Yong Chen

Dissemination and characterization of NDM-1-producing Acinetobacter pittii in an intensive care unit in China.

The sporadic emergence of New Delhi metallo-β-lactamase-1 (NDM-1)-producing Acinetobacter spp. has been reported in China; however, NDM-1-positive bacteria epidemics are rarely reported in intensive care units (ICUs) in China, or even in the world. During 15 months surveillance Acinetobacter spp. isolated from patients, heathcare workers and surfaces of a Chinese ICU were screened for the bla(NDM-1) gene. A total of 27 of 3114 Acinetobacter spp. strains were NDM-1 positive and identified as A. pittii with sequence type 63 (ST63) by multilocus sequence typing. Of the 27 NDM-1-positive A. pittii strains, 22 were isolated from the ICU surfaces and grouped into a major clone A using pulsed-field gel electrophoresis typing, while the other five strains isolated from the patients were classified into three clones (A, B and C). The bla(NDM-1) gene was located on a 45-kb plasmid for all three A. pittii clones. The plasmid could be transferred to A. pittii and A. baumannii recipients at both 30 and 37°C but not to Escherichia coli J53. The plasmid could not be classified into any of the known plasmid incompatibility groups. The bla(NDM-1) region in the plasmid was flanked by two insertion sequence elements, ISAba125 and ISAba11, and no other carbapenemase gene was present in this NDM-1-positive A. pittii isolate. Thus, we present the first report on the transmission and characterization of NDM-1-producing A. pittii in an ICU in China as well as a novel bla(NDM-1) gene-bearing plasmid.

A nosocomial outbreak of KPC‐2‐producing Klebsiella pneumoniae in a Chinese hospital: dissemination of ST11 and emergence of ST37, ST392 and ST395

In China, Klebsiella pneumoniae carbapenemase (KPC) -producing K.xa0pneumoniae isolates have been identified. However, little is known about the spread and outbreak of KPC-producing enterobacterial pathogens. In this study, 48 non-duplicated KPC-producing isolates were analysed for genetic relatedness by pulsed-field gel electrophoresis (PFGE), antimicrobial susceptibility by E-test, and sequence type (ST) by multilocus sequence typing. S1-PFGE and Southern blot were used for plasmid profiling, and PCR and subsequent sequencing were performed to determine the effects of genetic background on the blaKPC gene. From December 2011 to June 2012, an outbreak of the KPC-2-producing K.xa0pneumoniae was observed. The 48 isolates of K.xa0pneumoniae are categorized into eight PFGE types (A1, A2, A3, A4, B, C, D and E). The predominant pathogens of the outbreak were strains with PFGE types A1, A2 and A3, which all belong to ST11. Furthermore, ST37, ST392 and ST395 KPC-2-producing K.xa0pneumoniae isolates have also been sporadically identified. The blaKPC-2 -carrying plasmids vary in size from 30 to 220xa0kb. The genetic environments of the blaKPC-2 gene for most strains were consistent with the genetic structure of blaKPC-2 on the plasmid pKP048. In conclusion, the dissemination and outbreak of KPC-2-producing K.xa0pneumoniae isolates in this study appeared to be clonal, and ST11 K.xa0pneumoniae was the predominant clone attributed to the outbreak. This is the first study to report the emergence and spread of KPC-producing K.xa0pneumoniae ST392 and ST395 worldwide. Our findings suggest that horizontal transfer of Tn3-based transposons might mediate the spread of blaKPC-2 gene between different K.xa0pneumoniae clones in China.

NDM-1–producing Strains, Family Enterobacteriaceae, in Hospital, Beijing, China

To the Editor: The prevalence of New Delhi metallo-β-lactamase-1 (NDM-1)–producing strains (family Enterobacteriaceae) in China remains unclear. Recently, to clarify the prevalence of blaNDM-1 in Enterobacteriaceae strains, we carried out retrospective surveillance for blaNDM-1 among carbapenem-resistant enterobacterial strains isolated from patients at the Chinese PLA General Hospital in Beijing. This tertiary teaching hospital has 4,000 beds and 12,000 daily outpatient visits. More than 50% of patients admitted to the hospital are from areas outside Beijing. During January 2009–June 2013, a total of 8,586 enterobacterial isolates were obtained from routine clinical samples that had been passively sent to the microbiology department. Of these, 242 (2.8%) strains exhibited resistance to carbapenems. n nIn this study, we used PCR amplification to screen the carbapenem-resistant strains for the blaNDM-1 gene and other common resistance determinants. The MICs of various antimicrobial drugs were measured by E-test (AB bioMerieux, Solna, Sweden). S1 nuclease pulsed-field gel electrophoresis and Southern blot analysis were used to identify the sizes of blaNDM-1-carrying plasmids. The incompatibility (Inc) groups of the plasmids were detected by several multiplex and simplex PCRs. Multilocus sequence typing (MLST) was carried out for Klebsiella pneumoniae and Escherichia coli isolates, according to protocols provided on MLST websites (www.pasteur.fr/recherche/genopole/PF8/mlst/Kpneumoniae.html and http://mlst.ucc.ie/mlst/dbs/Ecoli). The transferability of plasmids was identified by conjugation experiments. n nFive blaNDM-1-positive enterobacterial isolates of the following species were identified: E. coli (1 isolate in October2010), K. pneumoniae (1 isolate in August 2012), Providencia rettgeri (1 isolate in October 2012), Enterobacter cloacae (1 isolate in November 2012), and Raoultella ornithinolytica (1 isolate in March 2013). According to the 2013 Clinical and Laboratory Standards Institute performance standard M100-S23 (www.clsi.org/), the NDM-1-producing K. pneumoniae (IR5047) isolate exhibited low-level resistance to imipenem and meropenem, whereas other isolates showed high-level resistance to carbapenems. Only E. coli and Providencia rettgeri, which carry 16S rRNA methylase genes, exhibited high-level resistance to amikacin (Table). S1 nuclease pulsed-field gel electrophoresis and Southern blot analysis showed that the blaNDM-1 gene was located on plasmids of various sizes belonging to different Inc groups. The K. pneumoniae isolate was defined as a novel ST1240 with the allelic profile 2–1-1–1-1–3-24, and the E. coli isolate was identified as ST167. n n n nTable n nPhenotype and molecular characteristics of NDM-1–producing strains isolated from Chinese PLA General Hospital, Beijing, China, 2009–2013* n n n nIn China, various blaNDM-1-carrying strains of the Enterobacteriaceae have been sporadically identified, including K. pneumoniae, K. oxytoca, Escherichia coli, Enterobacter cloacae, Enterobacter aerogenes, and Citrobacter freundii (1–4). We identified a P. rettgeri isolate and an R. ornithinolytica isolate that produced NDM-1. The blaNDM-1-positive P. rettgeri isolates have also been identified in Pakistan, India, Canada, and Mexico, whereas the NDM-1-producing R. ornithinolytica strain has only been detected in India (5–9). In this study, all 5 NDM-1–producing strains were isolated only once, and no dissemination of NDM-1–producing strains of Enterobacteriaceae has been found. Two strains (K. pneumoniae and Enterobacter cloacae) were isolated within 48 hours of the patient’s hospital admission, indicating the infections were imported (from Shandong and Hebei Provinces, respectively). Escherichia coli, P. rettgeri, and R. ornithinolytica were isolated 48 hours after admission of patients (from Henan and Hebei Provinces). Therefore, the patients might have acquired the NDM-1–producing Enterobacteriaceae strains at the hospital. n nHowever, the source of the blaNDM-1 determinant remains unclear. The possibility that the strains were imported cannot be excluded for the several reasons. First, examination to determine the infectious agent had not been performed for a considerable number of patients within 48 hours of their admission. Second, NDM-1–producing Enterobacteriaceae species have not spread in this hospital. Third, the blaNDM-1-carrying plasmids in the same Inc group and of similar size exhibited substantial differences in resistance determinants (Table), which suggests a different evolutionary origin for these isolates. In an additional survey of clinical data, we found no epidemiologic relationship between the patients who were infected by NDM-1–producing pathogens. These data suggest a sporadic pattern of NDM-1–producing enterobacteria in the hospital. n nSequencing analysis (data not shown) indicated that the blaNDM-1-carrying plasmid carried by K. pneumoniae (≈50 kb, IncX3) was different from the plasmid found in the Acinetobacter pitti isolate that was disseminated in an intensive care unit of the Chinese PLA General Hospital in 2008 (10). This finding suggests that the 2 plasmids had a different evolutionary origin. The IncX3 plasmid that we found was highly homologous (>99%) to the plasmid pNDM-HN380 (GenBank accession no. {type:entrez-nucleotide,attrs:{text:JX104760,term_id:402914504,term_text:JX104760}}JX104760), which has been identified in several Enterobacteriaceae strains isolated from patients in southern China (1). This finding showed that the IncX3 plasmid that was 50 kb in size acted as the main factor mediating the transmission of the blaNDM-1 gene across China. IncA/C plasmids are the leading group of blaNDM-1-carrying plasmids and have been detected in E. coli isolated from China (1). In this study, E. coli (IR5028) and P. rettgeri (IR5337) carried IncA/C plasmids. However, these 2 strains exhibited diverse resistant determinants on these plasmids (Table). This observation suggested that the 2 plasmids have different integrating processes. For R. ornithinolytica, the blaNDM-1 gene was located on an IncN plasmid of ≈70 kb, which is very different from other plasmids. n nIn conclusion, we identified various NDM-1–producing enterobacterial isolates at the Chinese PLA Hospital in Beijing and the emergence of novel blaNDM-1-carrying clones among common species of Enterobacteriaceae, such as K. pneumoniae ST1240 and E. coli ST167. There is an urgent need for monitoring and surveillance of epidemiologic and genotypic profiles of NDM-1–producing Enterobacteriaceae species in China.

Draft Genome Sequence of an Acinetobacter Genomic Species 3 Strain Harboring a blaNDM-1 Gene

Here we report the draft genome sequence of one Acinetobacter genomic species 3 strain, D499, which harbors the bla(NDM-1) gene. The total length of the assembled genome is 4,103,824 bp, and 3,896 coding sequences (CDSs) were predicted within the genome. A previously unreported bla(NDM-1)-bearing plasmid was identified in this strain.

Transcriptome Profiles of Human Lung Epithelial Cells A549 Interacting with Aspergillus fumigatus by RNA-Seq.

Lung epithelial cells constitute the first defense line of host against the inhaled Aspergillus fumigatus; however, the transcriptional response of human alveolar type II epithelial cells was still unclear. Here we used RNA-Seq technology to assess the transcriptome profiles of A549 cells following direct interaction with conidia of A. fumigatus. The total number of identified genes was 19118. Compared with uninfected A549 cells, 459 genes were differentially expressed in cells co-incubated with conidia for 8 h, including 302 up-regulated genes and 157 down-regulated genes. GO and KEGG pathway enrichment analysis showed that most of the up-regulated genes were related to immune response, chemotaxis and inflammatory response and enriched in cytokine-cytokine receptor interaction, JAK-STAT and MAPK signaling pathways. The down-regulated genes were mainly enriched for terms associated with development, hemopoiesis and ion transport. Among them, EGR4 and HIST1H4J gene had the maximum of fold change in up-regulated and down-regulated genes, respectively. Fourteen up-regulated genes and three down-regulated genes were further validated and significant increase on expression of IL-6, IL-8 and TNF-α in A549 cells were confirmed by qRT-PCR during the interaction of A549 cells with A. fumigatus. Besides, western blot showed that expression of two proteins (ARC, EGR1) significantly increased in A549 cells during interaction with A. fumigatus conidia for 8h. Interference of endogenous expression of ARC or EGR1 protein in A549 cells reduced the internalization of A. fumigatus. These results provided important insights into dynamic changes of gene expression in lung epithelial cells, especially its strong immunological response against A. fumigatus infection.

Characterization of Staphylococcus aureus from distinct geographic locations in China: an increasing prevalence of spa-t030 and SCCmec type III.

Staphylococcus aureus belongs to one of the most common bacteria causing healthcare and community associated infections in China, but their molecular characterization has not been well studied. From May 2011 to June 2012, a total of 322 non-duplicate S. aureus isolates were consecutively collected from seven tertiary care hospitals in seven cities with distinct geographical locations in China, including 171 methicillin sensitive S. aureus (MSSA) and 151 MRSA isolates. All isolates were characterized by spa typing. The presence of virulence genes was tested by PCR. MRSA were further characterized by SCCmec typing. Seventy four and 16 spa types were identified among 168 MSSA and 150 MRSA, respectively. One spa type t030 accounted for 80.1% of all MRSA isolates, which was higher than previously reported, while spa-t037 accounted for only 4.0% of all MRSA isolates. The first six spa types (t309, t189, t034, t377, t078 and t091) accounted for about one third of all MSSA isolates. 121 of 151 MRSA isolates (80.1%) were identified as SCCmec type III. pvl gene was found in 32 MSSA (18.7%) and 5 MRSA (3.3%) isolates, with ST22-MSSA-t309 as the most commonly identified strain. Compared with non-epidemic MRSA clones, epidemic MRSA clones (corresponding to ST239) exhibited a lower susceptibility to rifampin, ciprofloxacin, gentamicin and trimethoprim-sulfamethoxazole, a higher prevalence of sea gene and a lower prevalence of seb, sec, seg, sei and tst genes. The increasing prevalence of multidrug resistant spa-t030 MRSA represents a major public health problem in China.

Epidemiology and Molecular Characterizations of Azole Resistance in Clinical and Environmental Aspergillus fumigatus Isolates from China.

ABSTRACT Azole resistance in Aspergillus fumigatus has emerged as a worldwide public health problem. We sought here to demonstrate the occurrence and characteristics of azole resistance in A. fumigatus from different parts of China. A total of 317 clinical and 144 environmental A. fumigatus isolates from 12 provinces were collected and subjected to screening for azole resistance. Antifungal susceptibility, cyp51A gene sequencing, and genotyping were carried out for all suspected azole-resistant isolates and a subset of azole-susceptible isolates. As a result, 8 (2.5%) clinical and 2 (1.4%) environmental A. fumigatus isolates were identified as azole resistant. Five azole-resistant strains exhibit the TR34/L98H mutation, whereas four carry the TR34/L98H/S297T/F495I mutation in the cyp51A gene. Genetic typing and phylogenetic analysis showed that there was a worldwide clonal expansion of the TR34/L98H isolates, while the TR34/L98H/S297T/F495I isolates from China harbored a distinct genetic background with resistant isolates from other countries. High polymorphisms existed in the cyp51A gene that produced amino acid changes among azole-susceptible A. fumigatus isolates, with N248K being the most common mutation. These data suggest that the wide distribution of azole-resistant A. fumigatus might be attributed to the environmental resistance mechanisms in China.

Characteristics of qacA/B-positive Staphylococcus aureus isolated from patients and a hospital environment in China

OBJECTIVESnThis study was designed to demonstrate the characteristics of qacA/B-positive Staphylococcus aureus in China.nnnMETHODSnOne hundred and forty-five MRSA and 178 MSSA from clinical specimens from seven hospitals in different regions of China, 70 MRSA from superficial sites of patients and 106 MRSA from environmental samples from an ICU were collected and screened for the presence of the qacA/B gene. The qacA/B-positive isolates and 72 randomly selected qacA/B-negative control isolates were further characterized by MLST, spa typing and detection of toxin genes, as well as antimicrobial and chlorhexidine susceptibility. SCCmec typing was conducted for MRSA. PFGE was conducted for qacA/B-positive isolates.nnnRESULTSnTwenty-five (7.8%) of the 321 MRSA isolates harboured qacA/B, including 11 isolates from clinical specimens (7.6%), 12 isolates from patients superficial sites (17.1%) and 2 isolates from an ICU environment (1.9%). Ten and five qacA/B-positive MRSA were identified as ST239-t030-MRSA-III and ST239-t037-MRSA-III, respectively. Six PFGE clusters and five singletons were identified among the 25 qacA/B-positive MRSA. Only one (0.6%) of the 178 MSSA isolates harboured qacA/B. qacA/B carriage in MRSA was statistically associated with spa-t037 and the presence of mupA. Compared with qacA/B-negative MRSA, the qacA/B-positive MRSA exhibited a lower susceptibility to chlorhexidine and higher resistance rates to clindamycin and trimethoprim/sulfamethoxazole.nnnCONCLUSIONSnCarriage of qacA/B, although it had a low prevalence, might be the main reason for declining susceptibility to chlorhexidine in MRSA from Chinese patients and is probably associated with spa-t037 and the presence of the mupA gene.

Emergence of TR46/Y121F/T289A in an Aspergillus fumigatus Isolate from a Chinese Patient.

Azole resistance in Aspergillus fumigatus is increasingly reported and evolving into a global health problem (1).…

A data-driven mathematical model of multi-drug resistant Acinetobacter baumannii transmission in an intensive care unit

Major challenges remain when attempting to quantify and evaluate the impacts of contaminated environments and heterogeneity in the cohorting of health care workers (HCWs) on hospital infections. Data on the detection rate of multidrug-resistant Acinetobacter baumannii (MRAB) in a Chinese intensive care unit (ICU) were obtained to accurately evaluate the level of environmental contamination and also to simplify existing models. Data-driven mathematical models, including mean-field and pair approximation models, were proposed to examine the comprehensive effect of integrated measures including cohorting, increasing nurse-patient ratios and improvement of environmental sanitation on MRAB infection. Our results indicate that for clean environments and with strict cohorting, increasing the nurse-patient ratio results in an initial increase and then a decline in MRAB colonization. In contrast, in contaminated environments, increasing the nurse-patient ratio may lead to either a consistent increase or an initial increase followed by a decline of MRAB colonization, depending on the level of environmental contamination and the cohorting rate. For developing more effective control strategies, the findings suggest that increasing the cohorting rate and nurse-patient ratio are effective interventions for relatively clean environments, while cleaning the environment more frequently and increasing hand washing rate are suitable measures in contaminated environments.