Detection of methicillin-resistance (mec-A) gene inStaphylococcus aureus strains by PCR and determination of antibiotic susceptibility

Effect of enterocins against methicillin-resistant animal-derived staphylococci

The occurence and spread of animal-derived methicillin resistant staphylococci (MRS) worldwide is a current problem, especially due to their increasing incidence in food animals and their products, with possible contamination of food consumers and handlers. Staphylococci isolated from animals (n = 123) were identified with MALDI-TOF mass spectrometry and screened for methicillin/oxacillin/cefoxitin resistance (MR) using the disk diffusion method. Twenty-three phenotypically MRS strains were analysed using PBP2' Latex Agglutination Test Kit to confirm the phenotypic MR and PCR was performed for mecA gene detection; mecA gene positive strains were furtherly confirmed by means of sequencing. The susceptibility of MRS to 11 partially-purified enterocins (Ent) produced by E. faecium, E. durans and E. mundtii strains of animal, feed/food and environmental origin was checked using agar spot tests. Out of 23 MRS, PBP testing confirmed MR in 17 strains. Three Staphylococcus epidermidis and one S. vitulinus were mecA positive. The majority of MRS, including two mecA gene-positive strains S. epidermidis R44/1 and P3/Tr2a, were susceptible to the tested enterocins, mainly to Ent7420, EntA(P)/EK13, Ent412, Ent55 and Ent9296 (in the range 100 - 12,800 AU/mL). The most susceptible strains appeared to be the mecA gene-positive S. epidermidis SE R44/1 and SE P3/Tr2a strains, inhibited by eight enterocins out of 11 tested (100-200 AU/mL). Only four strains (including mecA gene positive S. epidermidis SE P3/Tr1 and S. vitulinus SV K12PL/1) were resistant to the tested antimicrobial substances. These results indicate that the enterocins used offer a promising option for prevention and treatment of bacterial infection caused by MRS in animals.

Prevalence of PVL and LucED Genes in Methicillin-Resistant and Susceptible Isolates of Staphylococcus aureus Isolated from Burn Patients in Kermanshah, Iran

Background: The main pathogen causing various nosocomial infections, especially in burn patients, is Staphylococcus aureus. An important virulence factor of this bacterium is leukocidin, which binds to white blood cells and leads to apoptosis and necrosis. Objectives: In the present research, we aimed at investigating the prevalence of the panton-valentine leukocidin (PVL) and LucED genes in methicillin-susceptible and resistant isolates of S. aureus isolated from burn patients in Kermanshah, Iran. Methods: Overall, 73 isolates of S. aureus were collected from burn wounds and identified by specific biochemical tests. After determining the susceptibility patterns of the isolates by the disc diffusion method, the frequencies of the PVL and LucED genes were assessed using specific primers and polymerase chain reactions. Results: The rates of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA) isolates were 58.9% (43 isolates) and 41.1% (30 isolates), respectively. In MRSA isolates, the highest antibiotic resistance was to penicillin (100%) and gentamicin (81.4%). Moreover, the frequencies of the LucED and PVL genes were 76.7% (56 isolates) and 27.4% (20 isolates), respectively, and the highest frequency of the LucED and PVL genes was observed in MRSA (81.4%) and MSSA (40%) isolates, respectively. Conclusions: Increased multidrug resistance pattern among S. aureus isolates with leukocidin production has led to treatment failure and severe infections. The development of infections can be prevented by the identification of isolates carrying the leukocidin gene, and early detection of MRSA isolates is feasible by using the PVL gene.

Molecular analysis of the coagulase gene in clinical and nasal carrier isolates of methicillin-resistant Staphylococcus aureus by restriction fragment length polymorphism

OBJECTIVES

The coagulase enzyme, encoded by the coa gene, is an important virulence factor of Staphylococcus aureus and can be used for typing of S. aureus isolates. In this study, coa gene typing was used to study the epidemiology of S. aureus at a university hospital in Hamadān (Iran).

METHODS

A total of 200 S. aureus strains were analysed, among which 150 were isolated from clinical samples and 50 were from nasal swab specimens of carriers. Methicillin resistance was confirmed by presence of the mecA gene by PCR. For polymorphism analysis, the coa gene was amplified by PCR and the products were subjected to restriction digestion using the enzyme AluI.

RESULTS

Amplification of the coa gene produced five classes of bands based on size, ranging from 300bp to 800bp. The 600-bp amplicon included coa 3 genotype predominated in S. aureus isolated from clinical and carrier specimens (150/200; 75.0%). AluI digestion of the PCR products produced eight distinct restriction fragment length polymorphism (RFLP) patterns, designated coa 1-8. The results showed that the 700-bp and 800-bp amplicons formed two (coa 4a and 4b) and three (coa 5a, 5b and 5c) patterns following AluI digestion, respectively, whereas the 300-, 500- and 600-bp fragments generated unique patterns designated coa 1, coa 2 and coa 3, respectively.

CONCLUSIONS

This study performed coagulase typing, a technique used to determine the molecular epidemiology of S. aureus clinical isolates. coa gene amplification has been considered a simple and accurate method for typing of S. aureus.