ABSTRACT
OBJECTIVE: In this prospective study, we determined phenotypic resistance to erythromycin among gram positive bacteria. METHODS: BACTERIAL ISOLATES WERE IDENTIFIED BY CONVENTIONAL METHODS AND BY THE MICROSCAN: D-test zone was performed according to the Clinical and Laboratory Standards institutes (CLSI) recommendations to determine inducible resistance to clindamycin on gram positive bacteria isolated from different clinical specimens. Bacterial isolates included : group A streptococci (GAS), group B streptococci (GBS), viridans streptococci, S.pneumoniae, Staphylococcus aureus (S.aureus) (both methicillin susceptible (MSSA) and methicillin resistant (MRSA). RESULTS: A total of 1072 gram positive bacterial isolates were tested. The majority was from swabs collected from outpatient clinics. Erythromycin resistance was 8/23 (35%) for S. pneumoniae, 12/91(13%) for GAS and 17/300(5.7%) for GBS. All GAS and viridans streptococci possessed the efflux phenotype only, 8(8.8% and 1(20%), respectively. For GBS, cMLS(B) was 11(3.7%), 3 (1%) iMLS(B) and 2(0.33%) were of efflux phenotype. All S.pneumoniae strains possessed cMLS(B) phenotype. Seventy five isolates (16.3%) of MSSA were resistant to erythromycin compared to 160(83%) of MRSA. The majority of MSSA, 31/460 (6.7%) had an efflux phenotype while 26/460(5.6%) were of cMLS(B) and 19/460(4%) iMLS(B) phenotypes. Constitutive MLS(B) was the most predominant resistant phenotype, 152/193(78.8%) among MRSA. CONCLUSION: D-test zone should be considered for routine testing to detect inducible clindamycin resistance among significant gram positive bacteria.
ABSTRACT
Antimicrobial resistance to nine anti-pseudomonal agents (azteronam, ceftazidime, cefepime, piperacillin/tazobactam, imipenem, meropenem, ciprofloxacin, amikacin and gentamicin), the magnitude of multidrug resistance, associated underlying conditions, and mortality among patients with Pseudomonas aeruginosa isolates from King Khalid University Hospital, Riyadh, Saudi Arabia from 2001 to 2005 were determined. The results showed that antimicrobial resistance among P. aeruginosa is gradually increasing for most anti-pseudomonal agents, particularly aztreonam, ceftazidime, piperacillin/tazobactam and imipenem. There were 19 (3%) and 12 (2%) multidrug-resistant (MDR) P. aeruginosa patients in 2004 and 2005, respectively, and MDR P. aeruginosa was more commonly found in non-intensive care unit (ICU) patients. Most MDR isolates were from surgical and diabetic patients. The mortality rate was higher among ICU patients.
