text: I[NTRODUCTION]{.smallcaps} {#sec1-1}
  ==========================
  
  As the potent colonizers of skin of humans or animals, *Staphylococcus aureus* can accelerate nosocomial as well as community-acquired infections ranging from skin and soft-tissue infections, which are considered as mild condition, to sepsis, another severe and life-threatening condition.\[[@ref1]\] In a hospital, methicillin-resistant *S. aureus* (MRSA) infections are normally spread out without introducing any surveillance program embedded with control procedures.\[[@ref2]\] In the past couple of years, a significant number of MRSA cases have been noticed worldwide.\[[@ref3]\] From clinical point of view, methicillin resistance is highly significant since a single genetic element can reveal resistance to antibiotics, called beta-lactam antibiotics including penicillins (oxacillin), carbapenems, and cephalosporins.\[[@ref4]\] It has been reported that, the presence of resistance genes determine not only the resistance to antibiotics but also the expression of these genes which are regulated by environment, which can provoke the resistance to antibiotics. *S. aureus*, which has a high resistance pattern against a good number of antibiotics but sensitive to methicillin, is considered as methicillin-sensitive *S. aureus* (MSSA) as well as multidrug-resistant strains of *S. aureus* (MDRSA). In recent years, treatments against MDRSA have become burdensome and less successful.\[[@ref5]\] It has been investigated that a large staphylococcal cassette chromosome, *mec* (SCCmec), mobile genetic element, is found in MRSA\[[@ref6]\] which carries the *mecA* gene to code penicillin-binding protein, PBP2a, to all β-lactams.\[[@ref7]\] Although some previous researches have been conducted on MRSA in Bangladesh using cultural methods, the result is not updated because the antibiotic resistance pattern of nosocomial microorganisms including MRSA and MDRSA has been changed in the last couple of years.\[[@ref8]\]
  
  The present study was conducted to investigate the recent prevalence of MRSA and MDR *S. aureus* from environmental and clinical samples in a hospital and aimed to evaluate their antibiotic resistance pattern.
  
  M[ATERIALS AND]{.smallcaps} M[ETHODS]{.smallcaps} {#sec1-2}
  =================================================
  
  Bacterial isolates {#sec2-1}
  ------------------
  
  A total of 100 swab samples were collected from various sources of different hospitals from Chittagong region in Bangladesh. Most of the samples were collected from skin-infected patients, hospital workers, utensils (such as forceps, sizer, trays, and several equipment used in operation theater), and drain water from hospital drainage line.
  
  Bacteriological investigation {#sec2-2}
  -----------------------------
  
  For initial screening, a loop of each sample was inoculated onto various selected media such as C.L.E.D. agar medium, mannitol salt agar medium, and Baird--Parker agar medium and incubated at 35°C ± 2°C for 24 h. Then, the positive isolates of *S. aureus* on selective medium were subjected to several biochemical tests such as catalase test according to Bergey\'s Manual of Bacteriology.\[[@ref9]\]
  
  Detection of MRSA by oxacillin and cefoxitin sensitivity assays {#sec2-3}
  ---------------------------------------------------------------
  
  After the confirmation of *S. aureus* from cultural method, isolates were tested to identify MRSA by disc diffusion test according to NCCLS guidelines\[[@ref10]\] using Mueller--Hinton agar and standard discs of methicillin (oxacillin) (1 μg) and cefoxitin (30 μg). ATCC culture of *S. aureu*s (43300) was used as a positive control.
  
  Antimicrobial susceptibility test to various drugs {#sec2-4}
  --------------------------------------------------
  
  Standard discs of azithromycin (15 μg), gentamicin (10 μg), tetracycline (30 μg), cefotaxime (30 μg), chloramphenicol (30 μg), and ciprofloxacin (5 μg) were applied to access the sensitivity of *S. aureus* for determining MDRSA. The procedure was performed followed by Kirby--Bauer disc diffusion method according to NCCLS guidelines.\[[@ref10]\] ATCC culture of *S. aureus* (43300) was used as a positive control.
  
  R[ESULTS]{.smallcaps} {#sec1-3}
  =====================
  
  A total of 66 isolates of *S. aureus* were identified from the 100 samples through biochemical and cultural tests. MRSA was determined on the basis of measurement of zone of inhibition produced by oxacillin (\<14 mm) and cefoxitin (\<21 mm).\[[@ref11]\] Fifty-three isolates (83.30%) gave a positive result for oxacillin test and, to avoid any false result, these 53 isolates were again tested by cefoxitin. Finally, 43 isolates (65.15%) gave a positive test for cefoxitin and confirmed as MRSA, whereas 23 isolates (34.85%) were confirmed as MSSA. The whole scenario is presented in [Table 1](#T1){ref-type="table"}.
  
  ###### 
  
  Number of totally identified *Staphylococcus aureus*, methicillin-resistant *Staphylococcus aureus*, and methicillin-sensitive *Staphylococcus aureus*
  
    Source of samples        Number of isolated *Staphylococcus aureus*   MRSA   MSSA
    ------------------------ -------------------------------------------- ------ ------
    Skin infection           9                                            7      2
    Hospital workers         7                                            3      4
    Utensils and equipment   27                                           15     12
    Hospital drain water     23                                           18     5
    Total                    66                                           43     23
  
  MRSA: Methicillin-resistant *Staphylococcus aureus*, MSSA: Methicillin-sensitive *Staphylococcus aureus*
  
  All the isolates of *S. aureus* were subjected to determine their antibiotic resistance pattern, whereas all MRSA showed a high antibiotic resistance and MSSA also revealed antibiotic resistance pattern as MDR *S. aureus*. [Figure 1](#F1){ref-type="fig"} shows the percentage of the antibiotic resistance pattern of total isolated *S. aureus* against different types of antibiotics.
  
  ![Antibiotic resistance pattern of isolated *S. aureus* against different antibiotics. Azi: Azithromycin, Tet: Tetracycline, Gen: Gentamicin, Cip: Ciprofloxacin, Cef: Cefotaxime, Chlo: Chloramphenicol, Cefo: Cefoxitin, and Oxa: Oxacillin](JMAU-6-188-g001){#F1}
  
  D[ISCUSSION]{.smallcaps} {#sec1-4}
  ========================
  
  From this investigation, it was found that most of the isolates of *S. aureus* were resistant to cefoxitin, azithromycin, cefotaxime, tetracycline, gentamycin, chloramphenicol, and ciprofloxacin as both MRSA and MDR were highly potent for spreading nosocomial infection. This is consistent with the findings of Debnath *et al*.\[[@ref12]\] The antibiotic activity of *S. aureus* isolates to beta-lactam antibiotic group members such as penicillin, cefoxitin, and tetracycline was also evident. A remarkable percentage of isolates were resistant to cefoxitin and tetracycline, which was almost similar to the finding of another study.\[[@ref13]\]
  
  In this study, it was noticed that 80.30% and 65.15% of isolates were resistant to oxacillin and cefoxitin, respectively. The feasible reason behind this variation could be the false resistance to oxacillin because of the elevated production of β-lactamase by bacteria.\[[@ref14]\] From molecular point of view, MRSA isolates which have no *mecA* could be phenotypically resistant to methicillin.\[[@ref15]\] It has been reported that *S. aureus*, which does not carry any *mecA* gene, is capable of producing huge amounts of β-lactamase which can make the isolates resistant to oxacillin.\[[@ref16]\] On the contrary, it has been also observed that some *mecA*-positive *S. aureus* were susceptible to both methicillin and oxacillin.\[[@ref17]\] The study by van Griethuysen *et al*. mentioned that the isolates might lost the *mecA* gene during the storage of MRSA isolates.\[[@ref18]\] Previous other studies also suggested that, besides mecA, there are other genes which are also accountable for converting *S. aureus* into MRSA.\[[@ref19]\] Hence, to block the resistance to antibiotics, addition of β-lactamase inhibitors including clavulanic acid or sulbactam could be an effective strategy.\[[@ref20]\]
  
  Several risk practices as well as factors were also noticed which were highly considerable for spreading nosocomial pathogens. Various practices including the use of contaminated needle or forceps, improper disposal of antibiotics in the environment, contaminated dustbins positioned besides to the patient\'s bed, hospital discharges' accumulation into drainage system in hospitals, lack of public awareness, use of unsterilized equipment, and faulty drainage system in hospitals were noticed. These practices are extremely correlated as the independent risk factors for spreading MRSA at higher rate in hospitals. Although the mode of transmission of MRSA is quite similar to other strains of *S. aureus*, their host colonization efficiency is different.\[[@ref21]\] It has been reported that MRSA can be transmitted from animals to humans, humans to animals, and humans to humans by direct and indirect contacts.\[[@ref22]\] As the potential source of contamination, the surface of equipment, which are used for food handling or processing, is also recognized as a potent harbor for microbial growth.\[[@ref23]\] Indiscriminate use of antibiotics is also responsible to develop resistance.\[[@ref24]\] Therefore, we suggested that effective control measures should be implemented to prevent the outbreak of *S. aureus* in hospitals and the surrounding environments.
  
  C[ONCLUSION]{.smallcaps} {#sec1-5}
  ========================
  
  Presence of methicillin and other antibiotics resistant to *S. aureus* indicates risks to public health. Although very few preventive measures are commonly practiced in hospitals, therefore, to minimize the spread of MRSA, the study recommends taking proper measures such as practice of hand hygiene, use of personal protective equipment, disinfection, sterilization, and maintenance of waste disposal system to prevent infectious diseases. It is also highly recommended to ensure auditing on a regular basis to make sure of compliance to infection control measures.
  
  Financial support and sponsorship {#sec2-5}
  ---------------------------------
  
  Nil.
  
  Conflicts of interest {#sec2-6}
  ---------------------
  
  There are no conflicts of interest.
  
  The authors are grateful to Noakhali Science and Technology University, University of Chittagong, and Chittagong Veterinary Animal Science University for supporting us to conduct this research.
  