Distribution of Aminoglycoside Resistance Genes in Coagulase-Negative Staphylococci Isolated From Hospitalized Patients

Abstract

Background: The incidence of coagulase-negative staphylococci (CNS) isolates, as causes of hospital-acquired infections, is increasing annually and it is a truly global challenge. Objectives: The current study aimed at assessing aminoglycoside resistance genes among CNS isolated from hospitalized patients and investigating the prevalence of methicillin and aminoglycoside resistance genes using molecular methods. Methods: A total of 103 species of coagulase negative staphylococci were isolated from clinical specimens from August 2013 to November 2014. All the specimens were identified using conventional microbiological methods including colony morphology, Gram staining, catalase, and slide and tube coagulase. The isolates were subjected to the API-20 Staph identification kit. Antibiotic susceptibility tests were performed using Kirby-Bauer disc diffusion method. The methicillin and aminoglycoside resistant genes among coagulase negative staphylococci were detected by polymerase chain reaction (PCR) and sequencing methods. Results: The most frequent clinically isolated coagulase negative staphylococci species were Staphylococcus hominis and S. haemolyticus (51.9%), S. epidermidis (21.7%), S. lugdunensis (9.8%), S. intermedius (4.9%), S. saprophyticus and S. simulans (3.9%), S. warneri (2.9%), as well as S. chromogenes, S. sciuri, S. caprae, S. schleiferi, and S. xylosus (0.98%). The overall rate of methicillin resistance among CNS species in the present study was 89 (86.4%). The resistance of CNS isolates against tested antibiotics was as follows: 74 (71.8%) to cefoxitin, 54 (52.4%) to kanamycin, 51 (49.5%) to gentamicin, 45 (43.7%) to tobramycin, and 16 (15.5%) to amikacin. The prevalence of aminoglycoside resistance genes such as ant (4')-Ia, aac (6')/aph (2") and aph (3')-IIIa were 89 (86.4%), 87(84.5%), and 68(66%), respectively. Conclusions: The presence of antibiotic resistance among coagulase negative Staphylococcus species, which cause nosocomial infections, has increased. Therefore, identification of coagulase negative staphylococci within 24 hours after development of enzymatic tests would be very useful in any clinical microbiology laboratory for effective treatment. Resistance to antibiotics, including aminoglycosides, develops quickly in CNS species where these antimicrobial agents are widely used. Thus, a better understanding of antibiotic resistance of CNS species is essential to eliminate antibiotic resistance in hospitals and society.

New update on molecular diversity of clinical Staphylococcus aureus isolates in Iran: antimicrobial resistance, adhesion and virulence factors, biofilm formation and SCCmec typing

“…Aminoglycosides are a class of bactericidal broad spectrum antimicrobials that bind to the A-position of 16S rRNA in 30S ribosomal small subunit and inhibit protein synthesis. Aminoglycoside-modifying enzymes (AMEs) and 16S ribosomal RNA (16S rRNA) methylation are two important mechanisms for antibiotic inactivation in the S. aureus [9]. Based on their functions, AMEs are generally categorized to three types: AAC (aminoglycoside acetyltransferase), APS (aminoglycoside phosphotransferase), and ANT (aminoglycoside nucleotidyltransferase).…”

Heavy metal and antibiotic resistance bacteria in marine sediment of pahang coastal water

“…S. saprophyticus is a gram-positive coccus commonly found in urine specimen and a common cause of urinary tract infection. Reports on multiple antibiotic resistant S. saprophyticus were mostly related to clinical isolates from hospitals but none from the marine environment [15]. High number of tourists in Teluk Chempedak might implicate to high volume of waste water (excrete products, urine) discharged into the marine environment and which eventually led to its residing in the marine sediment.…”