Tropical Doctor, October 1992
158
Bacteriology of snakebite abscess Kevin R Kerrigan MD FACS Hospital Vozandes Oriente Shell, Pastaza, Ecuador TROPICAL DOCTOR,
1992, 22, 158-160
SUMMARY
Thirty-eight cases of abscess secondary to pit viper envenomation are reviewed. The incidence of abscess formation was 9070. Results of aerobic cultures revealed growth of enteric, coliform organisms in 22 of 25 isolates obtained from previously unopened abscesses. Clinical evidence for co-existent anaerobic infection is presented. No cases of tetanus were encountered. Clinical and laboratory findings of patients in the study are correlated with a review of bacteriologic investigations of the oral flora of venomous snakes. Use of antibiotics effective against aerobic coliforms and histotoxic anaerobic organisms for prophylaxis and/or treatment of infectious complications of pit viper envenomation are recommended. INTRODUCTION
Venomous snakebite is a major cause of morbidity and mortality in many parts of the world. In the western hemisphere, most snakebite injuries are caused by members of the family Viperidae, subfamily Crotalidae, also known as pit vipers. In North America, pit vipers are represented by the genera Crotalus (rattlesnakes), Agkistrodan (moccasins) and Sistrurus (massasaugas and pygmy rattlers). In Ecuador, Crotalidae is represented by the genera Bothrops and Lachesis', Abscess formation at the site of envenomation is one of the most frequent and devastating complications of pit viper injuries", Current efforts to prevent infectious complications of pit viper bites include early debridement at the site of envenomation and use of prophylactic antibiotics. Early debridement of pit viper bites has been shown to decrease morbidity associated with local necrosis and/or infectionv". Unfortunately, adequate medical facilities and personnel needed to provide such treatment are often lacking in rural Correspondence to: Dr K R Kerrigan, Kijabe Medical Centre, PO Box 20, Kijabe, Kenya, East Africa.
areas of developing nations where the incidence of snakebite injuries is the highestv". The efficacy of administration of prophylactic antibiotics in reducing incidence or severity of infectious complications of snakebite injuries has never been documented. Much controversy persists with regards to the indications for and usage of prophylactic antibiotics in snakebite injuries!O-13. Once abscess formation occurs, adequate treatment requires prompt surgical drainage combined with administration of appropriate antibiotics. Choice of antibiotics for prophylaxis and/or treatment of established infection secondary to pit viper envenomation demands a knowledge of the responsible organisms. The current study reports the results of aerobic bacteriological cultures and antibiotic sensitivities of abscesses secondary to bites of the Ecuadorian pit vipers, Bothrops and Lachesis. All abscesses occurred amongst a group of 312 snakebite victims admitted to a single medical facility located in the Amazon rainforest of eastern Ecuador. METHODS
The admission records of Hospital Vozandes Oriente for the years 1980 to 1989 were screened and all patients with an admitting diagnosis of snakebite were reviewed. Of the 312 patients thus selected, 38 patients were found to have formed abscesses at the site of envenomation. RESULTS
Incidence Of the 312 patients presenting with a diagnosis of snakebite, 18 arrived later than 4 days post-bite (group 1). These patients presented for treatment of an established complication of the bite rather than for acute treatment of the bite itself. Twelve of these patients had abscesses at the time of admission. The remaining 294 patients arrived within 4 days of the bite and presented for treatment of the snakebite, per se (group 2). Delays in arrival were primarily related to transportation problems. Among this group, 26 abscesses occurred, an incidence of 9%. No case of tetanus was encountered. Epidemiological features of this group have previously been reported elsewhere-. BACTERIOLOGY
Aerobic cultures of abscess contents were obtained in 29 of the 38 cases. Facilities for anaerobic culture were not available and Gram stains of purulent
Downloaded from tdo.sagepub.com at UNIV OF MICHIGAN on May 19, 2015
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material were not obtained. Three of the cultures ANTIBIOTIC SENSITIVITIES obtained resulted in no bacterial growth, despite Susceptibility studies utilizing commercially available the finding of pus at the time of surgical sensitivity discs were performed on the bacterial isolates. Twenty of twenty-three isolates (87010) drainage. Of the 26 cases in which cultures demonstrated demonstrated susceptibility to chloramphenicol. bacterial growth, 23 were obtained at the time of Twenty of 26 isolates (77%) were found to be surgical drainage of previously unopened abscesses. susceptible to gentamicin. Excluding the isolates of Two of these cultures resulted in growth of more Staphylococcus aureus obtained from surface than one organism. The remaining three positive cultures of previously opened abscesses yields cultures were obtained from the surface of wounds susceptibility rates of 90% and 83% respectively. resulting from prior spontaneous drainage of Only five of 25 isolates (20%) were susceptible to abscess cavities. All surface cultures resulted in ampicillin and none of the six isolates tested was growth of Staphylococcus aureus. Of the 25 found to be susceptible to penicillin. surgicallyobtained isolates of previously undisturbed abscesses, one resulted in growth of a J3-haemolytic DISCUSSION streptococcus. Another specimen resulted in growth Venomous snakebite injuries represent contaminated of two isolates, a Gram positive bacillus and puncture wounds. The local effects of injected a Gram positive coccus, neither of which could be venom include haemorrhage and tissue destruction further identified with the laboratory facilities resulting in an ideal environment for bacterial available. The remaining 22 isolates demonstrated growth. Although tissue necrosis without infection growth of a variety of Gram negative rods ('dry gangrene') does occur, more commonly infection supervenes-. (Table I). The finding in the current study of Gram negative Although facilities to perform anaerobic cultures were not available during the time of this study, rods in the vast majority of the aerobic cultures there was a strong clinical suspicion of anaerobic supports the concept that the source of the bacterial involvement in the majority of cases. Foul-smelling inoculum in snakebite abscesses is the oral flora of pus was found at the time of surgical drainage in the offending snake. Furthermore, the mouth all cases of previously unopened abscesses. organisms found in these snakes reflects the fecal Subcutaneous emphysema was found preoperatively flora of their ingested preyr'. Laboratory investigaand/or gas bubbles encountered operatively in tions of the bacteriology of venom and oral cavities infected tissues of many cases. In a number of cases, of North American pit vipers has demonstrated a a progressive, necrotizing myositis occurred despite preponderance of enteric and coliform organisms early and apparently adequate surgical drainage and in aerobic isolates, with Aerobacter, Proteus and administration of appropriate antibiotics. Figure I Pseudomonas occurring most commonlyI4-16. Although the finding of gas formation in tissues shows the leg of a Waorani Indian man who developed crepitus in the bitten extremity 5 days of patients in this series is not diagnostic of anaerobic post-bite. Immediate drainage and administration of gentamicin and chloramphenicol failed to prevent necrotizing myositis of the tibialis anterior and the extensors digitorum longus and hallucis longus muscles. Table 1. Aerobic bacterial isolates from 26 cases of snakebite abscess Gram negative rods" Enterobacter E. coli Serratia Proteus Total ·not further identified
9 5 4 3
Beta strep Gram positive rods" Gram positive cocci"
I
Staphylococcus aureus
3
Total
6
22
Figure 1. The leg of a Waorani Indian man who developed crepitus in the bitten extremity 5 days post bite
Downloaded from tdo.sagepub.com at UNIV OF MICHIGAN on May 19, 2015
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infection, the clinical suspicion of co-existent infection with anaerobic organisms which are gasproducing and tissue destructive is also consistent with results of laboratory investigations. Goldstein et 01. 14 found Clostridium to be the most common anaerobic genus isolated from the oral flora of 15 rattlesnakes. Ledbetter and Kutscher'>, in studying 100 rattlesnakes, isolated Clostridia from 48070 of venom and 86070 of fang specimens. Histotoxic species capable of producing gas gangrene were found in half the snakes. The authors felt that 'the potentially histotoxic clostridia are so commonly present in the venom and oropharynx of rattlesnakes that all bites with extensive necrosis should be treated with antibiotics effective against clostridia' 15. Bacteriologic studies of the oral flora of snakes other than North American pit vipers yield similar results. Williams et 01. 17 isolated coliform bacilli from the mouths of 73% of a variety of Australian snakes. Clostridia were recovered from the mouths of all of the 49 snakes they studied!". There are no reports of laboratory investigation of the bacteriology of snakes' mouths which document isolation of Clostridium tetani. The present report confirms the low incidence of tetanus in such wounds. Isolated case reports, however, document tetanus as an occasional complication of pit viper bites!8,19. RECOMMENDAnONS
Definitive treatment of pit viper envenomation should include administration of antivenin and/or early debridement of the bite wound when these modalities are available and when indications for their use exist. Snakebite victims, like other patients with contaminated puncture wounds, should receive tetanus prophylaxis. Controlled trials documenting the efficacy of prophylactic antibiotics in decreasing the infectious complications of snakebite injuries are needed. In the meantime, broad spectrum prophylactic antibiotics should continue to be utilized. Treatment of established infection secondary to pit viper envenomation should include aggressive surgical drainage and debridement of devitalized tissue as well as administration of appropriate antibiotics. In cases manifesting muscle necrosis, consideration should be given to use of hyperbaric oxygen 10. Choice of antibiotics for prophylaxis or for
treatment of established infection should reflect knowledge of the oral flora of venomous snakes known to inhabit the local environment. If such information is unavailable, clinicians treating victims of pit viper envenomation should choose antibiotics which are known to be effective against aerobic coliform organisms as well as anaerobic bacteria, particularly histotoxic clostridia. An effective and relatively inexpensive regimen available in most developing nations would include an amino glycoside such as gentamicin in combination with chloramphenicol.
REFERENCES
1 Campbell JA, Lamar WS. The venomous reptiles of Latin America. Ithaca, New York: Cornell University Press, 1989; 69-72 2 Kerrigan KR. Venomous snakebite in eastern Ecuador. Am J Trop Med Hyg 1991;44:93-9 3 Glass TG. Early debridement in pit viper bites. JAMA 1976;235:2513-16 4 Huang IT, Blackwell SJ, Lewis SR. Hand deformities in patients with snakebite. Plast Reconstr Surg 1978;62:32-6 5 Grace TG, Orner GE. The management of upper extremity pit viper wounds. J Hand Surg 1980;5: 168-77 6 Swaroop S, Grab B. Snakebite mortality in the world. Bull WHO 1954;10:35-76 7 Larrick JW, Yost JA, Kaplan 1. Snake bite among the Waorani Indians of Eastern Ecuador. Trans R Soc Trop Med Hyg 1978;72:542-3 8 Pugh RN, Theakston RDG. The incidence and mortality of snake bite in savanna Nigeria. Lancet 1980;ii:1181-3 9 MacGowan WAL. Surgical manpower worldwide. Bull ACS 1987;72:5-9 10 Russell FE. Clinical aspects of snake venom poisoning in North America. Toxicon 1969;7:33-7 11 Garfin SR, Mubarak SJ, Davidson TM. Rattlesnake bites: current concepts. Clin Ortho 1979;140:50-7 12 Reid HA, Theakston RDG. The management of snakebite. Bull WHO 1983;61:885-95 13 Abramowicz M. Treatment of snakebite in the USA. The Medical Letter 1982;24:89 14 Goldstein EJC, Citron DM, Gonzalez H, Russell FE, Finegold SM. Bacteriology of rattlesnake venom and implications for therapy. J Infect Dis 1979;140:818-21 15 Ledbetter EO, Kutscher AE. The aerobic and anaerobic flora of rattlesnake fangs and venom. Arch Environ Health 1969;19:770-8 16 Parrish MD, MacLaurin AW, Tuttle RL. North American pit vipers: bacterial flora of the mouths and venom glands. Viriginia Med Monthly 1956;83:383-5 17 Williams FE, Freeman M, Kennedy E. The bacterial flora of the mouths of Australian venomous snakes in captivity. Med J Aust 1934;21:190-3 18 Evans GH, Farrell JJ. Snake bite treatment and complications. J Florida Med Assoc 1962;48:885-90 19 Parrish HM. Pitfalls in treating pit viper bites. Med Times 1967;95:809-15
Downloaded from tdo.sagepub.com at UNIV OF MICHIGAN on May 19, 2015
158
Bacteriology of snakebite abscess Kevin R Kerrigan MD FACS Hospital Vozandes Oriente Shell, Pastaza, Ecuador TROPICAL DOCTOR,
1992, 22, 158-160
SUMMARY
Thirty-eight cases of abscess secondary to pit viper envenomation are reviewed. The incidence of abscess formation was 9070. Results of aerobic cultures revealed growth of enteric, coliform organisms in 22 of 25 isolates obtained from previously unopened abscesses. Clinical evidence for co-existent anaerobic infection is presented. No cases of tetanus were encountered. Clinical and laboratory findings of patients in the study are correlated with a review of bacteriologic investigations of the oral flora of venomous snakes. Use of antibiotics effective against aerobic coliforms and histotoxic anaerobic organisms for prophylaxis and/or treatment of infectious complications of pit viper envenomation are recommended. INTRODUCTION
Venomous snakebite is a major cause of morbidity and mortality in many parts of the world. In the western hemisphere, most snakebite injuries are caused by members of the family Viperidae, subfamily Crotalidae, also known as pit vipers. In North America, pit vipers are represented by the genera Crotalus (rattlesnakes), Agkistrodan (moccasins) and Sistrurus (massasaugas and pygmy rattlers). In Ecuador, Crotalidae is represented by the genera Bothrops and Lachesis', Abscess formation at the site of envenomation is one of the most frequent and devastating complications of pit viper injuries", Current efforts to prevent infectious complications of pit viper bites include early debridement at the site of envenomation and use of prophylactic antibiotics. Early debridement of pit viper bites has been shown to decrease morbidity associated with local necrosis and/or infectionv". Unfortunately, adequate medical facilities and personnel needed to provide such treatment are often lacking in rural Correspondence to: Dr K R Kerrigan, Kijabe Medical Centre, PO Box 20, Kijabe, Kenya, East Africa.
areas of developing nations where the incidence of snakebite injuries is the highestv". The efficacy of administration of prophylactic antibiotics in reducing incidence or severity of infectious complications of snakebite injuries has never been documented. Much controversy persists with regards to the indications for and usage of prophylactic antibiotics in snakebite injuries!O-13. Once abscess formation occurs, adequate treatment requires prompt surgical drainage combined with administration of appropriate antibiotics. Choice of antibiotics for prophylaxis and/or treatment of established infection secondary to pit viper envenomation demands a knowledge of the responsible organisms. The current study reports the results of aerobic bacteriological cultures and antibiotic sensitivities of abscesses secondary to bites of the Ecuadorian pit vipers, Bothrops and Lachesis. All abscesses occurred amongst a group of 312 snakebite victims admitted to a single medical facility located in the Amazon rainforest of eastern Ecuador. METHODS
The admission records of Hospital Vozandes Oriente for the years 1980 to 1989 were screened and all patients with an admitting diagnosis of snakebite were reviewed. Of the 312 patients thus selected, 38 patients were found to have formed abscesses at the site of envenomation. RESULTS
Incidence Of the 312 patients presenting with a diagnosis of snakebite, 18 arrived later than 4 days post-bite (group 1). These patients presented for treatment of an established complication of the bite rather than for acute treatment of the bite itself. Twelve of these patients had abscesses at the time of admission. The remaining 294 patients arrived within 4 days of the bite and presented for treatment of the snakebite, per se (group 2). Delays in arrival were primarily related to transportation problems. Among this group, 26 abscesses occurred, an incidence of 9%. No case of tetanus was encountered. Epidemiological features of this group have previously been reported elsewhere-. BACTERIOLOGY
Aerobic cultures of abscess contents were obtained in 29 of the 38 cases. Facilities for anaerobic culture were not available and Gram stains of purulent
Downloaded from tdo.sagepub.com at UNIV OF MICHIGAN on May 19, 2015
Tropical Doctor, October 1992
159
material were not obtained. Three of the cultures ANTIBIOTIC SENSITIVITIES obtained resulted in no bacterial growth, despite Susceptibility studies utilizing commercially available the finding of pus at the time of surgical sensitivity discs were performed on the bacterial isolates. Twenty of twenty-three isolates (87010) drainage. Of the 26 cases in which cultures demonstrated demonstrated susceptibility to chloramphenicol. bacterial growth, 23 were obtained at the time of Twenty of 26 isolates (77%) were found to be surgical drainage of previously unopened abscesses. susceptible to gentamicin. Excluding the isolates of Two of these cultures resulted in growth of more Staphylococcus aureus obtained from surface than one organism. The remaining three positive cultures of previously opened abscesses yields cultures were obtained from the surface of wounds susceptibility rates of 90% and 83% respectively. resulting from prior spontaneous drainage of Only five of 25 isolates (20%) were susceptible to abscess cavities. All surface cultures resulted in ampicillin and none of the six isolates tested was growth of Staphylococcus aureus. Of the 25 found to be susceptible to penicillin. surgicallyobtained isolates of previously undisturbed abscesses, one resulted in growth of a J3-haemolytic DISCUSSION streptococcus. Another specimen resulted in growth Venomous snakebite injuries represent contaminated of two isolates, a Gram positive bacillus and puncture wounds. The local effects of injected a Gram positive coccus, neither of which could be venom include haemorrhage and tissue destruction further identified with the laboratory facilities resulting in an ideal environment for bacterial available. The remaining 22 isolates demonstrated growth. Although tissue necrosis without infection growth of a variety of Gram negative rods ('dry gangrene') does occur, more commonly infection supervenes-. (Table I). The finding in the current study of Gram negative Although facilities to perform anaerobic cultures were not available during the time of this study, rods in the vast majority of the aerobic cultures there was a strong clinical suspicion of anaerobic supports the concept that the source of the bacterial involvement in the majority of cases. Foul-smelling inoculum in snakebite abscesses is the oral flora of pus was found at the time of surgical drainage in the offending snake. Furthermore, the mouth all cases of previously unopened abscesses. organisms found in these snakes reflects the fecal Subcutaneous emphysema was found preoperatively flora of their ingested preyr'. Laboratory investigaand/or gas bubbles encountered operatively in tions of the bacteriology of venom and oral cavities infected tissues of many cases. In a number of cases, of North American pit vipers has demonstrated a a progressive, necrotizing myositis occurred despite preponderance of enteric and coliform organisms early and apparently adequate surgical drainage and in aerobic isolates, with Aerobacter, Proteus and administration of appropriate antibiotics. Figure I Pseudomonas occurring most commonlyI4-16. Although the finding of gas formation in tissues shows the leg of a Waorani Indian man who developed crepitus in the bitten extremity 5 days of patients in this series is not diagnostic of anaerobic post-bite. Immediate drainage and administration of gentamicin and chloramphenicol failed to prevent necrotizing myositis of the tibialis anterior and the extensors digitorum longus and hallucis longus muscles. Table 1. Aerobic bacterial isolates from 26 cases of snakebite abscess Gram negative rods" Enterobacter E. coli Serratia Proteus Total ·not further identified
9 5 4 3
Beta strep Gram positive rods" Gram positive cocci"
I
Staphylococcus aureus
3
Total
6
22
Figure 1. The leg of a Waorani Indian man who developed crepitus in the bitten extremity 5 days post bite
Downloaded from tdo.sagepub.com at UNIV OF MICHIGAN on May 19, 2015
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160
infection, the clinical suspicion of co-existent infection with anaerobic organisms which are gasproducing and tissue destructive is also consistent with results of laboratory investigations. Goldstein et 01. 14 found Clostridium to be the most common anaerobic genus isolated from the oral flora of 15 rattlesnakes. Ledbetter and Kutscher'>, in studying 100 rattlesnakes, isolated Clostridia from 48070 of venom and 86070 of fang specimens. Histotoxic species capable of producing gas gangrene were found in half the snakes. The authors felt that 'the potentially histotoxic clostridia are so commonly present in the venom and oropharynx of rattlesnakes that all bites with extensive necrosis should be treated with antibiotics effective against clostridia' 15. Bacteriologic studies of the oral flora of snakes other than North American pit vipers yield similar results. Williams et 01. 17 isolated coliform bacilli from the mouths of 73% of a variety of Australian snakes. Clostridia were recovered from the mouths of all of the 49 snakes they studied!". There are no reports of laboratory investigation of the bacteriology of snakes' mouths which document isolation of Clostridium tetani. The present report confirms the low incidence of tetanus in such wounds. Isolated case reports, however, document tetanus as an occasional complication of pit viper bites!8,19. RECOMMENDAnONS
Definitive treatment of pit viper envenomation should include administration of antivenin and/or early debridement of the bite wound when these modalities are available and when indications for their use exist. Snakebite victims, like other patients with contaminated puncture wounds, should receive tetanus prophylaxis. Controlled trials documenting the efficacy of prophylactic antibiotics in decreasing the infectious complications of snakebite injuries are needed. In the meantime, broad spectrum prophylactic antibiotics should continue to be utilized. Treatment of established infection secondary to pit viper envenomation should include aggressive surgical drainage and debridement of devitalized tissue as well as administration of appropriate antibiotics. In cases manifesting muscle necrosis, consideration should be given to use of hyperbaric oxygen 10. Choice of antibiotics for prophylaxis or for
treatment of established infection should reflect knowledge of the oral flora of venomous snakes known to inhabit the local environment. If such information is unavailable, clinicians treating victims of pit viper envenomation should choose antibiotics which are known to be effective against aerobic coliform organisms as well as anaerobic bacteria, particularly histotoxic clostridia. An effective and relatively inexpensive regimen available in most developing nations would include an amino glycoside such as gentamicin in combination with chloramphenicol.
REFERENCES
1 Campbell JA, Lamar WS. The venomous reptiles of Latin America. Ithaca, New York: Cornell University Press, 1989; 69-72 2 Kerrigan KR. Venomous snakebite in eastern Ecuador. Am J Trop Med Hyg 1991;44:93-9 3 Glass TG. Early debridement in pit viper bites. JAMA 1976;235:2513-16 4 Huang IT, Blackwell SJ, Lewis SR. Hand deformities in patients with snakebite. Plast Reconstr Surg 1978;62:32-6 5 Grace TG, Orner GE. The management of upper extremity pit viper wounds. J Hand Surg 1980;5: 168-77 6 Swaroop S, Grab B. Snakebite mortality in the world. Bull WHO 1954;10:35-76 7 Larrick JW, Yost JA, Kaplan 1. Snake bite among the Waorani Indians of Eastern Ecuador. Trans R Soc Trop Med Hyg 1978;72:542-3 8 Pugh RN, Theakston RDG. The incidence and mortality of snake bite in savanna Nigeria. Lancet 1980;ii:1181-3 9 MacGowan WAL. Surgical manpower worldwide. Bull ACS 1987;72:5-9 10 Russell FE. Clinical aspects of snake venom poisoning in North America. Toxicon 1969;7:33-7 11 Garfin SR, Mubarak SJ, Davidson TM. Rattlesnake bites: current concepts. Clin Ortho 1979;140:50-7 12 Reid HA, Theakston RDG. The management of snakebite. Bull WHO 1983;61:885-95 13 Abramowicz M. Treatment of snakebite in the USA. The Medical Letter 1982;24:89 14 Goldstein EJC, Citron DM, Gonzalez H, Russell FE, Finegold SM. Bacteriology of rattlesnake venom and implications for therapy. J Infect Dis 1979;140:818-21 15 Ledbetter EO, Kutscher AE. The aerobic and anaerobic flora of rattlesnake fangs and venom. Arch Environ Health 1969;19:770-8 16 Parrish MD, MacLaurin AW, Tuttle RL. North American pit vipers: bacterial flora of the mouths and venom glands. Viriginia Med Monthly 1956;83:383-5 17 Williams FE, Freeman M, Kennedy E. The bacterial flora of the mouths of Australian venomous snakes in captivity. Med J Aust 1934;21:190-3 18 Evans GH, Farrell JJ. Snake bite treatment and complications. J Florida Med Assoc 1962;48:885-90 19 Parrish HM. Pitfalls in treating pit viper bites. Med Times 1967;95:809-15
Downloaded from tdo.sagepub.com at UNIV OF MICHIGAN on May 19, 2015
