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[Evaluation of antibiotics used for enterohemorrhagic Escherichia coli O157 enteritis--effect of various antibiotics on extracellular release of verotoxin].

We tested antimicrobial activities of ten oral antibiotics; ampicillin (ABPC), cefdinir (CFDN), cefaclor (CCL), fosfomycin (FOM), norfloxacin (NFLX), nalidixic acid (NA), kanamycin (KM), minocycline (MINO), doxycycline (DOXY), and tetracycline (TC) against eleven enterohemorrhagic Esherichia coli (EHEC) O157 clinical strains. Two strains were resistant to ABPC and TC. Other strains were sensitive to all the ten antibiotics. To investigate the effect of antibiotics on extracellular release of verotoxin (VT), strain EHEC TT10 was grown in 10 ml of LB containing various concentrations of the antibiotics for 2 h. Number of viable cells were counted and the amounts of VT1 and VT2 released in the supernatants were measured with reverse passive latex agglutination (RPLA) using serially diluted sterilized culture supernatants. The amount of VT1 and VT2 was evidently increased with ABPC, CFDN, CCL, and FOM, the inhibitors of cell wall biosynthesis. In the case of quinolons, VT2 was markedly increased, but VT1 was not released to the supernatant. KM killed the bacteria efficiently, but no release of VT1 or VT2 was observed in the supernatant. Tetracyclines (MINO, DOXY, and TC) did not make the bacteria release either VT1 or VT2, but could not kill the bacteria appreciably. These results indicated that the inhibitors of protein synthesis (KM, MINO, DOXY, TC) are the safe antibiotics not causing the release of verotoxin from the cells and thus preventing development of hemolytic uremic syndrome (HUS) or thrombotic thrombocytopenic purpra (TTP), the important sequelae of the enteritis.

Ampicillin Resistance↗

[Result of antibiotic therapy for children with Escherichia coli O26:H11 infection].

Between the end of November 1996 and the beginning of March 1997, there was an outbreak of Escherichia coli O26:H11 infection in Asahikawa. The strain produced only verotoxin type 1. The minimal inhibitory concentrations (microgram/ml) of the strain under aerobic condition and those of anaerobic were as follows: chloramphenicol (1.56, 0.78), minocycline (12.5, 3.13), kanamycin (3.13, 25), ampicillin (> 100, > 100), fosfomycin (12.5, 1.56), norfloxacin (0.1, 0.1), and cefaclor (6.25, 3.13). Forty-one episodes of antibiotic therapy to 32 children, who were treated in Asahikawa Kosei Hospital, Asahikawa Municipal Hospital, and Asahikawa Red Cross Hospital, were evaluated bacteriologically. In 26 episodes treated with fosfomycin, the pathogen from stools of 19 were eradicated, 4 were not eradicated, and 3 were isolated again within 2 weeks after the cessation of therapy. Eight episodes treated with norfloxacin and 5 episodes in kanamycin were all eradicated.

Anti-Bacterial Agents↗

[Therapeutic effects of antibiotics against enterohemorrhagic Escherichia coli (EHEC) O157:H7 (O157) infection: in vivo analysis using germfree mice].

Though O157 can cause a life-threatening diseases, the therapeutic protocol using antibiotics for the infection is still controversial. Main reasons for hesitating the uses of antibiotics for the infection is their possibility to enhance the release of verotoxins (VT). We have recently established the mouse model of O157 infection using germfree mice. Using this animal model of O157 infection, we examined therapeutic efficacy of antibiotics. Fosfomycin (FOM) and norfloxacin (NFLX) were selected for in vivo examination, because of their lower MIC under anaerobic condition (MIC:FOM = 0.78; NFLX = 0.10 microgram/ml) than those of the other antibiotics including kanamycin, doxycycline, minocycline, choramphenicol, cefaclor and ampicilin. When germfree BALB/c mice were orally infected with 1 x 10(5)CFU of O157 (clinically-isolated strain, TI001) at day 0, all mice died at 8 to 9 d after the infection. Oral treatment of the mice with FOM (500 mg/kg/d, twice a day) or NFLX (50 mg/kg/d, twice a day) everyday for 5 days starting at 3 hr after the infection significantly improved the survival rate from 0% to 83.3%, and 100%, respectively. VT could not be detected in the feces of the mice in either groups, suggesting that neither of these antibiotics enhanced the release of VT. Interestingly, when FOM treatment was started at 3, 6, 12 or 24 hr after the infection, the survival rate was 100%, 100%, 0% and 0%, respectively. Thus, in conclusion, FOM and NFLX are both useful as the therapeutic agents for O157 infection. However, the treatment should be started in the early phase after the infection.

Animals↗

[Murine typhus infected in Oku-etsu area, Fukui Prefecture].

A 15-year-old girl, high school student, became febrile (38-39 degrees C) with chills, sore throat and cough on April 20, 1994. Until the onset, she was healthy and she had been camping with her classmates in a wooded mountainous area in Oku-etsu, Fukui Prefecture. She consulted a local clinic on April 21 and bacampicillin was initially administered and then changed to cefaclor on April 23. However, high body temperature continued and a maclopapular rash appeared on her face on April 24 and gradually spread to her anterior chest and back. Blood examination showed a WBC count of 2,200/microliter, and she was admitted to our hospital on April 25. On admission, peripheral blood data showed leukocytopenia (WBC 2,300/microliter) with 5% atypical lymphocytes. Titers of anti-Rickettsia typhi serum antibodies (IgM, -G) were elevated (1:80, 1:640) and she was diagnosed as having murine typhus. On the second hospital day, 200 mg of minocycline (MINO) was administered per os and her body temperature fell to within the normal limits on the third hospital day. On the 7th hospital day, the skin rash disappeared and she was discharged. Altogether, 320 high school students went camping with this patient. Among them, approximately 30 students had similar symptoms and signs as this case and had been diagnosed suspected viral infection. Twelve students of the 30 were admitted to other hospitals. It was considered that this case was part of an outbreak of murine typhus in the Oku-etsu area, Fukui Prefecture, but no further investigation was performed. Murine typhus is usually a benign disease that is controllable by the administration of MINO. In rare cases, infection can worsen to multiorganic failure, severe complications have been reported in 1-4% of cases, and death has been reported in less than 3%. Recently, it has also been reported that MINO not only has an antibiotic effect, but also play acts as a cytokine modulator in patients with rickettsial infection. Thus, in febrile patients in whom uncommon Rickettsia infection is suspected, serological test for murine typhus should be examined and the immediate administration of MINO is important.

Adolescent↗

[Report of questionnaire survey for methicillin-resistant Staphylococcus aureus and penisillin-resistant Streptococcus pneumoniae between 1998 and 2000 in the Kinki district].

Kinki Infection Working Group made an annual (1998-2000) comparative study of an epidemiological investigation for Staphylococcus aureus and Streptococcus pneumoniae in the Kinki district. The number of S. aureus and methicillin-resistant S. aureus (MRSA) isolated decreased for three years, but the isolation frequencies of MRSA has not changed which was approximately 60%. All strains of MRSA were not resistant to vancomysin (VCM) and teicoplanin (TEIC), and the frequencies of resistance to sulfamethoxazole-trimethoprim (ST) and arbekacin (ABK) were 0.1 to 0.7% and 1.9 to 3.1%, respectively. On the other hand, the number of S. aureus and penicillin-resistant S. pneumoniae (PRSP) isolated did not show a consistent tendency, but the isolation frequencies of PRSP has increased for three years. All strains of PRSP were sensitive to vancomycin (VCM), but the frequencies of resistance to cefaclor and other some antibiotics have increased.

Humans↗

[Annual changes in antimicrobial susceptibility and macrolide resistance of Streptococcus pyogenes from 1995 through 2004].

This aim of this study was to reveal annual changes in antibiotic susceptibility, especially the macrolide susceptibility of Streptococcus pyogenes. A total of 755 strains of S. pyogenes were clinicaly isolated from throat swabs of children from 1995 through 2004 in Chiba Municipal Kaihin Hospital. All isolates were fully susceptible to benzylpenicillin, cefotaxim and cefaclor. The rate of resistance to erythromycin (EM) was over 10% every year after 2001 and 19% in 2004, and the rate of high resistance (MIC > or =16 microg/mL) has been increasing. A significant increase in EM resistance was observed over a 10-year period. There were 118 strains (15.6%) that persisted after treatment with beta-lactams. In the past few years it has been discovered that some S. pyogenes can be internalized by human cells of respiratory tract origin and survive within them. Since beta-lactams do not reach high intracellular concentrations, this ability of S. pyogenes may be related to treatment failure. Since macrolides can enter eukaryotic cells and remain active in intracellular compartments, they will be effective for these S. pyogenes. In case of pharyngitis which againist treatment with beta-lactams, there is a possibility macrolides are effective. Macrolides may be effective in pharyngitis resistant to treatment with beta-lactams. However, macrolide resistance is not rare, susceptibility must be tested.

Anti-Bacterial Agents↗

Diversity of ampicillin resistance genes and antimicrobial susceptibility patterns in Haemophilus influenzae strains isolated in Korea.

By Etest determination of the susceptibilities of 229 Haemophilus influenzae strains isolated in Korea to 10 antibiotics, the isolates were found to be antibiotic nonsusceptible in the following order: ampicillin (58.1%), trimethoprim-sulfamethoxazole (52%), cefaclor (41.1%), clarithromycin (25.8%), chloramphenicol (14.0%), amoxicillin-clavulanic acid (13.5%), meropenem (11.7%), cefixime (10.9%), cefuroxime (9.2%), and levofloxacin (1.3%). The prevalences of each resistance class were 23.6% for beta-lactamase-negative ampicillin-susceptible (BLNAS) strains; 37.6% for strains with the TEM-1 type beta-lactamase gene; 1.3% for strains with the ROB-1 type beta-lactamase gene; 29.3% for the beta-lactamase-negative ampicillin-resistant (BLNAR) strains with a mutation in the ftsI gene, which encodes PBP 3; and 8.3% for beta-lactamase-positive amoxicillin-clavulanate-resistant (BLPACR) strains, which showed both resistance mechanisms (i.e., a beta-lactamase gene and a mutation in the ftsI gene). The MIC50s of all beta-lactams, including cephem and meropenem agents, for the BLNAR strains were two to three times higher than those for the BLNAS strains. This study confirms that the prevalence of BLNAR and BLPACR strains is relatively high and for the first time confirms the presence of H. influenzae strains carrying blaROB-1 in Korea. Even though mutations in another gene(s) might be involved in beta-lactam resistance, these results suggest that mutations in the ftsI gene are important for the development of resistance to beta-lactams in H. influenzae strains in Korea.

Ampicillin Resistance↗

Comparative activities of selected beta-lactam antibiotics against Haemophilus influenzae.

The comparative activities of ampicillin, cefamandole, cefoxitin, cefaclor, and cefatrizine against both beta-lactamase-producing and non-beta-lactamase-producing isolates of Haemophilus influenzae were determined by using an agar dilution susceptibility test procedure. Ampicillin was the most active drug tested against non-beta-lactamase-producing isolates, whereas cefamandole was most active against beta-lactamase-producing strains.

Anti-Bacterial Agents↗

Use of a heavy inoculum in the in vitro evaluation of the anti-staphylococcal activity of 19 cephalosporins.

The in vitro activity of 19 cephalosporins against 105 clinical isolates of Staphylococcus aureus and S. epidermidis was determined by using a heavy inoculum, i.e., 10(8) to 10(9) organisms per ml, to maximally challenge the antibiotics. The anti-staphylococcal activities of cephaloridine and 87/312 were consistently decreased by the use of a heavy inoculum when compared with the activity obtained with two less-concentrated inocula. The activity of most of the other compounds was also decreased with the use of a heavy inoculum, but this was observed only with selected isolates. Cephapirin, cephalothin, and cefazaflur were the most active drugs against the methicillin-susceptible isolates. Cephaloridine, cefamandole, cefazaflur, and 87/312 had substantial activity against methicillin-resistant staphylococci even with heavy inocula. With the exception of cefaclor against S. aureus, the orally absorbed cephalosporins were generally one-half to one-sixteenth as active as the parenterally administered cephalosporins. The median minimal inhibitory concentrations of five of the 12 parenteral cephalosporins were lower with the methicillin-susceptible S. aureus than with the methicillin-susceptible S. epidermidis strains.

Bacteriological Techniques↗

Susceptibility of Eikenella corrodens to ten cephalosporins.

The susceptibility of 24 strains of Eikenella corrodens was determined, by the agar dilution technique, to 10 cephalosporins, as well as to clindamycin, penicillin and dicloxacillin. All strains were uniformly very susceptible to penicillin G and cefoxitin and resistant to clindamycin and dicloxacillin. Cefazolin showed good activity. Cephalexin, cephradine, and cefadroxil showed poor activity, and cefamandole's activity was relatively poor. Cephalothin, cephapirin, cefaclor, and cephaloridine showed moderate activity, with some strains relatively resistant.

Bacteroides↗

Antibiotic susceptibility of Neisseria gonorrhoeae strains from Europe and Africa.

The in vitro activities of 16 antimicrobial agents were tested by a plate dilution method against 268 unselected isolates of Neisseria gonorrhoeae from Belgium, Rwanda, Swaziland, and Zaire. Fifteen beta-lactamase-producing strains isolated in Europe from various origins were also tested. There were significant regional variations in antimicrobial agent susceptibility, even among the African isolates, with the Rwandan and Zairean strains being most resistant. Benzylpenicillin and ampicillin were equally active in all but the beta-lactamase-producing strains. Among the cephalosporins, cefotaxime was by far the most active, followed by cefuroxime, cefamandole, cefoxitin, and cefaclor, in that order. All strains were susceptible to spectinomycin, thiamphenicol, kanamycin, and rifampin, with the exception of one highly rifampin-resistant isolate and a moderately thiamphenicol-resistant strain. Twenty-six percent of the isolates were highly resistant to streptomycin. Six percent of the gonococci had a minimal inhibitory concentration for tetracycline greater than 2 mug/ml. Clavulanic acid inhibited the beta-lactamase activity of the gonococci tested and improved markedly the activities of ampicillin and amoxicillin against beta-lactamase-producing strains.

Africa↗

Antibiotic susceptibility of beta-lactamase-producing strains of Branhamella (Neisseria) catarrhalis.

All 11 clinically significant isolates of Branhamella catarrhalis examined in this study were found to produce beta-lactamase. The enzyme was apparently not plasmid associated since extrachromosomal deoxyribonucleic acid was not detected in any of the strains. The beta-lactamase activity of all strains was significantly depressed by the beta-lactamase inhibitors clavulanic acid and CP 45899. Based on comparisons of relative susceptibility to various beta-lactam antibiotics, it was inferred that the beta-lactamase of B. catarrhalis was significantly more active against penicillin congeners than against cephalosporin congeners. Most strains were not inhibited by readily achievable serum concentrations of the pencillinase-sensitive penicillins, penicillin G, ampicillin, and amoxicillin. Methicillin was equally ineffective. With rare exceptions, most strains of B. catarrhalis were inhibited by achievable serum concentrations of seven cephalosporins (cephalothin, cephapirin, cephaloridine, cephalexin, cephamandole, cefaclor, and cefuroxin) and one cephamycin (cefoxitin). All strains were uniformly resistant to clindamycin but were inhibited by achievable serum concentrations of erythromycin, tetracycline, chloramphenicol, and trimethoprim-sulfamethoxazole. Comparison of geometric mean minimum inhibitory concentrations of all antimicrobial agents tested suggested that B. catarrhalis was most susceptible to cefoxitin, erythromycin, and tetracycline.

Anti-Bacterial Agents↗

Activity of ten cephalosporins on biomass of methicillin-susceptible and -resistant Staphylococcus aureus.

The growth curves automatically recorded and printed during the action of 10 cephalosporins on methicillin-susceptible and methicillin-resistant Staphylococcus aureus showed the following. (i) The biomass of methicillin-susceptible S. aureus exposed to the cephalosporins increased before lysis occurred (inoculum, 10(6) colony-forming units per ml). Lysis was more rapid with cephalothin and cephaloridine, whose minimal inhibitory concentrations were lowest. (ii) The same biomass increase followed by lysis occurred with methicillin-resistant S. aureus, and the speed of lysis was not different from those of cephalothin (without any regrowth), cefoxitin (with regrowth of a few strains), and cephaloridine (regrowth of all strains), with methicillin-susceptible strains. A 2-log increase of inoculum (10(8) colony-forming units per ml) did not modify significantly the speed of lysis with cephalothin, cephaloridine, and cefoxitin, but regrowth sometimes occurred. The early transitory lysis caused by cephaloridine, cephalothin, cefamandole, and cefoxitin was not suppressed by preincubation with 32 mug of methicillin per ml, but regrowth occurred more frequently. No lysis could be observed with cefazolin, cefotaxime, cephalexin, cephradine, cefuroxime, and cefaclor unless high concentrations were achieved. (iii) From a practical point of view, the early response of the growth curve (4 h) could not determine in every case whether a strain of S. aureus was resistant or susceptible to cephalosporin. A further study of the growth curve (18 of 24 h) was necessary for this purpose. Results obtained after a few hours with automated systems should be interpreted with great caution.

Cephalosporins↗

In vitro susceptibility of Capnocytophaga strains to 18 antimicrobial agents.

Twenty-seven strains of capnocytophaga were tested for their susceptibility to 18 antimicrobial agents by an agar dilution technique. All strains were susceptible to achievable blood levels of penicillin G, cefaclor, cefoxitin, cefoperazone, moxalactam, clindamycin, chloramphenicol, and tetracycline. Most were susceptible to achievable levels of cefamandole, erythromycin, and metronidazole, and more than 10% were resistant to achievable levels of cephalexin and cephradine. With antimicrobial agents used in selective media, all strains were resistant to colistin, kanamycin, and nalidixic acid at commonly recommended concentrations of bacitracin and vancomycin.

Anti-Bacterial Agents↗

Pharmacokinetics of cefadroxil after oral administration in humans.

The human oral pharmacokinetics of cefadroxil were studied in parallel at doses of 250, 500, and 1,000 mg in three groups of 10 healthy young male volunteers. Renal excretion of intact cefadroxil, accounted for 82, 79, and 77% of the above doses. Mean peak serum levels were dose linear: 9, 18, and 35 microgram/ml at 250, 500, and 1,000 mg, respectively. However, overall pharmacokinetics were linear only in the 250- to 500-mg dose range; apparent serum clearances were 10 liters/h, and true renal clearances were 9 and 8 liters/h at 250 and 500 mg. At 1,000 mg, apparent serum clearance dropped to about 7 liters/h, true renal clearance, dropped to 6 liters/h, and the area under the curve increased disproportionately. At 250 and 500 mg, mean half-life was about 1.2 h; at 1,000 mg, however, it was 1.6h. The nonlinear decrease in clearance could be related to saturation of active renal tubular secretion of cefadroxil between the 500- and 1,000-mg doses. Previous results indicating that cefadroxil has greater persistence than other oral cephalosporins such as cephalexin, cephradine, cefaclor were confirmed.

Administration, Oral↗

In vitro activity of Bay 09867, a new quinoline derivative, compared with those of other antimicrobial agents.

The in vitro activity of Bay 09867, a new quinoline derivative, was compared with those of norfloxacin, nalidixic acid, ceftazidime, cefaclor, cefuroxime, gentamicin, and other antimicrobial agents, when appropriate, against 410 recent clinical isolates. The minimal inhibitory concentrations of Bay 09867 for 90% of Enterobacteriaceae, Pseudomonas aeruginosa, Haemophilus influenzae, Neisseria gonorrhoeae, streptococci, Staphylococcus aureus, and Bacteroides fragilis strains were between 0.008 and 2 micrograms/ml. Bay 09867 was considerably more active against the gram-negative bacteria tested than were other agents tested. Gentamicin-resistant Enterobacteriaceae, P. aeruginosa, and methicillin-resistant S. aureus were highly susceptible to Bay 09867. Strains less susceptible to nalidixic acid and norfloxacin tended to be less susceptible to Bay 09867. The protein binding of Bay 09867 was about 20%.

Anti-Bacterial Agents↗

High-pressure liquid chromatographic method for analysis of cephalosporins.

A high-pressure liquid chromatographic method is described for the analysis of a wide range of cephalosporin congeners, using only three reagents for extraction and drug analysis. Plasma was treated with cold methanol-0.1 M sodium acetate to precipitate protein. Cephalosporins were resolved on a C-18 reverse-phase column, utilizing a mobile phase of various percentages of 0.01 M sodium acetate and acetonitrile-methanol. Compounds analyzed included cephalexin, cefamandole, cephalothin, cefotaxime, cefazolin, cephaloridine, cefoxitin, cefaclor, cephapirin, and cefoperazone. Each antibiotic demonstrated excellent linearity throughout the therapeutic range. The method of standard additions revealed recoveries of 93 to 101%, with detection limits ranging from 0.2 to 1.0 micrograms/ml for these drugs. Retention times ranged from 4 to 6 min. This method offers a rapid and simple means by which this group of cephalosporins may be reliably quantitated.

Cephalosporins↗