Small changes in environmental parameters lead to alterations in antibiotic resistance, cell morphology and membrane fatty acid composition in Staphylococcus lugdunensis

• Staphylococcus lugdunensis has emerged as a major cause of community-acquired and nosocomial infections. This bacterium can rapidly adapt to changing environmental conditions to survive and capitalize on opportunities to colonize and infect through wound surfaces. It was proposed that S. lugdunensis would have underlying alterations in metabolic homeostasis to provide the necessary levels of adaptive protection. The aims of this project were to examine the impacts of subtle variations in environmental conditions on growth characteristics, cell size and membrane fatty acid composition in S. lugdunensis. Liquid broth cultures of S. lugdunensis were grown under varying combinations of pH (6-8), temperature (35-39°C) and osmotic pressure (0-5% sodium chloride w/w) to reflect potential ranges of conditions encountered during transition from skin surfaces to invasion of wound sites. The cells were harvested at the mid-exponential phase of growth and assessed for antibiotic minimal inhibitory concentration (MIC), generation time, formation of small colony variants, cell size (by scanning electron microscopy) and membrane fatty acid composition. Stress regimes with elevated NaCl concentrations resulted in significantly higher antibiotic resistance (MIC) and three of the combinations with 5% NaCl had increased generation times (P<0.05). It was found that all ten experimental growth regimes, including the control and centroid cultures, yielded significantly different profiles of plasma membrane fatty acid composition (P<0.0001). Alterations in cell size (P<0.01) were also observed under the range of conditions with the most substantial reduction occurring when cells were grown at 39°C, pH 8 (514±52 nm, mean ± Standard Deviation) compared with cells grown under control conditions at 37°C with pH 7 (702±76 nm, P<0.01). It was concluded that S. lugdunensis responded to slight changes in environmental conditions by altering plasma membrane fatty acid composition, growth rates and morphology to achieve optimal adaptations for survival in changing environments. © 2014 Crompton et al.

Ämnesord

NATURVETENSKAP  -- Biologi -- Mikrobiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Microbiology (hsv//eng)

Nyckelord

antibiotic agent

fatty acid

gentamicin

sodium chloride

antiinfective agent

adaptation

antibiotic resistance

antibiotic sensitivity

article

bacterial colonization

bacterial growth

bacterial membrane

bacterial survival

cell size

colony formation

controlled study

environmental stress

growth curve

growth rate

lipid composition

liquid culture

microbial morphology

minimum inhibitory concentration

nonhuman

osmotic pressure

pH

scanning electron microscopy

skin surface

Staphylococcus lugdunensis

temperature sensitivity

wound

cytology

drug effects

human

metabolism

microbiology

physiology

Staphylococcal Infections

temperature

Anti-Bacterial Agents

Drug Resistance

Microbial

Fatty Acids

Gentamicins

Humans

Hydrogen-Ion Concentration

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