Factors affecting Staphylococcus epidermidis growth in peritoneal dialysis solutions

Abstract

Staphylococcus epidermidis is the most frequent cause of peritonitis complicating continuous ambulatory peritoneal dialysis. We studied factors that might influence the growth of S. epidermidis in commercially available peritoneal dialysis solution (PDS). Test strains were inoculated into PDS and incubated overnight at 37°C. Samples were removed at appropriate intervals, bacterial counts were performed, and growth curves were constructed. We studied the effects of various osmolarities, the neutralization and acidification of fresh and spent PDS, and the effect of intraperitoneal dwell time on the ability of PDS to support growth of S. epidermidis. In fresh PDS, numbers of bacteria remained constant after 24 h. No significant differences in growth were observed among PDS with 0.5, 1.5, 2.5, and 4.25% glucose. Neutralizing acidic fresh PDS had no effect on bacterial growth. However, growth did occur in spent PDS. PDS which was recovered after only 2 h in the peritoneal cavity supported growth to the same extent as did PDS recovered after 4 to 6 h. Mean logo changes after 24 h of incubation were as follows: for fresh PDS,-1.3; after 2 h dwell time, 2.9; after 4 h dwell time, 1.9; and after 6 h dwell time, 1.3. Acidification of spent PDS to less than pH 6.35 produced less rapid growth; mean lglo increases after 24 h of incubation were 1.9 for pH 7.75, 1.6 for pH 6.35, 0.6 for pH 5.75, and 0.7 for pH 4.95. Fresh PDS of all available osmolarities neither supported the growth of S. epidermidis nor was bactericidal. Spent PDS supported bacterial growth, and this growth was partly independent of the neutralization which occurred during the dialysis.

Bacterial Biofilm Formation on Resorbing Magnesium Implants

“…It was shown in previous studies that S. epidermidis grows best in slightly more acidic pH close to around 6.35 but demonstrates the ability to growth in a range of pHs [30] [31]. In this study S. epidermidis seemed to be resistant to alkali pH due to the effects of magnesium, as revealed by the increase in the bacterial number up to 72 h for all samples tested.…”

Influence of carbon dioxide on growth and antibiotic susceptibility of coagulase-negative staphylococci cultured in human peritoneal dialysate

“…It is well known that isolates from CAPD patients with peritonitis often grow poorly or not at all in the fresh acidic dialysis fluid that is instilled into the peritoneal cavity (11,14). Furthermore, the composition of this fluid changes rapidly during dialysis, and so many workers have instead used PUD as a culture medium (8)(9)(10)(11)(12)(13)(14)16). The pH of PUD quoted in these references ranged from 7.0 to 8.6.…”

“…fluid represents a step closer to these conditions. The peritoneal cavities of patients undergoing continuous ambulatory peritoneal dialysis (CAPD) represent a unique growth environment for potential pathogens, and therefore in vitro studies of peritonitis-causing isolates have employed used peritoneal dialysis fluid (PUD) as a culture medium (8)(9)(10)(11)(12)(13)(14)16). In addition to differences in growth kinetics, we have shown unique phenotypic changes in staphylococcal cell surface characteristics associated with growth in PUD (17,19; S. P. Denyer, M. C. Davies, J.…”

Microbiological aspects of peritonitis associated with continuous ambulatory peritoneal dialysis.

“…The principal pathogens associated with CAPD peritonitis, i.e., Staphylococcus epidermidis, S. aureus, E. coli, and Pseudomonas aeruginosa, have been studied in vitro to determine their growth capabilities and survival in peritoneal dialysis fluids (86,126,145). Verbrugh and colleagues found that staphylococci could not survive in commercially prepared dialysis solutions but grew well in the peritoneal dialysis effluents recovered from patients after the dwell time (postdialysis fluid).…”

“…On the basis of their findings, Sheth et al reasoned that culture-negative cases of peritonitis were probably due to gram-positive cocci, especially coagulase-negative staphylococci, since these organisms may not be readily culturable because of their poor survival in peritoneal fluid (126). The viability of S. epidermidis in commercial dialysis fluids fortified with 0.5 to 4.25% glucose was studied by MacDonald and coworkers (86). They found that fresh dialysis fluid (of all osmolarities tested) neither supported the growth of S. epidermidis nor was bactericidal.…”