Abstract
Enterococci are a common cause of nosocomial infection and prevalence of antibiotic resistance among them is increasing. This study aimed to identify the prevalence of high level aminoglycoside resistant enterococci at Alexandria Main University Hospital. A total of 133 enterococci strains isolated from clinical specimens were all subjected to Bauer Kirby disc diffusion to detect antibiotic susceptibility pattern. High level aminoglycoside resistance (HLAR) and vancomycin resistance were confirmed by minimum inhibitory concentration (MIC). The HLAR enterococci were further identified by API 20 STREP to species level and nitrocefin test was used to detect beta lactamase production. Furthermore, polymerase chain reaction (PCR) for detection of gentamycin resistance was done to all HLGR enterococcal strains and for detection of vancomycin resistance genes. Among the 133 enterococcal isolates, 47 (35.3%) were found to be HLAR (31 Enterococcus faecalis, 13 Enterococcus faecium and 3 Enterococcus avium). They were all negative for beta lactamase production, 78.7% were erythromycin resistant, 63.8% resistant to doxycyclines, 51.06% to chloramphenicol, 46.8% to penicillin, 42.5% to rifampicin, and 40.4% to ampicillin. All HLAR enterococcal isolates were sensitive to Teigycyciln and Linezolid except one strain was resistant to linezolid. Urinary enterococcal isolates were also found to be 88.4, 84.6, 80.7 and 15.3% resistant to ciprofloxacin, levofloxacin, norfloxacin, and nitrofurantoin, respectively. Regarding PCR, all HLGR strains had Aac 6/)-Ie-aph (2//)-Ia gene except for 2 strains. It was found also that 3 HLAR enterococcal strains were vancomycin resistant, all of which were E. faecium with Van A genotype. HLAR enterococci constituted 35.3% from the total enterococci isolated during the period of study denoting the importance of these isolates as nosocomial pathogens. This situation obligates the clinical microbiologist to try to identify the most useful active antibiotic for treatment. On the other hand, physicians should use antibiotics appropriately and comply with the infection-control policies in an effort to prevent further spread of high level aminoglycoside resistant enterococci. Key words: Alexandria Egypt, enterococci, high level aminoglycoside resistance, aminoglycosides, gentamycin, antibiotic resistance, vancomycin.
Highlights
Enterococci have constituted a unique taxonomic entity since the mid-1980s when results of DNA–DNA hybridization experiments suggested their separation into the new bacterial genus, Enterococcus species from the former genus Streptococcus species (Werner, 2013)
Since early 1970s, enterococci were considered as nosocomial pathogens which coincided with increased expression of antimicrobial resistance by members of the genus and this contributed to extensive administration and misuse of antimicrobial agents (Dadfarma et al, 2013)
A total of 133 (6.3%) enterococcal strains were isolated from 2100 clinical specimens during our 6 months study period, with the highest rate of isolation being from urine; 86 strains (64.6%), followed by pus 21 strains (15.7%), blood 15 (11.2%), sputum 10 (7.5%) and only 1 (2.1%) strain was isolated from peritoneal aspirate
Summary
Enterococci have constituted a unique taxonomic entity since the mid-1980s when results of DNA–DNA hybridization experiments suggested their separation into the new bacterial genus, Enterococcus species from the former genus Streptococcus species (Werner, 2013) It has emerged as a super nosocomial infecting pathogen due to their inherent resistance to multiple antimicrobial agents A common regimen for treatment of serious enterococcal infections such as septicemia and endocarditis is the synergistic combination of cell wall inhibitors as penicillin, ampicillin or vancomycin with aminoglycosides such as streptomycin or gentamycin (Levison and Mallela, 2000) This synergy is lost in enterococci exhibiting high level aminoglycoside resistance (HLAR) due to production of aminoglycoside modifying enzymes which inactivate aminoglycoside by adenylation and phosphorylation or through ribosomally mediated resistance (Gaindo et al, 2005). Identification at the species level of enterococci isolated from clinical specimens is considered necessary, as is quantitative evaluation of their resistance to penicillin, ampicillin, vancomycin, teicoplanin and high-level resistance to gentamicin and streptomycin (Facklam et al, 1999)
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