Spinal Cord Injuries

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1 JOURNAL OF CLINICAL MICROBIOLOGY, OCt 1983, p /83/1844-5$2/ Copyright 1983, American Society for Microbiology Vol 18, No 4 ph and Water Content of Pseudomonas aeruginosa- and Klebsiella pneumoniae-colonized Perineal Skin of Men with Spinal Cord Injuries JOHN Z MONTGOMERIE,12* DONALD G SCHICK,2 DONNA S GILMORE,2 AND IRENE E GRAHAM2 University of Southern California School of Medicine, Los Angeles, California 933,1 and Department of Medicine, Rancho Los Amigos Hospital, Downey, California Received 2 March 1983/Accepted 17 June 1983 Men with spinal cord injuries have a high incidence of Pseudomonas aeruginosa colonization of the perineum Studies were carried out to determine whether colonization with Pseudomonas aeruginosa or Klebsiella pneumoniae is associated with changes in the ph or surface moisture of the perineal skin Increased skin moisture correlated with a higher ph (P < 1) In patients using the external urinary collection system, the ph was significantly higher on the perineum of patients colonized with P aeruginosa or K pneumoniae than on the perineum of patients not colonized with these bacteria There was no correlation between moisture and colonization Colonization with Pseudomonas aeruginosa has been found in a high percentage of men with spinal cord injury Previous studies have shown the perineum to be the most frequent site of colonization, with the same serotype of P aeruginosa persisting in this site for weeks or months (8, 9) The factors influencing the colonization of the skin have not been clear Patients using the external urinary collection system (EUCS) have been most frequently colonized (8, 9) There is some evidence that P aeruginosa is influenced by the presence of moisture on the skin (4) We carried out a study to determine whether the moisture or ph of the skin correlates with the presence of P aeruginosa or Klebsiella pneumoniae in a group of patients with spinal cord injury MATERIALS AND METHODS Patients included in the studies All male inpatients on the spinal cord injury service were included in the study Intermittent catheterization was carried out in these patients until reflex voiding occurred At that time, an EUCS was used by male patients This system consisted of an external condom catheter connected to either a leg bag or a drainage bag on the bed The entire system was changed daily On the same day, cultures of the perineum, skin moisture measurements, and ph measurements were carried out in the morning before the patients were out of bed The patients were studied before they were bathed since bathing may alter ph and moisture of the skin The variation in the skin ph and moisture measurements was examined by repeat duplicate estimations in five patients on 5 consecutive days Patients using the EUCS were selected for this part of the study Patient cultures Cultures of the perineal skin surface were taken with sterile cotton swabs moistened in normal saline The swab was placed in 4 ml of tryptic soy broth (Difco Laboratories, Detroit, Mich) containing 3% cetrimide (J T Baker Chemical Co, Phillipsburg, NJ), incubated for 24 h at 37 C, and transferred onto cetrimide agar (Pseudosel; BBL Microbiology Systems, Cockeysville, Md) A duplicate swab was placed in citrate broth (Koser citrate; Difco), incubated for 24 h, and transferred onto Mac- Conkey and klebsiella isolation agar (3) Identification of P aeruginosa or K pneumoniae was carried out by standard techniques Measurement of skin moisture (i) Sample collection The amount of moisture on the skin surface was determined by taking up the moisture with a dry cotton swab and by using Karl Fischer reagent to detect the amount of water present on the swab (7) Heat-dried cotton swabs were maintained dry in small vials They were prepared by inserting the wooden end of the cotton-tipped applicators through the rubber stoppers of the vial A second set of heat-dried vials were filled with 225 ml of absolute methanol (1% water) and were capped after filling The specimens were collected by using a rotating, rubbing motion with the dry cotton swab over a 2-cm2 area for 15 s The cotton swab tip was broken off and immediately placed into the vial of methanol The vial was then sealed with a rubber stopper and a metal crimper The amount of water in the methanol was measured with the Karl Fischer reagent, a Karl Fischer aquametry probe (Lazar Research Laboratories, Los Angeles, Calif), and a ph meter (SS-3; Beckman Instruments, Inc, Fullerton, Calif) in a hood Samples were introduced into the titration vessel by injection through a rubber diaphragm with a syringe (The Hamilton Co, Reno, Nev) The measurement of water was standardized by adding water to the titration vessel with a syringe Downloaded from on October 22, 218 by guest 844

2 VOL 18, 1983 TABLE 1 Clinical features of the patients Clinical feature No Total no of male patients 4 Colonized with P aeruginosa 17 Colonized with K pneumoniae 2 Colonized with P aeruginosa or K pneumoniae or both 23 No of patients with EUCS 27 Colonized with P aeruginosa 14 Colonized with K pneumoniae 17 No of patients without EUCS 13 Colonized with P aeruginosa 3 Colonized with K pneumoniae 3 (Hamilton) The specimen was titrated with Karl Fischer reagent The titration endpoint was that amount of Karl Fischer reagent which, when added in 5-ml amounts, resulted in a reading equal to a ph of greater than 11 that did not fall below that ph within 3 s of reagent addition Three vials of methanol with dry cotton swabs were titrated to determine the background activity of water in the methanol and cotton swabs The amount of background activity was subtracted from each of the samples (ii) ph measurement The ph of the skin on the perineum was measured with a portable ph meter (Expand-Mate; Beckman) and with a skin probe (flat bulb combination electrode; Beckman) Between the measurement of each patient, the probe was wiped and soaked in 7% ethanol for 5 min (iii) Statistics The ph and moisture measurements of the skin from different groups were compared by Student t test statistics The variation in the ph and moisture measurements was examined by calculating the relative standard deviation (SD), which was calculated by using the formula SD = square root of (xl - x2)12n, where xl and x2 are the duplicate values of ph or moisture, and n is the number of samples (1) The relative SD was calculated as (SD + M) x 1, where M is the mean of all the values RESULTS The clinical features of the 4 patients are shown in Table 1 A higher incidence of P aeruginosa and K pneumoniae infections were seen in patients with the EUCS than in patients without the EUCS Moisture and ph were not measured in three patients who were not available The ph of the perineum ranged from 49 to 82 The ph (mean + SD of the mean) of the perineum in patients colonized with P aeruginosa (647 ± 19) was greater than the mean ph of patients not colonized with P aeruginosa (61 ± 18), but the difference was not statistically significant Similarly, the ph of the perineum of patients colonized with K pneumoniae ( ) was not significantly greater than the ph of ph AND WATER CONTENT OF PERINEAL SKIN 845 patients not colonized with K pneumoniae ( ) P aeruginosa and K pneumoniae colonization and the ph of the perineum in relation to the use of the EUCS is shown in Fig 1A and B In patients using the EUCS, the ph was significantly higher in those colonized with P aeruginosa or K pneumoniae There was no association of colonization with a high ph in patients not using the EUCS The moisture ranged from 45 to 1498,ul/2 cm in 37 patients The relationship of ph and moisture is shown in Fig 2 The regression line has a correlation coefficient of 58 (P < 1) There was no significant association of P aeruginosa or K pneumoniae colonization with moisture The skin moisture (mean ± SD of the mean) of patients with the EUCS (285 ± 59) was not significantly greater than patients not using the EUCS (278 ± 95) The skin moisture in patients colonized with P aeruginosa (315 ± 91) or K pneumoniae (358 ± 85) was not significantly greater than the moisture in patients not colonized with these organisms (247 ± 72) The skin moisture in patients using the EUCS and colonized with P aeruginosa or K pneumoniae or both (321 ± 75) was greater than patients not colonized (159 ± 17), but the differences were not statistically significant The ph and skin moisture measurements of five patients studied for 5 days are shown in Table 2 The relative SD was 43% for duplicate measurements of ph obtained on the same day and 39% for ph measured in the same patient obtained on different days For the moisture measurement, the relative SD was 245% for duplicate samples obtained on the same day and 375% for samples in the same patients obtained on different days In this study, there were significant differences detected in skin moisture between patients In one patient, the ph changed on the day P aeruginosa was acquired, suggesting that P aeruginosa may have produced the ph change DISCUSSION In previous studies we found a high incidence of P aeruginosa colonization in men with spinal cord injury (8, 9) The perineum proved to be the most frequent site of P aeruginosa colonization This colonization was shown to be significantly influenced by the use of the EUCS Others have shown that gram-negative bacilli persist more readily and increase in number in moist, occluded areas on the skin (4) We speculated that the use of the EUCS increased the moisture on the skin and created an environment that increased the risk of P aeruginosa colonization The present studies, however, showed Downloaded from on October 22, 218 by guest

3 846 MONTGOMERIE ET AL A KLEBSIELLA EUCS SIAI EUlCS KLESELLA J CLIN MICROBIOL 8-7O - ph tv B 8 so p<oi EUCS _" L NS EUCS PSEUDOMONAS PSEUDOMONAS PSEULOONAS PSElJDOMONAS Downloaded from 7T ph 6 p< 5 NS 1 4 FIG 1 ph of the perineum and use of EUCS in relation to (A) K pneumoniae and (B) P aeruginosa colonization L on October 22, 218 by guest that there was no significant difference in perineal skin moisture between EUCS users and nonusers On the other hand, we did find that in patients who used the EUCS, colonization with P aeruginosa and K pneumoniae was associated with a high skin ph We are not aware of previous studies of the ph of the perineal skin A number of factors, including the eccrine sweat, lactic acid, and amphoteric amino acids, have been considered to result in the "acid mantle" on the skin (5) The ph of the skin varies in different body sites In exposed areas, the ph varies from 4 to 7 and is usually in the range of 42 to 56 (2) Patients with skin diseases may have significantly higher skin phs The skin of the patients in the present study was grossly normal, and the ph ranged from 48 to 82 Martin-Beare et al

4 VOL 18, ph AND WATER CONTENT OF PERINEAL SKIN ph FIG lo ABSOLUTE H2 (//) Correlation of ph and moisture of the perineum found a higher ph in the inguinal region of children and thought that this might result from contamination by urine and feces (6) Although these patients were not visibly contaminated, frequent contact of urine and feces with the perineal skin may have been a factor resulting in a higher ph It is possible that changes in skin ph may alter the balance of bacteria interacting on the skin or may influence physical factors influencing colonization It would seem unlikely that the increase in the perineal ph was the result of the multiplication of P aeruginosa and K pneumoniae Some support for this possibility was seen in the increase in ph of the perineal skin in a patient the same day as the patient acquired P aeruginosa on the skin Others have suggested that the multiplication of bacteria in sweat may increase the ph of the skin (1) We did not examine the skin for other types of bacteria which may have influenced the skin ph Although we found a significant correlation TABLE 2 ph and skin moisture measurements in five patients obtained on 5 consecutive days Measurementsa obtained on the following consecutive days Parameter and patient no studied Me-an+ SD Perineal moisture content ± ± ± b 118b 24b ± ± 151 Perineal ph 1 NDC ± ± 18 3 ND ± b 56b 53b ± 4 5 ND ± 18 a Average of two measurements obtained at the same time b Colonization negative for P aeruginosa and K pneumoniae C ND, Not done Downloaded from on October 22, 218 by guest

5 848 MONTGOMERIE ET AL between ph and moisture, we did not demonstrate an association between moisture and colonization It is possible that the moisture measurements may have been too variable to demonstrate a correlation between moisture and colonization at a significant level Additional studies will be necessary to determine the exact relationship of colonization to ph and moisture in these patients ACKWLEDGMENTS Support for these studies was supplied by the Weingart Foundation We acknowledge Jean Lloyd for her assistance and secretarial help in the preparation of this manuscript LITERATURE CITED 1 Bergeim, O, and T Cornbleet 1943 The antibacterial action of the lactic acid and volatile fatty acids of sweat Am J Med Sci 25: Blank, I H 1939 Measurement of ph of the skin surface II ph of the exposed surfaces of adults with no apparent skin lesions J Invest Dermatol 2:75-79 J CLIN MICROBIOL 3 Bruce, S K, D G Schick, L Tanaka, E M Jinenez, and J Z Montgomerie 1981 Selective medium for isolation of Klebsiella pneumoniae J Clin Microbiol 13: Marples, R R 1965 The effect of hydration on the bacterial flora of the skin, p 33 In H I Maibach and C Hildick-Smith (ed), Skin bacteria and their role in infection McGraw-Hill Book Co, New York 5 Marples, R R 1965 Climatic conditions on the surface of the skin Hydrogen ion concentration of the surface film, p In Ecology of human skin Charles C Thomas, Springfield, Ill 6 Martin-Beare, J, E A Cheeseman, A A H Galley, and D W Neill 1956 The ph of the skin surface of children with seborrhoeic dermatitis compared with unaffected children Br J Dermatol 7: Mitchell, J, Jr, and D M Smith 1948 Aquametry Interscience Publishers, Inc, New York 8 Montgomerie, J Z, and J W Morrow 1978 Pseudomonas colonization in patients with spinal cord injury Am J Epidemiol 18: Montgomerie, J Z, and J W Morrow 198 Long-term Pseudomonas colonization in spinal cord injury patients Am J Epidemiol 112: Shea, S M 1962 The evaluation of laboratory data, p 15-2 In L B Page and P J Culver (ed), A syllabus of laboratory examination in clinical diagnosis Harvard University Press, Cambridge, Mass Downloaded from on October 22, 218 by guest