Importance of penicillinase production for activity of penicillin alone or in combination with sulbactam in experimental endocarditis due to methicillin-resistant Staphylococcus aureus

The activity of penicillin, alone and in combination with sulbactam, against a heterogeneously methicillin-resistant, penicillinase-producing clinical isolate of Staphylococcus aureus and its penicillinase-negative derivative was investigated in vitro and in a rabbit experimental endocarditis model. Penicillin was significantly more effective than vancomycin against the penicillinase-negative derivative in vivo (P < 0.001), and it sterilized 25% of the vegetations. The combination of penicillin and sulbactam exhibited an in vivo synergistic effect on the penicillinase-producing strain (P < 0.01) but did not produce any advantage over treatment with vancomycin, even when a high dose of sulbactam was used (100 mg/kg of body weight every 6 h). This combination was significantly less effective against the penicillinase-producing strain than was penicillin alone against the penicillinase-negative derivative (P < 0.03). In addition, the most resistant subpopulation of the surviving bacteria, which grew on agar containing 16 micrograms of methicillin per ml, was detected in 5 of 6 animals treated with penicillin and a high dose of sulbactam against the penicillinase-producing strain compared with only 1 of 12 animals treated with penicillin alone against the penicillinase-negative derivative (P < 0.01). We conclude that penicillin is highly effective against penicillinase-negative methicillin-resistant S. aureus and that penicillinase production, rather than methicillin resistance, appears to be the limiting factor for the activity of the penicillin-sulbactam combination against penicillinase-producing, methicillin-resistant S. aureus.

[Kinetics of bactericidal activity of cefepime and cefpirome alone or combined with gentamicin, amikacin or ciprofloxacin against Acinetobacter baumannii, Stenotrophomonas maltophilia and Enterobacter cloacae hyperproductive in cephalosporinase]

Nosocomial infections encountered in intensive care units are frequently due to Gram negative bacilli among which Stenotrophomonas maltophilia, Acinetobacter sp., and Enterobacter sp. The aim of the present study was to evaluate the in vitro bactericidal activity of the new broad spectrum cephalosporins cefepime (FEP) and cefpirome (CPO) alone or in combination with amikacin (AKN), gentamicin (GTN) or ciprofloxacin (CIP) against Acinetobacter baumannii, Stenotrophomonas maltophilia and Enterobacter cloacae producing a derepressed cephalosporinase. This study was performed by using the time-kill curve method on 24 h with a starting inoculum of 10(6) - 10(7) cfu/ml. The combination of FEP (4 mg/l) with AKN (4 mg/l) against A. baumanii only results in about 1 log decrease at 24 h, but when FEP is combined at 8 mg/l, the decrease reaches 4 log in 24 h. The combination of FEP (16 and 32 mg/l) clavulanic acid (4 mg/l) resulted in 3 log decrease at 24 h. When combined with CIP 2 mg/l, FEP (16 and 32 mg) resulted in 5 and 6 log decrease in 24 h respectively. There were no survival bacteria at 6 h when FEP (32 mg/l) was combined with clavulanic acid (4 mg/l) and GTN (8 mg/l) at 6 h. Used alone FEP (1 mg/l) or CPO (1 mg/l) against E. cloacae, a 3 log decrease occurs at 6 h followed by a regrowth at 24 h. Combined with AKN (2 mg/l), FEP (1 mg/l) results in a 6 log decrease at 24 h, when CPO at 2 mg/l is needed for an equivalent result. These data show synergistic bactericidal activity of both new extended cephalosporins combined with AKN, GTN or CIP at concentrations achievable in biological fluid with adaptative dosage regimen.

[Comparison of the activity of beta-lactams against Pseudomonas aeruginosa according to phenotypes of resistance]

The in vitro activity of ticarcillin, ticarcillin-clavulanic acid, piperacillin, piperacillin-tazobactam, cefsulodin, ceftazidime, cefepime, cefpirome and aztreonam was evaluated against 130 isolates of Pseudomonas aeruginosa with various beta-lactam phenotypes. MICs were determined by the agar dilution method and inhibition method and inhibition zones by the disk test. The resistance mechanisms were characterized by the iodometric method. The activity of cefepime was greater than that of cefpirome whatever the resistance phenotype. Some ticarcillin-susceptible strains were intermediate to cefepime and cefpirome. Most strains with a penicillinase or "intrinsic resistance" phenotype were susceptible to ceftazidime but intermediate to cefepime and cefpirome. Only 10% of cephalosporinase-over-producing strains remained susceptible to cefepime.

Ticarcillin/clavulanic acid: determination of minimal inhibitory concentrations against bacterial strains isolated from patients in intensive care units. Comparison with other agents

A total of 303 bacterial strains isolated from bronchoaspirates of Intensive Care Unit (ICU) patients, collected through June and December 1993, were tested for susceptibility to ticarcillin/clavulanic acid, imipenem, amikacin, ceftazidime, ciprofloxacin and piperacillin. The minimal inhibitory concentration (MIC) for each antibiotic was determined according to the NCCLS, by means of serial dilution on microplates. The isolates, 80.8% of which were beta-lactamase producing strains, belonged to Pseudomonas aeruginosa (79 strains), Pseudomonas fluorescens (8 strains), Xanthomonas maltophila (25 strains), Escherichia coli (16 strains), Klebsiella-Enterobacter-Serratia (KES) (62 strains), Proteus spp. (15 strains), Acinetobacter spp. (22 strains), Moraxella spp. (15 strains), Bacteroides catarrhalis (8 strains), Haemophilus spp. (11 strains), Staphylococcus aureus (32 strains), Enterococcus faecalis (10 strains). The highest rate of susceptibility to ticarcillin/clavulanic acid (100%) was detected among E. faecalis (MIC 2-16 micrograms/ml), B. catarrhalis (MIC 1-4 micrograms/ml) and Haemophilus spp. (MIC 1-4 micrograms/ml). Among the non-fermenting microorganisms ticarcillin/-clavulanic acid showed good activity toward P. aeruginosa and P. fluorescens (86% and 75% respectively). It was also very active against X. maltophilia with a susceptibility of 96%. Susceptibility to the other antibiotics tested was within the range of 16% and 28%.

Convulsions in childhood shigellosis and antimicrobial resistance patterns of shigella isolates

Drug resistance patterns of 68 shigella strains were investigated prospectively in Kayseri during a period of approximately two years. The resistance was highest with ampicillin (58.8%) followed by co-trimoxazole (50%) and ampicillin-sulbactam (13%). Only 2.8 percent of cases were resistant to gentamicin, and all serogroups were sensitive to ceftriaxone. We conclude that in children with severe shigellosis, treatment with ceftriaxone is effective and better than ampicillin and co-trimoxazole for obtaining a clinical cure. We followed 18 children who experienced convulsions associated with shigellosis. Only one child had a history of febrile convulsions, and two children had histories of convulsive disorders. The majority of the children had generalized, self-limited convulsions which lasted less than ten minutes. Due to the benign and self-limited nature of most of the convulsions, neither diagnostic procedures nor drug therapy are usually necessary. These measures should, however, be considered in complicated cases characterized by focal or prolonged seizures.

In vitro activity of metronidazole alone and in combination with clotrimazole against clinical isolates of Trichomonas vaginalis

Trichomonas vaginalis vaginitis is generally treated with oral metronidazole. Widespread use of this drug has led, however, to selection of resistant strains. Topical therapy seems appropriate whenever systemic high dosage schedule cannot be adopted in order to overcome resistance. This study was designed to assess the activity of metronidazole alone and in combination with clotrimazole, an imidazole derivative for topical use, against T. vaginalis. Tests were performed employing the antitrichomonas activity of a fixed ratio of metronidazole with clotrimazole (5:1) which has been recently suggested for topical therapy and the checkerboard technique. All tests were carried out under aerobic conditions to maximize T. vaginalis resistance traits. Minimum inhibitory concentrations (MICs) of metronidazole for the 12 strains studied were in the range reported in the literature (0.5-32 micrograms/ml). The interaction of metronidazole with clotrimazole as assessed by the checkerboard technique gave an indifferent outcome with all the strains assayed (FIC = 1-2). The fixed concentration of drugs, however, produced synergism (FIC = 0.5) in 5 of 12 isolates. Spontaneous resistant strains were not selected from T. vaginalis exposed to sub-lethal levels of the drugs or by culturing a large inoculum in the presence of 1, 2, 4 and 8 times the MICs of metronidazole alone or in combination with clotrimazole. These results confirm and extend previous reports highlighting the good in vitro efficacy of the association of metronidazole plus clotrimazole against T. vaginalis.

Unorthodox antibiotic combinations including ciprofloxacin against high-level gentamicin resistant enterococci

Development of high-level gentamicin resistance among enterococci represents a serious therapeutic problem as it precludes synergy between aminoglycosides and cell-wall active agents. As part of a search for active antibiotic combinations against enterococci with high-level gentamicin resistance, we tested by the time kill curve method the efficacy of ciprofloxacin combined with ampicillin, trimethoprim-sulphamethoxazole, vancomycin or teicoplanin against ten isolates of Enterococcus faecium, three of Enterococcus casseliflavus and 13 of Enterococcus faecalis that exhibited a MIC of gentamicin > or = 2000 mg/L. Most of the E. faecium were also resistant to ampicillin and to ciprofloxacin. The combination of ciprofloxacin with ampicillin was bactericidal against five of seven E. faecium strains that exhibited a ciprofloxacin MIC < or = 4 mg/L, but was inactive against the three E. faecium that were highly resistant to ciprofloxacin. This combination was also bactericidal against the E. casseliflavus and all the E. faecalis strains. The combination of ciprofloxacin with trimethoprim-sulphamethoxazole was bactericidal against five of the seven E. faecium and seven of the nine E. faecalis strains with a ciprofloxacin MIC < or = 4 mg/L. No bactericidal activity of this combination was seen against the enterococci that were highly resistant to either ciprofloxacin or to trimethoprim-sulphamethoxazole. The combination of ciprofloxacin with glycopeptides was inactive against E. faecium and E. casseliflavus and against E. faecalis, it was either ineffective or antagonistic; in only one case it was bactericidal. Five strains of E. faecium were resistant to all antibiotic combinations tested.

[In vitro activities of sulopenem, a new parenteral penem, against anaerobes]

In vitro activities of sulopenem, a novel parenteral penem, was compared with those of imipenem, flomoxef, cefuzonam, cefoperazone and sulbactam/ampicillin against 66 reference strains (19 genera, 61 species) and 392 recent clinical isolates of anaerobic bacteria and fastidious aerobic bacteria. Sulopenem had a very broad spectrum against anaerobic bacteria. In general, this compound was active against anaerobic reference strains with MICs of < or = 0.78 micrograms/ml, while being the least active against Bifidobacterium spp. and less active than imipenem against Lactobacillus spp. Sulopenem was more active against Bacteroides fragilis isolates than imipenem and had the highest activities against Bacteroides thetaiotaomicron, Prevotella intermedia, Porphyromonas gingivalis, Fusobacterium spp. and Peptostreptococcus spp. among the antibiotics tested. Sulopenem was not hydrolyzed by oxyiminocephalosporinase type 1 produced by B. fragilis GAI-0558, GAI-7955 and GAI-10150 and its stability was comparable to imipenem. Its susceptibilities to hydrolysis by a metallo-beta-lactamase from B. fragilis GAI-30144 was less than imipenem. Sulopenem (120 mg/kg, 3 times a day for 4 days) was as effective as imipenem/cilastatin against a mixed intraabdominal mice infection due to E. coli and B. fragilis. Sulopenem (20 mg/kg twice a day for 5 days) did not induce an overgrowth of Clostridium difficile in the caecum of mice.

Susceptibilities of non-Pseudomonas aeruginosa gram-negative nonfermentative rods to ciprofloxacin, ofloxacin, levofloxacin, D-ofloxacin, sparfloxacin, ceftazidime, piperacillin, piperacillin-tazobactam, trimethoprim-sulfamethoxazole, and imipenem

Agar dilution MICs of 10 agents against 410 non-Pseudomonas aeruginosa gram-negative nonfermentative rods were determined. MICs at which 50 and 90% of the isolates were inhibited, respectively, were as follows (in micrograms per milliliter): sparfloxacin, 0.5 and 8.0; levofloxacin, 1.0 and 8.0; ciprofloxacin, 2.0 and 32.0; ofloxacin, 2.0 and 32.0; D-ofloxacin, 32.0 and > 64.0; ceftazidime, 8.0 and 64.0; piperacillin with or without tazobactam, 16.0 and > 64.0; trimethoprim-sulfamethoxazole, 0.5 and > 64.0; imipenem, 2.0 and > 64.0. With the exception of those for Stenotrophomonas maltophilia, Burkholderia cepacia, and Alcaligenes faecalis-A. odorans, agar dilution MICs for all strains tested were within 1 dilution of inhibitory (bacteriostatic) levels as determined by time-kill methodology.

The macrolide-lincosamide-streptogramin B resistance phenotypes characterized by using a specifically deleted, antibiotic-sensitive strain of Streptomyces lividans

Genes conferring resistance to macrolide, lincosamide, and streptogramin B (MLS) antibiotics via ribosomal modification are widespread in bacteria, including clinical isolates and MLS-producing actinomycetes. Such erm-type genes encode enzymes that mono- or dimethylate residue A-2058 of 23S rRNA. The different phenotypes resulting from monomethylation (MLS-I phenotype, conferred by erm type I genes) or dimethylation (MLS-II phenotype due to erm type II genes) have been characterized by introducing tlrD or ermE, respectively, into an MLS-sensitive derivative of Streptomyces lividans TK21. This strain (designated OS456) was generated by specific replacement of the endogenous resistance genes lrm and mgt. The MLS-I phenotype is characterized by high-level resistance to lincomycin with only marginal resistance to macrolides such as chalcomycin or tylosin, whereas the MLS-II phenotype involves high-level resistance to all MLS drugs. Mono- and dimethylated ribosomes were introduced into a cell-free protein-synthesizing system prepared from S. lividans and compared with unmodified particles in their response to antibiotics. There was no simple correlation between the relative potencies of MLS drugs at the level of the target site (i.e., the ribosome) and their antibacterial activities expressed as MICs.

In vitro activities of rifabutin, azithromycin, ciprofloxacin, clarithromycin, clofazimine, ethambutol, and amikacin in combinations of two, three, and four drugs against Mycobacterium avium

Multidrug therapy is recommended for treatment of Mycobacterium avium complex (MAC) bacteremia in patients with AIDS. Azithromycin, clarithromycin, rifabutin, ciprofloxacin, ethambutol, clofazimine, and amikacin have all been suggested for use in treating MAC bacteremia, but the most active combinations of these drugs have not been identified, nor has the minimum number of drugs needed for effective therapy been determined. To address the former, the in vitro bactericidal activities of all two-, three-, and four-drug combinations of these seven agents was determined by using 10 blood-derived strains of MAC isolated from patients with AIDS. The activities of the 132 drug combinations were compared by statistical analysis of survival means (analysis of variance) and further evaluated by determining the percentage of strains considered susceptible to each combination. When susceptibility was defined as a decrease in CFU of > or = 2 log10, no two- or three-drug combination and only two four-drug combinations were active against all 10 MAC strains. When a less stringent definition was applied (> or = 1 log10 decrease in CFU), 1 two-drug combinations, 9 three-drug combinations, and 31 four-drug combinations showed activity against all 10 strains. Eighteen selected drug combinations were also tested for intracellular activity in MAC-infected J774 cells. Combinations which contained amikacin as a component were considerably less active against intracellular MAC organisms than against organisms in broth. The opposite result was obtained for the combination of clarithromycin plus clofazimine.

Activity of rifabutin, clarithromycin, ethambutol, sparfloxacin and amikacin, alone and in combination, against Mycobacterium avium complex in human macrophages

Disseminated infection with Microbacterium avium complex (MAC) in patients with AIDS is currently treated with a combination of antimycobacterial agents in order to prevent the selection of resistant mutant strains. Although clinical and microbiological responses can generally be achieved within a few weeks, relapses are common and require modification of the combination regimen or identification of effective alternate therapies. In this study we investigated the activities of rifabutin 0.5 mg/L, sparfloxacin 1 mg/L, clarithromycin 4 mg/L, amikacin 16 mg/L and ethambutol 2 mg/L, alone and in combination, against nine strains of M. avium isolated from the blood of patients with AIDS in order to identify regimens with the greatest therapeutic potential. Macrophages derived from human monocytes were infected with M. avium and inoculated with a single drug or a combination of drugs; cfu counts were performed at 0, 4 and 7 days after infection. At day 4 and at day 7, the combination of rifabutin, clarithromycin, amikacin and sparfloxacin displayed the highest degree of activity. However, the activity did not differ significantly from that of the combination of rifabutin, clarithromycin and ethambutol. The results of this study confirm the activity of combinations including rifabutin and clarithromycin (+/- ethambutol) in human monocyte-derived macrophages and suggest potentially useful associations in incorporating sparfloxacin and amikacin.

Infective endocarditis caused by an unusual gram-negative rod, Rahnella aquatilis

An 11-month-old girl with congenital heart disease developed infective endocarditis. Blood cultures revealed an unusual gram-negative rod, Rahnella aquatilis. The patient was successfully treated with a combination of netilmicin and ceftazidime. This is the first case report of infective endocarditis caused by this organism. R. aquatilis should be recognized as a clinical pathogen capable of causing life-threatening infection in children and adults.

Piperacillin-Tazobactam: a new beta-lactam-beta-lactamase inhibitor combination

We reviewed the spectrum of activity, pharmacokinetics, clinical efficacy, adverse effects, and relative advantages of piperacillin-tazobactam, a new beta-lactam-beta-lactamase inhibitor. Piperacillin-tazobactam has a wide spectrum of activity that includes gram-positive organisms such as staphylococci and streptococci, as well as many gram-negative aerobic and anaerobic bacteria. The combination distributes rapidly after parenteral administration and penetrates well into skin, lung, and intestinal mucosa. Compared with other beta-lactam-beta-lactamase inhibitor combinations, piperacillin-tazobactam has comparable efficacy in the treatment of intraabdominal infections, skin and soft tissue infections, and upper and lower respiratory tract infections. It may have better in vitro activity than the currently available combinations against selective bacteria that produce class I beta-lactamases (Richmond-Sykes classification). The combination is well tolerated, with diarrhea being the most common reported adverse effect. Additional controlled trials and clinical experience are required to define its role in clinical practice.

[Antibacterial activities of combination uses of isepamicin and beta-lactams in vitro against clinically isolated strains. Part 1. Activities against Staphylococcus aureus]

In order to evaluate antibacterial activities of combination uses of isepamicin (ISP) and beta-lactams in vitro, minimum inhibitory concentrations (MICs) these drugs were examined singly and in combination against clinically isolated Staphylococcus aureus. The results are summarized as follows; 1. MICs of ISP + cefazolin (CEZ), ISP + cefotiam (CTM) and ISP + flomoxef (FMOX) were low and the activities against methicillin (DMPPC)-susceptible S. aureus (MSSA) were dependent on the concentration of ISP. Combined effects were observed when the concentrations of ISP were at sub-MIC levels (1/2 approximately 1/4 concentrations). 2. MICs of ISP + CEX, ISP + CTM, ISP + FMOX, ISP + imipenem and ISP + panipenem were low and the activities against DMPPC-resistant S. aureus (MRSA) were dependent on the concentration of ISP, and were similar to those against MSSA. Combined effects were observed when the concentrations of ISP were at sub-MIC levels of ISP. Lower MIC50 or MIC90 was observed at ISP concentrations of 4 approximately 16 micrograms/ml. 3. The blood Cmax of ISP exceeded 20 micrograms/ml at one-time administration of ISP 400 mg, and these results suggested that antibacterial activities of combination uses of ISP and beta-lactams was clinically effective against MRSA infections.

Molecular genetics of resistance to both ceftazidime and beta-lactam-beta-lactamase inhibitor combinations in Klebsiella pneumoniae and in vivo response to beta-lactam therapy

The molecular basis of ceftazidime resistance in 2 isolates of Klebsiella pneumoniae was studied. The first (21300) expressed resistance to ceftazidime and piperacillin-tazobactam. The second (26139) expressed resistance to ceftazidime but remained susceptible to piperacillin-tazobactam. The 2 strains harbored similar large plasmids that hybridized to TEM- and SHV-related beta-lactamase genes. An Escherichia coli strain harboring the plasmid conferring resistance to both compounds (pLRM7) produced beta-lactamases of pI 5.9 (TEM-6) and pI 7.6 (SHV-1). E. coli harboring the other plasmid (pLRM8) expressed only the TEM enzyme because of insertion of IS15 within blaSHV-1. In vivo studies suggested that resistance to beta-lactam-beta-lactamase inhibitor combinations conferred by pLRM7 will be clinically important. Clinical resistance to both extended-spectrum cephalosporins and beta-lactam-beta-lactamase inhibitor combinations is achievable via the production of two enzymes, with only one possessing an extended spectrum of activity.

High-level gentamicin-resistant enterococci: in vitro activity of double and triple combinations of antimicrobial drugs

The ability of double and triple combinations of antimicrobials with different mechanisms of action, such as teicoplanin, meropenem, gentamicin and sparfloxacin, to achieve synergisms was investigated in vitro on some moderate-level gentamicin-resistant (MLGR: 8 < or = MIC < or = 256 mg/l) and high-level gentamicin-resistant (HLGR: MIC > 500 mg/l) enterococci. On MLGR strains, a constant synergistic effect was achieved by a combination of teicoplanin with gentamicin or with meropenem, while generally addition, sometimes close to synergism, was exhibited by gentamicin-meropenem, gentamicin-sparfloxacin and teicoplanin-sparfloxacin associations. Triple combinations of teicoplanin, meropenem and gentamicin, or teicoplanin, sparfloxacin and gentamicin, always showed a remarkable advantage in terms of synergism over double combinations. On HLGR enterococci, the only double association showing an additive effect, sometimes close to synergism, was teicoplanin plus meropenem, while the triple combination of teicoplanin with gentamicin and meropenem always showed a marked synergistic effect. An effect very close to synergism was also shown by the combination of teicoplanin with sparfloxacin and gentamicin.

[Detection of resistance to the amoxicillin-clavulamic acid combination in Salmonella and Shigella]

PURPOSE

To study the emergence of amoxicilline/clavulanate resistance in Salmonella and Shigella.

MATERIAL AND METHODS

We have studied 118 strains of Salmonella enterica and 11 strains of Shigella flexneri isolated in our laboratory along 1993. The MICs values for amoxicilline/clavulanate were determined by the E-Test method and confirmed by the standard agar dilution method.

RESULTS

We have observed that 6% (7 out of 118 strains) of Salmonella enterica and 42% (5 out of 11 strains) of Shigella flexneri isolates exhibited an intermediate susceptibility or were resistant to amoxicilline/clavulanate with MICs values ranging between 16 mg/l and 32 mg/l.

CONCLUSIONS

Along 1993 we have detected the emergence of an amoxicilline/clavulanate resistance in salmonellae and shigellae strains. To our knowledge this fact has not been published up to now (Medline, 1990-October 1994). We don't know the clinical importance of this fact.

In vitro activity of amoxycillin/clavulanate and ticarcillin/clavulanate compared with that of other antibiotics against anaerobic bacteria: comparison with the results of the 1987 survey

The activity of amoxycillin/clavulanate (Augmentin) and ticarcillin/ clavulanate (Timentin) was tested against 351 strict anaerobic clinical isolates collected from September 1993 to April 1994 in eight Belgian university hospitals and compared with that of 8 other antibiotics using the NCCLS reference agar dilution procedure. Production of beta-lactamase was detected by the nitrocefin test in 48% of the isolates. At NCCLS-recommended breakpoints, more than 90% of isolates were susceptible to amoxycillin/clavulanate, ticarcillin/clavulanate, piperacillin/tazobactam, imipenem, chloramphenicol and metronidazole but only 77%, 72% and 48% to cefoxitin, clindamycin and penicillin, respectively. In comparison with the results of a similar survey conducted in 1987 no major changes in susceptibility were observed except for the susceptibility to clindamycin that declined from 83% to 72% overall, and from 83% to 66% in the B. fragilis group. Furthermore one isolate of Clostridium clostridioforme was found produce beta-lactamase and few B. fragilis group isolates showed reduced susceptibility to metronidazole.

Antimycobacterial synergism of clarithromycin and rifabutin

Clarithromycin and rifabutin are among the most promising drugs for the therapy of infections caused by Mycobacterium avium or other atypical mycobacteria. Since synergism of combined drugs is important in order to achieve strong antimycobacterial activity, the combined inhibitory effects of antibacterial agents should also be investigated when agents are evaluated for possible use in antimycobacterial drug therapy. In the present study we examined the antimycobacterial activity of clarithromycin, rifabutin, and their combination against 51 clinical isolates of the M. avium complex from patients with acquired immune deficiency syndrome (AIDS) with disseminated mycobacteriosis. A concentration-dependent inhibition was seen for each drug. The antibacterial effect was significantly more pronounced for the combined drugs than for the agents tested separately. Synergism, against up to 88% of the strains tested, was seen for the tested drugs combined at different concentrations. All 51 M. avium strains were susceptible to the combination of 4 mg/l clarithromycin and 2 mg/l rifabutin.

Role of gut-derived endotoxaemia and bacterial translocation in rats after thermal injury: effects of selective decontamination of the digestive tract

This study was performed to investigate: (1) the role of gut-derived endotoxin/bacterial translocation in the pathogenesis of sepsis, and (2) the possible effects of selective decontamination of the digestive tract (SDD) on mortality in rats following 40 per cent full-thickness scald injury. In the SDD-treated group, Enterobacteriaceae and yeasts were eradicated from the caecal mucosa, while the mucosal flora consisting of mainly anaerobes was well preserved, within 3 days. The incidence of bacterial translocation to the mesenteric lymph nodes (MLN) and viscerae was significantly lowered on postburn days 1, 3 and 5 (P < 0.05-0.01). Meanwhile, pretreatment with SDD resulted in reductions of the faecal endotoxin levels in different segments of intestinal tract to less than 0.5 per cent (0.04-0.45 per cent) of the untreated control; there was also a significant attenuation of the elevation of endotoxin concentrations in both portal and systemic blood. Intestinal diamine oxidase (DAO) activity returned to baseline on day 5 in rats receiving SDD but not in controls. The 5-day survival rate in the SDD-treated group was elevated by 26.7 per cent as compared with controls (P < 0.05). These data suggested that endotoxin/bacterial translocation took place early and commonly, which in turn contributed to postburn sepsis and mortality. SDD was effective in preventing gut origin endotoxaemia and bacterial translocation, and improving the survival rate in rats following severe thermal injuries.

[Antimicrobial activities of clavulanic acid/ticarcillin against clinical isolates]

In order to investigate antimicrobial activities of clavulanic acid/ticarcillin (CVA/TIPC) against Escherichia coli, Enterobacter spp. and Pseudomonas aeruginosa in 1992 and 1994, beta-lactamase activities were analyzed and minimum inhibitory concentrations (MICs) were determined including those of the control drugs. The results are as follows; 1. Compared to a report in 1980, the MIC distributions of CVA/TIPC against E. coli and P. aeruginosa did not show large differences. We found, however, that CVA/TIPC-resistant strains increased among Enterobacter spp. 2. Almost all of CVA/TIPC-resistant strains of Enterobacter spp. were also resistant to cephems and new quinolones, thus they were multiple drug resistant. 3. CVA/TIPC showed strong antimicrobial activities against penicillinase producing E. coli.