Tracing and transmission analysis of a nosocomial infection event caused by hypervirulent Acinetobacter baumannii / 中华临床感染病杂志

Objective:To trace and identify the source and the transmission vector of a nosocomial infection event caused by hypervirulent Acinetobacter baumannii. Methods:Nine strains of carbapenem-resistant Acinetobacter baumannii (CRAB) isolated from respiratory general ward and respiratory intensive care unit in Shenzhen People’s Hospital from July to August 2018 were collected. Environmental specimens such as ward environmental objects and medical staff’s hands were also collected. Vitek 2 was used for identification of bacterial species and drug susceptibility testing; Illuinam HiSeq 2500 platform, Staramr, Ridom SeqSphere+ were used for whole genome sequencing, drug resistance gene detection and multi-locus sequence typing (MLST); and IQ-Tree software, BEAST2 software package and SCOTTI software were used to construct phylogenetic tree and propagation path map. At the same time, the virulence of pathogenic bacteria was detected by mouse pneumonia model. Results:The 9 isolated CRAB strains were all ST2 type, all carried the carbapenem-resistant gene blaOXA-23, and the capsular types were KL49, KL3, KL77 and KL2, respectively. One of the CRAB strains isolated from removable ventilator screen was ST2 type and KL49 type capsule. Phylogenetic tree analysis showed that the environmental isolates were located in the same branch as 5 CRABs, and the transmission path map showed that these 5 CRABs were also located in the same transmission chain. Five strains of CRAB were involved in four lethal cases, and in vivo experiments in mice confirmed that the strains causing lethal infection had a hypervirulent phenotype. Conclusions:Highly virulent Acinetobacter baumannii can colonize the surface of mobile medical equipment, and sharing these equipment may lead to nosocomial spread of pathogens. The use of new propagation path analysis tools has certain reference significance for the investigation of propagation events.

Hypervirulent Klebsiella pneumoniae serotype K1 induces liver abscess through activating NLRP3 inflammasome / 中华微生物学和免疫学杂志

Objective:To investigate whether the hypervirulent Klebsiella pneumoniae (hvKP) induces liver abscess through activating NLRP3 inflammasome. Methods:K1-hvKP and K35-non-hvKP bacterial suspensions were intraperitoneally injected into C57BL/6 mice to establish the models of liver abscess. Human peripheral blood neutrophils were sorted by immunomagnetic beads with CD45 + and Gr-1 + , and the purity was detected by flow cytometry. The concentrations of capsular polysaccharide of K1-hvKP and K35-non-hvKP were detected by total carbohydrate assay kit. The expression of IL-18 and IL-33 by neutrophils at mRNA and protein levels was detected by real-time fluorescence quantitative PCR and ELISA, respectively. The activation of NLRP3 inflammasome in neutrophils was detected by Western blot. Neutrophil extracellular trap formation (NETosis) was observed under confocal laser scanning microscope. Results:The C57BL/6 mice with K1-hvKP infection had significantly serious liver abscess as compared with the K35-non-hvKP-infected mice. The purity of human neutrophils was more than 95%. The concentration of capsular polysaccharide in K1-hvKP was significantly higher than that in K35-non-hvKP. Compared with K35-non-hvKP, K1-hvKP significantly promoted the neutrophils to express IL-18 and IL-33 at both mRNA and protein levels, enhanced the activation of NLRP3 and induced NETosis.Conclusions:This study suggested that hvKP could promote NETosis by activating NLRP3 inflammasome to cause liver abscess.

Construction of hypervirulent Klebsiella pneumoniae strain with hfq gene deletion and study on its biological characteristics / 中华微生物学和免疫学杂志

Objective:To construct a mutant strain of hypervirulent Klebsiella pneumoniae NTHU-K2044 with hfq gene deletion and to analyze its biological characteristics. Methods:The hfq gene of NTUH-K2044 was knocked out by homologous recombination technology to construct △ hfq mutant strain. Its biological characteristics including growth rate, environmental stress tolerance, biofilm formation, capsular polysaccharide synthesis, resistance to neutrophil phagocytosis and lethality to Galleria mellonella larvae were analyzed by comparing with the wild-type strain using phenotypic experiments. Results:The △ hfq mutant strain of hypervirulent Klebsiella pneumoniae NTHU-K2044 was successfully constructed. Phenotypic experiments showed that the △ hfq mutant strain had significantly slower growth rate, smaller colonies and decreased hypermucoviscosity. Its growth was significantly inhibited under different environmental stress conditions such as pH9, pH5.5, 0.7 mmol/L SDS, 5% NaCl, 0.1% H 2O 2 and high temperature of 50℃. In terms of virulence and pathogenicity, the △ hfq mutant strain showed decreased ability to form biofilm and capsule, significantly down-regulated expression of magA and rmpA genes required for capsule synthesis, lower survival rate in the neutrophil bactericidal test and obviously reduced lethality to Galleria mellonella larvae. Conclusions:As a RNA chaperone, Hfq protein could participate in post-transcriptional regulation and play an important role in regulating the physiology, environmental adaptability and virulence of hypervirulent Klebsiella pneumoniae. This study provided reference for further study on hypervirulent Klebsiella pneumoniae.

Characterisation of Neisseria meningitidis cc11/ET-15 variant by whole genome sequencing

BACKGROUND Neisseria meningitidis strains belonging to clonal complex 11 is the cause of numerous outbreaks and epidemics in the United States, Canada and Europe, accounting for 49.5% of cases of meningococcal disease caused by serogroup C worldwide. In Brazil, it is the second most frequent clonal complex within this serogroup. The genetic characterisation of cc11/ET-15 variants is important for the epidemiological monitoring of meningococcal disease, through the identification of circulating epidemic clones, to support specific actions of Health Surveillance aiming outbreaks control. OBJECTIVES The objective of this study was to identify features in the genome of cc11/ET-15 clones through whole-genome sequencing (WGS), that differ from cc11/non-ET-15 strains that could explain their virulence. METHODS The whole genome of three cc11/ET-15 representative strains were sequenced with a minimum coverage of 100X with the MiSeq System and compared to the genome of cc11/non-ET-15 strains. RESULTS Genome analysis of cc11/ET-15 variants showed the presence of resistance factors, mobile genetic elements and virulence factors not found in cc11/non-ET-15 strains. MAIN CONCLUSIONS Our results show that these strains carry virulence factors not identified in cc11/non-ET-15 strains, which could explain the high lethality rates attributed to this clone worldwide.

Characteristics of Klebsiella pneumoniae Isolates from Stool Samples of Patients with Liver Abscess Caused by Hypervirulent K. pneumoniae

Clinical characteristics in patients with hypervirulent Klebsiella pneumoniae infection and its capsular serotypes and multilocus sequence typing / 中华内科杂志

Objective To describe the clinical characteristics of hypervirulent Klebsiella pneumoniae (hvKP) infection.To analyze the antibiotic susceptibility of hvKP to provide the empiric antibiotic options.To investigate capsule serotype and sequence type (ST) of hvKP and their correlation with clinical profiles.Methods hvKP was defined as bacteria isolated from patients with community-acquired pyogenic liver abscess (CA-PLA) with co-infection sites outside liver or a bloodstream infection in a host without underlying biliary tract diseases.Patients with CA-PLA hospitalized in the First Hospital of China Medical University were retrospectively analyzed from January 2011 to December 2017.Antibiotic susceptibility was detected by automatic bacterial identification and antibiotic susceptibility analysis system in vitro.Polymerase chain reaction method and gene sequencing were used to detect the main capsule serotype and ST.Results A total of 140 cases with hvKP infection were enrolled.The co-infections outside liver abscess included 98 bloodstream infections,53 pneumonia,11 perianal abscess,10 urinary system infections,3 subphrenic abscess,3 endophthalmitis,2 spleen abscess,and other miscellaneous infections including 1 peritonitis,1 skin and soft tissue infection,1 myelitis,1 colitis,1 psoas major abscess and 1 myocardial abscess.Among the 140 cases,106 presented with single co-infection site,32 with 2 sites,and 2 with 3 sites.HvKP manifested high antibiotic susceptibility up to 80％ for most commonly used antibiotics.Capsule serotyping of 4,3 revived isolates indicated that K1 serotype accounted for 53.49％ (23/43),K2 34.88 (15/43),K54 2.33％ (1/43),K57 2.33％ (1/43),and other serotypes 6.98％(3/43).There was no significant distribution among K1,K2,K54,and K57 of hvKP capsule serotypes in patients with or without diabetes mellitus (P＞0.05).Multilocus sequence typing (MLST) suggested that ST23 and ST65 were predominant accounting for 39.53％ (17/4.3) and 25.58％ (11/4.3) respectively.No serotype or ST predominance was seen in any of the clinical infections.Conclusion HvKP is related to a wide spectrum of infectious diseases,including multiple extrahepatic sites and bloodstream infections besides CA-PLA with high antibiotic susceptibility.K1 and K2 are the predominant capsule serotypes,and ST 23 and ST65 are the predominant sequence types.

Clinical features of hypervirulent Klebsiella pneumoniae bloodstream infection / 中国感染控制杂志

Objective To understand the microbiological and clinical features of bloodstream infection(BSI) with high virulent Klebsiella pneumoniae(hvKP).Methods The strains and clinical data of 159 patients with Klebsiella pneumoniae (K.pneumoniae) BSI at the Second Hospital of Dalian Medical University from April 2013 to March 2016 were collected.Statistical analysis was performed using SPSS 19.0 software.Results 35.22％(56/159)of patients were with hvKP BSI,K1 and K2 serotypes in hvKP BSI accounted for 51.79％ and 26.79％ respectively.The main source of hvKP BSI was liver abscess(n =26,46.43 ％),the classic type of K.pneumoniae (cKP) BSI was primary bacteremia(n =41,39.81 ％).Difference in different types of infection between two groups of patients was statistically significant(x2 =57.782,P＜0.001),89.29 ％ of hvKP BSI was community-associated infection(CAI),and 73.79％ of cKP BSI was healthcare-associated infection(HAI).Difference in underlying diseases between two groups of patients was statistically significant(x2 =36.532,P＜0.001),50.00％ of hvKP BSI patients had diabetes,45.63％ of cKP BSI patients had malignant tumor.Icidence of septic shock in hvKP BSI patients was higher than that of cKP BSI patients(32.14％ vs 8.74％;x2 =14.096,P＜0.001).The proportion of ESBLs-producing of hvKP and cKP were 5.36％ (3/56)and 47.57％ (49/103)respectively,difference was statistically significant(x2 =29.375,P＜0.001).Klebsiella pneumoniae carbapemase(KPC)-producing hvKP was not found.Resistance rates of hvKP to ceftazidime,ceftriaxone,cefepime,aztreonam,gentamicin,levofloxacin,and compound sulfamethoxazole were all lower than cKP(all P＜0.05).Conclusion hvKP BSI is common in CAI,infection sources and underlying diseases are difference from cKP BSI,hvKP BSI is prone to cause septic shock.Both laboratories and clinicians should pay attention to hvKP infection and the change trend of antimicrobial resistance.

Diarreia causada por clostridium difficile: recentes avanços / Diarrhea caused by clostridium difficile: recent Advances

A infecção causada por Clostridium difficile (C. difficile), um dos agentes causadores de diarréia aguda e recorrente, tem como principal fator de risco o uso de antimicrobianos. Recentemente, houve um aumento da incidência e da mortalidade desta afecção. Clinicamente, a mesma pode manifestar-se desde um quadro de diarreia aquosa leve até a forma grave de colite pseudomembranosa. O objetivo deste artigo é apontar as mudanças epidemiológicas da infecção pelo C. difficile, além de rever fatores de risco, manifestações clínicas, métodos diagnósticos, tratamento e prevenção desta infecção. O aumento na gravidade da infecção causada pelo C. difficile é relacionado a uma nova cepa hipervirulenta, BI/NAPI/Ribotipo 027, que apresenta maior capacidade de produção de toxinas. Essa nova cepa, mais virulenta, ainda não foi detectada no Brasil, porém como já foi identificada em outros países da América, alerta para a preocupante capacidade de disseminação universal. Essa revisão é baseada em artigos publicados nos últimos 10 anos, utilizando como base de dados o PubMed e o Scielo (Scientific Eletronic Library Online), com as palavras-chave: Epidemiologia, diarreia, Clostridium difficile e cepa hipervirulenta.

Clostridium difficile (C. difficile) is a causative agent of diarrhea and its main risk factor is the use of antimicrobials. Recently, there was an increase in incidence and mortality. Clinical symptoms can manifest from mild watery diarrhea to severe pseudomembranous colitis. The purpose of this article is to make a literature review of C. difficile -associated diarrhea including its recent epidemiological changes. The increase in the severity of infection caused by Clostridium difficile was related to a new hypervirulent strain, BI/NAPI/ribotype 027, with greater capacity for production of toxins, responsible for clinical manifestations. This new strain, more virulent, has not yet been detected in Brazil, but it was already identified in other countries of America, warns the disturbing ability to universal dissemination. This review is based on articles published in the last 10 years, using as database PubMed and Scielo (Scientific Electronic Library Online), with the keywords: Epidemiology, diarrhea, Clostridium difficile and hypervirulent strain.

Neutrophil bactericidal activity assay for detecting the virulence of hypervirulent Klebsiella pneumoniae / 中华微生物学和免疫学杂志

Objective To evaluate the feasibility of using neutrophil bactericidal activity assay for analyzing the anti-bactericidal ability of hypervirulent Klebsiella pneumoniae ( hvKP) strains that harbored the virulence genes of rmpA and rmpA2 and were positive for string test .Methods A total of 150 non-duplicate blood-borne Klebsiella pneumoniae strains were collected from Zhejiang Province from January 2016 to July 2017.PCR was performed to detect carbapenem resistance genes (blaKPC, blaNDM, blaIMP-1, blaIMP-2), cap-sule genotypes (K1, K2, K5, K20, K54 and K57) and virulence genes (rmpA, rmpA2, iucA and iroN). Klebsiella pneumoniae strains that were positive for string test and harbored rmpA and rmpA2 genes were iden-tified as hvKP strains, while classic Klebsiella pneumoniae (cKP) strains were negative for string test, rmpA or rmpA2 gene.Neutrophil bactericidal activity assay was performed to analyze the virulence of Klebsiella pneumoniae strains and the survival rate was determined by using the following equation: the number of colony-forming units ( CFUs) in experimental group divided by the number of CFUs in control group .Re-sults Of the 150 Klebsiella pneumoniae strains, 43.3％ (65/150) harbored the rmpA2 gene and among them, strains positive for genes of rmpA, iroN and blaKPC and K2 respectively accounted for 73.8％, 80.0％, 75.4％and 40.0％.Twenty-four (36.9％) rmpA2 gene-positive strains showed positive result of string test.The survival rates of hvKP and cKP groups were respectively 0.866±0.056 and 0.368±0.058 and the difference between them was statistically significant (P<0.001).Conclusion Most of the hvKP strains that carry rmpA and rmpA2 genes and are positive for string test in Zhejiang Province survive the neu-trophil treatment , which indicates that the neutrophil bactericidal activity assay is an effective and simple method for identifying the virulence of Klebsiella pneumoniae.

Fidaxomicin - the new drug for Clostridium difficile infection.

Clostridium difficile is one of the many aetiological agents of antibiotic associated diarrhoea and is implicated in 15-25 per cent of the cases. The organism is also involved in the exacearbation of inflammatory bowel disease and extracolonic manifestations. Due to increase in the incidence of C. difficile infection (CDI), emergence of hypervirulent strains, and increased frequency of recurrence, the clinical management of the disease has become important. The management of CDI is based on disease severity, and current antibiotic treatment options are limited to vancomycin or metronidazole in the developing countries. this review article briefly describes important aspects of CDI, and the new drug, fidaxomicin, for its treatment. Fidaxomicin is particularly active against C.difficile and acts by inhibition of RNA synthesis. Clinical trials done to compare the efficacy and safety of fidaxomicin with that of vancomycin in treating CDI concluded that fidaxomicin was non-inferior to vancomycin for treatment of CDI and that there was a significant reduction in recurrences. The bactericidal properties of fidaxomicin make it an ideal alternative for CDI treatment. However, fidaxomicin use should be considered taking into account the potential benefits of the drug, along with the medical requirements of the patient, the risks of treatment and the high cost of fidaxomicin compared to other treatment regimens.

Necrotizing fasciitis and psoas abscess caused by hypervirulent Klebsiella pneumoniae / 대한내과학회지

A 62-year-old diabetic female was admitted to the hospital with fever and pain in both legs. Computed tomography scans of the abdomen revealed necrotizing fasciitis of the right thigh extending into the abdominal wall, and abscesses on the right psoas muscle. Magnetic resonance imaging showed increased T2 signal intensity along the peroneus muscle and fascia of the lower left leg. The patient received antibiotics and underwent debridement of the infected and necrotic tissue. Intra-abdominal abscesses were drained. Blood and pus cultures showed growth of Klebsiella pneumoniae, as had been suspected due to string test results showing hypermucoviscosity. Free-skin grafts were performed to repair tissue loss and the patient was subsequently discharged 82 days after admission. This represents the first reported case of necrotizing fasciitis and psoas muscle abscess caused by a hypervirulent strain of K. pneumoniae in Korea.

Necrotizing fasciitis and psoas abscess caused by hypervirulent Klebsiella pneumoniae / 대한내과학회지

A 62-year-old diabetic female was admitted to the hospital with fever and pain in both legs. Computed tomography scans of the abdomen revealed necrotizing fasciitis of the right thigh extending into the abdominal wall, and abscesses on the right psoas muscle. Magnetic resonance imaging showed increased T2 signal intensity along the peroneus muscle and fascia of the lower left leg. The patient received antibiotics and underwent debridement of the infected and necrotic tissue. Intra-abdominal abscesses were drained. Blood and pus cultures showed growth of Klebsiella pneumoniae, as had been suspected due to string test results showing hypermucoviscosity. Free-skin grafts were performed to repair tissue loss and the patient was subsequently discharged 82 days after admission. This represents the first reported case of necrotizing fasciitis and psoas muscle abscess caused by a hypervirulent strain of K. pneumoniae in Korea.