Initial antibiotic therapy for alligator bites: characterization of the oral flora of Alligator mississippiensis

Delayed Medical Care Following an Alligator Bite: A Case Report and Literature Review

Alligator bites in humans present a significant concern for public safety in the southern United States, especially in states like Florida with substantial alligator populations. Although these reptiles play a vital role in the local ecology, encounters with humans can lead to severe injuries and even fatalities. A case report is presented of a 58-year-old male who suffered an alligator bite while attempting to take a selfie with the reptile during a hunting trip in rural Florida. The patient's injuries included multiple lacerations on the dorsum of his right hand. Despite the incident, the patient hesitated in seeking medical attention due to a lack of insurance, emphasizing the need for public awareness of alligator bite management. The discussion highlights the potential complications of alligator bites, including hemorrhage and infection, as well as the importance of appropriate medical treatment, including wound irrigation, debridement, and antibiotic therapy. Moreover, preventive strategies are discussed, such as maintaining a safe distance from alligators and refraining from feeding them, to ensure coexistence between humans and these reptiles in their natural habitats. As knowledge of alligator bites remains limited, this case report contributes valuable information to promote public safety and guide future research in this area.

Novel Alligator Cathelicidin As-CATH8 Demonstrates Anti-Infective Activity against Clinically Relevant and Crocodylian Bacterial Pathogens

Host defense peptides (HDPs) represent an alternative way to address the emergence of antibiotic resistance. Crocodylians are interesting species for the study of these molecules because of their potent immune system, which confers high resistance to infection. Profile hidden Markov models were used to screen the genomes of four crocodylian species for encoded cathelicidins and eighteen novel sequences were identified. Synthetic cathelicidins showed broad spectrum antimicrobial and antibiofilm activity against several clinically important antibiotic-resistant bacteria. In particular, the As-CATH8 cathelicidin showed potent in vitro activity profiles similar to the last-resort antibiotics vancomycin and polymyxin B. In addition, As-CATH8 demonstrated rapid killing of planktonic and biofilm cells, which correlated with its ability to cause cytoplasmic membrane depolarization and permeabilization as well as binding to DNA. As-CATH8 displayed greater antibiofilm activity than the human cathelicidin LL-37 against methicillin-resistant Staphylococcus aureus in a human organoid model of biofilm skin infection. Furthermore, As-CATH8 demonstrated strong antibacterial effects in a murine abscess model of high-density bacterial infections against clinical isolates of S. aureus and Acinetobacter baumannii, two of the most common bacterial species causing skin infections globally. Overall, this work expands the repertoire of cathelicidin peptides known in crocodylians, including one with considerable therapeutic promise for treating common skin infections.

Incubation determines favorable microbial communities in Chinese alligator nests

Nest materials are a major heat source due to rotting promoted by microbial activity. Additionally, they are a potential microbial source given their direct contact with eggshells. Microbial dynamics during incubation have been studied in wild birds; however, similar studies in reptiles remain elusive. Here, the study characterized microbial communities in the nest materials of Chinese alligator (Alligator sinensis) using high-throughput sequencing of bacterial 16S rRNA genes and fungal internal transcribed spacer (ITS) region sequences. The results showed that significant changes in the diversity and structure of microbial communities according to different incubation periods. The diversity and richness of bacterial species increased significantly over time, but the relative abundance of the most dominant bacteria in pre-incubation period, including some pathogenic bacteria, declined after incubation. In contrast, fungal species diversity and richness decreased significantly with time. Additionally, nest material composition significantly influenced microbial community structure rather than species diversity and richness. Notably, the fungal community structure showed a stronger response than bacteria to nest material composition, which varied due to differences in plant litter composition. Our results demonstrate the significant response of microbial community diversity and structure to differences in incubation periods and nest material composition in reptiles. It is further emphasized that the importance of incubation period in the conservation of the Chinese alligator and could inform similar studies in other reptiles and birds.

A Rare Case of Limb-Threatening Injury Secondary to Extrinsic Vascular Compression Following Crocodile Bite

Crocodile bites lead to fatal and nonfatal outcomes in humans. Mugger crocodiles (Crocodylus palustris) and saltwater crocodiles (Crocodylus porosus) are common in India. Most crocodile bites can cause severe injuries, especially to the extremities, due to the substantial bite force of the crocodile, which typically leads to extensive tissue damage, fractures, amputations, and vascular injuries. We report the case of a crocodile bite victim who presented with features of acute limb ischemia, was found to have vascular thrombosis of the common femoral artery, and was experiencing complete compression of the femoral vein due to external vascular compression by a hematoma. We discuss various injury mechanisms sustained in crocodile bites and the roles of point-of-care ultrasound and continuous tomography angiography, which could help identify these injuries. After thrombectomy and hematoma evacuation the patient recovered and was discharged without any physical dysfunction.

Identification of a crocodylian β-defensin variant from Alligator mississippiensis with antimicrobial and antibiofilm activity

β-defensin host defense peptides are important components of the innate immune system of vertebrates. Although evidence of their broad antimicrobial, antibiofilm and immunomodulatory activities in mammals have been presented, β-defensins from other vertebrate species, like crocodylians, remain largely unexplored. In this study, five new crocodylian β-defensin variants from Alligator mississippiensis and Crocodylus porosus were selected for synthesis and characterization based on their charge and hydrophobicity values. Linear peptides were synthesized, folded, purified and then evaluated for their antimicrobial and antibiofilm activities against the bacterial pathogens, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, Enterobacter cloacae and Acinetobacter baumannii. The Am23SK variant (SCRFSGGYCIWNWERCRSGHFLVALCPFRKRCCK) from A. mississippiensis displayed promising activity against both planktonic cells and bacterial biofilms, outperforming the human β-defensin 3 under the experimental conditions. Moreover, Am23SK exhibited no cytotoxicity towards mammalian cells and exerted immunomodulatory effects in vitro, moderately suppressing the production of proinflammatory mediators from stimulated human bronchial epithelial cells. Overall, our results have expanded the activity landscape of crocodylian and reptilian β-defensin in general.

Systemic Granulomatous Pathology in Two Captive Alligator Mississippiensis

The literature in this field cites various ubiquitous fungal and bacterial microorganisms as etiologic agents in severely stressed captive alligators and crocodiles. This study reports two cases of Alligator mississippiensis with bacterial and fungal disease. Two adult American alligators have been submitted for post-mortem investigations. Necropsy, cytology (MGG), and histopathology investigations (HE, HEA, PAS, Gram, Giemsa, Ziehl Neelsen) were carried out. Pleural and pericardial swabs were subjected to microbiological examination. The main lesions detected involved the lower respiratory system and were characterized by thoracic serosanguineous effusions, pleural and pulmonary nodules (1 – 80 mm), accompanied by edema. Similar nodules observed also in the liver, spleen and myocardium, suggested a systemic disease. Additionally, cutaneous, gingival and gastrointestinal erosions and ulcers were found. Cytoarchitecture findings in the major organs revealed lymphoid depletion, multifocal to coalescing necrotic areas with coccoid aggregates and rod shaped bacteria intermixing fungal structures, boarded by heterogeneous inflammatory infiltrates, composed by epithelioid macrophages, lymphocytes and heterophils. The microbiological examination revealed the presence of Aeromonas hydrophila, A. caviae, Serratia marcescens, Pantoea agglomerans, Proteus vulgaris, haemolitic and non-haemolitic E. coli, Citrobacter freundii, Rhizopus/Absidia from pleural and pericardial cavities, concluding that death occurred following a bacterial and fungal pneumonia, with secondary spreading of microorganisms. Along with the low immune response, severe stress was the main possible cause, as a result of environmental temperature changes during the winter, as well as other husbandry issues.

Cathelicidin antimicrobial peptide from Alligator mississippiensis has antibacterial activity against multi-drug resistant Acinetobacter baumanii and Klebsiella pneumoniae

Alligator mississippiensis (American alligator), a member of order Crocodilia, lives in bacteria-laden environments but is not often known to succumb to bacterial infections. Their serum has been shown to have antibacterial activity beyond that of human serum, and it is believed that this activity is partially due to cationic antimicrobial peptides (CAMPs). CAMPs are produced by many organisms as part of the innate immune system. CAMPs are attractive possible therapies against multi-drug resistant bacteria, such as those found in biofilm-infected war wounds, because they seldom cause genetic resistance in bacteria and are effective against antibiotic resistant bacteria. In this work, we identified, synthesized, and characterized a cathelicidin and two shorter fragments from the American alligator. We discovered the cathelicidin using Basic Local Alignment Search Tool (BLAST) alignment and by comparing A. mississippiensis expressed sequence tags (ESTs) with propeptide cathelicidins of other reptiles. We analyzed the structure using bioinformatics tools and circular dichroism and predicted that the full-length cathelicidin peptide has a mixed structure, with an N-terminal α-helix and a center Pro hinge. In minimal inhibitory concentration (MIC) assays, it was determined that the cathelicidin and the two shorter fragments have strong activity against multiple Gram-negative bacteria, including clinical isolates of multi-drug resistant (MDR) Acinetobacter baumannii and carbapenem-resistant Klebsiella pneumoniae. Using the ethidium bromide uptake assay, it was found that these peptides permeabilize the bacterial membrane and are less sensitive to salt inhibition than many other known CAMPs. The alligator cathelicidin peptides were not hemolytic against sheep red blood cells at 300 μg/ml and were not significantly cytotoxic against A549 human lung epithelial cells after 24 h exposure in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. These alligator cathelicidin peptides have activity similar to other CAMPs from reptiles such as NA-CATH. It is possible that the alligator cathelicidins play an important role in the innate immune response of A. mississippiensis, similar to LL-37 in humans. In addition, due to their activities against MDR bacteria and lack of cytotoxicity, the AM-CATH peptides could be an attractive platform for further development as a potential therapeutic.

An urban Northeastern United States alligator bite

Individuals who live and work in the Southeastern coastal range of the 3 US crocodilian carnivores, American alligators, American crocodiles, and caiman, understand the risks of reptile-human encounters. Individuals who live in other parts of the country maybe exposed through contact with exotic pets at private homes, small menageries, or petting zoos or from escaped or abandoned animals. During these encounters, individuals may be severely injured.Emergency medical services, law enforcement, and animal welfare workers in nonhabitat areas are usually not trained in the handling and safe removal of injured individuals from the scene when the reptile is present. The emergency management of large crocodilian injuries is similar to that of other major trauma; however, providers also must take into consideration the significant crush component potentially inflicted by the tremendous bite power and shaking inflicting during attacks by these large reptiles, appropriate antibiotic coverage for less common organisms that inhabit their mouths, and management of possible psychological distress, including posttraumatic stress disorder produced by such an unusual attack. Emergency physicians should support the development of a readily available national database of scientifically collect information on attacks to inform appropriate care and support efforts to explore responsible measures that the USDA Animal and Plant Health Inspection Service and other appropriate local, state, and federal agencies can take to ensure ethical and biologically sustainable management of our large reptiles, which also helps to ensure the safety of the public.

Anaerobic and aerobic bacteriology of the saliva and gingiva from 16 captive Komodo dragons (Varanus komodoensis): new implications for the "bacteria as venom" model

It has been speculated that the oral flora of the Komodo dragon (Varanus komodoensis) exerts a lethal effect on its prey; yet, scant information about their specific oral flora bacteriology, especially anaerobes, exists. Consequently, the aerobic and anaerobic oral bacteriology of 16 captive Komodo dragons (10 adults and six neonates), aged 2-17 yr for adults and 7-10 days for neonates, from three U.S. zoos were studied. Saliva and gingival samples were collected by zoo personnel, inoculated into anaerobic transport media, and delivered by courier to a reference laboratory. Samples were cultured for aerobes and anaerobes. Strains were identified by standard methods and 16S rRNA gene sequencing when required. The oral flora consisted of 39 aerobic and 21 anaerobic species, with some variation by zoo. Adult dragons grew 128 isolates, including 37 aerobic gram-negative rods (one to eight per specimen), especially Enterobacteriaceae; 50 aerobic gram-positive bacteria (two to nine per specimen), especially Staphylococcus sciuri and Enterococcusfaecalis, present in eight of 10 and nine of 10 dragons, respectively; and 41 anaerobes (one to six per specimen), especially clostridia. All hatchlings grew aerobes but none grew anaerobes. No virulent species were isolated. As with other carnivores, captive Komodo oral flora is simply reflective of the gut and skin flora of their recent meals and environment and is unlikely to cause rapid fatal infection.

Oral and cloacal microflora of wild crocodiles Crocodylus acutus and C. moreletii in the Mexican Caribbean

Bacterial cultures and chemical analyses were performed from cloacal and oral swabs taken from 43 American crocodiles Crocodylus acutus and 28 Morelet's crocodiles C. moreletii captured in Quintana Roo State, Mexico. We recovered 47 bacterial species (28 genera and 14 families) from all samples with 51.1% of these belonging to the family Enterobacteriaceae. Fourteen species (29.8%) were detected in both crocodile species and 18 (38.3%) and 15 (31.9%) species were only detected in American and Morelet's crocodiles, respectively. We recovered 35 bacterial species from all oral samples, of which 9 (25.8%) were detected in both crocodile species. From all cloacal samples, we recovered 21 bacterial species, of which 8 (38.1%) were detected in both crocodile species. The most commonly isolated bacteria in cloacal samples were Aeromonas hydrophila and Escherichia coli, whereas in oral samples the most common bacteria were A. hydrophila and Arcanobacterium pyogenes. The bacteria isolated represent a potential threat to crocodile health during conditions of stress and a threat to human health through crocodile bites, crocodile meat consumption or carrying out activities in crocodile habitat. We especially warn about the presence of Salmonella arizonae and S. typhi, which cause enteritis and septicemia in crocodiles and salmonellosis and typhoid fever in humans. The risk of bacterial contamination from crocodiles to humans could increase in the future because of the accelerated destruction of crocodile habitat, which could lead to an augmentation of human-crocodile interactions. Information on bacterial diversity reported here could help in the choice of antibacterial products in case of infections that are of crocodile origin.

Microbiology of animal bite wound infections

The microbiology of animal bite wound infections in humans is often polymicrobial, with a broad mixture of aerobic and anaerobic microorganisms. Bacteria recovered from infected bite wounds are most often reflective of the oral flora of the biting animal, which can also be influenced by the microbiome of their ingested prey and other foods. Bacteria may also originate from the victim's own skin or the physical environment at the time of injury. Our review has focused on bite wound infections in humans from dogs, cats, and a variety of other animals such as monkeys, bears, pigs, ferrets, horses, sheep, Tasmanian devils, snakes, Komodo dragons, monitor lizards, iguanas, alligators/crocodiles, rats, guinea pigs, hamsters, prairie dogs, swans, and sharks. The medical literature in this area has been made up mostly of small case series or case reports. Very few studies have been systematic and are often limited to dog or cat bite injuries. Limitations of studies include a lack of established or inconsistent criteria for an infected wound and a failure to utilize optimal techniques in pathogen isolation, especially for anaerobic organisms. There is also a lack of an understanding of the pathogenic significance of all cultured organisms. Gathering information and conducting research in a more systematic and methodical fashion through an organized research network, including zoos, veterinary practices, and rural clinics and hospitals, are needed to better define the microbiology of animal bite wound infections in humans.

Animal bite-associated infections: microbiology and treatment

Human and animal bites may lead to serious infection. The organisms involved tend to originate from the oral cavity of the offending biter, as well as the environment where the injury occurred. A variety of aerobic as well as anaerobic organisms have been isolated from bite wounds, with infection ranging from localized cellulitis to systemic dissemination, leading to severe disease ranging from abscess to bone and joint infection, to endocarditis and brain abscess. Immediate wound management, including recognition of the most commonly associated infectious pathogens, and judicious use of empiric antibiotics are crucial in providing the best care after a bite. Here, we discuss the common animal bite associated infections, and provide the most up to date information regarding their management.

CROCODILIANS

This chapter presents a general overview of the anatomy, physiology, and treatment methodology for crocodilians. Most crocodilians grow to be larger than other reptile species and, therefore, have significant space requirements. Like most animals requiring an aquatic environment, crocodilians need water that is clean and free of disease. Crocodilians have a true hard palate in the roof of the mouth that ends caudally in a soft palate. This soft palate has a ventral flap which is referred to as the velum palati. The respiratory system of crocodilians consists of well-developed lungs benefiting from a very effective inspiration aided by the intercostal muscles and the septum post hepaticum. Crocodilians have a four-chambered heart as opposed to the three-chambered heart found in other reptiles and amphibians. The temperature and humidity requirements for crocodilians in captivity vary with the species. An understanding of crocodilian biology and natural history is needed to try and duplicate their natural environment. An important consideration is the allowance of circadian variations in light cycle and temperatures to mimic their natural environment. This is not the case in many commercial operations, where they are maintained at a fairly constant temperature and humidity to achieve faster growth.

Pantoea agglomerans bacteremia in a 65-year-old man with acute myeloid leukemia: case report and review

A 65-year-old man with a recent history of acute leukemia was admitted with complaints of chills and rigors. He had a long-standing Hickman catheter which was removed following the isolation of a gram negative rod later identified as Pantoea agglomerans. The patient recovered with antimicrobial therapy. Pantoea species are rare causes of clinically relevant infections.

Isolation of Serratia fonticola from skin lesions in a Nile Crocodile (Crocodylus niloticus) with an associated septicaemia

This paper describes the first isolation of Serratia fonticola in a Nile Crocodile (Crocodylus niloticus). This organism was initially isolated from skin lesions and blood and subsequently from a variety of organs during necropsy. S. fonticola was confirmed as the pathogen causing the infection.

Alligator Attacks in Southwest Florida

The American alligator inhabits bodies of fresh water in Florida and other southeastern states. Although attacks on pets are frequent, alligator attacks on humans are relatively rare because of the animal's natural fear of man. Because of the rarity of attacks on humans, the pathologic findings and pathophysiology of death in such cases have not been well characterized in the literature. We report three cases of fatal alligator attacks that occurred in southwest Florida, each with different pathologic findings and mechanisms of death. Although the cause of death in each case was attributed to the alligator attack, the mechanisms of death differed and included exsanguination because of amputation of an extremity, overwhelming sepsis, and drowning. These cases illustrate the varied pathophysiologies associated with deaths due to alligator attacks on humans and the features that distinguish alligator bites from those of other aquatic predators.

Management of human and animal bite wounds: an overview

Serious infections can result from wounds that are caused by bites from animals and humans. Organisms recovered from bite wounds generally originate from the oral cavity of the biting animal, as well as from the patient's skin flora. Anaerobes have been isolated from animal and human bite wound infections, especially those associated with abscess formation. In addition to local wound infections, common complications, such as lymphangitis, septic arthritis, tenosynovitis, and osteomyelitis, and uncommon complications, such as endocarditis, meningitis, brain abscess, and sepsis, may occur. Wound management includes proper local care and, when needed, antimicrobial therapy.

Management of extremity trauma and related infections occurring in the aquatic environment

Wounds sustained in oceans, lakes, and streams are exposed to a milieu of bacteria rarely encountered in typical land-based injuries. These include Vibrio species, Aeromonas hydrophila, Pseudomonas and Plesiomonas species, Erysipelothrix rhusiopathiae, Mycobacterium marinum, and other microbes. Failure to recognize and treat these less common pathogens in a timely manner may result in significant morbidity or death. Initial antibiotic therapy should address common gram-positive and gram-negative aquatic bacteria, depending on the environment. Trauma occurring in brackish or salt water should be treated with doxycycline and ceftazidime, or a fluoroquinolone (eg, ciprofloxacin or levofloxacin). Freshwater wounds should be managed with ciprofloxacin, levofloxacin, or a third- or fourth-generation cephalosporin (eg, ceftazidime). Injuries sustained in a marine or freshwater environment may result from bites or venomous stings of aquatic organisms as well as from accidental trauma. Musculoskeletal trauma caused by venomous underwater species (eg, stingrays, stinging fish, sea urchins, and coral) requires immediate neutralization of the heat-labile toxin with immersion in nonscalding water for 30 to 90 minutes. Appropriate management of aquatic wounds requires recognition of the mechanism of injury, neutralization of venom, antibiotic administration, radiographic assessment, surgical débridement with irrigation, wound cultures, and structural repair or amputation as indicated by the severity of the injury.

Microbiology and management of human and animal bite wound infections

This article describes the microbiology, diagnosis, and management of human and animal bite wound infections. Various organisms can be recovered from bite wounds that generally result from aerobic and anaerobic microbial flora of the oral cavity of the biting animal, rather than the victim's own skin flora. The role of anaerobes in bite wound infections has been increasingly appreciated. Anaerobes were isolated from more than two thirds of human and animal bite wound infections, especially those associated with abscess formation. This article describes several of the organisms found in the bites of various species. In addition to local wound infection, other complications may occur, including lymphangitis, local abscess, septic arthritis, tenosynovitis, and osteomyelitis. Rare complications include endocarditis, meningitis, brain abscess, and sepsis with disseminated intravascular coagulation, especially in immunocompromised individuals. Wound management includes the administration of proper local care and the use of proper antimicrobial agents when needed.

Crocodile bite injury in southern Malawi

In Trinity Hospital, a district hospital in the south of Malawi, over a period of 4 years 60 patients were admitted following injury by crocodiles. All patients were treated by extensive surgical cleaning and debridement, anti-tetanus treatment and broad spectrum antibiotics. Twenty-four patients (40%) had serious injuries resulting in permanent deformity. Only one patient died from sepsis.

Surgical hazards posed by marine and freshwater animals in Florida

Marine and freshwater animals can cause injury to humans by biting, stinging, being poisonous to eat, and causing infections. Biting aquatic animals in Florida include sharks, barracudas, alligators, and moray eels. Devitalized tissue should be débrided, and vascular, neurologic, and tendinous injuries should be repaired. Radiographs should be obtained to examine the injury sit for fractures and retained foreign bodies (teeth). The spines of stingrays and marine catfish can cause soft tissue injury and infection. The spine has a recurved, serrated shape that may cause further injury and break if it is pulled out. The venom may cause local tissue necrosis requiring débridement. Soft tissue infections with marine Vibrio bacteria can occur after eating raw oysters or receiving even minor injuries from marine animals. Thirty-one individuals developed soft tissue infections, 49 developed sepsis, and 23 developed both sepsis and soft tissue infection with marine Vibrio species during a 12-year period. Sixteen patients developed necrotizing soft tissue infections. Treatment is with antibiotics and débridement when necrosis occurs.

Crocodile attacks in the Northern Territory of Australia

OBJECTIVE

To examine crocodile attacks in the Northern Territory with particular reference to risk factors, range of injuries, microorganisms isolated from wounds, and surgical management; and to make recommendations for optimal treatment.

DESIGN AND SETTING

The case notes of patients treated at the Royal Darwin Hospital within the last decade were reviewed retrospectively. Autopsy and newspaper reports for the same period were also reviewed.

RESULTS

There were 16 reported crocodile attacks in Northern Territory waters from June 1981 to June 1991. Four of these were fatal. Most attacks resulted from swimming or wading in shallow water (13/16). Half the victims were known to be affected by alcohol. The majority of attacks occurred in failing light or at night (10/16). Injuries in survivors ranged from minor lacerations and puncture wounds to major abdominal, chest and limb trauma. Death in fatal attacks was caused by transection of the torso or decapitation. Microorganisms isolated from wound swabs included Pseudomonas, Enterococcus, Aeromonas and Clostridium species.

CONCLUSIONS

Most attacks in this series could have been prevented by taking adequate precautions. The treatment of crocodile injuries must include (i) adequate wound cultures, (ii) antitetanus prophylaxis, (iii) meticulous wound debridement, (iv) appropriate broad spectrum prophylactic antibiotics and (v) allowing healing by secondary intention or delayed primary closure where appropriate.

Unusual case of Aeromonas hydrophila endocarditis

We describe a case of Aeromonas hydrophila endocarditis in a 66-year-old man with myelodysplastic syndrome and non-A, non-B hepatitis, The infection resolved with antibiotic therapy, but the patient succumbed to complications of his underlying illness. This is the second case of Aeromonas endocarditis reported in the world literature.