Genetic relatedness of resistant and multiresistant Streptococcus pneumoniae strains,recovered in the Athens area,to international clones

The prevalence of resistance to antibiotics was examined among 318 Streptococcus pneumoniae strains isolated during 1998 and 1999 in a children's hospital in Athens. The rate of resistance to penicillin was 25.8% (intermediate 22%, resistant 3.8%); 42.5% of the strains were resistant to > or = 1 antibiotic and 20% were multidrug resistant. Resistance to penicillin was lowest in invasive strains (8.3%) and highest in ear isolates (31%). A review of the same microbiology laboratory's records revealed that there has been a gradual increase in penicillin resistance since 1988-1989, when it was 5%. Capsular types were determined for 77 strains resistant to > or = 1 antibiotic, and 69 (90%) of them belonged to the following five serotypes: 19F, 14, 9V, 23F, and 6B. Seventy-five strains were analyzed by pulsed-field gel electrophoresis (PFGE) and 59/75 (79%) shared five electrophoretic types. The largest cluster consisted of 19 serotype 19F strains, of which 18 were nonsusceptible to penicillin and most were multidrug resistant and shared a common and distinct electrophoretic pattern not resembling any known clone. A group of 17 strains that were nonsusceptible to penicillin belonged to serotypes 9V (10), 14 (6), and 19F (1) and shared a common PFGE type similar to the international clone Spain9V-3. Seven serotype 23F strains, of which five were multidrug resistant, belonged to the international clone Spain23F-1. Among the strains susceptible to penicillin but resistant to non-beta-lactam antibiotics, the largest cluster consisted of 13 isolates resistant to erythromycin that belonged to serotype 14 and shared an electrophoretic pattern characteristic of the clone England14-9. Finally, three serotype 6B strains were penicillin susceptible and multidrug resistant and had features similar to the Mediterranean 6B clone. The introduction and spread of several antibiotic-resistant international clones accounts at least in part for the increase in pneumococcal resistance observed in recent years in the Athens metropolitan area.     

Stability of penicillin-susceptible and nonsusceptible clones of Streptococcus pneumoniae in southern Sweden

Understanding what determines the stability and global spread of pneumococcal clones is important for future public health interventions. This requires better knowledge about the stability and distribution of existing clones. In this study we characterized and compared penicillin nonsusceptible (PNSP) and susceptible pneumococci (PSP) from southern Sweden. A total of 166 isolates of Streptococcus pneumoniae, recovered in Malmohus County between 1982 and 1997, were analyzed with molecular and microbiological techniques; 107 PNSP isolates of serogroup 15, collected between 1992 and 1995, and 15 PNSP isolates of serogroup 9, isolated in 1996 and 1997, were studied. In addition, PSP of serogroups 9 and 15, isolated approximately 10 years apart, were studied; 23 of serogroup 9 and 21 of serogroup 15, isolated in 1982-1983 and 1992-1993. As expected, a high degree of homogeneity was found in the PNSP isolates, where all the isolates of serogroup 9 belonged to the same clone, Spain(9V)-3, and the majority of the serogroup 15 isolates belonged to the Sweden(15A)-25 clone. The remaining PNSP isolates of serogroup 15 belonged to a clone found in The Netherlands and Greece. An unexpectedly high degree of clonality and stability of the PSP isolates was observed. Isolates representing clones that remained stable for over 10 years were found among both serogroups. These results indicate that factors, other than antimicrobial resistance, play an important part in establishing successful clones of S. pneumoniae, and these factors may be instrumental in determining the success or failure of clones after they acquire resistance.     

Serotyping and antibiotic resistance of Streptococcus pneumoniae isolated from pediatric infections in central Greece

Objective: To determine the distribution of serogroups/serotypes and antibiotic resistance pattern of Streptococcus pneumoniae isolated from pediatric infections in central Greece.
Methods: In total, 306 S. pneumoniae strains isolated from children, aged from 18 days to 14 years (median 18 months), during a 21-month period, from different specimen sources, were studied. Susceptibility testing was carried out by the Kirby-Bauer method and by the Etest, and serotyping by the Quellung reaction.
Results: Of the S. pneumoniae isolates, 3.9% were highly resistant to penicillin (PR), while 17.6% were intermediately resistant (IPR). PR and IPR isolates were found to be, in general, more resistant to other antibiotics than penicillin-susceptible isolates. The PR and IPR isolates belonged to the serogroup/serotypes 19, 23, 9, 6 and 14 (in descending order of frequency). The penicillin-susceptible isolates belonged to 20 different groups/serotypes, the most common being 19, 6, 14, 9, 3, 23 and 1 (in descending order of frequency). Serogroup 23 was often found to be multiresistant.
Conclusions: Resistance to penicillin in S. pneumoniae isolates is relatively low and differs according to the specimen type. All the pneumococcal serogroups/serotypes isolated from the children were found to be included in the 23-valent polysaccharide vaccine. Most of the children with a pneumococcal infection, however, were less than 2 years old and could not be protected by the existing vaccine.     

Pneumococcal resistance to antimicrobial agents in the province of Québec, Canada.

The serogroup/serotypes (SGTs) and antimicrobial susceptibilities to 10 antimicrobial agents of 110 clinical strains of Streptococcus pneumoniae were determined. Strains intermediately resistant or highly resistant to penicillin G (80 of 110) belonged predominantly to SGTs 23 (45.0%), 19 (13.7%), 6 (10.0%), 9 (6.2%), and 14 (3.7%). The MICs of all cephalosporins, tetracycline, trimethoprim-sulfamethoxazole, and chloramphenicol increased along with the MICs of penicillin G. However, erythromycin resistance and clindamycin resistance were observed more frequently among the intermediately penicillin-resistant strains. Multiple resistance was observed for 32 strains, of which 25 were highly resistant to penicillin G and belong to SGT 23F. All strains were susceptible to vancomycin.     

Characteristics of the major etiologic agents of bacterial meningitis isolated in Poland in 1997-1998

Bacterial meningitis remains a major cause of morbidity and mortality worldwide, especially in children. In this paper, we present the results of the first two years (1997-98) of activity of the National Reference Centre for Bacterial Meningitis (NRCBM) on the etiologic agents of bacterial meningitis in Poland. Of the 220 isolates sent to the NRCBM, the most frequently identified was Neisseria meningitidis (n = 90, 40.9%), followed by Haemophilus influenzae (n = 58, 26.4%), and Streptoccus pneumoniae (n = 46, 20.9%). Of the meningococcal isolates, 88.9% belonged to serogroup B and 10.0% to serogroup C, and the most prevalent serotype was 22 (43.3%). Most meningococci were highly sensitive to penicillin; however, 10% of them had decreased susceptibility to penicillin. More than 90% of H. influenzae belonged to serotype b, and all were susceptible to third generation cephalosporins and chloramphenicol. A broad distribution of serotypes was found among pneumococcal isolates, of which the most common were serotypes 3 and 8. Penicillin nonsusceptible isolates constituted 13% of all pneumococcal isolates. Three of the resistant pnemococci belonged to serotype 23F. Data presented in this paper demonstrate the current epidemiological situation of bacterial meningitis in Poland.     

Evolution of antibiotic resistance and serogroups of Streptococcus pneumoniae over the 1997-2003 period in Brittany

At this time, many antibiotics have decreased activity against Streptococcus pneumoniae, a major agent of infectious disease. In this study, we evaluated antibiotic susceptibility and serogroups of strains isolated from bacteraemia, meningitis and acute otitis media in adults and children over the 1997-2003 period in Brittany, France. In 2003, 62% of the isolates were not susceptible to penicillin and 11% were fully resistant. The prevalence of erythromycin resistance was 63%. Resistance rates were higher among isolates recovered from children than adults. Serogroups 19 and 14 were the most frequently isolated, especially the 19 one among children. The emergence of this serogroup might be a consequence of the use of heptavalent conjugate vaccine introduced in 2001 in France. Future surveillance after vaccination will be needed to detect emerging serogroups and resistance among S. pneumoniae.     

Extremely high incidence of macrolide and trimethoprim-sulfamethoxazole resistance among clinical isolates of Streptococcus pneumoniae in Taiwan

From January 1996 to December 1997, 200 isolates of Streptococcus pneumoniae recovered from 200 patients treated at National Taiwan University Hospital were serotyped and their susceptibilities to 16 antimicrobial agents were determined by the agar dilution method. Sixty-one percent of the isolates were nonsusceptible to penicillin, exhibiting either intermediate resistance (28%) or high-level resistance (33%). About two-fifths of the isolates displayed intermediate or high-level resistance to cefotaxime, ceftriaxone, cefepime, imipenem, and meropenem. Extremely high proportions of the isolates were resistant to erythromycin (82%), clarithromycin (90%), and trimethoprim-sulfamethoxazole (TMP-SMZ) (87%). Among the isolates nonsusceptible to penicillin, 23.8% were resistant to imipenem; more than 60% displayed resistance to cefotaxime, ceftriaxone, cefepime, and carbapenems; 96.7% were resistant to erythromycin; and 100% were resistant to TMP-SMZ. All isolates were susceptible to rifampin and vancomycin. The MICs at which 50% and 90% of the isolates were inhibited were 0.12 and 1 microgram/ml, respectively, for cefpirome, and 0.12 and 0.25 microgram/ml, respectively, for moxifloxacin. Six serogroups or serotypes (23F, 19F, 6B, 14, 3, and 9) accounted for 77.5% of all isolates. Overall, 92.5% of the isolates were included in the serogroups or serotypes represented in the 23-valent pneumococcal vaccine. The incidence of macrolide and TMP-SMZ resistance for S. pneumoniae isolates in Taiwan in this study is among the highest in the world published to date.     

Characterization of penicillin intermediate serotypes of Streptococcus pneumoniae carried by human immunodeficiency virus-infected adults and healthy children in Uganda

There are little data on the genetic relatedness between antibiotic-resistant pneumococcal isolates colonizing the Ugandan population. Penicillin-intermediate pneumococci of serogroups or serotypes rarely or not previously reported as being penicillin nonsusceptible were selected out of 166 isolates representing 26 capsular serogroups or serotypes isolated from Ugandan children in 1995 and human immunodeficiency virus (HIV) infected Ugandan adults in 2004-2005. Pairs of penicillin-intermediate pneumococci of the same serogroup or serotype present in both patient populations were characterized further by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Seven such pairs of isolates were found and included serogroups 7, 11, 15B/C, and 16 as well as serotypes 13, 21, and 35B. PFGE of these seven pairs showed no clonality between serogroups or serotypes, and clonality only within serogroup 11 and serotype 13. MLST of the 14 individual isolates revealed 13 different sequence types (STs), 11 of which had not previously been recorded. Comparisons with all known STs revealed that most of these strains were related only to strains of the same serotype in other countries, with these related strains frequently also being penicillin intermediate. These findings suggest that penicillin nonsusceptibility in Uganda is likely due to the introduction of antibiotic-resistant pneumococcal clones into Uganda rather than development of resistance within the country.     

Trends in drug resistance, serotypes, and molecular types of Streptococcus pneumoniae colonizing preschool-age children attending day care centers in Lisbon, Portugal: a summary of 4 years of annual surveillance

Of the nasopharyngeal cultures recovered from 942 day care center (DCC) attendees in Lisbon, Portugal, 591 (62%) yielded Streptococcus pneumoniae during a surveillance performed in February and March of 1999. Forty percent of the isolates were resistant to one or more antimicrobial agents. In particular, 2% were penicillin resistant and 20% had intermediate penicillin resistance. Multidrug resistance to macrolides, lincosamides, and tetracycline was the most frequent antibiotype (17% of all isolates). Serotyping and molecular typing by pulsed-field gel electrophoresis were performed for 202 out of 237 drug-resistant pneumococci (DRPn). The most frequent serotypes were 6B (26%), 14 (22%), 19F (16%), 23F (10%), and nontypeable (12%). The majority (67%) of the DRPn strains were representatives of nine international clones included in the Pneumococcal Molecular Epidemiology Network; eight of them had been detected in previous studies. Fourteen novel clones were identified, corresponding to 26% of the DRPn strains. The remaining 7% of the strains were local clones detected in our previous studies. Comparison with studies conducted since 1996 in Portuguese DCCs identified several trends: (i) the rate of DRPn frequency has fluctuated between 40 and 50%; (ii) the serotypes most frequently recovered have remained the same; (iii) nontypeable strains appear to be increasing in frequency; and (iv) a clone of serotype 33F emerged in 1999. Together, our observations highlight that the nasopharynxes of children in DCCs are a melting pot of successful DRPn clones that are important to study and monitor if we aim to gain a better understanding on the epidemiology of this pathogen.     

Epidemiology of penicillin resistance in Streptococcus pneumoniae isolates in Kayseri, Turkey

Objective   To determine the penicillin resistance and serotype distribution of Streptococcus pneumoniae strains and to identify clonal relationships of isolates resistant to penicillin by means of pulsed-field gel electrophoresis (PFGE).
Methods   In total, 193 S . pneumoniae strains were isolated from clinical specimens between November 1997 and January 2000. Susceptibility testing was carried out by E test, and serotyping by the Quellung reaction. Clonal relationship was analyzed by using PFGE with sma I endonuclease.
Results   Of the S. pneumoniae isolates, 23% were intermediately resistant to penicillin. There were no high-level resistant pneumococci. The majority of isolates intermediately resistant to penicillin were of serogroups/serotypes 19, 23, 14 and 1, in descending order of frequency. There were eight major clones in strains intermediately resistant to penicillin. It was seen that serogroups in the 23-valent polysaccharide vaccine, 7-valent, 9-valent, and 11-valent vaccine formulations caused 92%, 75%, 78% and 87% of pneumococcal diseases in our region, respectively.
Conclusion   Penicillin resistance in S. pneumoniae is relatively uncommon in Kayseri. All vaccine formulations can prevent the majority of pneumococcal diseases, and there is genetic heterogeneity in intermediately penicillin-resistant pneumococci in this region.     

Multicentre Study of the Molecular Epidemiology, Serotypes and Antimicrobial Susceptibility Patterns of Invasive Streptococcus pneumoniae Invasive Isolated from Children in the Ille de France Area

Between January 1997 and April 2002, 73 consecutive invasive strains of Streptococcus pneumoniae were isolated from children under 16 years of age in four hospitals in suburban Paris. Their genetic diversity was investigated by serotyping and analysis of pulsed-field gel electrophoresis restriction patterns. Antibiotic susceptibility patterns were analysed by disk susceptibility testing and determination of minimal inhibitory concentrations. The genetic basis of macrolide resistance was investigated by polymerase chain reaction. Studies of penicillin and vancomycin tolerance were performed for each strain. Despite the high prevalence (45.2%) of penicillin-nonsusceptible Streptococcus pneumoniae, resistance to amoxicillin (1.4%) was rare, and no strain was resistant to cefotaxime. Overall, 4.1% of pneumococcal strains were resistant to penicillin. Penicillin or vancomycin tolerance was not detected in any of the 73 strains studied. Of the erythromycin-resistant strains (48%), all but one carried the ermB gene. No strains showing a decreased susceptibility to ciprofloxacin (MIC, >4 mg/l) or overexpressing an efflux pump inhibited by reserpine were isolated. The serotypes found, in order of frequency, were as follows: 18C, 14, 6B, 19F, 19A, 9V, 23F, 1, 7F, 9A, 38. Strains of penicillin-nonsusceptible Streptococcus pneumoniae belonged predominantly to serotypes 14, 6B, 9V, 9A, 23F, 19F and 19A. The seven-valent conjugated vaccine covered 85.5% of the serogroups isolated in children under 2 years of age and 65.6% of the serogroups identified in children over 2 years of age. The genetic analysis showed a high identity for some serotypes, such as 14/9V, 6B and 23F. The use of the seven-valent conjugated vaccine is a critical measure to prevent invasive pneumococci infections in children in the Ille de France area.     

Biochemical and serological characterization of Bacteroides intermedius strains isolated from the deep periodontal pocket.

Fifty-one fluorescence-positive black-pigmented Bacteroides strains obtained from 51 patients with deep periodontal pockets (greater than 6 mm) were identified and characterized. Fifty of these strains were presumptively identified as Bacteroides intermedius according to the indole reaction. This was confirmed by further biochemical characterization. The 50 strains from diseased sites were then compared with 16 B. intermedius strains isolated from periodontally healthy individuals with no signs of destructive periodontal disease. Tests for antimicrobial susceptibility showed similar patterns for all 50 pocket-derived strains, except for one beta-lactamase-positive strain that was resistant to penicillin G and ampicillin. Forty-seven strains were tested for binding of three monoclonal antibodies defining three distinct serogroups of B. intermedius. Thirty-one strains belonged to serogroup I, three to serogroup II and thirteen to serogroup III. In comparison to the strains from the shallow periodontal pockets, serogroup I was significantly overrepresented in the patient group with periodontal disease. We conclude that saccharolytic black-pigmented Bacteroides species from deep periodontal pockets constituted, with very rare exceptions, a biochemically homogeneous but antigenically heterogeneous group of B. intermedius and that serogroup I is predominantly found in deep periodontal lesions.     

Inferring the potential success of pneumococcal vaccination in Italy: serotypes and antibiotic resistance of Streptococcus pneumoniae isolates from invasive diseases

To evaluate the potential impact of antipneumococcal vaccination in Italy, Streptococcus pneumoniae isolates from invasive disease were collected from 65 laboratories in the years 1997-2000. Of the 503 isolates examined, 15% were from children <5 years and 34% from adults > or = 65 years. The most frequent serogroups were, in ranking order, 14, 19, 6, and 23. Overall, 93.8% of the isolates belonged to serogroups enclosed in the 23-valent polysaccharide vaccine. Among children isolates, serotypes 14, 6B, and 23F comprised 60% of the isolates; overall, 72% of the isolates belonged to serotypes included in the heptavalent conjugate vaccine. Penicillin nonsusceptible isolates (10%) belonged to a limited number of serogroups, being more common in serogroups 19 and 9 and in the nonvaccine serogroups 24 and 35. Erythromycin-resistant isolates (29%) belonged to several serogroups, more frequently to serogroups 14, 6, and 19. Both vaccines are potentially able to prevent the majority of resistant infections in the respective age groups in Italy.     

Bacteriological and epidemiological data on Streptococcus pneumoniae in the hospital of southern Reunion Island

We studied the epidemiology of Streptococcus pneumoniae in southern Reunion Island from 1993 to 1998. Data were collected from the Centre hospitalier Sud Reunion. Incidence of pneumonia was calculated by applying published ratios to two different types of data (bacteriological, clinical). Survey of pneumococci showed that antimicrobial resistance of S. pneumoniae to penicillin G appeared in 1994 and reached high levels in 1998. We confirmed the increase of multiresistant strains among penicillin resistant S. pneumoniae. Serotyping the penicillin resistant S. pneumoniae has shown that these strains belonged to serogroups 9, 14, 19, 23. The MIC determined in PRP showed that imipenem was the most active agent among beta-lactamin antibiotics followed by ceftriaxone. Strains with high resistance to amoxicillin are rare. Annual incidence of meningitis was almost 0.4 per 100,000 inhabitants. Estimation of pneumonia incidence was between 44 and 78 per 100,000 inhabitants. Incidence in Reunion Island is twice to three times lower than the incidence in France. Death rate from pneumoniae (10%) is similar to that in France. In the course of the study, the number of isolated S. pneumoniae increased. Changing socio-economic conditions are probably associated with the emergence of PRP since 1994 and the increase in numbers of infections. Pneumococcal infections in Reunion Island are becoming a public health problem of the same importance as in France.     

Pneumococcal acute otitis media in children

Objectives   To evaluate the clinical and laboratory findings of Streptococcus pneumoniae acute otitis media in children during a 1 year period.
Methods   From October 1995 to September 1996, 113 children aged 2 months to 14 years (median 18 months), with S. pneumoniae acute otitis media were studied. Susceptibility testing was performed by the Kirby-Bauer method and the E- test, and serotyping by the Quellung reaction.
Results   E- test assays detected five isolates (4.4%) to be highly resistant to penicillin and 13 (11.5%) that had intermediate resistance. All isolates were found to be susceptible to vancomycin, rifampicin and cefotaxime. In total, 25 isolates (22.1%) were resistant to one or more drugs. Fifty per cent of the penicillin-resistant or intermediately resistant S. pneumoniae isolates were resistant to multiple drugs, whereas only 2.1% of the penicillin-susceptible isolates were resistant to multiple drugs. The predominating serogroups of the isolates with reduced susceptibility to penicillin were the 19 (61.1%), 9 (16.7%), 23 (11.1%), 6 (5.5%) and 14 (5.5%) whereas those of the susceptible isolates were the 19 (26.3%), 14 (13.7%), 3 (11.6%), 6 (11.6%), 9 (8.4%), 1 (5.3%) and 12 (5.3%).
Conclusions   Streptococcus pneumoniae isolates from children with acute otitis media were penicillin-insensitive in 15.9%. The multiresistant S. pneumoniae isolates belonged to serogroups: 19 (45.4%), 9 (27.3%), 6 (18.2%) and 23 (9.1%).     

Observatoire régional du pneumocoque en région Pays de la Loire : résistance de Streptococcus pneumoniae aux antibiotiques en 2007

Objectives

Between 1st January and 31st December 2007, 331 Streptococcus pneumoniae strains were collected from 20 participating laboratories in the Pneumococcus Network Pays de la Loire county to assess their susceptibility to antibiotics and to evaluate serogroups of strains.

Method

The coordinating centre performed MICs of penicillin G, amoxicillin and cefotaxime by the reference agar dilution method. Results were interpreted according to CA-SFM breakpoints. Sensitivity to other antibiotics were studied and serotyping of each strain performed.

Results

Three hundred and thirty one strains were isolated in 2007. They were collected from 30 cerebrospinal fluids, 239 blood samples, 53 middle ear fluids and nine pleural fluids. The percentage of pneumococci with decreased susceptibility to penicillin G (PDSP) was 39% and was higher in children (51%) than in adults (35%). The PDSP were often multidrug resistants especially with a high percentage of resistance to erythromycin (87.6% versus 8.4% for pneumococci sensitive to penicillin G). Finally, the most prevalent serogroup was the serogroup 19 (29.6% of isolates).

Conclusion

A decrease of PDSP was observed since 2001 and high-level resistant strains to β-lactams remain low. The rate of PDSP in Pays de la Loire is in the national average.     

Evolution of Streptococcus pneumoniae serotypes and antibiotic resistance in Belgium—update (1994–98)

Objective To follow the evolution of capsular types and resistance of Streptococcus pneumoniae , isolated from deep sites.
Methods More than 100 Belgian laboratories permanently collect S. pneumoniae strains isolated from puncture specimens (blood, cerebrospinal fluid, middle ear fluid, etc.) and forward them to the reference center in Leuven, in order to determine the capsular serogroups and types (SGTs) and their resistance.
Results From 1994 to 1998, the 5486 S. pneumoniae strains examined belonged to 39 of the 46 currently identified SGTs. The 10 most frequent SGTs accounted for 78.9% of the isolates, and 97% of all isolates belonged to SGTs included in the 23-valent vaccine. Overall mortality of patients with pneumococcal bacteremia or meningitis was 9.7%, and 23.8% in patients over 80 years. From 1994 to 1998, resistance to penicillin (P) increased from 7.6% to 14.2%, to tetracycline (T) from 14.9% to 28.0%, and to erythromycin (E) from 22.9% to 31%. Triple resistance (PTE) increased from 0.9% in 1994 to 6.6% in 1998. Five SGTs (6, 9, 14, 19 and 23) accounted for 50% of the isolates, but for > 90% of the penicillin-resistant or erythromycin-resistant isolates.
Conclusions Resistance of S. pneumoniae to penicillin, erythromycin and tetracycline is steadily increasing and is concentrated in five serotypes included in the 23-valent pneumococcal vaccine. Increasing resistance and high mortality of invasive infections are an incentive to vaccinate vulnerable groups.     

Carriage of Antibiotic-Resistant Streptococcus pneumoniae in Greek Infants and Toddlers

The prevalence, resistance patterns and serotypes of antibiotic-resistant Streptococcus pneumoniae strains recovered from Greek carriers under 24 months of age were studied. From February 1997 to April 1998, nasopharyngeal cultures were performed in 1269 children (ages 2–23 months, median 11 months) living in various areas of central and southern Greece. Resistance (including both intermediate and resistant isolates) to one or more antimicrobial agents was found in 132 of the 421 (31%) Streptococcus pneumoniae isolates, as follows: penicillin, 9% intermediate, 7.6% resistant; cefotaxime, 5.2% intermediate, 0.5% resistant; erythromycin, 0.7% intermediate, 18.1% resistant; clindamycin, 0.2% intermediate, 12.4% resistant; tetracycline, 0.7% intermediate, 16.4% resistant; chloramphenicol, 12.4% resistant; and trimethoprim-sulfamethoxazole, 3.8% intermediate, 14.3% resistant. The MICs of penicillin for 66% of the penicillin-nonsusceptible pneumococci were 1–4 μg/ml. Multidrug resistance was found in 64% of penicillin-nonsusceptible and 37% of penicillin-susceptible strains. Sixty-two percent of the penicillin-susceptible, multidrug-resistant strains belonged to serotype 6B and were resistant to all five non-β-lactam agents tested. This notable serotype 6B resistance pattern was described for the first time in a previous study performed from December 1995 to February 1996 in the city of Patras, southwestern Greece. Seventy-two percent of antibiotic-resistant isolates belonged to serotypes 6B, 9V, 14, 18C, 19F and 23F. These results document the spread of resistant pneumococcal strains in central and southern Greece, many of which are multidrug resistant.     

Natural history of drug-resistant clones of Streptococcus pneumoniae colonizing healthy children in Portugal

A total of 3,539 Streptococcus pneumoniae (Pn) were recovered from 4,969 nasopharyngeal samples of children attending 13 day-care centers (DCCs) located in Lisbon, Portugal, during a surveillance study from January, 2001, through March, 2003, integrated in the European intervention project (EURIS, European Resistance Intervention Study). All Pn isolates were tested for anti-biotyping and drug-resistant pneumococci (DRPn) were further tested by serotyping and pulsed-field gel electrophoresis (PFGE). Overall carriage of Pn was very high (71.2%) and 39.9% of the isolates were resistant to antimicrobials (22.5% with decreased susceptibility to penicillin and 17.4% susceptible to penicillin and resistant to other antimicrobials). Serotypes 6B, 14, 23 F, 19F, and 19 A were prevalent among the 1,287 DRPn and 5.8% of the isolates were non-typeable. Eighty PFGE patterns were identified among 1,285 DRPn, and 93.1% of the DRPn belonged to 26 major clonal types that comprised: Pneumococcal Molecular Epidemiology Network (PMEN) clones (76.3%), Portuguese (PT)-DCC clones, previously detected in 1996-1999 (14.3%), and EURIS PT-DCC new clones, identified for the first time in the EURIS study, during 2001-2003 (9.4%). Comparing with previous Portuguese surveillance studies carried out since 1996, we observed that carriage increased from 47% to 71%, but no major changes were detected on the prevalence of pneumococcal serotypes. Moreover, although PMEN clones were predominant in all DCCs, in the present study the majority of them were gradually decreasing in time whereas several PT-DCC and new clones seemed to be increasing.     

Clonal groups of penicillin-nonsusceptible Streptococcus pneumoniae in Baltimore, Maryland: a population-based, molecular epidemiologic study

Few data are available on the molecular subtypes of all penicillin-nonsusceptible Streptococcus pneumoniae (PNSP) from a defined population base. Pulsed-field gel electrophoresis (PFGE), serotyping, and antibiotic susceptibility testing were performed for all available invasive PNSP isolates for which the penicillin (MIC) was > or =0.1 microg/ml from Baltimore, Md., during 1995-1996 (n = 143). The dendrogram analysis of PFGE patterns included 32 distinct clonal groups. Six major clonal groups included two-thirds of the PNSP strains. Major clonal groups 2, 3, 4, and 6 strains were genetically related to four previously described international clones and were all multidrug resistant. Major clonal group 3 was genetically related to the Tennessee(23F)-4 clone and contained all four strains for which the penicillin MIC was 8 microg/ml. Most of the clonal group 1 and 5 strains had intermediate susceptibility to penicillin and were rarely multidrug resistant. The latter clonal groups represent two previously undescribed penicillin-intermediate pneumococcal clones. Clonal group homogeneity was greater for serotype 9V, 19A, and 23F strains than for serotype 6A, 6B, 14, and 19F strains. The classification of PNSP strains into clonal groups is essential for future population-based epidemiologic studies of PNSP.