The occurrence of Aeromonas hydrophila wound infections in healthy hosts after water-associated injury is being reported more frequently. This paper reports our experience with 3 such cases and outlines the importance of recognising the association between a water-related injury and, this organism

Hide, G.R.

Moore, P.J.

Sacho, H

English

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SAMJ VOL 78 15 SEPT 1990 339Aquatically acquired Aeromonas hydrophilawound infectionA report of 3 casesH. SACHO, P. J. MOORE, G. R. HIDESummaryThe occurrence of Aeromonas hydrophila wound infectionsin healthy hosts after water-associated injury is being reportedmore frequently. This paper reports our experience with 3such cases and outlines the importance of recognising theassociation between a water-related injury and, this organism.S AIr Med J 1990: 78: 339-340.The occurrence of Aeromonas hydrophila wound infections inhealthy hosts after water-associated injury was first emphasisedin 2 cases of mixed infection associated with swimming acci-dents. l Recently focal Aeromonas infections have been reportedwith increasing frequency. 2,3Case reportsCase 1A 49-year-old man was admitted to Johannesburg Hospitalafter having sustained a laceration on the sole of the left footwhile paddling in a river 2 days eatlier. The injury hadbecome progressively more painful and swollen. On admissionhe had a temperature of 38,5°C and the left foot was swollen,erythematous and tender with an obviously infected 10 mmlaceration over the left 5th metatarsal. A small quantity of puscould be expressed from the wound and the ipsilateral lymphnodes were tender and enlarged. Radiographs of the foot didnot -reveal any foreign bodies and the results of laboratoryinvestigations were normal apart from a white cell count of17,6 X 10911.In addition to tetanus toxoid the patient was given intra-venous penicillin, amikacin and metronidazole pending themicrobiological results of a pus swab of the wound taken onadmission. While his pyrexia settled over the next 3 days, thelocal inflammation and cellulitis worsened, necessitating opera-tive debridement. At operation no abnormalities other thandeep-seated plantar fat pad necrosis were found.Bacteriological cultures revealed a profuse growth of A.hydrophila and the antibiotic regimen was changed to cefta-zidime and amikacin.Department of Experimental and' Clinical Pharmacology,University of the Witwatersrand, JohannesburgH. SACHO, M.B. B.CH.,B.Se., F.F.PATH. (S.A.)P. J. MOORE, M.B. B.CH., DIP. MID. C.O.G. (S.A.), F.C.O.G. (s.A.), M.R.C.O.G.,HONS. B.Se. GENEESK. WET. (STILL.)Department of Surgery, Johannesburg Hospital and Uni-versity of the Witwatersrand, JohannesburgG. R. HIDE, M.B. B.CH.Accepted 26 Apr 1990.Postoperatively the wound healed satisfactorily and he wasdischarged without further complications.Case 2A 35-year-old woman was admitted to Johannesburg Hospitalafter having been bitten by a crocodile while swimming in ariver in Botswana. She had sustained injuries to both buttocksand the right thigh. On examination, although pale, she washaemodynamically stable and her temperature was 37,5°C.There was extensive loss of skin and muscle of both buttocksand the lateral aspect of the right thigh. The anus had been,spared and the sphincter was functional. The clinical suspicionof a stable pelvic fracture was confirmed radiologically' andcystography and ureilirography showed the lower urinary tractto be intact. The haemoglobin concentration was 6,9 gldl andthe white cell count was 11,4 X 109/1.After blood transfusion and tetanus toxoid administration,the patient underwent operative debridement and treatmentwith'a triple antibiotic regimen consisting of penicillin, amikacinand metronidazole was started. Blood cultures revealed thepresence of A. hydrophila and an operative specimen ofdebrided tissue showed a profuse growth of A. hydrophila aswell as a moderate growth of anaerobic organisms and Pseudo-monas aeruginosa. In view of these results and the patient'sclinical septicaemia the antibiotic regimen was changed toceftazidime and amikacin. A repeat debridement was performed2 days later and the fashioning of skin flaps for subsequentdefect closure was commenced. Over the next 3 days herpyrexia settled and she showed marked clinical improvement.Defmitive closure of the tissue defects by a skin flap combinedwith split-skin grafting was undertaken on the 8th day afterthe injury with a successful result.Case 3A 31-year-old man sustained a crush injury to the right legin a power boat accident on a dam in Botswana. He wasevacuated by air to Johannesburg Hospital, where he wasfound to be haemodynamically stable. He had a temperatureof 38,0°C and a large 150 X 150 mm stellate laceration'on theposterior aspect of the right calf with extensive loss of skin andmuscle.Radiological and Doppler studies confirmed that there wasno bone or vascular injury and clinically no neurologicaldeficit was found. Besides a white cell count of 12,6 X 109/1the results of laboratory investigations were normal.Tetanus toxoid was administered, treatment with antibioticsin the form of penicillin, amikacin an!! metronidazole com-menced and operative debridement was performed. On the 4thday microbiological examination of an operative tissue specimenrevealed the presence of a profuse growth of A. hydrophila. Inview of his clinical toxicity and these results, the antibioticswere changed to ceftazidime and amikacin. The patient'spyrexia rapidly settled thereafter and on day 8 he was trans-ferred to Windhoek for subsequent skin grafting.340 SAMJ VOL 78 15 SEPT 1990DiscussionThe genus Aeromonas has frequently been isolated from watersources, marine animals and soil. A. hydrophila was culturedfrom human sources as early as 19374 and is being recognisedincreasingly in human/ocal and systemic infections.2After gastro-intestinal infections manifesting as diarrhoeas,skin and soft-tissue infections are the second most commonsite for A. hydrophila isolation. Most of these infections aredirectly related to water- or soil-associated injury,I,2,5-7 withthe lower extremity being involved in 75% of cases.8 Thecondition is characterised by a rapid onset of cellulitis andpurulent discharge, which remains localised in healthy hosts.Dissemination from localised wound infections has beenobserved in compromised hosts.5Aeromonas species are particularly pathogenic for muscle9-11and cause intense local muscle inflanimation and necrosis.2,5,6,7,12The necrotising myositis appears to be a metastatic localisationof haematogenous infection with the organism.Aeromonas species comprise a group of non-fastidious,fermentative Gram-negative bacilli, excluded from the familyof Enterobacteriaceae primarily because they produce cyto-chrome oxidase. Aeromonas species share some characteristicswith Vibrio and Pleisiomonas species. The genus Aeromonascurrently includes 3 motile species (A. caviae, A. hydrophila,and A. sobria) and 1 non-motile species (A. salmonicida). Onlythe motile species ar-e considered potential human pathogens.As the species name hydrophila ('water lover') indicates,- thenatural habitat of Aeromonas species is fresh or sea waters,where they commonly cause infectious disease in cold-bloodedaquatic animals. These bacteria also reside in sink traps anddrainpipes and can be recovered from tap-water faucets anddistilled water supplies, which are potential sources oforganisms involved in nosocomial infections.On blood agar, many strains. of Aeromonas species show alarge zone of ,B-haemolysis, but non-haemolytic strains dooccur. On enteric differential agars the majority of strains arenon-lactose-fermenting, although a minority of strains yieldlactose-fermenting colonies. However, enteric media arefrequently inhibitory for Aeromonas species. In the routinediagnostic laboratory, the most important characteristics thatshould lead to a presumptive diagnosis of infection· withAeromonas species are growth on MacConkey agar, a positiveoxidase reaction, and fermentation of carbohydrates. Theoxidase test in aeromonads is positive if perfomed with thereagent on colonies from blood agar, but may be negative ifperformed on colonies from enteric agars. On triple-sugar ironagar or Kligler iron agar, most strains yield acid buns andslants - however, alkaline slants, gas formation or both mayoccur, but not H2S formation. If oxidation-fermentation mediawith carbohydrates are used, acidification occurs in both 'open'and 'closed' mbes. 13,14 In conjunction with traditional or com-mercial kit systems, the abovementioned tests should lead to acorrect bacteriological diagnosis.The majority of isolates of Aeromonas species are susceptiblein vitro to chloramphenicol, tetracyclines, co-trirnoxazole, andthe newer aminoglycosides and cephalosporins. Most penicil-lins, the fIrst-generation cephalosporins and older aminoglyco-sides (e.g. streptomycin and kanamycin) are ineffective fortreating Aeromonas infections. The organism is variably suscep-tible to erythromycin and piperacillin, and their use remainscontroversial.6 As early as 1966, Bulger and Sherris9 foundthat A. hydrophila appeared to elaborate a ,B-lacramase enzyme.This rmding was later confIrmed when it was found that theorganism produces a chromosomally mediated ,B-lacramaseenzyme (termed AER-l), which hydrolyses both penicillinsand fIrst-generation cephaloSporins.15This explains the minimalactivity of the fIrst-generation cephalosporins and of ampicillinagainst this organism. Published data now indicate that co-trimoxazole is effective for the treatment of the majority ofAeromonas infections,16 but that a combination of .amino-glycoside (e.g. gentamicin or amikacin) togetlier with anextended-spectrum cephalosporin (e.g. ceftazidime or cefo-taxime) is preferred for bacteraemia or severe sepsis.8ConclusionThese cases illustrate the importance of considering A. hydro-phila among the causes of post-traumatic infeCtion, especiallywhen trauma has been associated with a fresh-water environ-ment or marine animals. Our antibiotic recommendations areto use a third-generation cephalosporin such as ceftazidimetogether with an aminoglycoside such as amikacin as empiricaltherapy in patients who present with a soft-tissue water-related injury, especially if there is evidence of severe inflam-mation.REFERENCES1. Washington JA. Aeromonas hydr<>J>hiJa in clinical bacteriologic specimens.Ann Intern Med 1972; 76: 611-614. '2. Von Graevenitz A, Mensch AH. The genus Aeromonas in human bac-teriology. N Engl] Med 1968; 278: 245-249. .3. Cooper RG, Brown GW. Plesiomonas shigelloides in South Australia.] ClinP<uJwII968; 21: 715-718.4. Miles AA, Halnan ET. A new species of microorganism (Noreris melana-vogenes) causing black rot in eggs.] Hyg (Land) 1937; 37: 79-97.5. McCracken AW, BarkIey R. Isolation of Aeromonas species from clinicalsources.] Clin ParJwI1972; 25: 970-975.6. Phillips JA, Bernhardt HE, Rosenthal SG. Aeromonas hydr<>J>hila infections.Pediatrics 1974; 53: 110-112.7. Rosenthal SG, Bernhardt HE, Phillips JA. Aeromonas hydr<>J>hila woundinfection. Plasr Reconsrr Surg 1974; 53: 77-79.8. Khardori N, Fainstein V. Aeromonas and Plesiomonas as aetiological agents.Annu Rev MicrobioI1988;~ 395-419.9. Bulger R, Sherris J. The clinical significance of Aeromonas hydr<>J>hila.. ArchInrern Med 1966; 118: 562-564. .10. Ketover BP, Young LS, Armstrong D. Septicaemia due to Aeromonashydrophila: clinical and immunological aspectS. ] Infecr DU 1973; 127:284-290.11. Shilkin KB, Annear DI, Rowen LR, Lavrence BH. Infection due toAeromonas hydr<>J>hiJa. Med] Ausr 1968; I: 351-353.12. Stephen S, Rao KNA, Kumar MS, Indurani R. Human infection withAeromonas species: varied clinical manifestations. Ann Intern Med 1975; 83:368-369.13. Koneman EW, Allen SD, Powell VR jun er al. Color Atlas and Texrbook ofDiagrwsriJ: Microbiology. 3rd ed. Philadelphia: JB Lippincon, 1988: 215-218.14. Le.nnet:e EH, Balows A, Hausler WJ jun, Shadomy HJ. Manual of ClinicalMzcrobiology. 4th ed. Washington, DC: American Sociery for Microbiology,1985: 278-281.16. Kucers A, Bennen NMcK. The Use ofAnribiorics. 4th ed. London: WilliamHeinemann Medical Books, 1987: 1162. -15. Bush K. Oassification of ,B-lactam.ases: groups 2c, 2d, 2e, 3 and 4. AnrimicrobAgenrs Chemorher 1989; 33: 271-276.

Aquatically acquired Aeromonas hydrophila wound infection A report of 3 cases

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Aquatically acquired Aeromonas hydrophila wound infection A report of 3 cases

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