Clonal distribution of penicillin-resistant Streptococcus pneumoniae 23F in France.

We studied the clonality of clinical isolates of Streptococcus pneumoniae 23F, the serotype most often associated with penicillin resistance in France. Clinical isolates obtained between November 1992 and April 1993 from nasopharyngeal samples from children with acute otitis media from different regions of the country were analyzed. The genetic polymorphism of penicillin-susceptible and -resistant 23F isolates (MIC, 2 mg/liter) was studied by pulsed-field gel electrophoresis. The resistant isolates were closely related, whereas the susceptible isolates were genetically heterogeneous. PCR amplification and restriction of the genes encoding penicillin-binding proteins (PBPs) 1A, 2B, and 2X also showed that the 24 resistant isolates had similar patterns which were very different from those of the susceptible isolates. All resistant isolates gave the same PBP pattern, with low affinities of PBPs for penicillin. Our results indicate that, in contrast to penicillin-susceptible 23F isolates, the penicillin-resistant 23F isolates have a single clonal origin, suggesting the rapid clonal spread of a resistant epidemic strain throughout the country.     

Clonal and temporal patterns of nasopharyngeal penicillin-susceptible and penicillin-resistant Streptococcus pneumoniae stains in children attending a day care center.

The nasopharyngeal carriage of penicillin-susceptible and penicillin-resistant Streptococcus pneumoniae (PSSp and PRSp, respectively) was analyzed in 116 children attending a day care center in Rouen, France, by three observation periods in November, January, and March of the winter of 1993 to 1994. The carriage rate of S. pneumoniae was found to be 47.7, 47.3, and 49.6% at each different observation period, and PRSp accounted for 42.2, 40.3, and 40.6% of pneumococcal isolates, respectively. The 52 isolates recovered in November were distributed in 34 electrophoretic types (ETs) by multilocus enzyme electrophoresis; 15 PRSp isolates, all of serotype 23F, belonged to a clonal complex of five ETs, representing the dominant population of PRSp in November. The temporal pattern of S. pneumoniae carriage was studied in 17 children who were colonized at the three periods by multilocus enzyme analysis of their isolates. The PSSp isolated, exhibiting distinct ETs, were transient only among these day care attendees. In contrast, most of the PRSp isolated in January and March belonged to the clonal complex. Thus, this PRSp population was resident in the day care center throughout the study period.     

Clonal structure and 21-year evolution of Streptococcus pneumoniae serotype 1 isolates in northern Spain

This study of 135 serotype 1 pneumococcal isolates (88 invasive and 47 non-invasive), collected between 1987 and 2007, gave eight sequence types (217, 227, 228, 304, 305, 306, 3860 and 3861) that group, using eBurst, into three different lineages and one singleton. The annual incidence of serotype 1 invasive episodes per million inhabitants increased from 1.8 in 1987–1993 to 4.0 in 1994–2000, and to 25.6 in 2001–2007. ST228 was the predominant clone until 1998. ST306 first appeared in 1998 and became the most prevalent sequence type (>80%) after the introduction, in June 2001, of the heptavalent pneumococcal conjugate vaccine.     

Clonal association between Streptococcus pneumoniae serotype 23A, circulating within the United States, and an internationally dispersed clone of serotype 23F

Streptococcus pneumoniae is an important pathogen in the United States and is associated with significant morbidity and mortality. Since the introduction of the seven-valent conjugate vaccine, a significant decline in pneumococcal disease has been reported. However, surveillance for pneumococcal disease remains essential, as the extent of cross protection against vaccine-related serotypes is still unclear. Further, any increase in non-vaccine-related serotypes also needs monitoring. We report on a new clonal association between a vaccine-related serotype, serotype 23A, obtained as part of the Active Bacterial Core surveillance, with an established internationally dispersed Pneumococcal Molecular Epidemiology Network (PMEN) clone, clone Colombia(23F)-26. Sixty-two isolates of serotype 23A collected from sterile sites during a 2-year period (2002 and 2003) were characterized. Twenty-one (34%) isolates were penicillin nonsusceptible, although none were fully resistant. Pulsed-field gel electrophoresis and multilocus sequence typing analysis showed that 24 (39%) of the serotype 23A isolates shared either genetic identity or high genetic relatedness with PMEN clone Colombia(23F)-26. Extensive variability was noted within the sequenced region of pbp2b in two penicillin-nonsusceptible isolates as well as in PMEN clone Colombia(23F)-26, suggesting that these isolates probably acquired penicillin resistance independently. The emergence of such new serotype and genotype associations highlights the dynamic nature of the pneumococcal population, necessitating continuous monitoring in the post-vaccine era.     

Novel penicillin-, cephalosporin-, and macrolide-resistant clones of Streptococcus pneumoniae serotypes 23F and 19F in Taiwan which differ from international epidemic clones

A cluster (14 of 18) of Streptococcus pneumoniae serotype 23F isolates that were resistant to penicillin (PEN), cephalosporin, and macrolide was found in one day care center in Kaohsiung, Taiwan. We analyzed the 18 isolates by pulsed field gel electrophoresis (PFGE). All but one serotype 23F isolate demonstrated identical PFGE patterns, which were different from the established pattern of the internationally spread Spanish 23F clone. The three strains of serotype 19F also showed a uniform pattern. These data strongly suggest that two novel clones of PEN-, cephalosporin-, and macrolide-resistant S. pneumoniae serotypes 23F and 19F are present in Taiwan.     

Phenotypic and genotypic characterization of two penicillin-susceptible serotype 6B Streptococcus pneumoniae clones circulating in Italy

Twenty-nine penicillin-susceptible serotype 6B strains isolated from patients with invasive diseases and from healthy carriers were examined by different genotyping methods. Ten groups were identified on the basis of the pulsed-field gel electrophoresis (PFGE) profiles, and two of these contained multiple isolates and were analyzed further. PFGE group 1 comprised 12 isolates, the majority of which had a multiresistant phenotype (resistance to erythromycin, clindamycin, tetracycline, chloramphenicol, and trimethoprim-sulfamethoxazole), corresponding to that of a clone previously described in the Mediterranean area and related to penicillin-resistant clone Spain(6B)-2. The pbp2b, pbp2x, dhf, and pspA genes of the isolates had identical restriction profiles; and the partial sequence of pspA was identical to that of clone Spain(6B)-2. In all isolates the resistance determinants erm(B) and tet(M) were inserted in a Tn1545-like element; 11 isolates carried cat as part of the integrated plasmid pC194. Multilocus sequence typing (MLST) performed with two isolates confirmed that their profiles corresponded to that of the Mediterranean clone. PFGE group 2 comprised nine strains, of which the majority showed no antibiotic resistance. Their pspA profiles were different, and the partial sequences obtained for two representative isolates indicated the presence of PspA proteins of different clades. The MLST profile of one strain was identical to that of a serotype 6B strain from the United Kingdom, while two other isolates were novel one-allele variants. This clone appears to be related (five of seven identical alleles) to two other internationally disseminated clones, Hungary(19A)-6 and Poland(23F)-16, both of which are penicillin resistant. The presence of antibiotic-susceptible isolates of this clone suggests that traits other than antibiotic resistance can make a clone successful.     

Nationwide surveillance of antimicrobial resistance in invasive isolates of Streptococcus pneumoniae in Taiwan from 2017 to 2019

Background/purposeStreptococcus pneumoniae causes pneumonia and other invasive diseases, and is a leading cause of mortality in the elderly population. The present study aimed to provide current antimicrobial resistance and epidemiological profiles of S. pneumoniae infections in Taiwan.MethodsA total of 252 nonduplicate S. pneumoniae isolates were collected from patients admitted to 16 hospitals in Taiwan between January 2017 and December 2019, and were analyzed. The minimum inhibitory concentration of antibiotics was determined using the Vitek 2 automated system for antimicrobial susceptibility testing. Furthermore, epidemiological profiles of S. pneumoniae infections were analyzed.ResultsAmong the strains analyzed, 88% were recognized as invasive pneumococcal strains. According to the Clinical and Laboratory Standards Institute criteria for non-meningitis, the prevalence of penicillin-non-susceptible S. pneumoniae demonstrated a declining trend from 43.6% in 2017 to 17.2% in 2019. However, the rate of penicillin-non-susceptible S. pneumoniae was 85.7% based on the criteria for meningitis. Furthermore, the prevalence of ceftriaxone-non-susceptible S. pneumoniae was 62.7% based on the criteria for meningitis. Isolates demonstrated higher susceptibility toward doripenem and ertapenem than toward meropenem and imipenem. An increased rate of non-susceptibility toward levofloxacin was observed in southern Taiwan (15.1%) and elderly patients (≥65 years; 11.4%). Most isolates were susceptible to vancomycin and linezolid.ConclusionEmpirical treatment with ceftriaxone monotherapy for pneumococcal meningitis should be carefully monitored owing to its high non-susceptibility rate. The susceptibility rates of most isolates to penicillin (used for treating non-meningitis pneumococcal diseases), carbapenems (ertapenem and doripenem), respiratory quinolones (moxifloxacin and levofloxacin), vancomycin, and linezolid suggested the potential of these antibiotics in treating pneumococcal diseases in Taiwan.     

Alterations to penicillin-binding proteins 1A, 2B and 2X amongst penicillin-resistant clinical isolates of Streptococcus pneumoniae serotype 23F from the nasopharyngeal flora of children

Various amino acid substitutions were identified in the three major penicillin-binding proteins (PBP1A, PBP2B and PBP2X) of eight clinical isolates of Streptococcus pneumoniae serotype 23F collected from children. The particular changes related to the level of penicillin resistance. Alterations were detected in an isolate with a penicillin MIC as low as 0.06 mg/L. These results confirm that the level of penicillin resistance in pneumococci reflects with sequential alterations of PBPs in clinical isolates.     

In vivo efficacy of cefotaxime and amoxicillin against penicillin-susceptible, penicillin-resistant and penicillin-cephalosporin-resistant strains of Streptococcus pneumoniae in a mouse pneumonia model

Objective: To compare cefotaxime (CTX) to amoxicillin (AMO) (usually considered the definitive therapy for penicillinsusceptible Streptococcus pneumoniae infections) in an immunocompromised mouse pneumonia model.
Methods: Three S. pneumoniae clinical isolates were used: two serotype 19 strains, a penicillin-susceptible (P^s) strain (penicillin MIC = 0.03 μ/mL) and a highly penicillin-resistant (P^r) strain (penicillin MIC = 4 μ/mL), and one serotype 23F strain, a penicillin-cephalosporin-resistant (CFTR) strain (CTX MIC = 4 μ/mL).
Results: CTX activity in this mouse model of pneumonia induced by the highly penicillin-resistant strain of S. pneumoniae was lower than expected from its low MIC against this organism. Furthermore, AMO had greater efficacy than CTX against a CFTR S. pneumoniae strain.
Conclusion: Our data suggest that there is no major difference in the in vivo efficacy of the two agents, cefotaxime and amoxicillin, against penicillin-resistant and penicillin-cephalosporin-resistant S. pneumoniae.     

Streptococcus agalactiae in a large Portuguese teaching hospital: antimicrobial susceptibility, serotype distribution, and clonal analysis of macrolide-resistant isolates

Group B streptococci are emerging as a cause of serious infection worldwide. The capsular polysaccharides are not only important virulence factors but also the target of vaccine development efforts. Serotypes III (24.6%), V (23.4%), Ia (17.8%), and II (16.3%) were the most prevalent among 252 Streptococcus agalactiae isolates collected during 1999-2002 in the largest hospital of Lisbon, Portugal. The substantial proportion of bacteremic patients (17 neonates and 21 adults) in this period illustrates the present importance of S. agalactiae as a cause of invasive disease. All isolates were fully susceptible to penicillin (MIC(50) = 0.064 microg/ml; MIC(90) = 0.094 microg/ml, range 0.008-0.094), cefotaxime, chloramphenicol, ofloxacin, and vancomycin. Resistance was found to tetracycline (75.4%), erythromycin (10.7%), and clindamycin (9.9%). Of the 27 erythromycin-resistant isolates, 70.4% had the cMLS(B), 22.2% the iMLS(B), and 7.4% the M phenotype. All isolates presenting the M phenotype carried the mef(A) gene, whereas the erm(B) gene was found in a large fraction of MLS(B) isolates (n = 17) and only a small proportion (n = 7) the erm(A) gene [erm(TR) variant]. All isolates carried a single macrolide-resistance determinant. Macrolide resistance was not attributable to a single clone as evidenced by distinct serotype and pulsed-field gel electrophoretic profiles. Careful surveillance of S. agalactiae invasive infections in Portugal is essential, and the treatment or intrapartum prophylaxis of patients who are allergic to penicillin should be guided by contemporary resistance patterns observed in the country.     

Characterization of ermB gene transposition by Tn1545 and Tn917 in macrolide-resistant Streptococcus pneumoniae isolates

In Streptococcus pneumoniae, the ermB gene is carried by transposons, such as Tn917 and Tn1545. This study investigated the relationship between macrolide resistance and the presence of the ermB gene on Tn917 or Tn1545 in 84 Japanese pneumococcal isolates. Macrolide-resistant strains were classified into two groups as follows. Group 1 (19 strains) showed a tendency to high resistance to erythromycin (MIC at which 50% of isolates are inhibited, 4 mg/liter; MIC at which 90% of isolates are inhibited [MIC(90)], 128 mg/liter) but susceptibility to rokitamycin (MIC(90), 1 mg/liter), with the ermB gene located on Tn1545. Group 2 (65 strains) showed a tendency to high resistance to both antibiotics (MIC(90)s for both erythromycin and rokitamycin, >128 mg/liter), with the ermB gene located on Tn917. There were no strains with constitutive macrolide resistance in either group. All of the strains in group 2 had a deletion in the promoter region of ermB and an insertion of the TAAA motif in the leader peptide. The results of pulsed-field gel electrophoresis and serogrouping showed that Tn1545 spread clonally while Tn917 spread both horizontally and clonally. In conclusion, in Japanese macrolide-resistant S. pneumoniae isolates, the ermB gene is carried and spread primarily by Tn917.     

Clonal dissemination of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae isolates in a Korean hospital

In this study, we investigated the molecular characteristics of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae isolates that were recovered from an outbreak in a Korean hospital. A new multilocus sequence typing (MLST) scheme for K. pneumoniae based on five housekeeping genes was developed and was evaluated for 43 ESBL-producing isolates from an outbreak as well as 38 surveillance isolates from Korea and also a reference strain. Overall, a total of 37 sequence types (STs) and six clonal complexes (CCs) were identified among the 82 K. pneumoniae isolates. The result of MLST analysis was concordant with that of pulsedfield gel electrophoresis. Most of the outbreak isolates belonged to a certain clone (ST2), and they produced SHV-1 and CTX-M14 enzymes, which was a different feature from that of the K. pneumoniae isolates from other Korean hospitals (ST20 and SHV-12). We also found a different distribution of CCs between ESBL-producing and -nonproducing K. pneumoniae isolates. The MLST method we developed in this study could provide unambiguous and well-resolved data for the epidemiologic study of K. pneumoniae. The outbreak isolates showed different molecular characteristics from the other K. pneumoniae isolates from other Korean hospitals.     

Molecular epidemiology of macrolide-resistant isolates of Streptococcus pneumoniae collected from blood and respiratory specimens in Norway

Norway has a low prevalence of antimicrobial resistance, including macrolide-resistant Streptococcus pneumoniae (MRSP). In a nationwide surveillance program, a total of 2,200 S. pneumoniae isolates were collected from blood cultures and respiratory tract specimens. Macrolide resistance was detected in 2.7%. M-type macrolide resistance was found in 60% of resistant isolates, and these were mainly mef(A)-positive, serotype-14 invasive isolates. The erm(B)-encoded macrolide-lincosamide-streptogramin B (MLS(B)) type dominated among the noninvasive isolates. One strain had an A2058G mutation in the 23S rRNA gene. Coresistance to other antibiotics was seen in 96% of the MLS(B)-type isolates, whereas 92% of the M-type isolates were susceptible to other commonly used antimicrobial agents. Serotypes 14, 6B, and 19F accounted for 84% of the macrolide-resistant isolates, with serotype 14 alone accounting for 67% of the invasive isolates. A total of 29 different sequence types (STs) were detected by multilocus sequence typing. Twelve STs were previously reported international resistant clones, and 75% of the macrolide-resistant isolates had STs identical or closely related to these clones. Eleven isolates displayed 10 novel STs, and 7/11 of these "Norwegian strains" coexpressed MLS(B) and tetracycline resistance, indicating the presence of Tn1545. The invasive serotype-14 isolates were all classified as ST9 or single-locus variants of this clone. ST9 is a mef-positive M-type clone, commonly known as England(14)-9, reported from several European countries. These observations suggest that the import of major international MRSP clones and the local spread of Tn1545 are the major mechanisms involved in the evolution and dissemination of MRSP in Norway.     

Clonal spread of macrolide-resistant Mycoplasma pneumoniae sequence type-3 and type-17 with recombination on non-P1 adhesin among children in Taiwan

ObjectivesMycoplasma pneumoniae is currently the most commonly detected bacterial cause of childhood community-acquired pneumonia in several countries. Of note, clonal expansion of macrolide-resistant ST3 occurred in Japan and South Korea. An alarming surge in macrolide resistance complicates the treatment of pneumonia. We aimed to evaluate the clinical manifestation and clonal relatedness of M. pneumoniae circulating among children in Taiwan.MethodsWe prospectively enrolled 626 children with radiologically confirmed pneumonia between 2017 and 2019. An M. pneumoniae infection was suspected on clinical grounds, and tested by real-time PCR and oropharyngeal swab cultures. We used multilocus sequence typing and whole-genome sequencing to characterize the genetic features of M. pneumoniae.ResultsA total of 226 children with M. pneumoniae pneumonia were enrolled. Macrolide resistance was found in 77% (174/226) of patients. Multi-locus sequence typing revealed that ST3 (n = 93) and its single-locus variant ST17 (n = 84) were the predominant clones among macrolide-resistant strains. ST17 presented clinical characteristics comparable to its ancestor ST3. On multivariate analysis, macrolide resistance (OR 3.5; 95% CI 1.4–8.5; p 0.007) was independently associated with fever >72 hours after macrolide treatment. By whole-genome sequencing, prediction analysis of recombination sites revealed one recombination site in ST3 and ST17 compared with M29 (a macrolide-sensitive ST3 strain isolated from China in 2005) containing cytadhesin MgpC-like protein, RepMP4 and RepMP5. ST17 had another recombination site containing an adhesin and RepMP2/3.ConclusionsIn addition to macrolide resistance, ST3 and its ST17 variant might evolve through recombination between repetitive sequences and non-P1 cytadhesins for persistent circulation in Taiwan.     

Antimicrobial susceptibility and serotype distribution of Streptococcus pneumoniae and molecular characterization of multidrug-resistant serotype 19F, 6B,and 23F Pneumococci in northern Thailand

Penicillin-resistant Streptococcus pneumoniae is widely spread worldwide. Our study was undertaken to examine the susceptibility and serotypes of S. pneumoniae in northern Thailand. Ninety-three S. pneumoniae strains were isolated from 93 patients at Chiang Mai University Hospital, Chiang Mai, Thailand, from September 1999 to June 2000. The strains were isolated from sputum (n = 51), blood (n = 15), nasopharynges (n = 14), and other sources (e.g., pus, ears, ascites, and cerebrospinal fluid) (n = 13). Of the 93 isolates, 29 (31.2%) were susceptible, 24 (25.8%) showed intermediate resistance (MIC, 0.12 to 1.0 micro g/ml), and 40 (43.0%) were fully resistant (MIC, >/=2.0 micro g/ml) to penicillin G. Seven (46.7%) from blood, 5 (35.7%) from nasopharynges, 15 (29.4%) from sputum, and 2 (15.4%) from other sources were susceptible isolates. Serotyping with the use of antiserum revealed differences in the predominant types that were susceptible (6A, 11A, and 19A), intermediately resistant (6B and 23F), and fully resistant (6B, 19F, and 23F). Molecular typing by pulsed-field gel electrophoresis of multidrug-resistant pneumococci showed four patterns (A, B, C, and D) for 16 isolates of serotype 19F, with pattern B being predominant (12 isolates). This finding was different from that with the Taiwan multidrug-resistant serotype 19F clone. Eleven isolates of serotype 6B all showed pattern E, and nine isolates of serotype 23F showed two patterns (F and G), with pattern F being predominant (seven isolates). This finding was similar to that with the Spanish multidrug-resistant serotype 23F clone. Our results indicated that the resistance of pneumococci to antibiotics in northern Thailand is progressing rapidly and that effort should be intensified to prevent any spread of pandemic multidrug-resistant serotypes 19F, 6B, and 23F.     

Antimicrobial susceptibilities and serotype distribution of Streptococcus pneumoniae isolates from a Low socioeconomic area in Lima,Peru

Streptococcus pneumoniae isolates were obtained from nasopharyngeal swabs taken from children living in a low socioeconomic area of Lima, Peru, to determine the rates of antimicrobial resistance and serotype distribution. A total of 146 nasopharyngeal isolates were collected from children from 3 to 38 months of age. Twenty-one clinical laboratory isolates from both sterile and nonsterile sites were obtained from a local hospital. Isolates with reduced susceptibilities to penicillin represented 15.1 and 42.9% of the nasopharyngeal and clinical isolates, respectively. For neither group of isolates did penicillin MICs exceed 1.5 micro g/ml, indicating only intermediate resistance. Thirty-two different serotypes were identified from the 146 nasopharyngeal isolates. The serotypes of the clinical isolates were represented among those 32 types. Isolates with reduced susceptibility to multiple antimicrobial agents were present in both settings. These findings indicate some of the highest rates of antimicrobial resistance in the region as well as a slightly different serotype distribution pattern from those of other South American countries. The 7-valent conjugate pneumococcal vaccines would only have a limited effect, providing coverage for about half of all isolates. Increasing rates of resistance in Peru necessitate an awareness of antimicrobial treatment practices and vaccination strategies.     

Whole-genome sequencing of Egyptian multidrug-resistant Klebsiella pneumoniae isolates: a multi-center pilot study

European Journal of Clinical Microbiology & Infectious Diseases - Multidrug-resistant (MDR) Klebsiella pneumoniae is a common infectious pathogen. We performed whole-genome sequencing (WGS) of...     

Dissemination of macrolide-resistant Streptococcus pneumoniae isolates containing both erm(B) and mef(A) in South Korea

Macrolide resistance was detected in 64 of 77 (83.1%) Streptococcus pneumoniae isolates from South Korea. Seven (10.9%) isolates contained only mef(A), 32 (50%) contained only erm(B), and 25 (39.1%) contained mef(A) and erm(B). Nineteen isolates containing mef(A) and erm(B) belonged to serotype 19F, and seven isolates were identical to the Taiwan(19F)-14 clone.