History
Urinary tract infections
M morganii commonly is recovered from urine cultures in patients with long-term indwelling urinary catheters.
In a study of 135 consecutive patients with symptomatic, complicated, multidrug-resistant urinary tract infections, nearly 10% were infected with M morganii. The presence of M morganii in catheter-associated urinary tract infections also can decrease the severity of a polymicrobial infection via a proposed mechanism of decreasing urease activity. [8]
Like Proteus species, M morganii has properties that enhance its ability to infect the urinary tract; these include motility and the ability to produce urease.
Urolithiasis is associated with both genera. Members of the tribe Proteeae account for approximately 50% of cases of urolithiasis associated with urinary tract infections in children. M morganii has been increasingly found as a cause of UTI in pediatric populations. [9]
Perinatal infections
M morganii has been associated with perinatal infection. Four cases of chorioamnionitis and 1 case of postpartum endometritis have been reported, and each case involved immunocompetent women. [10, 11]
Three of the patients had received parenteral treatment with ampicillin prior to delivery.
In 2 of the pregnancies, the neonates were not infected.
A third neonate developed early-onset sepsis and M morganii bacteremia. The infant was treated successfully with 10 days of cefotaxime and gentamicin. A fourth neonate, born at 24 weeks' gestation, died within the first 38 hours of life. M morganii was recovered from this neonate's blood, pleural fluid, and peritoneal fluid cultures.
The fifth case occurred in a mother who had repeated exposures to beta-lactam antibiotics in the months prior to delivery for rheumatic fever prophylaxis and pharyngitis and then had intrapartum ampicillin for chorioamnionitis. Her neonate, born at 35 weeks' gestation, was treated empirically with intravenous ampicillin and gentamicin immediately after delivery, but developed respiratory distress and petechial and purpuric skin lesions on the second day of life. A chest radiograph revealed a lobar infiltrate. Blood culture findings were positive for M morganii that was resistant to ampicillin and susceptible to cefotaxime and gentamicin. The infant recovered following a 14-day course of cefotaxime and gentamicin. The infant's mother remained febrile after delivery, with evidence of endometritis and subsequent M morganii urinary tract infection. Her isolate was resistant to ampicillin and gentamicin and was treated successfully with imipenem-cilastatin.
Two cases of early-onset neonatal sepsis in the absence of maternal infection have been reported. Both involved 32-week–premature neonates born to mothers who had received dexamethasone and ampicillin prior to delivery. Both neonates were treated with cefotaxime and amikacin. One neonate's sepsis responded to treatment; the other neonate died from M morganii infection.
Late-onset neonatal infection
Late-onset neonatal infection has been reported in 2 neonates: (1) a neonate born at term who presented on the 11th day of life with fever, irritability, and M morganii bacteremia and (2) a 15-day-old neonate with M morganii meningitis and brain abscess. [12]
Necrotizing fasciitis
Fatal necrotizing fasciitis caused by M morganii and Escherichia coli was reported in a 1-day-old neonate who had been inadvertently dropped into a toilet bowl during a home delivery. [13]
Skeletal infections
Four cases of M morganii septic arthritis have been reported in adults. All presented as chronic indolent infections. In contrast to the aggressive and destructive joint disease associated with Proteus mirabilis septic arthritis, the cases of M morganii arthritis were remarkable for their benign clinical presentations and lack of joint damage despite a prolonged course. [14, 15, 16]
Snakebites
M morganii commonly is found in the mouths of snakes. As a result, it is one of the organisms recovered most often from snakebite infections. Jorge (1994) recovered M morganii from 57% of abscesses occurring at the site of Bothrops (ie, the American Lanceheads) bites. [17]
Scombroid poisoning
M morganii produces the enzyme histidine decarboxylase, which reacts with histidine, a free amino acid present in the muscle of some species of fin fish, including tunas, mahimahi, sardines, and mackerel. When these fish are improperly stored, spoilage from M morganii may cause the decarboxylation of histidine into histamine. Scombroid poisoning, an anaphylacticlike clinical syndrome, is caused by ingestion of the histamine-containing fish. [18, 19]
Infections in people with AIDS
Two case reports of M morganii infection in patients with AIDS exist: a 45-year-old man with meningitis [20] and a 31-year-old man with pyomyositis. [21]
Bacteremia
In a retrospective review of 73 patients with M morganii bacteremia in Taiwan, 70% cases were community acquired and 45% were associated with polymicrobial bacteremia. The most common portals of entry were the urinary tract and hepatobiliary tract. Polymicrobial infection was most commonly associated with hepatobiliary disease. The overall mortality rate was 38%. The most important risk factor for mortality was inappropriate antibiotic therapy. [22]
CNS infections
CNS infections are rare. Six adult cases have been reported, including 3 cases of meningitis and 3 cases of brain abscess. The most common presentation was fever and altered mental status. Two of the patients with meningitis died. Two patients with brain abscess survived, one with long-term neurologic sequelae. [23]
Physical
Physical findings are similar to those of other gram-negative infections.
Ecthyma gangrenosum–like eruptions and hemorrhagic bullae have been associated with M morganii sepsis.
One 15-year-old patient with recurrent episodes of Henoch-Schönlein purpura was found to have a tuboovarian abscess caused by M morganii. Treatment of the infection resulted in complete remission of the vasculitis. [24] Another case demonstrates M morganii bacteremia resulting in purpura fulminans in a 80-year-old male who had undergone a recent urinary tract infection intervention. [4]
Causes
Risk factors for M morganii infection include the following:
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Prior exposure to ampicillin and other beta-lactam antibiotics
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Diabetes mellitus
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Advanced age
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Surgical procedures
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Perinatal exposure
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Abscesses or soft tissue infections following snakebite
