Antimicrobial susceptibility of Streptococcus pneumoniae in eight European countries from 2001 to 2003

Increase in numbers of β-lactam-resistant invasive Streptococcus pneumoniae in Brazil and the impact of conjugate vaccine coverage

A comprehensive investigation of invasive Streptococcus pneumoniae was carried out in Brazil as part of the programme of the national epidemiological surveillance system. The investigation provided data on the trends of resistance to antimicrobial agents. A total of 6470 isolates of S. pneumoniae collected in the country from 1993 to 2004 were tested. During this period of time, the number of penicillin-resistant strains rose from 10.2 to 27.9%. The proportions of intermediate and high-level resistant strains in 1993, which were 9.1 and 1.1%, respectively, rose to 22.0 and 5.9% in 2004. Geometric mean MICs for penicillin increased after the year 2000, to 0.19 microg ml(-1) in 2004; most of these isolates were from patients with pneumonia and from children under 5 years old, and belonged to serotype 14. There was a significant increase in the number of isolates belonging to serotypes included in the 7-valent conjugate vaccine from children under 5 years old: from 48.6% in 1993 to 69.6% in 2004, mainly related to an increase in the frequency of serotype 14 isolates. From 2000 to 2004, meningitis isolates showed higher resistance rates to cefotaxime (2.6%) compared to non-meningitis isolates (0.7%); percentages of isolates resistant to trimethoprim-sulfamethoxazole, tetracycline, erythromycin, chloramphenicol and rifampicin were 65, 14.6, 6.2, 1.3 and 0.7 %, respectively. No levoflaxin resistance was observed. Multidrug resistance was identified in 4.6% of isolates, of which 3.8% were resistant to three classes, 0.7% to four classes and 0.1% to five classes of antimicrobial agent. The study provides valuable information that may support empirical antimicrobial therapy for severe S. pneumoniae infections in Brazil, and emphasizes the need for conjugate pneumococcal vaccination.

Emergence and epidemiology of fluoroquinolone-resistant Streptococcus pneumoniae strains from Italy: report from the SENTRY Antimicrobial Surveillance Program (2001–2004)

Fluoroquinolones are key antimicrobials in the treatment of more serious pneumococcal infections, especially for treating infections caused by penicillin-resistant strains. Increased use of newer fluoroquinolones should be accompanied by greater surveillance efforts to monitor resistance development as well as clonal dissemination. Streptococcus pneumoniae (n=551) collected from 3 medical centers in Italy (Catania, Genoa, and Rome) over a period of 4 years (2001-2004) as part of the SENTRY Antimicrobial Surveillance Program were susceptibility tested against >30 antimicrobials using reference broth microdilution methods. Mutations in the quinolone resistance-determining region (QRDR) were characterized by PCR and sequencing of parC, parE, and gyrA. Epidemiological relationships among levofloxacin-resistant isolates were determined using ribotyping, PFGE, serotyping combined with antimicrobial resistance profiles augmented by QRDR mutation patterns. Eighty-three (15.1%) isolates showed reduced susceptibility to ciprofloxacin (MIC>or=4 microg/mL) and 31 (5.6%) were resistant to levofloxacin. In 2001, all pneumococcal isolates were susceptible to levofloxacin and resistance rapidly emerged in all 3 medical centers in 2002. The overall rates of levofloxacin resistance in 2002-2004 were the following: Catania 10.9%, Genoa 3.3%, and Rome 6.5%. All resistant strains showed at least one mutation in parC and gyrA. Each isolate from Genoa with a unique resistance phenotype also showed distinct ribotype/PFGE, serotype, and QRDR mutation patterns. All isolates from Catania (n=19) showed an identical ribotype/PFGE pattern (333.3/A1); however, 3 distinct clusters could be identified based on further resistance phenotype, serotypes, and QRDR mutation pattern analysis. Two clusters were documented among isolates from Rome based on ribotype/PFGE. One isolate from Genoa shared ribotype/PFGE (333.3/A1) and serotype (9 not V) results with clusters from the other 2 institutions monitored, indicating clonal dissemination between the geographically diverse cities. In conclusion, fluoroquinolone resistance rates have increased among S. pneumoniae recovered in Italian medical centers evaluated by the SENTRY Program. Although resistance has emerged in many epidemiologically distinct strains, clonal dissemination seems to be a key contributing factor for increasing resistance to fluoroquinolones among pneumococci in this nation.

Failure of levofloxacin treatment in community-acquired pneumococcal pneumonia

Background

Streptococcus pneumoniae is the leading cause of community-acquired pneumonia (CAP). High global incidence of macrolide and penicillin resistance has been reported, whereas fluoroquinolone resistance is uncommon. Current guidelines for suspected CAP in patients with co-morbidity factors and recent antibiotic therapy recommend initial empiric therapy using one fluoroquinolone or one macrolide associated to other drugs (amoxicillin, amoxicillin/clavulanate, broad-spectrum cephalosporins). Resistance to fluoroquinolones is determined by efflux mechanisms and/or mutations in the parC and parE genes coding for topoisomerase IV and/or gyrA and gyrB genes coding for DNA gyrase. No clinical cases due to fluoroquinolone-resistant S. pneumoniae strains have been yet reported from Italy.

Case presentation

A 72-year-old patient with long history of chronic obstructive pulmonary disease and multiple fluoroquinolone treatments for recurrent lower respiratory tract infections developed fever, increased sputum production, and dyspnea. He was treated with oral levofloxacin (500 mg bid). Three days later, because of acute respiratory insufficiency, the patient was hospitalized. Levofloxacin treatment was supplemented with piperacillin/tazobactam. Microbiological tests detected a S. pneumoniae strain intermediate to penicillin (MIC, 1 mg/L) and resistant to macrolides (MIC >256 mg/L) and fluoroquinolones (MIC >32 mg/L). Point mutations were detected in gyrA (Ser81-Phe), parE (Ile460-Val), and parC gene (Ser79-Phe; Lys137-Asn). Complete clinical response followed treatment with piperacillin/tazobactam.

Conclusion

This is the first Italian case of community-acquired pneumonia due to a fluoroquinolone-resistant S. pneumoniae isolate where treatment failure of levofloxacin was documented. Molecular analysis showed a group of mutations that have not yet been reported from Italy and has been detected only twice in Europe. Treatment with piperacillin/tazobactam appears an effective means to inhibit fluoroquinolone-resistant strains of S. pneumoniae causing community-acquired pneumonia in seriously ill patients.

Activity of the new quinolones WCK 771, WCK 1152 and WCK 1153 against clinical isolates of Streptococcus pneumoniae and Streptococcus pyogenes

OBJECTIVES AND METHODS

The new fluoroquinolones WCK 771, WCK 1152 and WCK 1153 were developed to overcome quinolone resistance in Gram-positive bacteria. The activity of these new quinolones was tested against 159 clinical isolates of Streptococcus pneumoniae and 52 clinical isolates of Streptococcus pyogenes using the microbroth dilution method.

RESULTS

MIC50/MIC90 values (mg/L) of WCK 771, WCK 1152 and WCK 1153 for quinolone-susceptible S. pneumoniae (n = 119; 54 penicillin G-susceptible, 53 penicillin G-intermediate, and 12 penicillin G-resistant strains) were 0.25/0.5, 0.03/0.06 and 0.016/0.03, respectively. MIC50/MIC90 values (mg/L) for quinolone-resistant pneumococci (n = 40) increased to 4/16, 0.25/1 and 0.125/0.5, respectively. Against S. pyogenes, WCK 771, WCK 1152 and WCK 1153 were also highly active with MIC50/MIC90 values (mg/L) of 0.25/0.25, 0.03/0.06 and 0.03/0.03, respectively.

CONCLUSIONS

Overall, WCK 771 was highly active against quinolone-susceptible, but not against quinolone-resistant S. pneumoniae, whereas WCK 1152 and WCK 1153 were more potent and were able to overcome quinolone resistance in both S. pneumoniae and S. pyogenes.