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Survey of antibiotic resistance in cell phone and computerkeyboard isolated bacteriaAuthor(s): Lisa Ann Blankinship, Barbara L. Cotton, and Janet L. GastonSource: BIOS, 84(3):165-172. 2013.Published By: Beta Beta Beta Biological SocietyDOI: http://dx.doi.org/10.1893/0005-3155-84.3.165URL: http://www.bioone.org/doi/full/10.1893/0005-3155-84.3.165

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Research Article

Survey of antibiotic resistance in cell phone andcomputer keyboard isolated bacteria

Lisa Ann Blankinship1, Barbara L. Cotton2, and Janet L. Gaston2

1Department of Biology, University of North Alabama, Florence, AL 35632 and2Department of Biology, Troy University, Troy, AL 36082

Abstract. Surveillance and tracking of antibiotic resistant bacteria carried on common-use items

will help to elucidate the prevalence of antibiotic resistance within communities. Communication

of these data will allow healthcare agencies and basic researchers to better plan mechanisms for

combatting the problem of antibiotic resistance. During this project, samples were collected from

public access computer keyboards and personal cell phones of the faculty, staff, and students at

Troy University in Troy, Alabama. From these samples, thirty-eight individual isolates were

identified by biochemical testing; one sample could not be identified. Nine distinct organisms were

identified to the species level and included both gram positive and gram negative bacteria. Each of

the 39 isolates was tested for resistance to 17 antibiotics. Resistance to three b-lactams (ampicillin,

oxacillin [methicillin], and penicillin) was most common while overall drug resistance remained

low. b-lactam antibiotics are commonly used to treat a wide range of bacterial infections. Oxacillin

is one of the ‘‘last ditch’’ antibiotics within the b-lactam family and is used for serious bacterial

infections. With the overuse and misuse of antibiotics, drug and multi-drug resistance amongcommonly encountered bacteria is expected to rise.

Introduction

Antibiotic resistance in bacteria repre-

sents a global healthcare problem that

has come to the forefront of the

public’s attention with problems such as

methicillin resistant Staphylococcus aureus

(MRSA), multi-drug resistant tuberculosis,

multi-drug resistant Pseudomonas aeruginosa,

and vancomycin resistant enterococci (VRE) on

the rise within hospital and community settings.

In 2011, the World Health Organization (WHO)

recognized this problem by making antibiotic

resistance their campaign topic for World Health

Day. The WHO encourages nations around the

world to improve drug resistance education, to

standardize and maintain proper surveillance of

antimicrobial trends, to establish limits to the

over prescription or free acquisition of antibiot-

ics, and to develop new treatment regimens and

antimicrobial drugs (WHO, 2011a). The WHO

also encourages the development of action plans

for each nation that targets these goals and

establishes deadlines for meeting each goal. The

Centers for Disease Control and Prevention

(CDC), the Food and Drug Administration, and

the National Institutes of Health (NIH) recently

released their Public Health Action Plan to

Combat Antimicrobial Resistance Part I: Do-

mestic Issues which establishes a plan of action

for the United States to monitor antimicrobial

resistance, to develop and implement prevention

and control strategies, to conduct research onCorrespondence to: lblankinship@una.edu

165BIOS 84(3) 165–172, 2013

Copyright Beta Beta Beta Biological Society

the mechanisms of antimicrobial resistance

transfer and novel detection methods, and to

develop new drugs to treat current and future

microbial infections (CDC et al., 2011).

The problem of antibiotic resistance is both

humanitarian and economic and is no longer

limited to just bacteria. Increasing incidence of

antimicrobial drug resistance in viruses, proto-

zoa, and fungi are being reported (CDC et al.,

2011). The American Society for Microbiology

(2011) has estimated that 63,000 people die

annually in the United States from hospital

acquired antimicrobial resistant infections

which increase the cost of healthcare by

approximately $20 billion per year. The WHO

estimates that 25,000 people die annually in the

European Union due to antimicrobial resistant

infections from healthcare sources (WHO,

2011b). These data do not include the cost or

incidence of community acquire infections such

as MRSAwhich have been on the rise since the

1980s (CDC et al., 2011).

One method for decreasing the threat of

antibiotic resistance is through education of

proper sanitary practices including the disinfec-

tion of publically available materials and

common-use items and proper hand washing.

Other mechanisms for decreasing antibiotic

resistance include education of the general

population that antibiotics will not treat viral,

fungal, or protozoan infections; limiting general

population access to over-the-counter antibiot-

ics; and holding physicians accountable to only

prescribe antibiotics when they are absolutely

necessary. Antibiotics used with agriculture

should be highly regulated and limited so that

the antibiotics that are used with humans are not

used in food animals or plants. Drug develop-

ment companies also play a major role in the

problem of antibiotic resistance both through

their marketing strategies and in the develop-

ment of future antibiotics (CDC et al., 2011;

WHO, 2011c). The WHO notes that few

antibiotics are under development that show

promise against multi-drug resistant bacteria,

especially with the newly emergent and highly

transmissible New Delhi metallo-b-lactamase-1

(NMD-1) gene producing resistance to carba-

penems, a subclass of cephalosporins (Bryskier,

2005; Salyers and Whitt, 2005; WHO, 2011d).

With the growing incidence of community-

acquired infections and the emergence of

antibiotic resistant ‘‘superbugs’’ both withinand outside of the healthcare system, there isan urgent need to sample both communaland individual items used on a daily basis forantibiotic resistant microbes. Common-useitems such as cell phones and computerkeyboards act as ideal mechanisms fortransferring microbes from one user toanother and may influence drug resistanceamong normal bacterial microbiota. Severalresearch articles have focused on the spreadof MRSA within the community and health-care settings. One survey of public accesstelephone receivers in Lagos found that 44%of all Staphylococcus isolates showed multi-

drug resistance (Smith et al., 2009). Another

study conducted in Amravati, India showed that

67% of community acquired MRSA isolates

and 56% of hospital acquired MRSA isolates

showed resistance to vancomycin, one of the

‘‘last ditch’’ antibiotics (Dong et al., 2004;Tambekar et al., 2007). A study of universitypersonnel, hospital staff, community mem-bers, and hospitalized patients showed thatcell phones contained several pathogenic orpotentially problematic gram negative bac-terial species including Escherichia coli, P.

aeruginosa, Klebsiella species, Serratia species,

and Proteus vulgaris in addition to gram

positive S. aureus (Famurewa and David,

2009). Pens, stethoscopes, cell phones, and lab

coats have also been identified as vectors for

hospital acquired infections (Pandey et al.,

2010). One study of cell phones used by dental

clinic students and faculty showed that by

disinfecting cell phones with 70% isopropyl

alcohol (over-the-counter isopropanol) the av-

erage bacterial load of each cell phone was

reduce by about 87% (Singh et al., 2010).

A current review of the literature shows that

only a limited number of studies on the

prevalence of antibiotic resistance within com-

munity settings have been conducted over the

past two decades within the United States.

Surveillance studies of antibiotic resistance tend

166 BIOS

Volume 84, Number 3, 2013

to focus on either one particular pathogen such

as MRSA or are limited to healthcare settings.

During this project, samples were collected

from common-use computer keyboards in a

student computer lab and from the library at

Troy University in Troy, Alabama. Samples

were also collected from the cell phones of Troy

University students, faculty, and staff. The

purposes of the project were to: 1) identify

bacteria isolated from computer keyboards and

cell phones and 2) generate antibiotic resistance

profiles for each isolate.

Materials and Methods

Sample collection and isolation

Twenty common-use computer keyboards

from the math lab and university library were

sampled with a sterile swab moistened in sterile

distilled (DI) water by rubbing the swab over

the computer keys and spacebar. Twenty

student, faculty, and staff (10 student, 10 faculty

or staff) cell phones were similarly sampled

along the cell phone key pad and face plate.

Swabs were incubated in 2.0 mL of sterile

nutrient broth (8.0 g nutrient broth [Difco]/L)

overnight at 358C. One mL of each culture was

serially diluted in sterile DI water and spread

plated onto nutrient agar plates (8.0 g nutrient

broth [Difco], 14.0 g agar [BD]/L) and

incubated overnight at 358C. All samples were

plated in triplicate per dilution.

Sample identification

Three to five isolates were chosen for each

cell phone and computer keyboard sample from

the serial dilution plates. Isolates were streaked

for purity and identified using a dichotomous

key based on biochemical tests such as gram

stain, phenol red fermentation broths, mannitol

salt, methyl red and Vogues Proskauer, citrate

fermentation, indole, catalase and oxidase tests

(Johnson and Case, 2001).

Antibiotic resistance testing

The Kirby Bauer test for antibiotic resistance

was used to determine the antibiotic resistance

profile of each isolate (Johnson and Case,

2001). In brief, each isolate was grown

overnight in 2.0 mL nutrient broth at 358C.

Log growth phase cells of each sample were

swabbed onto Mueller Hinton agar plates (65.0

g Mueller Hinton agar / L [BD]). Four to five

paper disks impregnated with the antibiotics to

be tested were placed on each inoculated plate.

Cultures were incubated overnight at 358C and

read 24-48 h after inoculation. Zone of

inhibition measurements were compared with

standard values available in the antibiotic disk

product insert [BD BBL Sensi-Disc]. All

cultures were tested in triplicate and a blank

paper disk was included as a negative control.

Antibiotics tested included: ampicillin (10 lg[BD]), bacitracin (10 U [BD]), chloramphenicol

(30 lg [BD]), cefopherazone (75 lg [BD]),

cefazolin (30 lg [BD]), erythromycin (15 lg[BD]), gentamicin (10 lg [BD]), kanamycin (30

lg [BD]), levofloxacin (5 lg [BD]), neomycin

(30 lg [BD]), novobiocin (30 lg [BD]),

oxacillin (1 lg [BD]), penicillin (10 U [BD]),

piperacillin (100 lg [BD]), streptomycin (10 lg[BD]), tetracycline (30 lg [BD]), and vanco-

mycin (30 lg [BD]).

Results

Nine organisms were identified from com-

puter keyboard and cell phone samples (Table

1). Of the 38 bacterial samples identified,

Variovorax paradoxus (one isolate), Enterococ-

cus faecalis (three isolates) and Staphylococcus

aureus (eight isolates) were isolated only from

cell phones while Bacillus cereus (three iso-

lates) and Micrococcus luteus (five isolates)

were isolated only from computer keyboards.

Bacillus megaterium (one isolate from a cell

phone and two isolates from computer key-

boards), Corynebacterium pseudodiptheriticum

(three isolates from cell phones and five isolates

from computer keyboards), Proteus mirabilis

(three isolates from cell phones and two isolates

from computer keyboards), and Staphylococcus

saprophyticus (one isolate each from a cell

phone and a computer keyboard) were isolated

from both sources. One bacterial sample could

not be identified using the dichotomous key.

Cell phone isolated antibiotic resistant bacteria 167

Volume 84, Number 3, 2013

Antibiotic resistance was found to be low

among the various isolates (Tables 2 and 3). V.

paradoxus and E. faecalis isolates from cell

phones showed resistance (100% of tested

isolates) to oxacillin, a replacement antibiotic

for methicillin. B. cereus isolates from computer

keyboards showed resistance to ampicillin

(66.6%), oxacillin (66.6%), and penicillin

(100%). M. luteus isolates from computer

keyboards were resistant to erythromycin

(60%) and oxacillin (80%). S. aureus isolates

from cell phone samples showed resistance to

ampicillin (12.5%), novobiocin (62.5%), oxa-

cillin (25%), penicillin (12.5%), and tetracy-

cline (12.5%). B. megaterium isolates from cell

phones showed no resistance to the seventeen

compounds that were tested while computer

keyboard isolates showed some resistance

(50%) to cefopherazone, cefazolin, oxacillin,

and penicillin. C. pseudodiptheriticum isolates

from cell phones showed resistance to ampicil-

lin (100%), oxacillin (100%), penicillin

(66.6%), and piperacillin (33.3%) while com-

puter keyboard isolates were found to be

resistant to ampicillin (80%), bacitracin

(20%), oxacillin (80%), and penicillin (60%).

Computer keyboard isolates of P. mirabilis

showed resistance to oxacillin (50% of tested

isolates) while samples isolated from cell

phones showed resistance to cefazolin

(66.6%), novobiocin (66.6%), oxacillin

(100%), penicillin (66.6%), and vancomycin

(66.6%). S. saprophyticus isolated from a cell

phone showed resistance to oxacillin and

penicillin while the computer keyboard isolate

was resistant to oxacillin. The unidentified

organism isolated from a computer keyboard

showed resistance to oxacillin and streptomy-

cin. All organisms showed good growth in the

Table 1. Summary of bacteria isolated from computerkeyboards and cell phones, their source of isolation, andnumber of isolates obtained from each source.

Isolate Source (Number of isolates)

Bacillus cereus Keyboard (3)

Bacillus megaterium Cell (1), Keyboard (2)

Corynebacterium

pseudodiptheriticum

Cell (3), Keyboard (5)

Enterococcus faecalis Cell (3)

Micrococcus luteus Keyboard (5)

Proteus mirabilis Cell (3), Keyboard (2)

Staphylococcus aureus Cell (8)

Staphylococcus saprophyticus Cell (1), Keyboard (1)

Variovorax paradoxus Cell (1)

Unknown (no ID) Keyboard (1)

Table 2. Antibiotic resistance among cell phone isolated bacteria. Percentages reflect the percent of total isolates from cellphones that showed resistance to each test antibiotic. Abx = antibiotic, BM = Bacillus megaterium, CP = Corynebacteriumpseudodiphtheriticum, EF = Enterococcus faecalis, PM = Proteus mirabilis, SA = Staphylococcus aureus, SS =Staphylococcus saprophyticus, VP = Variovorax paradoxus, and syn = synthesis.

Antibiotic Abx Target BM CP EF PM SA SS VP

Ampicillin Cell wall 0% 100% 0% 0% 12.5% 0% 0%

Bacitracin Cell wall 0% 0% 0% 0% 0% 0% 0%

Chloramphenicol Protein syn 0% 0% 0% 0% 0% 0% 0%

Cefopherazone Cell wall 0% 0% 0% 0% 0% 0% 0%

Cefazolin Cell wall 0% 0% 0% 66.6% 0% 0% 0%

Erythromycin Protein syn 0% 0% 0% 0% 0% 0% 0%

Gentamicin Protein syn 0% 0% 0% 0% 0% 0% 0%

Kanamycin Protein syn 0% 0% 0% 0% 0% 0% 0%

Levofloxacin DNA syn 0% 0% 0% 0% 0% 0% 0%

Neomycin Protein syn 0% 0% 0% 0% 0% 0% 0%

Novobiocin DNA syn 0% 0% 0% 66.6% 62.5% 0% 0%

Oxacillin Cell wall 0% 100% 100% 100% 25% 100% 100%

Penicillin Cell wall 0% 66.6% 0% 66.6% 12.5% 100% 0%

Piperacillin Cell wall 0% 33.3% 0% 0% 0% 0% 0%

Streptomycin Protein syn 0% 0% 0% 0% 0% 0% 0%

Tetracycline Protein syn 0% 0% 0% 0% 12.5% 0% 0%

Vancomycin Cell wall 0% 0% 0% 66.6% 0% 0% 0%

Blank none 100% 100% 100% 100% 100% 100% 100%

168 BIOS

Volume 84, Number 3, 2013

presence of a blank paper disk which served as

the negative control.

Discussion

Bacteria cultured from cell phones and

computer keyboards represent a mixed popula-

tion with several organisms commonly found as

normal human microbiota. Staphylococcus and

Micrococcus species are commonly found on

human skin and represent little threat to a

healthy individual (Willey et al., 2011). How-

ever, S. aureus has recently caused numerous

methicillin resistant outbreaks with some strains

showing multi-drug resistance which have led

to investigations into community acquired

infectious disease and the transfer of pathogens

through common-use items or commonly-

touched surfaces (Famurewa and David, 2009;

Pandey et al., 2010; Singh et al., 2010; Smith et

al., 2009; Tambekar et al., 2007). Eight isolates

of S. aureus and one isolate of S. saprophyticus

were identified from cell phone samples while

computer keyboards yielded five isolates of M.

luteus and one isolate of S. saprophyticus. S.

aureus and M. luteus were expected to be

present in the sampling as they are common

bacteria isolated from human skin and could

easily be transferred from skin to commonly

touched objects. S. saprophyticus has been

associated with urinary tract infections since

the 1960s but little remains known about this

organism or its natural habitat (Raz et al., 2005).

Contamination of a cell phone or keyboard with

S. saprophyticus was most likely due to

improper hand washing technique.

E. faecalis and P. mirabilis are part of the

normal human intestinal microbiota while C.

pseudodiptheriticum is commonly found in the

nose, nasopharynx, and external ear of humans

(Janda and Abbott, 2006; Willey et al., 2011). P.

mirabilis is an opportunistic pathogen that

typically causes nosocomial urinary tract infec-

tions (Janda and Abbott, 2006). E. faecalis and

C. pseudodiptheriticum are not pathogenic in

healthy individuals (Willey et al., 2011). Three

isolates of E. faecalis were isolated from cell

phone samples. Three isolates of P. mirabilis

were isolated from cell phone samples while

two isolates came from computer keyboards. C.

pseudodiptheriticum was isolated from both cell

phone (three isolates) and computer keyboards

(five isolates). Again, contamination of cell

phones and computer keyboards with E.

Table 3. Antibiotic resistance among public access computer keyboard isolated bacteria. Percentages reflect the percent oftotal isolates from computer keyboards that showed resistance to each test antibiotic. Abx = antibiotic, BC = Bacillus cereus,BM = Bacillus megaterium, CP = Corynebacterium pseudodiptheriticum, ML = Micrococcus luteus, PM = Proteusmirabilis, SS = Staphylococcus saprophyticus, Unk = unknown (no identification), and syn = synthesis.

Antibiotic Abx Target BC BM CP ML PM SS Unk

Ampicillin Cell wall 66.6% 0% 80% 0% 0% 0% 0%

Bacitracin Cell wall 0% 0% 20% 0% 0% 0% 0%

Chloramphenicol Protein syn 0% 0% 0% 0% 0% 0% 0%

Cefopherazone Cell wall 0% 50% 0% 0% 0% 0% 0%

Cefazolin Cell wall 0% 50% 0% 0% 0% 0% 0%

Erythromycin Protein syn 0% 0% 0% 60% 0% 0% 0%

Gentamicin Protein syn 0% 0% 0% 0% 0% 0% 0%

Kanamycin Protein syn 0% 0% 0% 0% 0% 0% 0%

Levofloxacin DNA syn 0% 0% 0% 0% 0% 0% 0%

Neomycin Protein syn 0% 0% 0% 0% 0% 0% 0%

Novobiocin DNA syn 0% 0% 0% 0% 0% 0% 0%

Oxacillin Cell wall 66.6% 50% 80% 80% 50% 100% 100%

Penicillin Cell wall 100% 50% 60% 0% 0% 0% 0%

Piperacillin Cell wall 0% 0% 0% 0% 0% 0% 0%

Streptomycin Protein syn 0% 0% 0% 0% 0% 0% 100%

Tetracycline Protein syn 0% 0% 0% 0% 0% 0% 0%

Vancomycin Cell wall 0% 0% 0% 0% 0% 0% 0%

Blank none 100% 100% 100% 100% 100% 100% 100%

Cell phone isolated antibiotic resistant bacteria 169

Volume 84, Number 3, 2013

faecalis, P. mirabilis, and C. pseudodiptheriti-

cum would suggest that these organisms were

transferred to surfaces by persons who had

improperly washed their hands or touched their

nose without sanitizing their hands.

Bacillus species and V. paradoxus are

common inhabitants of the soil though Bacillus

species may live in a wide range of habitats. V.

paradoxus, recently removed from the genus

Alcaligenes, and B. megaterium are nonpatho-

genic while B. cereus may cause food poisoning

(Holt et al., 1994; Willey et al., 2011). Three

isolates of B. cereus were obtained from

computer keyboard samples while B. megate-

rium was present on both cell phones (one

isolate) and computer keyboards (two isolates).

V. paradoxus was isolated once from a cell

phone. The data again suggest transfer of soil

microbes from individuals who had not washed

their hands after coming in contact with soil or

had practiced improper hand washing tech-

nique.

Seventeen antibiotics were tested for their

effectiveness against the cell phone and com-

puter keyboard isolates. A blank paper disk of

the same size and manufacture as antibiotic

impregnated disks was included as a negative

control. All samples were unaffected by the

negative control and thus produced no zones of

inhibition around the paper disk. Zone of

inhibition size for the seventeen antibiotics

varied with organism and isolate.

Penicillins (ampicillin, oxacillin, penicillin,

and piperacillin), cephalosporins (cefophera-

zone and cefazolin), and the peptide antibiotic

vancomycin block cell wall development in

bacteria by preventing peptidoglycan formation

or crosslinking (Bryskier, 2005; Salyers and

Whitt, 2005). These compounds are most

effective against gram positive bacteria such as

Staphylococcus, Micrococcus, Enterococcus,

Corynebacterium, or Bacillus species. B. cereus

isolates (66.6%) collected from computer

keyboards showed resistance to ampicillin and

oxacillin while all B. cereus isolates were

resistant to penicillin. Half of the B. megaterium

isolates from computer keyboard samples were

found to be resistant to cefopherazone, cefazo-

lin, oxacillin, and penicillin. B. megaterium

isolates from cell phones were not found to be

resistant to penicillins, cephalosporins, or van-

comycin. C. pseudodiptheriticum isolates were

found to be resistant to ampicillin (100% cell

phone isolates, 80% computer keyboard iso-

lates), oxacillin (100% cell phone isolates, 80%computer keyboard isolates), penicillin (66.6%cell phone isolates, 60% computer keyboard

isolates), and piperacillin (33.3% cell phone

isolates, 0% computer keyboard isolates). E.

faecalis isolates collected from cell phones only

showed resistance to oxacillin. Eighty percent

of M. luteus isolates collected from computer

keyboards showed resistance to oxacillin. S.

aureus isolated from cell phones showed

resistance to ampicillin (12.5%), oxacillin

(25%), and penicillin (12.5%) while both S.

saprophyticus isolates (one from a cell phone

and one from a computer keyboard) showed

resistance to oxacillin and penicillin (cell phone

isolate only). None of the gram positive isolates

showed resistance to vancomycin and only C.

pseudodiptheriticum showed resistance to pi-

peracillin. Oxacillin has replaced methicillin in

clinical treatment while vancomycin represents

one of the ‘‘last ditch’’ antibiotics andcontinues to play an important role in thetreatment of oxacillin resistant S. aureus

(Bryskier, 2005; Dong et al., 2004). It is

concerning that the majority of gram positive

isolates showed resistance to oxacillin as this

antibiotic was once used as a ‘‘last ditch’’ drugbefore resistance became so prevalent.

Variovorax and Proteus species are gram

negative rods so it was expected that these

isolates would show high resistance to b-lactams (penicillins and cephalosporins) and

vancomycin. Because gram negative bacteria

contain an outer membrane and have only a few

layers of peptidoglycan, antibiotics that target

the cell wall construction (e.g., peptidoglycan

synthesis or crosslinking) are inefficient treat-

ment options. However, the V. paradoxus isolate

was only found to show resistance to oxacillin.

P. mirabilis isolates showed more diversity in

their antibiotic resistance profile than the V.

paradoxus isolate. P. mirabilis showed resis-

tance to cefazolin (66.6% in cell phone isolates,

0% in computer keyboard isolates), oxacillin

170 BIOS

Volume 84, Number 3, 2013

(100% in cell phone isolates, 50% in computer

keyboard isolates), penicillin (66.6% in cell

phone isolates, 0% in computer keyboard

isolates), and vancomycin (66.6% in cell phone

isolates, 0% in computer keyboard isolates).

Neither V. paradoxus nor P. mirabilis showed

resistance to ampicillin, cefopherazone, or

piperacillin.

Bacitracin is a peptide antibiotic that inter-

feres with cell wall synthesis. As a result,

bacitracin is most effective against gram

positive bacteria and has been shown to be

effective against some archaeobacteria (Brysk-

ier, 2005; Salyers and Whitt, 2005). Only 20%of C. pseudodiptheriticum isolates obtained

from computer keyboards showed resistance to

bacitracin; all other isolates of C. pseudodip-

theriticum, Bacillus species, E. faecalis, M.

luteus, and Staphylococcus species did not show

resistance to bacitracin. All gram negative

isolates (P. mirabilis and V. paradoxus) were

susceptible to bacitracin which is surprising as

bacitracin blocks peptidoglycan synthesis and

normally would not be effective against gram

negative bacteria. Bacitracin is one of the most

commonly used over-the-counter antibiotics as

it is found in most antibiotic first aide ointments

(Salyers and Whitt, 2005). Normal microbiota

of the human skin tend to be dominated by gram

positive species, particularly Micrococcus and

Staphylococcus species (Willey et al., 2011).

Several classes of antibiotics inhibit bacterial

protein synthesis by binding to or preventing

movement of the bacterial ribosomes. Because

bacteria utilize ribosomes that are different from

eukaryotic ribosomes, the bacterial ribosome is

a popular antibiotic target. Drugs that interfere

with protein synthesis are effective against both

gram positive and gram negative bacteria

(Willey et al., 2011). Phenicols (chloramphen-

icol), macrolides (erythromycin), aminoglyco-

sides (gentamicin, kanamycin, neomycin, and

streptomycin), and tetracycline are all examples

of antibiotics that inhibit protein synthesis

(Bryskier, 2005; Salyers and Whitt, 2005). All

isolates of Bacillus species, C. pseudodipther-

iticum, E. faecalis, P. mirabilis, Staphylococcus

species, and V. paradoxus were found to be

susceptible to chloramphenicol, gentamicin,

kanamycin, neomycin, and streptomycin. Only

12.5% of S. aureus isolates showed resistance

to tetracycline while 60% of M. luteus isolates

showed resistance to erythromycin. Like baci-

tracin, neomycin is a common ingredient in

over-the-counter antibiotic ointments such as

Neosporint (Salyers and Whitt, 2005).

Fluoroquinoles (levofloxacin) and coumarin

(novobiocin) antibiotics target DNA gyrase and

prevent or limit the ability of a bacterium to

replicate DNA (Bryskier, 2005, Salyers and

Whitt, 2005). DNA replication is usually a

growth limiting step during bacterial cell

division (Willey et al., 2011). Because all

bacteria use DNA gyrase during replication,

antibiotics that target this process would be

effective against both gram positive and gram

negative organisms. All isolates of Bacillus

species, C. pseudodiptheriticum, E. faecalis, M.

luteus, P. mirabilis, Staphylococcus species, and

V. paradoxus were susceptible to levofloxacin.

Cell phone isolates of P. mirabilis (66.6%) and

S. aureus (62.5%) showed resistance to novo-

biocin. Levofloxacin is used to treat a wide

range of illnesses including bacterial infections

of the sinuses, urinary tract, kidneys, prostate,

skin, chronic bronchitis and pneumonia and

may be used prophylactically in individuals

who have been exposed to anthrax (NIH, 2009).

Resistance to novobiocin is not surprising as

this is an older antibiotic dating back to the

1950s (Bryskier, 2005).

This study investigated bacteria associated

with cell phones and public use computer

keyboards and the antibiotic resistance of

bacteria isolated from these commonly touched

surfaces. The experiment isolated aerobic and

facultative bacteria capable of growth in

nutrient broth. Strict anaerobes and fastidious

species, such as those requiring special cultur-

ing methods, are not expected to be long-term

residents of common-use items as these surfaces

are dry, continuously exposed to oxygen and

ambient environmental conditions (e.g., humid-

ity, temperature, etc.), and lack growth factors

needed by many fastidious species. The major-

ity of bacteria isolated from cell phones and

computer keyboards included normal microbi-

ota of the human body though the presence of

Cell phone isolated antibiotic resistant bacteria 171

Volume 84, Number 3, 2013

bacteria associated with soil and the human

intestinal tract and nasopharynx would suggest

improper hand washing technique or that hands

were not frequently washed. While antibiotic

resistance was found to be low among cell

phone and computer keyboard isolates, the data

do offer a snapshot of antibiotic resistance

within the Troy University community during

fall 2009. As antibiotics continue to be misused

and overprescribed, the occurrence of antibiotic

resistance is expected to increase. Commonly

touched surfaces such as cell phone or common-

use objects such as public access computer

keyboards will serve as prime candidates for the

transmission of antibiotic resistance from one

person to another as bacteria on these objects

move between users. Surveillance of antibiotic

resistant organisms on these commonly touched

surfaces will provide information that may be

used by healthcare officials to develop strategies

against the spread of antibiotic resistance and

complies with one goal of the United States’

plan to combat the domestic increase in

resistance to antimicrobial compounds (CDC

et al., 2011).

Acknowledgments: The authors thank Kathryn

Hobgood, Jeanette Chancellor, Kristin Embry,

and B. Skot Holcombe for their assistance with

data collection and antibiotic testing. This work

was funded in part by a Beta Beta Beta

undergraduate research grant.

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Received 4 June 2012; accepted 28 December 2012.

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