The key to improve the clinic antimicrobial therapy results is correct diagnosis of infection,pathogens and antibiotic resistance.To deal with increasingly complex pathogens and drug resistance,the clinic and lab should cooperate and communicate as often as possible,improve the level of pathogen diagnosis,interpretate of the microbiological examination report correctly and explore the mechanisms and treatment of antimicrobial resistant pathogens.Besides,they should make full use of the inflammatory markers to further enhance anti-infective levels.

The term "superbugs" refers to microbes with resistance to almost all antibiotics specifically recommended for the treatment. The superbugs disseminating worldwide included methicillinresistant Staphylococcus aureus ; vancomycin-resistant Staphylococcus aureus ; vancomycin-resistant Enterococcus ;carbapenem-resistant Gram-negative bacillus. Due to abuse of antibiotics, novel "superbug"emerged gradually, which demands optimizing antibiotic use, reinforcing surveillance of "superbugs" as well as nosocomial infection control.

Community-acquired methicillin-resistant Staphylococcus aureus ( CA-MRSA ) has been increasingly frequently isolated from patients worldwide, and is an emerging threat to public health.CA-MRSA strains differ from hospital-acquired MRSA strains in their epidemiologies, clinical features and genetic backgrounds, and the predominant CA-MRSA strains vary between geographic settings.This paper reviews literatures on the definition, epidemiology, clinical manifestations, treatment and virulent factors of CA-MRSA or CA-MRSA infection, and points out that we should further promote studies on epidemiology, molecular genetic properties of CA-MRSA and clinical management of CA-MRSA infection.

Objective To analyse the encoding gene sequence of extended spectrum ? lactamase produced by Klebsiella pneumoniae E95 strain in Zhejiang Province and identify its ESBLs subtype. Methods The gene of ESBLs produced by E95 strain was amplified by PCR. The purified PCR product was cloned into pGEM Teasy vector and then sequenced by Sanger's dideoxy chain termination composition method. Results The encoded gene of ESBLs was identified as SHV by PCR. Its PCR product had 812 nucleotides. It had the same gene sequence as the gene encoding SHV 12 discovered in Swiss. Conclusions The ESBLs produced by Klebsiella pneumoniae E95 strain isolated from a patient in Zhejiang Province is SHV 12.

Objective To construct the mice pneumonia model with imipenem-resistant Acinetobacter baumannii and provide experimental model in anti-pan-resistant Acinetobacter baumannii therapy study. Methods A total number of 120 4-week-old BALB/C male mice were randomly selected and divided into three groups including micro-intratracheal injection, ultrasonic atomizing and nasal dripping. The mice were treated with methotrexate to induce hypo-immunity in every group. These BALB/C mice of normal immunity and hypo-immunity were infected through Imipenem-resistant Acinetobacter baumannii by microintratracheal injection, ultrasonic atomizing and nasal dripping, respectively. The morbidity, mortality,bacterial clearance rate and histopathology in lung were determined. Results The morbidities of BALB/C mice with hypo-immunity infected by micro-intratracheal injection and ultrasonic atomizing achieved 100%(30/30), while the mortalities were 100% (10/10) and 33.3% (3/10), respectively. Mice in two groups above displayed the influx of neutrophils, lymphocytes and macrophages in the peri-bronchial and alveolar interstitial space 12-24 h after pulmonary infection. In addtion, the mice in micro-intratracheal injection group displayed coUapse of partial alveolar walls, formation of abscesses and bacterial colonies in alveoli. While the lung pathology in mice of ultrasonic atomizing group was characterized by cell degeneration in some regions in the lungs, slight relaxation, congestion in alveolar wall vessels and normal of bronchial and alveolar tissue 24 h after inoculation. Degeneration in peri-tracheal and peri-bronchial areas was observed 24-48 h after inoculation, along with highly expanded pulmonary blood vessels and edems. The inflammation was reduced at 48 hours. There was no obvious pulmonary infection in BALB/C mice with hypo-immunity by nasal dripping with mortality of 0% (0/10) and no significant histopathologic change in lungs. Conclusions BALB/C mice with hypo-immunity pneumonia model with Imipenem-resistant Acinetobacter baumannii can be conducted by micro-intratracheal injection or ultrasonic atomizing, but the latter has the advantages of high-productivity, easy-operation, low-cost, time-saving and usefulness. Mice with normal immunity are not susceptible to imipenem-resistant Acinetobacter baumannii.

Objectives To investigate the properties and distributions of ampC gene among different drug-resistant strains of Serratia marcescens,and the relationship of control gene ampR with AmpC enzymes′ expressions.Methods According to the results of inducting experiment with 1/2 MIC of beta-lactam antibiotics (CTX),three-dimensional testing and isoelectric focusing electrophoresis testing,143 strains of S.marcescens were classified into three groups:including induction group, continuous low-production group and hyperproduction group. In each group, the sequences of ampC and ampR genes were amplified using the method of PCR. The products of PCR were analyzed. The plasmid-mediated beta-lactamases were detected using the method of conjugation experiment.Results Among 143 strains of S.marcescens, the continuous low -production strains, induction strains and hyperproduction strains were 14,103,and 18, respectively.125 and 99 strains were ampC and ampR gene positive, respectively.The detection rate of ampR in hyperproduction group was lower than other groups.5 sites of ampC genes and 4 sites in the Open Reading Frame (ORF) of ampR gene were easily mutated in 5 induction strains and 2 hyperproduction strains.Conclusions The production of inducing drug-resistance of some S.marcescens might be related to mutation of ampC gene encoding AmpC beta-lactamases and the ORF mutation in ampR. The continuous hyperproduction drug-resistance had something to do with deletion mutation in ampR in segmental hyperproduction strains.The plasmid-mediated AmpC enzymes hadn′t been found in S.marcescens.

Objective To investigate the distribution of 16S rRNA methylase genes in Klebsiella pneumoniae strains producing Klebsiella pneumoniae ealbapenenase type 2(KPC-2).Methods A total of 37 Klebsiella pneumoniae isolates producing KPC-2 were collected.The minimal inhibitory concentrations (MICs)of these strains to amikacin,gentamyein and netilmicin were determinated by agal dilution method.Six 16S rRNA methylase genes(armA,rmtA,rmtB,rmtC,rmtD and npmA)were detected by PCR.Results The resistant rates to amikacin,gentamycin and netilmicin were 97.3%(MIC50≥1024μg/mL).Among those resistant strains,8 were armr/A positive,25 were rmtB positive,4 were both armA and rmtB positive.and no other 16S rRNA methylase genes were found.The total positive rate of 16S rRNA methylase genes was 78.4%(29/37).Conclusion 16S rRNA methylase genes armA and rmtB ale prevalent in Klebsiella pneumoniae strains producing KPC-2.

Objective To investigate the effect of resistance nodulation division (RND) efflux pumps on reduced susceptibility to tigecycline in carbapenem-resistant Acinetobacter baumanii.Methods Totally 631 isolates of Acinetobacter baumanii were collected from 16 hospitals in 7 provinces in 2010.Genes oxa-51 and oxa-23 were detected by PCR method,and the ST profiles were determined by multilocus sequence typing (MLST).The disk susceptibility assay was used to determine the inhibition zone diameters of β-lactams,aminoglycosides,macrolides,tetracyclines,carbapenems,tigecycline and polymyxin.The minimum inhibitory concentration (MIC) of tigecycline was determined by E-test in strains with inhibition zone diameters ≤ 12 mm on tigecycline.The expression of operon genes adeB,adeG and adeJ was determined with efflux pump inhibitor NMP (N-methyl-2-pyrrolidone) for detection of efflux pump inhibitor phenotype.The isolates of Acinetobacter baumanii which were resistant both to tigecycline and carbapenems and with the inhibited phenotype of efflux pump inhibitor were collected as the experiment group,the isolates which were susceptible to tigecycline but resistant to carbapenems were collected as the control group,and ATCC 19606 was used as the reference strain.The expressions of adeABC,adeFGH and adeIJK were quantified by q-PCR at the transcriptional level.Genes adeR,adeS and adeL were amplified and sequenced using PCR method to find polymorphic locus and insertion sequences.Results There were 32 isolates of Acinetobacter baumanii with reduced susceptibility to tigecycline and carbapenem-resistant.Eight isolates were with the inhibited phenotype by efflux pump inhibitor.And 4 strains which were susceptible to tigecycline but resistant to carbapenems were selected as the control.The expressions of adeABC in A518,Z1219 and A527 of experiment group were 13-fold,5-fold and 7-fold higher than reference strain ATCC19606,respectively.The expressions of adeFGH and adeIJK were up-regulated slightly in some isolates.Transcript of adeABC was not found in control group strains A207 and A1731,and the expressions of adeABC,adeFGH and adeIJK were not up-regulated in other isolates.The single nucleotide polymorphism (SNP) was detected in adeR (E220K) and adeS (A130D),respectively.ISAab1 insertion sequence was identified in adeS of adeABC-over expressed isolates.No mutation was found in adeL.Conclusion High expression of adeABC pump may play an important role in tigecycline resistance in carbapenem-resistant Acinetobacter baumannii,mainly due to the insertion of ISAba1 sequence in its regulator gene adeS,but other mechanism of tigecycline resistance may not be excluded.

Objective To investigate the related clinical factors and homology of strains in Stenotrophomonas maltophilia (S. Maltophilia) infections in 15 patients with liver transplantation. Methods Fifteen patients with S. Maltophilia infection from September to December 2006 were enrolled and their clinical data were collected. Minimal inhibitory concentrations (MICs) of 10 antimierobial agents against S. Maltophilia were determined by Etest strips. Antibiogram was carried out by resistance analysis assembly with WHONET 5 software. The genomic DNA of all the isolates was digested with Xbal and subjected to pulse-field gel electrophoresis (PFGE). Results All patients received mechanical ventilation during the treatment and had a history of long-term use of extended-spectrum β-lactamases and quinolones. MICs of 10 antimicrobial agents indicated that S. Maltophilia were susceptible to several antimicrobial agents including compound sulfamethoxazole and ciprofloxacin, but the best active agent against these resistant isolates was minocycline in vitro. The results of all 15 S. Maltophilia antibiograms were accordance with PFGE patterns. All 15 S. Maltophilia isolates were classified as 2 PFGE patterns: 9 for pattern A and 6 for pattern B. Conclusion Mechanical ventilation might be associated with the S. Maltophilia septicemia in patients with liver transplantation.

Objective To investigate the resistance-related genes of Shigella sonnei with decreased susceptibility to fluoroquinolones.MethodsA total of 131 strains of Shigella sonnei were analyzed for their antimicrobial susceptibility.Mutations within the quinolone resistance determining regions (QRDR) of gyrA and parC were detected by polymerase chain reaction (PCR) and PCR products were then sequenced. Meanwhile, the plasmid-mediated quinolone resistance (PMQR) genes,qnr and aac(6')-Ib-cr were screened by PCR.ResultsResistance rates of 131 Shigella sonnei isolates to nalidixic acid,tetracycline,ampicillin and trimethoprim-sulfamethoxazole were 100.0％,93.9％,93.2％ and 92.8％,respectively.All strains were susceptible to norfloxacin,ciprofloxacin,levofloxacin,while 94％ nalidixic acid-resistant Shigella sonnei strains showed reduced susceptibilities to fluoroquinolones.All of nalidixic acid-resistant Shigella sonnei strains presented a single mutation at codon 83 (Ser→Leu) of gyrA genes,but no mutations were detected in parC gene.And PMQR genes qnr and aac (6’)-Ib-cr were not detected.Conclusions The nalidixic acid-resistant Shigella sonnei strains with reduced susceptibility to fluoroquinolones are common in the clinical practice,which may mainly due to a single mutation at codon 83 (Ser→Leu) of gyrA genes.