Staphylococcus aureus: An Emerging Super Bug

Staphylococcus aureus, a catalase-positive, gram-positive cocci-shapted bacteria, has been implicated in hospital acquired infections since the 1950s when the organisms developed a resistant to penicillin. Even during the golden age of antibiotics, about 50% ofS. aureus strains were found to be resistant to penicillin and later penicillian derivative drugs. The organism quickly became resistnat to newer and more powerful antibiotics, such as tertracycline and the aminoglycosides. S. aureus is a member of the family Micrococcaceae which comprises four genera: Micrococcus, Staphylococcus, Planococcus, and Stomatococcus. Staphyolococcus are natural habitants of skin and mucouse membranes of humans. The bacterial can be found throughout the environment from dust to door knobes. It is common even in the most cleanest healthcare facilities. Most species of Staphycococcus are oppertunistic pathogens, S. aureus , however, has been considered a serious bacterial pathogen since the organism developed a resistance to penicillin in the 1950s.

Staphyococcus aureus : Extracellular Enzymes and Toxins

• Coagulase
• Deoxyribonuclease (DNase)
• Beta lactamase (penicillinase)
• Exfoliatins
• Staphylokinase
• Lipase
• Hemolysins
• Leukocidins
• Enterotoxins
• A, B, C, C2, D, E and F
• TSST-1: toxic shock syndrome toxin

Characteristics of the Cell Wall and Surface of S. aureus

• Protein A: binds to antibody molecules which makes the organism resistant to phagocyctosis and fixation of complement
• Capsular polysaccharide: enables the organism to resist phagocytosis
• Peptidoglycan: cell wall consituent which allows the organism to attach to host's cell membranes and resist unfavorable environmental conditions
• Teichoic acid

Web Site Resources on S. aureus
Four Pediatric Deaths from Community-Aquired Methicillin-Resistant Staphylococcus aureus - Minnisota and North Dakota 1997 - 1999. : MMWR 1999 August 20, 1999/48 (32) ; 707 - 710
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HA-MRSA : Methicillin Resistant S. aureus - - Infection Control Fact Scheet from the CDC, Atlanta, GA,

VISA : Vancomycin Resistant - Publication from the CDC on this resistant strain of Staphylococcus aureus.

WHO Emerging Pathogens Report - - 1997 report of vancomycin intermediate resistant S. aureus

Fact Sheet on S. aureus The Doc Shop Mall, Arizona Healthcare Network Web Site

Epidemiology

Epidemiology is the study of how specific infectious agent survives and spreads through a group of susceptible individuals. Commonly, the two ways are through respiratory and digestive system. Handwashing is the single most important method of controlling microbes in clinical setting. Through this, few microbes of no microbes transfer from person to person. It is known as direct contact. Proper Handwashing also control Fomite transmission.

Fomite is source of microbial infection in clinical area. A Fomite is an inanimate object such as fork or plate which is contaminated with infectious agent. During improper handle, it contaminates the person and transmits to another person through the infected person.

Respiratory secretion also a major source of infection material. Microbes present on fingers by direct or indirect contact may also be introduced into eye, nose, and mouth by accidentals touch. This is yet another reason for following strict aseptic technique procedures while handling infectious material.

Most of personal care product such as lipstick has bacteriostatic agents added which impede the growth of contaminating microbes. Therefore, there is no colony observed in lipstick plate. Using of disinfectant is effective against the growth of microbes.

Microbiology Technologist

Observing Under Microscope

Proficient in the study and identification of bacteria, fungus and parasites using sophisticated instrument including microscope. Deal with the detection and confirmation of infectious conditions.

Culturing Plate

Work involves culturing of:

* Stool
* Blood
* CSF
* vaginal swap
* Urine
* Pus
* Sputum

Agar Plate streaked with Microorganism

Identification of microbes and drug testing

Sputum Smear with TB bacilli

Microbiology Lab

On the first day at microbiology lab, the science officer there gave a briefing about the lab’s equipment, the function of the lab itself and the work procedure in the lab. Guidelines given by laboratory technicians about the method of receiving and sending specimens must be followed correctly if doctors would like to provide therapy service, efficient diagnosis to the patients.

Insignificant positive or negative might occur if the specimen is sent in a wrong container, the specimens are sent late and so on. Hence, this might give problem to doctors and they might give wrong diagnosis to patients. Usage of wrong antibiotic may also increase the cost of the hospital and increase of antibiotic resistant in patients. So the doctors and the laboratory staffs must cooperate to give correct result.

The tests that been conducted are cultures and sensitivity tests of blood, body fluid, cerebrospinal fluid, ear swab, eye, corneal, vitreous tap swab, high vaginal swab, endocervical swab, nasal swab, pus swab and aspirate, stool, sputum, tracheal fluid and also urine. There is also CSF for Bacterial Antigen test, microscopic examination and also hospital infection control test. The microscopic examination includes the usage of gram stain, Albert Stain and Ziehl Neelsen stain.Meanwhile the hospital control test includes the settle plates, environmental swab and also sterility tests for autoclave, pharmaceutical.

In general, microbiology laboratory can be divided into 4 sections which are high vaginal swab/antibiotic sensitivity section, blood and urine section, pus section and media room. I observed and went to each of the sections each day, the tasks that was assigned and learnt are processing and culture clinical specimens, blood agar culture using BACTEC 9240, high vaginal swab, urine culture, pus culture, TSI test, antibiotic sensitivity test and nasal and throat swab.

Picture of BECTEC 9240 machine