This document provides a review of antimicrobial resistance in fish aquaculture. It discusses the increasing use of antimicrobial agents in aquaculture and the development and spread of resistance. Key points include: 1) Antimicrobial agents are commonly used in aquaculture for disease treatment and growth promotion, but their overuse and misuse has led to the development of resistance. 2) Resistance genes can be transferred between bacteria through horizontal gene transfer, affecting the whole ecosystem. 3) Wastewater from aquaculture facilities contains high levels of antimicrobial residues and resistant bacteria, acting as reservoirs for resistance development. 4) There are risks to both animal and human health from antimicrobial resistant

1. REVIEW ON
ANTIMICROBIAL RESISTANCE IN FISH
Submitted by:
Biplov Shrestha
M.Sc. Fisheries (Aquaculture)
AQU-M-02-2021
Submitted to:
Prof. Dilip Kumar Jha, Ph.D.
Department of Aquatic Resource Management
Fisheries Program
FAVF, AFU, Rampur

2. TABLE OF CONTENTS
• Introduction
• Antimicrobial agents use in aquaculture
• Routes of antimicrobial agents administration
• Development and spread of antimicrobial resistance
• Wastewater habitats as reservoirs for the development of AMR
• Risk Associated with Antimicrobial Resistant in Fish culture
• Management and alternative strategies
• Conclusion
• References
2

3. INTRODUCTION
• Antibiotic: substance produced by one microorganism that selectively
inhibits the growth of another microorganism (Kümmerer, 2009;
Rodgers & Furones, 2009)
• Earlier antibiotic was derived from plant (penicillin). And in the
present, antibiotics are derived through a chemical processes, such as
the sulfa drugs (e.g. sulfamethoxazole)
3

4. CONTINUE
• Diverse group: ß-lactams, quinolones, tetracyclines, macrolides, sulphonamides,
and others (Kümmerer, 2009)
• Aquaculture sector is increasing rapidly to fulfill increasing demand
accompanied by intensive use of antibiotics
• Increasing antibiotic use: production of antimicrobial resistant pathogens and
gene
• Antibiotics in aquaculture: oxytetracycline, florfenicol, sulphadiazine,
amoxicillin, sulphadimethoxine, and enrofloxacin 4

5. • Development of resistant gene leads to loss of effectiveness of
antimicrobial agents
• Causing high mortality and high expanses on treatment
• Antimicrobial resistance gene can transfer horizontally, affecting whole
ecosystem
• Fish pathogens have several antibiotic resistance and that's why detailed
knowledge of the gene transfer system required to explore the
complexity of antimicrobial resistance in aquaculture (Preeena,
Swaminathan, Kumar, & Singh, 2020). 5

6. • High use of antibiotic agents in animal raises risk to human health (Heuer et.al ,
2009)
• Several pathogens in fish and shellfish studied: Aeromonas salmonicida,
A. hydrophila, A. caviae, A. sobria, E. ictaluri, E. tarda, P. damselae piscicida,
Vibrio anguillarum, V. salmonicida, V. ordalii, Flavobacterium psychrophilum,
Pseudomonas fluorescens, Streptococcus iniae, Renibacterium salmonicarum,
Yersinia ruckeri, and Piscirickettsia salmoni (Cabello, et al., 2013)
• AMR transferred: plasmid, mobile genetic elements (MGE), and horizontal gene
transfer (HGT) 6

7. ANTIMICROBIALAGENTS USE IN AQUACULTURE
• Intensification of aquaculture: fish disease and water quality problems
• Chemicals: antibiotics, hormones, pesticides, anesthetics, and various
pigments, minerals, and vitamins (Rodgers & Furones, 2009)
• 73% of countries: oxytetracycline, florfenicol, and sulphadiazine,
• 55%: amoxicillin, sulphadimethoxine, and enrofloxacin (Preeena,
Swaminathan, Kumar, & Singh, 2020)
7

8. • Antimicrobial agents: administrated in feed or adding it directly into the
water
• Results in strong selective pressure (Heuer, Collignon, Karunasagar, &
Angulo , 2009; Carvalho, David, & Silva, 2013)
• Aquaculture: prophylactic purposes and metaphylactic treatment
• No specific antibiotic for aquaculture so, certified products of veterinary
medicine are used (Santos & Ramos, 2018)
• Use of antimicrobial agents is governed by rules and regulations
8

9. • Despite rules and regulation China are using banned antimicrobial agents
for production and India account 8% of unregulated production and usages
• USA: 5 drugs have been approved by the US Food and Drug
Administration (FDA), oxytetracycline, florfenicol, Sulfa/trimethoprim and
sulfadimethoxine/ormetoprim (Schnick, 2000)
• Europe: oxytetracycline, florfenicol, sarafloxacin, erythromycin, and
sulphonamides (Santos et al., 2018).
• Other factors: pathogens present, the treatment timing, condition of
diseased fish, and culture parameters (physical and chemical)
9

10. Table 1: Reported Quantity of Antimicrobial Agents Intented For Animal Use By OIE Region,
2014
OIE Region No of countries
reporting quantitative
data for 2014
% of total
estimated biomass
Quantities (tonnes)
Africa 13 41% 3,869
Americas 11 86% 26,271
Asia and the
Pacific
5 6% 3,396
Europe 31 71% 8,891
Total 60 47% 42,427
10

11. Fig 1: consumption trend of antimicrobial agent in nepal (Acharya & Wilson, 2019)
11
16306.3
20569.3
22829.5
26320
29474.2
31595.7
0
5000
10000
15000
20000
25000
30000
35000
2002 2008 2009 2010 2011 2012
Amount
in
kg
Year
Consumption trend of antimicrobial in food producing animals

12. ROUTES OF ANTIMICROBIALAGENTS ADMINISTRATION
• Injection: Effective and direct approach, antibiotics directly get into
bloodstream. Suitable for small no of fish
• Mix with foods: Orally with food, early detection of diseased fish to treat
(Watts et al., 2017)
• Bath treatment: Large quantity of drugs, no guarantee of effectiveness, use
when large number is suffered (Yanong, 2016)
12

13. DEVELOPMENT AND SPREAD OF ANTIMICROBIAL
RESISTANCE
• Development and spread of AMR has become serious threat
• Development: Unregulated use of antimicrobial agents (30% in sediment),
• Through various processes such as mutation, horizontal gene transfer (HGT),
natural transformation, transduction, and conjugation (Iwasaki & Takagi,
2009; Aminov, 2011; Marti, Variatza, & Balcazar, 2014)
• Use of antimicrobial agents in one ecological niche, impact the occurrence
of antimicrobial resistance in other ecological niches, including the human
environment (FAO, WHO, OIE, 2003) 13

14. • Aquaculture system: a hotspot for AMR genes, where significant genetic
exchange and recombination takes place (Baquero, Martinez, & Canton,
2008)
• Resistance determinants are originated from aquatic bacteria, such as
plasmid-mediated quinolone resistance determinants from the qnr family and
CTX-M from aquatic Kluyvera spp (Cantas, et al., 2013)
• AMR gene bacteria live up to several years
14

15. • Antimicrobial agents in aquaculture are identified as critically important
for human medicine by World Health Organization
• Occurrence of resistance to these antimicrobials in human pathogens
possess a serious threat
• Table 2: Antimicrobial Agents (and Classes) Used in Aquaculture and
Their Importance in Human Medicine (Heuer, Collignon, Karunasagar,
& Angulo , 2009)
15

16. Antimicrobial agents (Drug class) Route of administration Importance of antimicrobial class
in human medicine
Amoxicillin (aminopenicillins) Oral Critically important
Ampicillin (aminopenicillins) Oral Critically important
Chloramphenicol (amphenicols) Oral/bath/injection Important
Florfenicol (amphenicols)a Oral Important
Erythromycin (macrolides) Oral/injection/bath Critically important
Streptomycin, neomycin
(aminoglycosides)
Bath Critically important
Furazolidone (nitrofurans) Oral/bath Important
Nitrofurantoin (nitrofurans) Oral Important
Oxolinic acid (quinolones)a Oral Critically important
Sulphonamides (sulphonamides) Oral Highly important
Flumequine (fluoroquinolone)a Oral Critically important
Oxytetracycline, chlotetracycline,
tetracycline (tetracyclines)
Oral/bath/injection Highly important
Enrofloxacin (fluoroquinolone)a Oral Important 16

17. • Antibiotics: growth promoter and to treat against bacterial infection for a
longer period of time leads to an increase in selective pressure,
• alters the biodiversity of aquatic environment by replacing the susceptible
bacterial population with resistant ones (Gullberg, et al., 2011)
• and persist in the environment even in the absence of a responsible gene
• AMR genes, tetracycline persist in aquaculture farms even in the absence of
selection pressure, indicating the transfer of AMR genetically from other
niches (Preeena et al., 2020)
17

18. • Mobile genetic elements (plasmids and transposable elements): bacterial can
access a large pool of itinerant genes which moves from one bacterial cell to
another causing widespread of it (Carvalho et al., 2013)
18

19. WASTEWATER HABITATS AS RESERVOIRS FOR THE
DEVELOPMENT OF AMR
• Heavy nutrient load higher the frequency of resistance (Preeena et al., 2020)
• Wastewater: large number of AMR bacteria and gene, mixing such water in
environment leads to AMR development (Cantas, et al., 2013)
• AMR gene transfer: horizontal gene transfer via plasmid and facilitated by
integrons (Tennstedt, Szczepanowski, Braun, Puhler, & Schluter, 2003)
• Industrial effluent: high concentration of antibiotics and low in ground water
19

20. 20
Fig 2: The process of antibiotic and ARGs transportation through different media
and their possible exposure ways to human health

21. • Integrated aquaculture: potential source for development of AMR bacteria
• Manure: AMR bacteria in it may act as donors of AMR genes
• Accumulation of surplus antimicrobials and their residue could lead to
selective pressure and growth of AMR bacteria (Petersen et al., 2002)
• Water exchange: rarely, AMR bacteria and antimicrobial present in sediment
and water via accumulation get enough time to develop resistance by
promoting HGT (Cao, et al., 2015)
21

22. RISK ASSOCIATED WITH ANTIMICROBIAL RESISTANT IN
FISH CULTURE
• Fish: reservoir for pathogens, affects animal health along with humans
(Cantas, et al., 2013)
• Aquaculture facilities: Some common infections are Aeromonas
hydrophilia, Mycobacterium marinum, Streptococcus iniae, Vibrio
vulnificus, and Photobacterium damselae.
• Commercial sea products: bacterial strains carrying resistant determinants,
which contains disease-causing pathogens in humans (Watts et al., 2017)
22

23. • Cold water fish has higher potential to transmit the pathogens in human
(Alderman & Hastings, 1998)
• Plasmid-borne resistance genes have been disseminated to human
pathogens through conjugation, A.salmonicida to Escherichia coli
(Carvalho et al., 2013)
• AMR pathogen of fish causes AMR zoonotic infections in humans:
Aeromonas hydrophila, Mycobacterium marinum, Vibrio damselae,
Salmonella (Cabello, et al., 2013)
23

24. TABLE 2. SOME FISH ASSOCIATED ZOONOTIC INFECTIONS
Infectionious organism Disease
Mycobacterium marinum, M. fortuitum, M.
ulcerans
Fish handler disease, tank granuloma
Streptococcus iniae Cellulitis, systemic infections
Aeromonas hydrophila, A. sobria, A. caviae Skin wound infections, systemic infections
Vibrio damselae, V. vulnificus, V. mimicus, V.
fluvialis, V. alginolyticus
Skin and wound infections, systemic infections
Kluyvera Gastroenteritis, bacteraemia
Food-borne
Vibrio parahaemolyticus, V. cholerae Diarrhoea
Aeromonas hydrophila Diarrhoea, systemic infections
Salmonella Diarrhoea, systemic infections
Clostridium botulinicum, C. perfringens Botulism, diarrhoea
24

25. MANAGEMENT AND ALTERNATIVE STRATEGIES
• Developing alternatives treatment methods
• Formulated and implementing good measurement methods to stop the
spread of AMR in fish (WHO, 2006)
• Effective policies: proper regulations and enforcement, information
collection, risk assessment, disease control and management, capacity
building and effective biosecurity practices (Preeena et al., 2020; Heuer et
al., 2009)
25

26. • Detection and removal of antimicrobial residue from waste water via
coagulation, filtration sedimentation and biological process (Preeena et al.,
2020)
• Use of vaccination
• In Norway: heavy use of antimicrobial agents in salmon culture reduced
after the introduction of the oil-adjuvanted vaccine by 99% from 1997-2007
despite increasing production of fish (Markestad & Grave, 1997)
• Probiotics as growth promoters, biological control technique (Cantas, et al.,
2013) 26

27. • Lactobacillus, Carnobacterium, Enterococcus, Lactobacillus,
Streptococcus, etc
• Essential oils: plant origin and safe to use, antimicrobial properties and use
as preservatives in sea food
• Phage therapy: Therapeutic properties, prevent and control bacterial
infections
27

28. CONCLUSION
• Aquaculture sector growing rapidly along with antimicrobial agent usage
• Antimicrobial in aquaculture is generally used as a growth promoter and to
treat bacterial infection
• Unregulated and prolong use of antibiotics leads to selective, which results in
AMR development
• The development of antibiotic resistance in natural microbial communities
can affect a wide spectrum and indirectly or directly on human health
28

29. • Good management practices and development of alternative measures to
restrict the use of antibiotics
• Further detailed studies regarding the amount of antimicrobial use in
aquaculture in order to assess their potential impact on other environments
and on animal and human health
• Despite lacking of clear information it is clear that it can negatively affect
other environment and health
29

30. REFERENCES
• Cabello, F. C., Godfrey, H. P., Tomova, A., Ivanova, L., Dölz, H., Millanao, A., & Buschmann, A. H.
(2013). Antimicrobial use in aquaculture re‐examined: its relevance to antimicrobial resistance and to
animal and human health. Environmental Microbiology, 15(7), 1917-1942. Retrieved from
https://sfamjournals.onlinelibrary.wiley.com/doi/full/10.1111/1462-2920.12134
• Carvalho, E. D., David, G. S., & Silva, R. J. (2013). Health and Environment in Aquaculture. Rijeka:
InTech.
• FAO, WHO, OIE. (2003). Joint FAO/OIE/WHO expert workshop on non-human antimicrobial usage and
antimicrobial resistance: scientific assessment. Geneva. Retrieved from
https://apps.who.int/iris/bitstream/handle/10665/68883/WHO_CDS_CPE_ZFK_2004.7.pdf
• Heuer, O., Collignon, G. K., Karunasagar, I., & Angulo , F. (2009). Human Health Consequences of Use of
Antimicrobial. Clinical Infectious Diseases: an Official Publication of the Infectious Diseases Society of
America, 49(8), 1248-1253.
• Kümmerer, K. (2009). Antibiotics in the aquatic environment – A review – Part I. Chemosphere, 75(4),
417-434. Retrieved from https://sci-
hub.do/https://www.sciencedirect.com/science/article/abs/pii/S0045653508015105
30

31. • Preeena, P. G., Swaminathan, T. R., Kumar, V. J., & Singh, I. S. (2020). Antimicrobial resistance in
aquaculture: a crisis for concern. Biologia, 75, 1497–1517. doi:https://doi.org/10.2478/s11756-020-00456-
4
• Santos, L., & Ramos, F. (2018). Antimicrobial resistance in aquaculture: Current knowledge and.
International Journal of Antimicrobial Agents, 52, 135-143.
• Schnick, R. A. (2000). Sixth mid-year report of activities. National Coordinator for Aquaculture New
Animal Drug Applications (NADAs).
• atts, J. M., Schreier, H. J., Lanska, L., & Hale, M. S. (2017). The Rising Tide of Antimicrobial Resistance
in Aquaculture: Sources, Sinks and Solutions. (A. Place, R. Jagus, & P. Long, Eds.) Marine drugs, 15(6).
Retrieved from https://www.mdpi.com/1660-3397/15/6/158#cite
• WHO. (2006). Report of a Joint FAO/OIE/WHO Expert Consultation on antimicrobial use in aquaculture
and antimicrobial resistance. Seoul.
• Yanong, R. P. (2016, December). Use of Antibiotics in Ornamental Fish Aquaculture. UF/IAS Extension, 1-
7
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32. THANK YOU
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