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PubMed1998

Immunopharmacology of oral betalactams.

Among the oral beta-lactam antibiotics only cefaclor has demonstrated a consistent in vitro and in vivo immunopharmacological effect which favors phagocytic chemotaxis and antimicrobial potential by inducing a T-helper 1 or pro-inflammatory response. Together with cefpimizole, cefaclor significantly reduces the minimum bactericidal concentration (MBC) against some bacterial species when cultured together with a suspension of polymorphonuclear leukocytes, as opposed to some other oral beta-lactams, co-amoxiclav and cefixime, which do not show this effect. The pro-inflammatory component of cefaclor's activity explains the clinical success of this antibiotic in a high percentage of cases, even when laboratory tests indicate in vitro resistance by the pathogen.

Adjuvants, Immunologic↗
PubMed2002

Effect of a short course of clarithromycin therapy on sputum production in patients with chronic airway hypersecretion.

STUDY OBJECTIVE: Long-term administration of macrolide antibiotics reduces sputum production in patients with chronic airway diseases, probably by inhibiting airway inflammation. The objective of the present study was to determine the acute effects of a macrolide on airway chloride secretion and sputum production. METHODS: We first investigated the effect of erythromycin treatment on chloride diffusion potential difference (CPD) across tracheal mucosa in vivo. Next, we conducted a double-blind, parallel-group study examining the effect of 7 days of treatment with clarithromycin (400 mg/d), amoxicillin (1,500 mg/d), or cefaclor (750 mg/d) in patients with chronic bronchitis or bronchiectasis without apparent respiratory infection. RESULTS: IV administration of erythromycin decreased the CPD of rabbit tracheal mucosa in a dose-dependent manner. Treatment of patients with clarithromycin decreased sputum production, whereas amoxicillin and cefaclor treatment had no effect. The percentage of patients whose sputum decreased > 30% from baseline (responders) was 38% in the clarithromycin group, 7% in the amoxicillin group, and 0% in the cefaclor group. During treatment with clarithromycin, the sputum solid composition increased and chloride concentration decreased in responders, but these changes were not observed in nonresponders. CONCLUSION: Short-term administration of 14-membered macrolide reduces chronic airway hypersecretion, presumably by inhibiting chloride secretion and the resultant water secretion across the airway mucosa.

Adult↗
PubMed1984

Mechanism of action of the new orally active cephalosporin FK027.

The mechanism of action of a new orally active cephalosporin, FK027, was compared to that of cephalexin and cefaclor to elucidate its excellent antibacterial activity against Gram-negative bacteria. FK027 showed very high affinity for the penicillin-binding proteins (PBPs) 3, 1a and 1bs of Escherichia coli whereas cephalexin showed fairly high affinity for PBPs 1a, 4 and 3. The ability of FK027 to penetrate the outer membranes of E. coli and Enterobacter cloacae was less than that of cephalexin and cefaclor. However, FK027 was extremely stable to both plasmid-mediated penicillinases and chromosomal beta-lactamases except the Bacteroides fragilis enzyme and its stability was superior to that of cephalexin and cefaclor. These results indicate that the potent antibacterial activity of FK027 is based on its enhanced affinity for the target enzymes and its high stability to beta-lactamases.

Amoxicillin↗
PubMed2005

Not all pustules are infective in nature: acute generalised exanthematous pustulosis causing pustular eruptions in an elderly woman.

Acute generalised exanthematous pustulosis (AGEP) is an adverse drug reaction that can occur in any age group. It is commonly mistaken as pustular psoriasis or cutaneous infection, resulting in unnecessary commencement of medications such as methotrexate and antibiotics that can cause harm to the patient or interact and adversely affect the efficacy of other medications. Early diagnosis of AGEP avoids unnecessary investigations and treatment, which not only can harm the patient but also escalate health care, as the condition is self-limiting. This case report illustrates AGEP secondary to Cefaclor occurring in a 72-year-old Chinese woman. Although the literature has documented the occurrence of AGEP with Cefaclor, the unique feature of this case is the occurrence of AGEP following repeated uneventful courses of Cefaclor. This case highlights that AGEP must never be forgotten in the work-up for pustular eruptions in an elderly patient.

Acute Disease↗
PubMed2005

Efficacy of prophylaxis in women with sex induced cystitis.

UNLABELLED: Sexual intercourse has been established as one of the most important risk factors for both isolated and recurrent uncomplicated infections of the urinary tract. Prophylactic therapy requires only a small dose of an antimicrobial agent, which is generally given at bedtime for 6 to 12 months. An alternative method is to give an antimicrobial agent for six months post-intercourse. It is still unknown which of the two methods is most effective. A total of 123 women with suspected sexually induced recurrent cystitis (mean age 28 years, range 15 to 65) and a history of recurrent urinary tract infection (UTI) (the last one within the last six months) were subjected to prophylactic therapy for six months. Half of them were treated with low-dose trimethoprim-cotrimoxazole (TMP-SMX) and cefaclor given orally post-intercourse (spontaneous usage), while the other half were treated with low-dose TMP-SMX and cefaclor given at bedtime. The response to the prophylactic therapy was classified as continued cure in 106 cases (86.17%), failure in 13 cases (10.56%), and unknown in four cases (3.25%). TMP-SMX administered in continuous nightly prophylaxis showed similar efficacy and tolerability as cefaclor post-intercourse. OBJECTIVE: To determine the efficacy of prophylaxis in women with recurrent sex induced cystitis and compare the post-intercourse versus the conventional bedtime given long-term, low-dose use of prophylactic antimicrobials.

Adolescent↗
PubMed1983

[Report of experiences with the oral cephalosporin-derivative cephaclor in respiratory tract infections].

The oral cephalosporin derivative Cefaclor was administered to 22 patients with respiratory tract infections at a daily dosage of 3 x 500 mg. The average duration of the Cefaclor therapy was 10 days. In all patients improvement of the clinical picture and of objective criteria, such as fever, cough and sputum was observed. It was not possible to objectivate side effects by laboratory parameters. Gastrointestinal disturbances and allergic symptoms were only present in individual cases but did not significantly influence the clinical efficacy of Cefaclor.

Administration, Oral↗
PubMed1995

Serum sickness like illness and antimicrobials in children.

AIM: To determine which antimicrobials are associated with the development of serum sickness like reactions in children admitted to hospital in Christchurch. METHOD: A retrospective case note review of children admitted with serum sickness like reactions over a 10 year period was carried out. 59 children were identified and 30 of these were eligible for inclusion in the study. RESULTS: Of the 30 children with serum sickness like reaction, 19 had received cefaclor alone, six penicillin V, two amoxycillin, and one each flucloxacillin cotrimoxazole and triacetylolendomycin (TAO). Children received these antimicrobials for 3-10 days. CONCLUSION: In this study cefaclor was commonest antimicrobial agent associated with the development of serum sickness like reaction. This association should receive consideration prior to prescribing cefaclor to children.

Amoxicillin↗
PubMed1987

[Smoking and lower respiratory tract infection].

Cigarette smoking exerts deleterious effects not only on the respiratory tract, but also on the lung's parenchyma. The FEV is reduced in heavy chronic smokers. Persistent smoking has an unfavourable influence on mucociliary activity. According to the results of recent research almost 8 million people in the U.S. were suffering from chronic bronchitis in 1981. There is a direct correlation between the number of cigarettes smoked, over what period of time, and the incidence of chronic bronchitis. In studies with patients suffering from exacerbations of chronic bronchitis the most common bacterial pathogens found were Haemophilus influenzae, Streptococcus pneumoniae and Branhamella catarrhalis. Mycoplasma pneumoniae and certain viruses are counted amongst the non-bacterial pathogens. Antibiotics should be effective against such possible pathogens. The resistance of H. influenzae to ampicillin/amoxicillin is currently observed in at least 12% of cases, whilst H. influenzae is regularly observed to be resistant to erythromycin. Cefaclor, trimethoprim/sulphamethoxazole and amoxicillin/clavulanic acid offer satisfactory forms of treatment. Pneumonia caused by S. pneumoniae, H. influenzae, B. catarrhalis and Legionella pneumophila is often seen in smokers and patients with COLD. Haemocultures should be prepared for all hospitalized patients. Penicillin G and/or V is the agent of choice. Cefaclor or trimethoprim/sulphamethoxazole can be given to counter beta-lactamase producing H. influenzae whilst cefaclor, erythromycin, tetracycline or trimethoprim/sulphamethoxazole are used for the treatment of B. catarrhalis infections. In Legionella infections erythromycin is the preferred treatment. A combination of erythromycin and cefamandole or ceftriaxone is indicated for empirical management. Patients with COLD should be immunised with pneumococcus and influenza vaccines.

Bacterial Infections↗
PubMed1992

Comparative in vitro activity and beta-lactamase stability of RU29246, the active metabolite of HR916B.

HR 916B is a new orally absorbed cephalosporin. In tests its active metabolite, RU29246, inhibited Streptococcus pyogenes, Streptococcus agalactiae and Streptococcus pneumoniae at less than or equal to 0.12 micrograms/ml, which is similar to the antibacterial activity of cefuroxime, and was more active than cefaclor. It was also more active (MIC 2 micrograms/ml) than cefixime, cefuroxime, cefaclor and cefotaxime against staphylococci. RU29246 inhibited Escherichia coli, Klebsiella pneumoniae, Citrobacter diversus, Klebsiella oxytoca, Proteus mirabilis, Providencia stuartii and Salmonella spp. at less than or equal to 1 microgram/ml, thus being more active than cefuroxime and cefaclor, but was less active than cefixime and cefotaxime. It did not inhibit Pseudomonas aeruginosa and other Pseudomonas spp., Enterobacter spp., Serratia marcescens or Bacteroides fragilis. RU29246 was not hydrolyzed by TEM-1, Staphylococcus aureus TEM-2 or Moraxella catarrhalis beta-lactamases, but was hydrolyzed by TEM-3 and the chromosomal beta-lactamases of Proteus vulgaris and Morganella morganii. Plasmid and chromosomal beta-lactamases were inhibited by RU29246.

Cephalosporins↗
PubMed1994

Comparative microbiological activity and pharmacokinetics of cefprozil.

In vitro studies on the activity of cefprozil have been conducted in Europe and North America. Against gram-negative bacilli, cefprozil and cefaclor are at least two to four times more active than cephalexin. Cefixime is more active against these organisms. Against gram-positive cocci, cefprozil is at least two to four times more active than cefaclor and cephalexin; cefixime has limited gram-positive activity, and is particularly inactive against staphylococci (MIC90 32 mg/l). Cefprozil is highly active against Streptococcus pneumoniae (unlike cefixime). Those strains of this genus that display intermediate resistance to pneumococci are more susceptible to cefprozil than cefaclor. Neisseria species and Moraxella catarrhalis are susceptible to cefprozil (MIC90 0.06 and 1 mg/l). beta-lactamase-producing strains of Haemophilus influenzae appear to be susceptible to cefprozil, as the reported MIC90 is 2-4 mg/l. Enterococci, Pseudomonas aeruginosa, and those strains of the Enterobacteriaceae that commonly possess a chromosomal cephalosporinase (e.g., Providencia, Morganella and Enterobacter) are generally considered to be resistant to cefprozil as well as to other oral cephalosporins. Cefprozil appears to display enhanced stability to the commonly encountered Tem-1 and SHV-1 plasmid-mediated beta-lactamases, as found in Haemophilus influenzae, Neisseria gonorrhoeae and the Enterobacteriaceae. Cefprozil is rapidly absorbed, reaching a maximum concentration 0.9 to 1.2 h post-dose. Following oral doses of 250 and 500 mg, the Cmax is 6.2 and 10.0 mg/l respectively. Serum half-lives are generally reported as between 1.2 and 1.4 h, and urine recovery is high, 57-70%.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Bacterial Agents↗
PubMed1996

Cephalosporin and carbacephem nephrotoxicity. Roles of tubular cell uptake and acylating potential.

Three beta-lactams, desacetylcephaloglycin, ampicillin, and loracarbef, were studied to test a hypothesis derived from retrospective analysis of previously studied cephalosporins: that beta-lactam nephrotoxicity develops in approximate proportion to tubular cell antibiotic concentrations and lactam ring reactivities. Concentrations of each beta-lactam (and insulin) in rabbit renal cortex and serum were measured at the end of 0.5-hr infusions of 100 mg antibiotic/kg body weight and 0.5 to 0.67 hr later. Total cortical AUCs (total areas under the curve of concentration and time in renal cortex) and transported cortical AUCs (total minus insulin-space beta lactam) were calculated from these measurements. Reactivities, determined by the rate constants of lactam-ring opening at pH 10, were taken from the literature. Nephrotoxicity was quantified by grades of proximal tubular cell necrosis and by serum creatinine concentrations 2 days after infusion of 100-1500 mg/kg of the antibiotics. Desacetylcephaloglycin was slightly less nephrotoxic than cephaloglycin; the AUCs reactivities, and toxicities of these two cephalosporins fit the proposed model, particularly when allowance is made for hepatic and renal deacetylation of cephaloglycin. The very low AUCs, limited reactivity, and absence of nephrotoxicity of ampicillin also fit the model. Loracarbef had a transported AUC less than three times, and reactivity one-thirtieth, those of cefaclor, respectively. Although only at 1500 mg/kg, loracarbef was significantly more nephrotic than cefaclor. If the relativity of loracarbef with its targeted bacterial proteins, which is essentially the same as that of cefaclor, is considered instead of the base hydrolysis rate constant, than loracarbef also fits the model. By the same analysis, the comparatively high in vitro stability of other carbacephems, although pharmaceutically convenient, may not limit their nephrotoxicity.

Acylation↗
PubMedDate not supplied

In vitro activity of cefprozil (BMY 28100) and cefepime (BMY 28142) against Streptococcus pneumoniae, Branhamella catarrhalis, and Haemophilus influenzae, and provisional interpretive criteria for disk diffusion and dilution susceptibility tests with Haemophilus influenzae.

The in vitro activities of two new cephalosporins, an oral agent, cefprozil and a parenteral compound, cefepime, were assessed against recent clinical isolates of Streptococcus pneumoniae, Moraxella (Branhamella) catarrhalis, and Haemophilus influenzae. In general, both cefprozil and cefepime MICs were higher for beta-lactamase-producing strains of M. catarrhalis in comparison to strains that lacked beta-lactamase. By contrast, beta-lactamase-positive and -negative strains of H. influenzae had similar cefprozil and cefepime minimum inhibitory concentrations (MICs). The MIC90 values for cefprozil were 0.12, 32, 4.0, and 0.5 micrograms/ml versus S. pneumoniae, H. influenzae, and beta-lactamase-positive and negative strains of M. catarrhalis, respectively. In comparison to three other oral cephalosporins included in this study, cefaclor, cefuroxime axetil, and cefixime, cefprozil was the most active agent against S. pneumoniae, the least active against B. catarrhalis, and equivalent in activity to cefaclor against H. influenzae. The cefepime MIC values against S. pneumoniae, H. influenzae, and beta-lactamase-positive and negative strains of M. catarrhalis were 0.03, 0.25, 2.0, and 0.5 micrograms/ml, respectively. Cefepime was less active than ceftriaxone for all three organism groups, however, was in all cases more active than cefixime, cefuroxime, cefaclor, and cefprozil.(ABSTRACT TRUNCATED AT 250 WORDS)

Cefepime↗
PubMed2004

Susceptibility of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis to 17 oral antimicrobial agents based on pharmacodynamic parameters: 1998-2001 U S Surveillance Study.

Pharmacokinetic/pharmacodynamic parameters were used to interpret susceptibility data for the oral agents tested in a clinically meaningful way. Among S pneumoniae isolates, >99% were susceptible to respiratory fluoroquinolones, 91.6% to amoxicillin, 92.1% to amoxicillin/clavulanic acid (95.2% at the extended-release formulation breakpoint), 90.6% to clindamycin, 80.4% to doxycycline, 71.0% to azithromycin, 72.3% to clarithromycin, 71.8% to cefprozil and cefdinir, 72.6% to cefuroxime axetil, 66.3% to cexime, 63.7% to trimethoprim/sulfamethoxazole, and 19.7% to cefaclor. Among H influenzae isolates, 28.6% were b-lactamase positive, but virtually all were susceptible to amoxicillin/clavulanic acid (98.3%, with 99.8% at the extended-release formulation breakpoint), cexime (100%), and uoroquinolones (99.8%), whereas 93.5% were susceptible to cefdinir, 82.8% to cefuroxime axetil, 78.1% to trimethoprim/sulfamethoxazole, 70.2% to amoxicillin, 25.1% to doxycycline, 23.2% to cefprozil, and 5% to cefaclor, azithromycin and clarithromycin. Most isolates of M catarrhalis were resistant to amoxicillin, cefaclor, cefprozil, and trimethoprim/sulfamethoxazole. Thus significant b-lactam and macrolide/azalide resistance in Streptococcus pneumoniae and b-lactamase production and trimethoprim/sulfamethoxazole resistance in untypeable Haemophilus influenzae are still present. The results of this study should therefore be applied to clinical practice based on the clinical presentation of the patient, the probability of the patient's having a bacterial rather than a viral infection, the natural history of the disease, the potential of pathogens to be susceptible to various oral antimicrobial agents, the potential for cross-resistance between agents with S pneumoniae, and the potential for pathogens to develop further resistance. Antibiotics should be used judiciously to maintain remaining activity and chosen carefully based on activity determined by pharmacokinetic/pharmacodynamic-based breakpoints to avoid these bacteria developing further resistance, particularly to fluoroquinolones.

Administration, Oral↗
PubMed2003

Rapid and sensitive high-performance liquid chromatographic determination of four cephalosporin antibiotics in pharmaceuticals and body fluids.

A rapid, accurate and sensitive method has been developed and validated for the quantitative simultaneous determination of four cephalosporins, cephalexin and cefadroxil (first-generation), cefaclor (second-generation) and cefataxim (third-generation), in pharmaceuticals as well as in human blood serum and urine. A Spherisorb ODS-2 250 x 4-mm, 5-microm analytical column was used with an eluting system consisting of a mixture of acetate buffer (pH 4.0)-CH(3)OH 78-22% (v/v) at a flow-rate 1.2 ml/min. Detection was performed with a variable wavelength UV-Vis detector at 265 nm resulting in limit of detection of 0.2 ng for cefadroxil and cephalexin, but only 0.1 ng for cefotaxime and cefaclor per 20-microl injection. Hydrochlorothiazide (HCT) (6-chloro-3,4-dihydro-7 sulfanyl-2H-1,2,4-benzothiadiazine-1-1-dioxide) was used as internal standard at a concentration of 2 ng/microl. A rectilinear relationship was observed up to 8, 5, 12 and 35 ng/microl for cefadroxil, cefotaxime, cefaclor, cephalexin, respectively. Analysis time was less than 7 min. The statistical evaluation of the method was examined by means of within-day repeatability (n=8) and day-to-day precision (n=9) and was found to be satisfactory with high accuracy and precision. The method was applied to the determination of the cephalosporins in commercial pharmaceuticals and in biological fluids: human blood serum after solid-phase extraction and urine simply after filtration and dilution. Recovery of analytes in spiked samples was in the range from 76.3 to 112.0%, over the range of 1-8 ng/microl.

Cephalosporins↗
PubMed1998

Surveillance of pneumococcal resistance in Belgium during winter 1996-1997.

This study tested 212 pneumococcal isolates from 9 institutions for their susceptibilities to penicillin, ampicillin, amoxycillin, amoxycillin/clavulanate, cefaclor, cefuroxime, cefotaxime, imipenem, tetracycline, erythromycin, and clarithromycin using NCCLS-standardized microdilution. Penicillin-insusceptibility was 12.3% [5.7% intermediate (0.12-1 microgram/ml) and 6.6% high-level (> or = 2 micrograms/ml)], tetracycline-insusceptibility (> or = 4 micrograms/ml) 31.1%, and erythromycin-insusceptibility (> or = 0.5 microgram/ml) 31.1% as well. Erythromycin-insusceptible isolates showed cross-insusceptibility to clarithromycin. Penicillin-susceptible isolates were susceptible to all beta-lactams. MICs of all beta-lactams rose with those of penicillin for penicillin-insusceptible isolates. Ampicillin and penicillin were equally potent against penicillin-insusceptible isolates, imipenem, cefotaxime, and amoxycillin +/- clavulanate were more potent (generally 5, 1, and 1 doubling dilution, respectively), and cefuroxime and cefaclor less potent (generally 1 and 6 doubling dilutions, respectively). Most penicillin-insusceptible isolates were high-level resistant to cefaclor (> or = 32 micrograms/ml). Although MICs of all beta-lactams rose with those of penicillin, resistance to penicillin was not absolute in terms of cross-resistance. Most penicillin-intermediate and high-level penicillin-resistant isolates remained fully susceptible and intermediate, respectively, to amoxycillin +/- clavulanate, cefotaxime, and imipenem, but not to cefuroxime. Penicillin-susceptible isolates were 76.9%, 42.3%, and 34.6% co-insusceptible to tetracycline, erythromycin, and tetracycline plus erythromycin, respectively. Most penicillin-, tetracycline-, and erythromycin-insusceptible isolates were of capsular types 23 >> 6 > 19 > 32, 19 > 6 > 28 > 23, and 19 > 6 > 14 > 23, respectively. Compared to winter 1994-1995, insusceptibility to penicillin, tetracycline, and erythromycin rose by some 4%, 4%, and 13%, respectively.

Adolescent↗
PubMedDate not supplied

In vitro study on the antimicrobial activity of various antibiotics against clinical isolates of Streptococcus pneumoniae from Belgium collected during winter 1998-1999.

A total of 205 isolates of Streptococcus pneumoniae obtained from 10 different centres were included in this study. The susceptibilities to penicillin, ampicillin, amoxicillin, amoxicillin/clavulanic acid, cefaclor, cefuroxime, cefotaxime, imipenem, ciprofloxacin, gemifloxacin, grepafloxacin, levofloxacin, trovafloxacin, erythromycin, clarithromycin, miocamycin, clindamycin and tetracycline were determined by a microdilution technique following NCCLS recommendations. Decreased susceptibility to penicillin was 16.1% [6.8% intermediate (0.12-1 microgram/mL) and 9.3% high-level (> or = 2 micrograms/mL)], cefotaxime insusceptibility (> or = 1 microgram/mL) 12.7%, ciprofloxacine insusceptibility (> or = 2 micrograms/mL) 15.6% with 1.5% of high level resistance (> or = 4 micrograms/mL), erythromycin insusceptibility (> or = 0.5 microgram/mL) 36.1% and tetracycline insusceptibility (> or = 4 micrograms/mL) 22.9%. Decreased susceptibility to cefotaxime was found in 78.8% of the penicillin-insusceptible isolates. No decreased susceptibility was found for gemifloxacin (> or = 0.5 microgram/mL) and trovafloxacin (> or = 1 microgram/mL). Compared to the 1996-1997 surveillance, penicillin, cefotaxime and erythromycin insusceptibility rose by 3.8%, 5.2% and 5.0% respectively, while tetracycline insusceptibility decreased with 8.2%. MICs of all beta-lactams rose with those of penicillin for penicillin-insusceptible isolates. Amoxicillin +/- clavulanate, cefotaxime and imipenem were generally 1, 1 and 5 doubling dilutions respectively more potent than penicillin on these isolates. Penicillin, ampicillin and cefuroxime were equally active while cefaclor was generally 5 dilutions less potent. Most penicillin-insusceptible isolates remained fully susceptible to amoxicillin +/- clavulanate and imipenem. The penicillin-insusceptible isolates were 36.4%, 27.3% and 3.0% co-insusceptible to erythromycin, erythromycin plus tetracycline and tetracycline respectively. A subpopulation of 52 isolates obtained from children aged < or = 3 years was also studied. Compared to the other isolates we found a statistically significant increase in insusceptibility for penicillin, cefaclor, cefuroxime, erythromycin, clarithromycin and tetracycline while a significant decrease was found for ciprofloxacin.

Adolescent↗
PubMed1996

In vitro susceptibilities of 176 clinical isolates of Streptococcus pneumoniae to 11 beta-lactams, erythromycin, and tetracycline.

One hundred seventy six consecutive, non-duplicate pneumococcal isolates from clinical specimens collected from November 1994 through February 1995 in nine general hospitals throughout Belgium were tested for their in vitro susceptibilities to penicillin, ampicillin, amoxycillin with and without clavulanate, cefaclor, cefuroxime, cefonicid, cefprozil, cefpodoxime, cefotaxime, imipenem, tetracycline, and erythromycin by means of the NCCLS microdilution test. The overall rate of decreased susceptibility to penicillin was 12.5%, including 6.3% of intermediately and 6.3% of fully resistant isolates. Penicillin, ampicillin amoxycillin, amoxycillin/clavulanate, cefuroxime, cefotaxime and imipenem had the highest activity on a weight basis (MIC50 < or = 0.008 microgram/ml), followed by cefpodoxime and erythromycin (MIC50 of 0.015 microgram/ml), cefprozil and tetracycline (MIC50 of 0.12 microgram/ml), and eventually, cefaclor and cefonicid (MIC50 of 0.5 microgram/ml). Aggregate rates of susceptible plus intermediately resistant isolates at NCCLS-recommended breakpoints, i.e. overall percentages of isolates likely to respond to increased antibiotic doses in vivo (except for meningitis), were 100.0% for imipenem and cefotaxime, 98.9% for amoxycillin with and without clavulanate, 93.8% for penicillin, and 90.9% for cefuroxime. Overall rates of susceptibility to erythromycin and tetracycline amounted to 78.4% and 72.7%, respectively. MIC values of all beta-lactams increased with those of penicillin. Ampicillin was equally active as penicillin against isolates with reduced susceptibility to the latter (MIC90 of 2 micrograms/ml); imipenem, cefotaxime, and amoxycillin with and without clavulanate however, were more active (MIC90 3, 1, and 1 doubling dilution, respectively, below that of penicillin), while cefpodoxime, cefuroxime, cefprozil, cefonicid, and cefaclor on the other hand, were less active (MIC90, 1, 1, 2, 5, and 5 doubling dilutions, respectively, above that of penicillin). In conclusion, the present data confirm that pneumococcal resistance to penicillin has increased in Belgium, suggest that resistance to erythromycin may have stabilised, and reveal an unexpectedly high rate of resistance to tetracycline. Imipenem was the most active antibiotic tested overall, and amoxycillin with or without clavulanate the most active oral antibiotic, with activity almost similar to that of cefotaxime.

Anti-Bacterial Agents↗
PubMed1987

Evaluation of Hemophilus type B systemic isolates for beta-lactamase and non-beta-lactamase mediated ampicillin resistance and for susceptibility to other antimicrobial agents.

Of 175 recent Minnesota Hemophilus influenzae type b isolates from systemic disease, 43 were found to be resistant to ampicillin (greater than or equal to 4 micrograms/mL [mg/L]), each of which produced beta-lactamase. Of the 132 ampicillin-susceptible isolates, 68 (52%), all beta-lactamase negative, had minimum inhibitory concentrations (MICs) of either 1 or 2 micrograms/mL (mg/L), indicating relative resistance if derived from cerebrospinal fluid (CSF) infections. From a review of the literature, and in agreement with the authors findings, ampicillin-resistant beta-lactamase-negative isolates are rare and are likely to be nontypeable, of respiratory origin, and with MICs in the low resistance range. For the 43 ampicillin-resistant isolates, percentages resistant to other agents were as follows: 0% chloramphenicol, 0% rifampin, 6% tetracycline, 0% trimeprim-sulfamethoxazole, 2% cefamandole, 5% cefaclor, 2% moxalactam, and 0% for the remaining third-generation cephalosporins cefotaxime, ceftazidime, and ceftizoxime. Unlike ampicillin-resistant isolates, 100% of ampicillin-susceptible isolates had relatively low cefaclor MICs of less than or equal to 4 micrograms/mL (mg/L), suggesting a relatively increased H. influenzae beta-lactamase effect on cefaclor in comparison with the other cephalosporins tested.

Ampicillin↗