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Rhizopus microsporus infection in an immunocompetent host: a case of immunoparalysis?

Fungal infections are among the most feared opportunistic infections in humans. These organisms are ubiquitous in nature; however, many are of low virulence and rarely infect humans. One such fungus is Rhizopus microsporus, a zygomycete found on decaying organic matter, which has previously been reported only in patients who are profoundly immunosupressed. We report a case of R. microsporus infection in an immunocompetent host.

A previously healthy 58-year-old male was admitted to the intensive care unit with septic shock and multi-organ failure. He was commenced on mechanical ventilation, renal replacement therapy and treated with clindamycin, ciprofloxacin and metronidazole. Teicoplanin was commenced following isolation of group G Haemolytic streptococcus. His clinical course was complicated by a vancomycin resistant enterococcus wound infection, a staphylococcal bacteraemia and a bleeding gastric ulcer. However, he was discharged well to a general ward after four weeks and all antibiotics were discontinued.

Shortly thereafter the patient deteriorated, with recurrent sepsis and a large gastrointestinal haemorrhage. He underwent an emergency gastrectomy and splenectomy and was commenced on meropenem, linezolid and fluconazole. Histological examination of sections from the stomach revealed fungal hyphae invading the splenic and gastric vessels (Figure 1), accounting for the sudden gastrointestinal haemorrhage. This was thought to be invasive aspergillosis and fluconazole was replaced with amphotericin-B. Two days later he underwent a further laparotomy, which revealed multiple colonic perforations and faecal peritonitis. Despite surgical resection and multi-organ support, the patient died within 24 hours. Post mortem examination determined the cause of death as gastrointestinal haemorrhage secondary to angio-invasion by fungal hyphae of the gastric, colic and splenic vessels. The fungus was identified as R. microsporus on polymerase chain reaction examination.

R. microsporus is a thermophilic zygomycete and is found in soil, air and decaying organic matter. It is normally a pathogen of low virulence. The nine cases of infection that had been reported previously were all associated with haematological malignancies or prolonged immunosuppressive therapy use1,2. Infection with rhizopus is characterised by tissue infarction and necrosis due to angioinvasive hyphae. The diagnosis is difficult, requiring a high index of clinical suspicion and histological confirmation from a biopsy specimen and/or growth of R. microsporus by polymerase chain reaction. The treatment is amphotericin B, in the highest tolerable dose. Posiconazole has recently been shown to have some activity against zygomyocetes3.

[FIGURE 1 OMITTED]

It is unclear why a previously immune-intact patient succumbed to rhizopus infection. Critically ill patients are at risk for opportunistic fungal infections that are more usually seen in immunocompromised patients (4). This may be explained by the biphasic immunological pattern seen in sepsis: an early hyperinflammatory phase followed by a hypo-inflammatory state known as compensatory anti-inflammatory response syndrome or immunoparalysis--a temporary form of acquired immunodeficiency (5). We postulate that, in our case, a prolonged episode of sepsis resulted in an acquired immunodeficiency and subsequent infection with an environmental pathogen of low virulence. This report highlights the need for physicians to maintain an awareness of the potential of the compensatory anti-inflammatory response syndrome to allow lethal, but often rare, opportunistic infections to develop in the critically ill population.

O. RYAN

S. FROHLICH

T. B. CROTTY

D. RYAN

Dublin, Ireland

References

(1.) Hyvernat H, Dunais B, Burel-Vandenbos F, Guidicelli S, Bernardin G, Gari-Toussaint M. Fatal peritonitis caused by Rhizopus microspores. Med Mycol 2010; 48:1096-1098.

(2.) Monecke S, Hochauf K, Gottschlich B, Ehricht R. A case of peritonitis caused by Rhizopus microspores. Mycoses. 2006; 49:139-142.

(3.) Greenberg RN, Mullane K, van Burik J-AH, Raad I, Abzug MJ, Anstead G et al. Posaconazole as salvage therapy for zygomycosis. Antimicrob Agents Chemother 2006; 50:126-133.

(4.) Hartemink KJ, Paul MA, Spijkstra JJ, Girbes ARJ, Polderman KH. Immunoparalysis as a cause for invasive aspergillosis? Intensive Care Med 2003; 29:2068-2071.

(5.) Bone RC. Sir Isaac Newton, sepsis, SIRS, and CARS. Crit Care Med 1996; 24:1125-1128.
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Article Details
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Title Annotation:Correspondence
Author:Ryan, O.; Frohlich, S.; Crotty, T.B.; Ryan, D.
Publication:Anaesthesia and Intensive Care
Article Type:Case study
Geographic Code:4EUIR
Date:Mar 1, 2012
Words:638
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