Clinical Isolates of Streptococcus pneumoniae with Different Susceptibilities to Ceftriaxone and Cefotaxime

Abstract

Ceftriaxone and cefotaxime are extended-spectrum cephalosporins previously demonstrated to possess very similar in vitro activities against Streptococcus pneumoniae. Anecdotal reports of isolates with divergent in vitro susceptibilities to ceftriaxone and cefotaxime have been published. To determine the prevalence of pneumococcal isolates with divergent ceftriaxone and cefotaxime susceptibilities, we tested 1,000 clinical isolates collected by U.S. laboratories in 2001-2002 by broth microdilution and E-test. The percentages of isolates susceptible to ceftriaxone and cefotaxime were significantly different by both broth microdilution (98.6 and 96.6%, respectively; P < 0.05) and E-test (98.3 and 95.8%; P < 0.001). The differences observed were due solely to the activities of the two agents against penicillin-resistant isolates. Twenty-six of 188 penicillin-resistant isolates (13.8%) demonstrated different ceftriaxone and cefotaxime MIC interpretative phenotypes when tested by broth microdilution; 18 isolates were concurrently ceftriaxone susceptible and cefotaxime intermediate, 6 were ceftriaxone intermediate and cefotaxime resistant, and 2 were ceftriaxone susceptible and cefotaxime resistant (1.1% of penicillin-resistant isolates; 0.2% of all isolates tested). Sixteen of the 26 isolates (65%) were from southern U.S. states. The 26 isolates had serogroups and serotypes (6, 9, 14, 19, and 23) commonly associated with penicillin-resistant isolates; SmaI pulsed-field gel electrophoresis identified 18 isolates (69%) dispersed among five subtype groups and 8 isolates that were unrelated to any of the other isolates. We conclude that certain isolates of penicillin-resistant pneumococci are less susceptible to cefotaxime than to ceftriaxone and that these isolates are not the result of the spread of a single clone. Whether such isolates have increased in prevalence over time remains unknown.

Streptococcus pneumoniae: Does Antimicrobial Resistance Matter?

“…4 Six PBPs have been identified in S. pneumoniae (PBPs 1a, 1b, 2a, 2b, 2x, 3). 93,94 Alterations in PBPs 2x, 2b, and 1a reduce binding to the target site and are responsible for virtually all b-lactam resistance among S. pneumoniae. 4,95 Importantly, resistance to penicillin is associated with some degree of resistance to all b-lactam antibiotics.…”

“…138 94. 167 By the mid-to late 1990s, rates of PNSP climbed to 24 to 44%, of which 10 to 19% were Pc-R. 7,84,85,87,88,93,132,168,169 The SENTRY study from 1999 to 2003 cited Pc-R rates of 14.7% in Europe, 12.7% in Latin America, and 15.9% in North America, respectively. 142 The incidence of PNSP in the United States appears to have plateaued with Pc-R rates 15% 3,7,70, 93,142 (Fig.…”

Penicillin-Resistant <i>Streptococcus pneumoniae</i> in Iran

“…pneumoniae to chloramphenicol, trimethoprim-sulfamethoxazole, and tetracycline limits the therapeutic effects of these antibiotics. Erythromycin-resistant strains among patients with pneumonia in some regions of European and Asian countries and treatment failure of pneumococcal meningitis with extended spectrum cephalosporins, ceftriaxone and cefotaxime in Europe and the USA [9][10][11] have further complicated the treatment of pneumococcal infections such that the current initial empirical treatment of infections need to be altered. Although there are various reports on the PRSP from Asian countries [4,6,[12][13][14] , there is no authentic data on this issue from Iran.…”

Prevalence of Ceftriaxon-Sensitive Pneumococci Infection and Use of E- Test for Patients Admitted to Ghaem and Imam Reza Hospitals During a Two-Year Period

“…Moreover, in a study conducted in Riyadh, Kingdom of Saudi Arabia, from February 2000 and November 2001, including 78 isolates of S. Pneumonia from different samples (blood, cerebrospinal fluid, bone, and peritoneal fluid) only 1.28% of isolates were resistant to Ceftriaxone (24) although authors suggested Ceftriaxone for treating invasive pneumococcal infections other than the central nervous system infections (25). A large study included 1,000 clinical isolates of S pneumonia, collected by U.S. laboratories in 2001-2002 showed that nearly 2% of isolates were resistant to Ceftriaxone (26). The rate of resistance to Ceftriaxone in our study was similar to the other studies (2.86%).…”