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Outcome of unimicrobial versus polymicrobial sepsis


Polymicrobial sepsis is associated with immunosuppression caused by the predominance of anti-inflammatory mediators and profound loss of lymphocytes through apoptosis, and so deaths directly related to sepsis are twofold higher in polymycrobial sepsis. The aim of study is to compare unimicrobial versus polymicrobial sepsis as regards microbiology, complications, length of stay, mortality, factor affecting mortality.


One hundred and one patients with sepsis were studied and divided into two groups. The first group: unimicrobial, where one organism was isolated from cultures; and the second group: polymicrobial, where more than one organism was isolated from the cultures.


The first group (unimicrobial) was 48 cases (47.5%) and the second group (polymicrobial) was 53 cases (52.47%). Both groups has similar positive sputum cultures (32/48 (66%) versus 38/53 (71%), P value 0.6), but positive blood culture was significantly higher in the second group (27/53 (51%) vs 7/48 (14%), P value 0.0001). There was also a significantly higher incidence of UTI and wound infection in the second group (49.7% vs 6.3% for UTI, P value 0.0001 and 20.7% vs 2.1%, P value 0.004 for wound infection, respectively). The commonest detected organisms were Staphylococci and Klebsiella (48, 22 out of 101 patients); 16/48 (33%) in unimicrobial vs 32/53 (60%) in polymicrobial (P value 0.007) for staph, and 7/48 (14.5%) in unimicrobial vs 15/53 (28%) in polymicrobial for Klebsiella (P value 0.09). Incidence of Acinetobacter, Candida and E. coli in the second group were significantly higher 10/53 in poly vs 2/48 in unimicrobial (P value 0.032), and 10/53 vs 0/48 (P value 0.002 ) and 6/53 vs 0/48 (P value 0.016), respectively. Need for mechanical ventilation in the second group was significantly higher than the first group (46/53 (86%) vs 31/48 (64%), P value 0.009). The mean hospital stay was longer in the second group (26.9 ± 15.4 vs 17.4 ± 9.3, P value 0.001). Mortality was significantly higher in the second group (P value 0.012). Factors increasing mortality in both groups were DCL (P value 0.007 in unimicrobial and 0.036 in polymicrobial); vasopressors (P value 0.001 and 0.002, respectively); mechanical ventilation (P value 0.00 and 0.00, respectively), and severe sepsis and septic shock with significant P value (0.019) and (0.008), respectively, for the first group and (0.003) and (0.002), respectively, for the second group.


Polymicrobial sepsis shows higher risk for complication, length of stay and mortality than unimicrobial.


  1. 1.

    Aliaga , et al.: Eur J Clin Microbiol Infect Dis. 2000, 19: 871-874. 10.1007/s100960000392

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Correspondence to N Abed.

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Abed, N., Hussein, A., Salaheldine, S. et al. Outcome of unimicrobial versus polymicrobial sepsis. Crit Care 14, P62 (2010).

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  • Public Health
  • High Risk
  • Hospital Stay
  • Mechanical Ventilation
  • Septic Shock