Characterization of streptomycin resistance mechanisms among Mycobacterium tuberculosis isolates from patients in New York City.

From a collection of 367 isolates of Mycobacterium tuberculosis from patients in New York City in 1994, 45 isolates (12.3%) were resistant in vitro to 2 micrograms or more of streptomycin (SM) per ml. We further evaluated these isolates for levels of SM resistance and for mutations previously associated with resistance in the rpsL (S12 ribosomal protein) gene and the rrs (16S rRNA)-coding region. Twenty-four isolates, representing nine distinct patterns of susceptibility to antituberculosis drugs, were resistant to 500 micrograms of SM per ml and shared a common point mutation at nucleotide 128 in the rpsL gene. This mutation, which substitutes lysine for arginine in the S12 ribosomal binding protein, was not present in isolates with low-level SM resistance or in SM-susceptible control isolates. Among 20 isolates with low-level SM resistance, one possessed a substitution (C-->G865) in the 912 loop of the rrs gene. No mutations in the 530 loop of the rrs coding region were detected, suggesting the presence of an alternative SM resistance mechanism in 19 isolates. Single-strand conformation polymorphisms of mutants were readily detected by a nonradioactive gel screen.

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Activity of Meropenem with a Novel Broader-Spectrum β-Lactamase Inhibitor, WCK 4234, against Gram-Negative Pathogens Endemic to New York City

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01666-19 ◽

2019 ◽

Vol 64 (1) ◽

Cited By ~ 1

Author(s):

Alejandro Iregui ◽

Zeb Khan ◽

David Landman ◽

John Quale

Keyword(s):

New York ◽

New York City ◽

York City ◽

Multidrug Resistant ◽

Resistance Mechanisms ◽

Gram Negative ◽

Content Type ◽

Carbapenem Resistant ◽

Lactamase Inhibitor

ABSTRACT WCK 4234 is a novel diazabicyclooctane with potent inhibitory activity against class A and D carbapenemases and class C enzymes. We examined the in vitro activity of meropenem plus WCK 4234 (4 or 8 μg/ml) against Gram-negative pathogens from New York City. Three groups of isolates were analyzed: a contemporary collection of isolates, a collection of known carbapenem-resistant isolates, and a collection of isolates with defined resistance mechanisms. From the contemporary collection, we found (i) that all Enterobacteriaceae were susceptible to meropenem plus WCK 4234, (ii) that susceptibility rates for Acinetobacter baumannii were 56.5% for meropenem alone, 82.6% with 4 μg/ml WCK 4234, and 95.7% with 8 μg/ml WCK 4234, and (iii) that WCK 4234 had a modest effect on susceptibility of Pseudomonas aeruginosa. Against a collection of carbapenem-resistant isolates, the addition of WCK 4234 to meropenem (i) restored meropenem susceptibility against Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae isolates, (ii) improved susceptibility against A. baumannii, and (iii) had a negligible effect against P. aeruginosa. When tested against isolates with defined mechanisms of resistance, MICs of meropenem plus WCK 4234 were higher for K. pneumoniae with blaKPC albeit well below the susceptibility breakpoint; efflux systems or porins did not correlate with susceptibility. For A. baumannii, MICs of meropenem plus WCK 4234 did not correlate with efflux systems, outer membrane protein, blaampC, or blaoxa-51; however, MICs were higher in isolates with extended-spectrum β-lactamases (ESBLs). For P. aeruginosa, isolates with relatively higher MICs of meropenem plus WCK 4234 had increased expression of ampC. WCK 4234 is a potent β-lactamase inhibitor that, when combined with meropenem, displays promising activity against multidrug-resistant pathogens.

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