A laboratory assessment of ciprofloxacin and comparable antimicrobial agents

The resistance mechanisms of bacteria against ciprofloxacin and new approaches for enhancing the efficacy of this antibiotic

For around three decades, the fluoroquinolone (FQ) antibiotic ciprofloxacin has been used to treat a range of diseases, including chronic otorrhea, endocarditis, lower respiratory tract, gastrointestinal, skin and soft tissue, and urinary tract infections. Ciprofloxacin's main mode of action is to stop DNA replication by blocking the A subunit of DNA gyrase and having an extra impact on the substances in cell walls. Available in intravenous and oral formulations, ciprofloxacin reaches therapeutic concentrations in the majority of tissues and bodily fluids with a low possibility for side effects. Despite the outstanding qualities of this antibiotic, Salmonella typhi, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa have all shown an increase in ciprofloxacin resistance over time. The rise of infections that are resistant to ciprofloxacin shows that new pharmacological synergisms and derivatives are required. To this end, ciprofloxacin may be more effective against the biofilm community of microorganisms and multi-drug resistant isolates when combined with a variety of antibacterial agents, such as antibiotics from various classes, nanoparticles, natural products, bacteriophages, and photodynamic therapy. This review focuses on the resistance mechanisms of bacteria against ciprofloxacin and new approaches for enhancing its efficacy.

Pharmacokinetic parameters of ciprofloxacin (500 mg/5 mL) oral suspension in critically ill patients with severe bacterial pneumonia: a comparison of two dosages

The authors determined the pharmacokinetic parameters of a new immediate-release ciprofloxacin suspension in tube-fed intensive care patients with bacterial pneumonia, to compare two dosage regimens: 500 mg b.i.d and 750 mg b.i.d. in this prospective clinical trial. The 20 patients were critically ill and on mechanical ventilation and enteral feeding with bacterial pneumonia. They were randomized to receive two different ciprofloxacin dosages: 500 mg b.i.d (group 1) versus 750 mg b.i.d. (group 2). Blood samples were collected from these patients after reaching steady-state and the pharmacokinetic parameters were determined. The mean (range) serum steady-state concentration at 2 h after enteral administration was: C(max 500) = 2.6 (1.2-4.3) mg/L in group 1 and C(max 750) = 3.5 (1.5-5.9) mg/L in group 2. The mean (range) calculated 12-h area under the serum concentration was high in both groups: AUC(0-12 (500)) = 24.7 (12.9-36.2) mg.h/L in group 1 and AUC(0-12 (750)) = 28.9 (18.3-47.5) mg.h/L in group 2. In conclusion, ciprofloxacin oral suspension was well absorbed via nasogastric route in intensive care patients with severe pneumonia, achieving reliable pharmacokinetic parameters for most of the pathogens and important cost reduction compared to intravenous delivery. However, with less susceptible pathogens such as Staphylococcus aureus or Pseudomonas aeruginosa, higher dosages than 750 mg b.i.d. should be given.

Salmonella osteomyelitis and arthritis in sickle cell disease

Salmonellosis is one of the most frequent serious infections in sickle cell patients and remains a significant cause of morbidity and mortality in this population. Capillary occlusion secondary to intravascular sickling may devitalize and infarct the gut, permitting Salmonella invasion. Reduced function of the liver and spleen, together with interference with reticuloendothelial system function due to erythrophagocytosis, suppresses clearing of these organisms from the blood stream. Abnormal opsonizing and complement function probably also play a role. The expanded bone marrow with sluggish flow leads to an ischemic focus for salmonella localization. The majority of Salmonella infections in sickle cell patients involve bones (especially long bones) and joints and occur most frequently in early childhood. Multiple sites, often symmetrical, are usually involved. It is imperative to distinguish Salmonella osteomyelitis from bone infarctions. While clinical and hematologic data may be suggestive, radionuclide bone imaging studies, particularly combined technetium and gallium scintigraphy and technetium sulphur colloid bone marrow scans, and magnetic resonance imaging appear more sensitive and specific. Salmonella osteomyelitis is best managed medically. Chloramphenicol, ampicillin, and trimethoprim/sulfamethoxazole have been used most frequently; however, newer beta lactams and quinolones are more active. Septic arthritis carries a poorer prognosis and often requires aggressive surgical intervention.

Pefloxacin and vancomycin vs. gentamicin, colistin sulphate and vancomycin for prevention of infections in granulocytopenic patients: a randomised double-blind study

To test the value of pefloxacin for the prevention of infections in patients with chemotherapy-induced neutropenia, oral pefloxacin plus vancomycin (PV) (n = 76) or gentamicin, colistin sulphate and vancomycin (GCV) (n = 74) were administered in a randomised double-blind study. Infections were significantly less severe in the PV than in the GCV group. Patients receiving PV had significantly fewer episodes of bacteraemia and central venous line infections than patients treated with GCV. Gram-positive and gram-negative infections were significantly less frequent in patients receiving PV, because of fewer infections with Staphylococcus species and enterobacteriaceae. Stool culture detected significantly more gram-positive organisms in the PV group and more gram-negative organisms in the GCV group. Thus, PV was more efficacious than GCV for the prevention of gram-positive and gram-negative infections in the neutropenic patients, despite lower efficacy in eradicating gram-positive organisms from the lower intestinal tract.

In vitro activity of eight antimicrobial agents against non-penicillinase-producing gonococci isolated in Munich

The susceptibility of 119 strains of Neisseria gonorrhoeae isolated in Munich in 1986 to eight antibiotics was assessed. Although some degree of resistance to penicillin and tetracycline, as well as high minimum inhibitory concentrations (MIC) of spectinomycin, were observed, all the strains were sensitive to ciprofloxacin, enoxacin, fleroxacin, cefotaxime, and FCE 22250.

Ciprofloxacin: chemistry, mechanism of action, resistance, antimicrobial spectrum, pharmacokinetics, clinical trials, and adverse reactions

Ciprofloxacin, considered a benchmark when comparing new fluoroquinolones, shares with these agents a common mechanism of action: inhibition of DNA gyrase. While ciprofloxacin demonstrated a fairly good activity against gram-positive bacteria, it is against gram-negative organisms that it proved to be more potent than other fluoroquinolones. It is the most active quinolone against Pseudomonas aeruginosa, with MIC90s on the order of 0.5 micrograms/ml. When given orally, ciprofloxacin exhibited 70% bioavailability and attained peak serum levels ranging between 1.5 and 2.9 micrograms/ml after a single 500-mg dose. Nineteen percent of an oral dose was excreted as metabolites in both urine and feces. In most cases, body fluids and tissue concentrations equaled or exceeded those in concurrent serum samples. In clinical trials, oral and intravenous ciprofloxacin yielded similar clinical and bacteriologic results compared to standard therapy in a wide array of systemic infections, including lower and upper urinary tract infections; gonococcal urethritis; skin, skin structure, and bone infections; and respiratory tract and gastrointestinal tract infections. Major benefits with the oral form of this quinolone are expected in chronic pyelonephritis and bone infections, and in pulmonary exacerbations in patients with cystic fibrosis. Emergence of ciprofloxacin-resistant microorganisms has been noted in clinical practice, primarily Pseudomonas aeruginosa and Staphylococcus aureus. The most frequent side effects are related to the gastrointestinal tract; but attention should be given to adverse central nervous system effects.

Norfloxacin: clinical pharmacology and clinical use

Norfloxacin, a nalidixic acid analog, is the first of the fluorinated quinolinecarboxylic acids to be marketed in the United States. It demonstrates potent antibacterial activity against aerobic, gram-negative bacteria including the Enterobacteriaceae, gentamicin-resistant Pseudomonas aeruginosa, and penicillin-resistant Neisseria gonorrhoeae. Norfloxacin exhibits good activity against methicillin-resistant and -sensitive Staphylococcus aureus, but less activity against most other aerobic, gram-positive organisms. Anaerobic bacteria are resistant to the drug. Resistance to norfloxacin is not plasmid mediated, but is secondary to bacterial mutation, and occurs less frequently than nalidixic acid resistance. Its pharmacokinetic properties after a 400-mg oral dose consist of a peak serum concentration of 1.3-1.58 micrograms/ml, an elimination half-life of 3-7 hours, and good penetration into kidney and prostatic tissues. Renal excretion is the major route of elimination. Norfloxacin is highly effective in the treatment of uncomplicated and complicated urinary tract infections, and gonococcal urethritis. Adverse effects are generally well tolerated and usually do not require discontinuation of therapy.

Ciprofloxacin in the treatment of urinary tract infections

Twenty patients (15 males; five females) aged 11-70 years, with urinary tract infections were treated with one 250 mg tablet of ciprofloxacin every 12 h for 5-10 days. Clinical response to this treatment was the complete disappearance of symptoms in 85% of cases and the elimination of the micro-organism responsible for infection. In only three patients, who all had urinary calculus in addition to an infection, clinical failure of the therapy occurred and the causative micro-organism persisted. Tolerance to the therapy was excellent in this study, no adverse reactions connected with the treatment being reported.

Ciprofloxacin

Ciprofloxacin is a new fluorinated quinolone antibiotic with high activity against a wide spectrum of gram-positive and gram-negative bacteria, including methicillin-resistant Staphylococcus aureus, Enterobacteriaceae, and Pseudomonas aeruginosa. Clinical trials using the oral preparation of ciprofloxacin have demonstrated its effectiveness in a wide variety of infections. In addition, extensive clinical trials with the intravenous preparation are underway. In vitro and in vivo studies with ciprofloxacin have reported the incidence of resistant organisms to be very low. In addition, the incidence of ciprofloxacin-related side effects throughout its clinical trials has been minimal. Most reports of side effects have been related to the gastrointestinal tract, such as nausea or vomiting. The incidence of adverse experiences in worldwide clinical trials has been reported to be approximately 6.4 percent.

In vivo and in vitro activity of ciprofloxacin plus azlocillin against 12 streptococcal isolates in a neutropenic site model

Closed-space neutropenic infection sites were simulated in rabbits by subcutaneous semipermeable chambers that were inoculated with 5 X 10(4) CFU/ml of various strains of Streptococcus pneumoniae, Streptococcus faecalis, and Streptococcus avium. Four hours after inoculation, treatment was begun with ciprofloxacin, 10 or 30 mg/kg, azlocillin, 100 mg/kg, amikacin, 15 mg/kg, procaine penicillin G, 300 U/dose, or gentamicin, 2 mg/kg, alone and in two-drug combinations. Antimicrobials were given intramuscularly every 6 hr for 16 doses. Extravascular chambers were sampled throughout the treatment course for bacterial counts and antimicrobial concentration. In vivo results were compared to in vitro tests of inhibition, killing, and synergism. Ciprofloxacin alone had little effect on the animal infection sites. Azlocillin alone reduced, in vivo, eight of 12 isolates greater than or equal to 5 log10 CFU/ml by 92 hr as compared to control. Azlocillin plus ciprofloxacin reduced all 12 isolates greater than or equal to 5 log10 CFU/ml by 92 hr, whereas amikacin plus azlocillin reduced only three and penicillin plus gentamicin only one of the six group D streptococcal isolates greater than or equal to 5 log10 CFU/ml.

Comparative in vitro activities of pefloxacin, ofloxacin, enoxacin and ciprofloxacin against 256 clinical isolates

The antibacterial activity of four new fluoroquinolone carboxylic acids, pefloxacin, ofloxacin, enoxacin and ciprofloxacin, against 256 clinical isolates was investigated by means of an agar dilution method. Generally, all quinolones tested had a high activity against Gram-negative bacteria. More than 90% of Enterobacteriaceae strains were inhibited by a quinolone concentration of 0.4 microgram/ml. Also strains usually resistant to conventional beta-lactam antibiotics, and sometimes to third-generation cephalosporins, like Enterobacter spp., Serratia spp, and Yersinia spp. were susceptible to the tested quinolones. Ciprofloxacin was 5 to 25-fold more potent on a weight basis against Enterobacteriaceae than the other quinolones. Neisseria meningitidis, Neisseria gonorrhoeae, and Haemophilus influenzae were extremely susceptible to the new quinolones. Ciprofloxacin was about 10 times more potent against Pseudomonas aeruginosa than the other quinolones, and was the only quinolone that was sufficiently active against all tested P. aeruginosa strains (MIC less than or equal to 0.4 microgram/ml). The activity against Gram-positive bacteria was considerably lower. All the quinolones investigated had an acceptable activity against many of the methicillin-sensitive and methicillin-resistant Staphylococcus aureus and coagulase-negative staphylococci. The majority of the Streptococcus spp. tested was quinolone-resistant, and was Listeria monocytogenes. Generally, it was evident that ciprofloxacin was more potent on a weight basis than the other quinolones, but this difference was counterbalanced by a higher achievable serum concentration for ofloxacin. Some of the investigated fluoroquinolones might constitute valid therapeutical alternatives to beta-lactam antibodies and aminoglycosides in the treatment of serious bacterial infections.

Effect of norfloxacin on human oropharyngeal and colonic microflora and multiple-dose pharmacokinetics

10 healthy volunteers received 200 mg norfloxacin orally every 12 h for 7 days. Saliva, throat and faecal specimens were collected days 0, 3, 5, 7, 14 and 21 to study the effect of norfloxacin on the normal microflora. The concentrations of norfloxacin in serum, urine, saliva and faeces were determined by a microbiological method and all samples except faeces were also assayed by high-pressure liquid chromatography (HPLC). The pharmacokinetics of norfloxacin were studied on day 3. The mean peak serum concentration (+/- SD) attained after 0.75-1.0 h was 0.75 +/- 0.15 mg/l measured by HPLC, and the mean terminal serum half-life was 4.2 +/- 0.6 h. The mean cumulative urinary elimination was 29% during 12 h after dosing. There was no significant difference between values obtained by microbiological assay and by HPLC. The saliva concentration was approximately 30% of the serum levels 1.0-1.5 h after administration. No accumulation in faeces was found during the administration period, and mean concentrations were 940 mg/kg. The changes in the oropharyngeal flora were minor and only branhamella were affected. In the colonic flora, the number of enterobacteria was strongly depressed while the anaerobic microflora was only slightly affected. Two weeks after the administration period, both the oropharyngeal and colonic microflora had returned to normal.

Liquid chromatographic determination of ciprofloxacin and some metabolites in human body fluids

Two column liquid chromatographic (HPLC) methods for the determination of ciprofloxacin and three metabolites are described. Both use reversed phase chromatography, the stationary phase being Nucleosil 5C18. Method A separates ciprofloxacin, metabolite M1 and another metabolite of unknown structure using fluorometric detection. Method B allows the determinations of metabolite M3 (oxo-ciprofloxacin) in urine by UV absorption. Serum was deproteinised with acetonitrile. Urine was diluted with buffer solution. The detection limit of ciprofloxacin was 0.010 mg/l serum and 0.2 mg/l urine and for the metabolite M3, 1 mg/l urine. Within-batch precision (coefficient of variation) for ciprofloxacin in serum was 0.8 to 2.4% and between-batch precision 4.8 to 9.3%. In urine within-batch precision was 1.7 to 2.1% and between-batch precision 2.4 to 7.2%. Recovery rates of ciprofloxacin from three groups of spiked sera was 94.5 +/- 2.6%, 97.2 +/- 1.1% and 95.0 +/- 1.8% and from urine 99.6%. Results obtained by HPLC (method A) were compared with those from a standard microbiological assay by means of bivariate regression analysis. In 12 subsets of data the slope of the regression line varied from 1.042 to 1.556. Significantly higher results from the microbiological assay were probably due to the presence of microbiologically active metabolites. We conclude that HPLC is the more specific method of determination. The described methods were applied for pharmacokinetic studies and therapeutic drug monitoring.

Pharmacokinetics of ciprofloxacin in healthy volunteers after oral and intravenous administration

The pharmacokinetics of ciprofloxacin was studied in three groups of healthy volunteers comprising a total of 16 males and 16 females (age 21-35 years; body weight 52-80 kg). Single oral doses of 50, 100, 250, 500 and 750 mg were given to fasting subjects. The 250 mg dose was repeated after a breakfast. Intravenous doses of 50, 100 and 200 mg were given by short infusion in a randomized cross-over sequence. Concentrations of the drug in serum and urine were determined by high-performance liquid chromatography and by a microbiological assay. Mean peak concentrations between 0.37 +/- 0.49 mg/l (100 mg dose) and 1.97 +/- 0.50 (750 mg dose) were measured 60-75 min after oral administration. Twelve hours after 750 mg ciprofloxacin, serum concentrations were 0.15 +/- 0.05 mg/l. Taking a breakfast reduced absorption by 15-20% compared to the fasting state, as judged by peak concentrations, AUC and renal excretion. After 200 mg i.v. (20 min infusion period), initial serum concentrations of 4.0 +/- 1.2 mg/l were observed which declined 12 h later to 0.070 +/- 0.025 mg/l. Mean cumulated recovery of ciprofloxacin from urine over 24 h varied between 25.5% and 33.6% of oral doses and between 53.2% and 57.4% of intravenous doses. Two of the three metabolites seen in the chromatograms were identified as M1 and M3 (oxo-ciprofloxacin). Cumulated renal excretion after an oral 250 mg dose was 1.2 +/- 0.4% of M1 and 5.5 +/- 1.6% of M3.(ABSTRACT TRUNCATED AT 250 WORDS)

Norfloxacin: a quinoline antibiotic

Norfloxacin is a quinoline (quinolinecarboxylic acid) that should prove successful in treating infections that currently require hospitalization and intravenous antibiotics. Although a nalidixic acid derivative, it possesses greater antibacterial activity against gram-positive and gram-negative bacteria. Compared with other antimicrobial agents, norfloxacin is more potent than the aminoglycosides, first-, second-, and third-generation cephalosporins, tetracycline, trimethoprim-sulfamethoxazole, carbenicillin, piperacillin, nalidixic acid, oxolinic acid, cinoxacin, and enoxacin. In the clinical studies to date, the side effects of norfloxacin have been minimal, but include nausea, vomiting, anorexia, dizziness, headache, drowsiness, depression, and a bitter taste in the mouth. In studies with more than 4000 patients, the incidence of side effects ranged from 3.9 to 4.7 percent, with most appearing by the second day of therapy.

Pharmacokinetics of ciprofloxacin after intravenous and increasing oral doses

The pharmacokinetics of ciprofloxacin were evaluated after increasing single oral doses of 100, 250, 500 and 1000 mg, and an intravenous dose of 100 mg given to each of 12 healthy volunteers (6 females and 6 males). Concentrations in serum and urine were determined by microbiological assay. The rise in peak serum concentrations and the values of the total area under the serum concentration curve were proportional to the increase in the oral doses. As the oral dose increased a slight increase was observed in the apparent time lag before absorption from 0.34 h after 100 mg to 0.53 h after 1000 mg. The serum half-life after the intravenous dose was 3.2 h. After the oral doses shorter apparent half-life values were observed. The intravenous dose showed an elimination phase distribution volume of 2.76 l/kg and total body clearance of 40.7 l/h. The total urinary excretion was 42.2 +/- 15.6% of the dose after the intravenous dose; the figure was lower after the oral doses. The bioavailability of the 100 mg oral dose was 83.7% as calculated from the value of the total area under the serum curve after the same oral and intravenous dose in all 12 subjects. Ciprofloxacin thus demonstrates normal linear pharmacokinetics, the rise in serum concentrations being proportional to the dose.

Ciprofloxacin concentrations in bone and muscle after oral dosing

Ciprofloxacin, a quinoline derivative with marked gram-negative and staphylococcal activity, may be a valuable orally administered agent for use against soft-tissue and bone infections. The concentrations of this antibiotic in serum, bone, and muscle samples were determined in patients undergoing orthopedic surgery. A total of 18 patients undergoing hip or knee replacement surgery or osteotomy were randomized to receive single oral doses of ciprofloxacin (500 mg, 750 mg, or 1 g); 10 patients with osteomyelitis were given single doses of 500 or 750 mg. Mean levels in bone of more than 1 microgram/g were achieved with the 750-mg ciprofloxacin doses in patients with osteomyelitis (1.4 +/- 1 microgram/g) or with the 1-g doses in patients without infections (1.6 +/- 0.6 microgram/g). The levels in muscle were significantly higher with each increasing dose level. Orally administered ciprofloxacin (750 mg given every 12 h) should provide adequate concentrations in bones and soft tissues to treat most osteomyelitis and soft-tissue infections.

Fluorinated quinolones. A review of their mode of action, antimicrobial activity, pharmacokinetics and clinical efficacy

Quinolones, chemically related to nalidixic acid, have a strong and rapid bactericidal action against Gram-negative bacteria, including Ps. aeruginosa, some Mycobacteria, Legionella and Staphylococci. Streptococci and anaerobic bacteria are usually less sensitive. The quinolones exert their bactericidal action through inhibition of the enzyme DNA gyrase. Quinolones are absorbed for 50-100% from the gastro-intestinal tract, their volume of distribution is generally high (2 l/kg) and high concentrations are reached in almost all organs. The elimination half-lives range from 4 to 14 h. The efficacy of quinolones in urinary tract infections has been shown in many studies. They also seem to be effective in many serious infections. In animal studies their efficacy was generally equal or superior to aminoglycosides. Until now only mild and infrequent side effects have been reported.

Pharmacokinetics of ciprofloxacin and effect of repeated dosage on salivary and fecal microflora

The pharmacokinetics of ciprofloxacin was studied in 12 volunteers during a 5-day course of 500 mg of ciprofloxacin given orally twice a day. The effects on the microflora of saliva and feces were also examined. Serum and urine samples were assayed for ciprofloxacin microbiologically, and the salivary and fecal microflora were examined quantitatively after processing onto a series of selective media. Fecal samples were also investigated for the presence of Clostridium difficile and its cytotoxin. The MICs for new colonizing bacteria were examined in the salivary and fecal samples. There was no accumulation during the course of 5 days with peak serum concentrations identical (2.8 and 2.3 mg/liter) after the first and final doses, and the areas under the serum curves were similar (9.6 mg/liter). The serum half-life was 2.5 h on both days. The changes in the salivary flora were minor and affected only the neisseriae. In the fecal flora, the numbers of enterobacteria and enterococci decreased markedly, whereas the changes in anaerobic flora (anaerobic cocci, fusobacteria, and bacteroids) were not so pronounced. However, 14 days after the drug was discontinued, the salivary and fecal flora were normalized in all respects. No new colonization of ciprofloxacin-resistant bacteria for which MICs were above 1.0 mg/liter was observed. C. difficile or its cytotoxin was not detected.

Ciprofloxacin pharmacokinetics in patients with cystic fibrosis

The pharmacokinetics of ciprofloxacin were studied in cystic fibrosis patients and healthy volunteers following oral administration of 500 mg and 1000 mg. Serum kinetics as well as urinary recovery were monitored. As the body weights of cystic fibrosis patients and the healthy volunteers differed significantly, kinetic parameters were calculated on the basis of a constant relative dose in mg/kg body weight. Neither serum kinetics nor urinary recovery differed significantly between the two groups, as indicated by the serum concentration versus time curves ranging from 1.1 to 1.4 mg X h/l, the elimination half-life of 4.4 to 5.1 h and the 24 h urinary recovery which amounted to 35% to 41% of the dose administered. Serum concentrations were linearly proportional to the doses administered. Sputum concentrations were monitored in cystic fibrosis patients. Again, ciprofloxacin sputum levels were linearly proportional to the doses and were within the same range as serum concentrations. Thus, ciprofloxacin kinetics are not altered in cystic fibrosis patients as compared to healthy volunteers.

In vitro activity of the newer quinolones compared with the classic ones and tobramycin

The halogenated substitution of quinolone derivatives has given rise to a new group of substances called newer quinolones, which possess extraordinary antibacterial activity in vitro. The aim of our study was to compare the effect of the newer quinolones ciprofloxacin (CIP), norfloxacin (NOR) and enoxacin (ENO) with that of the classical ones nalidixic acid (NA), oxolinic acid (OX) and pipemidic acid (PIP) and with a widely-used aminoglycoside tobramycin (TBR). This was tested on 2,263 strains from clinical isolations. Evaluating the effect of the least active substances as a unit, we generally found the MIC90s to be of the following order: (Formula: see text). The remaining groups among the antibiotics studied are ordered identically, the most potent being the newer quinolones in the following order: CIP is at least four times superior to NOR, which in turn is at least twice as effective as ENO for gram-positive organisms, but only 1.2 times for gram-negative bacilli.