Antimicrobial Efficacy

Antimicrobial efficacy is the rate in which microbes, such as harmful bacteria, are destroyed by antimicrobial agents. Products with kill log rates are typically illustrated on a logarithmic scale from 90% to 99.99999%, with each level separated by multiples of ten.

When compared by this scale, users cannot see the whole picture of the remaining bacteria present after product use. For example, PrimeOn Hand Sanitiser has a 7 kill log rate (99.99999%), which means that if 10,000,000 bacteria on hands are present, this antimicrobial agent can bring the bacteria down to 1 (refer to Figure 1).

Figure 1. Breakdown of kill log and microbial reduction rate from 10,000,000 bacteria

Percentage-of-Microbial-Reduction-Pyramid

High Touch Surfaces

According to National Academy of Engineering and National Academies of Sciences, Engineering, and Medicine (2017), the high touch surfaces and bacterial reservoirs in hospitals are deeply connected to the flow of patients and staff. With multiple touch points in the surrounding environment of a hospital, an alarming number of healthcare associated infections (HAIs) originate from surface transmission between healthcare workers and patients (Smith et al. 2013).

Patient-room

1. Patient Room

Bed rails and bedside table, tray table, call boxes, phone, patient chair, IV pole, floor, light switches, glove box, air and exhaust filter

Patient-bathroom

2. Patient Bathroom

Sink, faucet handles and inside faucet head, tap water (hot and cold), light switches, door knob, handrails, toilet seats, flush lever, bed pan cleaning equipment, floor, air and exhaust filter

Medical-equipment

3. Medical Equipment

Control panels (IV pump, monitor, ventilator), monitor touch screen and cables, blood pressure cuff, janitorial equipment

Water

4. Water

Tap water (hot and cold) and water for cleaning floors

Patient

5. Patient

Faecal matter, nasal swab, hand contact

Healthcare-workers

6. Healthcare Workers

Nasal swab, bottom of shoe, dominant hand, technology (cell phone, pager, iPad, work phone), computer mouse, shirt cuff, stethoscope

Traffic-areas

7. Traffic areas

Corridor floor and wall, steps, stairwell door knobs, stairwell door kick plates, elevator buttons and floor, handrails, air

Waiting-area

8. Waiting area

Front desk surface, chairs, coffee tables, floor, air

Public-bathroom

9. Public Bathroom

Floor, door handles, sink controls and bowl, soap dispenser, towel dispenser, toilet seats, flush levers, stall door handle and lock, air and exhaust filter

In addition to the high touch surface areas that predominantly fall within the patient’s room, are the workstations circulated by healthcare staff. According to a study conducted at Bonn University Hospital in Germany, 32% of computer user interfaces were identified as positive for pathogenic microorganisms (refer to Table 1), with the highest contamination rates recorded after immediate use by healthcare workers (Engelhart et al. 2008).

 

Table 1: Microbial contamination of PC workstations in a university hospital, based on 300 samples collected from 100 computer user interfaces (keyboard and mouse) (Engelhart et al. 2008)

Microorganisms Positive Samples Cfu / 25 cm2Positive workstations
n%MittelMediann(=%)
Staphylococcus aureus196261212
Coagulase-negative staphylococci27391161296
Micrococcus spp.219738496
Viridans streptococci1554111
Enterococci83538
Bacillus spp.220736396
Gram-negative bacteria1962114
Acinetobacter*1248
Other non-fermenters**414
Enterobacteriaceae313
Moulds ***34111125
* Acinetobacter species, 4; A. baumannii, 5; A. lwoffii, 2; A. junii/johnsonii, 1
** Chryseomonas luteola, 2; Pseudomonas stutzeri, 2
*** Aspergillus fumigatus, 25; Aspergillus niger, 9; Paecilomyces variotii, 1; Geomyces pannorum, 1

Eliminating Bacteria

Finding the right product to eliminate bacteria and viruses requires more than comparing the log-reduction rate. Both the CDC and EPA encourage the use of EPA-registered products for disinfecting different types of surfaces in healthcare environments (Quinn et al. 2015).

The quantity of microbes on any given surface is subject to change, based on temperature conditions, surface material (smooth or rough), type of surface cleaner and disinfectant used, frequency of surface cleaning and disinfection, and the availability of hand hygiene products.

References

  1. Engelhart, S, Fischnaller, E, Simon, A, Gebel, J, Büttgen, S and Exner, M 2008, ‘Microbial contamination of computer user interfaces (keyboard, mouse) in a tertiary care centre under conditions of practice’, Hygiene + Medizin, vol. 33, pp. 504-507, Academic Search Complete Database, Semantic Scholar
  2. National Academy of Engineering and National Academies of Sciences, Engineering, and Medicine 2017, Microbiomes of the Built Environment: A Research Agenda for Indoor Microbiology, Human Health, and Buildings, The National Academies Press, viewed 7 January 2019, < https://www.nap.edu/catalog/23647/microbiomes-of-the-built-environment-a-research-agenda-for-indoor>
  3. Smith, D. P, Alverdy, J. C, Siegel, J. A and Gilbert J. A 2013, ‘Design considerations for home and hospital microbiome studies’ in The Science and Applications of Microbial Genomics: workshop summary, The National Academies Press, Washington, DC, pp. 169-171
  4. Quinn, M.M, Henneberger, P.K, Braun, B, Delclos, G.L, Fagan, K, Huang, V, Knaack, J.L.S et al. 2015, ‘Cleaning and disinfecting environmental surfaces in health care: Toward an integrated framework for infection and occupational illness prevention’, American Journal of Infection Control, vol. 43, no. 5, pp. 424-434, Academic Search Complete Database, ScienceDirect