1. Introduction
Infection control is extremely important in today’s healthcare settings due to increasing
numbers of antibiotic resistant pathogens. Although infection control has been successful
at decreasing numbers of common infections like MRSA, E.coli infections are still
continuing to increase[1].
The biggest mode of transmission of pathogens is via healthcare workers hands, and when
they touch surfaces they can transfer the pathogens to patients, which can lead to a fatal
infection [2].
Copper exhibits many antimicrobial properties (figure 1)[3]. Its use in healthcare settings
could be a possible preventative strategy that could potentially minimise the number of
infections and help with the economical burden. Resistance to copper has not been
currently observed as of yet.
The aim of this investigation was to
observe the effect copper has on the
growth of pathogenic organisms. The
organism’s that commonly cause HAI’s
were used and include gram-positive
Streptococcus pneumoniae and MRSA,
gram-negative Haemophilus influenzae
and E.coli, and the yeast Candida albicans.
Methods
Minimum Inhibitory Concentration
Concentrations of copper (II) sulfate ranging from 25-10mM were used, and each bacteria
were incubated in appropriate broth for each concentration for 24 hours at 37°C . The
concentration displaying no turbidity, and therefore no growth determined the MIC.
Minimum Bactericidal Concentration
Each concentration was sub-cultured onto the appropriate agar (figure 2) and
Incubated for 24 hours at 37°C . The lowest concentration displaying no growth of colonies
determined the MBC.
Antibiotic Sensitivity
Copper concentrations of 0.25, 0.5 and 0.75mM were incorporated into appropriate agar
and bacterial inoculums for each organism were spread over the surface. Antibiotic discs
were then place onto the surface and the diameter of the zones of inhibition were
measured.
Results
Organism
MIC
Average/mM
C.albicans 16.5
MRSA 17.5
E.coli 13.5
S.Pneumoniae 12.5
Organism
MBC
Average/mM
C.albicans 14.50
MRSA 11.25
E.coli 12.50
S.Pneumoniae 24.75
Conc (mM) Diameter (mm)
Vancomycin Doxycycline
0.75 20 42
0.50 17 38
0.25 17 36
Control 16 35
Conc (mM) Diameter (mm)
Azithromycin Cefotaxime
0.75 28 48
0.50 28 47
0.25 27 44
Control 27 42
Discussion
Copper exhibited antimicrobial properties against the species used in this
investigation. It inhibited the growth and killed each species at relatively low
concentrations. There was a varied range for both the MIC and MBC with MRSA
having the lowest and Streptococcus having the highest. The varied range makes
it harder to apply copper universally to liquid based solutions such as cleaning
products and disinfectants as HAI’s are caused by a variety of pathogens,
therefore it would need to be individualised.
The antibiotic susceptibility investigations showed that copper had a synergistic
effect with the antibiotics, as seen with MRSA and Haemophilus. The zones
increased in size compared to the control with higher concentrations of copper
in the agar (0.75mM) which improved the antibiotic efficacy. An antagonistic
effect was seen with E.coli which means that antibiotics are still depended on for
effective eradication of infections. Further investigations into the growth of a
greater variety of pathogens, as well as performing a quantitative analysis of the
numbers of bacteria present using cytofluorometric techniques [4] on copper
surfaces are needed, especially within clinical settings.
Conc (mM) Diameter (mm)
Ceftriaxone Tetracycline
0.75 45 31
0.5 42 30
0.25 43 34
Control 50 39
Conc (mM) Diameter (mm)
Penicillin Rifampicin
0.75 11 31
0.50 10 30
0.25 10 28
Control 14 29
References
1. Public Health England, Annual Epidemiological Commentary: Mandatory MRSA, MSSA and E. coli bacteraemia and C. difficile infection data, 2014/15, 2015
2. Newitt S, Myles PR, Birkin JA, Maskell V, Slack RCB, Nguyen-Van-Tam JS, et al. Impact of infection control interventions on rates of Staphylococcus aureus
bacteraemia in National Health Service acute hospitals, East Midlands, UK, using interrupted time-series analysis. Journal of Hospital Infection.
2015;90(1):28-37
3. Emamifar A, Applications of Antimicrobial Polymer Nanocomposites in Food Packaging, Advances in Nanocomposite Technology, Dr. Abbass Hashim (Ed.),
InTech, 2011, ISBN: 978-953-307-347-7
4. Balouiri M, Sadiki M, Ibnsouda SK. Methods for in vitro evaluating antimicrobial activity: A review. Journal of Pharmaceutical Analysis.
Figure 1: The antimicrobial mechanisms of copper
Figure 2: Each concentration was
sub cultured onto the relevant
division of the agar plate, and
growth was observed.
Table 5: The MIC of the tested species
Table 6: The MBC of the tested species
Table 1: The zone diameters of H.influenzae Table 2: The zone diameters of MRSA
Table 3: The zone diameters of E.coli Table 4: The zone diameters of S.pneumoniae
Figure 3: A graph representing the trends of synergism seen between the concentration of copper and the antibiotic for S.pneumoniae (SP),
H.influenzae (HI) and MRSA.
0
10
20
30
40
50
60
Rifampicin Azithromycin Cefotaxime Vancomycin Doxycycline
S.P H.I MRSA
Diameter(mm)
Species and Antibiotics
A graph representing the trends of synergism seen between the concentration
of copper and the antibiotic for each species
0.25mM
0.5mM
0.75mM
Control

2. References
Figure 1:National Institute of Open Schooling, Antibiotic
Susceptibility Testing,
http://www.nos.org/media/documents/dmlt/Microbiology/Lesson-
12.pdf

3. Copper Surface Sampling
5x2cm strips of copper were placed in sterile
petri dishes and swabbed with the bacterial
suspensions. After 24, 48 and 72 hours, a
sample of the same surface area size was
taken using a swab and cultured onto the
relevant agar. Growth was observed after
incubation for 24 hours at 30 degrees.
Concentration (mM) Diameter (mm)
Penicillin Rifampicin
0.75 11 31
0.50 10 30
0.25 10 28
Control 14 29
Conc (mM) Diameter (mm)
Ceftriaxone Tetracycline
0.75 45 31
0.5 42 30
0.25 43 34
Control 50 39