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BACKGROUND/PURPOSE - Escherichia coli is a common pathogen to cause clinical and subclinical mastitis in cows. A total of 57 E. coli isolates from raw milk from cows were characterized genetically and biochemically.
METHODS - Extended-spectrum β-lactamase (ESBL) genes, the mechanism for fluoroquinolone resistance, and variations in virulence genes and genomes of these E. coli isolates were investigated by the antimicrobial susceptibility test, simplex and multiplex polymerase chain reaction (PCR), and pulsed-field gel electrophoresis (PFGE).
RESULTS - All E. coli isolates were resistant to cloxacillin (100%) and to a lesser extent (50%) to tetracycline, neomycin, gentamycin, ampicillin, ceftriaxone, cefotaxime (CTX), and ceftazidime (CAZ). Nearly 70% of the isolates were resistant to at least two antimicrobials and 28.1% carried AmpA and AmpC genes simultaneously. The predominant bla gene was bla, followed by bla, bla, bla, and bla Among the six (10.5%) ESBL-producing E. coli carrying bla, bla, or bla, two isolates 31 of ST410 in the ST23 complex and 58 of ST167 in the ST10 complex were also resistant to ciprofloxacin, enrofloxacin, and levofloxacin, with mutations at codon 83 from serine to leucine and codon 87 from aspartic acid to asparagine in GyrA and at codon 80 from serine to isoleucine in ParC. These isolates were genetically diverse in pulsotype analysis, lacked toxin genes of human pathogenic E. coli and carried mostly the prevalent virulence genes fimH, papGII, and α-hemolysin.
CONCLUSION - Lacking virulence genes examined, genetic diverse E. coli isolates are unrelated to human pathogenic E. coli. Enhancing sanitation in milk processing and transportation is needed to eliminate multidrug-resistant (MDR), fluoroquinolone-resistant, and ESBL-producing E. coli isolates.
Copyright © 2014. Published by Elsevier B.V.

To determine the prevalence of and indications for vancomycin administration among hospitalized chronic hemodialysis patients, we performed a 3-month prospective cohort study at a tertiary care center. Modified guidelines for vancomycin use from the Hospital Infections Control Practices Advisory Committee of the Centers for Disease Control and Prevention were used. Vancomycin was administered during 56 of 144 admissions (39%) requiring chronic hemodialysis compared with 336 of 7,212 admissions (5%) not requiring hemodialysis (relative risk, 11; 95% confidence interval, 8 to 15; P < 0.001). Among chronic hemodialysis patients, vancomycin use was judged appropriate for 131 of the 164 vancomycin doses (80%). The most common appropriate indication was empiric therapy in a febrile patient before culture or susceptibility results. Of 32 infections identified in patients who received empiric vancomycin, 15 infections (47%) were caused by beta-lactam-resistant pathogens. Among the 33 doses (20%) judged inappropriate, continued therapy for a presumed infection despite failure to identify a beta-lactam-resistant pathogen was the most common indication. Although vancomycin administration was frequent among hospitalized chronic hemodialysis patients, its use was justified in the majority of cases. Efforts should focus on limiting vancomycin administration for treating infections caused by beta-lactam-sensitive pathogens.

To understand the biochemical basis of resistance of bacteria to beta-lactam antibiotics, we purified a penicillin-resistant penicillin-binding protein 2x (R-PBP2x) and a penicillin-sensitive PBP2x (S-PBP2x) enzyme of Streptococcus pneumoniae and characterized their transpeptidase activities, using a thioester analog of stem peptides as a substrate. A comparison of the k(cat)/Km values for the two purified enzymes (3,400 M(-1) s(-1) for S-PBP2x and 11.2 M(-1) s(-1) for R-PBP2x) suggests that they are significantly different kinetically. Implications of this finding are discussed. We also found that the two purified enzymes did not possess a detectable level of beta-lactam hydrolytic activity. Finally, we show that the expression levels of both PBP2x enzymes were similar during different growth phases.