Background Carbapenem-resistant Klebsiella pneumoniae (CRKP) has become a threat to public health, most notably as a superbug causing nosocomial infections. Patients in the intensive care unit (ICU) are at increased risk of hospital-acquired K pneumoniae infection, especially CRKP. This study was conducted to investigate the frequency of gastrointestinal and nasopharyngeal K pneumoniae colonization and its contribution to infections in ICU patients. Methods A 3-month prospective cohort study was performed in which 243 ICU patients were screened for intestinal and nasopharyngeal carriage of K pneumoniae at admission and once per week thereafter. The colonization and clinical infection isolates were analyzed by antimicrobial susceptibility testing to identify CRKP and were characterized by multilocus sequence typing (MLST) and whole-genome sequencing combined with epidemiological data to investigate the resistance mechanisms and assess the possible transmitted infection. Results Twenty-eight percent (68 of 243) of patients tested positive for carriage of K pneumoniae immediately upon admission to ICU, 54% (37 of 68) of which were nonduplicate CRKP isolates. Patients with carbapenem-susceptible K pneumoniae (CSKP) colonization at admission were more likely to acquire CRKP colonization during the ICU stay compared with patients without K pneumoniae colonization at admission. The incidence of subsequent CRKP infection in the baseline CSKP (32.3%, 10 of 31) and CRKP (45.9%, 17 of 37) carrier group was significantly higher than that of the baseline non-KP carrier group (8.6%, 15 of 175). The risk factors associated with acquired CRKP colonization during the ICU stay among negative CRKP colonization at admission included previous exposure to carbapenem, tigecycline or β-lactam/β-lactamases inhibitor, and invasive processes or surgical operations. Sixty-four percent (27 of 42) of patients with K pneumoniae infection were colonized by clonally related K pneumoniae strains according to enterobacterial repetitive intergenic consensus sequence-polymerase chain reaction analysis. ST11 (72%, 53 of 74) was the most predominant MLST type of clonally related CRKP isolate colonizing these patients, followed by ST15 (26%, 19 of 74). Conclusions The colonization of K pneumoniae may increase the incidence of corresponding K pneumoniae infection in critically ill patients in the ICU. High prevalence of ST11 CRKP (due to blaKPC-2) carriage and infection in ICU was observed.

The presence of adhesins is arguably an important determinant of pathogenicity for Uropathogenic Escherichia coli (UPEC). Antimicrobial susceptibilities were tested by agar dilution method, fifteen adhesin genes were detected by polymerase chain reaction, and multilocus sequence typing (MLST) was analyzed in 70 UPEC isolates and 41 commensal E. coli strains. Extended-spectrum β-lactamase (ESBL) was determined with confirmatory test. The prevalence of ESBL-producers in UPEC (53%, 37/70) was higher than the commensal intestinal isolates (7%, 3/41), and 97% (36/37) of the ESBL-producing UPEC harbored bla CTX-M genes. afa was present in 36% (10/28) UPEC isolates from recurrent lower urinary tract infection (UTI), and none in the acute pyelonephritis, acute uncomplicated cystitis or commensal strains (P<0.0001). papG was detected in 28% (20/70) of UPEC isolates, while 5% (2/41) of the commensal strains were papG positive (P = 0.0025), and the prevalence of papG was significantly higher in acute pyelonephritis group (71%) than the other two UTI groups (P<0.0001). The prevalence of flu, yqi, yadN and ygiL was significantly higher in UPEC isolates than in the commensal strains. ESBL-producing UPEC showed a lower prevalence of adhesin genes compared with non-ESBL-producing strains. The MLST profiles were different between UPEC and commensal strains, with ST131 (19%, 13/70) and ST10 (20%, 8/41) being the most common MLSTs, respectively. This study demonstrated that several adhesin genes were more prevalent in UPEC isolates than in commensal E. coli, and afa may be associated with recurrent lower UTI whereas papG is more frequently associated with acute pyelonephritis.

Carbapenems are first-line agents for the treatment of serious nosocomial infections caused by multidrug-resistant Enterobacteriaceae. However, resistance to carbapenems has increased dramatically among Enterobacteriaceae in our hospital. In this study, we report clonal dissemination caused by carbapenem-resistant Enterobacter aerogenes (CREA). In 2011, CREA was identified from 12 patients admitted to the neurosurgical ward. All 12 clinical isolates were non-susceptible to cefotaxime, ceftazidime, cefoxitin, ertapenem, imipenem or meropenem. All isolates carried the gene encoding Klebsiella pneumoniae carbapenemase-2 (KPC-2), except for the isolate E 4. However, a remarkably lower expression level of the porin OmpF was detected in the non-KPC-2-producing isolate E 4 on SDS-PAGE compared with the carbapenem-susceptible isolate. Epidemiological and molecular investigations showed that a single E. aerogenes strain (PFGE type A), including seven KPC-2-producing clinical isolates, was primarily responsible for the first isolation and subsequent dissemination. In a case-control study, we identified risk factors for infection/colonization with CREA. Mechanical ventilation, the changing of sickbeds and previous use of broad-spectrum antibiotics were identified as potential risk factors. Our findings suggest that further studies should focus on judicious use of available antibiotics, implementation of active antibiotic resistance surveillance and strict implementation of infection-control measures to avoid the rapid spread or clonal dissemination caused by carbapenem-resistant Enterobacteriaceae in healthcare facilities.

Porin deficiency plays an important role in carbapenem resistance among clinical E. aerogenes isolates under regulation of the sRNAs micC and micF. Furthermore, overexpression of micC and micF had a minor to no impact on carbapenem minimum inhibitory concentrations, and thus, the regulatory mechanism is likely to be complex.

PurposeThis study aimed to evaluate the molecular characteristics and prevalence of clinical carbapenem-resistant Klebsiella aerogenes (CRKA), collected during an outbreak in a Chinese tertiary hospital.MethodsAntimicrobial susceptibility test, using 17 antibiotics, was performed on 14 CRKA isolates. The strains were examined for the presence of β-lactamase genes by PCR, and efflux pump phenotype was determined by efflux pump inhibition test. Presence of outer-membrane porins was examined. Clonal relatedness among the isolates was investigated by pulsed-field gel electrophoresis (PFGE). S1 nuclease-PFGE and plasmid incompatibility group analysis were performed to determine plasmids, and the genetic environment of blaKPC-2 was analyzed. Epidemiological data were collected via chart review.ResultsThe 14 CRKA isolates were all resistant to carbapenems; five distinct groups (PFGE types A–E) were observed. All 14 isolates carried the blaKPC-2 gene. S1 nuclease-PFGE indicated the size of blaKPC-2-carrying plasmids to range from 20 kb to 200 kb, and the 14 plasmids belonged to various incompatibility groups. The most frequent genetic environment of blaKPC-2 was Tn1721- blaKPC-2-ΔTn3-IS26. PFGE type A group, including 11 KPC-2-producing clinical isolates, was primarily responsible for dissemination.ConclusionOur findings suggest both transposons and vertical transmission to contribute to the transformation of blaKPC-2. The results strongly suggest strict implementation of infection control of CRKA, in healthcare facilities.

Transcription activator RamA is linked to multidrug resistance of Klebsiella pneumoniae through controlling genes that encode efflux pumps (acrA) and porin‐regulating antisense RNA (micF). In bacteria, σ70, together with activators, controls the majority of genes by recruiting RNA polymerase (RNAP) to the promoter regions. RNAP and σ70 form a holoenzyme that recognizes ‐35 and ‐10 promoter DNA consensus sites. Many activators bind upstream from the holoenzyme and can be broadly divided into two classes. RamA acts as a class I activator on acrA and class II activator on micF, respectively. The authors present biochemical and structural data on RamA in complex with RNAP‐σ70 at the two promoters and the data reveal the molecular basis for how RamA assembles and interacts with core RNAP and activates transcription that contributes to antibiotic resistance. Further, comparing with CAP/TAP complexes reveals common and activator‐specific features in activator binding and uncovers distinct roles of the two C‐terminal domains of RNAP α subunit.

Nemonoxacin is a novel C-8-methoxy nonfluorinated quinolone with remarkably enhanced in vitro activity against a wide variety of clinically relevant pathogens, especially gram-positive bacteria, including multidrug-resistant Streptococcus pneumoniae and methicillin-resistant Staphylococcus aureus. It has a low propensity for selecting resistant pathogens than fluoroquinolones, since bacteria become resistant to nemonoxacin only when three different mutations occur in their quinolone resistance-determining regions. Nemonoxacin shows greater efficacy than most of the widely used fluoroquinolones in the murine model of systemic, pulmonary, or ascending urinary tract infection. Nemonoxacin has a sound PK profile in healthy volunteers. It rapidly reaches maximum concentration Cmax 1–2 hours after oral administration in the fasting state and has a relatively long elimination half-life of more than 10 hours, which is similar to fluoroquinolones. Approximately 60%–75% of the administered dose is excreted in unchanged form via kidneys over 24–72 hours. Phase II and III studies of oral nemonoxacin and Phase II studies of intravenous nemonoxacin have been completed in patients with community-acquired pneumonia (CAP), before which the Phase I studies of oral and intravenous nemonoxacin indicated sound tolerance and safety with healthy volunteers. The published results demonstrate that an oral dose of either 500 mg or 750 mg nemonoxacin once daily for 7 days is as effective and safe as levofloxacin 500 mg once daily for 7 days. Nemonoxacin is well-tolerated in patients with CAP. The most common adverse events of oral administration are observed in the gastrointestinal and nervous system, the incidence of which is similar to levofloxacin treatment. The Phase III studies of intravenous nemonoxacin for treating CAP and oral nemonoxacin for diabetic foot infection has been registered with promising outcomes to be expected.

BackgroundDifferential diagnosis of patients with suspected infections is particularly difficult, but necessary for prompt diagnosis and rational use of antibiotics. A substantial proportion of these patients have non-infectious diseases that include malignant tumors. This study aimed to explore the clinical value of metagenomic next-generation sequencing (mNGS) for tumor detection in patients with suspected infections.MethodsA multicenter, prospective case study involving patients diagnosed with suspected infections was conducted in four hospitals in Shanghai, China between July 2019 and January 2020. Based upon mNGS technologies and chromosomal copy number variation (CNV) analysis on abundant human genome, a new procedure named Onco-mNGS was established to simultaneously detect pathogens and malignant tumors in all of the collected samples from patients.ResultsOf 140 patients screened by Onco-mNGS testing, 115 patients were diagnosed with infections; 17 had obvious abnormal CNV signals indicating malignant tumors that were confirmed clinically. The positive percent agreement and negative percent agreement of mNGS testing compared to clinical diagnosis was 53.0% (61/115) and 60% (15/25), vs. 20.9% (24/115) and 96.0% (24/25), respectively, for conventional microbiological testing (both P &lt;0.01). Klebsiella pneumoniae (14.8%, 9/61) was the most common pathogen detected by mNGS, followed by Escherichia coli (11.5%, 7/61) and viruses (11.5%, 7/61). The chromosomal abnormalities of the 17 cases included genome-wide variations and local variations of a certain chromosome. Five of 17 patients had a final confirmed with malignant tumors, including three lung adenocarcinomas and two hematological tumors; one patient was highly suspected to have lymphoma; and 11 patients had a prior history of malignant tumor.ConclusionThis preliminary study demonstrates the feasibility and clinical value of using Onco-mNGS to simultaneously search for potential pathogens and malignant tumors in patients with suspected infections.