The present observational prospective study was conducted in the Department of Microbiology and Department of Radiotherapy and Oncology, SN Medical College and Hospital, Agra, Uttar Pradesh, India, from March to August 2018 for six months after obtaining approval from the institutional ethical committee, SN Medical College, Agra vide letter no: IEC/2018/01 dated 06/03/2018.

A written consent was taken from every patients enrolled for the study. The age of patients varied from 43 to 64 years and male female ratio was 3.8: 1. All patients who presented for the first time in oncology OPD and diagnosed as oral cancer and who gave consent for study were included in the study. Those patients who did not consent for the study and had other immune-compromised condition were excluded from the study. A total of 50 participants having oral cancer were screened for colonisation of S. aureus in anterior nare as per standard protocol [4].

First nasal swab sample was collected when patient was enrolled for the study. Based on treatment regimen these patients were divided in to two groups. In chemotherapy group (n=34), second sample was taken after three weeks of chemo treatment and in radiotherapy group (n=16), second sample was taken after 01 cycle (four weeks) of radiotherapy. Nasal swabs were processed as per standard criteria.

Colonies of Staphylococcus aureus were identified by colony morphology and were confirmed by Gram stain, catalase test and slide and tube coagulase test. Strains confirmed as Staphylococcus aureus were tested for resistance to methicillin by disc diffusion technique as per CLSI M100-S24 2017 guidelines using cefoxitin disc (30 microgram), Himedia Laboratory, India. Data was filled and analysed descriptively on Microsoft excel software.

[Table/Fig-1] shows the organism isolated in nasal flora during first time survey. A total of 29 (58%) cases were having Staphylococcus aureus in their nasal cavity out of which 16 (32%) were MRSA [Table/Fig-1]. Fifty patients were divided into two groups according to treatment plan, first group was given chemotherapy (n=34) and second group was given radiotherapy (n=16) [Table/Fig-2].

We only selected those patients for second sample in whom nasal flora had not shown any MRSA bacteria in their first sample. In chemotherapy group of patients, a second sample was taken after giving three weeks of chemotherapy. With the best of our efforts only 14 out of 22 non MRSA cases could be followed rest 5 were lost to follow-up and 3 died.

In radiotherapy group of patients, a second sample from nasal cavity was taken four weeks after radiotherapy. With the best of our efforts only 9 out of 12 non MRSA cases could be followed. Rest 1 was lost to follow-up and 2 died.

Patients in whom nasal flora were not positive for MRSA before chemotherapy, we found that 7 (50%) out of 14 cases have been converted into MRSA. In those patients whose nasal carriage was non MRSA before radiotherapy we found that 3(33.3%) out 9 cases, flora has converted into MRSA [Table/Fig-3].

[Table/Fig-4] shows the change of nasal flora in MRSA from other flora after chemotherapy and radiotherapy. In the present study, 4 (80%) out of 5 MSSA nasal carriage before chemotherapy has been converted to MRSA nasal carriage after three weeks of chemotherapy and surprisingly all (2) cases MSSA nasal carriage before radiotherapy has been converted to MRSA nasal carriage four weeks after first fraction of radiotherapy.

Cancer patients are at risk for developing serious infections. Due to immunocompromised status many times these patients may get infected with normal resident flora and ultimately become infected. In the present study, before starting any treatment modality, 29 (58%) cancer patients were colonised with Staphylococcus aureus out of which 16 (32%) were MRSA strains and 13 (26%) were MSSA. Worldwide many studies showed various prevalence of nasal colonisation in various categories of patients. O’Brien FG et al., studied the colonisation rate of MRSA in two remote communities in Australia and found colonisation rates of 42% and 24% [13]. Saxena S et al., in their study from East Delhi collected a total of 319 nasal swabs from both anterior nares of healthy parents attending a well-baby clinic. Of these, 94 yielded growth of S. aureus (29.4%). Out of these 94 isolates, 17 (18.1%) were MRSA [14].

In a palliative care setting, Ghanem HM et al., found 8.3% prevalence of MRSA [9]. Other studies on palliative care patients found that on admission, 24 of 281 (8.5%) patients tested positive for MRSA [15]. In another study overall prevalence of nasal carriage for MRSA was 4.1% in cancer patients at the time of admission [16]. Srinivasan A et al., in his study in children with cancer found that 0.6% were colonised with MRSA in 2000 and 2.9% in 2006 [17]. Crysandt M et al., in his study on patients with solid or hematological malignancies found that 1.3% were colonised with MRSA in their nasal flora [11]. In a study authors found 6.7% prevalence of MRSA in renal transplant patients [18].

In the present study, we divided our patients into two groups on the basis of therapy given to the patients, one on chemotherapy and another on radiotherapy treatment protocol. In chemotherapy group those patients whose nasal flora were not positive for MRSA before chemotherapy, we found that 7 (50%) out of 14 cases have been converted into MRSA. We also found that 4 (80%) out of 5 MSSA nasal carriage before chemotherapy has been converted to MRSA nasal carriage after three weeks of chemotherapy. Other significant conversions seen were NPG to MRSA in 2 patients and MRCONS to MRSA in 1 case. In radiotherapy group those patients whose nasal carriage was non MRSA before radiotherapy, we found that 3 (33.3%) out 9 cases, flora has converted into MRSA. We also found that 100% of MSSA nasal carriage before radiotherapy has been converted to MRSA nasal carriage four weeks after first fraction of radiotherapy. Other significant conversions seen were MSCONS to MRSA in 1 patient.

In the present study, conversion of nasal flora to MRSA is much higher after chemotherapy than radiotherapy and the difference is statistically significant. Our study suggests that if a patient is colonised with MSSA then there is a high chance that it will be converted to MRSA colonisation after Chemotherapy or Radiotherapy. This study also emphasises that in patients with chronic diseases like cancer if nasal carriage initially showed MSSA then it must be decolonised to avoid its conversion into MRSA and further life-threatening complications like pneumonia and sepsis. The results indicate the need of a prospective study with follow-up of large number of subjects. Overall, chemotherapy caused more conversion of nasal flora to MRSA in comparison to radiotherapy. Present study emphasises that based on treatment protocol, MRSA conversion of nasal flora may differ.

The number of patients included in the present study is less therefore a large prospective case control study should be done to see any role of therapy in conversion of nasal flora in MRSA. Another limitation is that study on genetic level may give more significant correlation. Various risk factors may also be analysed to establish any correlation.

In the current scenario, healthcare associated infection especially MRSA is a serious threat to mankind especially in immunocompromised patients like cancer. Therefore, these group of patients should be screened for presence of MRSA in their nasal flora, if patients nasal flora is showing MSSA initially, it must be taken seriously and should be treated as there is high chance in MSSA flora for development of MRSA following various treatment strategies.