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) and vancomycin 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 160C 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 37C 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 +4C and another set at -15C to -20C. 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
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DR.J.SHANMUGAM,
Professor of Microbiology,
SMV Medical College & Hospital,
Principal Investigator of the Project.
Date: 25th February, 2009.

Source: http://dste.puducherry.gov.in/Dr.J.Shanmugam.pdf