Dissemination and characteristics of carbapenem-resistant Klebsiella pneumoniae in nine district hospitals in southwestern China.

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKP) is epidemically transmitted globally, but few studies focused on the prevalence in district-level hospitals. In this study, we investigated CRKP strains collected from nine district hospitals from September 2019 to September 2020, aiming to determine the resistance mechanisms, virulence profiles, and molecular epidemiological characteristics of CRKP in district hospitals in Southwest China. Methods: A total of 51 CRKP strains were collected from 9 district-level hospitals. Matrix-assisted laser desorption/ionization-time of flight mass spectrometer was used for strain identification review, and the micro-broth dilution method was used for antibiotic sensitivity detection. Molecular epidemiological investigation of strains was performed by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) methods. PCR and efflux pump inhibition tests were used to detect CRKP resistance mechanisms. PCR and serum killing tests were used to detect capsular serotype, virulence-related genes, and virulence validation. Results: The CRKP strains in district hospitals presented high levels of MIC50 and MIC90 in carbapenem antibiotics especially ertapenem and meropenem. A total of 90.2% (46/51) CRKP strains were detected as carbapenemase producers, and the proportion of strains co-expressing carbapenemases was 11.8% (6/51). All CRKP strains were grouped into eight MLST types, and ST11 was the most prevalent genotype. A total of 11.8% (6/51) CRKP isolates were positive for the string test, and three strains of hypervirulent and carbapenem-resistant K. pneumoniae (HV-CRKP) were positive in serum killing test. The molecular typing of all the CRKP isolates was grouped into 29 different PFGE patterns, and 40 ST11 isolates belonged to 20 different PFGE clusters. Conclusion: CRKP strains showed high-level antibiotic resistance and virulence phenotype in district hospitals in Southwest China, which suggested that we should immediately pay attention to the rapid dissemination of the CRKP in regional hospitals. Our study will provide new insights into the epidemiology of CRKP in regional hospitals, which will help regional hospitals develop nosocomial infection prevention and control policies tailored to local conditions.

Inactivation of Clinically Frequently Used Antimicrobial Agents By BacT/ALERT FAN Plus and BACTEC Aerobic and Anaerobic Culture Media in Simulated Blood Cultures: First Comparative Evaluation in China Mainland.

PURPOSE: To evaluate the antimicrobial inactivation capabilities of BacT/ALERT (FA Plus and FN Plus) and BACTEC (Plus Aerobic/F and Lytic/10 Anaerobic/F) media. PATIENTS AND METHODS: The inactivation capabilities of the commercial blood culture media were compared using 21 microorganism-antimicrobial combinations in simulated adult blood cultures. RESULTS: BacT/ALERT culture media demonstrated higher detection rates than the BACTEC culture media. The recovery rates of the aerobic bottles were 74/115 (64.3%) for FA Plus bottles and 64/115 (55.7%) for BACTEC Aerobic Plus bottles. The BacT/ALERT FAN Plus culture media exhibited a shorter time to detection (TTD). The TTD of FA Plus media was 14.7 h, 4.85 h shorter than the BACTEC Aerobic media (19.55 h), while the TTDs of FN Plus media and BACTEC Anaerobic media were 16.8 h and 18.4 h, respectively. CONCLUSION: BacT/ALERT (FA Plus and FN Plus) media showed relative, but not absolute, advantages, as it had higher detection rates and shorter TTD and thus can be selectively applied to patients with prior use of antimicrobial agents before blood culture samples are taken.

Epidemiology and risk factors of rectal colonization of carbapenemase-producing Enterobacteriaceae among high-risk patients from ICU and HSCT wards in a university hospital.

BACKGROUND: Nosocomial carbapenemase-producing Enterobacterieceae (CPE) infections constitute a major global health concern and are associated with increased morbidity and mortality. Rectal colonization with CPE is a risk factor for bacterial translocation leading to subsequent endogenous CPE infections. This prospective observational study was aimed to investigate the prevalence and epidemiology of rectal colonization of CPE, the carbapenemase genotypes, and to identify the independent risk factors for the acquisition of CPE colonization in high-risk patients from ICU and HSCT wards in a university hospital in China. METHODS: In a prospective cohort study, 150 fecal samples from rectal swabs were consecutively obtained for inpatients from the intensive care unit (ICU) and hematopoietic stem cell transplantation (HSCT) wards from November 2018 to May 2019, and screening test for CPE was conducted by using prepared in-house trypsin soybean broth (TSB) selective media and MacConkey agar. Antimicrobial susceptibility was determined by the broth microdilution method and carbapenemase genes were characterized by both the GeneXpert Carba-R and PCR for blaKPC, blaNDM, blaIMP, blaVIM and blaOXA. Multi-locus sequence typing (MLST) was employed to characterize the genetic relationships among the carbapenemase-producing K. Pneumonia (CPKP) isolates. In order to further investigate the risk factors and clinical outcomes of CPE colonization, a prospective case-control study was also performed. RESULTS: Twenty-six suspected CPE strains, including 17 Klebsiella pneumoniae, 6 Escherichia coli, 1 Citrobacter freundii, 1 Enterobacter Kobe, and 1 Raoultella ornithinolytica, were identified in 25 non-duplicated rectal swab samples from 25 patients, with a carriage rate of 16.67% (25/150). Through GeneXpert Carba-R and subsequent PCR and sequencing, all the suspected CPE isolates were identified to be positive for the carbapenemase genes, of which 17 were blaKPC-carriers, and another 9 were blaNDM-producers. MLST designated all the CPKP isolates to be ST11 clone. Multivariate analysis indicated that urinary system diseases, operation of bronchoscopy, and combined use of antibiotics were independent risk factors for acquiring CPE colonization in high-risk patients from the ICU and HSCT wards. CONCLUSIONS: This study revealed a high prevalence of rectal CPE colonization in high-risk patients from ICU and HSCT wards, and a predominant colonization of the KPC-producing K. pneumoniae clone ST11. Stricter infection control measures are urgently needed to limit the dissemination of CPE strains, especially in patients who were afflicted by urinary system diseases, have underwent bronchoscopy, and were previously exposed to combined antibiotic use.

Evaluation of Modified Rapid Carbapenem Inactivation Method (mrCIM) Combined with Rapid EDTA-Modified Carbapenem Inactivation Method (reCIM) to Detect Carbapenemase and Distinguish Metallo-Carbapenemase in Enterobacteriaceae Within Four Hours.

PURPOSE: To develop a rapid EDTA-modified carbapenem inactivation method (reCIM) combined with modified rapid carbapenem inactivation method (mrCIM) to detect carbapenemase and distinguish metallo-ß-lactamases from carbapenemases in Enterobacteriaceae in 4 hrs. MATERIALS AND METHODS: The sensitivities and specificities of mrCIM and reCIM were retrospectively evaluated in 247 carbapenem-resistant Enterobacteriaceae of which 107 were carbapenemase producers confirmed by PCR and sequencing. In addition, mrCIM and reCIM were prospectively evaluated with 47 carbapenem-resistant enterobacterial isolates. RESULTS: The sensitivity and specificity of mrCIM were 96.3% and 97.1% at 2.5 hrs post incubation, and the specificity increased to 98.6% at 3 hrs. The combined mrCIM and reCIM showed a sensitivity of 95.4% and a specificity of 100% at 2.5 hrs post incubation in identifying metallo-ß-lactamases, and the sensitivity increased to 97.0% at 3 hrs. These performance characteristics are comparable to mCIM and eCIM; however, compared with mCIM and reCIM tests which need at least 24 hrs to detect results, the mrCIM and reCIM required less than 4 hrs of total work time. CONCLUSION: The combined mrCIM and reCIM can be used to accurately and quickly detect carbapenemase and metallo-ß-lactamases in Enterobacteriaceae in 4 hrs and are suitable for routine use in most clinical microbiology laboratories.

Eight-Year Surveillance of Uropathogenic Escherichia coli in Southwest China.

PURPOSE: To assess antimicrobial resistance profiles change in uropathogenic Escherichia coli (UPEC) during an 8-year period, especially extended-spectrum ß-lactamase (ESBL)-producing and carbapenem-resistant isolates. MATERIALS AND METHODS: A retrospective observational study of urinary tract infections (UTIs) was performed in a territory hospital between 2012 and 2019. Isolates were identified using matrix-assisted laser desorption/ionization time of flight mass spectrometry or the VITEK 2 Compact system. The antimicrobial susceptibility testing was performed using the VITEK 2 Compact system and the ï»¿modified Kirby-Bauer disc diffusion method. RESULTS: Of the 7713 non-repetitive UPEC isolates, 7075 (91.7%) were from inpatients and 638 (8.3%) were from outpatients. The prevalence of ESBL declined from 62.5% to 49.7% (P = 0.003). Except for cefoxitin, the resistance rates of ESBL-producing isolates were mostly higher than that of non-ESBL-producing isolates (P < 0.001). The resistance rates of ampicillin (P = 0.013), ampicillin/sulbactam (P = 0.013), ceftriaxone (P < 0.001), gentamycin (P = 0.001), tobramycin (P = 0.011), and trimethoprim/sulfamethoxazole (P = 0.028) declined slightly, while the resistance rate of imipenem increased slightly (P = 0.001). The prevalence of carbapenem-resistant Escherichia coli was <2.0%. CONCLUSION: ESBL-producing Escherichia coli is still the main drug-resistant bacteria causing UTIs. We should pay attention to antimicrobial resistance in high-risk inpatient areas and take effective measures to prevent and control nosocomial infections.

Corrigendum: Carbapenem-Resistant E. cloacae in Southwest China: Molecular Analysis of Resistance and Risk Factors for Infections Caused by NDM-1-Producers.

[This corrects the article DOI: 10.3389/fmicb.2018.00658.].

Protective Regulatory T Cell Immune Response Induced by Intranasal Immunization With the Live-Attenuated Pneumococcal Vaccine SPY1 via the Transforming Growth Factor-ß1-Smad2/3 Pathway.

Vaccine effectiveness is mainly determined by the mechanism mediating protection, emphasizing the importance of unraveling the protective mechanism for novel pneumococcal vaccine development. We previously demonstrated that the regulatory T cell (Treg) immune response has a protective effect against pneumococcal infection elicited by the live-attenuated pneumococcal vaccine SPY1. However, the mechanism underlying this protective effect remains unclear. In this study, a short synthetic peptide (P17) was used to downregulate Tregs during immunization and subsequent challenges in a mouse model. In immunized mice, increase in immune cytokines (IL-12p70, IL-4, IL-5, and IL-17A) induced by SPY1 were further upregulated by P17 treatment, whereas the decrease in the infection-associated inflammatory cytokine TNF-α by SPY1 was reversed. P17 also inhibited the increase in the immunosuppressive cytokine IL-10 and inflammatory mediator IL-6 in immunized mice. More severe pulmonary injuries and more dramatic inflammatory responses with worse survival in P17-treated immunized mice indicated the indispensable role of the Treg immune response in protection against pneumococcal infection by maintaining a balance among acquired immune responses stimulated by SPY1. Further studies revealed that the significant elevation of active transforming growth factor ß (TGF-ß)1 by SPY1 vaccination activated FOXP3, leading to increased frequencies of CD4+CD25+Foxp3+ T cells. Moreover, SPY1 vaccination elevated the levels of Smad2/3 and phosphor-Smad2/3 and downregulated the negative regulatory factor Smad7 in a time-dependent manner during pneumococcal infection, and these changes were reversed by P17 treatment. These results illustrate that SPY1-stimulated TGF-ß1 induced the generation of SPY1-specific Tregs via the Smad2/3 signaling pathway. In addition, SPY1-specific Tregs may participate in protection via the enhanced expression of PD-1 and CTLA-4. The data presented here extend our understanding of how the SPY1-induced acquired Treg immune response contributes to protection elicited by live-attenuated vaccines and may be helpful for the evaluation of live vaccines and other mucosal vaccine candidates.

Carbapenem-Resistant E. cloacae in Southwest China: Molecular Analysis of Resistance and Risk Factors for Infections Caused by NDM-1-Producers.

Carbapenem-resistant Enterobacteriaceae (CRE) has been considered a serious global threat, but carbapenem resistance remains relatively uncommon in E. cloacae, especially in China. The aim of this study was to characterize carbapenem-resistant E. cloacae (CR-ECL) isolates from 2012 to 2016 in Southwest China. Our study revealed that 20 (15.2%) of the 132 CR-ECL isolates obtained from patients were identified as NDM-1, with most isolates carrying the IncFIIA plasmids. Notably, we initially observed that the E. cloacae strain co-harbored NDM-1 and IMP-8 carbapenemases simultaneously. Analysis of the genetic environment of these two genes has revealed that the highly conserved regions (blaNDM-1-bleMBL-trpF-tat) are associated with the dissemination of NDM-1, while IS26, intI1, and tniC could be involved in the spread of IMP-8. Molecular epidemiology studies showed the nosocomial outbreak caused by NDM-1-producing E. cloacae ST88. Transferring from another hospital and previous carbapenem exposure were identified as independent risk factors for the acquisition of NDM-1-producing E. cloacae. These findings emphasize the need for intensive surveillance and precautions to monitor the further spread of NDM-1 in China.

spd1672, a novel in vivo-induced gene, affects inflammatory response in a murine model of Streptococcus pneumoniae infection.

spd1672, a novel Streptococcus pneumoniae (hereinafter S. pn) gene induced in vivo, has been identified to contribute to the virulence of S. pn; however, the role of spd1672 during host innate immune reaction against S. pn infection is unknown. In the present study, mice were infected with wild-type D39 and mutant D39Δspd1672 strains. Compared with the D39-infected mice, reduced bacterial load and attenuated inflammatory response were observed in the D39Δspd1672-treated mice. The levels of proinflammatory cytokines, including IFN-γ, TNF-α, and IL-1ß, in the blood of D39Δspd1672-infected mice were lower than that in the D39-infected group. Additionally, attenuated activation of STAT3 and AKT was observed in the D39Δspd1672-infected mice. In conclusion, our data indicated that spd1672 expression modulates the release of proinflammatory cytokines, and AKT-STAT3 signaling appears to participate in the process. In conclusion, the present study extends our understanding of the role of an in vivo-induced gene in S. pn-host interaction.

Heteroresistance to carbapenems in invasive Pseudomonas aeruginosa infections.

Heteroresistance is common in a variety of microbes, however carbapenem heteroresistance among invasive Pseudomonas aeruginosa infections has not been thoroughly characterised to date. The objective of this study was to investigate the mechanisms, molecular epidemiology and risk factors for invasive carbapenem-heteroresistant P. aeruginosa (CHPA) infections between 2011 and 2015 in Chongqing, China. A significant increase in the rates of heteroresistance to imipenem and meropenem was observed during the study period. Mechanistic analysis revealed that efflux system overexpression and decreased OprD could have contributed to carbapenem heteroresistance in P. aeruginosa. It was also observed that all of the subpopulations produced enhanced levels of biofilm compared with their native strains. Moreover, previous carbapenem exposure was identified as a common independent risk factor for imipenem-heteroresistant (IPM-HR) and meropenem-heteroresistant (MEM-HR) isolates, but patients infected with MEM-HR isolates were at higher risk of poor outcomes than those with IPM-HR isolates. Most importantly, there was a remarkable increase in the prescription of carbapenems during the study period, which was demonstrated to correlate significantly with the quarterly increasing prevalence of IPM-HR and MEM-HR isolates, respectively. These findings show the necessity of routine detection of carbapenem-heteroresistant strains and that strict control of carbapenem use is critical to reduce CHPA infections in hospitalised patients.

Multidrug Resistance Mechanisms of Carbapenem Resistant Klebsiella pneumoniae Strains Isolated in Chongqing, China.

BACKGROUND: Carbapenem-resistant Klebsiella pneumoniae (CRKP) is considered a serious global threat. However, little is known regarding the multidrug resistance (MDR) mechanisms of CRKP. This study investigated the phenotypes and MDR mechanisms of CRKP and identified their clonal characteristics. METHODS: PCR and sequencing were utilized to identify antibiotic resistance determinants. Integron gene cassette arrays were determined by restriction fragment length polymorphism (RFLP) analysis. Multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were used for epidemiological analysis. Plasmids were typed by using a PCR-based replicon typing and analyzed by conjugation and transformation assays. RESULTS: Seventy-eight strains were identified as resistant to at least one carbapenem; these CRKP strains had a high prevalence rate (38.5%, 30/78) of carbapenemase producers. Additionally, most isolates harbored MDR genes, including Extended spectrum ß-lactamases (ESBLs), AmpC, and quinolone and aminoglycoside resistance genes. Loss of porin genes was observed, and Class 1 integron was detected in 66.7% of the investigated isolates. PFGE and MLST results excluded the occurrence of clonal dissemination among these isolates. CONCLUSIONS: A high prevalence of NDM-1 genes encoding carbapenem resistance determinants was demonstrated among the K. pneumoniae isolates. Importantly, this is the first report of bla(NDM-1) carriage in a K. pneumoniae ST1383 clone in China and of a MDR CRKP isolate co-harboring bla(NDM-1), bla(KPC-2), bla(CTX-M), bla(SHV), acc(6')-Ib, rmtB, qnrB, and acc(6')-Ib-cr.

Evaluation of Six Phenotypic Methods for the Detection of Carbapenemases in Gram-Negative Bacteria With Characterized Resistance Mechanisms.

BACKGROUND: We compared the performance of the modified Hodge test (MHT), Triton Hodge test (THT), Carba NP test (CNPt), simplified Carba NP test (CNPt-direct), blue-Carba NP test (BCT), and carbapenem inactivation method (CIM) for rapid and accurate carbapenemase detection. METHODS: The methods were evaluated by using 256 gram-negative isolates, including 197 Enterobacteriaceae (79 Enterobacter spp., 74 Klebsiella spp., 33 Escherichia coli, 10 Citrobacter spp., and 1 Serratia marcescens), 51 Acinetobacter baumannii, and 8 Pseudomonas aeruginosa strains. The collection included 117 non-carbapenemase, 18 Klebsiella pneumoniae carbapenemases (KPC) producers, 46 New Delhi metallo-ß-lactamases (NDM) producers, 11 imipenemases (IMP) producers, and 51 oxacillinases (OXA) producers, and 13 strains harboring two different carbapenemase genes. RESULTS: The specificity of the THT (91.5%) was significantly lower than other methods, each of which had 100% specificity (P<0.003). This can be attributed to the false detection of Ampler class C ß-lactamases (AmpC) carriers. The CNPt-direct and CIM yielded the highest sensitivities (P<0.003), which were comparable (92.8% vs 93.5%, P>0.999). Because of improved detection of NDM carriers, THT showed significantly higher sensitivity than the MHT (84.9% vs 75.5%, P<0.001). However, poor performances in detecting OXA still influenced the sensitivities of the CNPt (66.2%) and BCT (82.0%), as well as the MHT and THT. CONCLUSIONS: CNPt-direct and CIM demonstrated the best performance for the efficient detection of carbapenemase among the six evaluated methods. Except the MHT and THT, the detection of carbapenemase-producing Enterobacteriaceae by all the other methods was acceptable, when the OXA-type carbapenemase was not prevalent.

A corrected effective density fluid model for gassy sediments.

A corrected effective density fluid model is developed for predicting sound speed dispersion and attenuation coefficient in gassy sediments. An acoustic experiment was undertaken to measure the attenuation coefficient in a frequency band of 600 to 3000 Hz in gassy unsaturated sand. The measured frequency spectra of the attenuation coefficient show four peaks due to bubble resonance. Then a method of using several modified Gaussian functions to model bubble size distribution is proposed to fit measured attenuation data, which shows that the magnitudes of the fitted model attenuation coefficients are broadly in agreement with those measured attenuation data.

Epidemiology, antifungal susceptibilities, and risk factors for invasive candidiasis from 2011 to 2013 in a teaching hospital in southwest China.

BACKGROUND: Invasive candidiasis (IC) is the most common cause of invasive fungal infections. Identification of risk factors for such infection may help in the empirical therapeutic decision-making process. We conducted this study to characterize the clinical epidemiology of such infection and to differentiate risk factors between Candida albicans and Candida non-albicans species. METHODS: We retrospectively evaluated patients with IC from 2011 to 2013. Clinical data, antibiotic therapy, underlying condition, and invasive procedures were analyzed and compared between C. albicans and C. non-albicans species. RESULTS: C. albicans was the most frequently isolated Candida species (48.6% of all IC patients), although C. non-albicans spp. were more commonly isolated overall. C. albicans, Candida tropicalis, and Candida parapsilosis have a high susceptibility rate to all antifungal agents (>90%), whereas Candida glabrata showed decreased susceptibility to fluconazole and itraconazole. Amphotericin B demonstrated excellent antifungal activity against all Candida species. Univariate analyses showed that IC patients with C. albicans had a higher ratio of older age (p = 0.008), solid tumor (p = 0.029), and hypoproteinemia (p = 0.019), whereas those with C. non-albicans spp. had a higher ratio of hospital length of stay (p = 0.005), usage of corticosteroids (p = 0.011), duration on corticosteroids (p = 0.005), chemotherapy (p = 0.022), hematologic malignancy (p = 0.039), neutropenia (p = 0.030), and usage of glycopeptides (p = 0.002). Multivariate analyses showed that a significant predictor of IC due to C. albicans was hypoproteinemia [odds ratio (95% confidence interval) = 2.133 (1.164-3.908), p = 0.014]. CONCLUSION: C. albicans was the most frequently isolated Candida species. The risk factors between C. albicans and C. non-albicans species are different.

Differential distribution patterns of ammonia-oxidizing archaea and bacteria in acidic soils of Nanling National Nature Reserve forests in subtropical China.

In addition to ammonia-oxidizing bacteria (AOB) the more recently discovered ammonia-oxidizing archaea (AOA) can also oxidize ammonia, but little is known about AOA community structure and abundance in subtropical forest soils. In this study, both AOA and AOB were investigated with molecular techniques in eight types of forests at surface soils (0-2 cm) and deep layers (18-20 cm) in Nanling National Nature Reserve in subtropical China. The results showed that the forest soils, all acidic (pH 4.24-5.10), harbored a wide range of AOA phylotypes, including the genera Nitrosotalea, Nitrososphaera, and another 6 clusters, one of which was reported for the first time. For AOB, only members of Nitrosospira were retrieved. Moreover, the abundance of the ammonia monooxygenase gene (amoA) from AOA dominated over AOB in most soil samples (13/16). Soil depth, rather than forest type, was an important factor shaping the community structure of AOA and AOB. The distribution patterns of AOA and AOB in soil layers were reversed: AOA diversity and abundances in the deep layers were higher than those in the surface layers; on the contrary, AOB diversity and abundances in the deep layers were lower than those in the surface layers. Interestingly, the diversity of AOA was positively correlated with pH, but negatively correlated with organic carbon, total nitrogen and total phosphorus, and the abundance of AOA was negatively correlated with available phosphorus. Our results demonstrated that AOA and AOB were differentially distributed in acidic soils in subtropical forests and affected differently by soil characteristics.

[Identification of a point mutation in the promoter region of cps operon responsible for capsular polysaccharide deficiency in Streptococcus pneumniae SPY1].

OBJECTIVE: To determine if the point mutation of nt313713 T --> C in the promoter region of capsular polysaccharide biosynthesis (cps) operon is responsible for the deficiency of capsular polysaccharide in S. pneumoniae SPY1 strain. METHODS: Western blot was used to compare the amounts of capsular polysaccharide between the wild-type strain and SPY1 strain. Real-time quantitative PCR was used to determine transcription levels of the first four genes of cps operon , cps2A, cps2B, cps2C and cps2D. The lacZ gene was used as a reporter gene to report the strength of the promoters on cps transcription. The cps promoter was amplified by PCR from the wild-type strain or SPY1 strain. The amplified fragments were cloned into shuttle vector pEVP3, transformed into S. pneumoniae D39 or SPY1 strain. The transcription activities of the promoters on capsular polysaccharide biosynthesis were determined by using ß-galactosidase as the reporter. Transmission electron microscopy and the Neufeld test were used to reveal the changes in capsule. RESULTS: Compared to that in the wild-type strain, mRNA levels of the cps genes were significantly decreased in SPY1 strain. The amount of CPS was also decreased in SPY1 strain. ß-galactosidase activities in SPY1-pEVP3-cps promoter(SPY1) and D39-pEVP3-cps promoter(SPY1) were decreased by about 79% and 76%, respectively, compared to that of the control. Transmission electron microscopy showed that the amount of the capsular polysaccharide of SPY1-pEVP3-cps promoter(D39) strain was restored to the wild-type level. In addition, capsular polysaccharide was absent in the D39-pEVP3-cps promoter(SPY1) (NC_008533. 1 313713 T --> C) strain as determined by Neufeld test. CONCLUSION: The point mutation of nt313713 T --> C in the cps promoter region results in a significantly reduced transcription of the cps genes, which is responsible for the significant reduction or even absence of the biosynthesis of capsular polysaccharide in SPY1 strain.

Retrospective analysis of hospital-acquired linezolid-nonsusceptible enterococci infection in Chongqing, China, 2011-2014.

BACKGROUND: Linezolid-nonsusceptible enterococci (LNSE) is an increasingly emerging multidrug-resistant pathogen, and the caused nosocomial infections are difficult to manage. However, data on the host-related risk factors and clinical outcomes for LNSE infection are poorly characterized. METHODS: A retrospective case-case-control study of risk factors and clinical outcomes of hospitalized patients with LNSE infection during the period 2011-2014 was conducted in a teaching hospital in Chongqing, China. Case patients with LNSE and those with linezolid-susceptible enterococci (LSE) and controls with no enterococcal infection were compared at a ratio of 1:1:4. Two parallel multivariate logistic regression models were used to evaluate independent predictors for acquiring LNSE and LSE, respectively. RESULTS: Forty-four LNSE cases, 44 LSE cases, and 176 uninfected controls were analyzed. Multivariable analysis indicated that transferring from another hospital (odds ratio [OR], 3.57; 95% confidence interval [CI], 1.58-8.09), peripheral vascular disease (OR, 4.36; 95% CI, 1.64-11.60), and exposure to cephalosporins (OR, 4.24; 95% CI, 1.85-9.71) were unique independent predictors for acquiring LNSE. Gallbladder disease (OR, 3.64; 95% CI, 1.36-9.74) was independently associated with LSE acquisition. Polymicrobial infection was the only factor identified in both LNSE and LSE groups compared with controls; however, no statistical significance was observed in in-hospital mortality. CONCLUSION: Timely control efforts and appropriate antibiotic stewardship programs are necessary to effectively reduce the burden of LNSE infections among high-risk patients.

Interleukin 4 Deficiency Reverses Development of Secondary Pseudomonas aeruginosa Pneumonia During Sepsis-Associated Immunosuppression.

BACKGROUND: Interleukin 4 (IL-4) is an important cytokine that may modulate development of secondary bacterial pneumonia during sepsis-induced immunosuppression. METHODS: We established an experimental model of cecal ligation and puncture (CLP)-induced sublethal polymicrobial sepsis followed by secondary Pseudomonas aeruginosa pulmonary infection, RESULTS: IL-4-deficient mice that underwent CLP were resistant to secondary pulmonary P. aeruginosa infection. As compared to wild-type mice, IL-4 knockout (KO) mice displayed improved survival and better bacterial clearance. Furthermore, IL-4 KO mice exhibited enhanced lung inflammation, neutrophil recruitment to airspaces, and elevated pulmonary cytokine production, with significantly increased tumor necrosis factor α (TNF-α) production. Neutralization of TNF-α could reverse the enhanced protection against secondary P. aeruginosa pneumonia in septic IL-4 KO mice, indicating that the resistance of septic IL-4 KO mice to secondary bacterial pneumonia was partially mediated by TNF-α. In addition, IL-4 priming displayed marked impairment of the ability of alveolar macrophages to phagocytose and kill P. aeruginosa in vitro, and this defect was associated with decreased activation of Akt, JNK, p38MAPK, and ERK intracellular signaling pathways by IL-4. Finally, neutralization of IL-4 in septic mice could improve survival and clearance of bacteria from the lungs of septic mice infected with P. aeruginosa. CONCLUSIONS: Our findings provide new insight for immunopathologic mechanisms of sepsis-induced secondary bacterial pneumonia.

Mucosal immunization with the live attenuated vaccine SPY1 induces humoral and Th2-Th17-regulatory T cell cellular immunity and protects against pneumococcal infection.

Mucosal immunization with attenuated vaccine can protect against pneumococcal invasion infection, but the mechanism was unknown. Our study found that mucosal delivery with the live attenuated SPY1 vaccine strain can confer T cell- and B cell-dependent protection against pneumococcal colonization and invasive infection; yet it is still unclear which cell subsets contribute to the protection, and their roles in pneumococcal colonization and invasion remain elusive. Adoptive transfer of anti-SPY1 antibody conferred protection to naive µMT mice, and immune T cells were indispensable to protection examined in nude mice. A critical role of interleukin 17A (IL-17A) in colonization was demonstrated in mice lacking IL-17A, and a vaccine-specific Th2 immune subset was necessary for systemic protection. Of note, we found that SPY1 could stimulate an immunoregulatory response and that SPY1-elicited regulatory T cells participated in protection against colonization and lethal infection. The data presented here aid our understanding of how live attenuated strains are able to function as effective vaccines and may contribute to a more comprehensive evaluation of live vaccines and other mucosal vaccines.

Characterization of carbapenemases, extended spectrum ß-lactamases, quinolone resistance and aminoglycoside resistance determinants in carbapenem-non-susceptible Escherichia coli from a teaching hospital in Chongqing, Southwest China.

Carbapenem-resistant Escherichiacoli isolates harboring carbapenemases or combining an extended-spectrum ß-lactamase (ESBL) enzyme with loss of porins present an increasingly urgent clinical danger. Combined resistance to aminoglycosides and fluoroquinolones in carbapeneme non-susceptible (CNS) isolates will inevitably create problems. In the current study, we characterized the carbapenemases and ESBLs, and the prevalence of quinolone resistance determinants and aminoglycoside resistance determinants in carbapenem-non-susceptible (CNS) E.coli isolates from a teaching hospital in Chongqing, Southwest China in 2012. Thirty non-duplicated CNS E.coli isolates were screened via antimicrobial susceptibility testing, and the drug resistance profiles of the 30 strains were analyzed. Carbapenemase genes blaKPC-2, ESBL genes including blaCTX-M-3, blaCTX-M-14, blaCTX-M-55 and blaTEM, ARD genes including aac(6')-Ib, armA and rmtB, and QRD genes including qnrA, qnrB, qnrC, qnrD, qnrS and aac(6')-Ib-cr were identified and clonal relatedness was investigated by pulsed-field gel electrophoresis. Of the 30 isolates, 2 (6.7%) harbored carbapenemase gene blaKPC-2; 29 (96.7%) carried ESBLs; 20 (66.7%) were QRD positive; and 11 (36.7%) were ARD positive. Between the two blaKPC-2 positive strains, one contained ESBL, QRD and ARD genes, while the other expressed ESBL genes but was negative for both QRD and ARD genes. Of the 29 ESBLs positive isolates, 2 (6.9%) were carbapenemase positive, 19 (65.5%) were QRD positive, and 11 (37.9%) were ARD positive. PFGE revealed genetic diversity among the 30 isolates, indicating that the high prevalence of CNS E. coli isolates was not caused by clonal dissemination. Production of ESBLs was associated with the carbapenem resistance and QRD genes were highly prevalent among the CNS E. coli isolates. Multiple resistant genes were co-expressed in the same isolates. This is the first report of a multidrug resistant carbapenem-non-susceptible E.coli co-harboring resistant determinants blaKPC-2, blaCTX-M-14, blaCTX-M-55, blaTEM, aac(6')-Ib-cr, qnrB, aac(6')-Ib and rmtB from Chongqing, mainland China.