Antimicrobial activity of carbapenem antibiotics against gram-negative bacilli

Antimicrobial activities of meropenem (MEPM), imipenem (IPM), panipenem (PAPM), ceftazidime (CAZ), cefozopran (CZOP), aztreonam (AZT), norfloxacin (NFLX) and tetracycline (TC) against clinically isolated Gram-negative bacilli [271 strains of Enterobacteriaceae and 242 strains non-fermentative Gram-negative bacteria (NFB)] were investigated. Among carbapenem antibiotics, MEPM showed the lowest MIC90, which activity was about four-hold higher than those of IPM and PAPM. The activity of IPM was equal or slightly superior to that of PAPM. Resistance to IPM (> 16 micrograms/ml) was observed in 3 strains of Enterobacteriaceae (1.1%) and 14 strains of NFB (5.8%). It is conceivable that these strains produce metallo-beta-lactamase. Referring to the correlation among MICs of MEPM, IPM and PAPM, 3 strains in 3 species of Enterobacteriaceae showed cross resistance to carbapenems; while 14 strains of NFB showed cross resistance to MEPM and IPM, 15 strains to MEPM and PAPM, and 29 strains to IPM and PAPM, and all of these strains were Pseudomonas aeruginosa. Fifteen of 29 strains of IPM-resistant and 77 of 92 strains of PAPM-resistant P. aeruginosa were susceptible to MEPM. Thirty-three strains (12%) of the Enterobacteriaceae were resistant to CAZ and AZT (> or = 32 micrograms/ml) and these were considered as ESBL-producing strains.     

Antimicrobial activity of macrolides against clinical isolates

Antimicrobial activity of 6 macrolides was determined using a micro-broth dilution method, against 535 clinical isolates of 22 species, which were isolated in 1996 from 325 facilities in Japan. Results were as follows. 1. In general, antimicrobial activities of 14-membered macrolides were higher than those of 16-membered macrolides. The antimicrobial activities of 14-membered macrolides were in the order of clarithromycin (CAM), erythromycin (EM), roxithromycin (RXM). Among 16-membered macrolides, rokitamycin (RKM) was the most potent, josamycin (JM) was next potent followed by midecamycin (MDM). More numbers of highly-resistant strain of > 100 micrograms/ml were recognized in 14-membered macrolides than in 16-membered macrorides. 2. Most of S. pyogenes (group A) strains were distributed in the susceptible range and almost none was found in the resistant range. 3. S. pneumoniae strains were distributed widely from the susceptible range to the highly resistant range, and as high as 37.1% fell into the high resistance of > 100 micrograms/ml range. 4. Against Peptostreptococcus spp. and MRSA, 16-membered macrolides were more effective than 14-membered macrorlides, and their antibacterial activities were in the order of RKM, JM, MDM. Ratio of high-resistant strains of > 100 micrograms/ml against 14-membered macrolides was much higher than that against 16-membered macrolies. 5. Most of M. (B.) catarrhalis strains were distributed in the susceptible range of < or = 1.56 micrograms/ml, and most of H. influenzae strains were distributed within the moderately resistant and the resistant ranges. 6. In M. (B.) catarrhalis and H. influenzae, no correlation between macrolide resistance and beta-lactamase production was recognized. 7. Most of C. jejuni strains were susceptible to all macrolides used in this study.     

Comparison of the in vitro activity of several cephalosporin antibiotics against gram-negative and gram-positive bacteria resistant to cephaloridine

The in vitro activity of each of two oral [cefatrizine (BL-S640), cephalexin] and three parenteral (cefamandole, cefazolin, cephapirin) cephalosporin antibiotics was compared with that of cephalothin against 168 clinical isolates of gram-negative and gram-positive bacteria selected as resistant to 20 mug of cephaloridine per ml on the basis of agar dilution susceptibility test data. Each of the five other cephalosporins inhibited a greater percentage of gram-negative bacillary isolates than did cephalothin or cephaloridine, with minimal inhibitory concentration values ranging 2- to 50-fold lower. Significant differences between minimal inhibitory concentrations of the compounds tested were also observed in tests against strains of Streptococcus faecalis and of methicillin-resistant Staphylococcus aureus. Potential advantages of including more than a single cephalosporin antibiotic in the panel of antibiotics used for routine susceptibility testing, suggested by these observations, are discussed.     

In vitro antimicrobial activity of fluoroquinolones against clinical isolates obtained in 1989 and 1990

The in vitro activity of nine fluoroquinolones, enoxacin, norfloxacin, ofloxacin, ciprofloxacin, lomefloxacin, tosufloxacin, sparfloxacin, fleroxacin and levofloxacin, and two earlier quinolones, nalidixic acid and pipemidic acid, against 1,346 bacterial strains isolated clinically between 1989 and 1990, was evaluated by agar dilution method. The bacteria studied were Staphylococcus aureus (including methicillin-susceptible and -resistant strains), Staphylococcus epidermidis, Enterococcus species (including high-level gentamicin-resistant strains), Escherichia coli, Salmonella species, Proteus mirabilis, Proteus vulgaris, Morganella morganii, Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens, Citrobacter spp., Pseudomonas aeruginosa, Pseudomonas cepacia, Acinetobacter baumannii, and Bacteroides fragilis. In contrast to the moderate to poor activity of two earlier quinolones, the fluoroquinolones acted well against most Enterobacteriaceae and A. baumannii. The minimum inhibitory concentrations for 90% of the drug strains (MIC90s) were < 1 microgram/mL against most tested species. Ciprofloxacin, tosufloxacin, sparfloxacin, and levofloxacin were more effective against multi-drug-resistant nosocomial pathogens. All fluoroquinolones assayed were very active against methicillin-susceptible S. aureus, with MIC90s < or = 1 microgram/mL. For methicillin-resistant strains, on the other hand, the MIC90s were > or = 4 micrograms/mL. There was no significant difference in fluoroquinolone susceptibility between methicillin-susceptible and -resistant S. epidermidis. Sparfloxacin, tosufloxacin, ciprofloxacin and levofloxacin were more active against enterococci. Most fluoroquinolones were relatively inactive against B. fragilis, with the exception of tosufloxacin, sparfloxacin and levofloxacin. The MIC90s of most quinolones assayed against K. pneumoniae, Citrobacter spp., E. cloacae, S. aureus and S. epidermidis were at least four-fold higher in our study. Therefore, it is important for physicians to use fluoroquinolones carefully so as to prevent or delay the emergence of resistant strains.     

In vitro activity of the new glycopeptide LY333328 against multiply resistant gram-positive clinical isolates

In order to assist the medical team in the decision-making process and in adequate counselling of patients when encountering technical difficulties at the time of embryo transfer, we investigated the effect of difficult embryo transfer, with or without the need for cervical dilatation or repeated sequential attempts because of retained embryos in the catheter system, on in-vitro fertilization (IVF) pregnancy rates and outcome. A total of 854 consecutive embryo transfer procedures were prospectively categorized as (i) easy (smooth, unforced), (ii) difficult (requiring uterine manipulation or increased force or cervical grasping and/or accompanied by trauma), (iii) requiring cervical dilatation, or (iv) multiple (two or three) sequential attempts because of embryos retained in the catheter system. Embryo transfer was easy in 734 cases (85.9%). It was difficult in 72 (8.4%), cervical dilatation was required in 21 (2.5%), and one or two repeated attempts were needed in 27 cases (3.2%). Pregnancy rates for the different categories of embryo transfer were 23.3, 23.6, 23.8 and 29.6% respectively. There were no significant differences in the percentage of the ongoing/delivered pregnancies for the different categories of embryo transfer (69, 64.6, 60 and 62.5% respectively). There were no significant differences in the distribution of embryo transfer types among the six infertility specialists who performed the procedures. To conclude, embryo transfers that are difficult to perform or that require cervical dilatation or repeated attempts do not adversely affect pregnancy rates and outcome following IVF. Cervical dilatation, if needed for patients with cervical stenosis, should be performed at the time of the embryo transfer and not earlier. Surgical transmyometrial embryo transfer or rescheduling patients for delayed embryo transfer could be avoided in most patients. This information is important for patient management and counselling in cases of embryo transfer that are not easy to perform.     

Repression of catabolites in gram-positive and gram-negative bacteria

Analyzes the mechanism of catabolite repression of grampositive and gramnegative bacteria. The role of cyclic adenosine monophosphate and CRP protein, forming a complex, is shown. Contribution of ATP kinase to manifestation of the catabolic repression phenomenon in grampositive bacteria is discussed.     

Antimicrobial activity of ofloxacin against recent clinical isolates from otitis media and otitis externa]

In order to evaluate the annual changes of susceptibility, minimum inhibitory concentrations (MICs) of ofloxacin (OFLX) and 4 control drugs were determined against clinical isolates that were obtained from patients with otitis media and otitis externa during the periods between January and December 1993, and the periods between October 1996 and March 1997. The results are summarized as follows: 1. No annual changes were seen for MIC50 of OFLX, but MIC80 and MIC90 of that rose against methicillin-resistant Staphylococcus aureus (MRSA), coagulase-negative staphylococci (CNS) and Pseudomonas aeruginosa from 1993 to 1996. It appears that resistance to OFLX is increasing among these bacteria. Detection frequency of highly resistant strains to OFLX (MIC > 100 micrograms/ml) was lower than to other control drugs. 2. No annual changes were seen of MIC50, MIC80 and MIC90 of OFLX against methicillin-susceptible S. aureus (MSSA), Streptococcus spp., Proteus spp. and Haemophilus influenzae. OFLX showed strong antimicrobial activities against these bacteria. 3. Since there was no large annual changes in the antimicrobial activity of OFLX against clinical isolates that were obtained from patients with otitis media and otitis externa, OFLX otic solution was considered as one of the clinically useful drugs even now.     

Antimicrobial activities of ciprofloxacin against recently obtained clinical isolates

In order to evaluate antimicrobial activity of ciprofloxacin (CPFX), minimum inhibitory concentrations (MICs) of CPFX and other drugs were determined against clinical isolates that were obtained in our laboratory from January to December of 1991, and of 1993. The results are summarized as follows: 1. CPFX-resistant strains were on the increase in various strains, compared to those in the early 1980s. However, many of CPFX-resistant strains were multi-drug resistant including beta-lactams. In addition, they showed cross resistance to other fluoroquinolone agents. 2. MIC distribution of other drugs suggested that there were increased frequencies of benzylpenicillin (PCG)-insensitive Streptococcus pneumoniae (PISP) and CEPs-resistant Escherichia coli. However, MIC distribution of CPFX to these resistant strains were in a relatively low range. 3. When isolates of 1991 were compared to those of 1993, we confirmed that CPFX-resistant strains decreased among certain bacteria such as Staphylococcus aureus. Also we confirmed that fewer CPFX-resistant strains were found among bacteria that may be highly related to infections encountered in daily medical care.     

In vitro activity of 9 antibiotics and 3 beta-lactamase inhibitors against 107 clinical isolates of Acinetobacter baumanii

Twenty eight of 227 patients undergoing restorative proctocolectomy for inflammatory bowel disease, familial adenomatous polyposis or functional disease were over the age of 50 years: ages 50 to 60 (n = 13), 60 to 70 (n = 10), and over 70 (n = 5). Major complications occurred in 5 patients over the age of 50 (18%) compared with 43 patients under the age of 50 (23%). Three patients above the age of 50 had their pouch excised (11%) compared with 23 under the age of 50 (12%). Functional outcome was assessed with a 12 point symptom score. This was similar in all age bands: under 50 years (mean = 2.2; sd +/- 2.2; n = 109), 50 to 60 years (mean = 2.5; sd +/- 2.5; n = 12), 60 to 70 years (mean = 2.8; sd +/- 2.3; n = 7) and over 70 years (mean = 4.0; sd +/- 3.7; n = 5): P > 0.05). When analysed for ulcerative colitis alone, no significant differences were seen between the two age groups. Restorative proctocolectomy in the elderly gives results which are comparable to the younger population.     

Complement activation in septic shock due to gram-negative and gram-positive bacteria

Whole serum complement (CH50) and C3, C4, and C3PA plasma values were studied in 48 patients: 9 with nonseptic shock; 20 with sepsis; 14 with septic shock caused by gram-negative bacteria; 5 with septic shock caused by gram-positive bacteria. All were compared with a control group of 25 healthy individuals. Determinations were made upon admission and again 48 and 96 h later. No significant differences in complement values were found between the patients with nonseptic shock and the control group. In the patients with sepsis, decreased CH50 (p less than 0.001) and increased C3PA (p less than 0.02) values were observed, while C3 and C4 remained unaltered. In the patients with septic shock, markedly decreased levels of CH50, C3, and C4 were seen (p less than 0.001, and p less than 0.001, and p less than 0.001, respectively) without changes in C3PA levels. There were no differences between septic shock due to gram-negative and gram-positive bacteria, or between patients who died and those who survived. After 96 h, the altered values returned to the normal range. This underlines the transitory activation of the complement system through the classic pathway and suggests its possible role in the pathogenesis of septic shock in man.     

Evaluation of antibacterial activities of various antibiotics against glucose non-fermentative gram-negative rods other than Pseudomonas aeruginosa

MICs of piperacillin, sulbactam/cefoperazone, minocycline (MINO), gentamicin, amikacin, flomoxef, ceftazidime, cefozopran, cefsulodin and imipenem were determined, against 189 clinical isolated strains of glucose non-fermentative Gram-negative Rods (NFGNR; Acinetobacter baumannii (44), Alcaligenes faecalis (5), Alcaligenes xylosoxidans (25), Burkholderia cepacia (12), Chryseobacterium indologenes (23), Chryseobacterium meningosepticum (9), Pseudomonas fluorescens (8), Pseudomonas putida (12), Stenotrophomonas maltophilia (51). Most species of these NFGNR show resistance to many antibiotics tested. Among the antibiotics used in this study, the only antibiotic effective against all species of NFGNR tested is MINO. The spectrums of antibacterial activities of various antibiotics determined by MICs may be useful in preliminary test for identification of these NFGNR.     

Use of clinical parameters for differentiation of gram-positive and gram-negative mastitis in dairy cows vaccinated against lipopolysaccharide core antigens

OBJECTIVE: To determine whether clinical parameters could be used to differentiate clinical mastitis (CM) caused by gram-positive bacteria from CM caused by gram-negative bacteria in dairy cows vaccinated against lipopolysaccharide core antigens. DESIGN: Case series. ANIMALS: 143 episodes of CM in 86 dairy cows in a single herd. PROCEDURE: Cows were examined at onset of CM, and 24 clinical parameters including rectal temperature, heart rate, rumen contraction rate, degree of dehydration, various udder and milk characteristics, lactation number, stage of lactation, and season of year were recorded. Milk production and milk constituent concentrations before onset of CM were obtained from Dairy Herd Improvement Association records. Values for cows with gram-negative CM were compared with values for cows with gram-positive CM. Logistic regression was used to identify important predictors of gram-negative CM. RESULTS: 64 (45%) CM episodes were caused by gram-negative bacteria and 79 (55%) were caused by gram-positive bacteria. Rumen contraction rate was significantly lower and milk protein percentage before onset of CM was significantly higher in cows with gram-negative, rather than gram-positive, CM. Logistic regression indicated that CM was more likely to have been caused by gram-negative bacteria if it developed during the summer, milk was watery, or rumen contraction rate was low. Sensitivity and specificity of the final regression model were 0.58 and 0.80, respectively. Predictive value of a positive result was 0.74 when proportion of CM episodes caused by gram-negative bacteria was assumed to be 50%. CLINICAL IMPLICATIONS: Results suggest that clinical observations do not allow accurate prediction of CM pathogens and should not be the sole criteria for deciding whether cows with CM are treated with antibiotics.     

In vitro activities of the ketolide HMR 3647 against recent gram-positive clinical isolates and Haemophilus influenzae

The ketolide HMR 3647 (previously RU 66647) was evaluated against 2, 563 recent clinical isolates of gram-positive pathogens and 200 Haemophilus influenzae isolates. HMR 3647 was active against macrolide-resistant streptococci, including pneumococci, but was not active against macrolide- or lincosamide-resistant staphylococci. Against H. influenzae, the potency of HMR 3647 was similar to that of azithromycin.     

Klebsiella pneumoniae clinical isolates: susceptibility to some antibiotics and surface hydrophobicity

The susceptibility of Klebsiella pneumoniae strains isolated from the respiratory tract (55), urinary tract (19) and other human body sites (8) to the antibiotics, amoxycillin/clavulanate, cefuroxime, ceftazidime, gentamicin, norfloxacin, colistine, cotrimoxazole and oxolinic acid, as well as their surface hydrophobicity, were studied. The strains expressed a very high sensitivity to the antibiotics (94.7-100%). The surface hydrophobicity of the strains was evaluated by means of three assays and was minimal. The hydrophobicity manifested by adherence to xylene ranged between 0 and 10% for 96.4% of the respiratory strains, and for 100% of the urinary and other sites. Weak binding of Congo red (10-29 micrograms/10(10) cells) showed 96.4% of respiratory isolates as well as 100% of the urinary and other strains. Results of the salt aggregation test showed that 96.4% of respiratory strains and 100% of urinary and other strains aggregated only at 1.5 M, 2 M or higher concentrations.     

Antimicrobial properties of pectins and their effects on antibiotics

The influence of food fibres and plant proteins on microorganisms, bacteriophages, antibiotics and penicillinase was studied in vitro. It was shown that pectin was the only agent that had a bactericidal effect on the most widely distributed pathogenic and opportunistic microorganisms and did not influence indigenic microflora. High concentrations of pectin (> 2 per cent) had an inactivating effect on therapeutic bacteriophages. There was also a decrease in the antimicrobial activity of penicillins. The other agents tested i.e. wheat bran, soya isolate and soybean flour had no influence on microorganisms, bacteriophages and antibiotics. No sorption activity of the food fibres and plant proteins with respect to microorganisms and antibiotics or their effect on penicillinase was observed.     

Characterisation of DNA gyrase and measurement of drug accumulation in clinical isolates of Acinetobacter baumannii resistant to fluoroquinolones

Twelve clinical isolates of Acinetobacter baumannii highly resistant to pefloxacin (MIC > or = 32 mg/L) and to ciprofloxacin (MIC > or = 16 mg/L), were studied. A susceptible isolate used as a reference (MIC of 0.032 and 0.25 mg/L for ciprofloxacin and pefloxacin, respectively) accumulated 85 mg of pefloxacin per litre of cell volume within 10 min, from a solution containing 10 mg/L of antibiotic. One resistant isolate accumulated the same amount of pefloxacin, while the 11 others accumulated between 40 and 70 mg/L of cell volume. The differences between reference and resistant isolates with respect to ciprofloxacin and sparfloxacin accumulation were less pronounced. There were no apparent differences in the outer membrane protein profiles of susceptible and resistant isolates. DNA gyrase was isolated from four A. baumannii and the minimum concentration of fluoroquinolones, required to inhibit gyrase-catalysed supercoiling of plasmid DNA was 5- to 80-fold higher for the resistant isolates than for the reference strain. Although most isolates showed some degree of reduced fluoroquinolone accumulation, a DNA gyrase mutation was more likely to be the main mechanism of the high level resistance encountered.