Let's talk about antibiotics

Antimicrobial stewardship conversations across Northern NSW, Australia

strep pyogenes


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Extrapolating antibiotic susceptibility for streptococci including the pneumococcus

This posting concerns betahaemolytic species of streptococci including S. pyogenes (Lancefield group A strep), S. agalactiae ((group B strep), S. dysgalactiae group (betahaemolytic large colony, groups C or G) (several species included) which are usually associated with pyogenic infection, especially of skin and soft tissue.   S. pneumoniae (the pneumococcus ) is also considered. 

A key misunderstanding about Streptococcus pneumoniae is the significance of penicillin ‘resistance’ and how it is detected.  Oxacillin is used because it provides the best sensitivity for detection of minor elevation of the penicillin minimal inhibitory concentration (MIC) that may be associated with failure of meningitis treatment. Note that benzylpenicillin, ampicillin or amoxycillin remain highly effective therapy for non-meningeal infection (e.g. pneumonia) caused by strains with lowered susceptibility (raised MIC), unless the MIC is (unusually) >=4mg/L when an alternative agent should be selected.   For a useful review of the situation in regards betalactam and macrolide resistance see this 2007 review by Keith Klugman and the paper by Schentag et al referenced below.

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Cipro


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Sparing fluoroquinolones – alternative safe and effective options by syndrome and bug

Fluoroquinolones (ciprofloxacin, norfloxacin and moxifloxacin) have serious potential side effects and are best used only for directed therapy of serious multi-resistant Gram negative infections where no other safer alternatives are available.

14 of our 32 hospital facilities in HNELHD overuse these agents with 2016 average FQ usage above our current benchmark of 30 defined daily doses per 1000 patient-days.

Here are some pointers to situations where better alternatives to FQ exist:

Gram negatives

In hospital practice, FQ are often used for proven susceptible infections due to Pseudomonas aeruginosa,  Enterobacter cloacae and Enterobacter aerogenesSerratia marcescens, Citrobacter freundii, Proteus vulgaris, Providentia species and Morganella morganii (the so called ‘ESCPPM’ group) because there are few or no other oral antibiotic alternatives.

Alternatives:

  • Trimethoprim+sulfamethoxazole is an attractive alternative for ESCPMM organisms as susceptibility is high in HNELHD (avoid this drug in the elderly however).
  • In uncomplicated UTI, use trimethoprim for susceptible ESCPPM group organisms.
  • For non-typhoidal Salmonella infection, use oral amoxycillin or trimethoprim+sulfamethoxazole- local strains are nearly always susceptible to one or both

Always consider whether these organisms are really causing infection since they frequently colonise the skin, respiratory tract,  other mucous membranes and urinary catheters or bladder.

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Cipro


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Ciprofloxacin and other fluoroquinolones: should you think twice about prescribing?

Fluoroquinolones (ciprofloxacin, moxifloxacin and norfloxacin) (FQ) are essential agents for directed treatment of certain types of resistant aerobic Gram negative bacterial species where FQ susceptibility  has been proven.  They are best avoided as empirical  therapy or where there is an alternative due to these potential serious side effects:

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Capture


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Hunter New England Cumulative Antibiogram Updates reflecting 2015 isolate data

Hot of the press – our updated antibiograms with commentaries – revised format.

Some take home messages from these analyses:

  1. Gentamicin retains excellent coverage of aerobic Gram negative bacteria and remains the best choice for empirical Gram negative cover, as reflected in the Australian Therapeutic Guidelines: Antibiotic recommendations.
  2. The proportion of non-urinary isolates of Staph. aureus that are MRSA is driven by outpatient presentations with skin and soft tissue infection and ranged between 14 and 23% across Hunter New England regions (table below). For that reason, it’s important to culture open skin infections for MRSA and use alternative treatment if an antibiotic is indicated and MRSA detected –   oral doxycycline or trimethoprim+sulphamethoxazole are suitable.

Percent MRSA

3. Tetracycline (doxycycline) retains high levels of activity against Streptococcus pneumoniae and Haemophilus influenzae. It is the recommended non-betalactam alternative in mild-moderate community-acquired pneumonia and in those patients with acute on COPD who meet criteria for treatment.

Cumulative antibiograms provide a summary of current bacterial antimicrobial susceptibility for key pathogens in urine and non-urine specimens. The antibiogram reports also include analyses of bloodstream  infections , community and healthcare -associated and key bacterial antibiotic resistances in such events.  Treatment recommendations based on Therapeutic Guidelines, Antibiotic, Edition 15, 2014 are included in each report.

clostridium difficile


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Micro comments: Clostridium difficile testing

Here are our local Pathology North (NSW) comments together with their rationale:

Positive CDI test result comment (no test of clearance required!):

cdp

The duration of contact precautions following recovery are controversial. Patients will continue to excrete C. difficile for weeks following recovery and can represent a cross infection risk. However continent patients with formed stool who are compliant with hand washing represent an acceptable risk. In the setting of an outbreak, it is advisable to extend the post recovery isolation phase, perhaps until the patient is discharged. Continue reading

clostrdiff


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Recurrent community-acquired Clostridium difficile infection (CDI) – what to do?

A call from a local GP last week – 53 year old woman who was given a course of oral amoxycillin+clavulanate for respiratory infection and then developed moderately severe enteritis associated with CT evidence of colitis. Stool testing for C. difficile toxin genes was positive, confirming a diagnosis of CDI. She responded to a 10 day course of oral metronidazole and then relapsed within 1 week of stopping with diarrhoea.  She has no underlying medical conditions and has not been admitted to hospital in the past year.

For the latest management advice,  we would suggest you consult the 2016 Australasian Society of Infectious Diseases updated guidelines for the management of Clostridium difficile infection in adults and children in Australia and New Zealand.  Key points indicate that oral vancomycin is the best second line treatment approach for relapse or for severe infection.  Oral vancomycin is expensive when prescribed privately and it is recommended that discussion with Infectious Diseases occurs so that a public hospital script can be arranged.

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