  
Genomic Analysis ◽  
Staphylococcal Infection ◽  
Clinical Samples ◽  
Future Research ◽  
Emerging Pathogens ◽  
Coagulase Negative Staphylococci ◽  
Content Type ◽  
History Of ◽  
Clinically Significant

Introduction. Coagulase-negative staphylococci have been recognized both as emerging pathogens and contaminants of clinical samples. High-resolution genomic investigation may provide insights into their clinical significance. Aims. To review the literature regarding coagulase-negative staphylococcal infection and the utility of genomic methods to aid diagnosis and management, and to identify promising areas for future research. Methodology. We searched Google Scholar with the terms ( Staphylococcus ) AND (sequencing OR (infection)). We prioritized papers that addressed coagulase-negative staphylococci, genomic analysis, or infection. Results. A number of studies have investigated specimen-related, phenotypic and genetic factors associated with colonization, infection and virulence, but diagnosis remains problematic. Conclusion. Genomic investigation provides insights into the genetic diversity and natural history of colonization and infection. Such information allows the development of new methodologies to identify and compare relatedness and predict antimicrobial resistance. Future clinical studies that employ suitable sampling frames coupled with the application of high-resolution whole-genome sequencing may aid the development of more discriminatory diagnostic approaches to coagulase-staphylococcal infection.

scholarly journals Candida parapsilosis: from Genes to the Bedside

2019 ◽  
Vol 32 (2) ◽  
Author(s):  
Renáta Tóth ◽  
Jozef Nosek ◽  
Héctor M. Mora-Montes ◽  
Toni Gabaldon ◽  
Joseph M. Bliss ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Candida Parapsilosis ◽  
Molecular Genetic ◽  
Antifungal Susceptibility ◽  
Resistance Mechanisms ◽  
Antifungal Drugs ◽  
Host Responses ◽  
Content Type ◽  
Antifungal Drug Resistance ◽  
Geographical Regions

SUMMARYPatients with suppressed immunity are at the highest risk for hospital-acquired infections. Among these, invasive candidiasis is the most prevalent systemic fungal nosocomial infection. Over recent decades, the combined prevalence of non-albicans Candidaspecies outrankedCandida albicansinfections in several geographical regions worldwide, highlighting the need to understand their pathobiology in order to develop effective treatment and to prevent future outbreaks.Candida parapsilosisis the second or third most frequently isolatedCandidaspecies from patients. Besides being highly prevalent, its biology differs markedly from that ofC. albicans, which may be associated withC. parapsilosis’ increased incidence. Differences in virulence, regulatory and antifungal drug resistance mechanisms, and the patient groups at risk indicate that conclusions drawn fromC. albicanspathobiology cannot be simply extrapolated toC. parapsilosis. Such species-specific characteristics may also influence their recognition and elimination by the host and the efficacy of antifungal drugs. Due to the availability of high-throughput, state-of-the-art experimental tools and molecular genetic methods adapted toC. parapsilosis, genome and transcriptome studies are now available that greatly contribute to our understanding of what makes this species a threat. In this review, we summarize 10 years of findings onC. parapsilosispathogenesis, including the species’ genetic properties, transcriptome studies, host responses, and molecular mechanisms of virulence. Antifungal susceptibility studies and clinician perspectives are discussed. We also present regional incidence reports in order to provide an updated worldwide epidemiology summary.

scholarly journals Pharmacodynamic Evaluation of the Activity of Antibiotics against Hemin- and Menadione-Dependent Small-Colony Variants of Staphylococcus aureus in Models of Extracellular (Broth) and Intracellular (THP-1 Monocytes) Infections

2012 ◽  
Vol 56 (7) ◽  
pp. 3700-3711 ◽  
Author(s):  
L. G. Garcia ◽  
S. Lemaire ◽  
B. C. Kahl ◽  
K. Becker ◽  
R. A. Proctor ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Concentration Effect ◽  
Intracellular Bacteria ◽  
Maximal Effect ◽  
Small Colony Variants ◽  
Content Type ◽  
Pharmacodynamic Profile ◽  
Lower Amplitude ◽  
Small Colony ◽  
Antibiotic Failure

ABSTRACTStaphylococcus aureussmall-colony variants (SCVs) persist intracellularly, which may contribute to persistence/recurrence of infections and antibiotic failure. We have studied the intracellular fate ofmenDandhemBmutants (corresponding to menadione- and hemin-dependent SCVs, respectively) of the COL methicillin-resistantS. aureus(MRSA) strain and the antibiotic pharmacodynamic profile against extracellular (broth) and intracellular (human THP-1 monocytes) bacteria. Compared to the parental strain, SCVs showed slower extracellular growth (restored upon medium supplementation with menadione or hemin), reduced phagocytosis, and, for themenDSCV, lower intracellular counts at 24 h postinfection. Against extracellular bacteria, daptomycin, gentamicin, rifampin, moxifloxacin, and oritavancin showed similar profiles of activity against all strains, with a static effect obtained at concentrations close to their MICs and complete eradication as maximal effect. In contrast, vancomycin was not bactericidal against SCVs. Against intracellular bacteria, concentration-effect curves fitted sigmoidal regressions for vancomycin, daptomycin, gentamicin, and rifampin (with maximal effects lower than a 2-log decrease in CFU) but biphasic regressions (with a maximal effect greater than a 3-log decrease in CFU) for moxifloxacin and oritavancin, suggesting a dual mode of action against intracellular bacteria. For all antibiotics, these curves were indistinguishable between the strains investigated, except for themenDmutant, which systematically showed a lower amplitude of the concentration-effect response, with markedly reduced minimal efficacy (due to slower growth) but no change in maximal efficacy. The data therefore show that the maximal efficacies of antibiotics are similar against normal-phenotype and menadione- and hemin-dependent strains despite their different intracellular fates, with oritavancin, and to some extent moxifloxacin, being the most effective.

Sign in / Sign up

Export Citation Format

Share Document