Chemotherapy of bacterial infections

 

 

·        Septicaemia.

·        Infections of ear, nose, throat.

·        Lung and bronchi.

·        Endocarditis.

·        Meningitis.

·        Infections of the intestines.

·        Infections of the urinary tract.

·        Genital tract infections.

·        Mycobacterial infections.

 

 

Septicaemia

 

Bacterial pathogen

Antibacterial therapy

Septicaemia follows gastrointestinal or genital tract surgery:

·        Escherichia coli

·        Bacteroides.

·        Streptococci.

·        Enterococci.

·        Cefuroxime + metronidazole or

·        Gentamicin + amoxycillin + metronidazole

Septicaemia related to urinary tract infection:

·        Escherichia coli

·        Enterococci

·        Pseudomonas aeruginosa

·        Gentamicin + amoxycillin or

·        Gentamicin + ceftazidime (where pseudonomas aeruginosa is suspected).

Neonatal septicaemia:

·        Streptococci

·        Coliforms

·        Pseudomonas aeruginosa

·        Cefotaxime alone or with netilmicin.

Abscess: staphylococcus septicaemia

·        Flucloxacillin.

Toxic shock syndrome

·        Flucloxacillin.

 

 

Ear, nose and throat

 

Bacterial pathogen

Antibacterial therapy

Sinusitis:

·        Streptococcus pneumoniae

·        Streptococcus pyogenes

·        Haemophilus influenzae

·        Moraxella catarrhalis

·        Oral amoxycillin or

·        Oral doxycycline.

Otitis media:

·        Streptococcus pneumoniae

·        Haemophilus influenzae

·        Moraxella catarrhalis

·        Streptococcus pyogenes

·        Staphylococcus aureus

·        Amoxycillin

Pharyngitis:

·        Streptococcus pyogenes

·        Secondary invaders: streptococcus pneumoniae & Haemophilus influenzae

·        Benzylpenicillin

·        Chemoprophylaxis of streptococcal (Group A) infection: Penicillin V

Vincent’s infection

·        Benzylpenicillin

Diphtheria

·        Antitoxin

·        Erythromycin or benzylpenicillin

Whooping cough

·        Erythromycin

 

 

Lungs and Bronchi

 

Bacterial pathogen

Antibacterial therapy

Bronchitis:

·        Streptococcus pneumoniae

·        Haemophilus influenzae

·        Amoxycillin or

·        Trimethoprim

Segmental or lobar pneumonia:

·        Streptococcus pneumoniae

·        Haemophilus influenzae

·        Benzylpenicillin i.v. or

·        Amoxycillin or

·        Erythromycin

Pneumonia following influenza:

·        Staphylococcus aureus

·        Sodium fusidate + flucloxacillin i.v.

Atypical pneumonia:

·        Mycoplasma pneumoniae

·        Chlamydia psittaci

·        Coxiella burnetii

·        Tetracycline oral

Nosocomial pneumonia:

·        Staphylococcus aureus

·        Streptococcus pneumoniae

·        Pseudomonas aeruginosa

·        Enterobacteriaceae

·        Haemophilus influenzae

·        Initiate ciprofloxacin or ceftazidime until results of sputum culture and bacterial sensitivity are known.

Pneumonia in people with chronic lung disease:

·        Streptococcus pneumoniae

·        Haemophilus influenazae

·        Klebsiella pneumoniae

·        Moraxella catarrhalis

·        Streptococcus & haemophilus: amoxycillin or trimethoprim or co-amoxiclav or a quinolone.

·        Klebsiella: cefotaxime + an aminoglycoside.

·        Moraxella: co-amoxiclav or erythromycin.

Pneumonia in immunocompromised:

·        Enterobacteriaceae

·        Klebsiella spp

·        Pneumocystis carinii

·        Aminoglycoside + amoxycillin until the pathogen is known.

·        Aerobic Gram-negative bacilli: cefotaxime or ceftazidime

·        Pneumocystis: co-trimoxazole

Legionnaire’s disease

·        Erythromycin

Pneumonia due to anaerobic microorganisms:

·        Anaerobic streptococci

·        Bacteroides spp

·        Fusobacterium

·        Cefuroxime + metronidazole

 

 

Endocarditis

 

1.       Common pathogens:

 

a.       Streptococci and staphylococci are causal in 80% of cases with viridans group streptococci, the most common pathogen.

 

b.    In intravenous drug abusers, Staphylococcus aureus is the most likely organism.

 

c.    For culture-negative endocarditis, it is best regarded as being due to streptococci and treated accordingly.

 

2.       Principles of Treatment:

 

a.    High doses of bactericidal drugs are needed because the organisms are difficult to access in avascular vegetations on valves.

 

b.       Drugs should be given parenterally initially and by intravenous bolus injection which achieve the high peak concentrations needed to penetrate the avascular vegetations.

 

c.    The infusion site should be changed every 2 – 3 days to prevent opportunistic infection, which is usually with staphylococci or fungi.

 

d.       Prolonged therapy is needed, usually 4 weeks, and in the case of infected prosthetic valves at least 6 weeks.

 

3.       Drugs used:

 

Bacterial pathogen

Antibacterial therapy

Initial treatment

·        Benzylpenicillin + gentamicin

·        Flucloxacillin + gentamin or sodium fusidate (if staphylococcus aureus is suspected.

Viridans group streptococci

·        Benzylpenicillin + gentamicin

Enterococcus faecalis

·        Benzylpenicllin + gentamicin

Staphylococcus aureus

·        Flucloxacillin + gentamicin i.v. or sodium fusidate oral

Staphylococcus epidermidis

·        Flucloxacillin + gentamicin i.v. or sodium fusidate oral

Coxiella or chlamydiae

·        Tetracycline oral

Fungal endocarditis

·        Amphotericin + flucytosine

Culture-negative endocarditis

·        Benzylpenicillin + gentamicin i.v. for 6 weeks.

 

4.       Prophylaxis:

 

a.       Transient bacteraemia can be provoked by dental procedures, surgical incision of the skin, instrumentation of the urinary tract and parturition.

 

b.       People with acquired or congenital heart defects are at risk of bacteraemia and are protected by antimicrobials prophylactically.

 

c.    The drugs are given as a short course in high dose at the time of the procedure to coincide with the bacteraemia and avoid emergence of resistant organisms.

 

5.       Drugs used for Prophylaxis:

 

Procedure

Antibacterial therapy

Dental procedures

·        Amoxycillin oral 1h before the procedure.

·        Clindamycin oral 1h before the procedure.

Under general anaesthesia

·        Amoxycillin oral and / or with probenecid.

Prosthetic valves / previous endocarditis

·        Amoxycillin i.m or i.v. + gentamicin for induction then amoxycillin oral later.

·        Vancomycin i.v. then gentamicin i.v. or clindamycin over 10min at induction.

 

 

Meningitis

 

1.       Principles of Treatment:

 

a.       Speed of initiating treatment and accurate bacteriological diagnosis are the major factors determining the fate of the patient.

 

b.       When meningococcal disease is suspected, treatment with benzylpenicillin should be started before transfer to hospital.

 

c.       Drugs must be given i.v.

 

2.       Common pathogens:

 

a.       Children and adults: Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae.

 

b.       Neonates: Escherichia coli, Group B streptococci, Listeria monocytogenes.

 

3.       Drugs used in treatment and prophylaxis:

 

Bacterial pathogen

Antibacterial therapy

Neisseria meningitidis

·        Benzylpenicillin or

·        Cefotaxime

·        Hydrocortisone: if there is evidence of adrenocortical insufficiency.

·        Prophylaxis: rifampicin or minocycline.

Streptococcus pneumoniae

·        Cefotaxime or

·        Benzylpenicillin

Haemophilus influenzae

·        Chloramphenicol or

·        Cefotaxime

·        Prophylaxis: rifampicin

Escherichia coli or Group B streptococci

·        Cefotaxime or

·        Ceftazidime

Listeria monocytogenes

·        Ampicillin

 

 

Infecations of the intestines

 

1.       Principles of Treatment:

 

a.       Antimicrobial therapy should be reserved for specific conditions with identified pathogens where benefit has been shown.

 

b.       Maintenance of water and electrolyte balance, either by i.v. infusion or orally with a glucose-electrolyte solution together with an antimotility drug are the mainstay of therapy is such cases.

 

2.       Drugs used:

 

Bacterial pathogen

Antibacterial therapy

Campylobacter jejuni

·        Erythromycin or

·        Ciprofloxacin oral

Shigella

·        Ciprofloxacin or

·        Amoxycillin oral

Salmonella

·        Ciprofloxacin or

·        Amoxycillin or

·        Co-trimoxazole

Typhoid fever

·        Ciprofloxacin or

·        Amoxycillin or

·        Co-trimoxazole

Escherichia coli

·        Ciprofloxacin

Staphylococcus enteritis

·        Vancomycin oral or

·        Flucloxacillin oral or i.v.

Vibrio cholerae

·        Doxycycline

Peritonitis: coliforms, anaerobes & streptococci

·        Gentamicin, amoxycillin + metronidazole or

·        Cefuroxime + metronidazole

 

 

Infection of the urinary tract

 

1.       Common pathogens:

 

a.       Escherichia coli.

 

b.       Proteus spp.

 

c.       Klebsiella pneumoniae.

 

d.       Pseudomonas aeruginosa.

 

e.       Enterobacteriaceae.

 

f.       Staphylococcus saprophyticus.

 

2.       Principles of Treatment:

 

a.       Identification of the causative organisms and of the sensitivity to drugs are important because of the range of organisms and the prevalence of resistant strains.

 

b.    For infection of the lower urinary tract a low dose may be effective, as many antimicrobials are concentrated in the urine.

 

c.       Infections of the substance of the kidney requires the doses needed for any systemic infection.

 

d.       Elimination of infection is hastened by a large urine volume and by frequent micturition.

 

3.    Drug treatment of urinary tract infections:

 

Category

Antibacterial therapy

Lower urinary tract infection

·        Oral cephalosporin: cephalexin or

·        Trimethoprim or

·        Ampicillin

Upper urinary tract infection

·        Gentamicin + amoxycillin i.v. or

·        Cefotaxime i.v.

Recurrent urinary tract infection

·        Trimethoprim

Asymptomatic infection

·        Amoxycillin or a

·        Cephalosporin

Prostatitis

·        Trimethoprim or

·        Ciprofloxacin or

·        Erythromycin

Chemoprophylaxis

·        Nitrofurantoin

·        Nalidixic acid

·        Trimethoprim

 

4.       Nitrofurantoin:

 

a.    Half-life: 30min.

 

b.    A synthetic antimicrobial active against the majority of urinary pathogens except pseudomonads.

 

c.    It is well absorbed from the GI tract and is concentrated in the urine.

 

d.    Main use is now for prophylaxis.

 

e.       Adverse effects: nausea and vomiting, diarrhea, polyneuritis in patients with renal impairment.

 

5.       Fosfomycin:

 

a.       Inhibit cell wall synthesis.

 

b.       Rapidly bactericidal.

 

c.       Active against a broad spectrum of bacteria isolated in urinary tract infections: Escherichia coli, Proteus spp, Klebsiella pneumoniae, Staphylococci and Streptococci.

 

d.    Used to treat uncomplicated urinary tract infections.

 

 

Genital tract infections

 

Bacterial pathogen

Antibacterial therapy

Anogenital gonorrhoea

·        Amoxycillin + probenecid oral.

·        Spectinomycin i.v. or

·        Ciprofloxacin oral

·        Tetracycline: with co-existent chlamydiae infection

Pharyngeal gonorrhoea

·        Tetracycline

Nongonococcal urethritis:

·        Chlamydia trachomatis

·        Ureaplasma urealyticum

·        Tetracycline or

·        Erythromycin oral

Pelvic inflammatory disease:

·        Chlamydiae trachomatis

·        Neisseria gonorrhoea

·        Mycoplasma hominis

·        Metronidazole + doxycycline oral

Syphilis

·        Benzylpenicillin

·        Tetracycline or

·        Erythromycin

Chancroid: Haemophilus ducreyi

·        Erythromycin or

·        Ceftriaxone or

·        Azithromycin

Granuloma inguinale

·        Ampicillin or

·        Co-trimoxazole or

·        Tetracycline

Anaerobic vaginosis:

·        Trichomonas vaginalis

·        Candida albicans

·        Gardnreella vaginalis

·        Bacteroids spp

·        Metronidazole oral

 

 

Eye infections

 

Bacterial pathogen

Antibacterial therapy

Superficial infection:

 

 

·        Chloramphenicol

·        Gentamicin

·        Ciprofloxacin

·        Neomycin

·        Tobramycin

Chlamydial conjunctivitis

·        Tetracycline

 

 

Mycobacterial infections

 

1.       Principles of Therapy:

 

a.    A large number of actively multiplying bacilli must be killed: isoniazid achieves this.

 

b.       Treat persisters, i.e. semidormant bacilli that metabolize slowly or intermittently: rifampicin and pyrazinamide are the most efficacious.

 

c.       Prevent the emergence of drug resistance by multiple therapy to suppress drug-resistant mutants that exist in all large bacterial populations: isoniazid and rifampicin are best.

 

d.       Combined formulations are used to ensure that poor compliance does not result in monotherapy with consequent drug resistance.

 

2.       Treatment Regimens:

 

a.    An unsupervised regiment of daily dosing comprising isoniazid and rifampicin for 6 months, plus pyrazinamide for the first 2 months.

 

b.    A supervised (directly observed) regimen comprising thrice-weekly dosing with isoniazid and rifampicin for 6 months, plus pyrazinamide for the first 2 months.

 

c.    With both above regimens, ethambutol by mouth or streptomycin i.m. should be added for the first 2 months.

 

d.    A less costly, yet effective regimen: supervised daily administration of isoniazid, rifampicin, pyrazinamide and either ethambutol or streptomycin for 2 months followed by 6 months of unsupervised daily isoniazid and thiacetazone.

 

3.       Chemoprophylaxis:

 

a.       Treatment of infected by symptom-free individuals.

 

b.       Justified in children under age of 3 because they have a high risk of disseminated disease.

 

c.       Isoniazid used alone for 6 months may be used since there is little risk of resistant organisms emerging.

 

4.       Pregnancy: drug treatment should never be interrupted or postponed during pregnancy.

 

5.       Meningeal tuberculosis: use isoniazid and pyrazinamide which penetrate well into the CSF.

 

6.       Leprosy:

 

a.       Paucibacillary disease: dapsone and rifampicin for 6 months.

 

b.       Multibacillary disease: dapsone, rifampicin and clofazimine for 2 years.

 

 

Other bacterial infections

 

1.       Burns: sliver sulphadiazine cream.

 

2.    Gas gangrene: prevented by benzylpenicillin.

 

3.       Wounds:

 

a.       Systemic chemoprophylaxis is necessary for several days at least in dirty wounds.

 

b.       Benzylpenicillin is probably the best, but in the case of penetrating abdominal wounds, metronidazole should be added.

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