Haemophilus influenzae
H. influenzaetype b is the second most common organism related to OPSI and accounts for 32%
of the mortality. Most cases (86%) occur in children younger than 15 years, but the overall
incidence has decreased due to wide usage of conjugatedH. influenzaetype b vaccine (7).
Neisseria meningitidis
N. meningitidisis cited as the third most common cause of OPSI. Even though there is no
conclusive evidence, many investigators feel that splenectomized patients are at high risk for
fulminant meningococcemia (7).
Capnocytophaga canimorsus
It is a fastidious gram-negative bacillus, previously referred to as CDC group DF-2 (dysgonic
fermentor-2), and part of normal oral flora of dogs and cats. The organism is transmitted to
humans by exposure to an animal, usually via bite or scratch, and can lead to fulminant sepsis
(28). Infection in asplenic or hyposplenic settings can be associated with an eschar at the bite
site and can produce intraleukocytic gram-negative bacilli in the Buffy coat or peripheral blood
smear. The illness tends to manifest one to seven days after animal exposure (29–31).
Other Bacteria
Salmonellaspecies do not play a large role in OPSIs, althoughsalmonellais a prominent
pathogen in children with sickle cell anemia and splenic dysfunction. Non-typhoidSalmonella
species, which normally cause gastroenteritis, may cause disseminated infection in asplenic
patients. Infections with gram-negative bacteria, notably Escherichia coliandPseudomonas
aeruginosa, also occur with increased frequency in splenectomized patients and are often
associated with high mortality.Enterococcusspecies,Bacteroidesspecies,Bartonella,Plesiomonas
shigelloides,Eubacterium plautii, andP. pseudomalleialso are reported. BothSalmonellaand
Bartonellainfection has been linked to reticuloendothelial blockade (32,33).Streptococcus suis,a
zoonotic gram-positive bacteria, has been reported in several cases of bacteremias in asplenic
individuals and is associated with swine exposure (34). Human granulocytic ehrlichiosis may
be more severe, recurrent, with a prolonged course in individuals who are asplenic (35).
NONBACTERIAL PATHOGENS
The splenectomized host also appears to be more susceptible to serious infections with certain
protozoa. Babesiosis caused by anintraerythrocytic protozoan,Babesia microtiin North America
andBabesia bovisin Europe has been reported to cause significant morbidity and mortality in
asplenic hosts. In a review of 22 cases of babesiosis in splenectomized individuals, the infection
was more severe and more likely associated with hemolytic anemia, high-grade and persistent
parasitemia, and in some cases required exchange transfusion (36). In a recent study
splenectomized patients secondary to trauma were twice as likely to have Plasmodium
falciparumparasitemia and it was more likely to be associated with febrile symptoms. Mature
parasites were seen more often in the peripheral blood in asplenic individuals (37).
HIV INFECTION AND SPLENECTOMY
Splenectomy may be required in refractory thrombocytopenia associated with HIV. It is not
clear however, if the risk of postsplenectomy sepsis in the HIV-infected individual is different
from that in the non-HIV-infected person or whether low CD4 cell level contributes to the risk.
Following removal of the spleen, CD4 and CD8 lymphocytes will rise, as it does in a non-HIV–
infected individual (38). Thus the absolute CD4 count may not be helpful in therapeutic
decision making in splenectomized patients, however the CD4 to CD8 ratio remains low and
becomes more relevant to decisions on antiretroviral therapy (39).
OVERWHELMING POSTSPLENECTOMY INFECTIONS
Clinical Presentation
Time to diagnosis and management is a key factor in OPSIs, with 68% of the deaths occurring
within 24 hours and 80% within 48 hours from the initial symptoms (20). OPSIs have a short
prodrome and early consideration is vital to facilitate an aggressive and prompt intervention.
352 Ahmed and Khardori