Growth of microorganisms in total parenteral nutrition solutions containing lipid

Abstract

Background: To identify the microorganisms that can grow rapidly in total parenteral nutrition (TPN) solutions, we investigated the growth of the major causes of catheter-related blood stream infection (Staphylococcus aureus, Serratia marcescens, Bacillus cereus, and Candida albicans) in TPN solutions containing lipid.

Methods: The pH value of a TPN solution containing lipid (pH 6.0, containing 20 ppm of NaHSO(3)) was adjusted by the addition of HCl to 5.7, 5.4, or 4.9. The pH value of another TPN solution (pH5.5, containing 400 ppm of NaHSO(3)) was adjusted by the addition of NaOH to 5.9, 6.3, or 6.8. A specific number of each microorganism was added to 10 mL of each test solution and incubated at room temperature. The number of microorganisms was counted as colony forming units at 0, 24, and 48 hrs later.

Results: C albicans increased similarly at any pH values in the TPN solution. The bacterial species also increased rapidly at pH6.0 in the solution containing 20 ppm of NaHSO(3), but growth was suppressed as the pH value was reduced, with growth halted at pH4.9. However, these bacterial species did not increase, even at pH5.9, in the other solution containing 400 ppm of NaHSO(3).

Conclusions: These results suggest that Candida species can grow rapidly in almost all TPN solutions regardless of the acidity, lipid, and NaHSO(3); also, some bacterial species may grow in TPN solutions containing lipid unless the pH value is 5.0 or less. Therefore, each TPN solution should be examined whether or not the bacterial species can proliferate.

Keywords: CRBSI; TPN solution; bisulfite; lipid; microbial growth; pH.

Figure 1

Effect of pH on the growth of Staphylococcus aureus in ML (pH6.0; NaHSO₃, 20 ppm). The pH value was adjusted by addition of 0.5 mol/L HCl.

Figure 2

Effect of pH on the growth of Serratia marcescens in ML (pH6.0; NaHSO₃, 20 ppm). The pH value was adjusted by addition of 0.5 mol/L HCl.

Figure 3

Effect of pH on the growth of Bacillus cereus in ML (pH6.0; NaHSO₃, 20 ppm). The pH value was adjusted by addition of 0.5 mol/L HCl.

Figure 4

Effect of pH on the growth of Candida albicans in ML (pH6.0; NaHSO₃, 20 ppm). The pH value was adjusted by addition of 0.5 mol/L HCl.

Figure 5

Growth of Staphylococcus aureus, Serratia marcescens, Bacillus cereus, and Candida albicans at pH6.0 and pH4.9 in ML and in MLV (ML supplemented with multivitamins).

Figure 6

Effect of lipid on the growth of Staphylococcus aureus in AT1V (pH5.5; NaHSO₃, 400 ppm). The pH value was adjusted by addition of 0.5 mol/L NaOH. To AT1V was added 1/10 volume of 20% lipid emulsion (L+AT1V) or physiological saline (S+AT1V).

Figure 7

Effect of lipid on the growth of Serratia marcescens in AT1V (pH5.5; NaHSO₃, 400 ppm). The pH value was adjusted by addition of 0.5 mol/L NaOH. To AT1V was added 1/10 volume of 20% lipid emulsion (L+AT1V) or physiological saline (S+AT1V).

Figure 8

Effect of lipid on the growth of Bacillus cereus in AT1V (pH5.5; NaHSO₃, 400 ppm). The pH value was adjusted by addition of 0.5 mol/L NaOH. To AT1V was added 1/10 volume of 20% lipid emulsion (L+AT1V) or physiological saline (S+AT1V).

Figure 9

Effect of bisulfite concentration on the growth of Staphylococcus aureus in MLV (ML supplemented with multivitamins). The pH value was adjusted by addition of 0.5 mol/L HCl. To MLV was added 100 ppm or 200 ppm of NaHSO₃ (+100ppm or +200ppm).

Figure 10

Effect of bisulfite concentration on the growth of Serratia marcescens in MLV (ML supplemented with multivitamins). The pH value was adjusted by addition of 0.5 mol/L HCl. To MLV was added 100 ppm or 200 ppm of NaHSO₃ (+100ppm or +200ppm).

Figure 11

Effect of bisulfite concentration on the growth of Bacillus cereus in MLV (ML supplemented with multivitamins). The pH value was adjusted by addition of 0.5 mol/L HCl. To MLV was added 100 ppm or 200 ppm of NaHSO₃ (+100ppm or +200ppm).