Cefaclor Monohydrate-Loaded Colon-Targeted Nanoparticles for Use in COVID-19 Dependent Coinfections and Intestinal Symptoms: Formulation, Characterization, Release Kinetics, and Antimicrobial Activity.

Corona virus disease-2019 (COVID-19) emerged in Wuhan, China in December 2019 and was declared as a pandemic by the World Health Organization in March 2020. Although there is no complete treatment protocol for COVID-19, studies on this topic are ongoing, and it is known that broad-spectrum antibiotics such as cephalosporins are used for coinfections and symptoms in COVID-19 patients. Studies have shown that Staphylococcus aureus and Escherichia coli bacteria can cause symptoms such as diarrhea and coinfections accompanying COVID-19. Therefore, in this study, colon-targeted cefaclor monohydrate (CEF)-loaded poly(lactic-co-glycolic acid) (PLGA)-Eudragit S100 nanoparticles (NPs) were prepared using a nanoprecipitation technique. The particle sizes of the CEF-loaded NPs were between 171.4 and 198.8 nm. The encapsulation efficiency was in the range of 58.4%-81.2%. With dissolution studies, it has been concluded that formulations prepared with Eudragit S100 (E-coded) and Eudragit S100+PLGA (EP-coded) are pH-sensitive formulations and they are targetable to the colon, whereas the formulation prepared only with PLGA (P-coded) can release a higher CEF rate in the colon owing to the slow release properties of PLGA. The release kinetics were fitted to the Korsmeyer-Peppas and Weibull models. The antibacterial activity of E-, EP-, and P-coded formulations was 16-fold, 16-fold, and 2-fold higher than CEF, respectively, for S. aureus and E. coli according to the microdilution results. As a result of the time killing experiment, all formulations prepared were found to be more effective than the antibiotic itself for long periods. Consequently, all formulations prepared in this study hope to guide researchers/clinicians in treating both gram-positive and gram-negative bacteria-induced infections, as well as COVID-19 associated coinfections and symptoms.

Root canal dressings for revascularization influence in vitro mineralization of apical papilla cells.

Endodontic revascularization is based on cell recruitment into the necrotic root canal of immature teeth after chemical disinfection. The clinical outcome depends on the ability of surviving cells from the apical tissue to differentiate and promote hard tissue deposition inside the dentinal walls. OBJECTIVE: To investigate the effect of calcium hydroxide (CH) and modified triple antibiotic paste (mTAP - ciprofloxacin, metronidazole and cefaclor) on the viability and mineralization potential of apical papilla cells (APC) in vitro . MATERIAL AND METHODS: APC cultures were kept in contact with CH or mTAP (250-1000 µg/mL) for 5 days, after which cell viability was assessed using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Next, APCs were subjected to CH or mTAP at 250 µg/mL for 5 days before inducing the differentiation assay. After 14 and 21 days, calcium deposition was assessed by the Alizarin Red S staining method, followed by elution and quantification using spectrophotometry. Data were analyzed using ANOVA followed by Tukey post hoc test. RESULTS: CH induced cell proliferation, whereas mTAP showed significant cytotoxicity at all concentrations tested. APC treated with CH demonstrated improved mineralization capacity at 14 days, while, for mTAP, significant reduction on the mineralization rate was observed for both experimental periods (14 and 21 days). CONCLUSION: Our findings showed that CH induces cell proliferation and improves early mineralization, whereas mTAP was found cytotoxic and reduced the mineralization potential in vitro of APCs.

Root canal dressings for revascularization influence in vitro mineralization of apical papilla cells

Abstract Endodontic revascularization is based on cell recruitment into the necrotic root canal of immature teeth after chemical disinfection. The clinical outcome depends on the ability of surviving cells from the apical tissue to differentiate and promote hard tissue deposition inside the dentinal walls. Objective To investigate the effect of calcium hydroxide (CH) and modified triple antibiotic paste (mTAP - ciprofloxacin, metronidazole and cefaclor) on the viability and mineralization potential of apical papilla cells (APC) in vitro . Material and Methods APC cultures were kept in contact with CH or mTAP (250-1000 µg/mL) for 5 days, after which cell viability was assessed using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Next, APCs were subjected to CH or mTAP at 250 µg/mL for 5 days before inducing the differentiation assay. After 14 and 21 days, calcium deposition was assessed by the Alizarin Red S staining method, followed by elution and quantification using spectrophotometry. Data were analyzed using ANOVA followed by Tukey post hoc test. Results CH induced cell proliferation, whereas mTAP showed significant cytotoxicity at all concentrations tested. APC treated with CH demonstrated improved mineralization capacity at 14 days, while, for mTAP, significant reduction on the mineralization rate was observed for both experimental periods (14 and 21 days). Conclusion Our findings showed that CH induces cell proliferation and improves early mineralization, whereas mTAP was found cytotoxic and reduced the mineralization potential in vitro of APCs.

Coordination and redox interactions of ß-lactam antibiotics with Cu2+ in physiological settings and the impact on antibacterial activity.

An increase in the copper pool in body fluids has been related to a number of pathological conditions, including infections. Copper ions may affect antibiotics via the formation of coordination bonds and/or redox reactions. Herein, we analyzed the interactions of Cu2+ with eight ß-lactam antibiotics using UV-Vis spectrophotometry, EPR spectroscopy, and electrochemical methods. Penicillin G did not show any detectable interactions with Cu2+. Ampicillin, amoxicillin and cephalexin formed stable colored complexes with octahedral coordination environment of Cu2+ with tetragonal distortion, and primary amine group as the site of coordinate bond formation. These ß-lactams increased the solubility of Cu2+ in the phosphate buffer. Ceftazidime and Cu2+ formed a complex with a similar geometry and gave rise to an organic radical. Ceftriaxone-Cu2+ complex appears to exhibit different geometry. All complexes showed 1:1 stoichiometry. Cefaclor reduced Cu2+ to Cu1+ that further reacted with molecular oxygen to produce hydrogen peroxide. Finally, meropenem underwent degradation in the presence of copper. The analysis of activity against Escherichia coli and Staphylococcus aureus showed that the effects of meropenem, amoxicillin, ampicillin, and ceftriaxone were significantly hindered in the presence of copper ions. The interactions with copper ions should be taken into account regarding the problem of antibiotic resistance and in the selection of the most efficient antimicrobial therapy for patients with altered copper homeostasis.

Biophysical control of the growth of Agrobacterium tumefaciens using extremely low frequency electromagnetic waves at resonance frequency.

Isolated Agrobacterium tumefaciens was exposed to different extremely low frequencies of square amplitude modulated waves (QAMW) from two generators to determine the resonance frequency that causes growth inhibition. The carrier was 10 MHz sine wave with amplitude ±10 Vpp which was modulated by a second wave generator with a modulation depth of ± 2Vpp and constant field strength of 200 V/m at 28 °C. The exposure of A. tumefaciens to 1.0 Hz QAMW for 90 min inhibited the bacterial growth by 49.2%. In addition, the tested antibiotics became more effective against A. tumefaciens after the exposure. Furthermore, results of DNA, dielectric relaxation and TEM showed highly significant molecular and morphological changes due to the exposure to 1.0 Hz QAMW for 90 min. An in-vivo study has been carried out on healthy tomato plants to test the pathogenicity of A. tumefaciens before and after the exposure to QAMW at the inhibiting frequency. Symptoms of crown gall and all pathological symptoms were more aggressive in tomato plants treated with non-exposed bacteria, comparing with those treated with exposed bacteria. We concluded that, the exposure of A. tumefaciens to 1.0 Hz QAMW for 90 min modified its cellular activity and DNA structure, which inhibited the growth and affected the microbe pathogenicity.

Use of platelet-rich plasma for regeneration in non-vital immature permanent teeth: Clinical and cone-beam computed tomography evaluation.

Objective This study was performed to assess the clinical and radiological outcomes of a revascularization procedure in immature teeth with apical periodontitis using platelet-rich plasma (PRP). The PRP protocol and conventional revascularization protocol, which used a blood clot as the scaffold, were compared. Methods Thirty non-vital immature permanent teeth were randomly categorized into two groups. After disinfecting the root canal space with triple antibiotic paste (1:1:1 ciprofloxacin, metronidazole, and cefaclor), a tissue scaffold was created using either PRP or a blood clot (control) and covered with white mineral trioxide aggregate. All cases were followed up clinically and radiographically for 12 months. Differences in bone density, root length, and lesion size were calculated using preoperative and postoperative computed tomography images. The means of the differences in individual parameters in the blood clot and PRP groups were compared using the Mann-Whitney U test. Results After 5 months, sensitivity tests (cold and electric pulp tests) elicited a delayed positive response in 23 sites. At 12 months, cone-beam computed tomography revealed resolution or a decrease in lesion size and an increase in bone density in all 30 (100%) teeth. Additionally, continued root development was observed in 22 (73%) teeth and early root growth was observed in the test group (mineral trioxide aggregate with PRP). Conclusions The results of this study suggest that PRP can serve as a successful scaffold for regenerative endodontic treatment. With the exception of a significant increase in root length, the results of treatment with PRP were not significantly different from those of the conventional protocol using a blood clot as the scaffold.

Penicillin Binding Protein 1 Is Important in the Compensatory Response of Staphylococcus aureus to Daptomycin-Induced Membrane Damage and Is a Potential Target for ß-Lactam-Daptomycin Synergy.

The activity of daptomycin (DAP) against methicillin-resistant Staphylococcus aureus (MRSA) is enhanced in the presence of ß-lactam antibiotics. This effect is more pronounced with ß-lactam antibiotics that exhibit avid binding to penicillin binding protein 1 (PBP1). Here, we present evidence that PBP1 has a significant role in responding to DAP-induced stress on the cell. Expression of the pbpA transcript, encoding PBP1, was specifically induced by DAP exposure whereas expression of pbpB, pbpC, and pbpD, encoding PBP2, PBP3, and PBP4, respectively, remained unchanged. Using a MRSA COL strain with pbpA under an inducible promoter, increased pbpA transcription was accompanied by reduced susceptibility to, and killing by, DAP in vitro. Exposure to ß-lactams that preferentially inactivate PBP1 was not associated with increased DAP binding, suggesting that synergy in the setting of anti-PBP1 pharmacotherapy results from increased DAP potency on a per-molecule basis. Combination exposure in an in vitro pharmacokinetic/pharmacodynamic model system with ß-lactams that preferentially inactivate PBP1 (DAP-meropenem [MEM] or DAP-imipenem [IPM]) resulted in more-rapid killing than did combination exposure with DAP-nafcillin (NAF) (nonselective), DAP-ceftriaxone (CRO) or DAP-cefotaxime (CTX) (PBP2 selective), DAP-cefaclor (CEC) (PBP3 selective), or DAP-cefoxitin (FOX) (PBP4 selective). Compared to ß-lactams with poor PBP1 binding specificity, exposure of S. aureus to DAP plus PBP1-selective ß-lactams resulted in an increased frequency of septation and cell wall abnormalities. These data suggest that PBP1 activity may contribute to survival during DAP-induced metabolic stress. Therefore, targeted inactivation of PBP1 may enhance the antimicrobial efficiency of DAP, supporting the use of DAP-ß-lactam combination therapy for serious MRSA infections, particularly when the ß-lactam undermines the PBP1-mediated compensatory response.

Characterization and antibiotic susceptibility of Streptococcus agalactiae isolates causing urinary tract infections.

Streptococcus agalactiae (GBS) has been implicated in urinary tract infections but the microbiological characteristics and antimicrobial susceptibility of these strains are poorly investigated. In this study, 87 isolates recovered from urine samples of patients who had attended the Spedali Civili of Brescia (Italy) and had single organism GBS cultured were submitted to antimicrobial susceptibility testing, molecular characterization of macrolide and levofloxacin resistance, PCR-based capsular typing and analysis of surface protein genes. By automated broth microdilution method, all isolates were susceptible to penicillin, cefuroxime, cefaclor, and ceftriaxone; 80%, 19.5% and 3.4% of isolates were non-susceptible to tetracycline, erythromycin, and levofloxacin, respectively. Macrolide resistance determinants were iMLS(B) (n=1), cMLS(B) (n=10) and M (n=5), associated with ermTR, ermB and mefA/E. Levofloxacin resistance was linked to mutations in gyrA and parC genes. Predominant capsular types were III, Ia, V, Ib and IX. Type III was associated with tetracycline resistance, while type Ib was associated with levofloxacin resistance. Different capsular type-surface protein gene combinations (serotype V-alp2, 3; serotype III-rib; serotype Ia-epsilon) were detected. A variety of capsular types are involved in significant bacteriuria. The emergence of multidrug resistant GBS may become a significant public health concern and highlights the importance of careful surveillance to prevent the emergence of these virulent GBS.

Covalent inhibition of New Delhi metallo-ß-lactamase-1 (NDM-1) by cefaclor.

Covalent irreversible inhibitors can successfully treat antibiotic-resistant infections by targeting serine ß-lactamases. However, this strategy is useless for New Delhi metallo-ß-lactamase (NDM), which uses a non-covalent catalytic mechanism and lacks an active-site serine. Here, NDM-1 was irreversibly inactivated by three ß-lactam substrates: cephalothin, moxalactam, and cefaclor, albeit at supratherapeutic doses (e.g., cefaclor KI =2.3 ± 0.1 mM; k(inact) =0.024 ± 0.001 min(-1)). Inactivation by cephalothin and moxalactam was mediated through Cys208. Inactivation by cefaclor proceeded through multiple pathways, in part mediated by Lys211. Use of a cefaclor metabolite enabled mass spectrometric identification of a +346.0735 Da covalent adduct on Lys211, and an inactivation mechanism is proposed. Lys211 was identified as a promising "handhold" for developing covalent NDM-1 inhibitors and serves as a conceptual example for creating covalent inhibitors for enzymes with non-covalent mechanisms.

Synthesis, spectral and antibacterial sudies of copper(II) tetraaza macrocyclic complexes.

A novel family of tetraaza macrocyclic Cu(II) complexes [CuLX(2)] (where L = N(4) donor macrocyclic ligands) and (X = Cl(-), NO(3) (-)) have been synthesized and characterized by elemental analysis, magnetic moments, IR, EPR, mass, electronic spectra and thermal studies. The magnetic moments and electronic spectral studies suggest square planar geometry for [Cu(DBACDT)]Cl(2) and [Cu(DBACDT)](NO(3))(2) complexes and distorted octahedral geometry to the rest of the ten complexes. The biological activity of all these complexes against gram-positive and gram-negative bacteria was compared with the activity of existing commercial antibacterial compounds like Linezolid and Cefaclor. Six complexes out of twelve were found to be most potent against both gram-positive as well as gram-negative bacteria due to the presence of thio group in the coordinated ligands.

Evaluation of cefaclor oral suspensions stability using reversed phase high performance liquid chromatography and antimicrobial diffusion methods.

The effect of temperature stresses on Cefaclor suspensions under different storage conditions for a duration of 14 days was tested. The degradation of Cefaclor was determined on the 2nd, 7th and 14th day after reconstitution using a sensitive and precise Reversed phase High Performance Liquid Chromatographic (RP-HPLC) method. The RSD values for Forticef, Midocef, Ceclor, Cefabac and Cloracef, indicated a good precision of the RP-HPLC method. The limit of detection (LOD) and the limit of quantification (LOQ) were found 0.008 mg/ml and 0.03mg/ml respectively. The antimicrobial effect of Cefaclor suspension was also tested against pathogenic bacteria using the cylinder diffusion method. The RSD values range of the antimicrobial assay for all the Cefaclor compounds were 1.47-3.7%. The LOD and LOQ were 0.2mg/ml and 1mg/ml respectively. During the normal use of Ceclor, Midocef, and Forticef the loss of activity and the degradation were less than 5% on the 14th day of preservation at 4°C. However, the percentage of degradation for Cefabac and Cloracef on the 14th day reached 5 and 6%, respectively. Statistical multiple comparison between the effect of 4°C and 25°C indicated non significant mean differences (P>0.05) for Forticef, Cefabac, Ceclor and Cloraf and significant effect for Midocef (P <0.05). Significant effects were observed between (4oC and 37°C) and (25°C and 37°C) for all except Ceclor. Multiple comparisons between days of storage showed non significant mean difference values at 4°C except Cefabac. However significant results between days were found at 25°C and 37°C except for Midocef between (7th and 14th day). It was found that the pediatric suspensions of Cefaclor in the Jordanian market were stable and contained the amount of active ingredient specified by the United States pharmacopoeias specification (USP) and the British Pharmacopoeias specifications (BP).

Evaluation of disk diffusion methods to detect low-level ß-lactamase-negative ampicillin-resistant Haemophilus influenzae.

We evaluated the efficacy of disk diffusion methods for detection of low-level ß-lactamase-negative ampicillin-resistant (low-BLNAR) Haemophilus influenzae. Four hundred and seventy unselected, recent clinical isolates were tested with ampicillin (10 µg), cefaclor (30 µg) and cefuroxime (30 µg) on iso-Sensitest agar enriched with nicotinamide adenine dinucleotide (NAD) and horse blood [ST agar; Swedish Reference Group for Antibiotics (SRGA) guidelines], and on chocolate agar (in-house guidelines). Selected isolates (n = 147) were subjected to partial sequencing of the ftsI gene. Forty-seven strains (10.0%) were genotypically identified as low-BLNAR, which was confirmed by determination of minimal inhibitory concentration (MIC) using microbroth dilution method: only low level resistance to ampicillin was detected [MIC ≤1 µg/mL; MIC(50) = 0.5 µg/mL, implying susceptibility by Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antibiotic Susceptibility Testing (EUCAST) interpretative criteria]. The MIC of cefuroxime varied between 1 and 4 µg/mL (MIC(50) = 2 µg/mL), indicating susceptibility to cefuroxime by CLSI but not by EUCAST guidelines. Disk diffusion methods were able to discriminate low-BLNAR H. influenzae from the wild-type population with sensitivities ranging from 87% to 98% and specificities from 96% to 99%. Cefaclor was found to be superior to cefuroxime and ampicillin. Cefaclor zone diameter breakpoints of 30/29 and 23/22 mm are suggested for ST agar and chocolate agar, respectively.

Beta-lactams interfering with PBP1 induce Panton-Valentine leukocidin expression by triggering sarA and rot global regulators of Staphylococcus aureus.

Previous articles reported that beta-lactam antibiotics increase the expression of Staphylococcus aureus Panton-Valentine leukocidin (PVL) by activating its transcription. We investigated the mechanisms underlying the inductor effect of beta-lactams on PVL expression by determining targets and regulatory pathways possibly implicated in this process. We measured PVL production in the presence of oxacillin (nonselective), imipenem (penicillin-binding protein 1 [PBP1] selective), cefotaxime (PBP2 selective), cefaclore (PBP3 selective), and cefoxitin (PBP4 selective). In vitro, we observed increased PVL production consistent with luk-PV mRNA levels that were 20 to 25 times higher for community-acquired methicillin-resistant S. aureus (CA-MRSA) cultures treated with PBP1-binding oxacillin and imipenem than for cultures treated with other beta-lactams or no antibiotic at all. This effect was also observed in vivo, with increased PVL mRNA levels in lung tissues from CA-MRSA-infected mice treated with imipenem but not cefoxitin. To confirm the involvement of PBP1 inhibition in this pathway, PBP1 depletion by use of an inducible pbp1 antisense RNA showed a dose-dependent relationship between the level of pbp1 antisense RNA and the luk-PV mRNA level. Upon imipenem treatment of exponential-phase cultures, we observed an increased sarA mRNA level after 30 min of incubation followed by a decreased rot mRNA level after 1 to 4 h of incubation. Unlike the agr and saeRS positive regulators, which were nonessential for PVL induction by beta-lactams, the sarA (positive) and rot (negative) PVL regulators were necessary for PVL induction by imipenem. Our results suggest that antibiotics binding to PBP1 increase PVL expression by modulating sarA and rot, which are essential mediators of the inductor effect of beta-lactams on PVL expression.

Protein hydrolysate-induced cholecystokinin secretion from enteroendocrine cells is indirectly mediated by the intestinal oligopeptide transporter PepT1.

Dietary protein is a major stimulant for cholecystokinin (CCK) secretion by the intestinal I cell, however, the mechanism by which protein is detected is unknown. Indirect functional evidence suggests that PepT1 may play a role in CCK-mediated changes in gastric motor function. However, it is unclear whether this oligopeptide transporter directly or indirectly activates the I cell. Using both the CCK-expressing enteroendocrine STC-1 cell and acutely isolated native I cells from CCK-enhanced green fluorescent protein (eGFP) mice, we aimed to determine whether PepT1 directly activates the enteroendocrine cell to elicit CCK secretion in response to oligopeptides. Both STC-1 cells and isolated CCK-eGFP cells expressed PepT1 transcripts. STC-1 cells were activated, as measured by ERK(1/2) phosphorylation, by both peptone and the PepT1 substrate Cefaclor; however, the PepT1 inhibitor 4-aminomethyl benzoic acid (AMBA) had no effect on STC-1 cell activity. The PepT1-transportable substrate glycyl-sarcosine dose-dependently decreased gastric motility in anesthetized rats but had no affect on activation of STC-1 cells or on CCK secretion by CCK-eGFP cells. CCK secretion was significantly increased in response to peptone but not to Cefaclor, cephalexin, or Phe-Ala in CCK-eGFP cells. Taken together, the data suggest that PepT1 does not directly mediate CCK secretion in response to PepT1 specific substrates. PepT1, instead, may have an indirect role in protein sensing in the intestine.

[A simple disk diffusion test to identify beta-lactamase-negative, ampicillin-resistant Haemophilus influenzae--application of cephalexin, cefsulodin and cefaclor disks].

Currently, beta-lactamase-negative (BLN) ampicillin-resistant (AR) strains of Haemophilus influenzae are prevalent in Japan. BLNAR strains are defined by the presence of specific mutation(s) in the ftsI gene but are not phenotypically distinguishable by ampicillin (ABPC) susceptibility. In the present study, we showed that cephalexin (CEX), cefsulodin (CFS), and cefaclor (CCL) disk diffusion tests can be effectively used to identify BLNAR strains. A total of 169 clinical isolates of BLN H. influenzae, consisting of 113 of BLNAR and 56 of BLN, ampicillin-susceptible (AS), were included. All the isolates were genetically defined by detection of the TEM gene and partial sequencing of the ftsI gene. The Clinical and Laboratory Standards Institute (CLSI) standard broth microdilution and disk diffusion tests for ABPC provided 20% and 19% false susceptible rates, respectively. Alternatively, 34 cephem agents were tested using disk diffusion. Of the agents tested, CEX, CFS, and CCL disks could effectively discriminate between BLNAR and BLNAS isolates. All the BLNAS isolates showed visible growth inhibitory zones around CEX and CFS disks, but 108 (95.6%) and 106 (93.8%) BLNAR isolates did not. The results indicated 100% predictive values (PVs) for BLNAR and PVs for BLNAS were 91.8% for CEX and 88.9% for CFS. The CLSI-based interpretations for CCL (> or =20 mm) also highly correlated with BLNAR and BLNAS, PVs for BLNAR and for BLNAS being 100% and 93.3%, respectively. With simplicity and discriminability of the test method, we recommend a CEX disk diffusion test in combination with a rapid beta-lactamase test to identify BLNAR isolates in clinical laboratories.

In vitro antimicrobial activity of cefditoren and other oral antibiotics against Streptococcus pneumoniae, isolated from children with community acquired respiratory tract infections.

The antibacterial susceptibility to frequently prescribed antibiotics of Streptococcus pneumoniae isolated from the pediatric patients with acute respiratory infectious diseases was investigated in a study of three medical institutions in Korea. Total 143 clinical isolates of S. pneumoniae were available for susceptibility tests between May 2003 and July 2007. Antimicrobial susceptibility data for S. pneumoniae were analyzed by using agents of amoxicillin, cefaclor, cefuroxime, cefdinir, and cefditoren as the test antibiotics. The prevalence of each resistance class, penicillin-resistant S. pneumoniae (PRSP) were high with the proportion of MIC range (susceptible = 8.4%, intermediate resistance = 18.2%, resistance = 73.4%). MIC90 and susceptible (S) rate of antimicrobial agents to the strains tested were amoxicillin (MIC90 = 4 microg/ml, S = 76.2%), cefaclor (MIC90 = 128 microg/ml, S=8.4%), cefuroxime (MIC90 = 16 microg/ml, S = 24.5%), cefdinir (MIC90 = 16 microg/ml, S = 21.8%), and cefditoren (MIC90 = 0.5 microg/ml, S=90.2%) respectively. Against clinical isolates including PRSP, cefditoren demonstrated the strongest antibacterial activity intrinsically among the antibiotics tested. Conclusively, the antimicrobial activity of cefditoren to S. pneumoniae strains isolated from pediatric patients with acute respiratory infection is very high. In South Korea, where the antibiotic resistance ofS. pneumoniae is issued, cefditoren is expected to be used as a primary or secondary antibiotic. Moreover, cefditoren may serve as a useful option for secondary antibiotics after failure of amoxicillin treatment, which is most primarily used for acute respiratory S. pneumoniae infection in children.

blaROB-1 presence on pB1000 in Haemophilus influenzae is widespread, and variable cefaclor resistance is associated with altered penicillin-binding proteins.

Plasmid pB1000 is a small replicon recently identified as bearing bla(ROB-1) in animal and human Pasteurellaceae in Spain. We identified pB1000 in 11 bla(ROB-1)-positive Australian and North American Haemophilus influenzae isolates, suggesting a wider role for pB1000 in disseminating bla(ROB-1). Native H. influenzae conjugative elements can mobilize plasmids similar to pB1000 at a low frequency of 10(-8), and this might account for the infrequency of bla(ROB-1) compared to the rate of occurrence of bla(TEM-1). Altered penicillin-binding protein 3 was associated with an increased cefaclor MIC in 3 isolates.

Haemophilus influenzae clinical isolates with plasmid pB1000 bearing blaROB-1: fitness cost and interspecies dissemination.

Plasmid pB1000 is a mobilizable replicon bearing the bla(ROB-1) beta-lactamase gene that we have recently described in Haemophilus parasuis and Pasteurella multocida animal isolates. Here we report the presence of pB1000 and a derivative plasmid, pB1000', in four Haemophilus influenzae clinical isolates of human origin. Pulsed-field gel electrophoresis showed unrelated patterns in all strains, indicating that the existence of pB1000 in H. influenzae isolates is not the consequence of clonal dissemination. The replicon can be transferred both by transformation and by conjugation into H. influenzae, giving rise to recipients resistant to ampicillin and cefaclor (MICs, > or =64 microg/ml). Stability experiments showed that pB1000 is stable in H. influenzae without antimicrobial pressure for at least 60 generations. Competition experiments between isogenic H. influenzae strains with and without pB1000 revealed a competitive disadvantage of 9% per 10 generations for the transformant versus the recipient. The complete nucleotide sequences of nine pB1000 plasmids from human and animal isolates, as well as the epidemiological data, suggest that animal isolates belonging to the Pasteurellaceae act as an antimicrobial resistance reservoir for H. influenzae. Further, since P. multocida is the only member of this family that can colonize both humans and animals, we propose that P. multocida is the vehicle for the transport of pB1000 between animal- and human-adapted members of the Pasteurellaceae.

Pharmacokinetic interaction between cefaclor and bromhexine in healthy Chinese volunteers.

OBJECTIVE: To determine the pharmacokinetic interaction between cefaclor and bromhexine in healthy Chinese volunteers. METHODS: Twelve subjects received a cefaclor (CEF) treatment, a bromhexine (BHX) treatment, and a co-treatment of CEF and BHX with a 3 x 3 Latin square design. The wash-out time between periods was 14 days. The plasma and urine drug concentrations of CEF and BHX were detected by HPLC-UV and LC/MS, respectively. RESULTS: All the 12 volunteers completed the study. There were no significant differences in AUC 0-t and Cmax of CEF in logarithm between the single administration group of CEF and the co-administration group of CEF with BHX. Two one sided t-test showed that CEF was bioequivalent in the 2 groups. There were no significant differences in tmax, MRT, t1/2, and Clr between the 2 groups. Vd/F was significantly lower in the single CEF group than in the co-administration group of CEF and BHX. There were no significant differences of AUC 0-t and Cmax of BHX in logarithm between the single administration group of BHX and the co-administration group of BHX with CEF. Two one sided t-test showed that BHX was bioequivalent in the 2 groups. There were no significant differences in tmax, MRT, t1/2, Vd/F, and Clr between the 2 groups. CONCLUSION: There is no significant pharmacokinetic parameter change in the drug absorption, metabolism, and excretion, but Vd/F of CEF significant increases in the co-administration of CEF with BHX. The co-administration of CEF and BHX has no adverse drug interaction. The increase of Vd/F may be a favorable drug interaction, which may be the mechanism of the synergistic effect of the 2 drugs.

Interactions of amoxicillin and cefaclor with human renal organic anion and peptide transporters.

Amoxicillin and cefaclor are two of the widely used beta-lactam antibiotics in the treatment of urinary tract infections. Both drugs are eliminated mainly by the kidney and rely on renal excretion to exert their antibacterial activities in the urinary tract. Previous studies have suggested the involvement of organic anion and oligopeptide transporters in membrane transport of beta-lactams. The objective of the current study was to examine the kinetics of amoxicillin and cefaclor interactions with human renal transporters human organic anion transporter 1 (hOAT1), human peptide transporter 1 (hPepT1), and human peptide transporter 2 (hPepT2) in detail, both as substrates and as inhibitors. Using fluorescence protein tagging and cell sorting, we established Madin-Darby canine kidney cell lines stably expressing highly functional hOAT1, hPepT1, and hPepT2. Amoxicillin and cefaclor inhibited hOAT1-mediated [(3)H]para-aminohippuric acid uptake (K(i) = 11.0 and 1.15 mM, respectively). However, our uptake study revealed that neither drug was transported by hOAT1. Amoxicillin and cefaclor competitively inhibited hPepT2-mediated [(3)H]glycylsarcosine uptake (K(i) = 733 and 65 muM, respectively), whereas much lower affinity for hPepT1 was observed with both antibiotics. Direct uptake studies demonstrated that amoxicillin and cefaclor were transported by hPepT1 and hPepT2. Kinetic analysis showed that hPepT2-mediated uptake of both drugs was saturable with K(m) of 1.04 mM for amoxicillin and 70.2 muM for cefaclor. hPepT2, and to a lesser extent hPepT1, may play an important role in apical transport of amoxicillin and cefaclor in the renal tubule. hOAT1, in contrast, is not involved in basolateral uptake of these antibiotics.