The endpoints of the study were infection, bacteremia and/or SBP; incidence of SBP; and death. Antibiotic prophylaxis not only increased the mean survival rate by 9.1%, but also increased the mean percentage of patients free of infection (32% improvement); bacteremia and/or SBP (19% improvement); and SBP (7% improvement).7
Low Ascitic Fluid Protein
Of the three major risk factors for SBP, ascitic fluid protein content is the most debated. Guarner et al studied the risk of first community-acquired SBP in cirrhotics with low ascitic fluid protein.2 Patients were seen immediately after discharge from the hospital and at two- to three-month intervals. Of the 109 hospitalized patients, 23 (21%) developed SBP, nine of which developed SBP during their hospitalization. The one-year cumulative probability of SBP in these patients with low ascitic fluid protein levels was 35%.
During this study, the authors also looked at 20 different patient variables on admission and found that two parameters—high bilirubin (>3.2mg/dL) and low platelet count (<98,000 cells/ul)—were associated with an increased risk of SBP. This is consistent with studies showing that patients with higher Model for End-Stage Liver Disease (MELD) or Child-Pugh scores, indicating more severe liver disease, are at increased risk for SBP. This likely is the reason SBP prophylaxis is recommended for patients with an elevated bilirubin, and higher Child-Pugh scores, by the American Association for the Study of Liver Disease (see Table 2, p. 41).
Runyon et al showed that 15% of patients with low ascitic fluid protein developed SBP during their hospitalization, as compared with 2% of patients with ascitic fluid levels greater than 1 g/dl.8 A randomized, non-placebo-controlled trial by Navasa et al evaluating 70 cirrhotic patients with low ascitic ascitic protein levels showed a lower probability of developing SBP in the group placed on SBP prophylaxis with norfloxacin (5% vs. 31%).9 Six-month mortality rate was also lower (19% vs. 36%).
In contrast to the previous studies, Grothe et al found that the presence of SBP was not related to ascitic protein content.10 Given conflicting studies, controversy still remains on whether patients with low ascitic protein should receive long-term prophylactic antibiotics.
Antibiotic Drawbacks
The consensus in the literature is that patients with ascites who are admitted with a GI bleed, or those with a history of SBP, should be placed on SBP prophylaxis. However, patients placed on long-term antibiotics are at risk for developing bacterial resistance. Bacterial resistance in cultures taken from cirrhotic patients with SBP has increased over the last decade, particularly in gram-negative bacteria.5 Patients who receive antibiotics in the pre-transplant setting also are at risk for post-transplant fungal infections.
Additionally, the antibiotic of choice for SBP prophylaxis is typically a fluoroquinolone, which can be expensive. However, numerous studies have shown that the cost of initiating prophylactic therapy for SBP in patients with a prior episode of SBP can be cheaper than treating SBP after diagnosis.2
Back to the Case
Our patient’s paracentesis was negative for SBP. Additionally, he does not have a history of SBP, nor does he have an active GI bleed. His only possible indication for SBP prophylaxis is low ascitic protein concentration. His electrolytes were all within normal limits. Additionally, total bilirubin was only slightly elevated at 2.3 mg/dL.
Based on the American Association for the Study of Liver Diseases guidelines, the patient was not started on SBP prophylaxis. Additionally, given his history of medication noncompliance, there is concern that he might not take the antibiotics as prescribed, thus leading to the development of bacterial resistance and more serious infections in the future.