Staphylococcus aureus dry-surface biofilms are not killed by sodium hypochlorite: implications for infection control

A. Almatroudi, I. B. Gosbell, H. Hu, S. O. Jensen, B. A. Espedido, S. Tahir, T. O. Glasbey, P. Legge, G. Whiteley, A. Deva, K. Vickery

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Background: Dry hospital environments are contaminated with pathogenic bacteria in biofilms, which suggests that current cleaning practices and disinfectants are failing. Aim: To test the efficacy of sodium hypochlorite solution against Staphylococcus aureus dry-surface biofilms. Methods: The Centers for Disease Control and Prevention Biofilm Reactor was adapted to create a dry-surface biofilm, containing 1.36 × 107 S. aureus/coupon, by alternating cycles of growth and dehydration over 12 days. Biofilm was detected qualitatively using live/dead stain confocal laser scanning microscopy (CLSM), and quantitatively with sonicated viable plate counts and crystal violet assay. Sodium hypochlorite (1000-20,000parts per million) was applied to the dry-surface biofilm for 10min, coupons were rinsed three times, and residual biofilm viability was determined by CLSM, plate counts and prolonged culture up to 16 days. Isolates before and after exposure underwent minimum inhibitory concentration (MIC) and minimum eradication concentration (MEC) testing, and one pair underwent whole-genome sequencing. Findings: Hypochlorite exposure reduced plate counts by a factor of 7 log10, and reduced biofilm biomass by a factor of 100; however, staining of residual biofilm showed that live S. aureus cells remained. On prolonged incubation, S. aureus regrew and formed biofilms. Post-exposure S. aureus isolates had MICs and MECs that were not significantly different from the parent strains. Whole-genome sequencing of one pre- and post-exposure pair found that they were virtually identical. Conclusions: Hypochlorite exposure led to a 7-log kill but the organisms regrew. No resistance mutations occurred, implying that hypochlorite resistance is an intrinsic property of S. aureus biofilms. The clinical significance of this warrants further study.

LanguageEnglish
Pages263-270
Number of pages8
JournalJournal of Hospital Infection
Volume93
Issue number3
DOIs
Publication statusPublished - 1 Jul 2016

Fingerprint

Sodium Hypochlorite
Biofilms
Infection Control
Staphylococcus aureus
Hypochlorous Acid
Confocal Microscopy
Genome
Gentian Violet
Disinfectants
Microbial Sensitivity Tests
Centers for Disease Control and Prevention (U.S.)
Dehydration
Biomass
Coloring Agents

Keywords

  • biofilms
  • disinfectants
  • dry-surface biofilms
  • healthcare-associated infections
  • hospital cleaning
  • infection control
  • sodium hypochlorite
  • staphylococcus aureus

Cite this

Almatroudi, A. ; Gosbell, I. B. ; Hu, H. ; Jensen, S. O. ; Espedido, B. A. ; Tahir, S. ; Glasbey, T. O. ; Legge, P. ; Whiteley, G. ; Deva, A. ; Vickery, K. / Staphylococcus aureus dry-surface biofilms are not killed by sodium hypochlorite : implications for infection control. In: Journal of Hospital Infection. 2016 ; Vol. 93, No. 3. pp. 263-270.
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Staphylococcus aureus dry-surface biofilms are not killed by sodium hypochlorite : implications for infection control. / Almatroudi, A.; Gosbell, I. B.; Hu, H.; Jensen, S. O.; Espedido, B. A.; Tahir, S.; Glasbey, T. O.; Legge, P.; Whiteley, G.; Deva, A.; Vickery, K.

In: Journal of Hospital Infection, Vol. 93, No. 3, 01.07.2016, p. 263-270.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Staphylococcus aureus dry-surface biofilms are not killed by sodium hypochlorite

T2 - Journal of Hospital Infection

AU - Almatroudi, A.

AU - Gosbell, I. B.

AU - Hu, H.

AU - Jensen, S. O.

AU - Espedido, B. A.

AU - Tahir, S.

AU - Glasbey, T. O.

AU - Legge, P.

AU - Whiteley, G.

AU - Deva, A.

AU - Vickery, K.

PY - 2016/7/1

Y1 - 2016/7/1

N2 - Background: Dry hospital environments are contaminated with pathogenic bacteria in biofilms, which suggests that current cleaning practices and disinfectants are failing. Aim: To test the efficacy of sodium hypochlorite solution against Staphylococcus aureus dry-surface biofilms. Methods: The Centers for Disease Control and Prevention Biofilm Reactor was adapted to create a dry-surface biofilm, containing 1.36 × 107 S. aureus/coupon, by alternating cycles of growth and dehydration over 12 days. Biofilm was detected qualitatively using live/dead stain confocal laser scanning microscopy (CLSM), and quantitatively with sonicated viable plate counts and crystal violet assay. Sodium hypochlorite (1000-20,000parts per million) was applied to the dry-surface biofilm for 10min, coupons were rinsed three times, and residual biofilm viability was determined by CLSM, plate counts and prolonged culture up to 16 days. Isolates before and after exposure underwent minimum inhibitory concentration (MIC) and minimum eradication concentration (MEC) testing, and one pair underwent whole-genome sequencing. Findings: Hypochlorite exposure reduced plate counts by a factor of 7 log10, and reduced biofilm biomass by a factor of 100; however, staining of residual biofilm showed that live S. aureus cells remained. On prolonged incubation, S. aureus regrew and formed biofilms. Post-exposure S. aureus isolates had MICs and MECs that were not significantly different from the parent strains. Whole-genome sequencing of one pre- and post-exposure pair found that they were virtually identical. Conclusions: Hypochlorite exposure led to a 7-log kill but the organisms regrew. No resistance mutations occurred, implying that hypochlorite resistance is an intrinsic property of S. aureus biofilms. The clinical significance of this warrants further study.

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KW - biofilms

KW - disinfectants

KW - dry-surface biofilms

KW - healthcare-associated infections

KW - hospital cleaning

KW - infection control

KW - sodium hypochlorite

KW - staphylococcus aureus

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