Bactericidal activities of parenteral antibiotics and genotype of penicillin-binding protein in Streptococcus pneumoniae and Haemophilus influenzae isolated from children's blood

[Susceptibility in parenteral antibiotics in Streptococcus pneumoniae isolated from children with invasive pneumococcal disease]

Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of commonly used clinical antimicrobial drugs were examined for 76 strains of Streptococcus pneumoniae isolated between 2006 and 2011 from pediatric patients with invasive pneumococcal infection. Patients from whom bacterial strains were isolated ranged from 4 months to 6 years old and included 50 infants (65.8%) 1 year old and 10 (13.2%) less than 1 year old, i.e., 79.1% of all patients studied. In diagnosis, 38 (50.0%) had occult bacteremia, 34 (44.7%) pneumonia, 3 (3.9%) meningitis, and 1 (1.3%) sepsis. Infections in all but one case who died of sepsis were treated without sequelae. The most frequent capsular serotype among isolates was 6B (20 strains, 26.3%), followed by 19 F (13 strains, 17.1%) and 14 (9 strains, 11.8%). Serotypes for 55 strains (72.4%) corresponded to those contained in heptavalent pneumococcal conjugate vaccine. In classification by resistance based on mutations in penicillin-binding protein genes, 32 were penicillin-resistant S. pneumoniae (42.1%), 35 penicillin intermediate-resistant S. pneumoniae (46.1%), and 11 penicillin-susceptible S. pneumoniae (11.8%). MIC90/MBC90 of drugs were as follows: ampicillin 4/4 microg/mL, cefotaxime 0.5/0.5 microg/mL, ceftriaxone 1/2 microg/ mL, panipenem 0.125/0.125 microg/mL, meropenem 0.5/0.5 microg/mL, and doripenem 0.25/0.25 microg/mL.

[Antibiotic susceptibility to parental antibiotics and penicillin-binding-protein genotype in Haemophilus influenzae isolated from children with invasive infection]

The minimum inhibitory concentation (MIC) and minimum bactericidal concentration (MBC) of 8 parental antibiotics were determined using 21 strains of Haemophilus influenzae from 21 children with invasive H. influenzae infection in 2006-2009. Children were from 4 months to 12 years, with 18 (85.7%) under 1 year old. Diagnosies involved meningitis or pneumonia in 7 (33.3%); epiglottitis, phlegmon, or arthritis in 2 each (9.5%), and occult bacteremia in 1 (4.8%). The capsule type was b (Hib) in 19 (90.5%). Classified by penicillin binding protein (PBP) gene mutation, strains were classified into (i) 6 beta-lactamase negative ampicillin resistant (BLNAR) (28.6%), (ii) 5 low-BLNAR (23.8%), (iii) 4 beta-lactamase positive clavulanic acid/amoxicillin resistant-II (19.0%), (iv) 2 beta-lactamase positive ampicillin resistant (9.5%), and (v) 4 beta-lactamase negative ampicillin susceptible (19.0%). Compared to a 2003-2005 survey, the number of sensitive strains had decreased significantly (p < 0.05). MIC90/MBC90 of ampicillin was 64/>128 microg/mL, piperacillin 16/>128 microg/mL, cefotaxime 0.5/0.5 microg/mL, ceftriaxone 0.12/0.12 microg/mL, panipenem 0.5/0.5 microg/mL, meropenem 0.12/0.12 microg/mL, doripenem 0.25/0.25 microg/ml, and chloramphenicil 1/2 microg/mL against H. influenza.

Meta-analysis of antibiotic susceptibility and the genotype of penicillin-binding proteins in Streptococcus pneumoniae

To further understanding of the mechanisms of development of resistance to penicillin in Streptococcus pneumoniae, and the role of penicillin-binding proteins (PBPs) mutations to antibiotics resistance a meta-analysis was performed. Major databases, Pubmed, Current Contents, Biosis previews, Web of Science, were searched for studies that published within 1997 through to 2007, and reported the penicillin MIC and the alteration of PBP 1a, 2b and 2x (genes or proteins) of clinical S. pneumoniae isolates. Papers were reviewed by 2 persons and used standard criteria to enroll them. Meta-analysis was performed using a random-effects model. Overall, 20 studies were included in the meta-analysis. For the included 1771 clinical S. pneumoniae isolates, the susceptibility to penicillin decreased in inverse proportion to the presence of mutated pbp genes. The mutations of the conserved amino acid motifs STMK and SRNVP of PBP 1A, STMK and LKSG of PBP2X, and SSNT of PBP2B are critical for the penicillin resistance. Those motifs can be used as markers for the penicillin susceptibility of S. pneumoniae. These results are useful in helping define the mechanism of penicillin resistance in S. pneumoniae.