Received date: March 16, 2012; Accepted date: March 29, 2012; Published date: March 31, 2012
Citation: Malki Fatima EL, Lekhlifi Zineb EL, Said B (2012) Identification and Characterization of Staphylococcus Isolates in Fes-Meknes Region in Morocco. Pharm Anal Acta S15:003. doi: 10.4172/2153-2435.S15-003
Copyright: © 2012 Kummalue T. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Staphylococci are among the most commonly recovered bacteria in the clinical microbiology laboratories. According to the coagulase test, staphylococci are categorized as S. aureus and coagulase negative staphylococci (CoNS). Although S. aureus is more virulent, CoNS may also cause infections, some of which may be lifethreatening. Raising staphylococci multi-drogue resistance has complicated therapeutic protocols especially for S. aureus resistant to meticillin (SARM). In our study we characterized by phenotypic and molecular data, a group of staphylococci collected from hospital laboratories. Comparison between standard laboratories procedures in routine identification and molecular methods showed a good correlation of both. Multiplex-PCR revealed that all species specific 16S RNA positive were coagulase positive and identified to be S. aureus. Besides, all mecA positive isolates were cefoxitin resistant. The prevalence of SARM was found 11.76% while meticillin resistant coagulase negative staphylococcus (MRCoNS) was 84.61%. Although the analyzed staphylococcal isolates sample is small, our study revealed a relatively low prevalence of SARM in this region of Morocco compared to others region of the world. The very high prevalence of MRCoNS isolates is alarming and demonstrating that CoNS are becoming the main source for dissemination of mecA gene.
Staphylococcus aureus; CoNS; SARM; Multiplex-PCR; mecA
Staphylococcus genus currently consists of 38 species . S. aureus is the most important pathogen and the most virulent wile S. epidermidis and other coagulase negative Staphylococci (CoNS) are commensally common flora of skin and mucous membranes and are therefore common contaminants, particularly in blood cultures. However, increased incidence of infections caused by CoNS has been reported . These bacteria have also become an important cause of hospitalacquired infections . Discrimination between S. aureus and others CoNS in clinical samples is important to evaluate the virulence level. Moreover, rising Staphylococcus isolates multi-resistant to antibiotics has complicated the antimicrobial therapeutic scheme.
Hospital infections due to methicillin-resistant Staphylococcus aureus (MRSA) strains are frequent worldwide . In fact, MRSA is considered as a serious threat to hospitalized patients and is becoming a challenge for public health. Moreover, MRSA community-acquired infections appear to be on the increase in various part of the world . The consequences to the health care system are graves with longer hospitalization, greater costs in addition to higher mortality and morbidity rates due to invasive MRSA infection .
Thus, rapid and reliable detection and identification tests is an important infection control policy method and might help the clinician to reduce the use of inappropriate therapy, preventing the dissemination of this microorganism.
In Morocco few data are available concerning the MRSA frequency in hospitals or community. This study aims to assess the MRSA frequency in the central region of Morocco comparing the standard phenotypic methods and PCR method to differentiate S. aureus from CoNS.
One hundred forty one isolates, among them sixty two Staphylococcus, were collected from hospital bacteriological laboratories in Fes-Meknes region during a period of three months (1st July to 30th September 2010).
Identification of staphylococcal isolates
The isolates were identified morphologically and biochemically by standard laboratory procedures. The coagulase plasma test was performed on organisms exhibiting typical Staphylococcal colony morphology to allow discrimination of S. aureus from coagulatenegative Staphylococci .
Staphylococcus antibiotic susceptibility testing
Resistance to β-lactams (including methicillin) is assessed by Cefoxitin disk (FOX 30 μg). In addition, susceptibility to fourteen other antibiotics were determined by the agar disk diffusion method. Antibiotics tested are listed: cefoxitin (FOX), vancomycin (VA), teicoplanin (TEC), amikacin (AN), tobramycin (TM), netilmecin (NET), erythromycin (E), lincomycin (L), tertacyclin (TE), chloramphenicol (C), ciprofloxacin (CIP), rifampecin (RA), corticomoxasol (SXT), fosfomycin ( FOS), fusidic acid (FA) .
DNA extraction and polymerase chain reaction (PCR)
Staphylococcal colonies were emulsified in 100 μl sterile distilled water to produce a heavy suspension, and heated at 100°C for 15 min, then centrifuged at 12.000 rpm for 10 min.
Multiplex-PCR was performed to detect mecA gene and S. aureus 16S RNA using the reported primers .
Bacterial isolates and identification
During a period of three months (from July to September 2010) 241 isolates were collected from hospital laboratories of Fes–Meknes region and routinely identified by standard laboratory procedures. We focused our analysis on Staphylococcus group as they occupy the second place, just after Enterobacteriaceae with more than 25%, in routinely isolated bacteria from different infection diseases (Table 1 and Figure 1).
Table 1: Percentage of different isolates.
Distribution of staphylococcal samples
We examined sixty two gram-positive bacteria isolated from different type of human physiological liquid. As showed in table 2, Staphylococcus bacteria can be isolated from various kinds of human fluid demonstrating its ubiquitous localization. The pus secretions are the most affected (35.48%) followed by urinary samples (30.64%) shown in Figure 2.
Table 2: Percentage of samples.
Fifteen different antibiotics were tested. Staphylococcus isolates susceptibility rates are showed in table 3. Resistance to cefoxitin is over 36%. The higher rate is detected for tetracyclin (46%) followed by erythromycin (40%) and fusidic acid (33%). The lower resistance rate was reported for amikacin and chloramphenicol (3%) wile lincomycin exhibited 100% susceptibility. For vancomycin and teicoplanin apparent resistance was detected by agar disc diffusion method. The CMI test for vancomycin has been carried out, and these isolate were classed vancomycin susceptible with CMIs of 1 mg/L or 0.5 mg/L. revealing their sensitivity (Table 4).
Table 3: Antibiotics susceptibility of Staphylococci isolated.
Table 4: CMI Determination for vancomycin.
PCR detection of mecA gene and 16S RNA
A sub-site of 30 Staphylococcus isolates were selected on the basis of their antibiotic resistance profiles to be further characterized by multiplex-PCR to assess the presence of mecA gene and S. aureus 16S-RNA to confirm the MRSA strains. A sample of multiplex-PCR products are shown by Figure 3. The two genes are detected in 25 isolates and which is then a MRSA. Others isolates presenting only one segment are mecA positive (case of meticillin resistant CoNS) or S. aureus meticillin sensitive (SAMS).
The obtained results were compared with coagulase test and the cefoxitin susceptibility. These two tests are used in routine procedures to identify MRSA.
Among the 30 Staphylococcus 17 were coagulase positive and then considered as S. aureus strain and the remained 13 isolates were belonging to CoNS group. Eleven isolates were resistant to cefoxitin (Ф ≤ 24 mm) and one was an intermediary phenotype (Ф = 25 mm).
S. aureus 16S RNA was detected by PCR in 17 isolates which is in correlation with the coagulase test [10,11]. mecA gene was detected in 13 isolates only two among them showed S. aureus species specific segment, and then are MRSA strains. Hence, the frequency of mecA gene in S.aureus estimated at 11.76% is relatively low (2/17) compared to CoNS group which showed very high prevalence with 84.61% (11/13). The CoNS isolates are becoming the main source for dissemination of mecA gene.
Although the analyzed Staphylococcal isolates sample is small, our study revealed a relatively low prevalence of SARM in this region of Morocco compared to others region of the world .