Staphylococcus Saprophyticus

This is mainly seen as UTI’s in young sexually active females. Infected women have pain upon urination (dysuria), pus in urine (pyuria), and bacteria and white blood cells in urine. Patients respond rapidly with antibiotics, such as: amoxicillin – and trimethoprim.

For the following topics use lecture notes as Murray doesn’t offer any notes:

Micrococcus and Stomatococcus

Nosocomial Staphylococcus Infections

Hospital Staphylococci

MRSA

Laboratory Diagnosis (Murray 3^rd Ed. Pg 186)

For a proper diagnosis, a swab from the base of the abscess (per say) should be obtained. Blood cultures are unrewarding due to minute number of organisms for high volumes of blood. Once a swab is sent for culture, they should be put onto sheep blood enriched agar plates for growth. If the swab contains other organisms, then inoculate in agar medium that contains 7.5% NaCl which inhibits growth of other organisms, and also mannitol – important because Staph aureus only ferments it. Within 24 hours, you see the growth of Staphylococci: you see golden appearance if aureus present. Almost all times with S. aureus – you see haemolysins – this is due to the cytolytic toxins (described earlier) that destroy red blood cells.

Diagnosis is done by the appearance of grape like growth and can also be tested for catalase positive reactions, clumping factor, coagulase  for Staph aureus etc). Other methods include: antibiotic susceptibility patterns, biochemical profiles, phage typing (susceptibility to bacteriophages).

Treatment, Prevention (Murray 3^rd Ed Pg 187)

Obviously drug resistance is a major concern in terms of antimicrobial therapy, and this is particularly true for Staphylococci. In Australia, we are at a verge of a major outbreak of resistant organisms – such that antibiotics will become largely useless if used for treatment. The reason for the resistance is because Staphylococci produce penicillinase that break the beta-lactam rings of the antibiotics, which makes them useless and ineffective. The gene that codes for this enzyme is unfortunately transmissible, therefore the spread of resistance is prominent via this pathway. Also, resistance occurs due to the continuous alterations in the binding site for the antibiotic on the bacteria – thus making it quite difficult for drugs to work – unless we constantly develop newer drugs. Synthetic penicillins were developed, but unfortunately this did not contain the spread of resistance.

Treatment for abscesses is to continuously drain them or surgically excise them and have them dressed with sterile products until healing by secondary intention occurs. Prevention is by having good infection control in hospitals, prescribing antibiotics after lab results come – Isolation of patients with these infection to stop spread, screening at admissions, WASH HANDS!

Use of vancomycin is proving to be effective therapy but the organisms are showing signs of resistance to this drug as well. Signs have been widely reported in the US, and signs have also been reported here in Australia.

Category: Microbiology Notes