Effect of biofilm formation on the survival of Acinetobacter baumannii on dry surfaces

doi:10.1016/j.jhin.2011.08.013

Journal of Hospital Infection

Volume 80, Issue 1, January 2012, Pages 56-60

https://doi.org/10.1016/j.jhin.2011.08.013 Get rights and content

Summary

Background

Acinetobacter baumannii is emerging as an important hospital pathogen, which can persist in the environment for extended periods of time. It is known to produce biofilms, a community of bacteria enclosed within a protective polymeric matrix.

Aim

To establish whether the effect of biofilm formation by Acinetobacter baumannii may be associated with persistence in the hospital environment.

Methods

The effect of biofilm formation on the survival of A. baumannii on dry surfaces was investigated in biofilm-forming compared to non-biofilm-forming strains. Survival assays were determined by viable counts of the cells inoculated on to glass cover slips and stored under controlled conditions of temperature and relative humidity.

Findings

The survival times for the biofilm-forming strains were longer than for the non-biofilm-forming ones (36 vs 15 days, respectively, P < 0.001). Scanning and transmission electron microscopy studies showed a polysaccharide layer and appendages in the biofilm-forming strains, not in the non-biofilm forming ones.

Conclusion

Biofilm formation increases the survival rate of A. baumannii on dry surfaces and may contribute to its persistence in the hospital environment, increasing the probability of causing nosocomial infections and outbreaks.

Introduction

Acinetobacter baumannii is an important pathogen capable of causing nosocomial infections, including pneumonia, wound and urinary tract infections, bacteraemia, and meningitis, especially in patients in the intensive care unit.1, 2 These organisms, which are ubiquitous within the environment, are generally found in soil, water, human skin, food products and medical devices.3, 4, 5, 6 A. baumannii can survive on fingertips and inanimate objects such as glass, plastic and other environmental surfaces, even after exposure to dry conditions, during extended periods of time, and the environment has been implicated as a transmission route in some outbreaks.7, 8, 9

The survival of A. baumannii has also been attributed to resistance of this micro-organism to antimicrobial drugs and desiccation.4, 5 Since A. baumannii can produce biofilm, the resistance phenotype could be attributed to the ability of A. baumannii clinical strains to form biofilms on abiotic surfaces.5, 10, 11

Bacteria in a biofilm, as a structural community, are enclosed in a polymeric matrix constituting a protective mechanism to survive in harsh environments and during host infection. These bacteria become more resistant to antimicrobial stressors, antibiotics or cleaning and therefore this biofilm structure represents an important virulence factor.10, 12, 13 To understand the effect of biofilm formation on the persistence of Acinetobacter on dry surfaces, we performed survival assays with biofilm-forming and non-biofilm-forming strains on glass cover slips in a desiccated environment and analysed the structure of the resulting biofilms.

Section snippets

Bacterial strains

We selected four isolates, two biofilm-forming and two non-biofilm-forming ones, from a set of 92 clonally unrelated isolates from a collection of 221 A. baumannii clinical isolates collected during the GEIH-Ab 2000 project.⁸ In this study it was found that all clonally related isolates shared either an ability or an inability to form biofilm. Accordingly, the isolates for the present study were clonally unrelated and randomly selected. Susceptibility of the isolates to antimicrobial agents was

Results

The ability of strains Ab033 and Ab053 to form biofilm, and the inability of strains Ab001 and Ab143 to form biofilm was confirmed by Crystal Violet staining. The means of the duplicate OD₆₀₀ values were: strain Ab033 (1.814), Ab053 (2.174), Ab001 (0.24), Ab143 (0.109). The interpretation for these OD values is: biofilm negative (<0.4), low biofilm-forming (0.4–1), and strong biofilm-forming (>1.5).

Biofilm-forming strains were less resistant to almost all the antimicrobials than their

Discussion

A. baumannii is an important opportunistic pathogen, with the ability to colonize and persist in the hospital setting and on medical devices, and also constitutes a significant problem in intensive care units.3, 16 This micro-organism survives on nutrient-limited surfaces for several days and is also capable of resisting desiccation and disinfection.4, 6, 17 It is hypothesized that its ability to persist in these environments, as well as its virulence, is a result of its capacity to form

Acknowledgements

This study has been supported by the Spanish Ministry of Health (FIS 08/0195 to J.V.), by 2009 SGR 1256 from the Departament de Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya, the Ministerio de Sanidad y Consumo, Instituto de Salud Carlos III, Spanish Network for the Research in Infectious Disease (REIPI 06/0008), and by funding from the European Community (TROCAR contract HEALTH-F3-2008-223031). We want to thank the AlBan programme E07D401559CO for supporting

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View full text

Effect of biofilm formation on the survival of Acinetobacter baumannii on dry surfaces

Summary

Background

Aim

Methods

Findings

Conclusion

Introduction

Section snippets

Bacterial strains

Results

Discussion

Acknowledgements

J Hosp Infect

Clin Microbiol Infect

Indian J Med Microbiol

Clin Microbiol Infect

Acinetobacter spp as nosocomial pathogens: microbiological, clinical and epidemiological features

Clin Microbiol Rev

Survival of Acinetobacter baumannii on dry surfaces: comparison of outbreak and sporadic isolates

J Clin Microbiol

Attachment to and biofilm formation on abiotic surfaces by Acinetobacter baumannii: involvement of a novel chaperone-usher pili assembly system

Microbiology

Inﬂuence of relative humidity and suspending menstrua on survival of Acinetobacter spp. on dry surfaces

J Clin Microbiol

Survival of Acinetobacter baumannii on dry surfaces

J Clin Microbiol

Regulation of Acinetobacter baumannii biofilm formation

Future Microbiol