Comparison of exhaust emissions resulting from cold- and hot-start motorcycle driving modes.

This study investigated the emissions of criteria air pollutants (carbon monoxide [CO], hydrocarbons [HCs], and oxides of nitrogen [NOx]) from motorcycle exhaust at cold- and hot-start driving cycles on a chassis dynamometer. Seven four-stroke carburetors and two fuel-injection motorcycles were tested. As expected, the emission factors (g/km) of CO and HCs increased during cold-start driving. The ratio of emission factors (g/km) for cold- and hot-start driving cycles ranged from 1.1-1.5 (for CO) to 1.2-2.8 (for HCs). However, the difference of NOx emissions between the cold- and hot-start cycles was not pronounced. Further, the cold-/hot-start ratios of CO and HCs from 50-cm3 motorcycles were higher than those of 100- and 125-cm3 motorcycles; however, the carbon dioxide (CO2) emission was the lowest for the four-stroke motorcycles. High engine temperature and poor combustion efficiency of smaller cylinder-capacity motorcycles may contribute a significant amount of exhaust emission. Additionally, the fuel-base emission factor (g/L-fuel) ratios were low compared with the distance-base emission factor (g/km) in cold- and hot-start driving. This indicates that the effect of catalyst efficiency was greater than the effect of fuel combustion in the tested motorcycles. A comparison of emission ratios of motorcycles and passenger cars shows that the warm-up may be more important for cars, especially under low-temperature conditions. However, the motorcycle contributes a large proportion of CO and HC emissions in many Asian counties. The difference between cold- and hot-start emissions may affect inventory

[Resistance study of community respiratory pathogens isolated in China from 2005 to 2007].

OBJECTIVE: To investigate the antimicrobial resistance of community respiratory pathogens isolated in China. METHODS: The strains of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, S. pyogenes were isolated from patients with community-acquired respiratory tract infections at 14 Chinese hospitals from 2005 to 2007. Etest and disk diffusion methods were used to survey the susceptibility of 14 antibiotics against these strains. These antibiotics included penicillin G, ampicillin, amoxicillin/clavulanic acid, cefaclor, cefprozil, ceftriaxone, cefepime, levofloxacin, gatifloxacin, ciprofloxacin, tetracycline, clindamycin, erythromycin and trimethoprim/sulfamethoxazole (SXT). RESULTS: A total of 1870 strains were collected including S. pneumoniae (n = 997), S. pyogenes (n = 176), H. influenzae (n = 499) and M. catarrhalis (n = 198). The 2005 - 2007 prevalence of penicillin-susceptible S. pneumoniae (PSSP) were 92.6%, 73.9%, 74.1% and penicillin-intermediate S. pneumoniae (PISP) 4.5%, 9.5%, 14.3% and penicillin-resistant S. pneumoniae (PRSP) 2.9%, 16.6%, 11.6% respectively. 36.9% of S. pneumoniae strains isolated from or= 92.9%. CONCLUSIONS: Antimicrobial resistance in S. pneumoniae is rising. The prevalence of PNSSP isolated from children < or = 6 years old is higher than other age groups. Amoxicillin-clavulanic acid, ceftriaxone, cefepime, gatifloxacin and levofloxacin remain highly active against common community respiratory pathogens.

[Surveillance of antimicrobial resistance among nosocomial gram-negative pathogens from 15 teaching hospitals in China in 2005].

OBJECTIVE: To investigate the antimicrobial resistance among the nosocomial gram-negative pathogens from 15 teaching hospitals located in different areas in China in 2005. METHODS: A total of 1927 non-repetitive nosocomial gram-negative pathogens were collected from 15 teaching hospitals in different areas in China and sent to the central lab for reidentification and susceptibility testing. The levels of minimal inhibitory concentration (MIC) of 18 antimicrobial agents were determined by agar dilution method. WHONET 5.4 software was used to analyze the data. RESULTS: The strains of Escherichia coli, Klebsiella pneumoniae, and Proteous mirabilis isolates that did not produce extended spectrum beta lactamases (ESBLs) showed high sensitivity to beta-lactams. The antibiotics with a susceptibility rates over 80% against the strains of Entorobacter cloacae, Enterobacter aerogene, Citrobacter spp, Serratia spp, and Proteous vulgaris producing AmpC enzyme included meropenem, imipenem, and piperacillin-tazobactam, and these 3 drugs showed a susceptibility rate of more than 80% against the ESBL-producing strains of Escherichia coli and Klebsiella pneumoniae. Other antimicrobial agents showing a relatively high activity against Enterobacter spp, Citrobacter spp, Serratia spp and Proteous vulgaris included cefepime (67.3% - 100%), amikacin (67.3% - 95.2%), ceftazidime (52.9% - 100%) and cefoperazone-sulbactam (51.9% - 100%). The susceptibility rate of fluoroquinolones was 34.8% - 36.1% against non-ESBL-producing Escherichia coli and was 13.4% - 17.1% against ESBL-producing isolates. The most active agent against Pseudomonas aeruginosa was polymyxin B (95.6%). The agents with the activity rates of 70% - 80% included meropenem, imipenem, amikacin, and piperacillin-tazobactam. The antibiotic with a high susceptible rate against Acinetobacter baumannii was polymyxin B (98.3%), followed by imipenem (80.8%), meropenem (76.2%), and minocycline (67.4%). The susceptible rates of other agents were all below 60%. The agents with relatively high activity against Stenotrophomonas maltophilia included minocycline (85%), levofloxacin (82.5%), and trimethoprim-sulfamethoxazole (77.5%). The agents with a relatively high activity against Burkholderia cepacia included minocycline (77.2%) and meropenem (61.4%). CONCLUSION: Carbapenem, piperacillin-tazobactam, amikacin and cefepime remained relatively high activity against nosocomial Enterobacteriaceae, Non-fermenting pathogens have lower susceptibility to the antimicrobial agents than before.

[Genotype of TEM- and SHV-type beta-lactamase producing Klebsiella pneumoniae in Guangzhou area].

OBJECTIVE: To determine the prevalence and genotypes of TEM- and SHV-type beta-lactamase-producing Klebsiella pneumoniae in Guangzhou area. METHODS: Genotype determination of TEM- and SHV-type beta-lactamases were performed by PCR amplification followed by denaturing high-performance liquid chromatography (DHPLC) and DNA sequencing among 57 strain of klebsiella pneumonia obtained from the hospitals in Guangzhou. RESULTS: The genes bla(TEM) and bla(SHV) were amplified from all strains. TEM-116 type ESBLs were found in 56.14% (32/57) of the isolates. SHV-12 (n = 19), -11 (n = 11), -2a (n = 6), -28 (n = 4), -26 (n = 1), -33 (n = 1) and five novel SHV-type beta-lactamases were identified among the SHV-type beta-lactamases. These novel enzymes were designated from SHV-64, -65, -66, -67 and SHV-69, which derived from SHV-1 beta-lactamase or SHV-12 ESBL. A total of 94.74% of the isolates (54/57) produced both TEM- and SHV-type beta-lactamases simultaneously, in which 13.0% were TEM-116 and SHV-12 (n = 12). CONCLUSION: TEM-116 and SHV-12 are the predominant TEM- and SHV-type genotypes of Klebsiella pneumoniae producing beta-lactamases in Guangzhou. This area is confronted with the prevalence of the phenotypes of Klebsiella pneumoniae that simultaneously produce TEM- and SHV-type beta-lactamases.