6 articles
Extended-spectrum beta-lactamase producing Klebsiella pneumoniae
ESBL-producing Klebsiella pneumoniae: hospital Gram-negative pathogen carrying extended-spectrum beta-lactamases (TEM, SHV, CTX-M) that inactivate penicillins, cephalosporins, and aztreonam; treated with carbapenems per MERINO trial evidence.
Gram stain
Gram stain: differential bacteriological stain devised by Hans Christian Joachim Gram in Berlin, 1884. Crystal violet, iodine, decolorizer, and safranin classify bacteria as Gram-positive (purple) or Gram-negative (pink) by cell wall thickness.
Gram-negative bacteria
Gram-negative bacteria are bacteria with a thin peptidoglycan wall and an LPS-containing outer membrane, so they stain pink in the Gram stain and resist many antibiotics via porins, efflux pumps, and LPS modifications.
Gram-positive bacteria
Gram-positive bacteria are bacteria that retain crystal violet in the Gram stain and appear purple, defined by a thick 30-100 nm peptidoglycan wall, teichoic acids, and no outer membrane; examples include Staphylococcus aureus and Streptococcus pneumoniae, with MRSA and VRE as key resistant threats.
MacConkey agar
MacConkey agar (MAC): selective, differential culture medium for gram-negative bacteria, invented by Alfred MacConkey (Lancet, 1900). Bile salts and crystal violet inhibit gram-positives; lactose plus neutral red turns fermenters pink, non-fermenters colorless.
Ziehl–Neelsen stain
Ziehl–Neelsen stain: acid-fast bacteriological stain for Mycobacterium tuberculosis, developed 1882–1883 from Koch, Ehrlich, Ziehl, Rindfleisch, and Neelsen; carbol fuchsin, heat, acid decolorization; Kinyoun cold variant; auramine fluorescent alternative.