scholarly journals Characterization of Staphylococcus aureus Small Colony Variant (SCV) Clinical Isolates in Zaria, Nigeria

2019 ◽  
pp. 1-9
Author(s):  
R. O. Ikala ◽  
B. O. Olayinka ◽  
E. E. Ebah
Keyword(s):  
Virulence Genes ◽  
University Teaching ◽  
Wild Type ◽  
Coagulase Negative Staphylococci ◽  
Antibiotic Susceptibility Pattern ◽  
Small Colony Variant ◽  
Standard Procedures ◽  
Significant Difference ◽  
Small Colony

Staphylococcal isolates from specimen submitted to the Medical Microbiology laboratory of Ahmadu Bello University Teaching Hospital, Zaria were collected over a period of 6 months (February-July 2012), characterized by microbiological standard procedures and the S. aureus small colony variant (SCV) isolates were isolated. The antibiotic susceptibility pattern of the isolates was determined by the Kirby-Bauer-CLSI modified disc agar diffusion (DAD) technique. The SCV isolates were assessed for the carriage of four virulence genes; sdrE (putative adhesin) icaA (intracellular adhesin) hlg (hemolysin), Cna (collagen adhesin). A total of 258 non-duplicate staphylococcal isolates made up of 219 (84%) S. aureus and 39 (15%) coagulase-negative staphylococci (coNS) where obtained. A total of 48 (22%) isolates were determined to be S. aureus SCV mainly from wound/abscess (31%). S. aureus SCV isolates were generally resistant to all the nine antibiotics tested with only minimal sensitivity to tigecyclin (10.4%) and ciprofloxacin (18.8%). Statistically, there was no significant difference between the microbial load and the different antibiotics that were used, (P ≥0.05). None of the S. aureus SCV isolates carried the four virulence genes which were tested in this study. The results have therefore proved that S. aureus small colony variant exist in our environment and they are more resistant to most antimicrobial agent than their wild type.

scholarly journals Enhanced production of exopolysaccharide matrix and biofilm by a menadione-auxotrophic Staphylococcus aureus small-colony variant

2010 ◽  
Vol 59 (5) ◽  
pp. 521-527 ◽  
Author(s):  
Rachna Singh ◽  
Pallab Ray ◽  
Anindita Das ◽  
Meera Sharma
Keyword(s):  
Staphylococcus Aureus ◽  
Tricarboxylic Acid Cycle ◽  
Surface Hydrophobicity ◽  
Tricarboxylic Acid ◽  
Polysaccharide Intercellular Adhesin ◽  
Wild Type ◽  
Small Colony Variant ◽  
Enhanced Production ◽  
Small Colony

The role of Staphylococcus aureus small-colony variants (SCVs) in the pathogenesis of biofilm-associated infections remains unclear. This study investigated the mechanism behind increased biofilm-forming potential of a menadione-auxotrophic Staphylococcus aureus SCV compared with the wild-type parental strain, as recently reported by our laboratory. SCVs displayed an autoaggregative phenotype, with a greater amount of polysaccharide intercellular adhesin (PIA), significantly reduced tricarboxylic acid cycle activity and a decreased susceptibility to aminoglycosides and cell-wall inhibitors compared with wild-type. The biofilms formed by the SCV were highly structured, consisting of large microcolonies separated by channels, and contained more biomass as well as significantly more PIA than wild-type biofilms. The surface hydrophobicity of the two phenotypes was similar. Thus, the autoaggregation and increased biofilm-forming capacity of menadione-auxotrophic Staphylococcus aureus SCVs in this study was related to the enhanced production of PIA in these variants.

scholarly journals Rapidly Correcting Frameshift Mutations in the Mycobacterium tuberculosis orn Gene Produce Reversible Ethambutol Resistance and Small-Colony-Variant Morphology

2020 ◽  
Vol 64 (9) ◽  
Author(s):  
Hassan Safi ◽  
Subramanya Lingaraju ◽  
Shuyi Ma ◽  
Seema Husain ◽  
Mainul Hoque ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Frameshift Mutation ◽  
Relative Increase ◽  
Wild Type ◽  
Content Type ◽  
Reading Frame ◽  
Small Colony Variant ◽  
Large Colony ◽  
Small Colony ◽  
High Level

ABSTRACT We have identified a previously unknown mechanism of reversible high-level ethambutol (EMB) resistance in Mycobacterium tuberculosis that is caused by a reversible frameshift mutation in the M. tuberculosis orn gene. A frameshift mutation in orn produces the small-colony-variant (SCV) phenotype, but this mutation does not change the MICs of any drug for wild-type M. tuberculosis. However, the same orn mutation in a low-level EMB-resistant double embB-aftA mutant (MIC = 8 μg/ml) produces an SCV with an EMB MIC of 32 μg/ml. Reversible resistance is indistinguishable from a drug-persistent phenotype, because further culture of these orn-embB-aftA SCV mutants results in rapid reversion of the orn frameshifts, reestablishing the correct orn open reading frame, returning the culture to normal colony size, and reversing the EMB MIC back to that (8 μg/ml) of the parental strain. Transcriptomic analysis of orn-embB-aftA mutants compared to wild-type M. tuberculosis identified a 27-fold relative increase in the expression of embC, which is a cellular target for EMB. Expression of embC in orn-embB-aftA mutants was also increased 5-fold compared to that in the parental embB-aftA mutant, whereas large-colony orn frameshift revertants of the orn-embB-aftA mutant had levels of embC expression similar to that of the parental embB-aftA strain. Reversible frameshift mutants may contribute to a reversible form of microbiological drug resistance in human tuberculosis.

Characterization of Staphylococcus pseudintermedius Isolates from Skin Infections of Dogs

2021 ◽  
Author(s):  
Hridya Susan Varughese ◽  
Murugesan Ananda Chitra
Keyword(s):  
Virulence Genes ◽  
Bacterial Genome ◽  
Sccmec Type ◽  
Opportunistic Pathogen ◽  
Epidemiological Surveillance ◽  
Skin Infections ◽  
Staphylococcus Pseudintermedius ◽  
Significant Difference ◽  
Type V

Background: Staphylococcus pseudintermedius is a part of the canine skin microflora and an opportunistic pathogen. It plays a central role in canine pyoderma, otitis and surgical wound infections. These conditions correlate with virulence genes distributed in the bacterial genome. These genes determine strain variability on typing, in turn aiding epidemiological surveillance. The aim of this study was to isolate, identify and characterize Staphylococcus pseudintermedius (SP) and Methicillin resistant Staphylococcus pseudintermedius (MRSP) from dogs with skin infections in Chennai, India. Methods: SP and MRSP positive isolates were identified by multiplex PCR for nuc and mecA genes respectively. Characterization of the isolates for virulence genes responsible for biofilm formation (icaA, icaD), cell wall adherence (SpsO, SpsK, SpsP, SpsQ, SpsF), toxins (ExpA, ExpB, SIET, Sel, Se-int, LukS, LukF) and gene regulation (Agr, SarA) was performed. Result: Out of 275 samples, 120 SP and 8 MRSP positive isolates were identified. Only one isolate could be typed as SCCmec Type V whereas other MRSP isolates were non typeable. Agr typing of MRSP isolates revealed type II in 7 isolates and type III in one isolate. Our study revealed that there was no significant difference in the detection of virulence genes between MSSP and MRSP.

scholarly journals Influence of the Protein Kinase C Activator Phorbol Myristate Acetate on the Intracellular Activity of Antibiotics against Hemin- and Menadione-Auxotrophic Small-Colony Variant Mutants of Staphylococcus aureus and Their Wild-Type Parental Strain in Human THP-1 Cells

2012 ◽  
Vol 56 (12) ◽  
pp. 6166-6174 ◽  
Author(s):  
Laetitia G. Garcia ◽  
Sandrine Lemaire ◽  
Barbara C. Kahl ◽  
Karsten Becker ◽  
Richard A. Proctor ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Parental Strain ◽  
Wild Type ◽  
Content Type ◽  
Small Colony Variant ◽  
Intracellular Activity ◽  
Kinase C ◽  
Pharmacodynamic Profile ◽  
Small Colony ◽  
Intracellular Fate

ABSTRACTIn a previous study (L. G. Garcia et al., Antimicrob. Agents Chemother. 56:3700–3711, 2012), we evaluated the intracellular fate ofmenDandhemBmutants (corresponding to menadione- and hemin-dependent small-colony variants, respectively) of the parental COL methicillin-resistantStaphylococcus aureusstrain and the pharmacodynamic profile of the intracellular activity of a series of antibiotics in human THP-1 monocytes. We have now examined the phagocytosis and intracellular persistence of the same strains in THP-1 cells activated by phorbol 12-myristate 13-acetate (PMA) and measured the intracellular activity of gentamicin, moxifloxacin, and oritavancin in these cells. Postphagocytosis intracellular counts and intracellular survival were lower in PMA-activated cells, probably due to their higher killing capacities. Gentamicin and moxifloxacin showed a 5- to 7-fold higher potency (lower static concentrations) against the parental strain, itshemBmutant, and the genetically complemented strain in PMA-activated cells and against themenDstrain in both activated and nonactivated cells. This effect was inhibited when cells were incubated withN-acetylcysteine (a scavenger of oxidant species). In parallel, we observed that the MICs of these drugs were markedly reduced if bacteria had been preexposed to H2O2. In contrast, the intracellular potency of oritavancin was not different in activated and nonactivated cells and was not decreased by the addition ofN-acetylcysteine, regardless of the phenotype of the strains. The oritavancin MIC was also unaffected by preincubation of the bacteria with H2O2. Thus, activation of THP-1 cells by PMA may increase the intracellular potency of certain antibiotics (probably due to synergy with reactive oxygen species), but this effect cannot be generalized to all antibiotics.

scholarly journals Adaptation Genomics of a Small-Colony Variant in a Pseudomonas chlororaphis 30-84 Biofilm

2014 ◽  
Vol 81 (3) ◽  
pp. 890-899 ◽  
Author(s):  
Dongping Wang ◽  
Robert J. Dorosky ◽  
Cliff S. Han ◽  
Chien-chi Lo ◽  
Armand E. K. Dichosa ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Genetic Alterations ◽  
Whole Genome Sequence ◽  
Phenotypic Switching ◽  
Whole Genome ◽  
Pseudomonas Chlororaphis ◽  
Wild Type ◽  
Content Type ◽  
Small Colony Variant ◽  
Small Colony

ABSTRACTThe rhizosphere-colonizing bacteriumPseudomonas chlororaphis30-84 is an effective biological control agent against take-all disease of wheat. In this study, we characterize a small-colony variant (SCV) isolated from aP. chlororaphis30-84 biofilm. The SCV exhibited pleiotropic phenotypes, including small cell size, slow growth and motility, low levels of phenazine production, and increased biofilm formation and resistance to antimicrobials. To better understand the genetic alterations underlying these phenotypes, RNA and whole-genome sequencing analyses were conducted comparing an SCV to the wild-type strain. Of the genome's 5,971 genes, transcriptomic profiling indicated that 1,098 (18.4%) have undergone substantial reprograming of gene expression in the SCV. Whole-genome sequence analysis revealed multiple alterations in the SCV, including mutations inyfiR(cyclic-di-GMP production),fusA(elongation factor), andcyoE(heme synthesis) and a 70-kb deletion. Genetic analysis revealed that theyfiRlocus plays a major role in controlling SCV phenotypes, including colony size, growth, motility, and biofilm formation. Moreover, a point mutation in thefusAgene contributed to kanamycin resistance. Interestingly, the SCV can partially switch back to wild-type morphologies under specific conditions. Our data also support the idea that phenotypic switching inP. chlororaphisis not due to simple genetic reversions but may involve multiple secondary mutations. The emergence of these highly adherent and antibiotic-resistant SCVs within the biofilm might play key roles inP. chlororaphisnatural persistence.

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