ABSTRACT
This study was carried out to determine the incidence of Methicillin Resistant Staphylococcus aureus (MRSA) nasal carriage among school pupils of Ikwuano . A total of 100 randomly selected pupils of Divine Vessel of Mercy Academy Nursery/Primary School Oboro Umuariaga and Amawom Community Nursery/Primary School Oboro Amawom both in Ikwuano Local Government of Abia state younger than 12 years were included in the study. Nasal swabs specimens collected were cultured on Mannitol salt agar. S. aureus isolates were identified by mannitol fermentation, coagulase positivity and catalase positivity. Antimicrobial susceptibility test was performed on Meuller-Hinton Agar (MHA) by modified Kirby-Bauer disc diffusion method. Out of the 100 nasal swabs collected, S. aureus was isolated in 60 (60%). Among the isolates, 63.3% (n=38) were from male children whereas 36.7% (n=22) were from female. There was no significant sex difference in colonization of S. aureus between male and female pupils. Out of 60 isolates, 60% (n=39) were MRSA. MRSA isolates showed high rate of resistance towards antibiotics Imipenem (100%) followed by Cefotaxime (90%), Cefoxitin (65%), Azithromycin (55%), Cefuroxime (50%), Ceftriaxone (41.67%), Gentamycin (18.33%), Ciprofloxacin (18.33%), and Lefofloxacin (18.33%).This study showed a high incidence of MRSA carriage in school pupils of Ikwuano indicating the spread of MRSA in the community.
TABLE OF CONTENTS
Title
Page i
Certification ii
Dedication iii
Acknowledgements iv
Table
of Contents v
List
of Tables vii
Abstract viii
CHAPTER ONE: INTRODUCTION 1
1.1 Virulence
Factors of S. aureus 3
1.2 MRSA 3
1.3 Vancomycin Resistant S. aureus 6
1.4 Modes of Transmission 7
1.5 MRSA Colonization 8
1.6 MRSA Infection 8
1.6.1 Bacteremia 9
1.6.2 Endocarditis 9
1.6.3 Metastatic Infections 9
1.6.4 Sepsis 10
1.6.5 Toxic Shock Syndrome 10
1.7 Aims and Objective 10
CHAPTER TWO: LITERATURE REVIEW
11
2.1 Epidemiology of MRSA 12
2.2 Prevalence
of MRSA amongst School Children 12
2.3 Antimicrobial
Evaluation of MRSA Nasal Carriage amongst Healthy Students 13
2.4 Public Health Burden of MRSA in Africa 13
CHAPTER THREE: MATERIALS
AND METHODS 15
3.1 Study Area 15
3.2 Collection of Samples 15
3.3 Preparation of Culture Media 15
3.4 Inoculation and Isolation 15
3.5 Purification
of Isolates 16
3.6 Identification of the Isolates 16
3.7 Gram
Staining 16
3.8 Biochemical Test 17
3.8.1 Catalase Test 17
3.8.2 Coagulase Test 17
3.9 Antibiotic
Susceptibility Testing 17
CHAPTER FOUR: RESULTS 18
CHAPTER FIVE: DISCUSSION
AND CONCLUSION 22
5.1 Discussion 22
5.2 Conclusion 23
References 24
LIST
OF TABLES
|
TABLE
|
TITLE
|
PAGE
|
|
1
|
Isolation of Staphylococcus aureus from school
pupils of Ikwuano
|
19
|
|
2
|
Antibiotic
Susceptibility pattern of the Staphylococcus
aureus Isolates
|
20
|
|
3
|
Methicillin resistance
among Staphylococcus aureus isolates obtained from school pupils of
Ikwuano
|
21
|
CHAPTER ONE
1.0 INTRODUCTION
Staphylococcus.
aureus causes a variety of suppurative infections
and toxinoses in humans. It causes superficial skin lesions such as boils,
styes and furuncules; more serious infections such as pneumonia, mastitis,
phlebitis, meningitis, and urinary tract infections; and deep-seated
infections, such as osteomyelitis and endocarditis. S. aureus is a major
cause of hospital acquired (nosocomial) infection of surgical wounds and
infections associated with indwelling medical devices. S. aureus causes
food poisoning by releasing enterotoxins into food, and toxic shock syndrome by
release of super-antigens into the blood stream (Edward et al., 2013).
Although
methicillin-resistant S. aureus (MRSA) has been entrenched in hospital
settings for several decades, methicillin-resistant S. aureus MRSA
strains have recently emerged outside the hospital becoming known as community
associated- methicillin-resistant S. aureus ( (CA-MRSA) or superbug
strains of the organism, which now account for the majority of staphylococcal
infections seen in the clinic (Emaneini et
al., 2016).
The
primary reservoir of staphylococci is the nares, with colonization also
occurring in the axillae, vulva, pharynx, and other skin surfaces. Nasal
carriage in patient admitted to the hospital is common because close contact
among patients and hospital personnel is not unusual; transfer of organisms
often takes place. Increased colonization in patients and hospital workers
frequently occurs in hospitals. Both hospital and community-acquired infections
caused by drug resistant S. aureus have increased in the past 20 years
(Espinosa-Gongora et al., 2015).
S.aureus
is both a human commensal and a frequent
cause of clinically important infections. It is frequently found on the human
respiratory tract and on the skin. Strains that are associated with disease
often result in infections by producing potent protein toxins, and expressing
cell-surface proteins that bind and inactivate antibodies. The emergence of
antibiotic-resistant forms of pathogenic S. aureus (e.g. MRSA)) is a
worldwide problem in clinical medicine. S. aureus screening, today, is
mainly done to identify methicillin-resistant S. aureus (MRSA) carriers.
The prevalence of methicillin-resistant S. aureus (MRSA) is still quite
low in some parts of the world, such as Northern European countries, but there
is a worldwide increase in the number of infections caused by methicillin-resistant
S. aureus (MRSA) (Emaneini et al.,
2016).
Almost
25% of the Health Care Workers are stable nasal carriers, and 30% to 50% of
them also possess the bacteria on their hands. Health Care Workers that carry S.
aureus in their nares can occasionally cause outbreaks of surgical-site
infections (Agumas et al., 2013).
Most of the invasive S. aureus infections are assumed to arise from nasal
carriage (Calfee et al., 2014).
Staphylococcus
aureus is one of the most important pathogens
worldwide and has emerged as a prominent organism infecting critically ill
persons; the impact of S. aureus infection on human health has
dramatically increased as a result of its remarkable ability to become
resistant to antimicrobials. Because of its primary habitat is moist squamous
epithelium of the anterior nares, most invasive S. aureus infections are
assumed to arise from nasal carriage (Annati et al., 2013). The difference between methicillin-resistant Staphylococcus
aureus (MRSA) and methicillin-susceptible Staphylococcus aureus is resistance
to ß-lactam antibiotics; this is often associated with resistance to multiple
other antibiotics, which limits the therapeutic options (Castro et al., 2016).
National
estimates in the United States from 2000-2002 suggested that the prevalence of S.
aureus and methicilin resistant S. aureus (MRSA) colonization ratios
were 31.6% and 0.84%, respectively. And about 7% or more of patients admitted
to the hospital are colonized with MRSA. Although asymptomatic nasal
colonization with S. aureus is common, it appears to be an important
factor in the development of most infections due to this organism (Ahanjan et al., 2014).
S.
aureus is the most clinically significant species
of staphylococci; S. aureus characteristics gave the reason for their
pathogenicity; which takes many forms. They grow comparatively well under
conditions of high osmotic pressure and low moisture, which partially explains
why they can grow and survive in nasal secretions and on the skin. S. aureus
has been recognized as an important cause of disease around the world and
it has become a major pathogen associated with both hospital and community
acquired infections (De-Boeck et al.,
2015).
1.1 VIRULENCE FACTORS OF S. aureus
S.
aureus expresses many potential virulence
factors: 1- surface proteins that promote colonization of host tissues; 2-
invasins that promote bacterial spread in tissues (leukocidin, kinases,
hyaluronidase); 3- surface factors that inhibit phagocytic engulfment (capsule,
Protein A); 4- biochemical properties that enhance their survival in phagocytes
(carotenoids, catalase production); 5- immunological disguises (Protein A,
coagulase, clotting factor); 6- membrane-damaging toxins that lyse eukaryotic
cell membranes (hemolysins, leukotoxin, leukocidin); 7- exotoxins that damage
host tissues or otherwise provoke symptoms of disease, and 8- inherent and
acquired resistance to antimicrobial agents (Gould, 2010)
1.2 MRSA
Two
kinds of methicillin-resistant Staphylo coccus aureus have been described:
Hospital- associated methicillin-resistant Staphylococcus aureus
(HA-MRSA) and Community-associated methicillin-resistant Staphylococcus
aureus (CA-MRSA). Naturally occurring strains of methicillin-resistant Staphylococcus
aureus were first reported from England in 1961, shortly after the
introduction of semi synthetic penicillins. Within ten years,
methicillin-resistant Staphylococcus aureus was reported in the United
States, with 22 such strains isolated from 18 patients at Boston City
Hospitals. Data gathered between July 2004 and December 2005 by the Active
Bacterial Core Surveillance Network (the laboratory surveillance component of
the Emerging Infections Program of the US Centers for Disease Control and
Prevention (CDC) showed an estimated rate of invasive methicillin-resistant Staphylococcus
aureus infection (bloodstream or other sterile sites) of 31.8 cases per
100,000 population.
Hospital
associated methicillin-resistant Staphylococcus aureus and Community
associated methicillin-resistant Staphylococcus aureus isolates have
been found to be distinct microbiologically, implying that Community associated
methicillin-resistant Staphylococcus aureus did not originate from
Hospital associated isolates that escaped from the hospital setting; rather,
Community associated methicillin-resistant Staphylococcus aureus seems
to have emerged de novo from established Community associated
methicillin-resistant Staphylococcus isolates. A typing scheme
established at the CDC showed that the majority of Community associated
methicillin-resistant Staphylococcus infections are caused by 2
pulsed-field gel electrophoresis types (USA300 and USA400), whereas the predominant
genotypes endemic in hospitals are USA100 and USA200 (Honda et al., 2010).
Additionally,
the infections caused by Hospital associated methicillin-resistant Staphylococcus
aureus and Community associated methicillin-resistant Staphylococcus
are generally different; the Community associated pathogen is most frequently
associated with skin and soft tissue (abscesses, boils, and folliculitis),
whereas HA pathogen is more likely to infect the respiratory tract, blood
stream, urinary tract, and surgical sites. Community associated MRSA is more
frequently susceptible to non B-lactam antibiotics (e.g. clindamycin,
trimethoprim-sulfamethoxazole, and tetracycline), and also tends to be more
aggressive (Khanal et al., 2015)
In
another study to determine nasal carriage of methicillin-resistant Staphylococcus
and its antibiotic susceptibility pattern in adult hospitalized patients and
medical staff in some hospitals in Cameroon the prevalence of nasal carriage of
MRSA in medical staff was 41.3% and 32% for in-patients. The carriage rates of
MRSA at the regional hospital, Limbe, Yaoundé University Teaching Hospital and
Laquintinie Hospital, Douala were 38%, 37.1% and 32.1% respectively. Those who
carried methicillin-resistant Staphylococcus were 34.2% and 35% for
males and females respectively. It was noted that most MRSA strains were highly
sensitive to vancomycin and teicoplanin in patients; while in medical
personnel, most strains were sensitive to clindamycin. In the medical staff,
the highest rate of resistance was recorded with penicillin G,
trimethoprim/sulfamethoxazole and amoxicillin/clavulanic acid; while in the
in-patients the highest rate of resistance was with gentamicin and erythromycin
(Kumar et al., 2011).
According
to a review that looked at Staphylococcus
isolates from Denmark and UK between
1957
and 1960, all early methicillin-resistant Staphylococcus strains
isolated resembled a large group of the early methicillin-resistant Staphylococcus
blood isolates in phenotypic and genetic properties, including phage group,
antibiotype (resistance to penicillin, streptomycin, and tetracycline),
pulsed-field gel electrophoresis pattern, and spaA type and multilocus
sequence type. This strongly suggested that the early methicillin-resistant Staphylococcus
examined here represented the progeny of a strain that served as one of the
first S. aureus recipients of the methicillin-resistance determinant in
Europe.
1.3 VANCOMYCIN RESISTANT S. aureus
Vancomycin
used to be an effective antistaphylococcal agent. Not any more, according to
the current in vitro and clinical data. The concentration required to inhibit
the growth of S.aureus is progressively increasing. Current evidence
provides little hope that increasing the dose or using it in combination with
another antistaphylococcal agent will improve its efficacy. These strategies,
however, require further randomized clinical trials to either reject or
validate them
(Lari
et al., 2011).
Vancomycin-intermediate
S. aureus (VISA) refers to S.aureus that might still respond to
large doses of vancomycin. It is also termed glycopeptide-intermediate
staphylococcus aureus (GISA), implying resistance to all glycopeptide
antibiotics. Vancomycin-resistant S. aureus (VRSA) on the other hand
refers to strains of S.aureus that have become resistant to vancomycin.
These are extremely rare, though people with the following conditions are more
likely to get VISA/VRSA: Underlying medical conditions (such as diabetes or
renal disease), previous infections with methicillin-resistant S. aureus (MRSA),
recent hospitalizations, use of catheters (e.g. IV lines), recent use of
vancomycin or other antibiotics. Detection of VISA is difficult in the
laboratory, and special inquiries about susceptibility testing methods may be
needed (Mamishi et al., 2012).
Reduced
vancomycin susceptibility can occur in S. aureus irrespective of
background methicillin susceptibility and that development of intermediate
vancomycin susceptibility in MSSA may result in increased tolerance to several
classes of anti-staphylococcal agents.The historical U.S. Vancomycin-resistant Staphylococcus
case count and geographical information found 13 cases isolated in different
states (Center for Disease Control and Prevention). The sources included
plantar ulcers, toe wound, urine from a nephrostomy tube, and vaginal swab.
Their underlying medical conditions included diabetes, obesity, vascular
disease, multiple sclerosis, and hypertension and end stage renal disease.
1.4 MODES OF TRANSMISSION
There
are many ways associated with the MRSA transmission; some of these are
associated with surrounding persons and others with the surrounding
environment. Some modes of transmission are:
1-
Person-to-person contact, for example, via transiently colonized hands of
staff.
2-
Fomites such as bed linens or environmental surfaces are not thought to play a
major role in transmission except in special populations, such as patients in
burn units or intensive care units (Halablab
et al., 2010). Contamination of healthcare workers clothing including white
coats, may be a vector for MRSA transmission. A study done on healthcare
workers found that about 23% of healthcare workers white coats were
contaminated with S. aureus of which 18% of them were MRSA. In a study
carried out at University College Hospital Medical School in London, all
medical students coats were bacteriologically contaminated, the most organisms
were Staphylococcus sp including S. aureus. (Navidinia 2015).
3-
Hands of staff appear to be the most likely mode of transmission of MRSA from
patient to patient.
4-
Droplet-borne transmission is less common, but may be important in patients
with tracheotomies who are not able to control their secretions (Ohadian et al., 2015).
1.5 MRSA COLONIZATION
Colonization
is the presence, growth and multiplication of the organism in one or more body
sites without observable clinical symptoms or immune reaction; colonized
patients were considered as a chief source of S. aureus in hospital;
approximately 10% to 40% of people on admission have nasal carriage of S.
aureus. A ''carrier'' refers to an individual who is colonized with MRSA
(Rahimi-Alang et al., 2011). There
are three patterns of carriage.
1-
Persistent carriers: individuals always carry one type of strains, and those
formed about 20% of the carriers and were more common in children than adults.
2-
Intermittent carriers: this pattern shows a large proportion of the population
(60%) and the strains change with varying frequency.
3-
Non carriers: people who almost never carry S. aureus and those are
minorities of people (20%) (Saadat et
al., 2014).
1.6 MRSA INFECTION
Invasion
and multiplication of MRSA in a body site are accompanied by clinical signs and
symptoms of infection (e.g., fever, lesions, wound drainage) or increased white
blood cell count. Infections caused by MSSA and MRSA are growing concern,
particularly among patients in intensive care and surgical units,
immunocompromised patients, and elderly patients in hospitals and nursing homes
(Shahsavan et al., 2012).
S.
aureus infection is a major cause of skin, soft
tissue, respiratory, bone, joint, and endovascular disorders. The majority of
these infections occur in persons with multiple risk factors for infection. The
major diseases caused by S. aureus are:
1.6.1 Bacteremia
The
overall rate of mortality from staphylococcal bacteremia, ranges from 11 to
43%. Factors associated with increased mortality include an age of more than 50
years, non-removable foci of infection, and serious underlying cardiac,
neurologic, or respiratory disease. The frequency of complications from
staphylococcal bacteremia is high, ranging from 11 to 53%. As many as 31% of
patients with bacteremia, who do not have evidence of endocarditis, do have
evidence of metastatic infection. An increasing percentage of bacteremic
infections are related to catheterization (Halablab et al., 2010).
1.6.2 Endocarditis
The
incidence of S. aureus endocarditis has increased and accounts for 25 to
35% of cases, it occurs in intravenous drug users, elderly patients, patients
with prosthetic valves, and hospitalized patients. S. aureus endocarditis
is characterized by a rapid onset, high fever, frequent involvement of normal
cardiac valves, and the absence of physical stigmata of the disease on initial
presentation.
1.6.3 Metastatic Infections
S.
aureus has a tendency to spread to particular
sites, including the bones, joints, kidneys, and lungs. Suppurative collections
at these sites serve as potential foci for recurrent infections. Patients with
persistent fever despite appropriate therapy should be examined for the
presence of suppurative collections
1.6.4 Sepsis
A
minority of bacteremia or local infections progress to sepsis. Risk factors for
sepsis include advanced age, immunosuppression, chemotherapy, and invasive
procedures. S. aureus is one of the most common gram-positive pathogens
in cases of sepsis.
1.6.5 Toxic Shock Syndrome
The
disease is characterized by a fulminant onset, often in previously healthy
persons. The diagnosis is based on clinical findings that include high fever,
erythematous rash with subsequent desquamation, hypotension, and multiorgan
damage (Shakya et al., 2010)
1.7 AIMS AND OBJECTIVES
The
aims and objectives of this project are:
1.
To isolate and characterize Staphylococcus
aureus from the nostrils of school pupils in
Ikwuano.
2.
To determine the antibiotic susceptibility profile of the isolates
3.
To determine MRSA carriage rate among school pupils in Ikwuano.
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