ANTIBIOTICS choices for common infections Originally published as a supplement with BPJ35
A safe and effective strategy for antibiotic use involves only prescribing an antibiotic when it is needed and selecting an effective agent at the correct dose with the narrowest spectrum, fewest adverse effects and lowest cost.
General principles of antibiotic prescribing:
Only prescribe antibiotics for bacterial infections if:
Symptoms are significant or severe
There is a high risk of complications
The infection is not resolving
Use first-line antibiotics first
Reserve broad spectrum antibiotics for indicated conditions only
The following information is intended to guide selection of an appropriate antibiotic for infections commonly seen in general practice. Individual patient circumstances may alter treatment choices.
Data on national resistance patterns are available from the ESR website: www.surv.esr.cri.nz
Regional resistance patterns may vary slightly, check with your local laboratory.
The information in this guide is correct as at the time of publication (April, 2011).
Many exacerbations are triggered by viruses. Bacteria are often present in purulent sputum and are not an indication of a need for antibiotic treatment. The limited benefit provided by antibiotic treatment is most helpful in patients with severe exacerbations and those with more severe airflow obstruction at baseline.
Amoxicillin 500 mg, three times daily, for five days
Alternatives
Doxycycline 100 mg, twice daily, for five days
Pneumonia – adult
Management
Consider chest x-ray to confirm diagnosis.
Patients with two or more of the following features: age >65yrs, confusion, respiratory rate >30/min, diastolic BP <60mm Hg have a predicted mortality of 10% or higher and admission to hospital should be considered.
Patients can generally be adequately treated with an agent that covers S. pneumonia. Ciprofloxacin should not be used as it does not reliably treat infections due to S. pneumoniae.
Amoxicillin 500 mg – 1.0 g, three times daily, for seven days.
When cover for Mycoplasma pneumoniae or Chlamydophilia pneumonia, is also required add either erythromycin or doxycycline.
Alternatives
Monotherapy with erythromycin, roxithromycin, doxycycline or co-trimoxazole for those with a history of penicillin allergy.
Doxycycline or amoxicillin clavulanate may be considered in post viral/influenza pneumonia where Staphylococcus aureus may be implicated.
Pneumonia – child
Management
Suspect pneumonia if; tachycardia, grunting, in-drawing and high fever in absence of wheeze (auscultatory findings uncommon).
The choice between inpatient or outpatient therapy is dependent on clinical severity. Patients who have systemic toxicity or any indication of respiratory failure should be treated in hospital. If no response to outpatient treatment in 24 to 48 hours, review diagnosis and consider referral to hospital.
Amoxicillin 25 mg/kg, three times daily, for seven days
Alternatives
Erythromycin – particularly in a young child if atypical infections are circulating in the community
Pertussis
Management
Antibiotics are ineffective if given more than seven days after the illness has started. However, use may be justified during the first four weeks of the illness to limit transmission to susceptible contacts.
Community outbreaks of pertussis occur approximately every four years.
Pertussis is a notifiable disease.
Common pathogens
Bordetella pertussis
Antibiotic treatment
First choice
Erythromycin 10 mg/kg (up to 500 mg), four times daily for 14 days
Alternatives
None
Ear, nose and throat
Otitis externa (acute)
Management
Gentle debridement of the ear canal may be necessary to enhance the effectiveness of topical treatment. Suction cleaning is also a safe and effective method of debridement.
Most topical antibacterials are contraindicated in the presence of a perforated drum or grommets.
Clioquinol + flumethasone (Locorten Vioform) 2 to 3 drops, two times daily
or
Dexamethasone + framycetin + gramicidin (Sofradex) 2 to 3 drops, three to four times daily.
Alternatives
Acetic acid 2% (Vosol) may be sufficient in mild cases.
Ciprofloxacin + hydrocortisone (Ciproxin HC) if pseudomonas suspected, e.g. when the onset of illness is related to recent swimming.
If there is spreading cellulitis or the patient is systemically unwell consider oral flucloxacillin or referral to hospital.
Otitis media (acute)
Management
Antibiotic treatment is usually unnecessary.
Consider antibiotics for those at high risk such as children with systemic symptoms, children aged under six months or children aged under two years with severe or bilateral disease.
Otherwise treat symptomatically (e.g. paracetamol) and arrange follow up or give a prescription to be dispensed if no improvement in next 24 hours.
Amoxicillin 40 mg/kg/day in two to three divided doses (up to 1.5 g daily, or 3 g in adults) for five days (seven to ten days if age < two years, underlying medical condition, perforated ear drum, chronic or recurrent infections)
N.B. Some clinicians recommend 80 mg/kg/day to cover Streptococcus pneumoniae resistant strains
Alternatives
Erythromycin, co-trimoxazole or cefaclor
Pharyngitis
Management
Most pharyngitis is of viral origin. The only benefit from treating Streptococcus pyogenes pharyngitis is to prevent rheumatic fever, therefore antibiotic treatment should not be given to people with a low risk of this complication.
There is a significantly increased risk of rheumatic fever if the patient; has a history of past rheumatic fever, is of Maori or Pacific ethnicity, or is resident in a lower socioeconomic area of the North Island, and is aged 3-45 years. Patients who fulfill one or more of these criteria and who have features of group A streptococcus infection; temperature >38°C, no cough, tender cervical nodes, tonsillar swelling or exudates, especially if aged 3-14 years, should have a throat swab cultured and either start empiric antibiotic treatment immediately or if Streptococcus pyogenes is isolated from the swab.
Avoid amoxicillin due to an increased risk of rash if the patient has glandular fever.
Common pathogens
Respiratory viruses, Streptococcus pyogenes
Antibiotic treatment
First choice
Phenoxymethylpenicillin adults 500 mg, twice daily, for ten days, children 20 mg/kg/day in two to three divided doses, for ten days
or
stat IM benzathine 0.6 MU if <27 kg or 1.2 MU if > 27 kg
Alternatives
Erythromycin
Cotrimoxazole does not reliably eradicate pharyngeal carriage and should not be used
Sinusitis (acute)
Management
Most patients with sinusitis will not have a bacterial infection.
The following features increase the likelihood of bacterial infection:
Purulent nasal discharge persisting more than seven days
Amoxicillin 500 mg, three times daily, for seven days (Child 40 mg/kg/day in two to three divided doses)
Alternatives
Doxycycline, co-trimoxazole or cefaclor
If anaerobes suspected, use amoxicillin clavulanate
Eyes
Conjunctivitis
Management
Can be allergic, viral or bacterial. Bacterial is more likely if eyelids are very sticky or symptoms are unilateral. Viral is more likely if symptoms start bilaterally. Most bacterial conjunctivitis is self-limiting and two-thirds of cases improve without treatment in two to five days. In newborns, consider Chlamydia trachomatis or Neisseria gonorrhoeae, in which case topical therapy is inadequate and referral to a paediatrician is recommended.
Assess for keratitis (using fluorescein stain) in contact lens wearers before treating as conjunctivitis.
Less commonly Chlamydia trachomatis or Neisseria gonorrhoeae
Antibiotic treatment
First choice
Topical chloramphenicol until 48 hours after signs of infection have cleared
Alternatives
Topical fusidic acid or topical framycetin
Skin
Bites and clenched fist infections*
Management
Clean and debride wound thoroughly and treat with antibiotic.
Assess need for tetanus immunisation.
Consider referral if bone or joint involvement.
Common pathogens
Polymicrobial infection, Pasteurella multocida, Capnocytophaga canimorsus (cat and dog bites), Eikenella corrodens (fist injury), Staphylococcus aureus, streptococci and anaerobes
Antibiotic treatment
First choice
Amoxicillin clavulanate 500/125 mg, three times daily, for five to ten days
Alternatives
Metronidazole plus either doxycycline or co-trimoxazole
Boils
Management
Most lesions may be treated with incision and drainage alone.
Antibiotics may be considered if fever, surrounding cellulitis or co-morbidity, e.g. diabetes, or if the lesion is in a site associated with complications, e.g. face.
If recurrent boils, e.g. more than ten boils over more than three months, do a nasal swab and if indicated by results, perform staphylococcal decolonisation with a one week course of intranasal mupirocin or fusidic acid. The patient should be advised to shower daily using triclosan body wash, as well as hot drying, ironing or bleaching towels, sheets and underclothes for the duration of treatment. Consider other household contacts.
Common pathogens
Staphylococcus aureus
Consider MRSA if there is a lack of response to flucloxacillin.
Antibiotic treatment
First choice
Flucloxacillin 500 mg, four times daily, for seven to ten days
Alternatives
Erythromycin, co-trimoxazole
Cellulitis
Management
Keep affected area elevated and assess response to treatment. May require referral if severe.
For periorbital cellulitis, in all but very mild cases consider referral for IV antibiotics.
Common pathogens
Streptococcus pyogenes, Staphylococcus aureus, Group C or Group G streptococci
Antibiotic treatment
First choice
Flucloxacillin 500 mg, four times daily, for seven to ten days (the addition of penicillin is not required)
Alternatives
Erythromycin, roxithromycin, cefaclor or co-trimoxazole
Diabetic foot infections
Management
Referral may be required to determine whether infection involves the bones of the feet. If present this requires prolonged treatment with intravenous antibiotics.
Common pathogens
Early infection is usually due to Staphylococcus aureus and/or streptococci. Later infection may be polymicrobial with a mixture of gram-positive cocci, gram-negative bacilli and anaerobes.
Antibiotic treatment
First choice
Amoxicillin clavulanate 500/125 mg, three times daily, for five to ten days
Alternatives
Cefaclor or co-trimoxazole plus metronidazole
Impetigo
Management
Remove crusted area and apply topical antibiotic ointment. Keep affected areas covered and stay away from school or preschool for 24 hours after treatment initiated.
Common pathogens
Streptococcus pyogenes, Staphylococcus aureus
Antibiotic treatment
First choice
Fusidic acid cream for seven days
Alternatives
Flucloxacillin (oral) for seven days for extensive lesions or topical treatment failure
Mastitis
Management
Treat with antibiotic and continue to breast feed from both breasts. This is an important component of treatment and poses no risk to the infant.
Common pathogens
Staphylococcus aureus in lactating women, anaerobes in non-lactating women or in men
Antibiotic treatment
First choice
Flucloxacillin 500 mg, four times daily, for seven days
Alternatives
Cefaclor, erythromycin. Treat non-puerperal mastitis with amoxicillin clauvulanate 500/125 mg, three times daily, for seven days
Gastrointestinal
Campylobacteriosis
Management
Most people will recover with symptomatic treatment only.
Antibiotics have little impact on the duration and severity of symptoms but eradicate stool carriage.
Treatment is indicated for severe or prolonged infection and in pregnant women nearing term. Treatment may also be reasonable in food handlers, childcare workers and those caring for immunocompromised patients.
Campylobacteriosis is a notifiable disease.
Common pathogens
Campylobacter jejuni
Antibiotic treatment
First choice
Erythromycin 250 mg – 500 mg (child 10 mg/kg), three times daily, for five days
Alternatives
Ciprofloxacin
Clostridium difficile colitis
Management
Discontinue or narrow the spectrum of antibiotic treatment when possible. Stopping the antibiotics may lead to clinical resolution of symptoms. Consider referral if evidence of worsening colitis.
Antidiarrhoeals, e.g. loperamide, should be avoided as the toxin may be retained and worsen colitis.
Relapse may occur after treatment.
Common pathogens
Clostridium difficile
Antibiotic treatment
First choice
Metronidazole 400 mg, three times daily, for 10 to 14 days
Alternatives
Vancomycin (hospital treatment)
Giardiasis
Management
Avoid lactose-containing foods for one month after treatment.
Giardiasis is a notifiable disease.
Common pathogens
Giardia lamblia
Antibiotic treatment
First choice
Ornidazole 1.5 g, once daily, for one to two days
or
Metronidazole 2 g (child 30 mg/kg), once daily, for three days
Alternatives
For treatment failure:
Exclude re-infection from asymptomatic family contacts, e.g. children
Use metronidazole 400 mg (child 10 mg/kg), three times daily, for seven days
Salmonellosis
Management
Routine treatment with antibiotics is usually unnecessary and may prolong excretion. Treat in severe disease or immunocompromised patients.
Salmonellosis is a notifiable disease.
Common pathogens
Salmonella enteritidis, Salmonella typhimurium
Antibiotic treatment
First choice
Ciprofloxacin 500 mg, twice daily, for three to five days
Alternatives
Co-trimoxazole (400 + 80 mg tablets), two tablets, twice daily, for three to five days
Travellers’ diarrhoea
Management
Mild cases require symptomatic treatment only such as replacement of fluids. Loperamide may also be used. Antibiotic treatment can be considered for moderate to severe illness. When there are symptoms and signs of invasive infection such as persistent high fever and/or bloody, mucoid diarrhoea, antibiotic treatment should be started after a sample has been sent to the laboratory. Loperamide alone should not be given in such cases.
Common pathogens
Escherichia coli, Campylobacter jejuni, Salmonella and Shigella species
Antibiotic treatment
First choice
Ciprofloxacin 500 mg, twice daily, for three days.
Alternatives
Azithromycin where quinolone resistance is present (South East Asia); or for pregnant women and young children.
Genito-urinary
Cystitis
Management
Non-pregnant women with uncomplicated cystitis do not require a urine culture. However, those who fail to respond to empiric treatment within two days as well as males, children and pregnant women do require a urine culture.
Antibiotic therapy is indicated for all people who are symptomatic. Asymptomatic bacteriuria requires antibiotic treatment in pregnant women but not in elderly women or patients with long-term indwelling urinary catheters.
Treat for longer in pregnant women (seven days) and in men (10 to 14 days). Pregnant women should have repeat urine culture one to two weeks after completing treatment to ensure cure.
Co-trimoxazole 400+80 mg, two tablets, twice daily, for 10 to 14 days or amoxicillin clavulanate 500/125 mg, three times daily, for 10 to 14 days or cefaclor 500 mg, three times daily, for 10 to 14 days
Chlamydia
Management
Sexual partners of a person who has tested positive for chlamydia should also be treated. A test of cure should be done at four weeks post treatment in rectal infection, in pregnant women and when amoxicillin or erythromycin is used.
Repeat STI screen in three months for patients with confirmed chlamydia.
Common pathogens
Chlamydia trachomatis
Antibiotic treatment
First choice
Azithromycin 1 g stat (not licensed for use in pregnancy in New Zealand but clinical experience and studies suggest it is safe and effective)
Alternatives
Doxycycline 100 mg, twice daily, for seven days (do not use in pregnancy or breast feeding) or amoxicillin 500 mg, three times daily, for seven days or if allergic to penicillin, erythromycin ethyl succinate 800 mg, four times daily, for seven days
Gonorrhoea
Management
Sexual partners of a person who has tested positive for gonorrhoea should also be treated. Test of cure is not usually required as standard treatment is >95% effective (provided compliant and asymptomatic after treatment).
As co-infection with chlamydia is very common, azithromycin is also routinely given.
Common pathogens
Neisseria gonorrhoeae
Antibiotic treatment
First choice
Ceftriaxone 250 mg IM stat
and
Azithromycin 1 g stat
(including in pregnancy and breastfeeding)
Alternatives
If the isolate is known to be ciprofloxacin sensitive, a 500 mg stat dose of ciprofloxacin can be used. Resistance rates vary by location.
Trichomoniasis
Management
Sexual partners of a person who has tested positive for trichomoniasis should also be treated, even if asymptomatic. N.B. culture is seldom positive in males even if infection present.
Common pathogens
Trichomonas vaginalis
Antibiotic treatment
First choice
Metronidazole 400 mg, twice daily, for seven days
or
Metronidazole 2 g stat
The single dose has the advantage of improved compliance but there is some evidence to suggest that the failure rate is higher.
Alternatives
In pregnancy and breast feeding use metronidazole 400 mg, twice daily, for seven days.
The single dose regimens are avoided because they may result in higher serum concentrations which can reach foetal circulation.
Bacterial vaginosis
Management
Treatment of asymptomatic woman is unnecessary unless an invasive procedure is planned, e.g. IUCD insertion, termination of pregnancy.
Common pathogens
Gardnerella vaginalis, Bacteroides, Peptostreptococci, Mobilunculus and others
Antibiotic treatment
First choice
Metronidazole 2 g stat
or
Metronidazole 400 mg, twice daily, for seven days
Alternatives
In pregnancy and breast feeding use metronidazole 400 mg, twice daily, for seven days.
The single dose regimens are avoided because they may result in higher serum concentrations which can reach foetal circulation.
Acute non-specific urethritis
Management
Non-specific urethritis is a diagnosis of exclusion. A urethral swab and first void urine sample should be taken to exclude gonorrhoea and chlamydia. Treat sexual contacts.
Common pathogens
Urethritis not attributable to Neisseria gonorrhoeae or Chlamydia trachomatis is termed non-specific urethritis and there may be a number of organisms responsible, e.g. Ureaplasma urealyticum, Mycoplasma genitalium, Trichomonas vaginalis
Antibiotic treatment
First choice
Azithromycin 1 g stat
If purulent discharge, treat as for gonorrhoea, i.e. ceftriaxone 250 mg IM stat and azithromycin 1g stat
Alternatives
Doxycycline 100 mg, twice daily, for seven days
Pelvic inflammatory disease
Management
May include pelvic exam, testing for chlamydia, gonorrhoea and trichomonas, pregnancy test and consider CBC and CRP.
In pregnant women, referral for specialist assessment is indicated. Hospital admission may be required for IV antibiotics.
If a patient has an IUCD, the decision to remove the IUCD should be made depending on individual circumstances. Evidence suggests that treatment of pelvic inflammatory disease can be successful in the presence of an IUCD.
Common pathogens
Chlamydia trachomatis, Neisseria gonorrhoeae and others
Antibiotic treatment
First choice
Ceftriaxone 250 mg IM stat
and
Doxycycline 100 mg twice daily, for two weeks
and
Metronidazole 400 mg twice daily, for two weeks
Alternatives
Azithromycin 1 g stat can be used instead of doxycycline (if chlamydia present) particularly if compliance is likely to be poor
epididiymo-orchitis
Management
Test for chlamydia, gonorrhoea and UTI
Bed rest, analgesics and scrotal elevation are recommended
Common pathogens
Majority due to Chlamydia trachomatis or Neisseria gonorrhoeae. Also E. coli, Bacteroides species, Gardnerella vaginalis, Mycoplasma hominis, Ureaplasma urealyticum, Trichomonas vaginalis, Streptococcus agalactiae and others
Antibiotic treatment
First choice
If STI pathogens suspected:
Ceftriaxone 250 mg IM stat
and
Doxycycline 100 mg, twice daily, for at least two weeks
If UTI pathogens suspected:
Amoxicillin clavulanate 500/125 mg, three times daily for two to three weeks
or
Ciprofloxacin 500 mg, twice daily, for 10–14 days
Alternatives
None
CNS
Bacterial meningitis
Management
Immediately refer suspected cases of meningococcal disease. Give benzylpenicillin or any available parenteral antibiotic before transport to hospital.
Common pathogens
Neisseria meningitidis, Streptococcus pneumoniae
Less common:
Listeria monocytogenes, Haemophilus influenzae
Antibiotic treatment
First choice
Benzylpenicillin 1.2 g (child – 50 mg/kg) IV or IM
Alternatives
Amoxicillin 1 to 2 g (child – 50 to 100 mg/kg) IV or IM
Erythromycin ethyl succinate may be associated with fewer adverse gastrointestinal effects compared to the other salts and the base. Gastrointestinal effects are dose related and appear to be more common in young than in older patients.
Doxycycline
Doxycycline should be taken with food with a full glass of water to avoid oesophagitis. Photosensitivity reactions may occur. Avoid in children (tooth discoloration) and pregnancy.
Cefaclor
Cefaclor has been associated with serum-sickness-like reactions especially in young children, and typically after several courses. Features include skin reactions and arthralgia.
Metronidazole
Avoid alcohol
Flucloxacillin or Phenoxymethylpenicillin
Take at least one hour before meals and at least two hours after meals.
Acknowledgement: Thank you to Associate Professor Mark Thomas, Infectious Disease Specialist, School of Medical Sciences, University of Auckland and Dr Rosemary Ikram, Clinical Microbiologist, MedLab South for expert guidance in producing this booklet.
Bibliography:
Australian Medicines Handbook. Adelaide; Australian Medicines Handbook Pty Ltd, 2006.
British Medical Association and the Royal Pharmaceutical Society. BNF 61. London: Royal Pharmaceutical Society, 2011.
Ellis-Pegler R, Thomas M. Approaches to the management of common infections in general practice. Auckland; Diagnostic Medlab, 2003.
Everts R. Antibiotic guidelines for primary care, Nelson and Marlborough Districts 2007-2008.
Lang S, editor. Guide to pathogens and antibiotic treatment. 7th ed, Auckland; Diagnostic Medlab 2004.
Lang S, Morris A, Taylor S, Arroll B. Management of common infections in general practice: Part 1. NZ Fam Phys 2004;31(3):176-8.
Lang S, Morris A, Taylor S, Arroll B. Management of common infections in general practice: Part 2. NZ Fam Phys 2004;31(4):258-60.
Data on national resistance patterns are available from the ESR website: www.surv.esr.cri.nz
Data on national resistance patterns are available from the ESR website: http://www.surv.esr.cri.nz/PDF_surveillance/Antimicrobial/AR/National_AR_2009.pdf
Regional resistance patterns may vary slightly - check with your local laboratory.