Whole genome analysis of echinocandin non-susceptible Candida Glabrata clinical isolates: a multi-center study in China.

BACKGROUND: Candida glabrata is an important cause of invasive candidiasis. Echinocandins are the first-line treatment of invasive candidiasis caused by C. glabrata. The epidemiological echinocandin sensitivity requires long-term surveillance and the understanding about whole genome characteristics of echinocandin non-susceptible isolates was limited. RESULTS: The present study investigated the echinocandin susceptibility of 1650 C. glabrata clinical isolates in China from August 2014 to July 2019. The in vitro activity of micafungin was significantly better than those of caspofungin and anidulafungin (P < 0.001), assessed by MIC50/90 values. Whole genome sequencing was conducted on non-susceptible isolates and geography-matched susceptible isolates. Thirteen isolates (0.79%) were resistant to at least one echinocandin. Six isolates (0.36%) were solely intermediate to caspofungin. Common evolutionary analysis of echinocandin-resistant and echinocandin-intermediate isolates revealed genes related with reduced caspofungin sensitivity, including previously identified sphinganine hydroxylase encoding gene SUR2. Genome-wide association study identified SNPs at subtelometric regions that were associated with echinocandin non-susceptibility. In-host evolution of echinocandin resistance of serial isolates revealed an enrichment for non-synonymous mutations in adhesins genes and loss of subtelometric regions containing adhesin genes. CONCLUSIONS: The echinocandins are highly active against C. glabrata in China with a resistant rate of 0.79%. Echinocandin non-susceptible isolates carried common evolved genes which are related with reduced caspofungin sensitivity. In-host evolution of C. glabrata accompanied intensive changing of adhesins profile.

Distribution and Antifungal Susceptibility of Candida Species Causing Candidemia in China: An Update From the CHIF-NET Study.

BACKGROUND: Candidemia is the most common, serious fungal infection and Candida antifungal resistance is a challenge. We report recent surveillance of candidemia in China. METHODS: The study encompassed 77 Chinese hospitals over 3 years. Identification of Candida species was by mass spectrometry and DNA sequencing. Antifungal susceptibility was determined using the Clinical and Laboratory Standards Institute broth microdilution method. RESULTS: In total, 4010 isolates were collected from candidemia patients. Although C. albicans was the most common species, non-albicans Candida species accounted for over two-thirds of isolates, predominated C. parapsilosis complex (27.1%), C. tropicalis (18.7%), and C. glabrata complex (12.0%). Most C. albicans and C. parapsilosis complex isolates were susceptible to all antifungal agents (resistance rate <5%). However, there was a decrease in voriconazole susceptibility to C. glabrata sensu stricto over the 3 years and fluconazole resistance rate in C. tropicalis tripled. Amongst less common Candida species, over one-third of C. pelliculosa isolates were coresistant to fluconazole and 5-flucytocine, and >56% of C. haemulonii isolates were multidrug resistance. CONCLUSIONS: Non-albicans Candida species are the predominant cause of candidemia in China. Azole resistance is notable amongst C. tropicalis and C. glabrata. Coresistance and multidrug resistance has emerged in less common Candida species.

In Vitro Activity of Imipenem/Relebactam Against Enterobacteriaceae Isolates Obtained from Intra-abdominal, Respiratory Tract, and Urinary Tract Infections in China: Study for Monitoring Antimicrobial Resistance Trends (SMART), 2015-2018.

BACKGROUND: Considering the increasing incidence of carbapenem-resistant Enterobacteriaceae in China, this study aimed to establish the in vitro effectiveness of imipenem/relebactam (IMI/REL) on clinical Enterobacteriaceae isolates derived from intra-abdominal infections (IAIs), respiratory tract infections (RTIs), and urinary tract infections (UTIs) in China between 2015 and 2018. METHODS: In total, 8781 Enterobacteriaceae isolates from IAI, RTI, and UTI samples were collected from 22 hospitals across 7 geographic regions of China. Susceptibility to antimicrobial drugs was tested using the Clinical and Laboratory Standards Institute broth microdilution and breakpoints, and IMI/REL activity was assessed using United States Food and Drug Administration guidelines. RESULTS: In 2015-2018, the most frequently identified Enterobacteriaceae species was Escherichia coli (n = 4676 [53.3%]), followed by Klebsiella pneumoniae (n = 2949 [33.6%]) and Enterobacter cloacae (n = 542 [6.2%]). The Enterobacteriaceae isolates showed 95.2% overall susceptibility to IMI/REL, of which the susceptibility rates in isolates from IAI, RTI, and UTI were 95.8%, 91.4%, and 96.6%, respectively. Overall, the susceptibilities of both intensive care unit (ICU) and non-ICU Enterobacteriaceae isolates to colistin were 92.9%, followed by IMI/REL (90.7% [95.9%]) and amikacin (83.3% [92.3%]). In addition, IMI/REL restored 66.3% susceptibility in imipenem-nonsusceptible Enterobacteriaceae. CONCLUSIONS: Given their high in vitro susceptibility, Enterobacteriaceae infections in China should be considered for IMI/REL treatment, especially with isolates that are not susceptible to carbapenems.

Investigation of Virulence Genes and Resistance Genes in a Group of Staphylococcus aureus Isolated in Yuhang, China.

BACKGROUND: To investigate the distribution of virulence genes and resistance genes in a group of Staphylococcus aureus (S. aureus). METHODS: From February 2013 to April 2014, a total of 39 strains of S. aureus were collected at Hangzhou Yuhang Hospital of Traditional Chinese Medicine, China. Drug sensitivity to 16 kinds of antimicrobial agents was performed by E-test method. A total of 94 virulence genes and 11 resistance genes, including qacA and bsa, were examined by PCR. All virulence and resistance genes were used as molecular markers to perform sample cluster analysis (UPGMA). RESULTS: At least one gene in every class of virulence genes were positive in strains of S. aureus: adherence, exoenzyme, host immune evasion, and toxin. Eleven virulence genes encoding adherence were positive: clfA, clfB, ebpS, fnbA, icaA, isdA, isdB, isdC, sdrC, sdrD, sdrE; 5 virulence genes encoding exoenzyme were positive: hysA, lip, splB, edinB, nuc; 2 virulence genes encoding host immune evasion were positive: cap5, cap8; 55 kinds of virulence genes encoding toxin were positive: hla, hlb, hlg-2, psm-mec, pvl, sea, seb, sec, sed, see, seg, sei, sek, sel, sem, sen, seo, seq, tst, set1, set2, set3, set4, set5, set6, set7, set8, set9, set10, set11, set12, set13, set14, set15, set16, set17, set18, set19, set20, set21, set22, set24, set25, set26, set30 , set31, set32, set33, set34, set35, set36, set38, set39, set40, lukE. In addition, 39 strains of S. aureus were 100.0% susceptible to quinupristin/dalfopristin, rifampin, vancomycin, tigecycline, and had some resistance rates to 12 other kinds of antimicrobial agents. Six resistance genes were positive: mecA (53.8%), aac6'/aph2" (33.3%), aph3'-III (12.8%), ant4'/ant44" (23.1%), qacA (30.8%), bsa (12.8%). Sample cluster analysis suggested that this group of S. aureus were divided into cluster A and B, and presented a clearly aggregation. CONCLUSIONS: A great number of virulence genes were positive in this group of S. aureus, contributing to colonization and survival in the host, evading the host immune system, delivering toxins to the host, and promoting pathogenicities. This group of S. aureus also had high resistance, carried some kinds of resistance genes, and had clustering. The implementation of disinfection measures should be strengthened to prevent the occurrence of nosocomial infection.

Endogenous endophthalmitis caused by a multidrug-resistant hypervirulent Klebsiella pneumoniae strain belonging to a novel single locus variant of ST23: first case report in China.

BACKGROUND: Endogenous endophthalmitis caused by hypervirulent Klebsiella pneumoniae (HVKP) is an emerging infectious disease commonly with a devastating visual outcome. Most HVKP strains display a wild-type susceptibility profile to antibiotics. However, reports of antimicrobial-resistant HVKP have increased over time, which poses a serious therapeutic dilemma. CASE PRESENTATION: A 25-year-old man with a liver abscess and poorly controlled diabetes mellitus was admitted for endophthalmitis due to K. pneumoniae. The isolate displayed hypermucoviscosity as determined by a positive string test and exhibited resistance to ceftazidime, piperacillin-tazobactam and amikacin. Whole genome sequencing (WGS) analysis demonstrated the isolate to be a K1-serotype strain and belong to a novel single locus variant of ST23, ST2922. In addition to the virulence genes linked to HVKP, rmpA, magA, iucABCDiutA (aerobactin), ybtAPSTUX (yersiniabactin) and iroBDN (salmochelin), it was found to harbor extended-spectrum ß-lactamase (ESBL) gene (blaCTX-M-14), AmpC ß-lactamase gene (blaDHA), and 16S rRNA methylase gene (armA). CONCLUSIONS: This is the first known case of endogenous endophthalmitis caused by a multidrug-resistant HVKP strain ever reported in China. Early diagnosis and treatment with intravenous and intravitreal injection of carbapenem were essential for a favorable visual outcome.

Bloodstream infections caused by Klebsiella pneumoniae: prevalence of blaKPC, virulence factors and their impacts on clinical outcome.

BACKGROUND: Klebsiella pneumoniae bloodstream infections (BSIs) occur with significant prevalence and high mortality worldwide. Antimicrobial resistance and virulence are two main factors participating in the pathogenicity of K. pneumoniae. Here we investigated the prevalence of blaKPC and virulence factors in K. pneumoniae isolated from patients with BSIs and their association with clinical outcome. METHODS: The clinical data of 285 K. pneumoniae BSI cases diagnosed from January 2013 to December 2015 in a Chinese university hospital were retrospectively evaluated. The "string test" was performed to identify hypermucoviscous K. pneumoniae (HMKP). blaKPC, rmpA, magA and serotype-specific genes were detected by PCR amplification. Finally, a Cox proportional hazards model was employed to determine the predictors of 14-day mortality. RESULTS: Of these isolates, the prevalence of blaKPC and rmpA were 33.3% (95/285) and 31.6% (90/285) respectively. 69 isolates (24.2%, 69/285) were HMKP. rmpA was strongly associated with HM phenotype. The KPC-producing KP and HMKP were almost non-overlapping and only three HMKP isolates harbored blaKPC. K1 (28, 40.6%) and K2 (22, 31.9%) were the most common serotypes in HMKP. 44.9% of HMKP BSIs had origin of biliary tract infection or liver abscess. The 14-day mortality was 100% in blaKPC+/HM+ subgroup (3/3), followed by blaKPC+/HM- (39/92, 42.4%), blaKPC-/HM+ (5/66, 7.6%) and blaKPC-/HM- (7/124, 5.6%). The 14-day cumulative survival was significantly different between blaKPC+ and blaKPC- subgroup (Log-rank p < 0.001) but almost equal between blaKPC-/HM+ and blaKPC-/HM- subgroup (Log-rank p = 0.578) under the condition of comparable illness severity between blaKPC-/HM+ and blaKPC-/HM- subgroup. Independent risk factors for 14-day mortality were Pitt bacteremia score (HR 1.24, CI 95% 1.13-1.36, p < 0.001), Charlson comorbidity index (HR 1.24, CI 95% 1.09-1.41, p = 0.001), septic shock (HR 2.61, CI 95% 1.28-5.35, p = 0.009) and blaKPC (HR 2.20, CI 95% 1.06-4.54, p = 0.034). CONCLUSIONS: Most of HMKP were antibiotic-susceptible and people infected received appropriate antimicrobial therapy, which may explain the favorable outcome of HMKP BSIs. The KPC-producing HMKP BSIs were scarce but life-threatening. blaKPC was valuable in predicting 14-day mortality.

Carbapenem susceptibilities of Gram-negative pathogens in intra-abdominal and urinary tract infections: updated report of SMART 2015 in China.

BACKGROUND: To evaluate the susceptibility rates of aerobic and facultative Gram-negative bacterial isolates from Chinese intra-abdominal infections (IAI) and urinary tract infections (UTI) focusing on carbapenems and comparing their effectiveness between 2014 and 2015. METHODS: A total of 2318 strains in 2015 (1483 from IAI and 835 from UTI) and 2374 strains in 2014 (1438 from IAI and 936 from UTI) were included in the analysis. Antimicrobial susceptibilities were determined at a central laboratory using CLSI broth microdilution and interpretive standards. Hospital acquired (HA) IAI and UTI were defined as isolates sampled > 48 h and community acquired (CA) as isolates sampled < 48 h after admission. RESULTS: The main species derived from IAI and UTI in 2015 were Escherichia coli (50.86%) and Klebsiella pneumoniae (19.20%). Susceptibilities of Escherichia coli IAI and UTI strains to imipenem (IPM) and ertapenem (ETP) were > 90% in 2014 and 2015, while the susceptibilities to IPM and ETP of Klebsiella pneumoniae IAI strains were >  80% in 2014 but dropped to ≤80% in 2015 for UTI strains. Susceptibilities of IAI Enterobacteriaceae strains to IPM and ETP in 2015 were lowest in the colon and abscesses, and Enterobacteriaceae susceptibilities of UTI and IAI isolates to IPM and ETP were lowest in medical, pediatric and surgery intensive care units (ICUs) in 2015. CONCLUSIONS: IPM and ETP were effective in vitro against Enterobacteriaceae isolated from IAIs and UTIs in 2014 and 2015, but susceptibility to carbapenems in UTIs markedly decreased in 2015.

Pyogenic liver abscess related to intrahepatic bile duct stones: Difficulties in infectious control and diagnosis of concomitant cholangiocarcinoma.

BACKGROUND AND AIM: Cholangitis, bacteremia, and pyogenic liver abscess (PLA) can be often caused by intrahepatic bile ducts stone (IBDS), which is endemic to South-East Asia. The association between IBDS and cholangiocarcinoma has been well recognized. Concomitant cholangiocarcinoma in the PLA related to IBDS is often missed. METHODS: A case-control study consisting of 64 patients with PLA related to IBDS and 256 control patients with PLA not related to IBDS was used to investigate clinical features of PLA and incidence of concomitant cholangiocarcinoma in patients with PLA related to IBDS. RESULTS: The main imaging manifestations of PLA related to IBDS was cystic-solid lesions and solid lesions. Of seven patients (10.9%) with pathology-proven cholangiocarcinoma in the same area of PLA related to IBDS among 64 patients, only two patients were initially diagnosed as having concomitant cholangiocarcinoma by biopsy, and other five patients diagnosed as acute inflammatory lesion. Within 60 days after onset, the infection-related death rate and recurrence rate in patients with PLA related to IBDS were 12.9% and 20.3%, respectively, whereas in patients with PLA not related to IBDS were 3.9% and 3.1%, respectively. Only 25% of patients with PLA related to IBDS underwent surgery after admission. The main pathogens in PLA patients related to IBDS were Escherichia coli and extended-spectrum beta-lactamase-producing Enterobacteriaceae. CONCLUSIONS: The imaging manifestations of PLA related to IBDS often present cystic-solid or solid lesions. PLA related to IBDS is characterized by high rate of recurrence and infection-related death, difficulty in diagnosis of concomitant cholangicarcinoma.

Biliary diseases as main causes of pyogenic liver abscess caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae.

BACKGROUND & AIMS: Little is known about aetiology and morbidity and clinical characteristics of pyogenic liver abscess caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae. METHODS: An analysis between pyogenic liver abscess patients caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae isolates and those caused by non-extended-spectrum beta-lactamase-producing Enterobacteriaceae was performed. RESULTS: Among 817 pyogenic liver abscess patients, there were 176 patients (21.5%) with pyogenic liver abscess of biliary origin, and 67 pyogenic liver abscess patients (8.2%) caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae isolates (mainly Escherichia coli and Klebsiella pneumoniae). Of 176 pyogenic liver abscess patients related to biliary disorders, there were 48 pyogenic liver abscess patients (27.3%) caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae. Within 67 pyogenic liver abscess patients caused by Enterobacteriaceae expressing extended-spectrum beta-lactamases, the occurrences of 48 pyogenic liver abscess patients (71.6%) were associated with biliary disorders. When compared with pyogenic liver abscess patients caused by non-extended-spectrum beta-lactamase-producing Enterobacteriaceae, there were significantly greater incidences of polymicrobial infections, bacteremia, pulmonary infection, recurrence and death in pyogenic liver abscess patients caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae. Carbapenems remain mainstay drugs against extended-spectrum beta-lactamase-producing E. coli and K. pneumoniae. Independent risk factors for occurrence of pyogenic liver abscess caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae were biliary disorders including extra- and intrahepatic cholangiolithiasis and an abnormal bilioenteric communication between bile and gut, a treatment history of malignancy such as operation and chemotherapy, pulmonary infection, and diabetes mellitus. CONCLUSIONS: Pyogenic liver abscess caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae isolates mainly occurs in patients with biliary disorders or with a treatment history of malignancy. The mainstay of treatment remains carbapenems in combination with adequate aspiration or drainage.

Antimicrobial susceptibilities of aerobic and facultative gram-negative bacilli isolated from Chinese patients with urinary tract infections between 2010 and 2014.

BACKGROUND: The objective of this study was to investigate the distribution and susceptibility of aerobic and facultative Gram-negative bacilli isolated from Chinese patients with UTIs collected within 48 h (community acquired, CA) or after 48 h (hospital acquired, HA) of hospital admission. METHODS: From 2010 to 2014, the minimum inhibitory concentrations (MICs) of 12 antibiotics for 4,332 aerobic and facultative Gram-negative bacilli, sampled in 21 hospitals in 16 cities, were determined by the broth microdilution method. RESULTS: Enterobacteriaceae composed 88.5% of the total isolates, with Escherichia coli (E. coli) (63.2%) the most commonly isolated species, followed by Klebsiella pneumoniae (K. pneumoniae) (12.2%). Non-Enterobacteriaceae accounted for only 11.5% of all isolates and included mainly Pseudomonas aeruginosa (P. aeruginosa) (6.9%) and Acinetobacter baumannii (A. baumannii) (3.3%). Among the antimicrobial agents tested, the susceptibility rates of E.coli to the two carbapenems, ertapenem and imipenem as well as amikacin and piperacillin-tazobactam ranged from 92.5 to 98.7%. Against K. pneumonia, the most potent antibiotics were imipenem (92.6% susceptibility), amikacin (89.2% susceptibility) and ertapenem (87.9% susceptibility). Although non-Enterobacteriaceae did not show high susceptibilities to the 12 common antibiotics, amikacin exhibited the highest in vitro activity against P. aeruginosa over the 5-year study period, followed by piperacillin-tazobactam, imipenem, ceftazidime, cefepime, ciprofloxacin, and levofloxacin. The Extended Spectrum Beta-Lactamase (ESBL) rates decreased slowly during the 5 years in E. coli from 68.6% in 2010 to 59.1% in 2014, in K. pneumoniae from 59.7 to 49.2%, and in Proteus mirabilis (P. mirabilis) from 40.0 to 26.1%. However, the ESBL rates were different in 5 regions of China (Northeast, North, East, South and Middle-China). CONCLUSION: E. coli and K. pneumonia were the major pathogens causing UTIs and carbapenems and amikacin retained the highest susceptibility rates over the 5-year study period, indicating that they are good drug choices for empirical therapies, particularly of CA UTIs in China.

Update of incidence and antimicrobial susceptibility trends of Escherichia coli and Klebsiella pneumoniae isolates from Chinese intra-abdominal infection patients.

BACKGROUND: To evaluate in vitro susceptibilities of aerobic and facultative Gram-negative bacterial (GNB) isolates from intra-abdominal infections (IAIs) to 12 selected antimicrobials in Chinese hospitals from 2012 to 2014. METHODS: Hospital acquired (HA) and community acquired (CA) IAIs were collected from 21 centers in 16 Chinese cities. Extended spectrum beta-lactamase (ESBL) status and antimicrobial susceptibilities were determined at a central laboratory using CLSI broth microdilution and interpretive standards. RESULTS: From all isolated strains the Enterobacteriaceae (81.1%) Escherichia coli accounted for 45.4% and Klebsiella pneumoniae for 20.1%, followed by Enterobacter cloacae (5.2%), Proteus mirabilis (2.1%), Citrobacter freundii (1.8%), Enterobacter aerogenes (1.8%), Klebsiella oxytoca (1.4%), Morganella morganii (1.2%), Serratia marcescens (0.7%), Citrobacter koseri (0.3%), Proteus vulgaris (0.3%) and others (1.0%). Non- Enterobacteriaceae (18.9%) included Pseudomonas aeruginosa (9.8%), Acinetobacter baumannii (6.7%), Stenotrophomonas maltophilia (0.9%), Aeromonas hydrophila (0.4%) and others (1.1%). ESBL-screen positive Escherichia coli isolates (ESBL+) showed a decreasing trend from 67.5% in 2012 to 58.9% in 2014 of all Escherichia coli isolates and the percentage of ESBL+ Klebsiella pneumoniae isolates also decreased from 2012 through 2014 (40.4% to 26.6%), which was due to reduced percentages of ESBL+ isolates in HA IAIs for both bacteria. The overall susceptibilities of all 5160 IAI isolates were 87.53% to amikacin (AMK), 78.12% to piperacillin-tazobactam (TZP) 81.41% to imipenem (IMP) and 73.12% to ertapenem (ETP). The susceptibility of ESBL-screen positive Escherichia coli strains was 96.77%-98.8% to IPM, 91.26%-93.16% to ETP, 89.48%-92.75% to AMK and 84.86%-89.34% to TZP, while ESBL-screen positive Klebsiella pneumoniae strains were 70.56%-80.15% susceptible to ETP, 80.0%-87.5% to IPM, 83.82%-87.06% to AMK and 63.53%-68.38% to TZP within the three year study. Susceptibilities to all cephalosporins and fluoroquinolones were less than 50% beside 66.5% and 56.07% to cefoxitin (FOX) for ESBL+ Escherichia coli and Klebsiella pneumoniae strains respectively. CONCLUSIONS: The total ESBL+ rates decreased in Escherichia coli and Klebsiella pneumoniae IAI isolates due to fewer prevalence in HA infections. IPM, ETP and AMK were the most effective antimicrobials against ESBL+ Escherichia coli and Klebsiella pneumoniae IAI isolates in 2012-2014 and a change of fluoroquinolone regimens for Chinese IAIs is recommended.

Antimicrobial Susceptibilities of Aerobic and Facultative Gram-Negative Bacilli from Intra-abdominal Infections in Patients from Seven Regions in China in 2012 and 2013.

To evaluate the antimicrobial susceptibility of Gram-negative bacilli that caused hospital-acquired and community-acquired intra-abdominal infections (IAIs) in China between 2012 and 2013, we determined the susceptibilities to 12 antimicrobials and the extended-spectrum ß-lactamase (ESBL) statuses of 3,540 IAI isolates from seven geographic areas in China in a central laboratory using CLSI broth microdilution and interpretive standards. Most infections were caused by Escherichia coli (46.3%) and Klebsiella pneumoniae (19.7%). Rates of ESBL-producing E. coli (P = 0.031), K. pneumoniae (P = 0.017), and Proteus mirabilis (P = 0.004) were higher in hospital-acquired IAIs than in community-acquired IAIs. Susceptibilities of enterobacteriaceae to ertapenem, amikacin, piperacillin-tazobactam, and imipenem were 71.3% to 100%, 81.3% to 100%, 64.7% to 100%, and 83.1% to 100%, respectively, but imipenem was ineffective against P. mirabilis (<20%). Although most ESBL-positive hospital-acquired isolates were resistant to third- and fourth-generation cephalosporins, the majority were susceptible to cefoxitin (47.9% to 83.9%). Susceptibilities of ESBL-positive isolates to ampicillin-sulbactam (<10%) were low, whereas susceptibilities to ciprofloxacin (0% to 54.6%) and levofloxacin (0% to 63.6%) varied substantially. The prevalences of cephalosporin-susceptible E. coli and K. pneumoniae were higher in the northeastern and southern regions than in the central and eastern regions, reflecting the ESBL-positive rates in these areas, and were lowest in the Jiangsu-Zhejiang (Jiang-Zhe) area where the rates of carbapenem resistance were also highest. Ertapenem, amikacin, piperacillin-tazobactam, and imipenem are the most efficacious antibiotics for treating IAIs in China, especially those caused by E. coli or K. pneumoniae. Resistance to cephalosporins and carbapenems is more common in the Jiang-Zhe area than in other regions in China.

Current perspectivesin pathogenesis and antimicrobial resistance of enteroaggregative Escherichia coli.

Enteroaggregative Escherichia coli (EAEC) is an emerging pathogen that causes acute and persistent diarrhea in children and adults. While the pathogenic mechanisms of EAEC intestinal colonization have been uncovered (including bacterial adhesion, enterotoxin and cytotoxin secretion, and stimulation of mucosal inflammation), those of severe extraintestinal infections remain largely unknown. The recent emergence of multidrug resistant EAEC represents an alarming public health threat and clinical challenge, and research on the molecular mechanisms of resistance is urgently needed.

Rapid identification and antimicrobial susceptibility testing directly from blood cultures of gram-negative and gram-positive isolates.

BACKGROUND: Bloodstream infection is still an important cause for morbidity and mortality. In order to reduce the turnaround time for laboratory diagnosis of bacteremia, the efficacy of identification and antimicrobial susceptibility testing using samples taken directly from positive culture bottles by Vitek 2 compact and Kirby-Bauer disk diffusion method was evaluated. METHODS: A total of 218 monomicrobial blood cultures, including 81 Gram-negative and 137 Gram-positive isolates, were detected by a direct (that is, the organism was taken from the positive blood culture bottle) and standardized (taken from the overnight agar medium subculture) method on Vitek 2 compact ID cards for identification and Kirby-Bauer disk diffusion method for antimicrobial susceptibility testing. RESULTS: 79 of 81 Gram-negative rods (97.5%) and 84 of 137 Gram-positive cocci (61.3%) were correctly identified to the species level. Among 41 strains of wrongly identified Gram-positive cocci, 30 strains (73.2%) were misidentified as Kocuria. For antimicrobial susceptibility testing, the direct method had an overall error rate of 2.1% for Gram-negative rods, with 0.1% very major, 0.4% major, and 1.6% minor discrepancies compared with the standard method. The overall error rate for Gram-positive cocci was 4.4%, with 0.2% very major, 1.3% major, and 2.9% minor discrepancies. CONCLUSIONS: Direct identification and antibiotic susceptibility testing with samples taken directly from blood cultures provided excellent results for Gram-negative rods and decreased turnaround time, while it would be less reliable for identification of Gram-positive cocci, although their antibiotic susceptibility testing yielded very good results.

Blood bacterial resistant investigation collaborative system (BRICS) report: a national surveillance in China from 2014 to 2019.

BACKGROUND: In this first national bloodstream infection (BSI) surveillance program in China, we assessed the composition of pathogenic bacteria and the trends for antimicrobial susceptibility over a 6-year period in China. METHODS: Blood bacterial isolates from patients at hospitals participating in the Blood Bacterial Resistant Investigation Collaborative System (BRICS) were collected from January 2014 to December 2019. Only the first isolate of a species per patient was eligible over the full study period. Antibiotic-susceptibility testing was conducted by agar-dilution or broth-dilution methods as recommended by the Clinical and Laboratory Standards Institute (CLSI). WHONET 5.6 was used to analyze data. RESULTS: During the study period, 27,899 bacterial strains were collected. Gram-positive organisms accounted for 29.5% (8244) of the species identified and Gram-negative organisms accounted for 70.5% (19,655). The most-commonly isolated organisms in blood cultures were Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, coagulase-negative Staphylococci, and Acinetobacter baumannii. The prevalence of multidrug-resistant organisms, such as E. coli, K. pneumoniae, A. baumannii was higher in tertiary hospitals, whereas extended-spectrum, ß-lactamase-producing E. coli (ESBL-E. coli), carbapenem-resistant A. baumannii were more prevalent in economically-developing areas. The prevalence of methicillin-resistant S. aureus declined from 39.0% (73/187) in 2014 to 25.9% (230/889) in 2019 (p < 0.05). The prevalence of ESBL-E. coli dropped from 61.2% (412/673) to 51.0% (1878/3,683) over time (p < 0.05), and carbapenem-resistant E. coli remained low prevalence (< 2%; 145/9944; p = 0.397). In contrast, carbapenem-resistant K. pneumoniae increased markedly from 7.0% (16/229) in 2014 to 19.6% (325/1,655) in 2019 (p < 0.05). CONCLUSION: E. coli and K. pneumoniae were the leading causes of BSI during the 6-year study period. The major resistant pathogens declined or remained stable, whereas carbapenem-resistant K. pneumoniae continued to increase, which poses a great therapeutic challenge for BSIs.

Emergence of transferable ceftazidime-avibactam resistance in KPC-producing Klebsiella pneumoniae due to a novel CMY AmpC ß-lactamase in China.

OBJECTIVES: To evaluate the molecular mechanisms of ceftazidime/avibactam (CAZ/AVI) resistance in six Klebsiella pneumoniae strains that co-produce K. pneumoniae carbapenemase (KPC)-2 and a novel variant of CMY cephalosporinase in a Chinese hospital. METHODS: Antimicrobial susceptibility was determined by broth microdilution. Whole-genome sequencing (WGS) was performed to investigate potential resistance determinants. Plasmid conjugation, electroporation, S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) hybridization and cloning experiment were carried out to investigate the resistance plasmids and genes. RESULTS: A high level of CAZ/AVI resistance was observed in six KPC-Kp strains (MIC 128 mg/L). Five strains were isolated in 2015 and one in 2016, before the approval of CAZ/AVI in China. Sequence analysis indicated that all the strains belonged to sequence type (ST) 11 and uniformly carried a novel CMY AmpC ß-lactamase gene, designated blaCMY-172. When compared with CMY-2, CMY-172 has a deletion of three consecutive amino acids (K290, V291 and A292) in the R2-loop region and a non-synonymous amino acid substitution at position 346 (N346I). The blaCMY-172-bearing plasmid, pKPCZA02_4, was 93.3 Kb, IncI1-I type, and conjugative; blaCMY-172 was located in an IS1294-mediated transposon. Plasmid conjugation and DNA fragment cloning proved that blaCMY-172 was responsible for CAZ/AVI resistance. CONCLUSIONS: Our study identified conjugative plasmid-mediated blaCMY-172 as a new mechanism for CAZ/AVI resistance in clinical KPC-Kp strains. Careful monitoring of CAZ/AVI susceptibility is imperative for preventing the spread of the resistance gene.

Dynamic variations in the peripheral blood lymphocyte subgroups of patients with 2009 pandemic H1N1 swine-origin influenza A virus infection.

BACKGROUND: Novel Influenza A (H1N1) is an acute respiratory infectious disease. Animal experiments indicated that when H1N1 virus infected early hosts, it showed strong CD4(+), CD8(+), and CD4(+)CD25(+) T cell reactions. The aim of this study was to investigate the dynamic fluctuations of the peripheral blood lymphocyte subgroups in patients infected with H1N1 swine-origin influenza A virus (S-OIV). METHODS: The frequency of T cells, B cells, natural killer (NK) cells, and regulatory T cells (Treg) in 36 severe H1N1 and 40 moderate H1N1 patients were detected at different periods by flow cytometry. In parallel, serum cytokines were detected by enzyme-linked immunosorbent assay and C-reactive protein (CRP) was analyzed through an image-type automatic biochemical analyzer. In addition, 20 healthy volunteers, who were not infected with 2009 H1N1 virus, were selected as controls. RESULTS: The frequency of NK cells were decreased in all cases and CD19(+) B cells were increased in severe cases than those of the controls. At 1-2d from onset, the frequency of CD4(+) and CD4(+)CD25(+) T cells in moderate cases was higher than in the severe cases. Serum cytokines, specifically IL-2, IL-4, IL-6, IL-10, and IFN-γ exhibited no significant change both in the moderate and the severe cases during the whole monitoring process. In the early stage of the disease, serum CRP levels in the severe and moderate groups were significantly higher than that in the control group. CONCLUSIONS: Patients showed different lymphocyte subgroup distributions between mild and severe cases, which might affect the incidence and development of 2009 H1N1.

Continual Decline in Azole Susceptibility Rates in Candida tropicalis Over a 9-Year Period in China.

BACKGROUND: There have been reports of increasing azole resistance in Candida tropicalis, especially in the Asia-Pacific region. Here we report on the epidemiology and antifungal susceptibility of C. tropicalis causing invasive candidiasis in China, from a 9-year surveillance study. METHODS: From August 2009 to July 2018, C. tropicalis isolates (n = 3702) were collected from 87 hospitals across China. Species identification was carried out by mass spectrometry or rDNA sequencing. Antifungal susceptibility was determined by Clinical and Laboratory Standards Institute disk diffusion (CHIF-NET10-14, n = 1510) or Sensititre YeastOne (CHIF-NET15-18, n = 2192) methods. RESULTS: Overall, 22.2% (823/3702) of the isolates were resistant to fluconazole, with 90.4% (744/823) being cross-resistant to voriconazole. In addition, 16.9 (370/2192) and 71.7% (1572/2192) of the isolates were of non-wild-type phenotype to itraconazole and posaconazole, respectively. Over the 9 years of surveillance, the fluconazole resistance rate continued to increase, rising from 5.7 (7/122) to 31.8% (236/741), while that for voriconazole was almost the same, rising from 5.7 (7/122) to 29.1% (216/741), with no significant statistical differences across the geographic regions. However, significant difference in fluconazole resistance rate was noted between isolates cultured from blood (27.2%, 489/1799) and those from non-blood (17.6%, 334/1903) specimens (P-value < 0.05), and amongst isolates collected from medical wards (28.1%, 312/1110) versus intensive care units (19.6%, 214/1092) and surgical wards (17.9%, 194/1086) (Bonferroni adjusted P-value < 0.05). Although echinocandin resistance remained low (0.8%, 18/2192) during the surveillance period, it was observed in most administrative regions, and one-third (6/18) of these isolates were simultaneously resistant to fluconazole. CONCLUSION: The continual decrease in the rate of azole susceptibility among C. tropicalis strains has become a nationwide challenge in China, and the emergence of multi-drug resistance could pose further threats. These phenomena call for effective efforts in future interventions.

Secondary Bacterial Infections in Critical Ill Patients With Coronavirus Disease 2019.

Secondary bacterial infections occurred in 13.9% (5 of 36) of critical ill patients with coronavirus disease 2019. All 5 patients had been admitted to intensive care unit and received mechanical ventilation before developing bacterial infection. Active surveillance of culture should be performed for critically ill patients. Prevention of nosocomial infection should to be taken seriously.