Trimethoprim-Rifampin, a New Combination Agent: Efficacy

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1 ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, Apr. 1981, p Vol. 19, No /81/4513-6$2./ Trimethoprim-Rifampin, a New Combination Agent: Effiay in Loalized Urinary Infetion and Influene on Miroflora ANNE-MARIE BOURGAULT,t KEVIN R. FORWARD,* ALLAN R. RONALD, GODFREY K. HARDING, MARGARET THOMSON, AND GLORIA GREY University ofmanitoba, Winnipeg, Manitoba, Canada R3E OZ3 Reeived 23 September 198/Aepted 8 January 1981 Twenty women with reurrent or persistent urinary trat infetions were treated with a fixed ombination of trimethoprim-rifampin (TMP-RAM). The site of infetion was established by the antibody-oated bateria test. Sixteen women had upper trat infetions (antibody-oated bateria tests positive); eight were ured, three failed, and five relapsed. All four women with lower trat infetions (antibody-oated bateria tests negative) were ured. Three of five patients with strutural abnormalities failed. The 12 ures and 5 relapses were assoiated with organisms suseptible to either TMP (minimal inhibitory onentration, s8,ug/ml) or RAM (miniimal inhibitory onentration, s32,ug/ml). In ontrast, two of the three failures were assoiated with organisms resistant to both TMP and RAM. In one patient, RAM resistane emerged during treatment. During therapy, urinary strains were eradiated from the periurethral and analanal areas in all but 3 of 16 patients. Adverse reations, noted in 16 women, inluded nausea (1), dizziness (6), headahes (2), rash (1), and blurred vision (1). Antimirobial suseptibility data on 246 isolates from urinary, periurethral, and anal-anal speimens are inluded. Our findings suggest that TMP-RAM is effetive in urinary infetions and may prevent the emergene of RAM-resistant strains. Rifaprim is a fixed ombination of trimethoprim (TMP) and rifampin (RAM). This ombination exerts a variable degree of synergism against different baterial speies and may prevent the appearane of strains resistant to RAM (3, 8-1, 13). TMP-RAM deserves to be studied to determine its effiay in urinary trat infetion (UTI) sine both TMP and RAM have favorable pharmaokinetis within the urinary trat and a broad spetrum of antibaterial ativity (1, 14). In an open unontrolled study we investigated the effiay and tolerane of the TMP-RAM ombination in patients with reurrent UTIs. The objetives of the present study were to determine (i) the effiay of TMP-RAM in diffiult-to-eradiate UTIs, (ii) the effet of TMP-RAM on the periurethral and anal-anal aerobi miroflora during and after therapy, (iii) the range of suseptibility of a number of strains to TMP and RAM and to ombinations of both agents, and (iv) the effet of TMP-RAM on the emergene of bateria resistant to TMP, RAM, or both. MATERIALS AND METHODS Seletion of patients. After written informed onsent was obtained, 2 nonpregnant women with a t Present address: Centre Hospitalier de l'universite Laval, Ste-Foy, Quebe, Canada G1V 4G2. history of reurrent or persistent UTI were enrolled in the study. These women were seleted from a group of patients regularly followed in the UTI lini at the Health Sienes Centre in Winnipeg. Of 16 patients, 14 had persistant bateriuria while on previous antimirobial therapy or relapsed after essation of therapy. Two patients with lower trat infetions had reinfetions. All patients had a doumented urinary infetion as defined by the isolation of 21, olony-forming units per ml of urine from a lean-voided midstream speimen in patients with aute urinary symptoms and by two positive urine ultures for -1, olony-forming units of the same baterial speies per ml in two onseutive speimens in asymptomati individuals. The riteria for exlusion were: presene of an indwelling atheter, treatment with antibaterial agents within the 48 h before ommenement of the experimental treatment, pregnany or breast feeding, previous intolerane to TMP or RAM, serum reatinine of >1.5 mg/1 ml, and abnormalities of liver funtion tests or hematologial parameters. Patient protool. The patients were treated with Rifaprim (TMP, 8 mg; RAM, 3 mg) (Dow Pharmaeutials, Rihmond Hill, Ontario), four tablets daily at bedtime for 14 days. To assess the response to therapy, the patients were monitored weekly during and for 2 weeks after therapy for reations to the mediation. In addition, urinalysis of midstream urine samples, periurethral and anal-anal swabs, hematologial examinations (omplete blood ount, platelet ount), liver funtion tests (bilirubin, serum glutami oxalaeti transaminase, alkaline phosphatase), and 513 Downloaded from on Otober 8, 218 by guest

2 514 BOURGAULT ET AL. kidney funtion tests (blood urea nitrogen, reatinine) were also performed before therapy, weekly during therapy, and for 2 weeks after ompletion of therapy. The antibody-oated bateria (ACB) test as desribed by Thomas et al. (18) and modified by Harding et al. (11) was used to differentiate upper from lower UTI. Definitions. A ure was defined as a negative urine ulture at 2 weeks after ompletion of therapy. A relapse was defined as a reurrene of the same speies of bateria or the same biotype of Esherihia oli within 2 weeks of ompletion of therapy. A reinfetion was defined as the appearane of a new baterial speies or biotype of E. oli during therapy or on follow-up. A failure was defined as the persistene of the pretherapy organism during treatment. Colletion of speimens and mirobiologial tehniques. Quantitative urine ultures were performed by routine methods. Periurethral and analanal speimens were obtained by swabbing the periurethral and anal-anal areas with otton-tipped appliators and blending the appliators in 5 ml of physiologial saline on a Vortex mixer. Quantitative ultures of the suspensions were arried out as previously desribed (16). The aerobi organisms were identified aording to standard laboratory proedures. All the E. oli isolates reovered from the urine, periurethral, and anal-anal speimens were biotyped as previously desribed (6). Minimal inhibitory onentrations (MICs) of RAM (Dow Pharmaeutials, Indianapolis, Ind.) and TMP (Hoffmann-LaRohe, Montreal, Canada) were determined in Wellotest agar (Wellome Researh Laboratories, England) (19) with the use of a Steers repliator (17). Inoula were prepared by subulturing four to five olonies from a blood agar plate into Isosensitest broth (Oxoid, England) and inubating at 35 C for 4 hr. All the organisms were tested with a 1:1 dilution of a broth ulture equivalent in turbidity to a MFarland.5 BaSO4 standard (19) so that approximately 14 olony-forming units were delivered to the agar surfae. The MIC was read as the lowest onentration of antibioti showing no growth, a faint haze, or a single olony at the site of inoulation. Organisms were onsidered suseptible to TMP if they required an MIC of -8 tig/ml and suseptible to RAM if they required an MIC of -32,ug/ml. The effet of the ombination of RAM and TMP on all primary urinary isolates was assessed by a mirotiter hekerboard proedure in Isosensitest broth (19). Conomitant MICs were obtained with eah synergism assay. Eah well ontained.1 ml of the appropriate antibioti solutions and.1 ml of the inoulum for a final onentration of 5 x 15 olonyforming units per ml. The inoula were initially prepared as desribed above for the agar dilution tehnique, and a 1:1 dilution was made. The plates were inubated at 35 C for 18 h. The MIC was read with a viewing box as the lowest onentration of antibioti that ompletely inhibited visible growth. The minimal bateriidal onentrations were determined by subulturing 1-pl portions of the infeted broth from the last turbid well and the next five lear wells on sheep blood agar plates. The plates were inubated for 24 h at 35 C. The bateriidal endpoint was defined as the lowest onentration of antibioti whih on subulture ANTIMICROB. AGENTS CHEMOTHER. yielded no growth. The frational inhibitory onentration (FIC) was alulated by dividing the MIC of the drug in ombination by the MIC of the drug alone. The FIC index was alulated by adding the FICs for both drugs. Synergy was deemed present when the FIC index was.5. Addition was deemed present when the FIC index was >.5 and Indifferene was defined as a onstant MIC of one drug in the presene of various amounts of the alternate drug. Antagonism was deemed present when the FIC index was >1.5. RESULTS Twenty women with a history of diffiult-toeradiate, reurrent, or persistent UTI were studied. Their ages ranged from 17 to 69 years (median, 47 years). Five patients had strutural abnormalities of the urinary trat as demonstrated by an intravenous pyelogram. The details of these abnormalities are summarized in Table 1 together with the results of TMP-RAM treatment, TMP and RAM suseptibilities, and the FIC indies. Sixteen women had upper trat infetion as Seven ACB-posi- established by the ACB test. tive patients were ured, one reinfeted with an E. oli suseptible to both TMP and RAM, five relapsed, and three failed. Of the seven patients who were ured, two were infeted with organisms resistant to TMP, and a third was infeted with an organism resistant to RAM. in the five Similarly, patients who relapsed, all five isolates were suseptible to at least one of the two agents; one isolate was resistant to TMP, and none was resistant to RAM. Organisms persisted during treatment in three patients, two of whom had strutural abnormalities. Eah of the three patients had organisms resistant to TMP, and two of three had organisms resistant to RAM. One of the failures was assoiated with an E. oli strain that required pretreatment MICs of 1,24 jig of TMP per ml and 8,tg of RAM per ml; during treatment, RAM resistane emerged, with the MIC inreasing to 128,ug/ml. Four patients had ACB-negative infetions. All were ured of their original infetion, but one reinfeted with a Staphyloous aureus strain suseptible to both TMP and RAM (TMP MIC,.5,Lg/ml; RAM MIC,.6,ug/ml). The influene of 14 days of therapy with TMP-RAM on the periurethral and anal anal aerobi miroflora was studied. Before treatment, 15 of 19 periurethral and 14 of 18 analanal ultures yielded the urinary isolates. The organisms persisted during therapy in 3 of 16 periurethral and 3 of 16 anal-anal speimens. Two weeks after ompletion of therapy (day 28), only 5 of 15 and 6 of 15 periurethral and anal- Downloaded from on Otober 8, 218 by guest

3 VOL. 19, 1981 TRIMETHOPRIM-RIFAMPIN IN URINARY INFECTION 515 TABLE 1. Bateriologial results on UTI treated with TMP (32 mg) and RAM (1,2 mg) daily for 14 days Loation Patient MIC (pag/mi) of: nt Pathogen of infetion no. pjparxb i FIC index Outome Upper trat 1 Esherihia olid Cure 2 Klebsiella sp.d Cure 3 Klebsiella sp Cure 4 Enterobater Cure loaae 5 E. oli Cure 6 Staphyloous NDe Cure epidermidis 7 Klebsiella sp Cure 8 E. oli Reinfetion 9 Proteus Relapse mirabilis 1 E. oli Relapse 11 E. oli Relapse 12 E. oli Relapse 13 E. oli Relapse 14 Proteus rettgerid Failure Pseudomonas INDf aeruginosa Alaligenes sp Citrobater sp Failure P. aeruginosa' 1,24 >128 IND 16 E. oli 1, Failure Lower trat 17 Streptoous Cure faealis 18 E. olid Cure 19 E. oli Cure 2 P. mirabilis Reinfetion a TMP suseptible: MIC of s8,ug/ml. b RAM suseptible: MIC of <32 ulg/ml. FIC index: the sum of the FICs of both agents. dpatients with abnormal intravenous pyelograms inluded one with bilateral hydronephrosis with ileal onduit (no. 14), one with double right renal olleting system and right kidney sarring (no. 1), one with analgeni nephropathy with papillary alifiation (no. 15), and two with parenhymal sarring (no. 2 and 18). ' ND, Not done. f IND, Indifferent. anal ultures, respetively, yielded the same pretreatment urinary pathogens. Thus TMP- RAM was usually effetive in eradiating the urinary strains olonizing the perineum. The effet of TMP-RAM on total aerobi gram-negative baterial olonization followed a similar pattern (Table 2). Gram-negative baterial arriage dereased during treatment, more notieably in the periurethral than in the anal-anal area. This effet persisted, although to a lesser degree, 2 weeks after ompletion of treatment. There was no emergene of resistane to either TMP or RAM during treatment in the periurethral or anal-anal aerobi miroflora. Sixteen patients noted side effets during treatment with TMP-RAM (TMP, 32 mg; RAM, 1,2 mg). Ten patients omplained of nausea, six omplained of dizziness, and two had TABLE 2. Influene of treatment with TMP-RAM on the periurethral and anal-anal gram-negative Time of sampling aerobi miroftora No. of patients olonized/no. sampleda Periurethral Anal anal Pretreatment 14/17 (14) 16/18 (15) Day 7 1/17 (1) 5/18 (3) Day 14 2/16 (1) 6/16 (3) Day 21 5/13 (2) 9/13 (3) Day 28 8/15 (5) 14/15 (6) a Number of patients olonized with gram-negative bateria/number of patients from whom urinary swabs were obtained. Numbers in parentheses indiate the number of patients olonized with the same pretreatment organism as the one isolated from the leanvoided urine. Downloaded from on Otober 8, 218 by guest

4 516 BOURGAULT ET AL. headahes. One patient developed a rash, and one experiened blurred vision. The side effets subsided rapidly after ompletion of therapy. Redution of the TMP-RAM dosage by half resulted in the disappearane of side effets in one patient. The hematologial and biohemial tests did not detet any evidene of drug-related toxiity. The suseptibility of 246 urinary, periurethral, and anal-anal isolates (representing 16 different baterial strains) to TMP and RAM is summarized in Table 3. Conentrations of 8,ug of TMP and 32,ug of RAM, respetively, per ml inhibited 91% and 95% of the E. oli strains. Five E. oli isolates were resistant to both TMP and RAM, seven were resistant to TMP and suseptible to RAM, and 137 were suseptible to both agents. Thirty-one of 32 isolates (97%) of the Klebsiella-Enterobater group were inhibited by 8 jg of TMP per ml, but only 23 of 32 (71%) were inhibited by 32,ug of RAM per ml. The Proteus sp. isolates tended to be more resistant to TMP, with 23 of 27 isolates requiring MICs of 4 or 8,tg/ml; all were inhibited by 8 ytg of RAM per ml. In ontrast, Pseudomonas aeruginosa strains were uniformly resistant to TMP, and only three of the eight isolates were inhibited by a onentration of 32,ug of RAM per ml Ṫhe FIC indies of the primary urinary isolates are listed in Table 1. Two strains of P. aeruginosa were indifferent. Synergy (FIC,.5) was noted in the following four strains: Proteus rettgeri, Enterobater loaae, Proteus mirabilis, and Streptoous faealis. All the other strains tested were additive. No antagonism was noted. DISCUSSION Kerry et al. (13) first studied in vitro the ombination of TMP and RAM. They demonstrated that both agents ating alone showed good antimirobial ativity and broad spetra against 386 strains of both gram-positive and gram-negative bateria. Furthermore, when tested in ombination, synergism or addition was frequently observed in these strains, and in the presene of subinhibitory levels of TMP, the inidene of RAM-resistant mutants was dereased. Farrell et al. also showed useful synergy at urinary levels in 24 of 26 gram-negative rods resistant to gentamiin (8). Studying 1 urinary pathogens of various speies and suseptibility patterns, Gruneberg and Emmerson (1) showed synergy against 16 strains; antagonism was not seen with any strain. Arioli et al. (3) studied the TMP-RAM ombination in experimental infe- ANTIMICROB. AGENTS CHEMOTHER. tions in mie. They reported that the ombination was more effetive therapeutially and that resistane did not emerge. Thus, suppression by TMP of RAM-resistant mutants is an important feature of the TMP-RAM ombination, perhaps the most relevant one for therapy of UTIs, an infetion in whih inoula may be high and seletion of resistant variants may be ommon (4,9). Previous linial trials of RAM (9 mg daily) in UTI have been disappointing. The suess rate in the report of Atlas and Turk was 24% (4), and half of the treatment failures were assoiated with development of resistane of the initial strains, severely limiting the usefulness of RAM by itself in the treatment of patients with UTI (4). A ontrolled trial of a TMP-RAM ombination and RAM used alone in patients with UTI has shown a signifiant differene in the suess rate after TMP-RAM (TMP at 12 mg and RAM at 45 mg daily for 1 days) ompared with that after RAM alone (9 mg daily for 1 days): 53% of 51 ases versus 24% of 45 ases (15). RAM-resistant strains were isolated after treatment in 27% of 26 patients treated with RAM alone and in 7% of 27 patients treated with TMP-RAM. Another linial trial omparison of TMP-RAM (TMP, 16 mg; RAM, 6 mg) and TMP-sulfamethoxazole (TMP, 16 mg; sulfamethoxazole, 8 mg) in "hroni" UTIs has shown no signifiant differene in ure rates (2). Our study onfirmed the effiay of TMP- RAM in the treatment of urinary infetion in females. This is the only study with TMP-RAM whih has determined the site of infetion. The site of infetion in the urinary trat is an important determinant of suessful treatment, and therefore the evaluation of antimirobial effiay must be judged in patients with doumented infetion of the upper trat. In upper trat infetions, the ombination of TMP-RAM ured 8 of 16 females; these results are equivalent to those observed by Harding and Ronald (12) using TMP-sulfamethoxazole. Those patients studied with upper UTI represented a group in whom more onventional regimens had resulted in either persistene of the infetion or relapse after disontinuation. Furthermore, in those infetions aused by suseptible organisms, relapse with TMP-RAM may have been due to the short duration of therapy rather than the ineffetiveness of the drug ombination. Two of four patients with ACB-negative UTI had previously failed or reurred when treated with antimirobial agents to whih the responsible organism was suseptible. Suh failures are Downloaded from on Otober 8, 218 by guest

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6 518 BOURGAULT ET AL. unusual in unompliated ystitis, and it is probable that the ACB test was false-negative (11). In this trial, resistane did not develop in the organisms suseptible to both TMP and RAM. In one TMP-resistant E. oli strain, RAM resistane emerged on treatment. With our primary urinary strains, the ombination demonstrated only moderate synergy or addition, but in no ase was antagonism observed. It should be noted that these in vitro results are expressed as inhibitory onentrations. The frequent ourrene of "skipped tubes" made determinations of bateriidal endpoints unsatisfatory. Atlas and Turk made similar observations when performing broth dilution tests of suseptibility to RAM alone (4). In synergy studies the FIC index was determined at that ratio of TMP-RAM produing optimal indies. Serum half-lives, urine onentration, and diffusion into vaginal seretions of TMP and RAM differed. Against ertain organisms, most benefiial interations may have ourred at ratios having little relevane to ratios ahieved in serum, urine, or vaginal seretions for at least part of the interval between doses. Alteration of the feal and periurethral flora preedes UTI reinfetion with resistant organisms (2). Therefore an optimal therapeuti regimen should ure the target infetion with little disruption of the baterial suseptibility profile in the periurethral and feal miroflora. Our study demonstrated that TMP-RAM was effetive in eradiating the urinary strains olonizing the periurethra and anal anal. In addition, during the period of observation, TMP- RAM did not predispose to the seletion of RAM- or TMP-resistant strains. The unaeptably high rate of side effets enountered in our patients may be explained by the high dosage of RAM administered (1,2 mg). A lower dosage ould possibly be as effetive and better tolerated. There is a body of opinion that suggests that RAM should be reserved for the therapy of tuberulosis and the eradiation of the Neisseria meningitidis arrier state. However, no evidene exists to suggest that the use of RAM in ombination with TMP for other indiations would inrease the ourrene of RAM-resistant strains of Myobaterium tuberulosis (7). We believe our preliminary data and the evidene aumulating in the European literature justify further linial investigation of the TMP- RAM ombination for treatment of UTI. Controlled studies are required to determine the relative safety and effiay of the ombination as ompared to other urrently available oral antibaterial regimens in well-haraterized renal parenhymal infetions. ANTIMICROB. AGENTS CHEMOTHER. LITERATURE CITED 1. Aoella, G., and R. Sotti Kineti studies on the ombination of rifampiin-trimethoprim in man. J. Antimirob. Chemother. 2: Adahi, T., and T. Ribeiro de Almeida Controlled linial trial of a rifampiin-trimethoprim ombination and otrimoxazole in patients with hroni urinary trat infetions. J. Int. Med. Res. 7: Arioli, V., M. Berti, G. Carniti, and E. Rossi Interation between rifampiin and trimethoprim in vitro and in experimental infetions. J. Antimirob. Chemother. 3: Atlas, E., and M. Turk Laboratory and linial investigation of rifampiin. Am. J. Med. Si. 256: Berenbaum, M. C. A A method for testing synergy with any number of agents. J. Infet. Dis. 137: Bukwold, F. J., A. R. Ronald, G. K. M. Harding, T. J. Marrie, L. Fox, and C. Cates. Biotyping of Esherihia oli by a simple multiple inoulation agar plate tehnique. J. Clin. Mirobiol. 1: Editorial Rifampiin for tuberulosis only? Lanet i: Farrell, W., M. Wilks, and F. A. Drasar The ation of trimethoprim and rifampiin in ombination against gram negative rods resistant to gentamiin. J. Antimirob. Chemother. 3: Goldstein, B. P., I. F. Rifamonti, G. Bolzoni, G. Carniti, and V. Arioli Rifampin plus trimethoprim: bateriidal ativity and suppression of resistane in human urine in vitro. Antimirob. Agents Chemother. 16: Gruneberg, R. N., and A. M. Emmerson The interations between rifampiin and trimethoprim: an in vitro study. J. Antimirob. Chemother. 3: Harding, G. K. M., T. J. Marrie, A. R. Ronald, S. Hoban, and P. Muir Urinary trat infetion loalization in women. J. Am. Med. Asso. 24: Harding, G. K. M., and A. R. Ronald Effiay of trimethoprim-sulfamethoxazole in bateriuria. J. Infet. Dis. 128:S641-S Kerry, D. W., J. M. T. Hamilton-Miller, and W. Brumfitt Trimethoprim and rifampiin: in vitro ativities separately and in ombination. J. Antimirob. Chemother. 1: MCabe, W. B., and V. Laurian Comparison of the antibaterial ativity of rifampiin and other antibiotis. Am. J. Med. Si. 256: Palminteri, R., and D. Sassella Double-blind multienter trial of a rifampiin-trimethoprim ombination and rifampiin alone in urinary trat infetions. Chemotherapy 25: Ronald, A. R., F. A. Jagdis, G. K. M. Harding, S. A. Hoban, P. L. Muir, and M. J. Gurwith Amoxiillin therapy of aute urinary infetions in adults. Antimirob. Agents Chemother. 11: Steers, E., E. F. Foltz, and B. J. Graves An inoula repliating apparatus for routine testing of baterial suseptibility to antibiotis. Antibiot. Chemother. 9: Thomas, V., A. Shelokov, and M. Farland Antibody-oated bateria in the urine and the site of urinary trat infetion. N. Engl. J. Med. 29: Washington, J. A., and A. L. Barry Dilution test proedures, p In E. H. Lennette, E. H. Spaulding, and J. P. Truant (ed), Manual of linial mirobiology, 2nd ed. Amerian Soiety for Mirobiology, Washington, D.C. 2. Winberg, J., T. Bergstrom, K. Linoln, and G. Linden-Jonson Treatment trials in urinary trat infetion with speial referene to the effet of antimirobials on the feal and periurethral flora. Clin. Nephrol. 1: Downloaded from on Otober 8, 218 by guest