The prevalence, antibiogram and charecterisation of staphylococcus aureus among thea healthy medical students of sri manakula
DEPARTMENT OF MICROBIOLOGY DSTE PROJECT REPORT (Government of Puducherry) THE PREVALENCE, ANTIBIOGRAM AND CHARACTERISATION OF Staphylococcus aureus INCLUDING M R S A AMONG THE HEALTHY STAFF,MEDICAL STUDENTS AND PATIENTS FROM SRI MANAKULA VINAYAGAR MEDICAL COLLEGE AND HOSPITAL (SMVMCH), PUDUCHERRY NAMES OF THE INVESTIGATORS Principal Investigator DR. J. SHANMUGAM PROFESSOR OF MICROBIOLOGY Co-Investigators DR.R.GOPAL, PROFESSOR OF MICROBIOLOGY MR.S.SENTHIL KUMAR, ASST.PROFESSOR OF MICROBIOLOGY. PERIOD OF STUDY January,2007 to December, 2008 NAME OF THE INSTITUTE SRI MANAKULA VINAYAGAR MEDICAL COLLEGE & HOSPITAL, KALITHEERTHALKUPPAM, MADAGADIPET, PUDUCHERRY-605107
___________________ LIST OF CONTENTS Subjects Page Numbers Title & Introduction Review of Literatures Aims & Objectives Material & Methods Observations & Results Discussion Conclusion Bibliography THE PREVALENCE, ANTIBIOGRAM AND CHARACTERISATION OF Staphylococcus aureus INCLUDING M R S A AMONG THE HEALTHY STAFF,MEDICAL STUDENTS AND PATIENTS OPF OF SRI MANAKULA VINAYAGAR HOSPITAL (SMVMCH), PUDUCHERRY INTRODUCTION Staphylococcus aureus is among the leading Gram positive bacteria (GPB) causing diseases in humans and animals. It is also the leading bacteria in the normal flora of humans especially, in the skin and nasal vestibule. Besides, this bacterial colonization is very common in certain areas in the body namely – axilla, umbilicus, perineal region and mammary folds. Staphylococcus aureus mainly cause opportunistic infections acquired from different sources like patients, hospital staff mainly through their hands and also from their normal flora. The common types of disease caused by Staphylococcus aureus are various types of skin infections including Staphylococcal scalded skin syndrome (SSSS),Osteomyelitis, Meningitis, Pneumonia, Septicemia, Gastroenteritis Staph.aureus is also the leading gram positive bacteria causing the hospital acquired infections, especially in the Intensive care patients. The other gram positive bacteria causing such infections are Enterococcus, Pneumococcus and Coagulase negative Staphylococcus. Due to many invasive procedures among the critically ill patients, the bacteria can cause serious bacterimia leading the septicaermia. The carrier rate of Staphylococcus aureus in the nasal canal among the healthy people range from 20-30%. From the healthy carriers among the hospital health care personnel, there are more chances of spreading from their hands, nose or throat by way of touching, sneezing, talking, coughing etc. Though there are many reports regarding the carrier state of Staphylococcus aureus among the doctors, nurses and other hospital employees there are scanty reports regarding such carrier state among the medical students. To our knowledge there are only two reports from India regarding the carrier state of Staph-aureus and MRSA - both from Karnataka state (Kasturba Medical Colleges at Mangalore & Manipal. The medical students being future doctors will be handling many types of patients within and outside the hospitals. Healthy carrier state of Staph.aureus, including MRSA among the Medical staff, nurses and students is a major problem, as they can disseminate the same to the patients as well as to their colleagues working in the same hospital. Hence the present study aims at understanding the prevalence of the carrier state of Staph.aureus in the anterior nares of Medical and Nursing students who will come in contact with the patients at OPD,Wards,ICUs and in operation theatres, posing potential chances of disseminating the Staph.aureus if proper aseptic precaution and protective measures are not observed. There are more chances of spreading Staph.aureus from their nose to their patients and in particular to immunocompromised ones, to their colleagues in the hospital as well as to the hospital environment by way of breathing, sneezing as well as by their hands contaminated by nose picking or cleaning. The literatures available from various parts of the world have indicated that Staph.aureus including methicillin resistant Staphylococcus aureus (MRSA) are causing serious and fatal infections among the hospitalized patients especially in intensive care facilities. It is well known that throughout the world 20 to 30% of healthy persons are carrying the Staph.aureus in their nose. The available literatures also indicate the wide prevalence rate of MRSA in various countries as – 1-5% in Northern Europe, 5-30% in Southern Europe, 5-40 % in Asian countries & 10-50 % in USA and in UK. The problem of treating such infections are mainly due to the multi-drug resistant nature of MRSA. The effective antibiotics available to treat MRSA infections are the glycolipid antibiotics like vancomycin and teichoplanin. Unfortunately from 1997, vancomycin intermediate resistant Staphylococcus aureus (VISA) andvancomycin resistant Staphylococcus aureus (VRSA) have started appearing in the hospital as well as in the community at large. This type of emergence of multiple drug resistance is a challenging task to the clinicians and surgeons handling serious patients in the ICUs. The mortality rate due to MRSA bacterimia is two times more than that caused by MSSA. Recently few Pharmaceutical manufacturers are trying to produce many new antibiotics to meet the challenging problems created by MRSA infections. Now few new antibiotics are introduced for managing such infections. Exa: Daptomycin, Tigecycline etc. REVIEW OF LITERATURE The discovery of Penicillin opened the green signal in successfully treating the diseases caused by Staphylococcus and Streptococcus. They used to caue high rate of mortality before the antibiotic era. But from 1950s onwards Staphylocococus aurues started showing increasing rates of Penicillin resistance due to beta- lactamases production. Later Methicillin resistant Staph.aureus (MRSA) was reported within one year after the discovery of the antibiotic in 1961. But the importance of MRSA prevalence within the hospital and the related problems in treatment was revealed only during 1980’s due to increased incidences of infection in ICU patients especially the blood stream infections. The available literature indicates the MRSA carrier rate ranges from 5-50% in many countries. The maximum carrier state was found among the UK hospitalized patients (5-50%) followed by USA (10-60%), northern Europe (1-5% ), southern Europe ( 10-30% ) and Asian countries (5-40% ). The MRSA causes various types of serious infections like pneumonia, endocarditis, bacteraemia, septicaemia and meningitis. Since MRSA strains are highly resistant to many group of antibiotics, there is increased rate of morbidity and mortality in ICU facilities as well as in immuno-compromised individuals. The antibiotics of choice for treating MRSA infection are vancomycin followed by teichoplanin. Overuse of vancomycin in many countries already resulted in the development of intermediate resistant (VISA) and fully resistant (VRSA) of MRSA. Recently the carrier state also found among the community, CMRSA. These strains are more susceptible than the hospital acquired MRSA. So, the patient discharged with the carrier state of MRSA spread these bacteria to the community. Simultaneously, natural occurring CMRSA also enter the hospital by the patients getting admitted with MRSA infection or carrier state. Such bi-directional dissemination of MRSA infections is recently understood by possible means of applying latest molecular typing methods. For example EMRSA type 15 & 16 in UK and EMRSA-300 in USA. Nowadays, it is possible to trace the foci of infection in the hospital as well as in the community by advanced molecular technique like pulse field gel electrophoresis (PFGE). The increased prevalence of Staph.aureus including MRSA in the nose of patients and the hospital staff resulted in the rapid dissemination of the same bacteria in various hospital environments and also result in rapid colonisation in the nose and skin of other persons within the hospital. The study carried out by various Workers in India and other countries clearly indicated the serious problems posed by Staph.aureus infections spreading between the patients and between the hospital staff and patients or vice versa. Since there are very few reports regarding the prevalence of Staph.aureus in the nose of Medical students ,we started the proposed study at our hospital to understand the potential problems of such carrier state. PREVALENCE RATES OF STAPH.AUREUS & M R S A AMONG ANTERIOR NOSTRIL OF HEALTHY HOSPITAL WORKERS AND MEDICAL STUDENTS (Reports during 2007 & 2008) Place of study Subjects Staph.aureus References Manipal, India Medi.students 37/157(23.7%) Santosh,DV et al School children 36/200(18.0%) 2/36 (5.6%) Ohuzkaya Artam et al Lagos,Nigeria Medi.students 26/185(14.0%) Adesida SA et al Virginia,USA Medi.students 398/864(46.1%) …… Knighton,HT Hlth.volunteers 34/157(22.0%) Uemura,E et al Univ.students 307/548(56.0%) Lamikanra,A et al Putra,Malysia Foot ballers 60/60(100%) William,JL et al Safat,Kuwait Hlth.hosp.staff 20/130(15.8%) Dimitrov,T et al Ivory Coast Hlth,hosp.staff 269/592(45.4%) 48/269 ( 17.8%) Koffi,CA et al Mangalore,India UG/PG students 34/50(68.0%) 12/50(24.0%) Baliga,S et al Puducherry,India Hlth.hosp.staff 1/57 (1.7 %) Madanraj,S et al Staph.aureus, MRSA and MSSA prevalence among Medical students:
The rate of MRSA among the Staphylococcus isolates ranges from 0-75% while MRSA range from 5-80%. To our knowledge there are only two reports regarding carrier state of MRSA in India in medical students, one from Manipal (157 MBBS students) and the other from Mangalore (50 UG & PG students). The Mangalore study found more carrier rate of Staph.aureus than the Manipal report. There are few more reports regarding the carrier rate of Staph.aureus as well as MRSA among the healthy medical and nursing students – reporting the carrier rate ranging from 14.0% to 100% -ie from Malaysia, Kuwait, Turkey, Nigeria, Japan etc (Table-1). AIMS AND OBJECTIVES (A) To investigate the carrier rate of Staphylococcus aureus in the anterior nares of healthy medical and nursing students at SMVMCH, Puducherry. (B) This will provide useful informations regarding the prevalence of Staph.aureus in the anterior nares of male and females students undergoing Medical and Nursing courses. (C) To find out the resistant rates against various types of antimicrobial agents used for treating Staphylococcus infections. This will help us to understand the prevalence of susceptible and resistant Staph.aureus isolates from the anterior nares of Medical and Nursing students. (C) To characterize the isolates of Staph.aureus in relation to -lactamase production and slime production. Detection of beta-lactamase producing Staph.aureus isolates will help us to understand the problem of treating the infections with Penicillin group of antibiotics and the uses of beta lactam resistant penicillins as well as the combination of beta-lactam inhibitors like Clavulonic acid (Augmentin etc). The detection of slime producing strains of Staph.aureus will help us to Understand the potential characters of Staph.aureus in causing implant associated infections and the related problems. (D) To correlate the relations between -lactamase and slime producing Staphylococcus aureus isolates showing multi-resistance against various antibiotics. The analysis of the phenotypic characters will reveal the possible associations between the beta lactamase production, slime production and antibiotic susceptible or resistant isolate of Staph.aureus. MATERIALS & METHODS (A) SELECTION OF THE VOLUNTARY SUBJECTS:
Healthy medical students not suffering from any upper respiratory tract infection and who have not received any antibiotics for the past 30 days are selected for the present study. After explaining the details of the proposed project, letters of informed consent signed by each student volunteer were obtained. A Proforma including age, sex, health status and relevant data were also collected from each student volunteer (enclosed copy of Consent letter and Proforma details). A total of 188 students comprising 139 medical students and 59 nursing students constituted the voluntary subjects for the proposed study of nasal carrier state of Staphylococcus aureus. The number of students belonging to Medical course and the Nursing course as well as their sex and age groups are given in Tables 2 & 3. Number of Medical and Nursing students who volunteered for the present study Medical students Nursing students Both groups 76 ( 54.7%) ) 14 ( 28.6%) 90 ( 47.9% ) 63 ( 45.3%) ) 35 ( 71.4%) 98 ( 52.1%) Both groups 139 (73.9%) 49 (26.1%) 188 (100 %) Sex and age group of students selected for the nasal carrier state of S. aureus Age group Female (%) 91 (92.8) 172 (91.5) 90 (47.8) 98 (52.2) 188 (100) (B) COLLECTION OF THE NASAL SWAB:
Cotton swabs sterilized by hot air oven at 160C for 1 hour were used for nasal swabbing of the anterior nares of the healthy volunteer students. The swabs were rubbed very well by rotating 5 times over the inner wall of the ala and nasal septum and immediately processed for culture and isolation. (C) CULTURE OF NASAL SWABS: The nasal swabs collected were cultured on Mannitol Salt agar (selective medium for Staphylococcus aureus) within one hour after collection by streaking as per the conventional technique. The culture plates were incubated at 37C for 24-48 hours in the incubator. (D) IDENTIFICATION OF STAPHYLOCOCCUS AUREUS:
The suspected Staphylococcus colonies-yellow colonies showing Mannitol fermentation and non-yellow colonies (mannitol negative) were selected and subject to Gram staining and sub-cultured into nutrient agar slopes. The isolates showing gram-positive cocci in clusters were subjected to coagulase test by slide and test tube technique using undiluted and 1: 6 diluted human plasma respectively. All the coagulase positive staphylococci are stored in duplicate - one set at +4C and another set at -15C to -20C. Later they are sub cultured to carry out varying phenotypic characterisation like Mannitol fermentation, beta lactamase production, slime production and antibiotic susceptibility testing. (E) IDENTIFICATION OF M R S A BY “CHROM AGAR” PLATE METHOD:
For the identification of the M R S A among the isolates of Staphylococcusaureus, the Hi-Media (India) made “HiChrome Me Re Sa HiVeg Agar Base (MV 1674) was used. The media was prepared by mixing 16.67 gm of the dehydrated media into 200 ml of the distilled water. After sterilization by autoclaving, the medium is cooled to around 50-55 C and 2.0 ml of the reconstituted Methicillin solution (reconstituted with 5 ml sterile distilled water into each Methicillin vials having 2.0 mg of Methicillin as per the direction of the supplier ( Hi Media - India), containing 0.8 mg per vial was added and mixed very thoroughly. Thus the final concentration n of Methicllin in the Chrom Agar was 4 ugm / ml. Soon after that the medium was poured into 100 X 18 mm Petri plates and cooled. After checking the plates for sterility by keeping at 37 C overnight the Staph.aureus strains were streaked onto the Hi Chrome Me Re Sa agar and incubated at 35 C for 24 hours. The MRSA only grew on this Hi Chrome Me Re Sa agar, while the MSSA was inhibited on the same agar plate. All cultures showing bright blue colored growth were taken as MRSA positive strains, while all others are recorded as MSSA strains. As controls, all strains were also inoculated on MH Agar and incubated simultaneously. (F) ANTIBIOTIC SUSCEPTIBILITY TESTING: All nasal isolates of Staphylococcus aureus were subjected to in vitro anti-microbial testing method on Muller-Hinton agar, using 2-hour-old nutrient broth culture and HIMEDIA make antibiotic discs as per the method described by Kirby and Bauer (1966). The zone of inhibition around the discs were measured and interpreted as sensitive, moderately sensitive and resistant using the interpretation chart supplied by the antibiotic disc manufacturers (HIMEDIA, Mumbai). (G) DETECTION OF BETA LACTAMASES PRODUCTION:
-Lactamase production was detected by two different methods: Test tube iodometric technique and filter paper technique using 24 hour old culture and 10,000 units/ml of crystalline penicillin as per the method described by Sykes & Mathew (1979). Test tube method: A loopful of heavy inoculum of 24 hours old culture from MH agar was mixed well with 1.0 ml Penicillin solution containing 10000 U per ml.The tubes are left for 60 min.at room temperature, mixing between every 15 minutes. Then 2 drops of 1% soluble starch solution was added followed by one drop of Iodine solution. The tubes are mixed well and the results are recorded as given below: Instant discoloration: Strong positive Discoloration in 1-5 min: Average positive Discoloration in 6 to 10 min: Moderately positive Discoloration in 10-15 min: Weak positive No discoloration Negative All test tubes showing discoloration with in 10 minutes after adding iodine solution is taken as positive for beta lactamase production. Agar Plate method: Staph.aureus was inoculated on MH agar containing 1% soluble starch and incubated at 37 C for 48 hours. Then the plate is flooded with Penicillin solution containing 10000 U per ml and left at RT for 30 minutes. Then the penicillin solution is decanted completely and flooded with 1:5 dilution of iodine solution. After 3-5 minutes the results are recorded as given below: More than 10 mm dia.discoloration around the culture: ++++ Strong positive 5-10 mm discoloration around culture: +++ Average positive 2-4 mm discoloration around culture: ++ Mode.positive 1 mm or discoloration below culture: positive No discoloration around or below culture: - Negative (H) DETECTION OF SLIME PRODUCTION:
All Staphylococcus aureus isolates were subjected to detection of slime production by Congo red agar plate method as described by Freeman et al. Brain heart infusion agar containing 5% sucrose and 0.08% Congo red was used for slime detection. The isolates were streaked to a length of 1.5 cm on Congo red plate (8 isolates on each plate) and incubated at 37 C for 48 hours and the results were recorded as given below: Dry black, crystalline colonies Strong positive Wet, black, non-crystalline colonies Moderate positive Brownish black colonies Weak positive Brownish black colonies Negative Wet, smooth, pink colonies Negative (I) PREPARATION OF VARIOUS REAGENTS & CULTURE MEDIA FOR THE PRESENT STUDY: 1. Iodine solution for beta lactamase detection 2. Starch solution (1% soluble starch in distilled water) 3. Penicillin solution (10000 Units of Crystalline Penicillin in PBS) 4. Human Plasma (1:6 sterile plasma in normal saline) 5. Congo red agar for slime detection 6. MHA and MSA agar (from Hi Media) OBSERVATION & RESULTS A total of 178 out of 188 students ( 94.6 % %) were found to be carriers of Staphylococcal Species, as revealed by the Gram’s staining. Out of them 45 ( 24.0 %) were carriers Staph.aureus and 133 (76.0%) were carriers of Coagulase Negative Staphylococcus. (CONS). The carrier rate of Staph.aureus among the male and female students are nearly same (Table - 4) Prevalence of Staph.aureus among Male and Female students from Medical and Nursing courses Students Both groups 21/76 (27.6%) 11/63 (17.5%) 32/139 (23.0%) 1/14 (7.1%) 12/35 (34.3%) 13/49 (26.5%) Both groups 22/90 (24.4%) 23/98 (23.5%) 45/188 (24.0%) The detection of M R S A among the isolates of the Staph.aureus was carried out using the Hi-Media made “Hi-Chrome Me Re Sa” dehydrated medium in 100 X 18 mm Petri plates. A total of 40 Staph.aureus strains were tested on this medium. The strains were inoculated on this special medium and incubated at 35 C for full 24 hours. The cultures showing bright blue color were taken as MRSA positive and the color less growth were recorded as MSSA strains. A total of 25.0 % Staph.aureus were found to be M R S A in our present study. Maximum MRSA positive strains were found among the Nursing students than the Medical Students (42.1% and 9.5 %,respectively). The details of the results are given in Table- 5 Table – 5 Prevalence of M R S A in the nose among the male and female Medical students from SMVMCH, Puducherry (As detected by Hi-Media made - HiChrome Me Re Sa plate method) Students Both groups 1/15 ( 6.7%) 1/6 (16.7 %) 2/21 ( 9.5 %) 2/6 ( 33.3%) 6/13 ( 46.1 %) 8/19 ( 42.1 %) Both groups 3/21 (14.2 %) 7/19 ( 36.8 %) 10/40 ( 25.0 %) As controls we have also tested 24 numbers of Staph.aureus strains isolated from the wound swabs collected from our hospital patients in order to find out the differences. The results obtained are given below: Patients: Number of isolates tested: Umber of MRSA positive strains: MRSA prevalence rate among the patient’s isolates: 54.2 % The detection of beta-lactamases was carried out with the Staph.aureus and CONS isolate as per the techniques described by Skyes and Mathews(1979). Using both agar diffusion and test tube method. The results obtained in both sexes belonging to Medical and Nursing students are given in Table - 6 Detection rate of beta-lactamases production among the Nasal isolates of Staph.aureus from healthy Medical and Nursing students Students Both groups 18 /21 (85.7%) 9 /11 (81.8%) 27 /32 (84.4%) 8/12 (66.7%) 8 /13 (61.5%) Both groups 18 /22 (81.8%) 17 /23(74.0%) 35/45 (77.8%) By Congo red agar method, we subjected all Staph .aureus and CONS isolates for the production of slime as per the technique described by Freeman et al (1989) Slime producing Staph.aureus strains isolated from the nasal swabs from healthy Medical and Nursing students Students Both groups 10/21 (47.6%) 3/11 (27.2%) 13 /32 (40.6%) 4 /12 (33.3%) 4/13 (30.7%) Both groups 10/22 (45.4%) 7/23 (30.4%) 17/45 (37.7%) Association between Mannitol fermentation and Slime production among the 125 isolates of Staphylococcus form healthy Medical (64) and Nursing students (61)
Med.students Nurs.students Both students Mannitol +ves 34 (53.1%) 17 (27.8%) 51 (40.8 %) Mannitol only +ve 8 (23.5%) 4 (23.5%) 12 (23.5%) Mannitol & Slime 26 (76.5%) 13 (76.5%) 39 (76.5%) Antibiogram: We have tested 23 different types of antibiotics for the susceptibility pattern of Staph.aureus isolates on Mueller-Hinton agar (MHA) plates as per the technique described by Kirby-Bauer (1966).The names of the antibiotics used and the susceptibility patterns Staph.aureus are given in Table- 9. Antimicrobial susceptibility patterns of Staph.aureus isolates obtained from the nasal swabs of healthy Male and Females students Sr.No: Antimicrobial agents Sensitive rates (%) Resistant rates (%) Penicillin Ampicillin Amoxycillin Ticarcillin Oxacillin Ampicillin/Sulbactam Ticacillin/Clavulonic acid 73 Moxifloxacin Ciprofloxacin Levofloxacin Ofloxacin Gatifloxacin Erythromycin Azithromycin Clarithromycin Clindamycin Pristinamycin Fosfomycin Rifampicin Amikacin Streptomycin Vancomycin Teichoplanin ** Moderately sensitive Average of seven types of Penicillins : Sensitive : 51.14% : Resistant : 48.86 % Average of five types of Quinolones : Sensitive : 84.8 % : Resistant : 15.2 % Average of four types of Macrolides : Sensitive : 78.0 % : Resistant : 22.0 %
DISCUSSION Published literatures on Staph.aureus showed a carrier state of 10 to 30 % in normal healthy population. Our results also similar carrier state of 24.6% among our pre-clinical Medical students with 18 to 25 years of age. The rate of carrier state of Staph.aureus in the anterior nares among the boys and girls students are nearly same - 24.4 % 23.5 %, respectively. To our knowledge there are only three published reports regarding the carrier rate of Staph.aureus among the nose of Medical students from India (Two from Manipal and One Mangalore). Compared to our findings, Santhosh et al (2007) from Manipal (India) have found less carrier rate among their Indian Medical students ( 16.6%), while they have also found higher carrier rate of Staph.aureus among the Chinese medical students Adesida,SA et al from Lagos, (Nigeria) have reported as only 14.0% (26/185) of their third year Medical students carrying Staph.aureus in their nose, compared to 22.0% seen among the Medical and Nursing students from Japan (Uemura,E et al,2007). The Medical students and the hospital staff acquire the colonization of Staph.aureus in their nose more and more as their number of years of service in the hospital or as the contact with the hospitalized patients increases. This is a well known fact available from the published reports and especially so with the MRSA prevalence The analysis of the findings obtained in the present study revealed correlation between mannitol fermentation and beta-lactamases production as well as between mannitol fermentation and slime production among the Staphylococcal species isolated from the Medical and Nursing students. 30% correlation was seen with mannitol fermentation and Slime production, while 9.2 % isolates have shown only mannitol fermentation. (Table – 10) Table - 10 Correlation between Slime production and Mannitol fermentation among 130 isolates of Staphylococcal species obtained from the nasal cultures of Medical and Nursing students. Category Numbers + ve or - ve Percentages Both negative Slime only positive Mannitol only positive Both Slime&Mannitol +ve 39 Total Mannitol +ve Total Slime +ve Unlike the correlation between Mannitol fermentation and slime production, the percentage of correlation between beta lactamase production and mannitol fermentation is far less than the previous one (17.0 % only against 30.%). The beta lactamase production was seen in more strain tested than the slime production - 69.2% and 78.5 % respectively ( Tables 10 & 11). Table – 11 Correlation between Beta lactamases production and Mannitol fermentation among 130 isolates of Staphylococcal species obtained from the nasal cultures of Medical and Nursing students. Category Numbers + ve or - ve Percentages Both negative Beta - lactamases positive Mannitol only positive Both Beta.& Mannitol +ve 22 Total Mannitol +ve Total Beta lactamases +ve 102 The rate of carrier state of Staph.aureus in the nose and their Mannitol fermentations obtained with two surveys carried out among the Nursing students are given below. Out of thirteen healthy carriers of Staph.aureus seen among nursing students, 9 of them (69.2 %) got cleared of their carrier state and only four new carriers (30.8 %) were found during the second survey. And 23.1 % of them continue to be healthy carriers of Staph.aureus even after three months (Table – 12). Table - 12 Prevalence of Staph.aureus among the nose of Nursing students on two occasions with an interval of three months
Staph.aureus Mannitol ________________________________________________________________________ Both times positive 3/13 (23.1%) 5/13 (38.5%) Persistent carriers ________________________________________________________________________ Both time negative 32/49 (65.3%) 17/49 (34.7%) Non-carriers ________________________________________________________________________ 2nd time positive 4/13 (30.8%) 2/13 (15.4%) No more carriers ________________________________________________________________________ 2nd time negative 9/13 (69.2%) 1/13 (7.8%) New carriers ________________________________________________________________________
Sindhu et al and Rathinam et al also from Trivandrum reported 90 - 95 % of beta lactamase producers among the Staph.aureus and CONS isolates obtained from the healthy hospital staff and from the patients undergoing cardiac surgery. The slime producing strains also ranged from 55 % to 65 % of the isolates in their study. The prevalence of MRSA among the nose of the healthy Nursing students were found to be far higher than among the Medical students - 42.1 % and 9.5 %, respectively. The prevalence rate among the nursing students was only 12 % less than that seen among the hospital patients (54.2 %). This indicates that there are more chances of cross infections between the hospitalized patients and the nursing students, than the Medical students who spent less time than the nursing students with the hospital patients. Table – 13 Comparison of antibiotic susceptibility pattern of Staph.aureus isolated from healthy hospital staff from Trivandrum (TVM) and healthy Medical student from Puducherry (PDY) Sr.No Name of antibiotics TVM- S Penicillin Ampicillin Erythromycin Amikacin Ciprofloxacin Vancomycin The above Table shows that the antibiotic resistant rates obtained with the isolates of Staph.aureus is more higher in our study than the reports from Trivandrum (Kerala), except with Amikacin and Vancomycin. The resistance rate of Staph.aureus with Erythromycin is nearly same in both the studies. Increased resistant rates were seen with Ampicillin and Ciprofloxacin in our study at SMVMCH.,from Puducherry. CONCLUSION 24.6 % of our second year Medical students are found to be healthy carriers of Staphylococcus aureus in their anterior nares. The carrier rate of Staph.aureus in the nose of male and female medical students are nearly same - 24.4 % and 23.5 % , respectively. The prevalence of M R S A among the three groups – namely healthy Medical students, healthy Nursing students and the infected patients were found to be 42.1 %, 9.5 % and 54.2 % , respectively. The MRSA prevalence rate in the nose of the Nursing students was found to be nearly five time higher than the nose of Medical students. The high prevalence of slime producing Staphylococci (Staph.aureus and Coagulase negative Staphylococci) indicate the potential possibility of acquiring implant associated infections, if they get transmitted from the clinical students or later when they are going to perform their duties as Hospital Doctors to their patients. The in vitro antibiotic susceptibility study indicated that the resistance rate among the isolates of Staphylococci from the healthy carriers among Medical students have shown highly sensitive rate than the clinical isolates (not included in this report) The present findings indicate the potential danger of dissemination of Staph.aureus, including MRSA from Medical students and ,Nursing students to the hospitalized patients The carrier state of Staph.aureus in the nose among the healthy Medical and Nursing students are found to be around 24.5%. There is no marked difference of Staph.aureus carrier rate between males and females or between Medical and Nursing students. The antibiotic susceptibility pattern with the isolates from healthy bcarriers (Medical students) revealed less rate of resistance rates compared to the clinical isolates. The rate of beta lactamase producing strains are found to be more than the slime producing Staph.aureus isolates from the nose of Medical and Nursing students. The present findings underline the importance of carrier state of Staph.aureus among the Medical students and the potentials possibility of hospital acquired infections during their future practice in hospitals. The prevalence of MRSA among them will be of much use in early prevention of nosocomial infections. The prevalence of MRSA carrier rate in the nose of the healthy Nursing students was found to be far higher than the healthy Medical students – 42.1 % and 9.5 %, respectively. The prevalence of MRSA among the Staph.aureus isolates obtained from the cultures of wound swabs (pus cultures) were found to be 54. 2 %. There are more chances of spreading of Staph.aureus, including MRSA from the Medical and Nursing students to the hospitalized patients BIBLIOGRAPHY Bauer, A. W., Kirby, W.M. M., Sherris, J.C. and Turck, M. (1966). 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