Antimicrobial susceptibilities and serotypes of invasive Streptococcus pneumoniae strains in Switzerland

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

Susceptibility testing results for Streptococcus pneumoniae isolates (n = 2,279) from eight European countries, examined in the PneumoWorld Study from 2001 to 2003, are presented. Overall, 24.6% of S. pneumoniae isolates were nonsusceptible to penicillin G and 28.0% were resistant to macrolides. The prevalence of resistance varied widely between European countries, with the highest rates of penicillin G and macrolide resistance reported from Spain and France. Serotype 14 was the leading serotype among penicillin G- and macrolide-resistant S. pneumoniae isolates. One strain (PW 158) showed a combination of an efflux type of resistance with a 23S rRNA mutation (A2061G, pneumococcal numbering; A2059G, Escherichia coli numbering). Six strains which showed negative results for mef(A) and erm(B) in repeated PCR assays had mutations in 23S rRNA or alterations in the L4 ribosomal protein (two strains). Fluoroquinolone resistance rates (levofloxacin MIC > or = 4 microg/ml) were low (Austria, 0%; Belgium, 0.7%; France, 0.9%; Germany, 0.4%; Italy, 1.3%; Portugal, 1.2%; Spain, 1.0%; and Switzerland, 0%). Analysis of quinolone resistance-determining regions showed eight strains with a Ser81 alteration in gyrA; 13 of 18 strains showed a Ser79 alteration in parC. The clonal profile, as analyzed by multilocus sequence typing (MLST), showed that the 18 fluoroquinolone-resistant strains were genetically heterogeneous. Seven of the 18 strains belonged to new sequence types not hitherto described in the MLST database. Europe-wide surveillance for monitoring of the further spread of these antibiotic-resistant S. pneumoniae clones is warranted.

Seven valent pneumococcal conjugate vaccine immunization in two Boston communities: changes in serotypes and antimicrobial susceptibility among Streptococcus pneumoniae isolates

BACKGROUND

Seven valent pneumococcal conjugate vaccine (PCV7) was licensed and introduced in 2000 for universal administration of children younger than 2 years of age and for selective immunization of children 2-5 years of age.

SPECIFIC AIMS

To identify changes in colonization and antimicrobial susceptibility among Streptococcus pneumoniae organisms after introduction of PCV7.

METHODS

Infants and children ages 2-24 months were enrolled in surveillance study of nasopharyngeal carriage of S. pneumoniae. Nasopharyngeal cultures for S. pneumoniae were performed at all well child visits and illness visits of children with acute otitis media. S. pneumoniae organisms were serotyped, and antimicrobial susceptibilities to penicillin, amoxicillin, trimethoprim-sulfamethoxazole and azithromycin were performed.

RESULTS

During the 3-year period (October 2000 through September 2003), nasopharyngeal colonization with vaccine serotypes declined from 22% to 2%, and nonvaccine serotypes increased from 7% to 16%. Rates of antibiotic resistance of S. pneumoniae isolates to penicillin, amoxicillin, azithromycin and trimethoprim-sulfamethoxazole were 29.3, 2.2, 26.5 and 28.1%, respectively.

CONCLUSIONS

PCV7 immunization produces a marked decline in vaccine serotypes carried in the nasopharynx of young children, with a coincident rise in the prevalence of nonvaccine serotypes. Important shifts in antimicrobial susceptibility have not been observed to date.

Antimicrobial resistance and serotype distribution of Streptococcus pneumoniae isolates from Crete, Greece

Susceptibility to 14 antibiotics was determined for 125 clinical isolates of Streptococcus pneumoniae collected over a 3-year period in Crete, Greece. Twenty-three isolates (18.4%) showed intermediate resistance and 15 (12%) high-level resistance to penicillin. Erythromycin, chloramphenicol, tetracycline, trimethoprim-sulphamethoxazole and sparfloxacin resistance rates were 16.8, 10.4, 19.2, 24.8 and 9.6%, respectively. Multiple resistance was observed in 22 strains. Vancomycin and levofloxacin were the most active agents tested. The most prevalent serotype among penicillin-susceptible pneumococci was 14, followed by 9, 7 and 1, while among penicillin-intermediate or -resistant strains serotype 23 was predominant followed by 19 and 9. These results show that as well as a high level of penicillin resistance in this region, some strains are also resistant to other antibiotics and may show multi-drug resistance.

Community-acquired pneumonia. A prospective outpatient study

We initiated a prospective study with a group of practitioners to assess the etiology, clinical presentation, and outcome of community-acquired pneumonia in patients diagnosed in the outpatient setting. All patients with signs and symptoms suggestive of pneumonia and an infiltrate on chest X-ray underwent an extensive standard workup and were followed over 4 weeks. Over a 4-year period, 184 patients were eligible, of whom 170 (age range, 15-96 yr; median, 43 yr) were included and analyzed. In 78 (46%), no etiologic agent could be demonstrated. In the remaining 92 patients, 107 etiologic agents were implicated: 43 were due to "pyogenic" bacteria (39 Streptococcus pneumoniae, 3 Haemophilus spp., 1 Streptococcus spp.), 39 were due to "atypical" bacteria (24 Mycoplasma pneumoniae, 9 Chlamydia pneumoniae, 4 Coxiella burnetii, 2 Legionella spp.), and 25 were due to viruses (20 influenza viruses and 5 other respiratory viruses). There were only a few statistically significant clinical differences between the different etiologic categories (higher age and comorbidities in viral or in episodes of undetermined etiology, higher neutrophil counts in "pyogenic" episodes, more frequent bilateral and interstitial infiltrates in viral episodes). There were 2 deaths, both in patients with advanced age (83 and 86 years old), and several comorbidities. Only 14 patients (8.2%) required hospitalization. In 6 patients (3.4%), the pneumonia episode uncovered a local neoplasia. This study shows that most cases of community-acquired pneumonia have a favorable outcome and can be successfully managed in an outpatient setting. Moreover, in the absence of rapid and reliable clinical or laboratory tests to establish a definite etiologic diagnosis at presentation, the spectrum of the etiologic agents suggest that initial antibiotic therapy should cover both S. pneumoniae and atypical bacteria, as well as possible influenza viruses during the epidemic season.

Two-year surveillance of antibiotic resistance in Streptococcus pneumoniae in four African cities

Worldwide spread of antibiotic resistance in Streptococcus pneumoniae is a major problem. However, data from West and North African countries are scarce. To study the level of resistance and compare the situations in different cities, a prospective study was conducted in Abidjan (Ivory Coast), Casablanca (Morocco), Dakar (Senegal), and Tunis (Tunisia), from 1996 to 1997. The resistances to eight antibiotics of 375 isolates were studied by E test, and the results were interpreted using the breakpoints recommended by the National Committee for Clinical Laboratory Standards. Overall, 30.4% of the isolates were nonsusceptible to penicillin G (25.6% were intermediate and 4.8% were resistant). Amoxicillin (96.3% were susceptible) and parenteral third-generation cephalosporins (92.7%) were highly active. Resistance to chloramphenicol was detected in 8.6% of the isolates. High levels of resistance were noted for erythromycin (28%), tetracycline (38.3%), and cotrimoxazole (36.4%). Resistance to rifampin was rare (2.1%). There were significant differences in resistance rates between individual countries. Multiple resistance was more frequent in penicillin-nonsusceptible isolates than in penicillin-susceptible isolates. Recommendations for treatment could be generated from these results in each participating country.

Prevention of acute mastoiditis: fact or fiction?

Acute mastoiditis is the most common complication of acute otitis media (AOM). In recent years routine antibiotic treatment for acute middle ear infections was questioned and even abandoned in some countries. The goal of our study was to investigate the influence of antibiotic treatment on the occurrence and clinical outcome of acute mastoiditis and to analyze the bacteriological findings. A retrospective case record study of 48 patients with 50 episodes of acute mastoiditis hospitalized at our tertiary-care center between 1992 and 1999 was performed. Twenty-three patients (48%) received antibiotic treatment before admission whereas 25 (52%) did not. The group of patients without antibiotic pretreatment were younger (mean, 6 years) than patients with antibiotics (mean, 18 years) and their referral was delayed. The most common isolated single pathogen was Streptococcus pneumoniae. All pneumococci were sensitive to penicillin. Acute mastoiditis may be the first clinical sign of a middle ear infection, especially in very young children. Adequate antibiotic pretreatment cannot invariably prevent the development of acute mastoiditis even in the absence of penicillin resistant pathogens.

Pneumococcal vaccine in patients with absent or dysfunctional spleen

Four patients (3 long-term Hodgkin disease survivors and 1 recipient of an allogeneic bone marrow transplant) developed severe infections with Streptococcus pneumoniae after staging splenectomy or due to functional hyposplenism after total body irradiation and bone marrow transplantation. Current guidelines for prevention of infection recommend pneumococcal immunization for patients with Hodgkin disease treated with splenectomy and others with functional hyposplenism. Booster vaccination after 5 years is also advised. Hospital- and community-based vaccination initiatives may help identify at-risk patients.

Antimicrobial susceptibilities and capsular types of invasive Streptococcus pneumoniae isolated in children in Mexico City

As part of the Sistema Regional de Vacunas (SIREVA) initiative, we conducted a surveillance study to determine the relative prevalence of capsular types of Streptococcus pneumoniae and antimicrobial susceptibility of invasive isolates in children less than 5 years old. We collected 220 isolates and found 33 of the 90 known types, with type 23F as the most common followed by types 6A+B, 14, 19F, and 19A. High penicillin resistance was found in 49 strains (22.2%), 31 belonging to type 23F. Twenty-nine (13.1%) were resistant to erythromycin, 95 (43.1%) were resistant to chloramphenicol, and 24 (10.9%) were resistant to cefotaxime. No strains were resistant to vancomycin.

The contribution of specific pneumococcal serogroups to different disease manifestations: implications for conjugate vaccine formulation and use, part II

To assess whether certain serogroups of Streptococcus pneumoniae are preferentially associated with specific disease manifestations, we analyzed all recent pneumococcal disease studies and assessed the relative frequency of isolation of each serogroup by clinical site (as a proxy for different disease states). In all age groups, serogroups 1 and 14 were more often isolated from blood, and serogroups 6, 10, and 23 were more often isolated from cerebrospinal fluid (CSF); in young children, serogroups 3, 19, and 23 were more often isolated from middle ear fluid (MEF). Serogroups represented in conjugate vaccines were isolated slightly less frequently from CSF than from blood or MEF. Nonetheless, serogroups in the 9-valent conjugate vaccine formulation still comprised approximately 75% of pneumococcal isolates from the CSF of young children in Europe and in the United States and Canada. These analyses indicate that pneumococcal conjugate vaccines could potentially prevent a substantial proportion of episodes of bacteremic disease, pneumonia, meningitis, and otitis media, especially in young children.

Which pneumococcal serogroups cause the most invasive disease: implications for conjugate vaccine formulation and use, part I

We analyzed >70 recent data sets to compare the serogroups causing invasive pneumococcal disease (IPD) with those represented in conjugate vaccine formulations. Five to 8 and 10-11 serogroups comprise at least 75% of pneumococcal isolates from young children and older children/adults, respectively, in each geographic region. Serogroups in the 7-valent formulation (4, 6, 9, 14, 18, 19, and 23) cause 70%-88% of IPD in young children in the United States and Canada, Oceania, Africa, and Europe, and <65% in Latin America and Asia. Serogroups in the 9-valent formulation (7-valent+1, 5) cause 80%-90% of IPD in each region except Asia (66%). Serogroup 1 accounts for >6% of IPD in each region, including Europe, except the United States and Canada and Oceania. In contrast, several serogroups not found in 7-, 9-, and 11-valent conjugate formulations are significant causes of disease in older children/adults. Nevertheless, each conjugate formulation could prevent a substantial IPD burden in each region and age group.

A 1-year study of antibiotic resistance among paediatric pneumococcal isolates in 1995 from four regions of France

The main object of this study was to describe the features of antibiotic resistance in pneumococci from children in four regions of France in 1995. Despite the high prevalence (40%) of pneumococci with diminished susceptibilty to penicillin (PDSP), resistance to amoxycillin (0.8%) and cefotaxime (0.4%) was rare; 16% of pneumococci were resistant to penicillin G (PRP, MIC > 1 mg/l). PDSP showed the expected resistance to macrolides (67%) and cotrimoxazole (57%) and were predominantly serotypes 23F, 14, 9 and 6. This study by the Regional Pneumococcal Observatories confirms the high prevalence and the main characteristics of antibiotic resistance among pneumococci isolated from children. Nevertheless, the resistance to all antibiotics was lower than that found in French multicentre, nationwide surveys, possibly because of differences in the mode of strain collection and geographic origin.

Austrian national survey of prevalence of antimicrobial resistance among clinical isolates of Streptococcus pneumoniae 1994-96

The antimicrobial susceptibilities of 1385 clinical isolates of Streptococcus pneumoniae obtained from 25 laboratories across Austria between December 1994 and January 1996 were tested. Minimal inhibitory concentration (MIC) values were determined in tests with penicillin, amoxycillin, amoxycillin/clavulanate, ceftriaxone, cefodizime, cefpirome, cefotaxime, cefpodoxime, cefadroxile, azithromycin, clarithromycin, josamycin and roxithromycin by the agar-dilution method. A total of 40 isolates (2.9%) demonstrated intermediate resistance (MIC 0.125-1 microg/ml) and 28 isolates (2.0%) had high-level resistance (MIC > or = 2 microg/ml) to penicillin. Excepting cefadroxil, with an MIC90 of 2 microg/ml, all other tested beta-lactams had MIC90s of 0.03-0.06 microg/ml. Penicillin-resistant strains were much more likely to be also resistant to the other beta-lactams. The macrolides proved to be very active compounds against pneumococci with MIC90s of 0.06 microg/ml (clarithromycin) and 0.25 microg/ml (all other macrolides). Regional differences within Austria with regard to antimicrobial resistance were not observed.

Sparfloxacin as alternative treatment to standard therapy for community-acquired bacteremic pneumococcal pneumonia

OBJECTIVE: To assess the effectiveness of a single daily dose of sparfloxacin in comparison with standard antibacterial therapy for the treatment of pneumococcal bacteremic community-acquired pneumonia (CAP). METHODS: The results were analyzed of four comparative trials in CAP, in which 107 adult patients with CAP confirmed by blood cultures positive for Streptococcus pneumoniae were included. Sparfloxacin was given at a loading dose of 400 mg followed by 200 mg daily. Comparator drugs included amoxycillin 3 g/day, amoxycillin/clavulanate 1.5/0.375 g/day and erythromycin 2 g/day. Dosing was for 7--14 days (mean 10 days). Success was determined by a combination of clinical and microbiological assessment and radiologic changes. RESULTS: Sparfloxacin was as effective as the comparator drugs, with an overall success rate of 80% at the end of treatment (comparators 78%), and a 79% success rate at follow-up (76% for comparators). There were no pneumococcal isolates resistant to sparfloxacin, but eight of 56 were either resistant (four) or had reduced susceptibility to penicillin G, and two strains were resistant to erythromycin. Tolerance to sparfloxacin was good, with fewer patients reporting drug-related adverse events (15.8%) than with the comparator drugs (33.3%). CONCLUSIONS: This analysis suggests that sparfloxacin would be an alternative candidate for empirical therapy in moderately severe CAP.

Epidemiology of penicillin resistance in Streptococcus pneumoniae isolates in eastern France

OBJECTIVE: To assess the rates of intermediate and high-level resistance to penicillin among Streptococcus pneumoniae isolates and to identify clonal relationship of isolates within the different serotypes by means of pulsed-field gel electrophoresis. METHODS: We studied all clinical isolates obtained between April 1995 and March 1996 from patients admitted to 10 hospitals in eastern France. Antibiotic susceptibility testing and serotyping were performed on all isolates. The genetic polymorphism of isolates susceptible, intermediately resistant and highly resistant to penicillin was studied by using pulsed-field gel electrophoresis with ApaI and SmaI endonucleases. RESULTS: The prevalence of intermediate and high-level resistance was respectively 30.3% and 9.7%. Diminished sensitivity to penicillin was mainly encountered in serotypes 6, 9V, 14 and 23F. The 9V isolates from the different hospitals were genetically closely related, unlike the 23F isolates. Different levels of resistance (MICs from 0.5 to 2 mg/L) were expressed by closely related isolates. Three 9V isolates, three capsular-type 14 isolates and one non-typeable isolate were genetically closely related in studies with the two endonucleases. CONCLUSIONS: The capsular type was not a good indicator of genetic relatedness. The level of penicillin resistance was independent of the clonal classification. Horizontal gene transfer may be the main factor determining the degree of resistance.

Antibiotic susceptibility of pneumococci isolated in Austria over a four-year period

The antibiotic susceptibility of pneumococci isolated from clinical specimens from 1991 through 1994 was investigated. Of 305 strains tested by the agar dilution method, 16 (5.2%) were resistant to penicillin (MICs > or = 0.12 mg/l). Of the resistant strains, 0.3% showed high-level resistance (MIC > or = 2 mg/l). The rate of resistance to erythromycin (MIC > or = 4 mg/l) was 2.3%, to tetracycline (MIC > or = 8 mg/l) 8.5%, to chloramphenicol (MIC > or = 8 mg/l) 1.0%, and to trimethoprim sulfamethoxazole (MIC > or = 3.2/64 mg/l) 3.3%. Penicillin-resistant strains showed significantly higher resistance to the other antibiotics tested. Resistance to penicillin was higher in isolates from the respiratory tract than in those from blood and cerebrospinal fluid (6.2% vs. 2.4%, respectively). There was no increase in penicillin resistance from 1991 through 1994 (5.3% vs. 4.9%, respectively).

Clindamycin resistance among erythromycin-resistant Streptococcus pneumoniae

The increasing proportion of Streptococcus pneumoniae isolates with reduced susceptibility to penicillin has created an urgent need for therapeutic alternatives to some beta-lactam agents. Clindamycin is an antimicrobial agent with excellent bioavailability after oral administration which has been considered for the therapy of community-acquired pneumococcal otitis media. Using the Etest methodology, we have studied the in vitro susceptibility of 59 erythromycin-resistant strains of S. pneumoniae to clindamycin, penicillin, trimethoprim-sulfamethoxazole, and rifampin. The study also addressed the impact of the susceptibility test medium [Mueller-Hinton (MH) vs IsoSensitest (Iso), both 5% blood supplement] on the results. A total of 20 isolates (37%) displayed constitutive clindamycin resistance on Iso blood agar, compared with only 11 (22%) on MH blood agar. The remaining nine strains found to be clindamycin susceptible on MH manifested resistance only with erythromycin induction. Resistance to penicillin, rifampin, and trimethoprim-sulfamethoxazole in erythromycin-resistant isolates was 83%, 2%, and 85%-89% (medium dependent), respectively. These results indicate that the choice of susceptibility test medium affects the expression (constitutive or inducible) of macrolide-lincosamide-streptogramin (MLS) resistance in S. pneumoniae. In addition, the common assumption that erythromycin resistance in S. pneumoniae implies clindamycin resistance may need to be reconsidered and routine susceptibility tests (including induction if MH medium is used) should be considered for MLS-class drugs.