Clinical and Microbiological Features of Shewanella Bacteremia in Patients with Hepatobiliary Disease

□ ORIGINAL ARTICLE □

Po-Yu Liu 1,2, Chin-Fu Lin 3,4, Kwong-Chung Tung 2, Ching-Lin Shyu 2, Ming-Ju Wu 1, Jai-Wen Liu 5, Chi-Sen Chang 1, Kun-Wei Chan 6, Jin-An Huang 7 and Zhi-Yuan Shi 1,8

Abstract

Objective Shewanella bacteremia is an uncommon but potentially fatal disease. Although hepatobiliary diseases have been proposed to be risk factors for various Shewanella infections, little is known about the features of Shewanella bacteremia in patients with hepatobiliary diseases. This study aims to characterize the presentation and risk factors of Shewanella bacteremia in patients with hepatobiliary diseases. Methods We retrospectively investigated the clinical features, microbiology and outcomes of patients with Shewanella bacteremia who were admitted to a tertiary medical center between January 2001 and December 2010. All isolates were confirmed to the species level using 16S rRNA sequencing analyses. The English language medical literature was searched for previously published reports. Results Fifty-nine cases of Shewanella bacteremia, including nine at the hospital, were identified, 28 (47.4%) of which involved underlying hepatobiliary diseases, representing an important risk factor. In 12 of the 28 cases, the infections involved the hepatobiliary system; with a tendency towards an Asian origin. In our case series of nine patients, Shewanella haliotis was isolated in five patients. The majority of our patients lived in coastal areas, consumed seafood regularly and developed bacteremia during the summer season. Conclusion It is recommended that the possibility for Shewanella infection be considered in patients with bacteremia and also underlying hepatobiliary diseases, particularly if patients present with hepatobiliary infections, a history of seafood, or development of the disease during the summer.

Key words: bacteremia, cholangitis, biliary tract diseases, liver cirrhosis, seafood, Shewanella

(Intern Med 52: 431-438, 2013) (DOI: 10.2169/internalmedicine.52.8152)

critical care and antimicrobial therapy, rapid fatal cases are Introduction still reported (3). The genus Shewanella includes 59 recognized species at Shewanella is a non-fermentative Gram-negative bacilli the time of this writing (http://www.bacterio.cict.fr/s/ found in aquatic environments throughout the world. Bac- shewanella.html). Most reported human infections are teremia caused by Shewanella is an uncommon but poten- caused by Shewanella algae and Shewanella putrefaciens. tially fatal disease. The mortality rate of Shewanella bactere- However, it is often difficult to identify the microbes at the mia is 28% (1). However, the mortality may rise to more species level using conventional microbiologic culture and than 50% in patients with underlying hepatobiliary dis- biochemical analyses. In addition, many automated identifi- eases (2). Moreover, despite the administration of aggressive cation systems include only S. putrefaciens in their database.

１Department of Internal Medicine, Taichung Veterans General Hospital, Taiwan, ２Department of Veterinary Medicine, College of Veterinary Medicine, National Chung-Hsing University, Taiwan, ３Microbiology Section of the Medical Laboratory Department, Taichung Veterans General Hospital, Taiwan, ４Department of Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taiwan, ５De- partment of Emergency Medicine, Chung Shan Medical University Hospital, Taiwan, ６Department of Veterinary Medicine, National Chiayi Uni- versity, Chiayi, Taiwan, School of Medicine, Chung-Shan Medical University, Taiwan, ７Department of Emergency Medicine, Taichung Veterans General Hospital, Taiwan and ８National Yang-Ming University, Taiwan Received for publication May 15, 2012; Accepted for publication November 7, 2012 Correspondence to Dr. Zhi-Yuan Shi, [email protected]

431 Intern Med 52: 431-438, 2013 DOI: 10.2169/internalmedicine.52.8152

DNA sequencing provides an opportunity for definitive tion using the Basic Local Alignment Search Tool (BLAST) identification (4). By incorporating 16S rRNA gene se- algorithm. The closest matches and GenBank accession quencing into the identification of Shewanella, more She- numbers were obtained. wanella species can be recognized as pathogenic organ- The minimum inhibitory concentrations (MICs) for am- isms (5-7). picillin/sulbactam, piperacillin, piperacillin/tazobactam, cefa- Shewanella is primarily an opportunistic pathogen that zolin, cefoxitin, ceftazidime, ceftriaxone, cefepime, causes three patterns of infection: soft tissue infection, bac- ciprofloxacin, imipenem, gentamicin, and trimethoprim- teremia and neonatal sepsis (3). In the majority of cases, the sulfamethoxazole were determined using the VITEK II auto- organism is cultured from and related to soft tissue infec- mated system (bioMérieux, France). Next, the disk-diffusion tions, primarily in patients with associated underlying ill- method was used as a confirmatory tool. There are no rec- nesses. Sea water exposure is a common environmental fac- ognized Clinical and Laboratory Standards Institute (CLSI) tor linked with soft tissue infections. Recently, the number MIC interpretive standards specified for this bacterial genus, of case reports of severe Shewanella bacteremia has in- and the MIC breakpoints of cefazolin, cefoxitin and ampicil- creased. Many of these patients were reported to have un- lin/sulbactam for non-fermentative Gram-negative bacilli are derlying hepatobiliary diseases and were from Asian re- also lacking in the CLSI database. In the present report, the gions (3, 8, 9). Previous analyses also suggest that hepato- MIC breakpoints of piperacillin (susceptible, !16 μg/mL; in- biliary diseases are a risk factor for the development of vari- termediate, 32-64 μg/mL; resistant, "128 μg/mL), piperacil- ous Shewanella infections; however, little is known about lin/tazobactam (susceptible, !16/4 μg/mL; intermediate, 32/ the roles of predisposing factors in bacteremia. The predis- 4-64/4 μg/mL; resistant, "128/4 μg/mL), ceftazidime (sus- posing factors, clinical presentation, treatments and out- ceptible, !8 μg/mL; intermediate, 16 μg/mL; resistant, "32 comes of Shewanella infection are poorly characterized. μg/mL), ceftriaxone (susceptible, !8 μg/mL; intermediate, We therefore conducted a 10-year retrospective study to 16-32 μg/mL; resistant, !64 μg/mL), cefepime (susceptible, review cases of Shewanella bacteremia occurring at our in- !8 μg/mL; intermediate, 16 μg/mL; resistant, "32 μg/mL), stitution. The aim of this study was to investigate the clini- ciprofloxacin (susceptible, !1 μg/mL; intermediate, 2 μg/mL; cal and microbiologic characteristics of Shewanella bactere- resistant, "4 μg/mL), imipenem (susceptible, !4 μg/mL; in- mia, especially in patients with hepatobiliary diseases. All termediate, 8 μg/mL; resistant, "16 μg/mL), gentamicin (sus- isolates were confirmed to the species level using 16S rRNA ceptible, !4 μg/mL; intermediate, 8 μg/mL; resistant, "16 sequencing analyses. The susceptibility of the Shewanella μg/mL) and trimethoprim-sulfamethoxazole (susceptible, !2/ isolates to various antibiotics was determined. In this report, 38 μg/mL; resistant, "4/76 μg/mL) were interpreted using we also review similar cases reported elsewhere in order to CLSI approved standard M100-S22 categories for other non- summarize the important features of this disease. Enterobacteriaceae in accordance with previous reports (7, 9, 14). In addition, the standards recommended by Materials and Methods the U.S. Food and Drug Administration (FDA) for ampicillin/sulbactam (susceptible, !8 μg/mL; intermediate, 16 μg/ This retrospective study was conducted at Taichung Veter- mL; resistant, "32 μg/mL), cefazolin (susceptible, !16 μg/ ans General Hospital, a tertiary medical center in central mL; resistant, "64 μg/mL) and cefoxitin (susceptible, !8μg/ Taiwan. All patients included were diagnosed with Shewan- mL; intermediate, 16 μg/mL; resistant, "32 μg/mL) were ella bacteremia between January 2001 and December 2010. used. The patients were identified using the computerized database Previously published cases of Shewanella bacteremia in of the institution. Clinical, laboratory and microbiologic data adults were reviewed. The English language medical litera- were retrieved from the medical records of the patients. A ture was searched using the online bibliographic database of standardized case record form was used by two experienced the National Library of Medicine (MEDLINE, PubMed). physicians to record the demographic profile, underlying The search terms included “Pseudomonas putrefaciens,” condition, clinical presentation, therapy and outcome of each “Shewanella,” “Shewanella putrefaciens,” “Shewanella patient. alga,” “Shewanella algae,” “bacteremia” and “bloodstream All isolates from patients with Shewanella bacteremia infection.” All studies identified were reviewed, as were the were re-identified using Gram staining, colony morphology references cited in the articles found in the original search. and biochemical characteristics (10). The organisms were Fisher’s exact test was used to compare categorical vari- further confirmed with 16S rRNA gene sequence analy- ables. Continuous variables were compared using the Wil- sis (11-13). The primers used for amplification of the 16S coxon rank-sum test, as appropriate. p<0.05 was considered rRNA gene were B27F (5’-AGAGTTTGATCCTGGCTCAG- statistically significant. All statistical analyses were per- 3’) and U1492R (5’-GGTTACCTTGTTACGACTT-3’). The formed using the SPSS, version 15.0 software program amplification products obtained with polymerase chain reac- (SPSS, Chicago, IL). tion (PCR) were sequenced, and the sequences were compared to known 16S rRNA gene sequences in the GenBank database of the National Center for Biotechnology Informa-

432 Intern Med 52: 431-438, 2013 DOI: 10.2169/internalmedicine.52.8152

Table 1. Characteristics of Patients with Shewanella Bacteremia, January 2001 Through December 2010

Living Other Underlying in organisms hepatobiliary coastal isolated from Antibiotic therapy for Patient Age/Sex Clinical syndrome condition area Shewanella species (GenBank ID) blood Shewanella infection Outcome Ampullary 1 80/M Cholangitis carcinoma Y S. haliotis (HM016086) E.coli flomocef Survival 2 91/M Cholangitis Cholangiocarcinoma Y S. haliotis (HM016086) cefmetazole Death E. coli, K. amoxicillin-clavulanic 3 77/M Cholangitis CBD stone, HBV N S. haliotis (FN997626) pneumoniae acid Survival Hepatoma, liver 4 66/M Infected biloma cirrhosis , HBV Y S. haliotis (HM016086) cefpirome Survival 5 81/M Liver abscess Hepatoma Y S. haliotis (FN997635) cefoxitin Survival Liver cirrhosis, amoxicillin-clavulanic 6 55/M Cellulitis HBV Y S. algae (HM016087) acid Survival amoxicillin-clavulanic 7 71/F Bacteremia Lung cancer Y S. algae (HM016087) acid Death 8 68/M Cholecystitis Gall bladder stone N S. algae (GQ372874) ampicillin Survival Hepatoma, liver 9 47/M Bacteremia cirrhosis , HCV,DM N S. putrefaciens (DQ307731) A. baumannii cefmetazole Survival CBD: common bile duct, HBV: hepatitis B virus, HCV: hepatitis C virus

A comparison of the clinical features of patients with S. Results haliotis bacteremia and those with non- S. haliotis bacteremia is shown in Table 2. We did not find any statistically Nine patients with Shewanella bacteremia were identified significant differences in any values between the five cases during the study period (Table 1). The patients included of S. haliotis and the four cases of other Shewanella species, eight men and one woman, with ages ranging from 47 to 91 although more patients in the S. haliotis bacteremia group years (median age: 71 years). Eight of the nine patients had presented with systemic symptoms, such as fever, chills and underlying hepatobiliary diseases, including liver cirrhosis, shock. These patients also had higher WBC counts and he- hepatitis, biliary tract stones or hepatobiliary malignancies. patic dysfunction of greater severity than did the patients Shewanella bacteremia was the initial presentation of hepa- with non- S. haliotis bacteremia. tobiliary malignancy in four of the five patients with cancer, Seven of the nine patients developed Shewanella bactere- including patients with cholangiocarcinoma, ampullary carci- mia between July and September, with a peak number (five noma and hepatoma. Seven patients had splenomegaly at the patients) developing the disease in September. Six of the time of bacteremia onset. Five patients had underlying car- nine patients lived in coastal areas. Two of the other three diovascular lesions, including two patients with aortic dis- patients consumed seafood regularly. Figure shows the mean section, two patients with aortic insufficiency and one pa- sea surface temperature and the number of cases of Shewan- tient with deep vein thrombosis. Five patients had hypo- ella bacteremia. chlorhydria, either because they had previously undergone Concerning antibiotic therapy, most of the patients re- gastrectomy or because they were receiving either proton ceived broad-spectrum β-lactam antibiotics, including pump inhibitors or H2-receptor antagonists. amoxicillin-clavulanate (three patients), cefmetazole (two pa- Shewanella bacteremia was associated with hepatobiliary tients), cefoxitin (one patient), flomoxef (one patient), cefpi- infections in six patients, including patients with cholangitis, rome (one patient) and ampicillin (one patient). Two patients cholecystitis, liver abscesses or infected bilomas. In two pa- died due to severe sepsis. tients, no evident sites of infection were established. The in- The MICs of the clinical isolates of the 12 antimicrobial fected focus was cellulitis in one patient. Most patients did agents are listed in Table 3. All tested Shewanella isolates not undergo any medical procedures before developing bac- were found to be susceptible to piperacillin, piperacillin- teremia; however, in one patient, the bacteremia followed a tazobactam, ceftriaxone, cefepime, ciprofloxacin, imipenem, liver biopsy. No patients were receiving antibiotics or corti- gentamicin and trimethoprim/sulfamethoxazole. Of the tested costeroids at the time of development of bacteremia. isolates, 88.8% were susceptible to ampicillin-sulbactam and In the nine patients, the causative Shewanella species ceftazidime and 66.63% were susceptible to cefoxitin. The were Shewanella haliotis (in five patients [55.5%]), S. algae majority of tested Shewanella isolates were resistant to cefa- (in three patients [33.3%]) and S. putrefaciens (in one pa- zolin (77.7%). tient [11.1%]). The majority of patients had monomicrobial Our search of the Medline database revealed 28 articles bacteremia. Three patients had polymicrobial bacteremia, concerning Shewanella bacteremia in adults. Clinical details and the concomitant pathogens included E. coli (in two pa- were available for 50 cases (1-3, 6, 8, 9, 14-35), 20 (40%) tients), Klebsiella pneumoniae (in one patient), and Acineto- of which involved underlying hepatobiliary diseases (Ta- bacter baumannii (in one patient). ble 4). Of these 20 patients, 15 (75%) were men, and the

433 Intern Med 52: 431-438, 2013 DOI: 10.2169/internalmedicine.52.8152

Table 2. Clinical Features and Initial Laboratory Values for Patients with Bacteremia due to S. haliotis and Non S. haliotis

All (n=9) S. haliotis (n=5) Non S. haliotis (n=4) Demographics Male (%) 8 (88.8%) 5 (100%) 3 (75%) Age, median years (range) 71 (47-91) 77 (66-91) 61.5 (47-71) Clinical features Fever (>38.3ÛC) (%) 6 (66.6%) 4 (80%) 2 (50%) Chills (%) 4 (44.4%) 3 (60%) 1 (25%) Abdominal pain (%) 6 (66.6%) 4 (80%) 2 (50%) Mental status change (%) 1 (11.1%) 0 1 (25%) Shock (%) 4 (44.4%) 3 (60%) 1 (25%) Death (%) 2 (22.2%) 1 (20%) 1 (25%) Splenomegaly (%) 7 (77.7%) 4 (80%) 3 (75%) Vascular lesion (%) 5 (55.5%) 2 (40%) 3 (75%) Hypochlorhydria (%) 5 (55.5%) 4 (80%) 1 (25%) Laboratory findings White cell countsa (per mm3 × 103) 14.4 ±5.7 12.8 ±6.3 9.6±5.1 Hemoglobina (g/dL) 12.8 ±2.1 12.1±2.5 13.6±1.4 Platelet countsa (per mm3 × 104) 15.9 ±10.0 14.3±11.2 18.1±9.5 Alanine aminotransferasea (IU/L) 97.3 ±81.5 110.2±81.5 81.3±90.8 Total bilirubina (mg/dL) 6.7 ±6.0 9.4±6.9 3.4±2.3 Alkaline phosphatasea (IU/L) 345.1±506.8 517.2±655.2 130±39 C-reactive protiena (mg/dL) 10.4 ±8.1 11.0±4.0 9.6 ±13.3 a) mean ± SD

8 35 In total, there were 28 patients with underlying hepato- 7 biliary diseases who developed Shewanella bacteremia. C 6 30 Û Among these patients, eight patients (28%) died, at an aver- 5 age age of 67.7 years. The underlying liver disorder was 4 25 malignancy in five of the eight fatal cases. All fatal cases in-

Case number Case 3 volved sepsis, and four fatal cases involved polymicrobial 2 20 bacteremia. Blood cell counts were available in five of the Sea surface temperature Sea surface 1 eight fatal cases. All of these five patients had peripheral 0 15 blood cytopenias, including neutropenia in three cases, ane- Jan-Mar Apr-Jun Jul-Sep Oct-Dec mia in three cases and thrombocytopenia in five cases. Two Month patients developed concomitant renal failure. Figure. The seasonal distribution of Shewanella bacteremia and the mean sea surface temperature, 2001 to 2010. Bars: Discussion case number. Circle: mean sea surface temperature. The data are expressed as the means, SD. This study reported nine cases of Shewanella bacteremia, including the first reported cases of S. haliotis bacteremia. Together, our data and the literature review show that of 59 median age was 64.5 years (range: 42 to 85 years). Fifteen bacteremic patients, 28 (47.4%) had underlying hepatobili- of the 20 patients were 60 years of age or older. The major- ary diseases, representing an important risk factor. Hepato- ity of patients presented with hepatobiliary infections (six biliary infections were present in a total of 12 (42.8%) of 28 cases, 30%), primary bacteremia (six cases, 30%) and soft patients with underlying hepatobiliary diseases with a ten- tissue infections (five cases, 25%). dency toward an Asian origin. In our case series, six The underlying hepatobiliary diseases included liver cir- (66.6%) of the patients lived in coastal areas and seven rhosis, hepatitis, biliary tract stones and hepatobiliary malig- (77.7%) developed Shewanella bacteremia during the sum- nancies. Sixteen of the 20 patients (80%) lived in Asian re- mer. The Shewanella isolates evaluated in this study were gions, including Japan, Korea, Hong Kong and Taiwan. found to be susceptible to most third- and fourth-generation Ten patients had monomicrobial infections. In cases of cephalosporins and piperacillin/tazobactam and resistant to polymicrobial infection, the co-isolates included E. coli (six cefazolin. cases), Enterococcus species (one case), Klebsiella species Our results indicate that hepatobiliary diseases, reported (two cases), Aeromonas species (two cases), Morganella in 88.8% of the patients in our series, represent an important morganii (one case), Serratia marcescens (one case), Flavo- risk factor in patients with Shewanella bacteremia. These bacterium odoratium (one case), Edwardsiella tarda (one findings are consistent with those of previous Asian stud- case) and Citrobacter diversus (one case). ies (9, 27). In a case series conducted in Hong Kong, 50%

434 Intern Med 52: 431-438, 2013 DOI: 10.2169/internalmedicine.52.8152

Table 3. MICs and Susceptibility Interpretations for Clinical Isolates of Shewanella Species

MI&LQȝJ/mL (susceptibility status) Case Species SAM PIP TAZ/PIPC CEZ CFX CAZ CTRX CFPM CIP IPM GM TMP-SMX 1 S. haliotis (S) 8 (S) (S) (R) (R) I) 8 (S) (S) (S) (S) (S) (S) S. haliotis (S) (S) (S) (R) I) 6 6 (S) (S) (S) (S) (S) 3 S. haliotis (S) (S) (S) (R) 8(S) (S) (S) (S) (S) 6 (S) (S) S. haliotis (S) (S) (S) (R) (S) (S) (S) (S) (S) (S) (S) (S) S. haliotis (R) (S) (S) (R) 5 (S) (S) (S) (S) 6) 6 (S) S. algae (S) (S) (S) (R) (S) (S) (S) (S) (S) 6 (S) (S) 7 S. algae (S) (S) (S) (R) 8(S) (S) (S) (S) (S) 6 (S) (S) 8 S. algae (S) (S) (S) 8 (S) (S) (S) (S) (S) (S) (S) (S) (S) S. putrefaciens (S) (S) (S) 6 (S) (S) (S) (S) 1 (S) (S) (S) (S) I: intermediate, R: resistant, S: susceptible SAM(Ampicillin/Sulbactam), PIP(piperacillin), TAZ/PIPC(piperacillin/tazobactam), CEZ(cefazolin), CFX(cefoxitin), CAZ(ceftazidime), CTRX(ceftriaxone), CFPM(cefepime), CIP(ciprofloxacin), IPM(imipenem), GM(JHQWamicin), TMP-SMX(trimethoprim-sulfamethoxazole)

Table 4. Characteristics of the Studies of Shewanella Bacteremia in Patients with Hepatobiliary Diseases during 1979-2010

Case Year Country Age Sex Underlying condition Presentation Coisolates in blood outcome Ref 1 1979 US 63 M Alcoholic liver cirrhosis, congestive STI Survival 21 heart failure, gouty arthritis 2 1981 Japan 80 M CBD stone Cholangitis E.coli, Enterococcus Survival 17 3 1989 US 50 F Pancreatic carcinoma, liver metastasis Liver abscess Klebsiella oxytoca, Death 24 Aeromonas hydrophila 4 1989 US 78 M Metastatic liver tumor Pneumonia Survival 24 5 1997 Taiwan 73 M Alcoholism, fatty liver STI Death 27 6 1997 Taiwan 51 M Biliary tract stone, Hepatitis B BSI Aeromonas sobria Survival 27 7 1997 Taiwan 71 M Biliary tract stone BSI Morganella Survival 27 morganii, Serratia marcescens, Flavobacterium odoratium 8 1997 Taiwan 61 M Liver cirrhosis BSI E. coli Survival 27 9 1997 Taiwan 71 M Cholangiocarcinoma, liver metastasis BSI E. coli Death 27 10 1997 Taiwan 85 F Pancreatic cancer, liver metastasis BSI E. coli Death 27 11 1997 Taiwan 81 M Biliary tract stone Biliary tract infection K. pneumonia Survival 27 12 2004 Taiwan 61 F Biliary tract stone Diarrhea E. coli, Survival 34 Edwardsiella tarda 13 2006 Korea 65 M Intraductal papillary mucinous tumor Infected biloma Survival 14 14 2007 Israel 62 F Pancreatic tumor, liver metastasis, colon BSI Survival 35 cancer, Krukenberg tumor, 15 2007 Japan 67 M PSC, liver cirrhosis, gastric cancer, STI Death 3 16 2008 Taiwan 76 F Gall bladder cancer, gastric cancer, Pericarditis Survival 6 17 2008 Taiwan 42 M Hepatitis B, Liver cirrhosis STI Survival 2 18 2009 Korea 58 M Liver cirrhosis STI Death 8 19 2010 Hong 47 M Cholangiocarcinoma Cholangitis E. coli, Death 9 Kong Citobacter diversus 20 2010 Hong 64 M Liver cirrhosis, hepatitis C, hepatoma Cholangitis Survival 9 Kong BSI: bacteremia, STI: soft tissue infection, PSC: Primary sclerosing cholangitis of patients with Shewanella bacteremia had hepatobiliary tion, the majority of our patients presented with hepatobili- diseases (9). An earlier report of Shewanella soft tissue in- ary infections. Ascending infections facilitated by abnormal fection in Taiwan also showed hepatobiliary disease to be a hepatobiliary anatomy may lead to the occasional develop- major risk factor among patients with bacteremic complica- ment of hepatobiliary infections caused by Shewanella.The tions (27). Our study showed a strong association between organism has been isolated from bile since it was first de- Shewanella infection and hepatobiliary malignancies. More- scribed as a possible human pathogen in 1970 (36) and is over, most of the patients in this study were newly diag- known to be associated with various hepatobiliary infec- nosed with hepatobiliary malignancies, and Shewanella bac- tions, including cholecystitis, cholangitis and liver ab- teremia was the initial presentation in most cases. In addi- scesses (1, 17, 37). Many of the reported patients had under-

435 Intern Med 52: 431-438, 2013 DOI: 10.2169/internalmedicine.52.8152 lying hepatobiliary structural abnormalities. The lipophilicity was noted in five cases. In the same study, the intra- of Shewanella and its tolerance to bile salts are proposed abdominal region was the most common site of isolation. causes of its affinity for bile and are possible virulence fac- The mean sea surface temperature of the central coastal tors in the development of hepatobiliary infec- area of Taiwan was found to be closely correlated with the tions (10, 27, 38). Overall, in our series and literature re- number of cases of Shewanella bacteremia in our case series view, 12 bacteremic patients presented with hepatobiliary in- (Figure). Shewanella is associated with aquatic environments fections, all of whom had underlying hepatobiliary diseases, and has been cultured from samples of animals that inhabit particularly malignancies, that resulted in biliary tract ob- these ecosystems, including fish, mollusks and crusta- struction. These findings demonstrate the importance of con- ceans (4). Shewanella has also been cultured directly from ducting appropriate imaging studies to determine the nature samples of seawater (42). Shewanella can grow over a wide of any underlying abnormalities. range of temperatures, although it tends to be more common Patients with hepatobiliary diseases are also predisposed in warmer waters (4). The mean sea surface temperature of to other marine bacterial infections such as infection with the central coastal area of Taiwan rises from a low of 18.8 Vibrio vulnificus or Aeromonas species. Iron overload is a ℃ during the period from January to March to a high of known risk factor that is highly related to these situations 28.6℃ during the period from July to September. Seven of due to its effects in decreasing neutrophil activity (39). the nine patients in this study developed onset of illness dur- Similarly, Shewanella species are one of the most diverse ing the warmer weather months of July, August and Septem- respiratory organisms and have the ability to reduce iron (4). ber. This association may reflect increased proliferation of In addition, siderophores have been reported to be extracel- Shewanella in warmer water, in seafood or both. In a study lular virulence factors of Shewanella species (10). Iron over- of Shewanella in Danish coastal water, the quantity of the load resulting from hepatic dysfunction has been speculated organism was found to be correlated with the temperature of to be associated with Shewanella infection by some ex- the seawater (42). Seasonal variations in the amount of in- perts (9). Associations with fulminant infections and associ- testinal Shewanella in tilapia were also reported in a study ated splenic dysfunction have also been suggested (40). A from Saudi Arabia, a country at the same latitude as Tai- potential association with splenic dysfunction is supported wan (46). Shewanella was the most abundant species of ti- by clear evidence of splenomegaly in our patients. More- lapia intestinal flora in that study, and the bacterial load was over, the majority of the fatal cases of Shewanella bactere- found to be highest in the summer. Adequate cooking kills mia in this study involved peripheral blood cytopenias, Shewanella; however, seafood is often eaten raw or under- which are often attributed to functional overactivity of the cooked in countries like Japan, Taiwan and Korea, thereby spleen in patients with chronic liver disease (41). Additional increasing the risk of infection with Shewanella. studies are therefore needed to further clarify this relation- Our study suggests that S. haliotis may be a human ship. pathogen within the Shewanella genus. S. haliotis was first Our findings also suggest an association between seafood detected in the gut of abalone in Korea (47). Abalone is also consumption and the development of Shewanella bactere- a commercially important mollusk cultured on the coast of mia. The majority of our patients (8/9, 88.8%) lived in Taiwan. In the area where this study was conducted, it is a coastal areas and consumed seafood regularly. Furthermore, local custom for abalone to be eaten as a prized delicacy. most patients (7/9; 77.7%) developed bacteremia during the Shewanella has also been isolated from abalone in the South summer season (July to September). Seawater contact is a China Sea (48). The most commonly reported Shewanella risk factor for Shewanella soft tissue and ear infec- species associated with human infections are S. algae and S. tion (9, 42). However, the route of transmission of bactere- putrefaciens. However, the methods of species identification mia remains undetermined. Ingestion of seafood has been used in most reports include biochemical reactions or auto- proposed as a possible explanation (9, 43). There are case mated systems. These methods are not reliable for differenti- reports of Shewanella bacteremia following seafood in- ating Shewanella species. Molecular typing required for de- take (3, 8, 43). Interestingly, the majority of cases are from finitive identification (4). 16S rRNA gene sequencing was Asian countries. Moreover, much of the literature that de- crucial for identifying the Shewanella bacteremia presented scribes an association between Shewanella infection and he- in this study. The availability of this technology allowed us patobiliary infection originates from Asian countries. These to recognize S. haliotis infections that otherwise would have findings may be associated with contamination of seafood been attributed to S. algae or S. putrefaciens. We recom- by Shewanella species, particularly in countries with a tradi- mend incorporating 16S rRNA gene sequencing into stan- tion of eating raw or undercooked seafood. Few studies dard identification procedures for Shewanella infection. We have investigated the ability of Shewanella to colonize the believe this will result in improved identification of Shewan- gastrointestinal tract. However, there are reports of Shewan- ella species, as well as the ability to offer directed therapy ella being isolated from stool cultures. In reports from India, and achieve improved clinical outcomes. In addition, this Shewanella was isolated from stool specimens of patients practice facilitates the identification of S. haliotis, suggesting with diarrhea (44, 45). In an 8-year study of Shewanella in- that S. haliotis infections may be more common than previ- fection in Hong Kong (9), asymptomatic bile colonization ously recognized.

436 Intern Med 52: 431-438, 2013 DOI: 10.2169/internalmedicine.52.8152

The antibiotic susceptibility patterns of our isolates are case. J Gastroenterol 42: 87-90, 2007. typical of those reported by others. Shewanella species are 4. Hau HH, Gralnick JA. Ecology and biotechnology of the genus Shewanella. Annu Rev Microbiol 61: 237-258, 2007. associated with the production of various β-lactamases, in- 5. Zong Z. Nosocomial peripancreatic infection associated with She- β cluding chromosome-encoded class B and class D - wanella xiamenensis. J Med Microbiol 60: 1387-1390, 2011. lactamases, while resistance to penicillin and first-generation 6. Tan CK, Lai CC, Kuar WK, Hsueh PR. Purulent pericarditis with cephalosporins are common (14, 49). In addition, Shewan- greenish pericardial effusion caused by Shewanella algae. J Clin ella has been noted to be less frequently susceptible to cer- Microbiol 46: 2817-2819, 2008. tain agents, including cefoxitin (1), and, more recently, 7. Gressier M, Mbayo D, Deramond H, Grados F, Eb F, Canarelli B. First case of human spondylodiscitis due to Shewanella algae. Int imipenem (14). Moreover, emergence of resistance to J Infect Dis 14 Suppl 3: e261-e264, 2010. piperacillin-tazobactam (6) and imipenem (14) during treat- 8. Myung DS, Jung YS, Kang SJ, et al. Primary Shewanella algae ment has been reported. These findings have particular sig- bacteremia mimicking Vibrio septicemia. J Korean Med Sci 24: nificance when selecting antimicrobial agents for empirical 1192-1194, 2009. treatment of biliary tract infections. Antibiotics such as cefa- 9. To KK, Wong SS, Cheng VC, et al. Epidemiology and clinical features of Shewanella infection over an eight-year period. Scand zolin or cefoxitin, which are often administered to empiri- J Infect Dis 42: 757-762, 2010. cally treat intra-abdominal infections, may be ineffective if 10. Holt HM, Gahrn-Hansen B, Bruun B. Shewanella algae and She- Shewanella species are present. Another area of concern is wanella putrefaciens: clinical and microbiological characteristics. the presence of drug-resistant strains in the environment. Clin Microbiol Infect 11: 347-352, 2005. The qnr gene has also been detected in Shewanella isolated 11. Saltikov CW, Cifuentes A, Venkateswaran K, Newman DK. The ars detoxification system is advantageous but not required for As from the coastal waters of China (50). The plasmid-borne (V) respiration by the genetically tractable Shewanella species quinolone resistance gene is common in drug-resistant En- strain ANA-3. Appl Environ Microbiol 69: 2800-2809, 2003. terobacteriaceae. Close monitoring for possible emergence 12. Wilson KH, Blitchington RB, Greene RC. Amplification of bacte- of quinolone resistance in Shewanella is needed. rial 16S ribosomal DNA with polymerase chain reaction. J Clin Our study is associated with some limitations. First, we Microbiol 28: 1942-1946, 1990. 13. Clarridge JE 3rd. Impact of 16S rRNA gene sequence analysis for reported detailed information from only one tertiary care identification of bacteria on clinical microbiology and infectious center. In that sense, our data set does not represent patients diseases. Clin Microbiol Rev 17: 840-862, 2004. overall and is subject to biases regarding referrals for ad- 14. Kim DM, Kang CI, Lee CS, et al. Treatment failure due to emer- vanced care. Patients with mild diseases were most likely gence of resistance to carbapenem during therapy for Shewanella underrepresented. Second, we were unable to obtain detailed algae bacteremia. J Clin Microbiol 44: 1172-1174, 2006. 15. Bhandari S, Pan TL, Horvath J, Tiller D. CAPD, swimming in information about the type, quantity and timing of seafood Shewanella. Nephrol Dial Transplant 15: 1484-1485, 2000. consumptions; thus, the incubation period cannot be deter- 16. Paccalin M, Grollier G, le Moal G, Rayeh F, Camiade C. Rupture mined. 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