We investigated the susceptibility to antibacterials, genotype of penicillin-binding protein (PBP) genes and macrolide resistant genes, and the serotypes against 377 strains of Streptococcus pneumoniae isolated from medical facilities in Gifu and Aichi prefectures between June 2008 and April 2009. These results were compared with those against 160 strains of S. pneumoniae isolated in 2004.

Referring to CLSI (M100-S17), the overall incidence of penicillin-susceptible (PSSP), penicillin-intermediate (PISP) and penicillin-resistant (PRSP)S. pneumoniae was 143(38%), 185(49%) and 49(13%) strains, respectively. PISP and PRSP were isolated higher in the material of nasal cavity and throat, and PRSP was isolated higher in the area of Chuno district.

The number of gPSSP with 3 normal PBP genes, gPISP with 1 or 2 normal PBP genes and gPRSP with 3 abnormal genes was 23(6.1%), 173(46%) and 181(48%) strains, respectively. The isolates with no macrolide-resistant gene, only mefA, only ermB, and both mefA and ermB were 28(7.4%), 138(37%), 166(44%) and 45(12%). The prevalent pneumococcal serotypes were type 19(92 strains; 24%), following by type 23(60 strains; 16%) and type 6(56 strains; 15%). The 80% of pneumococcal serotypes of PRSP were serotype 19 and 6.

The MIC₉₀ of each antibacterial was as follows; 0.1μg/mL for imipenem, panipenem and garenoxacin, 0.2μg/mL for moxifloxacin, 0.39μg/mL for meropenem and tosufloxacin, 0.78μg/ mL for amoxicillin, clavulanic acid/ amoxicillin, cefditoren and cefcapene, 1.56μg/mL for benzylpenicillin, piperacillin, cefteram and levofloxacin, 3.13μg/mL for cefotiam, flomoxef and pazufloxacin, 6.25μg/mL for cefdinir, 12.5μg/mL for norfloxacin and minocycline, >100μg/mL for clarithromycin, and these MIC₉₀s were about the same as those in 2004.

We investigated the susceptibility to antibacterial agents of 334 strains of Pseudomonas aeruginosa isolated from medical facilities in Gifu and Aichi prefectures from May to September 2008. For the β-lactams, meropenem (MEPM) and doripenem (DRPM) gave the lowest MIC₅₀ at 0.5μg/mL, and tazobactam/piperacillin (TAZ/PIPC) gave the highest susceptible rate of the breakpoint by Clinical and Laboratory Standards Institute (CLSI) at 93.1%. For the quinolones, ciprofloxacin (CPFX) gave the lowest MIC₅₀ at 0.25μg/mL, followed by pazufloxacin (PZFX) at 0.5μg/mL, and levofloxacin (LVFX) at 1μg/mL, and susceptible rate was 76.0% for CPFX and 73.4% for LVFX. Susceptible rates to amikacin (AMK) and tobramycin (TOB) of aminoglycocides and colistin (CL) of polypeptides were 98.2%, 97.6% and 96.4%. In 334 strains, IMP-1 MBL producing P. aeruginosa was 1 strain, and the strain showed resistance to all antibacterial agents except AMK and CL used in this study. The strains isolated from urine were lower susceptible rate in comparison with those from sputum, notably the susceptible rate to CPFX from urine was less over 30% than those from sputum. Because the results of the susceptibility test against P. aeruginosa were different in each area, it is important for us to pay attention to the susceptibility to antibacterial agents and the emergence of resistance in the clinical strains through continuous susceptibility surveillance.

High pathogenicity and drug resistance of Streptococcus pneumoniae are serious problem in clinical practice. Since 1999, we have conducted epidemiologic analyses of S. pneumoniae in Chubu district. We report the results of the analysis conducted in 2009.

Three hundred and eight (308)S. pneumoniae isolates with a gene coding for autolysin lyt- A, which had been isolated from patients at 21 medical institutions in Gifu prefecture and the northern part of Aichi prefecture in 2009, were enrolled in this study. The strains were classified according to their drug resistance based on the presence of the pbp mutation, and examined for the presence of the two macrolide-resistance genes, ermB and mefA. Moreover, they were serotyped using type-specific antisera.

The mean age of the patients from whom these S. pneumoniae strains were isolated, was 23.4±30.1 years old, and children aged 15 years old or less accounted for 66% of all the patients. Genotype penicillin-susceptible S. pneumoniae (gPSSP), genotype penicillin-intermediate S. pneumoniae (gPISP) and genotype penicillin-resistant S. pneumoniae (gPRSP) were 22(7.1%), 131(42.5%) and 155(50.3%), respectively. The strains with mefA positive and ermB negative, mefA negative and ermB positive, and mefA positive and ermB positive were 80(26.0%), 153(49.7%), and 47(15.3%), respectively. The MIC₉₀ values of tebipenem (TBPM) and faropenem were 0.06 μg/mL and 0.5 μg/mL, respectively. TBPM showed the high bactericidal activity against gPRSP. In carbapenems, panipenem and biapenem exhibited higher bactericidal activities. Quinolone-resistant S. pneumoniae (QRSP) were isolated from 10(3.2%). QRSP dominated 5(7.9%) and 3(1.5%) among the elderly (over 65 years old) and children, respectively.(As for the serotype, serotypes 6, 19 and 23 were 60(19.5%), 62(20.1%), and 44(14.3%), respectively.

Further epidemiologic studies on S. pneumoniae might be required also in the future, including the relationship between the serotype and drug resistance.

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≤2 μg/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≤1 ȝg/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 μg/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 μg/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.

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 β-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 μg/mL and doripenem showed an MIC₉₀ of 4 μg/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.