Interaction of shockwaves with infected kidney stones: is there a bactericidal effect?
OBJECTIVE
Many calculi contain bacteria, which can remain active inside kidney stones and cause infection after lithotripsy. Reduction in renal infections after extracorporeal shockwave lithotripsy has been observed; however, results are controversial, and no information on the effect of shockwaves on bacteria inside kidney stones has been reported. The purpose of this research was to study whether bacteria inside kidney stones can be inactivated by shockwaves.


METHODS
A series of infected artificial kidney stones were exposed in vitro to either 90 or 400 shockwaves using a research electrohydraulic or a commercial piezoelectric lithotripter. Two types of stones (soft and hard) were manufactured by mixing gypsum cement and Vel-mix-stone with water. Half of the stones were inoculated with Salmonella typhimurium. The suspension containing stone powder and bacteria was inoculated on agar plates and incubated. Bactericidal action was defined as the logarithmic viability reduction.


RESULTS
About 95% of the bacteria were inactivated with 400 shockwaves using the electrohydraulic lithotripter; however, most of the damage was associated with the electromagnetic emission (ultraviolet radiation and visible light) generated at the spark gap. After 2730 shockwaves to stones placed inside a black polypropylene bag, about 29% and 14% of all bacteria were inactivated with the piezoelectric and the electrohydraulic lithotripter, respectively. In this case, the electromagnetic radiation was blocked by the black bag.


CONCLUSIONS
Bacteria inactivation is possible by in vitro shockwave application; however, according to our results, no significant bactericidal effect is expected during extracorporeal shockwave lithotripsy.
Quintero
María Del Sol
Mdel S
Faculty of Sciences , Universidad Nacional Autónoma de México, México D.F., México.
Alvarez
Ulises M
UM
Wacher
Carmen
C
Gutiérrez
Jorge
J
Castaño-Tostado
Eduardo
E
Fernández
Francisco
F
Loske
Achim M
AM
D000704:Analysis of Variance; D001419:Bacteria / Q000166:cytology*; D006801:Humans; D007669:Kidney Calculi / Q000382:microbiology*; D008096:Lithotripsy / Q000379:methods*; D050296:Microbial Viability; D011312:Pressure