Potential use of procalcitonin as a diagnostic criterion in febrile neutropenia: experience from a multicentre study.

In order to assess the diagnostic value of procalcitonin, 158 patients with febrile neutropenia from centres across Europe were studied. Patients with fever were diagnosed on the basis of either: (1) clinical, radiological and microbiological criteria; or (2) the procalcitonin value. In the latter case, concentrations of 0.5-1.0 ng/mL were considered diagnostic of localised infection, concentrations of 1.0-5.0 ng/mL of bacteraemia, and concentrations of > 5.0 ng/mL of severe sepsis. Procalcitonin and C-reactive protein were estimated daily in serum by immunochemiluminescence and nephelometry, respectively. Overall, the sensitivity (specificity) of procalcitonin for bacteraemia was 44.2% (64.3%) at concentrations of 1.0-5.0 ng/mL, and 83.3% (100%) for severe sepsis at concentrations of > 5.0 ng/mL. It was concluded that procalcitonin is a marker strongly suggestive of severe sepsis at concentrations of > 5.0 ng/mL. Estimated concentrations of < 0.5 ng/mL indicate that infection is unlikely, but it was observed that bacteraemia associated with coagulase-negative staphylococci may fail to elevate serum procalcitonin levels.

Primary meningococcal arthritis: case report and review.

A rare case of primary meningococcal arthritis of a 16-year-old female patient is described. Arthritis involved her left knee and Neisseria meningitidis was isolated from blood and from the synovial fluid. Successful treatment was achieved by the intravenous administration of penicillin G.

Assessment of procalcitonin as a diagnostic marker of underlying infection in patients with febrile neutropenia.

The novel inflammatory marker procalcitonin (PCT) was assessed as an index of infection in patients with febrile neutropenia. Blood samples were obtained from 115 patients with febrile neutropenia for determination of PCT levels before onset of fever and daily until the resolution of fever. The median PCT level on the first day of fever was 8.23 ng/mL in patients with bacteremia, compared with 0.86 ng/mL in patients with localized bacterial infections (P=.017). The median PCT level on the first day of fever was 2.62 ng/mL in patients with severe sepsis, compared with 0.57 ng/mL in patients with clinically localized infections (P<.001). A dramatic decrease in PCT levels was documented after resolution of the infection; PCT levels were elevated when the infection worsened. Pronounced PCT levels were also found in patients with fever of unknown origin who were responding to antimicrobial chemotherapy, compared with those not responding to treatment with antibiotics. PCT levels were particularly elevated in patients with bacteremia and severe sepsis. These findings provide new insight into the application of PCT in clinical trials as a diagnostic tool of the severity of an infection in patients with febrile neutropenia and of the need to change antimicrobial regimen.

Impact of n-6 polyunsaturated fatty acids on growth of multidrug-resistant Pseudomonas aeruginosa: interactions with amikacin and ceftazidime.

Twenty-six multidrug-resistant Pseudomonas aeruginosa isolates were exposed over time to 300 microg of gamma-linolenic acid or arachidonic acid per ml or to the combination of both acids at 150 microg/ml each with ceftazidime and amikacin with or without albumin to observe the in vitro interactions of the antibiotics. Antibiotics and albumin were applied at their levels found in serum. Synergy between acids and antibiotics was found against 13 isolates, and it was expressed after 5 h of growth in the presence of albumin. The results indicate that further application in experimental infection models is merited.

In-vitro activity of FK 037 (Cefoselis), a novel 4(th) generation cephalosporin, compared to cefepime and cefpirome on nosocomial staphylococci and gram-negative isolates.

The novel 4(th) generation cephalosporin FK037 was in vitro compared to cefepime and cefpirome on 563 multiresistant nosocomial isolates including methicillin-susceptible (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA). Their time-kill effect was studied on MSSA, Escherichia coli, Klebsiella pneumoniae, and isolates of Enterobacter cross-resistant to cefotaxime, ceftriaxone, and to ceftazidime, their interaction with amikacin being also evaluated on the latter isolates. Results revealed that FK037 possessed a superior antistaphylococcal activity on MSSA isolates to both other compounds being however equal active to cefepime and cefpirome on multiresistant enterobacteriaceae. Synergy was documented between 4(th) generation cephalosporins and amikacin on K. pneumoniae and on Enterobacter spp. cross-resistant to 3(rd) generation cephalosporins. In the latter species 4(th) generation cephalosporins remained inactive. The presented results support the need of clinical studies with FK037 as monotherapy for nosocomial infections based on the local surveillance data of the level of antimicrobial resistance of each hospital.

Sitafloxacin (DU-6859a) and trovafloxacin: postantibiotic effect and in vitro interactions with rifampin on methicillin-resistant Staphylococcus aureus.

Sitafloxacin (DU-6859a) and trovafloxacin are novel quinolones potent on methicillin-resistant Staphylococcus aureus (MRSA) that are designed for once daily administration. In order to define the adequacy of the above regimen for the therapy of infections by multiple drug-resistant MRSA, their postantibiotic effect (PAE), their bactericidal activity, and their interactions with rifampin were determined on 14 MRSA isolates resistant to both ciprofloxacin and rifampin. PAE was defined after 1-h exposure to 1x, 4x, and 10x MIC and the killing effect after exposure to 1x and 4x MIC. Rifampin was applied for interactive studies at a concentration of 2 micrograms/mL, which is equal to its mean serum level. Median PAEs produced by 1x, 4x, and 10x MIC of sitafloxacin were 1.39, 3.75, and 6.61 h respectively, and by 1x, 4x, and 10x MIC of trovafloxacin 0.87, 2.07, and 2.23 h respectively. PAEs achieved by sitafloxacin were statistically shown to be longer than those achieved by trovafloxacin; PAEs achieved by a concentration of 10x MIC of each quinolone did not differ significantly from those achieved by a concentration of 4x MIC. Both the 4x and 10x MIC concentrations produced a more prolonged PAE than the 1x MIC concentration. A rapid bactericidal activity was expressed over the first 6 h of growth by each quinolone involving 80% of isolates enhanced in some isolates by their interaction with rifampin. The above findings revealed an extended PAE and a rapid killing effect of both sitafloxacin and trovafloxacin on MRSA resistant to ciprofloxacin and to rifampin, thus supporting their once daily administration in the therapy of infections by multiple drug-resistant MRSA. However little in vitro benefit is derived by their interaction with rifampin.

In vitro activity of quinupristin/dalfopristin and newer quinolones combined with gentamicin against resistant isolates of Enterococcus faecalis and Enterococcus faecium.

In a study designed to obtain data on compounds active against enterococci, the minimum inhibitory concentrations (MICs) of quinupristin/dalfopristin (RP 59500) and the novel quinolones DU-6859a, trovafloxacin, levofloxacin, and sparfloxacin were determined for 122 Enterococcus faecalis and seven Enterococcus faecium isolates. In addition, 15 Enterococcus faecalis isolates resistant to gentamicin, DU-6859a, and trovafloxacin were exposed over time to combinations of DU-6859a plus gentamicin and trovafloxacin plus gentamicin. DU-6859a and trovafloxacin were found to be the most active compounds against Enterococcus faecalis and DU-6859a and RP 59500 against Enterococcus faecium. Synergy between either DU-6859a or trovafloxacin and gentamicin was observed with 27 to 35% of the isolates. It is concluded that DU-6859a and trovafloxacin are very potent against enterococci, especially when combined with gentamicin.

In vitro activity of polyunsaturated fatty acids on Pseudomonas aeruginosa: relationship to lipid peroxidation.

Based on previous findings that gamma-linolenic acid (GLA) inhibits Escherichia coli growth and provokes the induction of strains resistant to aminoglycosides, 19 Pseudomonas aeruginosa strains were exposed in vitro over time to GLA, to arachidonic acid (AA) and to their combination in the presence or absence of vitamin E. All acids were used at a 300 microg/ml concentration, whereas vitamin E was added as an antioxidant. Lipid peroxidation was evaluated by the thiobarbiturate assay measuring malonodialdehyde (MDA) production. It was found that GLA or AA killed 5-10% of strains at 24 h of growth, whereas when applied in combination their effect involved 100% of strains at 24 h and was limited to 68% of strains in the presence of vitamin E (P< 0.01). MDA production was time-dependent and it was restrained by vitamin E (P < 0.01). Post acid exposure, 27% to 37% of the survived strains became resistant to diverse antimicrobial agents and mainly to ticarcillin, to ceftazidime and to amikacin; no strain developed resistance in the presence of vitamin E. It is concluded that GLA and AA interact bactericidally on P. aeruginosa isolates, inducing the development of strains resistant to beta-lactams and to aminoglycosides; their action might be mediated through their peroxides. Further research is necessary to establish the clinical application of these in vitro findings.

In-vitro activity and killing effect of quinupristin/dalfopristin (RP59500) on nosocomial Staphylococcus aureus and interactions with rifampicin and ciprofloxacin against methicillin-resistant isolates.

Quinupristin/dalfopristin (RP59500) is a novel streptogramin and a semisynthetic derivative of pristinamycins IA and IIB. The following properties of RP59500 were investigated: (i) its in-vitro activity against 164 hospital isolates of Staphylococcus aureus, 101 of which were methicillin-resistant (MRSA); (ii) its killing effect against 24 MRSA and seven methicillin-susceptible (MSSA) isolates; (iii) its interactions with rifampicin and ciprofloxacin against 18 MRSA isolates, six susceptible to both rifampicin and ciprofloxacin and 12 resistant to both, at 1 x MIC, 2 x MIC and 4 x MIC. Rifampicin and ciprofloxacin were applied at a concentration equal to their mean serum levels in order to establish the clinical relevance of the results. The MIC50, MIC90, MBC50 and MBC90 of quinupristin/dalfopristin were, respectively, < or = 0.015, 2, 0.12 and 2 mg/L for MRSA isolates and < or = 0.015, 0.06, < or = 0.015 and 0.25 mg/L for MSSA isolates. All isolates were inhibited by quinupristin/dalfopristin. Its killing effect varied with concentration and time, being optimal at 4 x MIC and after 24 h growth. Strains surviving 24 h exposure to this agent had much higher MICs than the parent strain, but only a limited number of them became resistant. Quinupristin/dalfopristin at 2 x MIC and 4 x MIC showed in-vitro synergy with rifampicin against highly resistant isolates mainly at 6 h and 24 h of growth involving 50-83% of MRSA isolates, and showed synergy with ciprofloxacin at 24 h involving 42-75% of isolates. The MIC increase in colonies surviving at 24 h was restricted by the presence of rifampicin or ciprofloxacin. In contrast, the above combinations acted synergically over the total number of MRSA strains susceptible to both rifampicin and ciprofloxacin. The above findings show that quinupristin/dalfopristin is a very potent antistaphylococcal agent, and that its activity against MRSA isolates is enhanced when it is combined with rifampicin or ciprofloxacin.

Interactions of Ceftazidime and Amikacin on Multiresistant Pseudomonas aeruginosa: Have They Altered in the Six-Year Period from 1988 to 1994?

OBJECTIVE: The wide clinical application of the combination of ceftazidime and amikacin over recent years for infections caused by multiresistant isolates may render the combination useless in the future because of the development of resistance. The present study aimed to investigate whether the in vitro susceptibility of multiresistant Pseudomonas aeruginosa isolated in 1994 to this drug combination had changed compared with 1988 isolates. DESIGN: Twenty-three P. aeruginosa strains isolated in 1988 and 30 in 1994, all resistant to ceftazidime, imipenem, ciprofloxacin and amikacin, were exposed in vitro to 16 mg/L of ceftazidime and 16 mg/L of amikacin, i.e. a concentration within their serum levels. RESULTS: The enhanced killing effect of the tested combination remained stable through 1988 to 1994 involving at least half of the isolates, a finding that was independent of the minimum inhibitory concentration of both agents. However, the tested combination produced a statistically superior decrease in baseline viable cell counts of strains isolated in 1988 compared with those isolated in 1994. CONCLUSION: These results confirm the adequacy of the tested combination on multiresistant Pseudomonas aeruginosa despite its wide clinical application over the last 6 years, and the need for a strict antibiotic policy to prevent resistance development.

Comparative in vitro interactions of ceftazidime, meropenem, and imipenem with amikacin on multiresistant Pseudomonas aeruginosa.

To evaluate the possibility of an enhanced killing effect by ceftazidime, meropenem, or imipenem with amikacin 26 multiresistant Pseudomonas aeruginosa isolates, to nine anti-pseudomonal antimicrobials of diverse chemical classes were studied. A modified time-kill curve procedure was used with a 16 micrograms/ml concentration of each antimicrobial, i.e. within the range of their serum level; a total of 248 killing-curves were performed. Any > or = 2 log10 decrease of viable cell counts by a combination compared to the most active single agent was considered an adequate enhanced killing effect. The latter was found to be mainly expressed at 24 h of growth and involved 30-50% of the tested isolates. The above findings were independent of the MIC level to any individual beta-lactam or to amikacin. It is concluded that there is no difference between the activity of the ceftazidime and amikacin combination and those of meropenem or imipenem with amikacin on multiresistant P. aeruginosa.

In-vitro interactions of DX-8739, a new carbapenem, meropenem and imipenem with amikacin against multiresistant Pseudomonas aeruginosa.

In order to investigate the antimicrobial interactions against multiresistant Pseudomonas aeruginosa, thirty-seven strains resistant to antimicrobial agents of five different chemical classes were exposed in vitro to the combination of three carbapenems. DX-8739, a novel DHP-I stable analogue, meropenem and imipenem with amikacin. The tested combinations expressed an enhanced killing activity against 38-46% of strains and an additive effect against 5-13%. These effects were the same whether the applied carbapenem was DX-8739, meropenem or imipenem; they were also independent of the MIC of any antimicrobial.

In vitro influence of polyunsaturated fatty acids on nosocomial Pseudomonas aeruginosa: a preliminary report.

Recent evidence derived from a mouse infection model implies an 'anti-infective' role of polyunsaturated fatty acids (PUFAs) which could not be attributed to an alteration of eicosanoid or cytokine biosynthesis provoked by them. In order to investigate that role, seven Pseudomonas aeruginosa nosocomial pathogens were in vitro exposed to 200 and 300 mug/ml of two PUFAs, arachidonic acid (AA) and gamma-linolenic acid (GLA), by performing 43 time-kill curves. Both PUFAs were found to inhibit P. aeruginosa growth as compared to their controls, an effect maximized at 5 h of incubation and minimized at 24 h. The strains that survived after the 24 h AA and GLA exposure were removed from the culture medium with added AA or GLA; half of these strains acquired enormously higher MIC and MBC values to aminoglycosides compared to their relevant controls. The possible mechanism of action of AA and GLA on P. aeruginosa and the clinical relevance of the presented findings is a matter of further research.

In-vitro inhibitory activity of gamma-linolenic acid on Escherichia coli strains and its influence on their susceptibilities to various antimicrobial agents.

Recent experimental evidence implies that polyunsaturated fatty acids (PUFAs) possess anti-infective activity which is unrelated to any alteration of eicosanoid biosynthesis or cytokine production provoked by PUFAs and it seems necessary to establish their possible influence on Gram-negative bacteria. Forty-two Escherichia coli strains were cultured in vitro in the presence of gamma-linolenic acid (GLA) at concentrations of 50 mg/L and 300 mg/L and a total of 77 killing curves were performed with GLA concentrations of 100, 200 and 300 mg/L GLA. At 50 and 300 mg/L, GLA inhibited 9.5% and 33.3% of strains respectively; GLA killing curves demonstrated a > or = 1 log GLA inhibitory effect in 0%, 18.2% and 72.7% of strains after the 5 h sequential exposures at 100, 200 and 300 mg/L GLA but this was not observed after the 24 h GLA exposure. Following removal of the E. coli strains from the culture medium with GLA, > or = four-fold increases in MICs and/or MBCs of various antimicrobials, were observed in 42.9% and 60% of strains after exposure to 50 and 300 mg/L GLA respectively; most of these increases involved aminoglycosides. The reproducibility of GLA inhibitory effects and increase in MICs and/or MBCs for E. coli in the two different experimental procedures used, was 82% and 73% respectively. Further studies are necessary to clarify the mechanism of GLA action on E. coli and assess the clinical relevance of these findings.

Comparative in vitro killing activity of meropenem versus imipenem against multiresistant nosocomial Pseudomonas aeruginosa.

In order to compare the in vitro killing activity of meropenem and imipenem against multiresistant P.aeruginosa 14 strains were used. All nosocomial isolates were susceptible to meropenem and imipenem minimum inhibitory concentration (MIC < or = 4 micrograms/ml) and resistant to at least two other antimicrobial agents of diverse chemical class with antipseudomonal activity. Forty-two killing curves were performed by exposing a 5 x 10(5) CFU/ml log-phase inoculum to 1x minimum bactericidal concentration (MBC) of each carbapenem. Meropenem was found to possess a slower killing rate than imipenem over the first 5 hours of P.aeruginosa exposure, but to be equally effective as imipenem after 24 hours of incubation. Forty percent and 11.1% of P.aeruginosa strains developed resistance to imipenem and meropenem respectively after a 24-hour exposure to carbapenem. The authors speculate about the underlying mechanisms explaining the higher rate of resistance development to imipenem than to meropenem.

In vitro activity and killing effect of DX-8739, a new carbapenem, compared with those of meropenem and imipenem against multiresistant Pseudomonas aeruginosa.

DX-8739 is a new dehydropeptidase I-stable carbapenem. In order to evaluate its activity in comparison with those of meropenem and imipenem, 147 multiresistant Pseudomonas aeruginosa isolates acquired nosocomially were simultaneously exposed to the actions of the three carbapenems in vitro, whereas to compare their killing effects on 14 strains, 56 killing curve studies were performed. Overall DX-8739 was found to possess inhibitory activity as well as bactericidal activity statistically superior to those of meropenem and imipenem. At a concentration of 4 micrograms/ml, 106 strains (72.1%) were found to be imipenem resistant; 33 and 27.4% of these strains were inhibited by DX-8739 and meropenem, respectively, a statistically significant difference (P < 0.05). DX-8739 was also shown to possess intrinsic activity in vitro superior to those of meropenem and imipenem against the imipenem-susceptible population of strains. However, no statistically significant difference regarding the comparative killing activities of the three studied carbapenems was observed. Following exposure to carbapenem for 24 h, 33.3, 44.4, and 70% of the strains which survived became resistant to DX-8739, meropenem, and imipenem, respectively. The reported results demonstrate the significant activity of DX-8739 against multiresistant P. aeruginosa strains acquired nosocomially. The mechanism of action of DX-8739 on P. aeruginosa is unknown, and various hypotheses that might explain its in vitro superiority over meropenem and imipenem are proposed.

Do Escherichia coli susceptibilities to various antibiotics decrease in the presence of polyunsaturated fatty acids? A preliminary report.

Polyunsaturated fatty acids (PUFAs) constitute an ingredient of the daily diet and therefore they might be in close contact with the polymicrobial gastrointestinal flora. In order to study the interaction of bacteria and PUFAs, eight Escherichia coli strains were cultured in the presence of docosahexaenoic acid (DHA) at a concentration of 100 micrograms/ml, and six of the latter eight at 75 micrograms/ml whereas nine other E. coli strains were cultured in the presence of 50 micrograms/ml gamma-linolenic acid (GLA). DHA provoked > or = 4-fold increases in the minimum inhibitory and bactericidal concentrations of various antibiotics in six strains at 100 micrograms/ml and in three strains at 75 micrograms/ml, which were not antibiotic-specific and involved mainly aminoglycosides. GLA provoked in four strains > or = 4-fold increases in MICs-MBCs of ampicillin. The clinical relevance of these observations require further study.