Pyomelanin biosynthetic pathway in pigment-producer strains from the pandemic Acinetobacter baumannii IC-5

BACKGROUND Acinetobacter baumannii outbreaks have been associated with pandemic International Clones (ICs), but the virulence factors involved with their pathogenicity are sparsely understood. Pigment production has been linked with bacterial pathogenicity, however, this phenotype is rarely observed in A. baumannii. OBJECTIVES This study aimed to characterise the reddish-brown pigment produced by A. baumannii strains, and to determine its biosynthetic pathway by genomic approaches. METHODS Pigment characterisation and antimicrobial susceptibility were conducted by phenotypic tests. The clonal relationship was obtained by pulsed field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). The genome of an A. baumannii was obtained for characterisation of genes involved with pigment production. FINDINGS The pyomelanin was the pigment produced by A. baumannii. Strains were extensively drug resistant and belonged to the IC-5/ST79. The pyomelanin biosynthetic pathway was determined and presented a particular architecture concerning the peripheral (tyrB, phhB and hpd) and central (hmgB, hmgC and hmgR) metabolic pathway genes. The identification of a distant HmgA homologue, probably without dioxygenase activity, could explain pyomelanin production. Virulence determinants involved with adherence (csuA/BABCDE and a T5bSS-carrying genomic island), and iron uptake (basABCDEFGHIJ, bauABCDEF and barAB) were characterised. MAIN CONCLUSION There is a biosynthetic pathway compatible with the pyomelanin production observed in persistent A. baumannii IC-5 strains.

An outbreak of suspected Acinetobacter baumannii infection in a general intensive care unit / 中国感染控制杂志

Objective To analyze the epidemiological characteristics of a healthcare-associated infection(HAI) outbreak due to multidrug-resistant Acinetobacter baumannii (AB) in an intensive care unit(ICU), and provide basis for the prevention and control of HAI.Methods Epidemiological investigation and environmental hygiene monitoring methods were adopted to investigate patients who had pulmonary infection after they were admitted to the ICU of a hospital in April 1-26, 2015, risk factors were analyzed and corresponding preventive control measures were taken.Results A total of 15 cases of extensively drug-resistant AB(XDR-AB) healthcare-associated lower respiratory tract infection occurred.15 strains of AB were isolated from 15 patients.No.1, 3, 4, 5, No.6, 7, 8, 9, and No.10, 11 patients were detected AB with the same antimicrobial susceptibility testing results respectively;occurrence time of infection was relatively centralized.A total of 43 specimens from environmental surface and hands of health care workers(HCWs) were collected, detection rates of AB from bedside cabinet, monitor button, and hands of HCWs were 100.00%(1/1), 75.00%(6/8), and 66.67%(4/6)respectively.AB were not detected from specimens of treatment table, infusion pump button, and doctors' nasal swabs.By late May 2015, there were no new such cases in ICU.Conclusion This AB HAI may be spread through environmental surface and hands of HCWs in ICU, AB isolated from patients is extensively antimicrobial resistant, active treatment of patients and strict disinfection and isolation measures can effectively control further prevalence.

Establishment of an infection model using Caenorhabditis elegans-exten-sively drug-resistant Klebsiella pneumoniae / 中国感染控制杂志

Objective To establish an infection model using Caenorhabditis elegans (C.elegans)-extensively drug-resistant Klebsiella pneumoniae (XDRKP)system.Methods Clinically isolated XDRKP strains were used to infect C.elegans in the liquid killing assay,the nematode survival and the number of bacteria in C.elegans digestive tract was observed.Results C.elegans was significantly retarded after being infected by XDRKP,different concentra-tions of XDRKP led to different patterns of the worm death.Log-rank test showed that survival curves of C. elegans infected with 1 .5×106 CFU/mL of XDRKP and E.coli OP50 (control)were not significantly different (χ2 =0.08,P >0.05);survival curves of C.elegans infected with 1 .5 ×107 CFU/mL,1 .5 ×108 CFU/mL of XDRKP and E.coli OP50 were significantly different(χ2 =229.37,275.98,respectively,both P <0.001).The survival rates of 1 .5×108 and 1 .5 ×107 CFU/mL XDRKP groups were both lower than that of the control group.Supernatant suspension obtained from test was performed bacterial culture,identification and antimicrobial susceptibility testing, XDRKP was determined.After being infected with XDRKP 4,6,12,and 24 hours,the total number of bacteria in C.elegans were(0.28±0.02)×105 CFU/mL,(0.50 ±0.38)×105 CFU/mL,(1 .73 ±0.56)×105 CFU/mL,and (2.62±0.53)×105 CFU/mL,respectively,the number of bacteria in C.elegans digestive tract was significantly different at different time points (F =1 363.39,P <0.001).Conclusion The infection model of C.elegans-XDRKP is established successfully.

Clinical distribution and antimicrobial resistance of Acinetobacter bau-mannii isolated between 2011 and 2013 / 中国感染控制杂志

Objective To investigate the clinical distribution and change in antimicrobial resistance of Acinetobact-er baumannii (A.baumannii)from a hospital between 2011 and 2013,so as to provide guidance for clinical treat-ment.Methods Sources and antimicrobial susceptibility testing results of A.baumannii from a hospital were ana-lyzed statistically.Results A total of 14 705 bacterial isolates were isolated in 2011 —2013,13.59%(n=1 999)of which were A.baumannii isolates,the percentage of A.baumannii in isolated pathogens in 3 years was 12.74%, 13.05%,and 14.85% respectively,which showed a rising trend (χ2 =9.458,P =0.002).The main specimen was sputum (n = 1 541 ,77.09%),bacteria were mainly isolated from patients in respiratory disease department (21 .71 %),surgical intensive care unit (16.26%),and emergency intensive care unit (8.26%).Antimicrobial re-sistance rates of A.baumannii increased year by year(all P <0.05);multidrug-resistant and extensively drug-resist-ant A.baumannii also increased year by year (all P <0.001).Conclusion Isolation rate and antimicrobial resistance rate of A.baumannii strains increase year by year,multidrug-resistant and extensively drug-resistant A.baumannii strains are obvious,which should be paid more attention in clinical department.

Survey and control of extensively drug-resistant Acinetobacter baumannii infection outbreak in a basic-level hospital / 中国感染控制杂志

Objective To survey and control an extensively drug-resistant Acinetobacter baumannii (A.bauman-nii)(XDRAB)lower respiratory tract infection (LRTI)outbreak in intensive care unit (ICU)of a hospital. Methods From October 27,2013 to December 27,2013,5 cases of XDRAB LRTI occurred in ICU,epidemiological investigation was conducted,sources and transmission routes of infection were searched,intervention measures were performed.Results XDRAB were isolated from patients’sputum and environmental object surface,drug-resistant spectrums of isolated XDRAB were almost the same,suggesting the outbreak was due to the contamination of envi-ronment by the same pathogen.54 specimens were taken before disinfection,26 were positive,XDRAB were isola-ted from door handles,sheets and telephones.Investigation concluded that the outbreak of XDRAB infection was due to contamination of indoor environment and equipment,incomplete disinfection,and inadequate hand hygiene compliance of health care workers.After the implementation of a series of control measures,XDRAB was not found,and there was no new XDRAB infection cases.Conclusion Environment contamination is the main cause of this XDRAB healthcare-associated infection(HAI)outbreak,strict implementation of isolation,prevention and con-trol measures of MDROs can effectively control HAI outbreak caused by A.baumannii.

Drug resistance and short-term efficacy of second-line drugs in patients with multidrug-resistant pulmonary tuberculosis in Zhejiang Province / 中华临床感染病杂志

Objective To investigate drug resistance and clinical efficacy of second-line anti-tuberculosis drugs in patients with multidrug-resistant pulmonary tuberculosis.Methods A total of 183 multi-drug resistant pulmonary tuberculosis (MDR-PTB) patients received standard anti-tuberculosis treatment in Zhejiang Provincial Center for Diagnosis and Treatment of Tuberculosis during March 2011 and March 2013.Patients were divided into four groups according to the results of first-line anti-tuberculosis drugs susceptibility test:group A (n =30) resistant to isoniazid (H) and rifamipicin (R) ; group B (n =28) resistant to HR and ethambutol (E) ; group C (n =53) resistant to HR and streptomycin (S) ; groups D (n =72) resistant to HRES.Drug susceptibility tests of second-line drugs kanamycin (Km),protionamide (Pto),paraaminosalicylic acid (PAS) and levofloxacin (Lfx) were performed.Negative conversion rates of mycobacterium tuberculosis in sputum culture were also observed and compared among different groups with x2 test.Results Among 183 MDR-PTB patients,49 cases (26.8％) were resistant to Lfx,which was significantly higher than that of Km (8.7％,n =16),Pto (13.1％,n =24) and PAS (6.6％,n=12) (x2 =37.983,P＜0.05).The resistant rate to Lfx in group D was 45.8％ (33/72),which was higher than that in group A (2/30,6.7％),group B (6/28,21.4％) and group C (8/53,15.1％) (x2 =14.413,5.047 and 13.087,P ＜0.05).The occurrence of pre-extensively drug resistance (Pre-XDR) in group D was 34.7％ (25/72),which was higher than that in group A (3/30,10.0％) and group C (9/53,17.0％) (x2 =6.499 and 4.852,P ＜ 0.05).Among 157 MDR-PTB patients who received standard anti-tuberculosis treatment for one year,the negative conversion rate of mycobacterium tuberculosis in sputum culture was 87.3％ (137/157).The negative conversion rate in group D was lower than that in other groups,but the difference was not of statistical significance (x2 =1.899,P ＞ 0.05).Conclusions The efficacies of second-line anti-tuberculosis drugs vary among MDR-TB patients resistant to different firstline anti-tuberculosis drugs.The sensitivity tests results of the first-line drugs may serve as reference for MDR chemotherapy regimen in lack of test results of second-line drugs.