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e We compared carbapenemase detection among 271 Gram-negative bacilli (of which 131 were carbapenemase producers) using a novel chromogenic rapid test-the Carba NP test (CNP)-and the modified Hodge test (MHT). Sensitivities were comparable (CNP, 100%, versus MHT, 98%; P ‫؍‬ 0.08), but CNP was more specific (100% versus 80%; P < 0.0001) and faster.

Susceptibility testing of the polymyxins (colistin and polymyxin B) is challenging for clinical laboratories. The Clinical and Laboratory Standards Institute (CLSI) Antimicrobial Susceptibility Testing Subcommittee evaluated two methods to enable accurate testing of these agents. These methods were a colistin broth disk elution (CBDE) and a colistin agar test (CAT), the latter of which was evaluated using two inoculum volumes, 1 μl (CAT-1) and 10 μl (CAT-10). The methods were evaluated using a collection of 270 isolates of Enterobacterales, 122 Pseudomonas aeruginosa isolates, and 106 Acinetobacter spp. isolates. Overall, 94.4% of CBDE results were in essential agreement and 97.9% in categorical agreement (CA) with reference broth microdilution MICs. Nine very major errors (VME; 3.2%) and 3 major errors (ME; 0.9%) were observed. With the CBDE, 98.6% CA was observed for Enterobacterales (2.5% VME, 0% ME), 99.3% CA was observed for P. aeruginosa (0% VME, 0.7% ME), and 93.1% CA was observed for Acinetobacter spp. (5.6% VME, 3.3% ME). Overall, CA was 94.9% with 6.8% VME using CAT-1 and improved to 98.3% with 3.9% VME using CAT-10. No ME were observed using either CAT-1 or CAT-10. Using the CAT-1/CAT-10, the CA observed was 99.4%/99.7% for Enterobacterales (1%/0.5% VME), 98.7%/100% for P. aeruginosa (8.3%/0% VME), and 88.5%/92.3% for Acinetobacter spp. (21.4%/14.3% VME). Based on these data, the CLSI antimicrobial susceptibility testing (AST) subcommittee endorsed the CBDE and CAT-10 methods for colistin testing of Enterobacterales and P. aeruginosa.

Background Rapid blood culture diagnostics are costly and of unclearbenefit for patients with Gram-negative bacilli (GNB) bloodstream infections (BSIs). We conducted a multicenter, prospective, randomized controlled trial comparing outcomes of patients with GNB BSI who had blood culture testing with standard of care (SOC) culture and antimicrobial susceptibility testing (AST) versus rapid organism identification (ID) and phenotypic AST using the Accelerate Pheno™ System (RAPID). Methods Patients with positive blood cultures with Gram stains showing GNB were randomized to SOC testing with antimicrobial stewardship review (AS) or RAPID with AS, at two medical centers between 10/2017-10/2018. The primary outcome was time to first antibiotic modification within 72 hours of randomization. Results Of 500 randomized subjects, 448 were included (226 SOC, 222 RAPID). Mean (S.D.) hours to results was faster for RAPID than SOC for organism ID [2.7 (1.2) vs 11.7 (10.5), p &lt; 0.001] and AST [13.5 (56) vs. 44.9 (12.1), p&lt;0.001]. Median (IQR) hours to first antibiotic modification was faster in the RAPID vs. SOC arm for overall antibiotics [8.6 (2.6, 27.6) vs. 14.9 (3.3, 41.1), difference 6.3, p=0.02] and Gram-negative antibiotics [17.3 (4.9, 72) vs. 42.1 (10.1, 72), difference 24.8, p&lt;0.001]. Median (IQR) hours to antibiotic escalation was faster in the RAPID vs. SOC arm for antimicrobial-resistant BSIs [18.4 (5.8, 72) vs. 61.7 (30.4, 72), difference 43.3, p=0.01]. There were no statistically significant differences between the arms in patient outcomes including mortality and length of stay. Conclusion Rapid organism ID and phenotypic AST led to faster changes in antibiotic therapy for Gram-negative BSIs. (Funded by the U.S. NIH UM1AI104681; ClinicalTrials.gov number, NCT03218397.)

Vancomycin-resistant enterococci (VRE) are increasingly isolated from clinical specimens. One hundred clinical isolates of enterococci (E. casseliflavus/E. flavescens [n ‫؍‬ 10], E. faecalis [n ‫؍‬ 34], E. faecium [n ‫؍‬ 43], E. avium [n ‫؍‬ 1], E. gallinarum [n ‫؍‬ 11], and E. raffinosus [n ‫؍‬ 1]) were examined for the presence of vanA, vanB, vanC-1, and vanC-2/3 genes by a single multiplex PCR performed directly with colonies from blood agar plates. Six previously characterized VRE strains which carry either vanA, vanB, vanC-1, or vanC-2 genes were used as controls. To discriminate among van genes, the PCR amplicons were digested with MspI and were electrophoresed on agarose gels. Because of significant sequence homology between vanC-2 and vanC-3 genes, this assay is unable to discriminate these genes from each other; therefore, these are referred to as vanC-2/3 genes. PCR products were detected in 63 of the 100 clinical isolates. The restriction fragment length patterns were consistent with vanA for 10 strains, vanB for 30 strains, vanC-1 for 12 strains, vanC-2 for 6 strains, and vanA and vanC-1 for 1 strain. The vancomycin MICs for the isolates with restriction fragment length patterns consistent with vanA and vanB were all >64 g/ml. The vancomycin MICs for the isolates with restriction fragment length patterns consistent with vanC-1 or vanC-2 were 4 to 8 g/ml. The vancomycin MICs for the isolates from which no PCR amplicons were produced were 2 to 4 g/ml. A PCR product was produced in four isolates (vancomycin MICs, 4 to >256 g/ml) with restriction fragment length patterns differing from those for the control vanA, vanB, vanC-1, and vanC-2 isolates. DNA sequencing of these amplicons revealed that two of the four isolates had nucleic acid sequences which were closely related to the published sequence for the vanB gene and two had nucleic acid sequences which were closely related to the published sequence for the vanC-2 and vanC-3 genes. Multiplex PCR-restriction fragment length polymorphism appears to be a useful and convenient method for rapidly detecting and discriminating genotypes for vancomycin-resistant Enterococcus spp. in the clinical laboratory. In instances in which unusual restriction fragment patterns of PCR amplicons occur, DNA sequencing can be performed to discriminate van genotypes.

Staphylococcus lugdunensis is a coagulase-negative staphylococcus that has several similarities to Staphylococcus aureus. S. lugdunensis is increasingly being recognized as a cause of prosthetic joint infection (PJI). The goal of the present retrospective cohort study was to determine the laboratory and clinical characteristics of S. lugdunensis PJIs seen at the Mayo Clinic in Rochester, MN, between 1 January 1998 and 31 December 2007. Kaplan-Meier survival methods and Wilcoxon sum-rank analysis were used to determine the cumulative incidence of treatment success and assess subset comparisons. There were 28 episodes of S. lugdunensis PJIs in 22 patients; half of those patients were females. Twenty-five episodes (89%) involved the prosthetic knee, while 3 (11%) involved the hip. Nine patients (32%) had an underlying urogenital abnormality. Among the 28 isolates in this study tested by agar dilution, 24 of 28 (86%) were oxacillin susceptible. Twenty of the 21 tested isolates (95%) lacked mecA, and 6 (27%) of the 22 isolates tested produced ␤-lactamase. The median durations of parenteral ␤-lactam therapy and vancomycin therapy were 38 days (range, 23 to 42 days) and 39 days (range, 12 to 60 days), respectively. The cumulative incidences of freedom from treatment failure (standard deviations) at 2 years were 92% (؎7%) and 76% (؎12%) for episodes treated with a parenteral ␤-lactam and vancomycin, respectively (P ‫؍‬ 0.015). S. lugdunensis is increasingly being recognized as a cause of PJIs. The majority of the isolates lacked mecA. Episodes treated with a parenteral ␤-lactam antibiotic appear to have a more favorable outcome than those treated with parenteral vancomycin.Staphylococcus lugdunensis, a coagulase-negative staphylococcus, was first described by Freney et al. in 1988 (6) on the basis of the analysis of 11 strains collected in Lyon, France. It is increasingly being identified as a cause of serious infections (10,12,13,(15)(16)(17). This organism may produce a bound coagulase via a clumping factor, a property which, if it is present, it shares with Staphylococcus aureus; but unlike S. aureus, it does not produce a free coagulase. In the laboratory, it can give a positive slide (short) coagulase test result but gives a negative tube (long) coagulase test result; hence, if appropriate tests are not performed, it is sometimes misidentified as S. aureus. Of the many coagulase-negative staphylococci that react to pyrrolidonylarylamidase (PYR), only S. lugdunensis, along with a small number of Staphylococcus epidermidis strains, is able to decarboxylate ornithine, distinguishing it from other staphylococcal species (13, 15).Although it is classified as a coagulase-negative staphylococcus, S. lugdunensis can be virulent and can cause serious infections, including prosthetic joint infections (PJIs), endocarditis, osteomyelitis, and septicemia. This organism is considered part of the normal flora of human skin, and it has been reported to be present in the perineum and inguinal area as well (10,16,17,21). In additio...

Among 177 carbapenemase-producing Gram-negative bacilli (108 KPC, 32 NDM, 11 IMP, 8 OXA-48, 4 OXA-181, 2 OXA-232, 5 IMI, 4 VIM, and 3 SME producers), aztreonam-avibactam was active against all isolates except two NDM producers with elevated MICs of 8/4 and 16/4 mg/liter; ceftazidime-avibactam was active against all KPC-, IMI-, SME-, and most OXA-48 group-producing isolates (93%) but not metallo-␤-lactamase producers. Among older and contemporary antimicrobials, the most active were colistin, tigecycline, and fosfomycin, with overall susceptibilities of 88%, 79%, and 78%, respectively. The recent emergence and global dissemination of carbapenemase-producing Gram-negative bacilli (CP-GNB) pose a significant therapeutic challenge. Avibactam is a diazabicyclooctane non-␤-lactam ␤-lactamase inhibitor with broad activity against Ambler class A and C ␤-lactamases and certain class D ␤-lactamases by covalent acylation of the ␤-lactamase active site serine residue. It restores susceptibility of Enterobacteriaceae harboring extended-spectrum ␤-lactamases (ESBLs), AmpC cephalosporinases, and class A carbapenemases to ceftazidime or ceftaroline (1). In vitro studies of avibactam in combination with aztreonam have also demonstrated activity against Enterobacteriaceae harboring NDM (a class B metallo-␤-lactamase); however, there are scant data for the other less commonly encountered carbapenemases (2-4).The aim of this study was to examine the activities of ceftazidime and aztreonam with and without avibactam against a large, contemporary, international collection of CP-GNB with diverse resistance mechanisms, with MICs determined using agar dilution as recommended by the Clinical and Laboratory Standards Institute (CLSI) (5, 6). A secondary aim was to evaluate the activity of antimicrobials commonly used to treat CP-GNB infections, including the "legacy antibiotics" colistin, amdinocillin (mecillinam), and fosfomycin. A total of 177 CP-GNB were studied (Table 1), comprising 122 and 53 clinical isolates from the United States and Singapore, respectively, and 2 NCTC (National Collection of Type Cultures, United Kingdom) reference isolates. These consisted of 172 Enterobacteriaceae isolates (107 KPC, 32 NDM, 8 OXA-48, 4 OXA-181, 2 OXA-232, 5 IMI, 3 SME, and 11 IMP producers) and 5 Pseudomonas aeruginosa isolates (4 VIM producers and 1 KPC producer). Genotypic characterization was performed using PCR/sequencing as previously described (7-15). All CP-GNB isolates tested positive by the CarbaNP test (16), except for one isolate each of OXA-181 and OXA-232, which were CarbaNP negative, and one OXA-48-producing isolate, which was CarbaNP indeterminate. In addition, as a control/comparator group, we studied 29 Enterobacteriaceae (11 Klebsiella pneumoniae and 18 Escherichia coli isolates), including 18 ESBL producers (10 with porin loss), 6 plasmid-mediated AmpC producers (1 with porin loss and another coproducing an ESBL), and 5 derepressed AmpC mutants (2 with porin loss).(This work was presented in part at the 54th Interscience Conf...

We performed a comprehensive analysis of the molecular, serological, and clinical features of 16 consecutive cases of invasive streptococcal disease (ISD). The majority of cases were linked to two group A streptococcus (GAS) clones closely related by pulsed-field gel electrophoresis (PFGE) and designated as PFGE-1 and PFGE-1.1. These clones, serotyped as M-3, T-3/B3264, carried an allelic variant of the gene that encodes pyrogenic exotoxin A (speA3) and the gene that encodes streptococcal superantigen (SSA) but different emm alleles that encode M-protein. The characteristics and clinical features of patients were similar to those described in previous reports, regardless of the responsible GAS clone. However, worse clinical outcomes (shock and death) were more frequent when patients infected with PFGE1/1.1 clones were considered as a group and compared with all other patients as a group. One striking feature in some patients with deep tissue infection was a lack of inflammatory cells despite the presence of numerous streptococci. An evaluation of PFGE profiles of GAS isolated elsewhere demonstrated that the PFGE-1 clone has caused invasive disease in other locations in the United States and in Japan.