Bacterial Contamination of Iranian Paper Currency and Their Antibiotic Resistance Patterns

1Department of Microbiology and Immunology, School of Medicine, Kashan University of Medical Sciences, Kashan, Iran 2Department of Microbiology and Immunology, School of Medicine, Alborz University of Medical Sciences, Karaj, Iran 3School of Medicine, Kashan University of Medical Sciences, Kashan, Iran 4Department of Parasitology and Mycology, School of Medicine, Alborz University of Medical Sciences, Karaj, Iran Int J Enteric Pathog. 2017 November;5(4):106-110

contaminated microorganisms isolated from Polish paper currencies. 15ill now, there are few studies on bacterial contamination of paper currencies in circulation and their antibiotic resistance pattern.This study aimed to determine bacterial contamination of Iranian paper currency in circulation and their antibiotic resistance patterns in Kashan, Iran.

Study Design
In this study, 337 currency notes of different value were collected from markets, shops, restaurants, bus stations and banks in Kashan, Iran during April 2015 to March 2016.The study samples were collected based on the level of usage by simple random sampling method as follows: the 13, 14, 21, 39, 46, 69, 71 and 64 pieces of 500; 1000; 2000; 5000; 10 000; 20 000; 50 000 and 100 000 Rials paper notes, respectively.Banknotes with different values which are currently in circulation (500; 1000; 2000; 5000; 10 000; 20 000; 50 000 and 100 000 Rials) were included in the study and notes that were withdrawn from circulation (100 and 200 Rials) were excluded.

Isolation and Identification of Bacteria
The currency notes transferred to Microbiology Laboratory at the Kashan University School of Medicine in sterile condition.Each note was swabbed with sterilized cotton swab which was wetted with sterilized distilled water.These swabs were plated on blood agar medium (Merck, Germany) and MacConkey agar medium (Merck, Germany) for isolation of gram-positive and gramnegative bacteria.After incubation for 24 to 48 hours at 37˚C, each bacterial colony was re-cultured on different series of blood agar and MacConkey agar culture media to obtain pure cultures.Each colony in pure culture was stained with gram method and bacterial isolates in pure culture were tested and identification of bacterial genus and species was done using standard microbiological and biochemical methods.
Antimicrobial susceptibility patterns of bacterial isolates were determined using disk diffusion method according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. 16The tested antibiotics were as follow: ampicillin, ciprofloxacin, gentamicin, nalidixic acid, amoxicillin, aztreonam, cefoxitin, vancomycin, tetracycline and erythromycin (Mast Company, UK).The standard strain of E. coli ATCC 25922 was used for quality control in susceptibility testing.Interpretation of results of antibiogram as susceptible, intermediate or resistant was done according to the criteria recommended by the CLSI guideline.

Statistical Analysis
For statistical analyses, SPSS version 16.0 (SPSS, Inc.) was used.Fisher exact and chi-square tests were used to study the statistical relationship between the results.P-value of less than 0.05 was considered statistically significant.

Results
Of total 337 currency notes, 262 (77.7%) were contaminated with bacteria (Table 1).Bacteria isolated from banknotes were included Bacillus spp, coagulasenegative staphylococci, E. coli, enterococci species, S. aureus, Klebsiella spp, Shigella species, and Pseudomonas species.Bacillus spp was the most common bacterial isolates from 113 currency notes of all denomination which were studied (Table 2).There were no significant correlations between bacterial growth, bacterial genera or species and denomination of currency notes (P > 0.05).Although the highest contamination was detected in 50 000 Rials paper notes and the 500 Rials paper notes had the lowest contamination (Table 1).There were relatively higher carriage rates of E. coli and enterococci species among banknotes isolated from shops and markets whereas the isolation of Staphylococcus species in paper notes collected from bus stations were higher.The highest resistance rates in gram-negative rods were against nalidixicacid and ampicillin.Also most resistance rates in S. aureus, coagulase-negative staphylococci and enterococci species were against ampicillin, and erythromycin (Table 3).

Discussion
Currency notes are frequently handled by various people with different hygienic level, are also stored in multiple environments, and therefore are considered as an important tool for transmission of pathogens within a population.
The results of our study showed that 77.7% of our studied currency notes were contaminated with bacteria.This finding is almost in agreement with the report of Saudi Arabia by Alwakeel and Nasser. 17However, higher levels of contamination were reported by Basavarajappa et al 4 in India and Pope et al 18 in the United States.Bacillus spp was the most common bacterial isolates in our contaminated currency notes.In accordance with our findings in other reports, the environmental bacteria and gram-positive normal flora especially Bacillus spp have been introduced as common contaminant of paper currency. 12Bacillus species have been found to cause significant infections in people with certain risk factors, while they scarcely cause infection in healthy people.The second most common bacterial isolate in current study was coagulase-negative staphylococci.In a survey, coagulase-negative staphylococci were reported as the most common contaminant of one-dollar bills which are widely used in the United States. 18The high frequency of contamination with coagulase-negative staphylococci among currency notes is logical because this bacterium is the main normal flora of human skin.However, coagulase-negative staphylococci are not considered as true pathogens, but immunocompromised patients are at risk of severe infection with them.The other isolates included in the current study were food-borne pathogens or causes of serious nosocomial infections.Studies on the persistence of pathogens on paper currency showed that currency notes are considered as a potential cause of food-borne diseases. 19There are evidences of isolation of food-borne pathogens including Salmonella spp, E. coli and S. aureus from the banknotes of different countries. 1he investigators have reported that many gram-positive and gram-negative bacteria such as enterococci spp, S. aureus, E. coli, Klebsiella spp, P. aeruginosa, and Serratia marcescens have the potential to survive on surfaces for several months. 20Among the bacterial isolates with more pathogenicity, we identified S. aureus which can cause wide range of infections in both hospitals    and community. 21The isolation of S. aureus as one of the bacterial isolates from paper currency in different countries has been reported. 12,14,18,21Considering the fact that S. aureus present in human nose and skin, isolation of this bacteria in paper currency is acceptable where the hygienic practices could be in low level.One result with particular importance in the present study was the isolation of Shigella species from the contaminated currency notes, showing fecal contamination.The results of a study on 1280 banknotes in 10 different countries showed that the currency papers with lower index value have higher microbial contamination. 1 In other studies also shown that currency notes with lower denomination carry more microbial agents due to more exchange among people with different occupations. 7,21In an investigation in Iran, the 50 000 Rials paper notes had the lowest bacterial contamination. 14In our study, unlike the other studies, the highest contamination was seen in 50 000 Rials paper notes whereas the 500 Rials paper notes had the lowest contamination.The difference between our results and other reports is due to that in our country currency notes with lower denomination like 500 Rials are not used regullary and the most exchanged paper notes are 50 000 Rials.Also small sample size could be the reason, as in our study only 13 pieces of 500 Rials paper notes were evaluated.
The person to person transmission of antimicrobial resistant bacteria via paper currency could be of great concern.Our antibiotic susceptibility test results revealed that there is resistance to clinically important antibiotics such as vancomycin in enterococci species, S. aureus and coagulase-negative staphylococci which could be a threat to cause vancomycin resistant enterococci (VRE) and vancomycin resistant S. aureus (VRSA) infections especially among immunocompromised persons.Although more accurate tests such as determination of MICs values are needed for identification of vancomycin resistant strains.In a survey in Saudi Arabia, it has been shown that all bacterial species were susceptible to gentamicin, ciprofloxacin and trimethoprimsulfamethoxazole, and in agreement with our results, resistance was seen against ampicillin in Enterobacter cloacae, Acinetobacter iwoffii and Staphylococcus warneri. 17inally, the present study revealed that the bacterial contamination among Iranian paper currency in circulation especially those obtained from certain sources including shops and bus stations is high and in most cases, these bacterial isolates are antibiotic resistant strains.Although here the clinical importance of bacterial contamination of currency notes is not investigated, transmissions of these bacteria especially antimicrobial resistant strains to immunosuppressed people may lead to serious infections, and they are notable.

Table 1 .
Bacterial Contamination of Paper Currencies With Different Denomination

Table 2 .
Bacterial Isolates From Paper Currencies With Different Denomination

Table 3 .
Antibiotic Resistance Patterns in Bacteria Isolated From Paper Currencies