[Antimicrobial susceptibilityof clinical isolates of aerobic gram-negative bacteria in 2008].

We determined MICs of antibacterial agents against 1145 clinical strains of aerobic Gram-negative bacteria (22 species) isolated at 16 Japanese facilities in 2008. MICs were determined using mostly broth microdilution method and antibacterial activity was assessed. Strains producing extended-spectrum beta-lactamases (ESBL) accounted for 3.8% of Escherichia coli, 2.6% of Klebsiella pneumoniae, 6.8% of Klebsiella oxytoca, 5.5% of Proteus mirabilis and 1.8% of Proteus vulgaris. ESBL produced strains were 6.8% at K. oxytoca that increased compared with 3.2% and 5.5% at P. mirabilis that decreased compared with 18.8% in 2006. Among Haemophilus influenzae, 61.7% that decreased compared with 67.7% in 2006, equaled 58.7% in 2004, were strains when classified by penicillin-binding protein 3 mutation. Against Pseudomonas aeruginosa, the activity of most antibacterial agents was similar to that in 2006. Although two antibacterial agents that tobramycin showed an MIC90 of 1 microg/mL and doripenem showed an MIC90 of 4 microg/mL against P. aeruginosa have potent activity. Of all P. aeruginosa strains, 4.3% were resistant to six agents of nine antipseudomonal agents, that decreased compared to 12.2% in 2004 and 5.7% in 2006. Against other glucose-non-fermentative Gram-negative rods, the activity of most antibacterial agents was similar to that in 2006.

[Antimicrobial susceptibility of clinical isolates of aerobic gram-positive cocci and anaerobic bacteria in 2008].

The activity of antibacterial agents against aerobic Gram-positive cocci (25 genus or species, 1029 strains) and anaerobic bacteria (21 genus or species, 187 strains) isolated from clinical specimens in 2008 at 16 clinical facilities in Japan were studied using either broth microdilution or agar dilution method. The ratio of methicillin-resistant strains among Staphylococcus aureus and Staphylococcus epidermidis was 59.6% and 81.2%, suggesting that resistant strains were isolated at high frequency. Vancomycin (VCM), linezolid (LZD) and quinupristin/dalfopristin (QPR/DPR) had good antibacterial activity against methicillin-resistant S. aureus and methicillin-resistant S. epidermidis, with MIC90s of < or = 2 microg/mL. The ratio of penicillin (PC) intermediate and resistant strains classified by mutations of PC-binding proteins among Streptococcus pneumoniae was 92.0% that was highest among our previous reports. Cefpirome, carbapenems, VCM, teicoplanin (TEIC), LZD and QPR/DPR had MIC90s of < or = 1 microg/mL against PC-intermediate and resistant S. pneumoniae strains. Against all strains of Enterococcus faecalis and Enterococcus faecium, the MICs of VCM and TEIC were under 2 microg/mL, and no resistant strain was detected, suggesting that these agents had excellent activities against these species. 15.9% of E. faecalis strains and 1.2% of E. faecium strains showed intermediate to LZD. 17.1% of E. faecium strains showed intermediate or resistant to QPR/DPR. Against all strains of Clostridium difficile, the MIC of VCM was under 1 microg/mL, suggesting that VCM had excellent activity. Carbapenems showed good activity against Clostridiales, Bacteroides spp., and Prevotella spp., but one strain of Bacteroides fragilis showed resistant to carbapenems. And so, the susceptibility of this species should be well-focused in the future at detecting continuously.

[Immunological analysis of pseudo-positive reaction in healthy adults at anti-streptolysin O measurement by latex agglutination method].

Streptolysin O (SLO) is a toxic immunogenic protein produced by Streptococcus pyogenes (S. pyogenes). The latex agglutination photometric immunoassay with latex coated by SLO (latex agglutination method) has been most widely used for determination of antibody to SLO (ASO). We measured ASO levels by latex agglutination method in serum specimens collected from 159 healthy individuals and eight patients with S. pyogenes, who had a positive S. pyogenes culture from throat swabs. A significant frequency(about 15%) had positive ASO levels (> 200 unit/ml) in healthy individuals aged < 20 (47 individuals) and 20-29 (80 individuals), respectively, however, none of 30 or over (32 individuals) were positive. The SLO specimen purchased from Sigma Chemical Co. showed at least three protein bands on SDS-PAGE; one was considered SLO protein because it had a molecular weight of 64 kD and of the remaining proteins, one had a molecular weight higher and the other had a molecular weight lower than 64 kD. Serum antibodies among the healthy adults to Sigma-SLO specimen consisted of IgG class in the majority, with little IgM class. Immunoblotting analysis revealed that serum antibodies of the patients recognized the 64-kD protein (SLO), and serum antibodies of the healthy adults recognized different proteins from SLO. It appeared that many of the healthy adults with a positive ASO level had antibodies different from ASO, resulting in pseudo-positive ASO values when ASO was measured by latex agglutination method using SLO specimen containing non-specific proteins. Improvement of commercial kits using this method is required.

The indirect pathogenicity of Stenotrophomonas maltophilia.

Stenotrophomonas maltophilia has at least two inducible beta-lactamases, L1 and L2, which can hydrolyze almost all classes of beta-lactam antimicrobial agents. This study was done to verify the indirect pathogenicity of S. maltophilia that could promote the growth of other beta-lactam agent-susceptible bacteria in a mixed culture. We counted CFU of beta-lactam agent-susceptible bacteria under the presence of imipenem or ceftazidime in a pure culture and mixed culture with S. maltophilia. Our results showed that beta-lactamase leaking from S. maltophilia can encourage the growth of Serratia marcescens and Pseudomonas aeruginosa even if imipenem or ceftazidime was supplemented. This study discovered a blind spot in chemotherapy against an indirect pathogen such as S. maltophilia.

First Streptococcus agalactiae isolates highly resistant to quinolones, with point mutations in gyrA and parC.

Three isolates of Streptococcus agalactiae highly resistant to multiple fluoroquinolones were isolated in Japan. Compared with susceptible strains of S. agalactiae, these quinolone-resistant strains had double point mutations within the quinolone resistance-determining regions of gyrA and parC; Ser-81 was changed to Leu (TCA --> TTA) in the amino acid sequence deduced from gyrA, and Ser-79 was changed to Phe (TCC --> TTC) in the amino acid sequence deduced from parC. Comparative sequence analysis revealed the possibility of gene transfer between S. agalactiae and another beta-hemolytic streptococcus, Streptococcus difficile.

[The results of antibiotic susceptibility of gram-negative rods at Tottori University Hospital--the possibility of the sensible use of narrow-spectrum antimicrobial agents].

The control of hospital-acquired infections is a matter of social concern, especially in the proper use of antimicrobial agents. The fundamentals of treatment for infectious diseases involve the exact identification of the responsible bacteria, and the minimum essential use of narrow-spectrum antimicrobial agents for the identified bacteria. We tested the antimicrobial susceptibility of 13 species which belong to the gram-negative rod type and isolated 50 or more strains at Tottori University Hospital in 2001. We evaluated the susceptibility pattern for every species, and have proposed a plan for the sensible use of narrow-spectrum antimicrobial agents. The resistant frequency in the present study was equal to or lower than previously reported. We think that it is possible to use narrow-spectrum antimicrobial agents more often, because the susceptible frequency to these agents was fairly high for some species. It is not too much to say that the history of the development of antimicrobial agents has been a road to broad-spectrum. Though the proper use of antimicrobial agents seems to go against this view, we should remain farsighted. Not only is the publicity of proper use indispensable but excellent surveillance is also highly necessary. We hope for the establishment of a good surveillance system gifted with simplicity, universality, high reproduction and continuity.

[Beta-lactamase activity and susceptibilities to antibiotics among some species of bacteria isolated from medical institution between December 1999 and February 2000].

We studied the beta-lactamase activity and susceptibilities to antibiotics in 604 strains among 10 species of bacteria isolated from 10 medical institutions in Tottori and Shimane Prefectures between December 1999 and February 2000. beta-Lactamase activity was measured by the nitrocefin test and penicillinase/cephalosporinase activities were measured by acidometry. beta-Lactamase activity was detected in 72.1% of S. aureus, 18.8% of H. influenzae, and 96.3% of M. catarrhalis. Penicillinase/cephalosporinase activities were detected in 17.8%/22.2% of E. coli, 9.7%/0.0% of K. pneumoniae, 18.6%/95.3% of E. cloacae, 12.7%/79.4% of S. marcescens, and 7.1%/31.8% of P. aeruginosa. Three of 72 strains (4.2%) of K. pneumoniae and 5 of 90 strains (5.6%) of E. coli were assessed as ESBL-producing bacteria using the NCCLS proposed screening method based on routine susceptibility testing results. BLNAR were detected in 13 of 69 strains (18.8%) of H. influenzae.