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This study investigates the effects, conversions, and resistance induction, following the addition of 150 μg·L -1 of two antibiotics, sulfamethoxazole (SMX) and trimethoprim (TMP), in a laboratory-scale micro-aerated anaerobic membrane bioreactor (MA-AnMBR). TMP and SMX were removed at 97 and 86%, indicating that micro-aeration did not hamper their removal. These antibiotics only affected the pH and biogas composition of the process, with a significant change in pH from 7.8 to 7.5, and a decrease in biogas methane content from 84 to 78%. TMP was rapidly adsorbed onto the sludge and subsequently degraded during the long solids retention time of 27 days. SMX adsorption was minimal, but the applied hydraulic retention time of 2.6 days was sufficiently long to biodegrade SMX. The levels of three antibiotic-resistant genes (ARGs) (sul1, sul2, and dfrA1) and one mobile genetic element biomarker (intI1) were analyzed by qPCR. Additions of the antibiotics increased the relative abundances of all ARGs and intI1 in the MA-AnMBR sludge, with the sul2 gene folding 15 times after 310 days of operation. The MA-AnMBR was able to reduce the concentration of antibiotic-resistant bacteria (ARB) in the permeate by 3 log.

Trimethoprim and sulfamethoxazole are used commonly together as cotrimoxazole for the treatment of urinary tract and other infections. The evolution of resistance to these and other antibacterials threatens therapeutic options for clinicians. We generated and analysed a chemical-biology-whole-genome data set to predict new targets for antibacterial combinations with trimethoprim and sulfamethoxazole. For this we used a large transposon mutant library in Escherichia coli BW25113 where an outward-transcribing inducible promoter was engineered into one end of the transposon. This approach allows regulated expression of adjacent genes in addition to gene inactivation at transposon insertion sites, a methodology that has been called TraDIS- Xpress . These chemical genomic data sets identified mechanisms for both reduced and increased susceptibility to trimethoprim and sulfamethoxazole. The data identified that over-expression of FolA reduced trimethoprim susceptibility, a known mechanism for reduced susceptibility. In addition, transposon insertions into the genes tdk , deoR , ybbC , hha , ldcA , wbbK and waaS increased susceptibility to trimethoprim and likewise for rsmH , fadR , ddlB , nlpI and prc with sulfamethoxazole, while insertions in ispD , uspC , minC , minD , yebK , truD and umpG increased susceptibility to both these antibiotics. Two of these genes' products, Tdk and IspD, are inhibited by AZT and fosmidomycin respectively, antibiotics that are known to synergise with trimethoprim. Thus, the data identified two known targets and several new target candidates for the development of co-drugs that synergise with trimethoprim, sulfamethoxazole or cotrimoxazole. We demonstrate that the TraDIS- Xpress technology can be used to generate information-rich chemical-genomic data sets that can be used for antibacterial development.

Objectives: Trimethoprim/sulfamethoxazole (SXT) is used to treat Staphylococcus aureus infections. However, the effect of treatment with SXT is sometimes not sufficient and there are patients whose treatment has to be prolonged. There are few reports of isolated strains of SXT-resistant S. aureus, but it is possible that some resistant strains cannot be detected by current testing methods We have therefore developed a tool to identify these resistant strains., Methods: The mutant selection window (MSW) of SXT for 40 clinical isolates of S. aureus, including 20 methicillin-resistant S. aureus (MRSA), was determined. The optimum concentration of SXT and thymidine in agar for detecting SXT-resistant small colony variants (SCVs) of S. aureus was investigated., Results: The MSW 50 and MSW 90 of SXT, presented as a multiple of the minimum inhibitory concentration (MIC), were 16× MIC and >256× MIC, respectively. SCVs were detected within the MSW in 32 (80%) of the 40 clinical isolates studied. To maintain the morphology of SCVs, the most suitable concentrations of SXT and thymidine for screening were 4mg/L and 0.01μg/mL, respectively. All 32 SCVs were resistant to SXT (MIC >32mg/L). The sensitivity and specificity of this screening method was 100% and 88.9%, respectively., Conclusions: SXT-resistant SCVs are not usually detected by routine laboratory tests performed in hospitals. However, the screening test described here can easily distinguish SXT-resistant SCVs among S. aureus isolated from specimens. This newly developed screening test could become an important tool to prevent inappropriate use of SXT., (Copyright © 2018 International Society for Chemotherapy of Infection and Cancer. Published by Elsevier Ltd. All rights reserved.)

In a study of 39 isolates of Edwardsiella piscicida made from Korean aquaculture sites, sul genes were detected in 16 isolates and dfr genes in 19. Ten isolates were shown to contain both sul and dfr genes. MIC and disc diffusion zones assays were performed to measure the phenotypic susceptibilities of the 39 isolates. Normalized resistance interpretation was applied to these data to categorize isolates as either fully susceptible or as manifesting reduced susceptibility. The standard CLSI protocols specify the use of a mixture of sulfamethoxazole/trimethoprim (20:1) in both MIC and disc diffusion tests. Using the CLSI MIC protocol, 100% of the isolates containing dfr genes, but only 75% of the isolates containing sul genes, were categorized as manifesting reduced susceptibility. Using the CLSI disc diffusion protocol, only 58% of the isolates containing dfr genes and 69% of those containing sul genes were categorized as manifesting reduced susceptibility. When the single agent trimethoprim was substituted for the combined mixture in both the MIC and disc diffusion protocols, 100% of the dfr-positive isolates were categorized as NWT. When the single-agent sulfamethoxazole was substituted, the analysis of the MIC characterized 100% and the disc zone data 94% of the sul-positive isolates as manifesting reduced susceptibility. It is argued that the use of trimethoprim and sulfamethoxazole as single agents in phenotypic susceptibility tests would provide more meaningful data than the currently recommended use of these two agents combined.

The response of the antimicrobial compounds sulfamethoxazole (SMX) and trimethoprim (TMP) - individually and in mixtures - to ionizing radiation was investigated using laboratory prepared mixtures and a commercial pharmaceutical formulation. The residual antibacterial activity of the solutions was monitored using Staphylococcus aureus and Escherichia coli test strains. Based on antibacterial activity, SMX was more susceptible to ionizing radiation as compared to TMP. The antibacterial activity of SMX and TMP was completely eliminated at 0.2 kGy and 0.8 kGy, respectively. However, when SMX and TMP were in a mixture, the dose required to eliminate the antibacterial activity was 10 kGy, implying a synergistic antibacterial activity when these are present in mixtures. Only when the antibiotic concentration was below the Minimum Inhibitory Concentration of TMP (i.e., 2 µmol dm -3 ) did the antibacterial activity of the SMX and TMP mixture disappear. These results imply that the synergistic antimicrobial activity of antimicrobial compounds in pharmaceutical waste streams is a strong possibility. Therefore, antimicrobial activity assays should be included when evaluating the use of ionizing radiation technology for the remediation of pharmaceutical or municipal waste streams.

Acinetobacter baumannii is emerging as a multidrug-resistant nosocomial pathogen of increasing threat to human health worldwide. Pili are important bacterial virulence factors, playing a role in attachment to host cells and biofilm formation. The Csu pilus, which is assembled via the chaperone-usher secretion system, has been studied in A. baumannii ATCC 19606. Here we show that, in opposition to previous reports, the common laboratory strain ATCC 17978 produces Csu pili. We found that, although ATCC 17978 was resistant to sulfamethoxazole (Smx) and trimethoprim (Tmp), subinhibitory concentrations of these antibiotics abolished the expression of Csu and consequently produced a dramatic reduction in biofilm formation by ATCC 17978. Smx and Tmp acted synergistically to inhibit the enzymatic systems involved in the bacterial synthesis of tetrahydrofolate (THF), which is required for the synthesis of nucleotides. The effects of these antibiotics were partially relieved by exogenous THF addition, indicating that Smx and Tmp turn off Csu assembly by inducing folate stress. We propose that, for Acinetobacter , nanomolar concentrations of Smx and Tmp represent a "danger signal." In response to this signal, Csu expression is repressed, allowing biofilm dispersal and escape from potentially inhibitory concentrations of antibiotics. The roles of antibiotics as signaling molecules are being increasingly acknowledged, with clear implications for both the treatment of bacterial diseases and the understanding of complex microbial interactions in the environment., (Copyright © 2017 American Society for Microbiology.)

Purpose: Stenotrophomonas maltophilia is a multidrug-resistant opportunistic pathogen causing an increasing number of nosocomial infections. Our aim was to evaluate the risk factors and mechanisms associated with trimethoprim-sulfamethoxazole (SXT) resistance in S. maltophilia infections in Mexico., Methodology: Clinical isolates and patients' demographic and clinical data were collected from February 2007 to August 2015 in two tertiary-care hospitals in Mexico. Antimicrobial susceptibility and analysis of sul and SmeABC and SmeDEF efflux pump overexpression were performed in all isolates.Results/Key findings. In the 9-year period, 196 patients infected with S. maltophilia were identified. Most patients were male, and the mean age was 46.2 years. The mean Charlson score was 1.42, and the most frequent comorbidities were arterial hypertension (26.7 %), type 2 diabetes (21.2 %) and cerebral infarction (11.6 %). High drug resistance to meropenem (93.4 %), gentamicin (55.1 %), ceftazidime (52.3 %), cefotaxime (51.5 %), amikacin (42.3 %) and cefepime (32.1 %), and lower resistance to ciprofloxacin (26.0 %), SXT (25.0 %), chloramphenicol (14.3 %) and levofloxacin (2.6 %) were detected. SXT resistance was not associated with the sul genes. SmeABC overexpression was associated with gentamicin (P=0.001) and levofloxacin resistance (P=0.041), whereas SmeDEF overexpression was associated with ceftazidime resistance (P=0.003). Prolonged hospitalization (≥15 days) was an independent risk factor for SXT-resistant S. maltophilia infections (OR=3.05; 95 % CI=1.12-8.86; P=0.029)., Conclusion: Given the high SXT resistance rate, SXT is not an effective first-line therapy for our patients; instead, levofloxacin could be used as an appropriate therapeutic option against S. maltophilia infections.

The combination of trimethoprim (TMP) and sulfamethoxazole (SMX) has been shown to be active against Mycobacterium tuberculosis (Mtb) in clinical tuberculosis (TB) treatment. However, the mechanism of action of TMP-SMX against Mtb is still unknown. To unravel this, we have studied the effect of TMP and SMX by deleting the folP2 gene in Mycobacterium smegmatis (Msm), and overexpressing the Mtb and Msm folP1/2 genes in Msm. Knocking out of the folP2 gene in Msm reduced the minimum inhibitory concentration of SMX 8-fold compared with wild type. Overexpression of the folP1 genes from Mtb and Msm increased the MICs by 4- and 2-fold in Msm for SMX and TMP, respectively. We show a strong correlation between the expression of folP1 and folP2 genes and TMP-SMX resistance in mycobacteria. This suggests that a combination of FolP2 inhibitor and SMX could be used for TB treatment with a better outcome.

Objectives: Sulfamethoxazole/trimethoprim is standard therapy for infections caused by opportunist non-fermenters except Pseudomonas aeruginosa and Acinetobacter. Sulfametrol(e)/trimethoprim is an alternative to sulfamethoxazole/trimethoprim available in some EU countries, with possible pharmacological advantages. We compared their activities against (i) non-fermenters, (ii) multiresistant Enterobacteriaceae and (iii) reference strains with sul1 and sul2., Methods: Test isolates were recent submissions to the reference laboratory, or were Escherichia coli previously shown to have sul1 or sul2. Identification was by MALDI-ToF, by 16S rRNA gene sequencing or with API20NE strips. MICs were determined by CLSI agar dilution. The Stenotrophomonas maltophilia and Burkholderia series were enhanced by inclusion of 25% sulfamethoxazole/trimethoprim-resistant isolates; other series were not enhanced., Results: MICs of sulfametrole/trimethoprim for non-fermenters tracked those of sulfamethoxazole/trimethoprim, being equal in 97/170 cases, 2-fold higher in 57/170 cases and 2-fold lower in 12/170 cases. Despite supplementing the Burkholderia and S. maltophilia collections with sulfamethoxazole/trimethoprim-resistant organisms, the antifolate combinations retained better activity against these and other non-fermenters than did piperacillin/tazobactam, moxifloxacin, ticarcillin/clavulanate, tigecycline, cefotaxime or imipenem. By contrast, few (5%-20%) of the extended-spectrum β-lactamase (ESBL)- and carbapenemase-producing Enterobacteriaceae were susceptible to the sulphonamides or their trimethoprim combinations, probably reflecting widespread co-carriage of sul1 and sul2, which both conferred resistance., Conclusions: Antifolate combinations remain the most active antimicrobials against less common non-fermenters, importantly including S. maltophilia and Burkholderia spp., but resistance is prevalent among ESBL- and carbapenemase-producing Enterobacteriaceae. Sulfametrole/trimethoprim had similar activity to sulfamethoxazole/trimethoprim against non-fermenters.

Objectives: To investigate the effect of trimethoprim/sulfamethoxazole on the survival of Mycobacterium tuberculosis and trimethoprim and sulfamethoxazole individually and combined with the first-line tuberculosis drugs (isoniazid, rifampicin and ethambutol)., Methods: M. tuberculosis strains were exposed to either trimethoprim/sulfamethoxazole combination or sulfamethoxazole and trimethoprim alone at various concentrations. The strains were also exposed to sulfamethoxazole in combination with existing antibiotics to assess the combined effect on the growth of M. tuberculosis in the BACTEC 460TB system. The effect of the drugs was compared with vehicle-treated controls. Drug interactions were interpreted using quotient values obtained from the growth index of cultures treated with a single drug or the combination., Results: Trimethoprim showed a negligible effect on the growth of M. tuberculosis while sulfamethoxazole inhibited 80% of the growth of M. tuberculosis at 4.75 mg/L. There was no synergistic activity between sulfamethoxazole and trimethoprim, although an additive effect was observed. A statistically significant synergistic effect was observed between sulfamethoxazole and rifampicin. Sulfamethoxazole also had an additive effect with ethambutol, but there was no interaction with isoniazid., Conclusions: Sulfamethoxazole is the main active compound against M. tuberculosis in the combination trimethoprim/sulfamethoxazole and has a synergistic effect with rifampicin. These findings suggest that sulfamethoxazole has potential in the multidrug regimen against M. tuberculosis.

The challenges of developing new drugs to treat tuberculosis (TB) are indicated by the relatively small number of candidates entering clinical trials in the past decade. To overcome these issues, we reexamined two FDA-approved antibacterial drugs, sulfamethoxazole (SMX) and trimethoprim (TMP), for use in TB treatment. SMX and TMP inhibit folic acid biosynthesis and are used in combination to treat infections of the respiratory, urinary, and gastrointestinal tracts. The MICs of SMX and TMP, alone and in combination, were determined for drug-susceptible, multidrug-resistant (MDR), and extensively drug-resistant Mycobacterium tuberculosis strains. While TMP alone was not effective against M. tuberculosis, the combination of TMP and SMX was bacteriostatic against M. tuberculosis. Surprisingly, the combination of SMX and TMP was also active against a subset of MDR M. tuberculosis strains. Treatment of M. tuberculosis with TMP-SMX and a first-line anti-TB drug, either isoniazid or rifampin, was bactericidal, demonstrating that the combination of TMP and SMX with isoniazid or rifampin was not antagonistic. Moreover, the addition of SMX-TMP in combination with either isoniazid or rifampin also prevented the emergence of drug resistance in vitro. In conclusion, this study further illustrates the opportunity to reevaluate the activity of TMP-SMX in vivo to prevent the emergence of drug-resistant M. tuberculosis.

Objectives: This study was designed to determine the susceptibility of clinical isolates of multidrug-resistant (MDR) and non-MDR Mycobacterium tuberculosis to sulfamethoxazole, trimethoprim and trimethoprim/sulfamethoxazole over a 12 year period in Taiwan., Patients and Methods: We examined a total of 117 clinical isolates of M. tuberculosis collected from Southern Taiwan, 116 from 1995 to 2006 and an extensively drug-resistant (XDR) isolate in 2009. These included 28 isolates susceptible to all four first-line agents, 52 MDR isolates and 36 isolates with a mixed combination of drug resistance patterns other than MDR and 1 XDR isolate., Results: Sulfamethoxazole inhibited 80% growth of all 117 isolates regardless of their susceptibility to the first-line agents at an MIC(90) of 9.5 mg/L. The concentration required to inhibit 99% growth was 38 mg/L. There were no significant changes in the MIC(50) or MIC(90) of sulfamethoxazole over a 12 year period. All 117 isolates were resistant to trimethoprim at >8 mg/L. The combination of trimethoprim/sulfamethoxazole at a ratio of 1:19 had no additive or synergistic effects., Conclusions: Sulfamethoxazole inhibited the growth of clinical isolates of M. tuberculosis at achievable concentrations in plasma after oral administration. Susceptibility to sulfamethoxazole remained constant over a 12 year period. Trimethoprim was inactive against M. tuberculosis and trimethoprim/sulfamethoxazole provided no additional activity. Although the current and prior studies demonstrate that sulfamethoxazole is active against M. tuberculosis the search needs to continue for more active, lipid-soluble sulphonamides that are better absorbed into tissues and have improved therapeutic efficacy.

This study evaluated the in vitro effect of sulfamethoxazole-trimethoprim against Histoplasma capsulatum var. capsulatum isolated from HIV-positive patients. The drugs were tested by microdilution testing in accordance with the CLSI guidelines. All of the strains were inhibited by sulfamethoxazole-trimethoprim, with MIC ranges of 0.039 (sulfamethoxazole)/0.0078 (trimethoprim) mg/ml to 0.625/0.125 mg/ml for mycelial forms and 0.0025/0.0005 to 0.02/0.004 mg/ml for yeast-like forms. However, in vivo studies are necessary to evaluate the significance of these results.

Aims: To compare the distribution of integrons and trimethoprim-sulfamethoxazole resistance genes among Escherichia coli isolates from humans and food-producing animals., Methods and Results: A collection of 174 multidrug-resistant E. coli isolates obtained from faecal samples of food-producing animals (n = 64) and humans (n = 59), and patients with urinary tract infections (n = 51) in Hong Kong during 2002-2004 were studied. The strains were analysed for their phylogenetic groups, the presence of sul genes (sul1 and sul2), integrons (intl1 and intl2) and class 1 integron-associated dfr cassette genes by PCR, restriction enzyme analysis and sequencing. Integrons were identified in 110 (63.2%) isolates. The prevalence of integrons was significantly different according to the specimen sources (animal faecal 84.4%, human faecal 67.8% and human urinary 31.4%) and phylogenetic groups (B1 80.8%, A 77.6%, D 54.1% and B2 11.5%). Faecal isolates (both human and animal) are more likely to belong to group A and B1. In contrast, most urinary isolates were either groups B2 and D. Among dfr containing isolates, dfrA1 and dfrA12 were almost exclusively found in strains of phylogenetic groups A and B1; and were present in animal and human faecal isolates. In contrast, dfrA17 was found in both faecal and urinary isolates and comprised strains from all phylogenetic groups. The sul1 and sul2 genes were equally prevalent among the isolates irrespective of the specimen source and phylogenetic group status. Pulsed-field gel electrophoresis analysis of isolates with identical cassette genes showed that they were genetically diverse., Conclusions: More animal faecal isolates carry class 1 integrons than human faecal and human urinary isolates, and the distribution of phylogenetic groups is common across animal and human faecal isolates but different from human urinary isolates., Significance and Impact of the Study: Commensal isolates from food-producing animals are an important reservoir for integrons carrying antibiotic resistance genes.

To evaluate the inhibitory effects of trimethoprim and sulfamethoxazole on cytochrome P450 (P450) isoforms, selective marker reactions for CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4 were examined in human liver microsomes and recombinant CYP2C8 and CYP2C9. The in vivo drug interactions of trimethoprim and sulfamethoxazole were predicted in vitro using [I]/([I] + K(i)) values. With concentrations ranging from 5 to 100 microM, trimethoprim exhibited a selective inhibitory effect on CYP2C8-mediated paclitaxel 6alpha-hydroxylation in human liver microsomes and recombinant CYP2C8, with apparent IC(50) (K(i)) values of 54 microM (32 microM) and 75 microM, respectively. With concentrations ranging from 50 to 500 microM, sulfamethoxazole was a selective inhibitor of CYP2C9-mediated tolbutamide hydroxylation in human liver microsomes and recombinant CYP2C9, with apparent IC(50) (K(i)) values of 544 microM (271 microM) and 456 microM, respectively. With concentrations higher than 100 microM trimethoprim and 500 microM sulfamethoxazole, both drugs lost their selectivity for the P450 isoforms. Based on estimated total hepatic concentrations (or free plasma concentrations) of the drugs and the scaling model, one would expect in vivo in humans 80% (26%) and 13% (24%) inhibition of the metabolic clearance of CYP2C8 and CYP2C9 substrates by trimethoprim and sulfamethoxazole, respectively. In conclusion, trimethoprim and sulfamethoxazole can be used as selective inhibitors of CYP2C8 and CYP2C9 in in vitro studies. In humans, trimethoprim and sulfamethoxazole may inhibit the activities of CYP2C8 and CYP2C9, respectively.

Resistance among uropathogenic Escherichia coli to trimethoprim-sulfamethoxazole (TMP-SMX) has increased. Risk factors for resistance and the impact on clinical failure have been poorly described. We performed a retrospective cohort study of women with acute uncomplicated cystitis seen at a university health center and at primary care clinics in southeastern Michigan from 1992 to 1999. The prevalence of TMP-SMX resistance increased from 8.1% to 15.8% (P=.01). Women who had taken TMP-SMX recently were >16 times as likely as women who had not taken antibiotics recently to be infected with an isolate resistant to this agent; those who had taken any other antibiotic were more than twice as likely to be infected with a resistant isolate. Women infected with a TMP-SMX-resistant isolate who were treated with TMP-SMX were >17 times as likely to have treatment failure. Recent antibiotic use is a risk factor for infection with a TMP-SMX-resistant isolate; patients who are infected with a TMP-SMX-resistant isolate and who are treated with this agent are at a higher risk for clinical failure.

Two-dimensional electrophoresis was applied to the global analysis of the cellular response of Haemophilus influenzae to sulfamethoxazole and trimethoprim, both inhibitors of tetrahydrofolate synthesis. Deregulation of the synthesis rate of 118 proteins, involved in different metabolic pathways, was observed. The regulation of the genes involved in the metabolism of the amino acids methionine, threonine, serine, glycine, and aspartate was investigated in detail by analysis of protein synthesis and Northern hybridization. The results suggested that the synthesis of methionine biosynthetic enzymes in H. influenzae is regulated in a similar fashion as in Escherichia coli. A good correlation between the results obtained by Northern hybridization and quantification of protein synthesis was observed. In contrast to trimethoprim, sulfamethoxazole triggered the increased synthesis of the heat shock proteins DnaK, GroEL, and GroES.

A new culture medium has been developed to evaluate the activity of trimethoprim and sulfamethoxazole against Borrelia burgdorferi in vitro. In this specially modified Barbour-Stoenner-Kelly medium, in which antagonizing substances were reduced to a minimum, trimethoprim was more active against Borrelia burgdorferi than against a sensitive strain of Escherichia coli, but sulfamethoxazole was not active against Borrelia burgdorferi.

The photochemical reactions in vitro of sulfamethoxazole alone and in combination with trimethoprim were studied to obtain information on the photosensitization mechanism. Sulfamethoxazole in aqueous solution, on exposure to UVB radiation, generates free radicals and singlet oxygen, with the neutral molecule being at least twice as active as the sulfamethoxazole anion. Photoexcited sulfamethoxazole can participate in electron transfer to cytochrome-c and nitro blue tetrazolium, and sensitizes the peroxidation of linoleic acid and the hemolysis of human erythrocytes, predominantly by a free radical mechanism. Trimethoprim is relatively inactive in the same photochemical systems.

Leishmaniasis is one of the important tropical diseases in the world. Although it is not prevalent in Korea, imported cases have been recorded. The karyotype of Leishmania sp. has been observed to be variable by localities or by strains, but the karyotype of a strain is known to be stable. This study was performed to observe if the karyotype of a Leishmania sp. would be changed under some stressful conditions. The karyotype, analyzed by pulsed field gradient gel electrophoresis, was not grossly changed by heat shock, chemotherapeutics, UV illumination, and gamma irradiation. Radiation destroyed the chromosomes mechanically, but subcultured organisms after irradiation showed unaffected karyotype. The present findings suggest that the karyotype of a Leishmania strain is so stable that it is not altered by temporary stimulation with heat, drugs, and radiation.

We compared Ro 11-8958, an analog of trimethoprim (TMP) with improved antimicrobial and pharmacokinetic properties, other dihydrofolate reductase (DHFR) inhibitors, sulfamethoxazole (SMX), and dapsone (DAP) in the treatment of Pneumocystis carinii pneumonia in an immunosuppressed rat model. In contrast to previous reports, high dosages of the DHFR inhibitors were used in combination with fixed, low dosages of SMX (3 mg/kg of body weight per day) or DAP (25 mg/kg/day). When administered alone at these dosages, SMX and DAP reduced the median P. carinii cyst count about 5- to 15-fold. Ro 11-8958, TMP, and diaveridine used at a dosage of 20 mg/kg/day with SMX were only slightly more effective than SMX used alone. However, administration of these DHFR inhibitors at a dosage of 100 mg/kg/day with SMX lowered the cyst count about 500- to 1,000-fold, indicating a synergistic effect. Little or no synergism was found when other DHFR inhibitors (pyrimethamine, cycloguanil, and tetroxoprim) were combined with SMX. Regimens of Ro 11-8958 at a dosage of 20 mg/kg/day with DAP and of TMP or diaveridine used at a dosage of 100 mg/kg/day with DAP showed comparable anti-P. carinii activity, lowering the cyst count 100- to 200-fold. By contrast, Ro 11-8958 administered at a dosage of 100 mg/kg/day with DAP reduced the cyst count > 1,000-fold. Thus, the experimental approach used here enables the rat model of pneumocystosis to be used to compare synergistic combinations of antifolate drugs. The favorable results achieved with Ro 11-8958 indicate that it should be considered for clinical trials.

Culturing Escherichia coli, Proteus mirabilis and Klebsiella pneumoniae in the presence of subinhibitory concentrations (1/4 MIC) of trimethoprim, sulphamethoxazole or their combination, resulted in reduced adherence of all the above strains. The number of phagocytosed bacteria pre-exposed to subinhibitory concentrations of the above antibiotics was not significantly changed, but a significant increase of bactericidal activity of the polymorphonuclear leucocytes was observed. Furthermore, filtrates of K. pneumoniae and P. mirabilis grown in the presence of trimethoprim alone or in combination with sulphamethoxazole induced an increased chemotactic response of human polymorphonuclear leucocytes.

The in vitro antimicrobial activities of aditoprim (AP), a new dihydrofolate reductase (DHFR) inhibitor, trimethoprim (TMP), sulfadimethoxine (SDM), sulfamethoxazole (SMX), and combinations of these drugs against some porcine respiratory tract pathogens were determined by use of an agar dilution method. The minimal inhibitory concentrations (MIC) of these agents were determined twice against Bordetella bronchiseptica (n = 10), Pasteurella multocida (n = 10), and Actinobacillus pleuropneumoniae (n = 20) strains isolated from pigs suffering from atrophic rhinitis or pleuropneumonia. All B bronchiseptica strains were resistant to AP and TMP. The MIC50 values of AP and TMP for P multocida were 0.25 and 0.06 microgram/ml, respectively, and for A pleuropneumoniae, 1 and 0.25 microgram/ml, respectively. The MIC50 values of SDM and SMX for B bronchiseptica were 4 and 1 micrograms/ml, respectively; for P multocida, 16 and 8 micrograms/ml, respectively; and for A pleuropneumoniae, 16 and 8 micrograms/ml, respectively. The investigated combinations of the DHFR inhibitors and the selected sulfonamides had synergism for the A pleuropneumoniae strains; the MIC90 values of the combinations were less than or equal to 0.06 microgram/ml. Potentiation was not observed for the B bronchiseptica and the P multocida isolates. The MIC of the combinations against B bronchiseptica and P multocida corresponded respectively to the concentrations of the sulfonamides and the DHFR inhibitors in the combinations. For A pleuropneumoniae, 2 types of strains were used (25% of serotype 2 and 75% of serotype 9). Type-2 strains had lower susceptibility than type-9 strains to AP and TMP as well as to SDM and SMX (at least a fourfold difference in MIC between the 2 types of strains).(ABSTRACT TRUNCATED AT 250 WORDS)

The in vitro activity of trimethoprim plus dapsone against oxacillin-resistant Staphylococcus aureus was comparable to that of trimethoprim plus sulfamethoxazole. Because of its different pharmacologic properties, dapsone may be a useful agent in combination with trimethoprim for the treatment of patients colonized with oxacillin-resistant S. aureus.

In order to demonstrate an immunomodulating effect of cotrimoxazole, we investigated its influence on some macrophage (M phi) functions in culture: P815 tumor cells killing, Toxoplasma gondii killing, production of free oxygen radicals by luminol-dependent chemiluminescence, prostaglandins and leukotrienes secretion evaluated after incorporation of tritiated arachidonic acid. In vitro, cotrimoxazole inhibited in a dose-dependent fashion the chemiluminescence of murine resident peritoneal or guinea pig alveolar M phi. Production of prostaglandin (PG) 6-keto-F1 alpha, PGF2 alpha, and 5-hydroxyeicosatetraenoic acid by resident peritoneal M phi was also inhibited. However, PGD2 synthesis by alveolar M phi was enhanced. A second study was performed on peritoneal M phi, resident or elicited in vivo by one intra-peritoneal injection of an extract from Mycobacterium Tuberculosis membranes and obtained from mice pretreated or not by cotrimoxazole per os. Resident M phi from cotrimoxale-treated animals showed increased production of leucotriene B4 compared to M phi from controls. 6-keto-PGF1 alpha and free oxygen radicals production by elicited M phi was greatly enhanced by cotrimoxazole whereas thromboxane B2 was reduced. Finally cotrimoxazole enhanced intracellular killing of Toxoplasma gondii and cytotoxicity for tumor cells P815 by resident but not by elicited M phi. It is concluded that cotrimoxazole can modulate MO activation and some M phi functions involved in immune homeostasis. This data could help to understand why an antibiotic such as cotrimoxazole, which is known to be frequently used in immunocompromised hosts, is also efficient in Wegener's granulomatosis.

Trimethoprim-sulfamethoxazole (TMP-SMX) or trimethoprim (TMP) alone was given on a random double-blind basis to 26 young women to treat urinary tract infections. Fecal and introital aerobic bacterial floras were identified at 1, 7, 14, and 42 days to analyze changes in these floras or development of resistance to TMP or TM-SMX. Neither TMP alone nor the TMP-SMX combination administered for 2 weeks selected a resistant fecal or introital flora. In the few individuals who had strains resistant to TMP or TMP-SMX before initiation of therapy, these organisms did not persist once therapy began. Both programs effectively cleared the introitus and rectal areas of Enterobacteriaceae. Concentrations of TMP adequate to inhibit the majority of Escherichia coli strains causing urinary tract infections were found in the vaginal secretions.

The effects of selective media and incubation atmosphere on the isolation of group A beta-hemolytic streptococci were evaluated. A higher percentage of group A streptococci was isolated on sheep blood agar incubated in air than in CO2 or anaerobic atmospheric conditions. Fewer non-group A beta-hemolytic streptococci were isolated on sheep blood agar incubated in air than in CO2 or anaerobically. Group A streptococcal isolation was not significantly affected by different incubation atmospheres on sheep blood agar containing trimethoprim-sulfamethoxazole, but detection time was longer than on sheep blood agar alone. No significant difference was found between isolation of group A streptococci on sheep blood agar incubated in air and that on sheep blood agar containing trimethoprim-sulfamethoxazole and incubated in 5 to 10% CO2; however, more group A streptococci were isolated on sheep blood agar in air within 24 h. Sheep blood agar incubated at 35 degrees C in air is, therefore, recommended for the isolation of group A streptococci from throat swabs.

The effects on pituitary-thyroid function of the commonly prescribed anti-bacterial preparations co-trimoxazole and co-trifamole, and their component drugs, have been studied in the rat and compared to the changes caused by propylthiouracil. Co-trimoxazole and co-trifamole, in doses 20-fold in excess of a pharmacological dose administered for 10 days, produced marked changes in hormone levels consistent with blocking of hyperplastic goitre formation, were also demonstrated. Propylthiouracil produced less marked changes of thyroid hormone levels but higher levels of thyroid-stimulating hormone. Pharmacological doses of co-trimoxazole and co-trifamole and sulphamoxole, the sulphonamide component of co-trifamole, caused significant changes in thyroid hormone levels consistent with anti-thyroidal activity. In contrast, there was no evidence that trimethoprim, which is common to both preparations, or sulphamethoxazole, the sulphonamide component of co-trimoxazole, had an anti-thyroidal action, indeed, serum thyroxine levels were significantly increased at pharmacological dosage. We have concluded that the new commonly prescribed combination preparations retain the goitrogenic properties of the earlier sulphonamides.

The activities of trimethoprim and sulfamethoxazole, singly and in combination, were compared with the activities of six other antimicrobial drugs against 50 anaerobic bacteria isolated from clinical specimens. Trimethoprim alone had little activity against the anaerobes tested, but sulfamethoxazole and the sulfamethoxazole/trimethoprim combination were active against most of the organisms. Results with the combination were slightly better than those with sulfamethoxazole alone.

The combination of SMZ-TMP has recently been introduced in Congo. This year (1978), it is very used by many Physicians. To help the congolese Physicians working without antibiogram frequently, we have tested 780 strains from August 1977 to August 78. The susceptibility of these strains was: for E. coli 90%, Klebsiella 69,20%, Staphylococcus 93% and for all strains studied Gram + and Gram - the percentage was 75,51. As many authors have showed, the strains of Pseudomonas, Streptococcus faecalis and Providencia are resistant. Our results remain similar to the results obtained by some french and african authors from 1970 to 1975.

The effects of inocula and media on the activities of ampicillin, penicillin, chloramphenicol and co-trimoxazole against Haemophilus influenzae were examined in vitro. Two inocula and four media were tested by the disk diffusion, broth dilution, and agar dilution methods. Chloramphenicol activity versus H. influenzae was least affected by changes in inocula and media, whereas co-trimoxazole was most susceptible to these effects. Filde's and Levinthal's agar dilution tests were most satisfactory for ampicillin. Penicillin was less active on Levinthal's than on Filde's agar. Both ampicillin and penicillin were less active when tested against the higher inoculum. Co-trimoxazole was most active (<1% H. influenzae was resistant) when tested at an inoculum of 10(6) colony-forming units/ml on diagnostic susceptibility test agar with 5% lysed horse blood added. The majority of H. influenzae appeared resistant to co-trimoxazole with increases in the test inocula and/or when tested on brain heart infusion with Filde's, Levinthal's or "low-thymidine" Mueller-Hinton medium.

A strain of Proteus mirabilis repeatedly subcultured in the presence of a combination of sulfisoxazole and 0.4 microgram/ml of trimethoprim and a strain of P. vulgaris subcultured in the presence of sulfamethoxazole and trimethoprim combined in a 5:1 ratio gradually developed resistance to the combinations. However, the level of resistance developed by the organisms exposed to the combination was always appreciably lower than the level of resistance developed by the same strains exposed to either the sulfonamide or trimethoprim alone.