Soft tissue infections following water exposure

INTRODUCTION — Soft tissue infection due to a broad array of organisms can occur in patients with traumatic injury associated with water exposure [1,2].

The epidemiology, microbiology, clinical manifestations, diagnosis, and treatment of soft tissue infections following water exposure are reviewed here.

Issues related to jellyfish stings and marine envenomations are discussed separately. (See "Jellyfish stings" and "Marine envenomations from corals, sea urchins, fish, or stingrays".)

EPIDEMIOLOGY — The risk of soft tissue infection due to traumatic injury with water exposure may be considered in the following hierarchy (from highest to lowest risk) (table 1) [1-3]:

●Fresh water (ponds, small lakes)

●Flowing fresh water (rivers, large lakes)

●Brackish water (water that is saltier than fresh water but less salty than sea water, found where bodies of sea water and fresh water meet)

●Sea water

●Well-regulated treated water (swimming pools, hot tubs)

In addition to water, other relevant exposures may include mud, sand, debris, or sewage.

Injuries associated with water exposure include lacerations (due to inanimate objects in water), puncture wounds due to fish hooks or fish spines, and bites from aquatic animals [4-7]. In addition, water exposure in patients with pre-existing wounds can result in infection.

Individuals at risk for soft tissue infection following water exposure include [8-13]:

●Recreational swimmers, fisherman, boaters, fishmongers

●Flooding victims and rescue workers

●People undergoing leech therapy

●Patients with underlying liver disease and immunosuppression

●People who inject drugs [14-16]

MICROBIOLOGY — Some of the organisms that can cause soft tissue infections following water exposure include (table 1) [1,2,17-19]:

●Aeromonas spp (see "Aeromonas infections")

●Burkholderia pseudomallei (see "Melioidosis: Epidemiology, clinical manifestations, and diagnosis")

●Chromobacterium violaceum

●Edwardsiella tarda

●Erysipelothrix rhusiopathiae (see "Erysipelothrix infection")

●Mycobacterium fortuitum (see "Rapidly growing mycobacterial infections: Mycobacteria abscessus, chelonae, and fortuitum")

●Mycobacterium marinum

●Plesiomonas spp (see "Plesiomonas shigelloides infections")

●Pseudomonas aeruginosa (see "Pseudomonas aeruginosa skin and soft tissue infections")

●Shewanella spp

●Streptococcus iniae

●Vibrio spp (see "Vibrio vulnificus infection" and "Vibrio parahaemolyticus infections" and "Minor Vibrio and Vibrio-like species associated with human disease")

Note that this listing of organisms is not all-inclusive; thus, it is important to obtain specimens (blood, drainage, tissue) for microbiologic examination when possible. In addition, soft tissue infection following water exposure can be caused by organisms unrelated to water exposure (such as beta-hemolytic streptococci and Staphylococcus aureus). Polymicrobial infection may occur [20,21]. (See "Cellulitis and skin abscess: Epidemiology, microbiology, clinical manifestations, and diagnosis" and "Necrotizing soft tissue infections".)

The microbiology depends on the type of water exposure as well as individual patient factors (table 1).

CLINICAL EVALUATION

History and physical examination — In patients presenting for initial evaluation and management of a wound associated with water exposure, a thorough exposure history should be obtained, including occupational and home exposures, hobbies, and recent travel history.

Soft tissue infection following water exposure may be superficial (eg, cellulitis, with or without abscess) or deep (abscess, septic arthritis, osteomyelitis, tenosynovitis, or necrotizing soft tissue infection) [11]:

●Clinical manifestations of cellulitis include fever, tenderness, erythema, swelling, and warmth; purulent drainage and/or lymphangitis may be present. An associated superficial abscess may present as a tender, erythematous, fluctuant nodule or lump.

●In addition to the above manifestations, clues for deep infection include persistent or progressive pain several days following the initial injury, pain with passive movement, pain out of proportion to exam findings, crepitus, joint swelling, systemic illness (fever, hemodynamic instability), and persistent signs of infection despite initial wound care and antibiotic administration.

The level of suspicion for deep infection should be increased for patients with immunosuppression (including diabetes) or neuropathy; these patients often present later in their course with increased risk of serious infection and limited pain on clinical exam.

The clinical manifestations, microbiology, epidemiology, and incubation period for various infections following water exposure are summarized in the table (table 1).

The range of clinical manifestations of skin and soft tissue infections following water exposure is illustrated by the following examples:

●Vibrio vulnificus is associated with rapidly progressive soft tissue infection (incubation period three to seven days). Relevant epidemiologic exposures include raw oyster ingestion and/or exposure of puncture wounds to salt water, especially in males with chronic liver disease. When ocean waters are warmer than usual, rates of infection due to V. vulnificus may increase; for example, in the summer of 2023, the United States Centers for Disease Control and Prevention (CDC) issued a warning about increasing infections along the East Coast and Gulf of Mexico, associated with warmer than normal ocean temperatures [22]. Clinical manifestations may include cellulitis, hemorrhagic bullae, ulcers, necrotizing infection with compartment syndrome, ecthyma gangrenosum, and septicemia (picture 1). (See "Vibrio vulnificus infection" and "Necrotizing soft tissue infections".)

●M. marinum is associated with indolent infection (mean incubation period 21 days). Relevant epidemiologic exposures include cleaning salt water aquariums, punctures from fish hooks, or seafood preparation involving crustaceans. Lesions usually appear as papules or nodules on an extremity (especially on the elbows, knees, and dorsum of feet and hands); subsequently, they progress to shallow ulceration and scar formation (picture 2). Most lesions are solitary; occasionally "ascending" lesions develop with "sporotrichoid spread" (ie, resembling sporotrichosis; also called nodular lymphangitis). In one series including 31 patients with M. marinum infection, the upper extremity was affected in 90 percent of cases; nodular lymphangitis occurred in 81 percent of cases [23]. (See "Clinical features and diagnosis of sporotrichosis", section on 'Nodular lymphangitis' and "Epidemiology of nontuberculous mycobacterial infections" and "Pseudomonas aeruginosa skin and soft tissue infections", section on 'Hot tub-associated eruptions' and "Lymphangitis", section on 'Nodular lymphangitis'.)

Clinical manifestations of necrotizing soft tissue infection (erythema, edema, warmth, and signs of systemic illness [fever, hemodynamic instability] in association with crepitus, rapid progression of clinical manifestations, and/or severe pain [out of proportion to skin findings in some cases]) are discussed separately. (See "Necrotizing soft tissue infections".)

The likelihood of wound infection should be determined based upon physical findings.

Laboratory testing — For patients with clinically uninfected wounds, routine laboratory studies are not indicated. Similarly, wound cultures are not indicated; such results do not correlate with subsequent infection.

For patients with clinically infected wounds, laboratory studies (complete blood count and serum inflammatory markers such as erythrocyte sedimentation rate, C-reactive protein) are reasonable. In addition, wound cultures (aerobic and anaerobic) should be obtained from infected wounds to establish the microbiology of the infection and to guide antibiotic therapy.

If consideration of M. marinum is warranted, the microbiology laboratory should be notified so that acid-fast staining and mycobacterial culture can be performed; growth of M. marinum is generally restricted to lower temperatures. Other diagnostic tools that may be useful to establish a diagnosis of M. marinum infection include histopathology, immunohistochemistry (IC), and polymerase chain reaction (PCR) from full-thickness skin biopsy; IC and PCR may not be readily available in most clinical laboratories [24].

Blood cultures should be obtained in the setting of fever or hemodynamic instability, as well as in patients at increased risk for systemic infection (including underlying hepatic disease, cancer, or immunosuppression).

Imaging — Imaging is not necessary for most clinically uninfected, superficial wounds. Deep wounds, including those near joints warrant diagnostic imaging (plain radiography) to exclude retained foreign body [2].

MANAGEMENT

Uninfected wound — Management of a wound following water exposure includes wound care and evaluation regarding need for antibiotic prophylaxis and/or tetanus prophylaxis.

Wound management — Wounds associated with water exposure should be irrigated copiously with sterile saline. Crushed or devitalized tissues should be debrided and foreign bodies should be removed if present.

Closure — The optimal approach to closure of uninfected wounds associated with water exposure is uncertain and depends in part on the nature of the exposure. (See 'Epidemiology' above.)

Indications for surgical consultation are summarized below. (See 'Surgical consultation' below.)

In general, closure of wounds associated with exposure to a treated swimming pool or hot tub is reasonable. In addition, closure of large wounds or wounds in cosmetically important areas associated with exposure to sea water, brackish water, or relatively clean fresh water (such as rivers or large lakes) may be reasonable.

For patients with wounds in cosmetically important areas associated with exposure to ponds or small lakes who do not undergo surgical debridement, it may be reasonable to administer prophylactic antibiotics followed by return for delayed primary closure after two to three days if no signs of infection are present.

Follow-up of patients with closed traumatic wounds is important, particularly in the first several days following closure. Such follow-up may be done via outpatient visits and/or via serial photographs sent by patients (depending upon the severity of the injury and available resources).

Surgical consultation — Surgical consultation is warranted in the following circumstances:

●Substantial wounds associated with exposure to a pond or small lake

●Complex facial lacerations

●Deep wounds that penetrate bone, tendons, joints, or other major structures

●Wounds associated with neurovascular compromise

Antibiotic prophylaxis — The optimal approach to post-exposure prophylactic antibiotic therapy in patients with an open wound associated with water exposure (in the absence of established infection) is uncertain; there are no clinical trial data evaluating whether prophylactic therapy is beneficial [25].

In general, post-exposure prophylactic antibiotic therapy is reasonable in the following circumstances:

●Deep puncture wound or laceration (beyond the dermis)

●Wounds requiring surgical repair

●Wounds undergoing primary closure associated with any water exposure apart from well-regulated treated swimming pools or hot tubs (see 'Epidemiology' above)

●Wound with associated crush injury

●Wound in area of underlying vascular or lymphatic compromise

●Wound on the hands, feet, face, or genital area

●Wound near a bone or joint (particularly a prosthetic joint)

●Wounds in immunocompromised patients or those with diabetes or chronic liver disease

The choice of prophylactic antibiotic therapy should be based on the epidemiology of the exposure and patient factors. (See 'Empiric therapy' below.)

The duration of prophylactic oral antibiotics is three to five days, with close follow-up. Signs of infection on follow-up examination should prompt further evaluation (with radiographic imaging and/or surgical consultation, if needed), an extension of the antibiotic course, and/or a switch to intravenous therapy.

Infected wound — Management of patients with soft tissue infection following water exposure includes wound debridement (with collection of microbiology specimens) and administration of empiric antibiotic therapy. In addition, patients should be evaluated regarding need for tetanus prophylaxis. (See 'Preventing tetanus' below.)

Management of patients with suspected necrotizing soft tissue infection is discussed separately. (See "Necrotizing soft tissue infections" and "Surgical management of necrotizing soft tissue infections".)

Wound management — Wounds associated with water exposure should be irrigated copiously with sterile saline. Crushed or devitalized tissues should be debrided and foreign bodies should be removed if present. Specimens (eg, lesion aspirate or biopsy) should be sent for Gram stain and culture (aerobic and anaerobic) as well as acid-fast stain and mycobacterial culture.

Acute infected wounds associated with water exposure should be left open with approximation of wound edges to facilitate closure by secondary intention following initial debridement. Delayed primary closure may be reasonable for facial wounds, large lacerations, and disfiguring wounds; factors to consider in this decision are discussed separately. (See "Basic principles of wound management" and "Assessment and management of facial lacerations".)

Antibiotic therapy

Route of therapy — Inpatient administration of intravenous antibiotics is warranted for patients with systemic symptoms (eg, fever, chills, rigors) and/or leukocytosis. Similarly, intravenous antibiotic therapy is warranted for patients with underlying hepatic disease, cancer, or immunosuppression; these groups are at increased risk for complications including bacteremia, sepsis and, death.

The route of antibiotic administration may be switched from parenteral to oral once fever and soft tissue findings have begun to resolve (often three to five days).

In the absence of the above factors, outpatient administration of oral antibiotic therapy is reasonable, with close follow-up within 24 to 48 hours.

Empiric therapy — Empiric antibiotic regimens are based on the most likely organisms to cause infection, in vitro susceptibility studies, and treatment case series [1-3].

For patients with soft tissue infection following water exposure, we use the following antibiotics for initial empiric therapy:

●A first-generation cephalosporin (cephalexin 500 mg orally four times daily or cefazolin 1 g intravenously every eight hours); for patients with immediate hypersensitivity reactions to cephalosporins, linezolid (600 mg orally or intravenously every 12 hours) is an alternative agent.

PLUS

●A fluoroquinolone such as levofloxacin (750 mg once daily)

PLUS (if epidemiologic risk is present)

●Seawater exposure: doxycycline (100 mg twice daily) for coverage of Vibrio species

●Soil-contaminated wound or exposure to sewage-contaminated water: metronidazole (500 mg four times daily) for anaerobic coverage

Issues related to empiric treatment of patients with suspected necrotizing soft tissue infection are discussed separately. (See "Necrotizing soft tissue infections".)

Empiric antibiotic therapy need not include coverage for mycobacterial infection unless acid-fast staining is positive. In such cases, directed therapy should be administered as described below. (See 'Mycobacterial infection' below.)

Directed therapy

Bacterial infection — Empiric antibiotic therapy should be tailored to microbiology data when available. General information regarding antimicrobial susceptibility for organisms associated with water exposure is presented in the table (table 1).

Treatment of infection due to Aeromonas spp, B. pseudomallei, E. rhusiopathiae, Plesiomonas spp, P. aeruginosa, S. aureus, Streptococcus pyogenes, and Vibrio spp is discussed in detail separately. (See "Aeromonas infections" and "Melioidosis: Treatment and prevention" and "Erysipelothrix infection" and "Plesiomonas shigelloides infections" and "Pseudomonas aeruginosa skin and soft tissue infections" and "Acute cellulitis and erysipelas in adults: Treatment" and "Vibrio vulnificus infection" and "Vibrio parahaemolyticus infections" and "Minor Vibrio and Vibrio-like species associated with human disease".)

Issues related to treatment of patients with suspected necrotizing soft tissue infection are discussed separately. (See "Necrotizing soft tissue infections".)

For most soft tissue infections due to bacteria associated with water exposure, a reasonable duration of therapy is 10 to 14 days. If local signs of infection persist after two weeks of treatment, we continue antibiotic therapy until signs of infection resolve.

Mycobacterial infection — Patients with infection due to nontuberculous mycobacteria (M. fortuitum or M. marinum) generally warrant months of therapy. Issues related to treatment of M. fortuitum infection are discussed separately. (See "Rapidly growing mycobacterial infections: Mycobacteria abscessus, chelonae, and fortuitum".)

Treatment of M. marinum infection is based on in vitro susceptibility testing and case reports; the optimal approach is uncertain [26,27]. M. marinum isolates are usually susceptible to rifampin, ethambutol, clarithromycin, sulfonamides, and trimethoprim-sulfamethoxazole; susceptible or intermediately susceptible to doxycycline and minocycline; intermediately susceptible to streptomycin; and resistant to isoniazid and pyrazinamide.

For treatment of superficial papules due to M. marinum, monotherapy with one of the following regimens is reasonable: clarithromycin (500 mg orally twice daily), minocycline (100 mg orally twice daily), doxycycline (100 mg orally twice daily), or trimethoprim-sulfamethoxazole (one double-strength tablet orally twice daily) [23,28-30].

For treatment of deeper or more extensive infection due to M. marinum, we favor treatment with two active agents. A reasonable regimen consists of clarithromycin (500 mg orally twice daily) combined with either ethambutol (15 mg/kg orally once daily) or rifampin (600 mg orally once daily).

We continue treatment of M. marinum infection for one to two months following resolution of symptoms (total duration is typically three to four months) [26,31]. The rate of clinical response is variable; at least four to six weeks of therapy should be administered before inadequate response should be suspected.

For disease involving the closed spaces of the hand or disease that responds poorly to drug therapy, surgical debridement may be warranted [32,33].

In one series including 63 patients with M. marinum infection, the median duration of antibiotics was 14 weeks (range 1 to 25 months) [34]. Cure was achieved in 87 percent of cases; treatment failure was associated with involvement of deeper structures (but not the antibiotic regimen). A combination regimen was administered in 63 percent of cases (most commonly clarithromycin plus rifampin); among patients treated with monotherapy, the most common regimen was minocycline or doxycycline.

PREVENTING TETANUS — The patient's tetanus immunization status should be reviewed [35]. Tetanus toxoid, diphtheria-tetanus-acellular pertussis, booster tetanus toxoid-reduced diphtheria toxoid-acellular pertussis, or tetanus-diphtheria toxoids adsorbed should be administered as indicated (table 2). The need for tetanus immune globulin should also be assessed (table 2). (See "Tetanus".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Skin and soft tissue infections".)

SUMMARY AND RECOMMENDATIONS

●Risk factors – The risk of soft tissue infection associated with water exposure may be considered in the following hierarchy (from highest to lowest risk) (see 'Epidemiology' above):

•Fresh water (ponds, small lakes)

•Flowing fresh water (rivers, large lakes)

•Brackish water (water that is saltier than fresh water but less salty than sea water, found where bodies of sea water and fresh water meet)

•Sea water

•Well-regulated treated swimming pools, hot tubs

In addition to water, other relevant exposures may include mud, sand, or sewage.

Patients with underlying liver disease and immunosuppression are at increased risk for soft tissue infection associated with water exposure as well as systemic infection. (See 'Epidemiology' above.)

●Types of injuries – Injuries associated with water exposure include lacerations (due to inanimate objects in water), puncture wounds due to fishhooks or spines, and bites from aquatic animals. (See 'History and physical examination' above.)

●Types of infection – These include cellulitis, abscess formation, necrotizing soft tissue processes (eg, fasciitis and myositis), and bone and joint infection. The microbiology, epidemiology, incubation period, and clinical manifestations are summarized in the table (table 1). (See 'Clinical evaluation' above and 'Microbiology' above.)

●Management of uninfected wounds – Components of management of uninfected wounds include local wound care and administration of antibiotic prophylaxis and tetanus prophylaxis, as needed (table 2). (See 'Uninfected wound' above.)

•Wound management – The optimal approach for closure of uninfected wounds associated with water exposure depends on the nature of the exposure, as discussed above (see 'Closure' above). Indications for surgical consultation are summarized above. (See 'Surgical consultation' above.)

•Post-exposure antibiotic prophylaxis – We suggest administering prophylactic antibiotic therapy for patients with wounds associated with water exposure in the following circumstances (Grade 2C) (see 'Antibiotic prophylaxis' above):

-Deep puncture wound or laceration (beyond the dermis)

-Wounds requiring surgical repair

-Wounds undergoing primary closure associated with any water exposure apart from well-regulated treated swimming pools or hot tubs (see 'Epidemiology' above)

-Wound with associated crush injury

-Wound in area of underlying vascular or lymphatic compromise

-Wound on the hands, feet, face, or genital area

-Wound in close proximity to a bone or joint (particularly a prosthetic joint)

-Wounds in immunocompromised patients or those with diabetes or chronic liver disease

●Management of infection wounds – Components of management for infected wounds include surgical consultation for selected patients as described above, debridement of infected tissue, obtaining wound cultures (and blood cultures in patients with signs of systemic infection or immunocompromise), administration of antibiotic therapy, and providing tetanus prophylaxis as indicated. (See 'Infected wound' above.)

●Preferred empiric antibiotic regimen – The following antibiotic regimen may be administered prophylactically for prevention of soft tissue infection following water exposure or empirically for treatment of established soft tissue infection (see 'Antibiotic prophylaxis' above and 'Empiric therapy' above):

•A first-generation cephalosporin (eg, cephalexin 500 mg orally four times daily or cefazolin 1 g intravenously every eight hours)

PLUS

•Levofloxacin (750 mg orally or intravenously once daily)

PLUS (if epidemiologic risk is present)

•Seawater exposure: doxycycline (100 mg orally or intravenously every 12 hours) for coverage of Vibrio species

•Soil-contaminated wound or exposure to sewage-contaminated water: metronidazole (500 mg orally or intravenously every six hours) for anaerobic coverage

●Tailoring antibiotics – General information regarding antimicrobial susceptibility for organisms associated with water exposure is presented in the table (table 1). For most soft tissue infections due to bacteria associated with water exposure, a reasonable duration of therapy is 10 to 14 days. (See 'Bacterial infection' above.)

●Treatment of Mycobacterium marinum infection – Optimal treatment of M. marinum infection is uncertain. For treatment of superficial papules due to M. marinum, we suggest monotherapy (Grade 2C); reasonable regimens include clarithromycin, minocycline, doxycycline, or trimethoprim-sulfamethoxazole. For treatment of deeper or more extensive infection due to M. marinum, we suggest combination therapy with two active agents (Grade 2C); a reasonable regimen consists of clarithromycin combined with ethambutol or rifampin. We continue treatment of M. marinum infection for one to two months following resolution of symptoms (total duration is typically three to four months). For disease involving the closed spaces of the hand or disease that responds poorly to drug therapy, surgical debridement may be warranted. (See 'Mycobacterial infection' above.)