Further Evidence of Anthropogenic Impact: High Levels of Multiple-Antimicrobial-Resistant Bacteria Found in Neritic-Stage Sea Turtles

BACKGROUND/OBJECTIVES

Marine turtles are globally threatened and face daily anthropogenic threats, including pollution. Water pollution from emerging contaminants such as antimicrobials is a major and current environmental concern.

METHODS

This study investigated the phenotypic antimicrobial resistance and heavy metal resistance genes of 47 Vibrio isolates from different stages of sea turtles (oceanic stage vs neritic stage) from the Taiwanese coast.

RESULTS

The results show that a high proportion (48.9%; 23/47) of the Vibrio species isolated from sea turtles in our study had a multiple antimicrobial resistance (MAR) pattern. It was found that Vibrio spp. isolates with a MAR pattern and those with a MAR index value greater than 0.2 were both more likely to be observed in neritic-stage sea turtles. Furthermore, isolates from neritic-stage sea turtles exhibited greater resistance to the majority of antimicrobials tested (with the exception of beta-lactams and macrolides) than isolates from the oceanic-stage groups. Isolates from neritic sea turtles were found to be more resistant to nitrofurans and aminoglycosides than isolates from oceanic sea turtles. Furthermore, isolates with a MAR pattern (p = 0.010) and those with a MAR index value greater than 0.2 (p = 0.027) were both found to be significantly positively associated with the mercury reductase (merA) gene.

CONCLUSIONS

The findings of our study indicate that co-selection of heavy metals and antimicrobial resistance may occur in aquatic bacteria in the coastal foraging habitats of sea turtles in Taiwan.

RETROSPECTIVE ANALYSIS OF BLOOD CULTURES AND THEIR ASSOCIATION WITH CLINICAL FINDINGS AND OUTCOME IN GREEN SEA TURTLES (CHELONIA MYDAS) AT A FLORIDA SEA TURTLE REHABILITATION FACILITY, 2017-2020

Septicemia is commonly suspected of sea turtles entering rehabilitation. However, blood culture results of green sea turtles (Chelonia mydas) are infrequently reported in the literature. Aerobic blood cultures were performed for intake examinations of 167 green sea turtles undergoing rehabilitation at Brevard Zoo's Sea Turtle Healing Center, Melbourne, Florida, USA from 2017 to 2020. The incidence of positive cultures during intake examinations was 24% (40/167). The most common bacterial isolates identified were Vibrio alginolyticus, Shewanella algae, Achromobacter xylosoxidans, Photobacterium damselae, Sphingomonas paucimobilis, and Vibrio parahaemolyticus. There was a statistically significant association (P < 0.05) between culture status and evidence of external injury. There was no significant association between culture status and Caryospora-like coccidia infection, or fibropapillomatosis. Culture-positive turtles had significantly lower (P < 0.05) total white blood cell, lymphocyte, monocyte, total protein, albumin, and calculated globulin values compared to turtles with negative blood cultures. Significantly more culture-positive turtles died in rehabilitation compared to culture-negative (P = 0.042). Positive blood cultures suggestive of septicemia are commonly found during intake examinations at a Florida sea turtle rehabilitation facility.

Microbial composition of carapace, feces, and water column in captive juvenile green sea turtles with carapacial ulcers

Introduction

Green sea turtles are endangered marine reptiles. Carapacial ulcers will develop on juvenile green sea turtles during artificial rescue, seriously affecting their health and potentially leading to death.

Methods

To determine the pathogens causing ulcerative carapacial disease, we performed 16S and ITS high-throughput sequencing, and microbial diversity analysis on samples from carapacial ulcers, healthy carapaces, feces, and seawater of juvenile green sea turtles.

Results

Our analysis showed that changes in microbial diversity of green sea turtle feces and seawater were not significantly associated with ulcerative carapacial disease.

Discussion

Psychrobacter sp. is the dominant species in the carapacial ulcers of green sea turtles. The bacterium is present in both healthy turtles and seawater where carapacial ulcers did not occur and decreasing seawater temperatures are likely responsible for the infection of juvenile green turtles with Psychrobacter sp. This is the first study on carapacial ulcers in captive juvenile green sea turtles. Our research provides theoretical guidance for the prevention and control of carapacial ulcers in captive juvenile green sea turtles.

Bacterial and fungal pathogens in granulomatous lesions of Chelonia mydas in a significant foraging ground off southern Brazil

The green sea turtle Chelonia mydas inhabit near-shore areas exposed to threatening anthropogenic activities. The granulomatous lesions in these animals may indicate infectious diseases that can be associated with environmental contamination and hazards to human health. This study aimed to characterize the granulomatous inflammation associated with bacterial and fungal infection in C. mydas off Paraná state. From September 2015 to February 2019, systematic monitoring was performed by the Santos Basin Beach Monitoring Project for sea turtles'carcasses recovery, necropsy, and cause of death diagnosis. The tissue samples were fixed in buffered formalin 10% for histochemical analysis and frozen for molecular analysis to fungi detection (Internal Transcribed Spacer region of the nuclear rDNA) and bacteria detection (16S ribosomal gene). From a total of 270 C. mydas, granulomatous lesions were observed in different organs of 63 (23.3%) individuals. The histological analysis indicated lesions in 94 organs, affecting most respiratory and digestive systems. Bacteria were identified in 25 animals, including an acid-fast bacteria detected in one animal, and fungi in 24 C. mydas. The fungi species included the genus Candida (Candida zeylanoides, n = 3), Yarrowia (Yarrowia lipolytica, n = 9; Yarrowia deformans, n = 5; and Yarrowia divulgata, n = 1), and Cladosporium anthropophilum (n = 1). No species of bacteria was identified by molecular testing. All fungi species identified are saprobic, some are important to food and medical industries, but are also pathogens of humans and other animals. Therefore, long-term monitoring of these pathogens and the C. mydas health may indicate changes in environmental quality, possible zoonotic diseases, and their effects.

Antimicrobial Resistance in Loggerhead Sea Turtles (Caretta caretta): A Comparison between Clinical and Commensal Bacterial Isolates

Simple Summary

Gram negative organisms are frequently isolated from Caretta caretta and may contribute to the dissemination of antimicrobial resistance. In this study, commensal bacteria isolated from oral and cloacal samples of 98 healthy C. caretta were compared to clinical isolates isolated from the wounds of 102 injured animals, in order to investigate the presence of antimicrobial resistance bacteria in free-living loggerheads from the Adriatic Sea. A total of 410 bacteria were cultured and differences were noted in the isolated genera, as some of them were isolated only in healthy animals, while others were isolated only from injured animals. When tested for susceptibility to antimicrobials, clinical isolates showed highly significant differences in the antimicrobial resistance rates vs. commensal isolates for all the drugs tested, except for doxycycline. The detection of high antimicrobial resistance rates in loggerhead sea turtles is of clinical and microbiological significance since it impacts both the choice of a proper antibiotic therapy and the implementation of conservation programs.

Abstract

Gram negative organisms are frequently isolated from Caretta caretta turtles, which can act as reservoir species for resistant microorganisms in the aquatic environment. C. caretta, which have no history of treatment with antimicrobials, are useful sentinel species for resistant microbes. In this culture-based study, commensal bacteria isolated from oral and cloacal samples of 98 healthy C. caretta were compared to clinical isolates from the wounds of 102 injured animals, in order to investigate the presence of AMR bacteria in free-living loggerheads from the Adriatic Sea. A total of 410 isolates were cultured. Escherichia coli and genera such as Serratia, Moraxella, Kluyvera, Salmonella were isolated only in healthy animals, while Acinetobacter, Enterobacter, Klebsiella and Morganella were isolated only from the wounds of the injured animals. When tested for susceptibility to ampicillin, amoxicillin + clavulanic acid, ceftazidime, cefuroxime, gentamicin, doxycycline, ciprofloxacin and enrofloxacin, the clinical isolates showed highly significant differences in AMR rates vs. commensal isolates for all the drugs tested, except for doxycycline. The detection of high AMR rates in loggerheads is of clinical and microbiological significance since it impacts both the choice of a proper antibiotic therapy and the implementation of conservation programs.

Antibiotic-Resistant Bacteria in Green Turtle (Chelonia mydas) Rearing Seawater

Simple Summary

The Sea Turtle Conservation Center of Thailand (STCCT) has conducted an early intervention program for conservation and faced high mortality rates due to bacterial diseases. Our previous investigation of juvenile turtle carcasses and sea water in the turtle hold tanks implied an association between bacterial isolates in rearing water and infection in captive turtles. In this study, for a management plan of juvenile sea turtles with bacterial infection, we monitored antibiotic resistance of bacteria in seawater from juvenile green turtle holding tanks at STCCT in three periods: January 2015 to April 2016, January to April 2018, and January to April 2019. The results clearly indicated that numbers of resistant bacteria and antibiotics were increased. Assessment of resistance against ten antibiotics revealed high prevalence of antibiotic-resistant bacteria to the beta-lactam class (ampicillin, penicillin, and cefazolin), whereas low resistant isolate numbers were found to aminoglycosides. From the results of this study, we suggest that antibiotic-resistant bacterial assessment in sea turtle rearing seawater will provide important information for the treatment of bacteria-infected sea turtles in husbandry.

Abstract

Antibiotic resistance of microorganisms is a serious health problem for both humans and animals. Infection of these bacteria may result in therapy failure, leading to high mortality rates. During an early intervention program process, the Sea Turtle Conservation Center of Thailand (STCCT) has faced high mortality rates due to bacterial infection. Previously, investigation of juvenile turtle carcasses found etiological agents in tissue lesions. Further determination of sea water in the turtle holding tanks revealed a prevalence of these causative agents in water samples, implying association of bacterial isolates in rearing water and infection in captive turtles. In this study, we examined the antibiotic resistance of bacteria in seawater from the turtle holding tank for a management plan of juvenile turtles with bacterial infection. The examination was carried out in three periods: 2015 to 2016, 2018, and 2019. The highest isolate numbers were resistant to beta-lactam, whilst low aminoglycoside resistance rates were observed. No gentamicin-resistant isolate was detected. Seventy-nine isolates (71.17%) were resistant to at least one antibiotic. Consideration of resistant bacterial and antibiotic numbers over three sampling periods indicated increased risk of antibiotic-resistant bacteria to sea turtle health. Essentially, this study emphasizes the importance of antibiotic-resistant bacterial assessment in rearing seawater for sea turtle husbandry.

Antimicrobial-resistance profiles of gram-negative bacteria isolated from green turtles (Chelonia mydas) in Taiwan

The green turtle (Chelonia mydas) is listed as a globally endangered species and is vulnerable to anthropogenic threats, including environmental pollution. This study investigated the antimicrobial resistance of Gram-negative bacteria isolated from wild green turtles admitted to a sea turtle rehabilitation center in Taiwan. For this investigation, cloacal and nasal swab samples were collected from 28 green turtles between 2018 and 2020, from which a total of 47 Gram-negative bacterial isolates were identified. Among these, Vibrio spp. were the most dominant isolate (31.91%), and 89.36% of the 47 isolates showed resistance to at least one of 18 antimicrobial agents tested. Isolates resistant to one (6.38%), two (8.51%), and multiple (74.47%) antimicrobials were observed. The antimicrobial agents to which isolates showed the greatest resistance were penicillin (74.47%), followed by spiramycin, amoxicillin, and cephalexin. The antimicrobial-resistance profiles identified in this study provide useful information for the clinical treatment of sea turtles in rehabilitation facilities. The results of our study also imply that wild green turtles may be exposed to polluting effluents containing antimicrobials when the turtles traverse migratory corridors or forage in feeding habitats. To benefit sea turtle conservation, future research should focus on (1) how to prevent pollution from antimicrobials in major green turtle activity areas and (2) identifying sources of antimicrobial-resistant bacterial strains in coastal waters of Taiwan.

Health assessment of wild speckled dwarf tortoises, CHERSOBIUS SIGNATUS

BACKGROUND

In free-ranging reptile populations, bacterial, fungal, viral and parasitic pathogens may affect hosts through impairment in movements, thermoregulation, reproduction, survival, and population dynamics. The speckled dwarf tortoise (Chersobius [Homopus] signatus) is a threatened species that is mostly restricted to the Succulent Karoo biome in South Africa, and little information on pathogens of this species is available yet. We derived baseline parameters for five males and five females that were captured to genetically enhance a conservation breeding program in Europe. Upon collection of the tortoises, ticks were removed and identified. Immediately upon arrival in Europe, ocular, nasal, oral and cloacal swabs were taken for viral, bacteriological and mycological examinations. Fecal samples were collected before and 1 month after fenbendazole treatment, and analyzed for parasites. A panel of PCR, aiming to detect herpesviruses, adenoviruses and iridoviruses, was carried out.

RESULTS

Samples were negative for viruses, while bacteriological examination yielded detectable growth in 82.5% of the swabs with a mean load of 16 × 107 ± 61 × 108 colony forming units (CFU) per swab, representing 34 bacterial species. Cloacal and oral swabs yielded higher detectable growth loads than nasal and ocular swabs, but no differences between sexes were observed. Fungi and yeasts (mean load 5 × 103 ± 13 × 103 CFU/swab) were detected in 25% of the swabs. All pre-treatment fecal samples were positive for oxyurid eggs, ranging from 200 to 2400 eggs per gram of feces, whereas after the treatment a significantly reduced egg count (90-100% reduction) was found in seven out of 10 individuals. One remaining individual showed 29% reduction, and two others had increased egg counts. In five tortoises, Nycthocterus spp. and coccidian oocysts were also identified. Soft ticks were identified as Ornithodoros savignyi.

CONCLUSIONS

Our baseline data from clinically healthy individuals will help future studies to interpret prevalences of microorganisms in speckled dwarf tortoise populations. The study population did not appear immediately threatened by current parasite presence.

Diagnosis and Treatment of Pulmonary Disease in Sea Turtles (Caretta caretta)

The aim of this study was to describe the clinical signs, radiographic, endoscopic and CT findings, cytological and microbiological findings and treatments of pulmonary diseases in sea turtles, in order to obtain an accurate diagnosis that avoids unnecessary therapy and antibiotic-resistance phenomena. In total, 14 loggerheads (Caretta caretta), with clinical and/or radiographic findings of pulmonary pathology, were assessed through various combinations of clinical, radiological, CT, endoscopic examination and bronchoalveolar lavage, which recovered fluid for cytologic and microbiologic analysis. In all cases, radiographic examination led to a diagnosis of pulmonary disorders-4 unilateral and 10 bilateral. All bacteria cultured were identified as Gram-negative. Antibiotic resistance was greater than 70% for all beta-lactams tested. In addition, all bacterial strains were 100% resistant to colistin sulfate and tetracycline. Specific antibiotic therapies were formulated for seven sea turtles using Enrofloxacin, and for four sea turtles using ceftazidime. In two turtles, antibiotic therapy was not included due to the presence of antibiotic resistance against all the antibiotics evaluated. In both cases, the coupage technique and environmental management allowed the resolution of the lung disease without antibiotics. All 14 sea turtles were released back into the sea. Radiographic examination must be considered the gold standard for screening sea turtles that show respiratory signs or abnormal buoyancy. Susceptibility testing with antimicrobials allowed appropriate therapy, including the reduction of antibiotic-resistance.

The Occurrence of Vibrionaceae, Staphylococcaceae, and Enterobacteriaceae in Green Turtle Chelonia mydas Rearing Seawater

In this study, levels of Vibrionaceae, Staphylococcaceae, and Enterobacteriaceae were observed in seawater from juvenile green turtle Chelonia mydas rearing tanks and in the incoming coastal seawater (the water supply). Bacterial loads were compared between the incoming coastal seawater and two different rearing conditions: in cement tanks at a low stocking density and in fiberglass tanks at a high stocking density. The total bacterial counts in seawater from fiberglass tanks were statistically greater than those in cement tanks. The nonlactose and lactose fermenting enterobacteria, tellurite-reducing bacteria, and total plate counts in water from all rearing containers were greater than those in coastal seaweater by a logarithmic fold change of 2--3. Differences in bacterial population structure of the incoming coastal seawater and rearing water were also addressed. The results from biochemical identification of 344 isolates revealed that the bacteria that were commonly found in water samples were Citrobacter spp., Enterobacteria spp., Edwardsiella spp., Staphylococcus spp., Staphylococcus aureus, Photobacterium spp., Vibrio alginolyticus, and Vibrio spp. Conclusively, the microbiological monitoring of rearing water provides important and essential information on the management of aquatic animal health and husbandry.

Monoclonal antibodies against loggerhead sea turtle, Caretta caretta, IgY isoforms reveal differential contributions to antibody titers and relatedness among other sea turtles

Serum from loggerhead sea turtles, Caretta caretta, was collected from the southeast Atlantic Ocean during routine summer monitoring studies in 2017. Serum immunoglobulin IgY was purified and used to develop IgY isoform-specific monoclonal antibodies (mAb). mAb LH12 was developed against the 66 kDa heavy chain of IgY, mAb LH1 was developed against the truncated heavy chain of approximately 37 kDA, and mAb LH9 was developed against the 23 kDa light chains. mAb LH9 reacts with the light chains of all sea turtles, mAb LH12 reacts with the long heavy chain of all sea turtles within the family Cheloniidae, and mAb LH1 reacts with the truncated form of IgY in both olive and Kemp's ridley turtles. Circulating IgY antibodies against three different marine bacterial pathogens were determined in 16 loggerhead samples using these mAbs. mAb LH12 detects higher titers than mAb LH1, and mAb LH9 detects the highest titers.

Fecal bacterial communities of wild-captured and stranded green turtles (Chelonia mydas) on the Great Barrier Reef

Green turtles (Chelonia mydas) are endangered marine herbivores that break down food particles, primarily sea grasses, through microbial fermentation. However, the microbial community and its role in health and disease is still largely unexplored. In this study, we investigated and compared the fecal bacterial communities of eight wild-captured green turtles to four stranded turtles in the central Great Barrier Reef regions that include Bowen and Townsville. We used high-throughput sequencing analysis targeting the hypervariable V1-V3 regions of the bacterial 16S rRNA gene. At the phylum level, Firmicutes predominated among wild-captured green turtles, followed by Bacteroidetes and Proteobacteria. In contrast, Proteobacteria (Gammaproteobacteria) was the most significantly dominant phylum among all stranded turtles, followed by Bacteroidetes and Firmicutes. In addition, Fusobacteria was also significantly abundant in stranded turtles. No significant differences were found between the wild-captured turtles in Bowen and Townsville. At the family level, the core bacterial community consisted of 25 families that were identified in both the wild-captured and stranded green turtles, while two unique sets of 14 families each were only found in stranded or wild-captured turtles. The predominance of Bacteroides in all groups indicates the importance of these bacteria in turtle gut health. In terms of bacterial diversity and richness, wild-captured green turtles showed a higher bacterial diversity and richness compared with stranded turtles. The marked differences in the bacterial communities between wild-captured and stranded turtles suggest the possible dysbiosis in stranded turtles in addition to potential causal agents.

Humoral Immune Responses to Select Marine Bacteria in Loggerhead Sea Turtles Caretta caretta and Kemp's Ridley Sea Turtles Lepidochelys kempii from the Southeastern United States

Serum from Kemp's ridley sea turtles Lepidochelys kempii and loggerhead sea turtles Caretta caretta was collected during summer in 2011, 2012, and 2013. Serum immunoglobulin Y (IgY) recognition of lysate proteins from nine bacterial species and whole bacterium-specific IgY titers to these pathogens were quantified. Serum and purified IgY recognized proteins of all bacteria, with protein recognition for some species being more pronounced than others. Circulating IgY titers against Vibrio vulnificus, V. anguillarum, Erysipelothrix rhusiopathiae, and Brevundimonas vesicularis changed over the years in Kemp's ridley sea turtles, while IgY titers against V. vulnificus, Escherichia coli, V. parahaemolyticus, B. vesicularis, and Mycobacterium marinum were different in loggerhead sea turtles. Serum lysozyme activity was constant for loggerhead sea turtles over the 3 years, while activity in Kemp's ridley sea turtles was lower in 2011 and 2012 than in 2013. Blood packed cell volume, glucose, and serum protein levels were comparable to those of healthy sea turtles in previous studies; therefore, this study provides baseline information on antibody responses in healthy wild sea turtles.

Aerobic bacterial microbiota isolated from the cloaca of the European pond turtle (Emys orbicularis) in Poland

We conducted a comparative analysis of the aerobic cloacal bacteria of European pond turtles (Emys orbicularis) living in their natural environment and juvenile turtles reared under controlled conditions in a breeding center. We included 130 turtles in the study. The aerobic bacteria isolated from the cloaca of the juvenile turtles were less diverse and more prevalent than the bacteria isolated from free-living adults. We isolated 17 bacterial species from juvenile captive turtles, among which the dominant species were Cellulomonas flavigena (77/96), Enterococcus faecalis (96/96), Escherichia coli (58/96), and Proteus mirabilis (41/96). From the adult, free-living turtles, we isolated 36 bacterial species, some of which are a potential threat to public health (e.g., Salmonella enterica serovars Newport, Daytona, and Braenderup; Listeria monocytogenes; Yersinia enterocolitica; Yersinia ruckeri; Klebsiella pneumoniae; Vibrio fluvialis; and Serratia marcescens), and pathogens that are etiologic agents of diseases of ectothermic animals (e.g., Aeromonas sobria, Aeromonas caviae, Hafnia alvei, Edwardsiella tarda, and Citrobacter braakii; the last two species were isolated from both groups of animals). The cloacal bacterial biota of the European pond turtle was characterized by numerous species of bacteria, and its composition varied with turtle age and environmental conditions. The small number of isolated bacteria that are potential human pathogens may indicate that the European pond turtle is of relatively minor importance as a threat to public health.