Use of sodium dichloroisocyanurate for floor disinfection

Letters to the Editor for local anti-infective treatment and surface decontamination.8 It can be concluded from this study that the echovirus type 1 strain Farouk is be not suitable for the substitution of the poliovirus type 1 vaccine strain for virucidal testing of disinfectants since this strain can be considered less stable than the poliovirus against several important chemical biocides.

Conflict of interest statement None declared.

279 b

Institute for Medical Statistics, Computer Sciences and Documentation, Friedrich-Schiller University, Jena, Germany E-mail address: Andreas.Sauerbrei@med. uni-jena.de Available online 30 May 2009 * Corresponding author. Address: Institute of Virology and Antiviral Therapy, Friedrich-Schiller University of Jena, HansKno ¨ll-Straße 2, D-07745 Jena, Germany. Tel.: þ3641 9395700; fax: þ3641 9395701.

Funding sources

ª 2009 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.

None.

doi:10.1016/j.jhin.2009.04.003

References 1. Leitlinie der Deutschen Vereinigung zur Beka ¨mpfung der Viruskrankheiten (DVV) e.V. und des Robert Koch-Instituts (RKI) zur Pru ¨fung von chemischen Desinfektionsmitteln auf Wirksamkeit gegen Viren in der Humanmedizin, Fassung vom 1 August 2008. Bundesgesundheitsbl Gesundheitsforsch Gesundheitsschutz 2008;51:937e45. 2. Wutzler P, Sauerbrei A. Virucidal efficacy of a combination of 0.2% peracetic acid and 80% (v/v) ethanol (PAA-ethanol) as a potential hand disinfectant. J Hosp Infect 2000;46: 304e8. 3. Wutzler P, Sauerbrei A. Virucidal activity of the new disinfectant monopercitric acid. Lett Appl Microbiol 2004;39: 194e8. 4. Sauerbrei A, Sehr K, Brandsta ¨dt A, Heim A, Reimer K, Wutzler P. Sensitivity of human adenoviruses to different groups of chemical biocides. J Hosp Infect 2004;57: 59e66. 5. European Committee for Standardisation. Chemical disinfectants and antiseptics e Virucidal quantitative suspension test for chemical disinfectants and antiseptics used in human medicine e Test method and requirements (phase 2, step 1); German version EN 14476:2005/prA1:2006. 6. Kampf G, Steinmann J, Rabenau H. Suitability of vaccinia virus and bovine viral diarrhea virus (BVDV) for determining activities of three commonly-used alcohol-based rubs against enveloped viruses. BMC Infect Dis 2007;7:5. 7. Robert-Koch Institut. Liste der vom Robert Koch-Institut gepru ¨ften und anerkannten Desinfektionsmittel und -verfahren. Bundesgesundheitsbl Gesundheitsforsch Gesundheitsschutz 2007;10:1353e6. 8. Reimer K, Wichelhaus TA, Scha ¨fer V, et al. Antimicrobial effectiveness of povidone-iodine and consequences for new application areas. Dermatology 2002;204(Suppl. 1): 114e20.

A. Sauerbreia,* W. Eschricha A. Brandsta ¨dtb P. Wutzlera a Institute of Virology and Antiviral Therapy, Friedrich-Schiller University, Jena, Germany

Use of sodium dichloroisocyanurate for floor disinfection

Madam, There is little doubt that pathogens such as Staphylococcus aureus can survive on surfaces in close proximity to patients.1 Cleaning and disinfection regimens have been encouraged to minimise pathogen spread, but we do not know whether these organisms are susceptible to the disinfectants being applied to surfaces in hospitals.2 We initiated a preliminary surveillance programme to investigate the susceptibility of meticillinresistant (MRSA) or -susceptible (MSSA) S. aureus to surface disinfectants used in intensive therapy units (ITUs) in Wales. We now report on the efficacy of sodium dichloroisocyanurate (NaDCC), an agent used to disinfect floors in one ITU. We assessed the inhibitory effect of NaDCC using a broth microdilution method and then its bactericidal efficacy on surfaces using a carrier test based on the British Standard EN 13697.3,4 S. aureus strains from clinically infected ITU patients were provided by the Welsh Hospital where the biocide is currently in use. The culture collection strain NCIMB 9518 was also used as a ‘susceptible’ counterpart strain. S. aureus was inoculated onto steel discs (20 mL; 6.2e6.7 log10 cfu) with (3 g/L bovine serum albumin, BSA) or without (0.3 g/L BSA) organic load and dried for 25 min at 37  C. NaDCC tablets (Haz-Tabs) were obtained from Guest Medical (Edenbridge, Kent, UK) and solutions were made up using sterilised tap water from the ITU following the manufacturer’s instructions. An aliquot (100 mL) of NaDCCsolution was placed onto the test surface,

280

Letters to the Editor

Table I Susceptibility of intensive therapy unit clinical strains of MSSA and MRSA to sodium dichloroisocyanurate (NaDCC) Bacterial strains

NaDCC (1000 ppm) Clean conditions

NaDCC (1000 ppm) Dirty conditions

Contact time (s)

Mean (SE) log10 reduction factor

Contact time (s)

MSSA 13

30

5.78 (0.03)

14

30

5.56 (0.16)

47

30

6.54 (0.02)

51

30

6.46 (0.03)

30 60 30 60 30 60 30 60

30

5.11 (0.01)

49

30

6.16 (0.01)

52

30

5.99 (0.02)

55

30

6.17 (0.05)

30

6.39 (0.06)

MRSA 17

Standarda 9518

60 120 30

Mean (SE) log10 reduction factor 3.85 5.96 2.10 6.16 2.45 6.46 2.76 5.26

NaDCC (500 ppm) Dirty conditions Contact time (s)

Mean log10 reduction factor (SEa)

(1.26) (0.21) (0.21) (0.19) (0.49) (0.18) (0.88) (1.18)

120 210 120 210 120 210 120 210

2.24 6.01 2.85 6.22 2.57 5.77 2.37 6.28

3.46 (1.12) 5.93 (0.07) 5.81 (0.66)

2.48 (0.43) 5.8 (0.06) 1.95 (0.12) 6.1 (0.04) 2.25 (0.04) 6.13 (0.01) 2.14 (0.18) 6.14 (0.08) 2.39 (0.24) 5.91 (0.06)

30 60 30 60

1.75 6.14 5.22 6.41

(1.02) (0.05) (0.96) (0.14)

120 210 120 210 120 210 120 210

30 60

2.27 (1.01) 6.19 (0.06)

120 210

(0.12) (0.02) (0.71) (0.24) (0.77) (0.2) (0.1) (0.11)

NCIMB, National Collection of Industrial and Marine Bacteria; MRSA/MSSA, meticillin-resistant or -susceptible S. aureus. Mean data from three experimental replicates are presented. a Standard strain S. aureus NCIMB 9518.

whereas 100 mL of sterilised tap water from the ITU was placed onto the control surface, ensuring that dried inocula were totally covered. After NaDCC exposures (30 s, 1 min, 2 min, 3.5 min and 5 min) steel discs were transferred to neutraliser (sodium thiosulphate 5 g/L) and the remaining bacteria resuspended and counted. Log10 cell reductions were calculated by subtracting the mean log10 number of cells recovered from the discs treated with disinfectant from the mean log10 number of survivors treated with water. Bacteria were exposed to disinfectant until a bactericidal effect (>4 log10 reduction in cell number) was achieved.4 The broth dilution method revealed that minimum concentrations of NaDCC of up to 400 ppm were needed to inhibit MRSA/MSSA strains.3 These results were initially alarming since the minimum inhibitory concentrations were close to the recommended ‘in-use’ concentration of 1000 ppm. Therefore, in subsequent carrier tests we tested a dilute 500 ppm solution as well as the in-use concentration. When 1000 ppm was applied to clean surfaces contaminated with S. aureus strains,

NaDCC achieved a bactericidal effect after 30 s (Table I). We observed a difference in inactivation kinetics between individual strains when experiments were conducted under dirty conditions, particularly among the MRSA strains, although all isolates remained susceptible to exposures of 2 min. Considerably longer contact times (3.5 min) were required when the strains were exposed to a dilute 500 ppm solution in the presence of an organic load. Some reports have suggested that MRSA might be more resilient than MSSA to disinfection.5,6 Overall we found no difference in susceptibility between MSSA and MRSA. The results suggest that the activity of NaDCC is noticeably affected by concentration, contact time and the presence of organic load. It is important to ensure that NaDCC is made up to the correct concentration and, once applied to the floors, it must stay in contact for 2 min to achieve the optimum kill. The significance of these results depends upon the regimens currently in place. In this particular Welsh ITU, routine cleaning protocols include the application of a general purpose cleaning solution to floors using a mop.

Letters to the Editor After the floor has dried in the ambient ITU conditions, NaDCC is then applied, also with a mop, around the beds of patients infected with MSSA or MRSA and the floor is again left to dry. The drying process takes >2 min, which in theory suggests that the optimum microbial kill will be achieved. However, it must be noted that as the solution dries on the floor, the concentration of active chlorine is likely to decrease. Such an event is difficult to mimic in laboratory experiments without the knowledge of the fate of NaDCC on the floor when applied with a mop. In addition, mops treated with detergents and disinfectant solutions can become contaminated with pathogenic microbes and have the potential to redistribute the organisms across floors.7 Do mops soaked in NaDCC possess the ability to effectively remove, kill and prevent the mechanical spread of bacteria across the floor? The development of more complete tests that mimic the application of biocides in situ is needed to properly evaluate their efficacy in practice. The simple test used in this study, however, re-emphasises the need to ensure the appropriate application and contact time are observed in practice. Failure to do so increases the potential for bacterial survival.

Conflict of interest statement None declared.

281 resistant Staphylococcus aureus (MRSA). J Hosp Infect 1998;38:297e303. 6. Block C, Robenshtok E, Simhon A, Shapiro M. Evaluation of chlorhexidine and povidone iodine activity against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis using a surface test. J Hosp Infect 2000;46:147e52. 7. Dharan S, Mourouga P, Copin P, Bessemer G, Tschanz B, Pittet D. Routine disinfection of patients’ environmental surfaces, myth or reality? J Hosp Infect 1999;42:113e7.

G.J. Williamsa,* S.P. Denyera I.K. Hoseinb D.W. Hillc J.-Y. Maillarda a Welsh School of Pharmacy, Cardiff University, Cardiff, UK b Microbiology Department, North Middlesex University Hospital NHS Trust, London, UK c Infection Prevention and Control Department, Cardiff and Vale NHS Trust, Cardiff, UK E-mail address: [email protected] Available online 18 March 2009 * Corresponding author. Address: Welsh School of Pharmacy, Cardiff University, Redwood Building, King Edward VII Avenue, Cardiff CF10 3NB, UK. Tel.: þ44 02920 879088; fax: þ44 02920 874149. ª 2009 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.

Funding sources Wales Office of Research and Development for Health and Social Care (WORD).

doi:10.1016/j.jhin.2009.02.017

Should laparoscopic surgeons wear masks?

References 1. Kramer A, Schwebke I, Kampf G. How long do nosocomial pathogens persist on inanimate surfaces? A systematic review. BMC Infect Dis 2006;6:130. 2. Coia JE, Duckworth GJ, Edwards DI, et al. Guidelines for the control and prevention of meticillin-resistant Staphylococcus aureus (MRSA) in healthcare facilities. J Hosp Infect 2006; 63(Suppl. 1):S1e44. 3. Clinical and Laboratory Standards Institute. Approved Standard M7eA7: Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically. 7th ed. Wayne, PA: CLSI; 2006. 4. BSEN 13697 (European Standard). Chemical disinfectants and antiseptics e Quantitative non-porous surface test for the evaluation of bactericidal and/or fungicidal activity of chemical disinfectants used in food, industrial, domestic and institutional areas e Test method and requirements without mechanical action (phase 2/step2). European Standard EN, 13697; 2001. 5. Kampf G, Jarosch R, Ruden H. Limited effectiveness of chlorhexidine based hand disinfectants against methicillin-

Madam, The use of face masks to protect the patient from airborne pathogens carried by the surgical team was first advocated just over a century ago, although since then the evidence produced to support their use as an infection control measure has not been robust.1 In recent times, masks have been used increasingly to protect operating theatre staff from bloodborne viruses carried by the patients. Surgery has also moved away from open procedures towards minimal access and natural orifice techniques, where cavities and organs are distended with media to allow inspection of their contents. Media such as saline, glycine and carbon dioxide must then be expelled from the body and it is during this phase of the procedure