PBP3 Mutations Research Articles

成人呼吸器感染症患者から分離されたインフルエンザ菌の薬剤耐性と耐性遺伝子変異の経年的検討

Haemophilus influenzae, a major respiratory tract pathogen, is becoming increasingly resistant to beta-lactam antibiotics. Studying annual trends in antibiotic susceptibility and genetic patterns of H. influenzae beta-lactam resistance, we isolated 122 strains from the adult respiratory tract in 2007, determined MIC for different antibiotics, and analyzed TEM-1 beta-lactamase resistant genes and ftsI encoding PBP3 mutation compared to results in 2005 and 2007. We found that ABPC-susceptible strains with MIC <1 microg/mL (BLNAS) accounted for 71.0%, ABPC-resistant strains with MIC exceeding 2 microg/mL without beta-lactamase activity (BLNAR) for 25.3%, and beta-lactamase-positive strains (BLP) for 3.7%. The BLNAS ratio showed no significant change from 2002 and 2005. The BLP ratio decreased from those in 2002 and 2005. Genetic studies of resistant genes showed that gBLNAS with no resistant genes had increased in the last five years. The ratio of all strains with PBP3 mutation (gBLNAR and gLow-BLNAR) remained constant from 2002 to 2007. The proportion of gBLNAR with two PBP3 mutations had increased, however, while gLow-BLNAR with one mutation had decreased. LVFX showed constant strong antimicrobial potency for all mutation groups. Among beta-lactam antibiotics, the lowest MIC90 was observed in parenteral CTRX and oral CDTR-PI use. Although a new MIC peak generated by gBLNAR became obvious in the ABPC and CDTR-PI MIC distribution, the MIC of the new peak was still low enough to treat with high doses of those two antibiotics.

Recovery of susceptibility to penicillin G in clinical isolates of Streptococcus pneumoniae despite increased accumulation of pbp gene alterations

Two hundred consecutive clinical isolates of Streptococcus pneumoniae isolated in 2005 and 2006 were analysed for susceptibility to various antimicrobials, pbp gene alterations and macrolide resistance gene expression (2007 analysis) and the results were compared with previous data (2003 analysis). The average minimum inhibitory concentration (MIC) of penicillin G in isolates with 1a m /2x m /2b m decreased from 1.135 ± 0.503 mg/L in the 2003 analysis to 0.872 ± 0.540 mg/L in the 2007 analysis ( P = 0.0046). The prevalence of isolates with 1a m /2x m /2b m increased from 30.5% to 32.3%, but the difference was not statistically significant ( P = 0.6979). The prevalence of isolates with a clarithromycin MIC ≥ 1.0 mg/L increased from 65.9% to 80.0% ( P = 0.0005). Isolates expressing ermB increased from 46.6% to 62.6% ( P = 0.0004). We conclude that the decrease in penicillin resistance of S. pneumoniae does not correlate with a decrease in pbp mutations; on the contrary, the prevalence of isolates with pbp mutations increased. A decrease in penicillin resistance in S. pneumoniae with pbp mutations appears to explain the present results regarding the recovery of penicillin susceptibility. Our results suggest that the spread of mutated pbp genes among S. pneumoniae itself is not responsible for acquisition of the penicillin-resistant phenotype. Use of β-lactams, especially oral cephalosporins, appears to be responsible for the acquisition of penicillin resistance.

Mutations in penicillin-binding proteins 1, 2 and 3 are responsible for amoxicillin resistance in Helicobacter pylori

To elucidate the relationship between the mutations of penicillin-binding protein (PBP)1, PBP2 and PBP3 and amoxicillin resistance in Helicobacter pylori. The mutations detected only in clinical amoxicillin-resistant strains were determined by comparison of the deduced amino acid sequences of PBP1(HP0597), PBP2(HP1556) and PBP3(HP1565) encoded by the pbp1, ftsI and pbp2 genes, respectively, in 13 clinical H. pylori strains and three ATCC strains. The contribution of the mutations in PBPs was analysed by the natural transformation of the amoxicillin-susceptible strain ATCC 700392 with various combinations of the pbp1, ftsI and pbp2 genes from the amoxicillin-resistant strain TH743 (MIC of amoxicillin: 8 mg/L). We initially identified six, four and two mutations of PBP1, PBP2 and PBP3, respectively, which were detected only in amoxicillin-resistant strains. By the natural transformation of an amoxicillin-susceptible strain ATCC 700392, we found that mutations in PBP1 and PBP3 conferred higher resistance to amoxicillin than mutations in PBP1 and PBP2, or mutations only in PBP1. Furthermore, mutations in PBP1, PBP2 and PBP3 conferred a 256-fold higher amoxicillin resistance when compared with ATCC 700392. Multiple mutations in PBP2 and PBP3, in addition to mutations in PBP1, confer higher amoxicillin resistance in H. pylori.

Mechanisms, molecular and sero-epidemiology of antimicrobial resistance in bacterial respiratory pathogens isolated from Japanese children

BackgroundThe clinical management of community-acquired respiratory tract infections (RTIs) is complicated by the increasing worldwide prevalence of antibacterial resistance, in particular, β-lactam and macrolide resistance, among the most common causative bacterial pathogens. This study aimed to determine the mechanisms and molecular- and sero-epidemiology of antibacterial resistance among the key paediatric respiratory pathogens in Japan.MethodsIsolates were collected at 18 centres in Japan during 2002 and 2003 from children with RTIs as part of the PROTEKT surveillance programme. A proportion of Haemophilus influenzae isolates was subjected to sequencing analysis of the ftsI gene; phylogenetic relatedness was assessed using multilocus sequence typing. Streptococcus pneumoniae isolates were screened for macrolide-resistance genotype by polymerase chain reaction and serotyped using the capsular swelling method. Susceptibility of isolates to selected antibacterials was performed using CLSI methodology.Results and DiscussionOf the 557 H. influenzae isolates collected, 30 (5.4%) were β-lactamase-positive [BL+], 115 (20.6%) were BL-nonproducing ampicillin-resistant (BLNAR; MIC ≥ 4 mg/L) and 79 (14.2%) were BL-nonproducing ampicillin-intermediate (BLNAI; MIC 2 mg/L). Dabernat Group III penicillin binding protein 3 (PBP3) amino acid substitutions in the ftsI gene were closely correlated with BLNAR status but phylogenetic analysis indicated marked clonal diversity. PBP mutations were also found among BL+ and BL-nonproducing ampicillin-sensitive isolates. Of the antibacterials tested, azithromycin and telithromycin were the most active against H. influenzae (100% and 99.3% susceptibility, respectively). A large proportion (75.2%) of the 468 S. pneumoniae isolates exhibited macrolide resistance (erythromycin MIC ≥ 1 mg/L); erm(B) was the most common macrolide resistance genotype (58.8%), followed by mef(A) (37.2%). The most common pneumococcal serotypes were 6B (19.7%), 19F (13.7%), 23F (13.5%) and 6A (12.8%). Telithromycin and amoxicillin-clavulanate were the most active antibacterials against S. pneumoniae (99.8% and 99.6% susceptibility, respectively).ConclusionApproximately one-third of H. influenzae isolates from paediatric patients in Japan are BLNAI/BLNAR, mainly as a result of clonally diverse PBP3 mutations. Together with the continued high prevalence of pneumococcal macrolide resistance, these results may have implications for the clinical management of paediatric RTIs in Japan.

Resistance to antimicrobiotics and mutation of PBPs in Streptococcus pneumoniae isolated from Kinki region of Japan

We studied the susceptibility to penicillin G (PCG) and other antimicrobiotics in 235 clinical isolates of Streptococcus pneumoniae. Samples were collected between April 1 and June 30, 2000 from nine medical institutions of the Kinki Region of Japan. We classified the minimum inhibitory concentration (MIC) of PCG according to the National Committee for Clinical Laboratory Standards (NCCLS) criteria. The overall rate of all types of S. pneumoniae resistance was 53.2% (penicillin-susceptible S. pneumoniae (PSSP): 46.8%, penicillin-intermediate S. pneumoniae (PISP): 42.6%, penicillin-resistant S. pneumoniae (PRSP): 10.6%). In other antimicrobiotics, the resistance (R)/intermediate susceptibility (I) rates (R/I%) were as follows: ceftriaxone, 28.9%; cefotaxime, 7.7%; imipenem, 8.9%; meropenem, 9.8%; clarithromycin, 82.6%; clindamycin, 42.1%; levofloxacin, 0.4%; vancomycin, 0%. We used the polymerase chain reaction to study the mutations of the penicillin-binding proteins pbp1 a, pbp2b, and pbp2x in 140 strains of S. pneumoniae in the MIC for PCG was < 0.5 microgram/ml. Among the 109 strains of PSSP, 32 (29.4%) had no mutation and 77 (70.6%) showed mutation of more than one of the pbp mutations. Among the 31 strains of PISP, only 1 strain (3.2%) was not mutated. Since 70.6% of the strains classified as PSSP had pbp mutations, S. pneumoniae clearly can acquire resistance to anti-microbiotics. In the future, a comprehensive surveillance of S. pneumoniae is necessary.

Clinical and laboratory evaluation of penicillin resistant Streptococcus pneumoniae in relation to the mutations of pbp 1a, pbp2b and pbp2x.

A total of 210 isolates of Streptococcus pneumoniae (S. pneumoniae) were selected randomly to examine drug susceptibility which were obtained from out- and in-patients who visited Kurume University Hospital and other affiliated hospitals through May 1998 to September 1999. The prevalence of penicillin resistant S. pneumoniae in this study was 39.5% and was compatible with those of previous reports in Japan. From the clinical aspects, the resistant strains of S. pneumoniae have been shown not to be so highly virulent comparing with sensitive strains that only few severe or mortal cases had been reported. Carbapenems, glycopeptides, and fluoroquinolones were shown to be highly active against penicillin-resistant S. pneumoniae strains as evidenced by the low minimum inhibitory concentrations (MICs) though LVFX showed 4 micrograms/ml or higher MICs against some strains. Regarding to the mechanisms of penicillin resistance, penicillin binding proteins coding gene (pbp1a, pbp2x and pbp2b) mutations that cause modifications in these proteins were also examined for all isolates. The multivariate analysis showed statistically significant correlation between higher MIC of penicillin and cephem and pbp1a mutation while no significant contribution of pbp2x and pbp2b to the resistance was demonstrated. Additionally, no significant correlation between pbp mutation and MIC of carbapenem was observed. Furthermore, there were two highly penicillin resistant S. pneumoniae strains with no pbp mutations. Thus the pbp mutations alone were not responsible for the elevation of MIC all beta-lactams. Nevertheless the pbp mutations were detected in advance of actual MIC elevations by inducement experiment in vitro. It indicated that penicillin resistance might be detected earlier than conventional methods. In previous reports some other responsible genes for penicillin resistance were demonstrated. Therefore, it might be possible to presume exact values of MICs of beta-lactams against resistant strains of S. pneumoniae by detecting still unknown genes other than pbps.