Marine infections can lead to cellulitis (redness and swelling), erysipelas (red streaks from infection in the lymph channels) and necrotizing soft tissue infections (bacterial digestion of the tissues). Cellulitis and erysipelas are relatively easy to treat while necrotizing soft tissue infections are difficult and require surgical intervention in most cases.
Infections caused by a mixture of bacteria, some requiring O2 and some not [aerobic and anaerobic] that cause necrotizing wounds can occur from injury, surgery or foreign bodies, and generally affect patients who have some underlying illness such as diabetes mellitus, poor circulation, or are immunosuppressed by medications or AIDS. Infections usually cause local low O2 levels, this being exaggerated in necrotizing infections by an infection-caused blockage of the arteries. The bacteria in necrotizing infections often includes germs that can swing both ways with O2 needs, so to speak, (facultative Gram-negative organisms and endogenous anaerobic bacteria) .
Conditions with low oxygen tension deeply impair white blood cell function, and as local infection develops, the germs use up the O2 and increase the hypoxia (low oxygen). As the infection continues, conditions are also improved for the growth of germs requiring little or no oxygen by the accumulation of metabolic products. This process decreases the tissue oxygen levels even further, accelerating the infectious process and serves to promote the growth of other organisms, getting into a viscious cycle.
Mixed infections produce detectable quantities of tissue gases as the end products of aerobic (oxygen present) and anaerobic (no oxygen) metabolism. Carbon dioxide (CO2) from aerobic infection does not usually accumulate but hydrogen (H2) and methane (CH4) are less soluble and accumulate in the tissues due to incomplete oxidation (metabolizing with oxygen) of tissues. This usually indicates rapid bacterial growth at a low metabolic potential.
Marine infections can be caused by bacteria, mycobacterium, protozoa and viruses.
The main culprit in bacterial infections is the Vibrio vulnificus, causing wound infections in individuals unable to ward off infection due to an underlying chronic disease, usually cirrhosis; or, people who are immuno-suppressed by anti-cancer drugs or AIDS. Wounds that are exposed to seawater or brackish fresh water can show a rapid, progressive cellulitis, necrotizing vasculitis, ulcers, myositis (inflammation muscle tissue) and septicemia (blood-stream infection).
Typically, there is a lacerated hand from cleaning crabs or other shell fish; it starts abruptly, can be associated with diarrhea, has a 50% mortality and may also have DIC [disseminated intravascular clotting] as a part of the symptom complex. Sometimes there are blisters and skin lesions far from the original wound.
Treatment of Vibrio vulnificus includes surgical debridement, supportive measures, and antibiotics, usually tetracycline deriviatives, Chloramphenicol, penicillin and aminoglycosides. X-rays usually fail to show air in the cellulitis.
Vibrio parahaemolyticus is another member of this family that is a gram negative (does not stain with Gram’s dye) halophilic organism (organisms that can live in chemicals called ‘halogens’ ) and is found in warm coastal salt waters. It usually causes a food poisoning scenario with acute onset of explosive watery diarrhea, dysentery and cramping abdominal pain. This is associated with a low grade fever, headache and mild chills. The organism can also cause wound infections, ear infections and septicemia. It is usually self-limited and is associated with positive cultures and fecal leucocytes (white blood cells in the stools).
Erysipelothrix infections can be localized or disseminated. The bacteria, Erysipelothrix rhusiopathiae, is a gram positive rod (a rod-shaped germ that takes up the dye with Gram staining) and occurs in wild, domestic animals, birds and fish. Infection is an occupational disease of fishermen, fish handlers, butchers and people who come in contact with raw seafood or uncooked meat.
Localized infection comes from an abrasion, scratch, or puncture wound while handling material containing the organisms. In the affected fingers and hands there is pain, burning, stiffness of adjacent joints. There is induration (hard swelling) with an irregular violaceous color. The incubation period is 1 to 4 days and the purplish-red swollen area around the site of inoculation spreads peripherally leaving central clearing. There is a slow progression which clears in 3 weeks with appropriate treatment. The disseminated infection (blood-stream) results in endocarditis (inflammation of the lining of the heart) and a red, raised rash. Treatment is with penicillin, clindamycin,or cephalothin. Prevention is accomplished with the use of gloves.
Aeromonas hydrophilia is a Gram negative (does not stain with Gram’s solution) bacteria that lives everywhere in water and soil. Oxidase positive (enzyme aiding in oxidation), it causes cellulitis, osteomyelitis (infection in the bone), acute diarrhea, septicemia [ecthyma gangrenosum], necrotizing myositis and selects compromised hosts such as cirrhotics. The usual setting is a rapidly progressive cellulitis after a water related injury. Leeches carry the aeromonas and this has resulted in stoppage of the use of leeches due to the resultant surgical wound infections.
Treatment of aeromonas infections is with sulfas [Bactrim, Septra], Quinolones [Cipro], Aminoglycosides and 3rd generation cephalosporins [Fortaz].
Mycobacterium marinum is an atypical tuberculosis organism that grows well in enviromental water sources, swimming pools, aquaria, but also in salt water and can be gotten from fish spines and nips by crustaceans. It likes sunlight (photochromogenic) and grows optimally at 32 degrees centigrade, poorly at 37 degrees C. Inoculation is followed by a 2-8 week incubation period after which there is suppuration and organized granulomas (tumorous infections) that can ulcerate. The infection may follow lymphatics and tendon sheaths and appears to infect the superficial cooler body tissues in the extremities.
Treatment of the Mycobacterium is with Ethambutol or Rifampin. Length of treatment is controversial—clinical resolution is accomplished in 4-6 weeks but some feel that treatment should be continued for 18 months.
FREE LIVING AMOEBAS
Free living amoebas can cause interesting diseases such as Naegleria, caused by Acanthamoeba and Pfiesteria piscicida, an unusual organism ordinarily feeding on fish but known to cause human infection characterized by sores, severe memory loss and cognitive (thinking) problems.
Acanthamoeba live in fresh water and can be found in hot tubs and saline solutions. It can cause death from meningitis and keratitis in contact wearers. Divers in fresh water ponds and lakes develop infections in the cribriform plate of the nasal mucosa, acute purulent meningitis and acute hemorrhagic necrotizing encephalitis. Amoebae can be seen on lumbar puncture. Death ensues in 96% of patients, usually children and young adults. Treatment is with Amphotericin B and Hyperbaric oxygen.
Giardia lamblia is a source of gas, watery diarrhea, foul flatus that is contracted from water. It can be diagnosed by stool examination or the string test where the organism is obtained from the duodenum.
Endamoeba histolytica infection is obtained from water, food, fecal-oral and flies. It is treated with Metronidazole.
Hepatitis A [27NM RNA virus] is contracted through the fecal-oral route through food contaminated by feces, soiled hands or sewage-contaminated shellfish. The incubation period is 2-6 weeks, infectivity mostly in the 2-3 weeks in late incubation and the early clinical phase. There is no evidence of a carrier state or chronic hepatitis. There is a flu-like syndrome with mild jaundice. Clinical symptoms and serum transaminases (blood enzymes produced by the liver) return to normal over a period of 3-4 months. Serological changes show IgM antibody early, IgG antibody in convalescence [45% of the US population]. Prevention is with immune serum globulin which is also used for amelioration of the infection.