Cellulitis due to Pseudomonas putrefaciens: possible production of exotoxins

Shewanella infection in humans: Epidemiology, clinical features and pathogenicity

The genus Shewanella consists of Gram-negative proteobacteria that are ubiquitously distributed in environment. As the members of this genus have rapidly increased within the past decade, several species have become emerging pathogens worldwide, attracting the attention of the medical community. These species are also associated with severe community- and hospital-acquired infections. Patients infected with Shewanella spp. had experiences of occupational or recreational exposure; meanwhile, the process of infection is complex and the pathogenicity is influenced by a variety of factors. Here, an exhaustive internet-based literature search was carried out in PUBMED using terms “Achromobacter putrefaciens,” “Pseudomonas putrefaciens,” “Alteromonas putrefaciens” and “Shewanella” to search literatures published between 1978 and June 2022. We provided a comprehensive review on the epidemiology, clinical features and pathogenicity of Shewanella, which will contribute a better understanding of its clinical aetiology, and facilitate the timely diagnosis and effective treatment of Shewanella infection for clinicians and public health professionals.

Emerging Infections Due to Shewanella spp.: A Case Series of 128 Cases Over 10 Years

Background

Shewanella species are emerging pathogens that can cause severe hepatobiliary, skin and soft tissue, gastrointestinal, respiratory infections, and bacteremia. Here we reported the largest case series of infections caused by Shewanella species.

Aim

To identify the clinical features and risk factors predisposing to Shewanella infections. To evaluate resistance pattern of Shewanella species and appropriateness of antibiotic use in the study cohort.

Methods

Patients admitted to a regional hospital in Hong Kong with Shewanella species infection from April 1, 2010 to December 31, 2020 were included. Demographics, antibiotics, microbiology, and outcomes were retrospectively analyzed.

Findings

Over the 10 years, we identified 128 patients with Shewanella species infection. 61.7% were male with a median age of 78 (IQR 65–87). Important underlying diseases included hepatobiliary diseases (63.3%), malignancy (26.6%), chronic kidney disease or end-stage renal failure (25.8%), and diabetes mellitus (22.7%). Hepatobiliary infections (60.4%) were the most common clinical manifestation. Majority (92.2%) were infected with Shewanella algae, while 7.8% were infected with Shewanella putrefaciens. The identified organisms were usually susceptible to ceftazidime (98.7%), gentamicin (97.4%), cefoperazone-sulbactam (93.5%) and ciprofloxacin (90.3%). Imipenem-susceptible strains were only present in 76.6% of isolates.

Conclusion

This largest case series suggested that Shewanella infections are commonly associated with underlying comorbidities, especially with hepatobiliary diseases and malignancy. Although Shewanella species remained largely susceptible to third and fourth generation cephalosporins and aminoglycosides, carbapenem resistance has been on a significant rise.

Shewanella putrefaciens: a rare cause of purulent otorrhoea

Shewanella putrefaciens is a Gram-negative, non-fermenting, motile and oxidase-positive bacillus. Its incrimination in human pathology is very rare, although there has been a resurgence in Shewanella infections in recent years. We report the first case in Morocco of a purulent otorrhoea caused by S. putrefaciens , resistant to conventional treatment, occurring in a 25-year-old female, afebrile, without deterioration of the general state and possibly acquired during sea bathing. We also describe the bacteriological characteristics of and antibiotic susceptibility results for the isolate.

Shewanella putrefaciens: A cause of bacteremia not to neglect

Shewanella putrefaciens is a Gram-negative bacillus and marine pathogen that rarely causes disease in humans. We report the first Moroccan case of multidrug-resistant Shewanella putrefaciens bacteremia and describe the bacteriological, clinical, and antibiogram characteristics of this isolate, which was repeatedly isolated from the blood of a 66-year-old hypertensive man who underwent femoral coronary angiography after a myocardial infarction.

Bacteremia and empyema caused by Shewanella algae in a trauma patient

OBJECTIVE

To describe the first reported case of bacteremia and empyema caused by Shewanella algae and summarize the existing literature on Shewanella human infection.

CASE SUMMARY

A 25-year-old healthy male was shot through the chest into the abdomen and fled into an adjacent body of seawater. He underwent surgical repair of his injuries, including pleural decortication. Leukocytosis, bandemia, and copious yellow bronchorrhea led to cultures; piperacillin/tazobactam and vancomycin were started for broad-spectrum empiric management based on the local intensive care unit antibiogram. Blood and pleural fluid cultures revealed S algae. Sputum cultures grew methicillin-sensitive Staphylococcus aureus and Haemophilus influenzae. He was successfully managed with an empiric and then tailored antibiotic regimen.

DISCUSSION

Shewanella algae is a rare Gram-negative bacillus that has infrequently been reported to cause infection. It is found predominantly in men. Shewanella algae infections span bacteremia to necrotizing soft tissue infection and are associated with injury and seawater exposure. Shewanella is susceptible to the majority of third- and fourth-generation cephalosporins, aminoglycosides, chloramphenicol, erythromycin, aztreonam, and fluoroquinolones, but are less predictably susceptible to tetracycline and trimethoprim/sulfamethoxazole and carbapenem agents. Shewanella infection is associated with medical comorbidities, in particular, renal failure and cardiovascular disease.

CONCLUSIONS

To our knowledge, this is the first case report of bacteremia and empyema caused by S algae. Such a case involving a young healthy individual should encourage health care providers to be aware of the potential infections caused by unusual pathogens, and to employ appropriate empiric antibiotic therapy based on reported sensitivity profiles. Based on available susceptibilities, we recommend using a third or fourth-generation cephalosporin as first-line pharmacologic management with regimen de-escalation based on culture-derived data.

Shewanella algae: a rare cause of necrotizing fasciitis

BACKGROUND

The genus Shewanella consists of motile, gram-negative, facultative anaerobes found in marine environments. Shewanella putrefaciens and Shewanella algae are the two species with documented pathogenicity in human beings. Most documented cases of S. algae infection worldwide have been reported in the context of bacteremia, cellulitis, and acute exacerbations of chronic otitis media in predisposed individuals. We report a rare case of necrotizing soft tissue infection by S. algae in an immunocompetent individual. The infection followed exposure to S. algae in contaminated water in New York City, New York.

METHODS

We reviewed the English-language literature on similar cases of soft tissue infection using PubMed. Search terms included "Shewanella algae" and "Shewanella putrefaciens" in conjunction with "necrotizing" and "infection." Cognizant that this search method may not have yielded early (pre-1985) reports about Shewanella because of changes in classification and nomenclature, we also searched for "Pseudomonas putrefaciens."

RESULTS

After prompt surgical debridement and culture-directed antibiotic therapy, the patient recovered from his infection without the need for re-intervention.

CONCLUSIONS

This case may reflect the geographic spread and emergence of S. algae infection in the United States. Clinicians should be aware of the virulence of S. algae and potential for the rapid clinical deterioration of persons it infects even among immunocompetent individuals.

Human infection with Shewanella putrefaciens and S. algae: report of 16 cases in Martinique and review of the literature

Shewanella spp. are saprophytic bacteria that are part of the marine microflora in warm climates and are rarely pathogenic. However, Shewanella spp. infections are being increasingly reported, and there has been no comprehensive review of the literature describing these infections. This article reports 16 cases of Shewanella spp. infections in Martinique since 1997 and reviews another 239 cases reported in the literature since 1973. Patients experienced soft tissue infections, ear infection, or abdominal and biliary tract infections. A skin or mucosal portal of entry was found for 53% of the patients and exposure to the marine environment was reported for 44%; 79% of patients had an underlying condition. Bacteriema were frequent (28%). Most (87%) patients recovered, although ear infections can become chronic. Death occurred in 13% of the patients. Most Shewanella spp. isolates are susceptible to cefotaxime (95%), piperacillin and tazobactam (98%), gentamicin (99%), and ciprofloxacin (94%).

Soft tissue infections caused by marine bacterial pathogens: epidemiology, diagnosis, and management

Skin and soft tissue infections (SSTIs) are one of the most common infection syndromes and may be caused by a large number of microorganisms. Some principles of aquatic injuries are different than those of land-based trauma. Wounds sustained in marine environment are exposed to a milieu of bacteria rarely encountered in different settings. These include Vibrio spp., Aeromonas spp., Shewanella spp., Erysipelothrix rhusiopathiae, Mycobacterium marinum, Streptococcus iniae, and other microbes. Failure to recognize and treat these uncommon pathogens in a timely manner may result in significant morbidity or death. These infections are frequently contracted as a result of recreational swimming, fishing injuries, or seafood handling. The spectrum of manifestations is wide, varying from cases of mild cellulitis, to severe life-threatening necrotizing fasciitis requiring radical surgery, to sepsis and death. This review will focus on the epidemiology, clinical manifestations, and treatment of SSTIs caused by the most important marine pathogens.

Emerging infections: shewanella - a series of five cases

Background:

Shewanella spp. are unusual cause of disease in humans; however, reports of Shewanella infections have been increasing. Shewanella is a ubiquitous organism that has been isolated from many foods, sewage, and both from fresh and salt water. Earlier it was named as Pseudomonas putrefaciens or Shewanella putrefaciens. There are several reports describing this organism causing human infections such as cellulitis, abscesses, bacteremia, wound infection, etc. It is oxidase and catalase-positive non-fermenter gram-negative rod that produces hydrogen sulfide.

Aims:

The study was conducted to identify Shewanella spp., which was wrongly reported as Pseudomonas spp.

Materials and Methods:

Clinical samples were cultured as per standard clinical laboratory procedure. We tested the non-lactose-fermenting colonies for oxidase positivity. Oxidase-positive colony was inoculated in triple sugar iron slant (TSI) to know the hydrogen sulfide production. Hydrogen sulfide positive colonies were further tested for citrate, urease, indole, and amino acid decarboxylation and acid and gas production from sugars.

Results:

Five isolates identified as Pseudomonas spp. during preliminary testing were proved to be Shewanella spp. on further testing.

Conclusions:

It will help in better understanding the epidemiology, pathogenesis and risk factors associated with these and prevention of the rare pathogenic organisms.

Biological characteristics and pathogenicity of a highly pathogenic Shewanella marisflavi infecting sea cucumber, Apostichopus japonicus

Shewanella marisflavi isolate AP629 is described as a novel pathogen of sea cucumber. The LD(50) values (14 days) in sea cucumber, mice and swordtail fish were 3.89 × 10(6) , 6.80 × 10(4) and 4.85 × 10(4) CFU g(-1) body weight, respectively. Studies on S. marisflavi were conducted, including morphology, physiological and biochemical characteristics, haemolysis, whole-cell protein and 16S rDNA gene sequence. Colonies of S. marisflavi appeared faint red on marine agar and green on thiosulphate-citrate-bile salt-sucrose media. Shewanella marisflavi had polar flagella. The cells were Gram-negative, oxidase- and catalase-positive and not sensitive to O/129. The bacterium exhibited β-haemolysis on sheep blood agar and produced H(2) S. Shewanella marisflavi survived and grew at 4-35°C, pH 6.0-9.2 and in the presence of 0-8% NaCl. The whole-cell proteins included 13 discrete bands, and proteins of molecular weight 87, 44 and 39 kDa were found in all five strains of Shewanella spp. The difference in 16S rDNA gene sequences in S. marisflavi was at the 446 bp site: S. marisflavi (KCCM 41822) - G, isolate AP629 - A. This is the first report that Shewanella is pathogenic to sea cucumber.

Shewanella soft tissue infection: case report and literature review

OBJECTIVE

To better understand the clinical characteristics of soft tissue infections caused by Shewanella in humans.

METHODS

We report a case of Shewanella soft tissue infection and review the English literature from a search of PubMed.

RESULTS

A total of 27 adults (mean age 61.1+/-16.0 years) with soft tissue infections caused by Shewanella were included for analysis. Limb involvement was found in 22 (81.5%) patients, while scalp, face, perineum, lacrimal sac, and abdominal wall involvement were each found in one patient. Chronic ulcer over the leg (14 cases (51.9%)), steroid use (four cases (14.8%)), and liver cirrhosis (three cases (11.1%)) were the major underlying conditions. Shewanella bacteremia was found in 14 out of 22 patients with soft tissue infections involving the limbs. Two patients died of septicemia, giving a mortality rate of 7.4%.

CONCLUSIONS

Shewanella soft tissue infections usually develop in immunocompromised patients with a preexisting cutaneous ulcer (particularly over the legs) after marine environment or seawater exposure. In view of the possible catastrophic consequences, education on the prevention of Shewanella soft tissue infections in at-risk people (e.g., the immunocompromised or elderly with a cutaneous ulcer) relating the need to avoid exposure to the marine environment or seawater may be of importance.

Shewanella algae and Shewanella putrefaciens: clinical and microbiological characteristics

The occurrence of the two Shewanella species found in clinical specimens, Shewanella algae and Shewanella putrefaciens, correlates with the temperature and salinity of seawater. This means that Shewanella infections occur in warm climates or during especially warm summers in temperate climates. The infections described most commonly involve ears, skin and soft tissue, with or without bacteraemia. Primary bacteraemia with a fulminant course is also seen in immunocompromised patients. Important differential characteristics between the two species include the ability of S. algae to produce mucoid colonies with beta-haemolysis on sheep blood agar, to grow at 42 degrees C and in NaCl 6% w/v, and to reduce nitrite, and an inability to produce acid from maltose, all of which are in contrast to the characteristics of S. putrefaciens. Automated identification systems fail to differentiate between S. algae and S. putrefaciens, as S. algae is not included in the databases of these systems. Presumably for this reason, most Shewanella infections reported during recent years have been attributed to S. putrefaciens. However, when extensive phenotypic characterisation is performed, most human infections are seen to be caused by S. algae. As the two species seem to have different pathogenic potential for humans, correct identification is important, and this is possible in routine clinical microbiology laboratories.

[Opportunistic infections caused by Shewanella, new emergent bacteria]

Shewanella putrefaciens and Shewanella algae are Gram negative, nonfermentative and oxidative bacilli whose the main phenotypic feature is the production of hydrogen sulfide gas. Widespread in the environment, both S. putrefaciens and S. algae species are rare human bacteria although they are reported with increasing frequency as a cause of opportunistic infection in humans, such as skin and soft tissue infections and bacteremia. Chronic infections of the lower limbs and liver disease have been identified as risk factors for bloodstream infection, with a faster course and a poorer prognosis in the last case. S. algae appears to be more virulent than S. putrefaciens. Most human S. putrefaciens strains are isolated from bacterial flora, which puts to question its clinical significance. Molecular biology must be used for an adequate identification because S. algae can easily be mistaken for S. putrefaciens with usual tests.

A rare cause of wound infection: Shewanella putrefaciens

Shewanella putrefaciens has a wide geographical distribution, including all forms of sea water, fresh water, fish and soil. In humans, it is an unusual pathogen of wound infections. In this report, a wound infection was presented in a previously healthy man.

Cutaneous manifestations of waterborne infections

Although waterborne pathogens are relatively uncommon causes of cutaneous infections, these agents are being recognized with increasing frequency. Humans are exposed to water through a variety of recreational and occupational activities. Poor sanitary conditions in developing nations place the human populations at constant risk. Some aquatically acquired skin infections respond well to therapy, whereas other diseases do not require a specific treatment. However, many of these infections are rare, and effective therapy has not been defined. Gram-negative bacilli constitute the largest group of aquatic pathogens that cause skin infections. Other agents include mycobacteria, fungi, viruses, and amoeba and other parasites. Toxins from aquatic animals and parasites are associated with cutaneous diseases. Because waterborne skin infections, which are caused by a wide variety of pathogens, occur infrequently, most of the literature on the topic are case reports. This paper reviews the aquatic pathogens associated with cutaneous infections in humans and the available treatments.

Concurrent infection due to Shewanella putrefaciens and Mycobacterium marinum acquired at the beach

Infection with marine bacteria is uncommon. A patient with systemic lupus erythematosus who developed concurrent infection with Shewanella putrefaciens and Mycobacterium marinum (M. marinum) is described. After bathing leg ulcers in sea water, severe cellulitis of the left leg with necrotic areas and extensive bullae developed. Infection due to S. putrefaciens was confirmed and a long course of hospitalization, oral ciprofloxacin and skin grafting was required. During hospitalization subcutaneous nodules developed on the other leg. Biopsy revealed acid-fast bacilli and culture grew M. marinum. These lesions responded to rifampicin and cotrimoxazole. Patients with leg ulcers, peripheral vascular disease, diabetes, or receiving immunosuppressive drugs may acquire unusual infections after salt water exposure.

Biochemical and pathogenic properties of Shewanella alga and Shewanella putrefaciens

We characterized 49 strains of Shewanella spp. from clinical (n = 31) and nonhuman (n = 18) sources. Most Shewanella alga organisms (Gilardi biovar 2; Centers for Disease Control and Prevention [CDC] biotype 2) originated from clinical material (92%), failed to produce acid from carbohydrates other than D-ribose, and were biochemically and enzymatically fairly homogeneous. In contrast, Shewanella putrefaciens organisms (Gilardi biovars 1 and 3; CDC biotype 1) were more often associated with nonhuman sources (70%), were able to utilize a number of sugars (sucrose, L-arabinose, and maltose), and were found to exhibit wider variations in biochemical characteristics; three biotypes within S. putrefaciens were detected. Notable differences between the two species in enzymatic activity, determined with the API-ZYM system (bioMérieux, Hazelwood, Mo.), and cellular fatty acid profiles, determined by the MIDI system (Microbial ID Inc., Newark, Del.), were also detected. Pathogenicity studies of mice indicate that S. alga appears to be the more virulent species, possibly due to the production of a hemolytic substance.

Differentiation of Shewanella putrefaciens and Shewanella alga on the basis of whole-cell protein profiles, ribotyping, phenotypic characterization, and 16S rRNA gene sequence analysis

Seventy-six presumed Shewanella putrefaciens isolates from fish, oil drillings, and clinical specimens, the type strain of Shewanella putrefaciens (ATCC 8071), the type strain of Shewanella alga (IAM 14159), and the type strain of Shewanella hanedai (ATCC 33224) were compared by several typing methods. Numerical analysis of sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell protein and ribotyping patterns showed that the strains were separated into two distinct clusters with 56% +/- 10% and 40% +/- 14% similarity for whole-cell protein profiling and ribotyping, respectively. One cluster consisted of 26 isolates with 52 to 55 mol% G + C and included 15 human isolates, mostly clinical specimens, 8 isolates from marine waters, and the type strain of S. alga. This homogeneous cluster of mesophilic, halotolerant strains was by all analyses identical to the recently defined species S. alga (U. Simidu et al., Int. J. Syst. Bacteriol, 40:331-336, 1990). Fifty-two typically psychrotolerant strains formed the other, more heterogeneous major cluster, with 43 to 47 mol% G + C. The type strain of S. putrefaciens was included in this group. The two groups were confirmed by 16S rRNA gene sequence analysis. It is concluded that the isolates must be considered two different species, S. alga and S. putrefaciens, and that most mesophilic isolates formerly identified as S. putrefaciens belong to S. alga. The ecological role and potential pathogenicity of S. alga can be evaluated only if the organism is correctly identified.

Ear infections with Shewanella alga: a bacteriologic, clinical and epidemiologic study of 67 cases

OBJECTIVE: To present bacteriologic and clinical data on 67 patients from the island of Funen, Denmark, with Shewanella alga, a bacterium rarely seen in Scandinavia, isolated from ear swabs. Included in the study is an examination of the occurrence of S. alga in sea water around the island. METHODS: Bacteriologic examination and antibiotic susceptibility testing of 67 clinical isolates, 11 sea-water isolates and two reference strains were conducted. Clinical information was obtained from the referring physicians. RESULTS: During 6 months S. alga was isolated from 67 patients, in 33 cases in pure culture. Seventy per cent of the patients were children between 3 and 15 years old who had clinical symptoms of acute or chronic otitis media. Previous ear disease was common (76%). Most of the cases (85%) occurred in August or September, and 47 of 55 patients reported contact with sea water shortly before symptoms developed. From seven of the patients, S. alga was isolated more than once. The species was also isolated from five of 10 bathing areas around the island of Funen. CONCLUSIONS: The patients were probably infected with S. alga during sea-water bathing in the unusually warm summer of 1994. Infections with marine bacteria are possible in countries with a temperate climate; patients with previous ear disease are at special risk.