Comparative evaluation of orally active antibiotics against community-acquired pathogens: a multi-center study in five Mediterranean countries

Frequency of symptomatic relapses of group A beta-hemolytic streptococcal tonsillopharyngitis in children from 4 pediatric practices following penicillin, amoxicillin, and cephalosporin antibiotic treatment

The objective was to determine the frequency of early symptomatic relapses following antibiotic treatment for group A beta-hemolytic streptococcal (GABHS) tonsillopharyngitis in children from Rochester, New York; Houston, Texas; Spokane, Washington; and Los Angeles, California (2004--2006). The study included 4278 patients. The proportion with a bacteriologic relapse of GABHS tonsillopharyngitis within 1 to 5 days of completing a 10-day treatment course was 8% (penicillin and bicillin), 6% (amoxicillin), 2% (first-generation cephalosporin), and 1% (second-generation and third-generation cephalosporin; P = .0001); symptomatic relapses occurred within 6 to 20 days after completion of therapy in 16%, 14%, 9%, and 7% of cases (P = .0001). Cases from New York and Washington had higher penicillin or amoxicillin failure rates than cases from Texas and California. The frequency of symptomatic relapses of GABHS tonsillopharyngitis, therefore, differs according to the antibiotic treatment selected; the trend for such relapses being penicillin or amoxicillin > cephalosporins although geographic differences may occur.

Pharmacodynamic analysis and clinical trial of amoxicillin sprinkle administered once daily for 7 days compared to penicillin V potassium administered four times daily for 10 days in the treatment of tonsillopharyngitis due to Streptococcus pyogenes in children

An a priori pharmacokinetic/pharmacodynamic (PK/PD) target of 40% daily time above the MIC (T >MIC; based on the MIC(90) of 0.06 microg/ml for Streptococcus pyogenes reported in the literature) was shown to be achievable in a phase 1 study of 23 children with a once-daily (QD) modified-release, multiparticulate formulation of amoxicillin (amoxicillin sprinkle). The daily T >MIC achieved with the QD amoxicillin sprinkle formulation was comparable to that achieved with a four-times-daily (QID) penicillin VK suspension. An investigator-blinded, randomized, parallel-group, multicenter study involving 579 children 6 months to 12 years old with acute streptococcal tonsillopharyngitis was then undertaken. Children were randomly assigned 1:1 to receive either the amoxicillin sprinkle (475 mg for ages 6 months to 4 years, 775 mg for ages 5 to 12 years) QD for 7 days or 10 mg/kg of body weight of penicillin VK QID for 10 days (up to the maximum dose of 250 mg QID). Unexpectedly, the rates of bacteriological eradication at the test of cure were 65.3% (132/202) for the amoxicillin sprinkle and 68.0% (132/194) for penicillin VK (95% confidence interval, -12.0% to 6.6%). Thus, neither antibiotic regimen met the minimum criterion of > or =85% eradication ordinarily required by the U.S. FDA for first-line treatment of tonsillopharyngitis due to S. pyogenes. The results of subgroup analyses across demographic characteristics and current infection characteristics and by age/weight categories were consistent with the primary-efficacy result. The clinical cure rates for amoxicillin sprinkle and penicillin VK were 86.1% (216/251) and 91.9% (204/222), respectively (95% confidence interval, -11.6% to -0.4%). The results of a post hoc PD analysis suggested that a requirement for 60% daily T >MIC(90) more accurately predicted the observed high failure rates for bacteriologic eradication with the amoxicillin sprinkle and penicillin VK suspension studied. Based on the association between longer treatment courses and maximal bacterial eradication rates reported in the literature, an alternative composite PK/PD target taking into consideration the duration of therapy, or total T >MIC, was considered and provides an alternative explanation for the observed failure rate of amoxicillin sprinkle.

Emergence and trends of penicillin non-susceptible Streptococcus pneumoniae in Saudi Arabia and Kuwait - perspective and outstanding issues

For many years in the past Streptococcus pneumoniae was uniformly susceptible to penicillin until the sudden and unexpected emergence of clinical infections caused by penicillin-resistant S. pneumoniae (PRSP) in 1967. Within the following decade, reports of nosocomial and community outbreaks of infections due to PRSP became widespread all over the world. Recent reports suggest that the incidence of resistance rates is rising in many countries although there are geographical variations in the prevalence and patterns of resistance between countries. The problem of antibiotic resistance is further compounded by the emergence of resistance to many beta-lactam antibiotics. The first report of PRSP in Saudi Arabia was in 1991. Barely a year after, PRSP infection was reported in Kuwait in 1992. Since then, studies from various parts of these countries have recorded prevalence rates ranging from 6.2% in Riyadh to 34% in Jeddah and 20% to 56% in neighboring Kuwait. These suggest considerable variation in the prevalence of PRSP in different cities in the Saudi Kingdom and Kuwait. The mechanism of resistance is due to chromosomally mediated alteration of penicillin-binding proteins (PBPs), which are target sites for beta-lactam antibiotics. It would appear that the spread of PRSP strains in Saudi Arabia is driven by the selective pressure created by excessive use and misuse of antimicrobial agents made possible by the easy availability of these agents, often frequently obtainable over the counter. In Kuwait, irrational and misguided use of antibiotics may be the major driving force favoring the spread of PRSP. The serotypes of strains encountered in Saudi Arabia and Kuwait are almost identical, with serotypes 19, 6, 15, 14 and 23 being the most common; together they constitute about 70% of the isolates circulating in these countries. In general, almost 90% of the serotypes included in the 23-polyvalent vaccine are present in the general population. However, a much lower percentage of these serotypes is found in the conjugated vaccines, which are more relevant to our communities. This paper reviews the emergence and the steady increase in the prevalence of penicillin-resistant pneumococcal strains in Saudi Arabia and Kuwait during the last 10 years. It discusses the trends, mechanisms of resistance and factors associated with the emergence, dissemination, and colonization of resistant organisms and suggests options available to clinicians for management of infections due to PRSP.

Alterations in thegyrA andparC Genes inSalmonellaspp. FollowingIn VitroExposure to Fluoroquinolones

We characterize alterations in the QRDR fragment of gyrA and parC in Salmonella spp. following repeated exposure to different quinolones in two in vitro models. Mutations in QRDR of gyrA were found in only 25% of the mutants. The most frequent mutations were Asp87(R)Asn and Asp87(R)Tyr. Strains with the former mutation had a higher ciprofloxacin MIC than those with the latter. We did not find mutations in parC. Our data confirm that mutation in the QRDR fragment of gyrA is the mechanism that produces the greatest decrease in fluoroquinolone susceptibility. There is a greater reduction in the ciprofloxacin susceptibility of strains that were originally nalidixic acid-resistant than in that of strains that were originally susceptible, and this confirms that there is a greater likelihood of therapeutic failures with such strains.