This table is not meant to be a definitive guide for clinical treatment but a general indication of the main antimicrobial actions and thus of the overall usefulness of commonly used antibiotics.
| Gram-Positive Cocci |
| Staphylococcus (boils, infection of wounds, etc.) |
| Non-β-lactamase-producing |
Benzylpenicillin (penicillin G) or phenoxymethylpenicillin (penicillin V) |
A cephalosporin or vancomycin |
| β-lactamase-producing |
A β-lactamase-resistant penicillin (i.e. flucloxacillin) |
A cephalosporin or vancomycin, or a macrolide, or a quinolone |
| Methicillin-resistant |
Vancomycin ± gentamicin ± rifampicin (rifampin) |
Co-trimoxazole, or ciprofloxacin, or a macrolide ± fusidic acid, or rifampicin |
| Methicillin/vancomycin-resistant |
Quinupristin/dalfopristin or linezolid |
|
| Streptococcus, haemolytic types (septic infections, i.e. bacteraemia, scarlet fever, toxic shock syndrome) |
Benzylpenicillin or phenoxymethylpenicillin ± an aminoglycoside |
A cephalosporin, or a macrolide, or vancomycin. |
| Enterococcus (endocarditis) |
Benzylpenicillin + gentamicin |
Vancomycin |
| Pneumococcus (pneumonia) |
Benzylpenicillin or phenoxymethylpenicillin or ampicillin, or a macrolide |
A cephalosporin |
| Gram-Negative Cocci |
| Morasella catarrhalis (sinusitis) |
Amoxicillin + clavulanic acid |
Ciproxafloxacin |
| Neisseria gonorrhoeae (gonorrhoea) |
Amoxicillin + clavulanic acid, or ceftriaxone |
Cefotaxime, or a quinolone |
| Neisseria meningitidis (meningitis) |
Benzylpenicillin |
Chloramphenicol, or cefotaxime, or minocycline |
| Gram-Positive Rods |
| Corynebacterium (diphtheria) |
A macrolide |
Benzylpenicillin |
| Clostridium (tetanus, gangrene) |
Benzylpenicillin |
A tetracycline, or a cephalosporin |
Listeria monocytogenes
(rare cause of meningitis and generalised infection in neonates) |
Amoxicillin ± an aminoglycoside |
Erythromycin ±an aminoglycoside |
| Gram-Negative Rods |
| Enterobacteriaceae (coliform organisms) |
| Escherichia coli, Enterobacter, Klebsiella |
| Infections of urinary tract |
An oral cephalosporin, or a quinolone |
Extended-spectrum penicillin |
| Septicaemia |
An aminoglycoside (intravenous) or cefuroxime |
Imipenem or a quinolone |
|
| Shigella (dysentery) |
A quinolone |
Ampicillin or trimethoprim |
| Salmonella (typhoid, paratyphoid) |
A quinolone or ceftriaxone |
Amoxicillin or chloramphenicol or trimethoprim |
Haemophilus influenzae
(infections of the respiratory tract, ear, sinuses; meningitis) |
Ampicillin or cefuroxime |
Cefuroxime (not for meningitis) or chloramphenicol |
| Bordetella pertussis (whooping cough) |
A macrolide |
Ampicillin |
Pasteurella multocida
(wound infections, abscess) |
Amoxicillin + clavulanic acid |
Ampicillin |
| Vibrio cholerae (cholera) |
A tetracycline |
A quinolone |
Legionella pneumophila
(pneumonia, legionnaires disease) |
A macrolide ± rifampicin |
Helicobacter pylori
(associated with peptic ulcer) |
Metronidazole + amoxicillin + ranitidinec (2-week regimen) |
Clarithromycin + metronidazole |
| Pseudomonas aeruginosa |
| Urinary tract infection |
A quinolone |
Antipseudomonal penicillins |
| Other infections (of burns etc.) |
Antipseudomonal penicillins + tobramycind |
Imipenem ± an aminoglycoside, or ceftazidime |
|
| Brucella (brucellosis) |
Doxycycline + rifampicin |
| Bacteroides fragilis |
| Oropharyngeal infection |
Benzylpenicillin |
Metronidazole or clindamycin |
| Gastrointestinal infection |
Metronidazole, clindamycin |
Imipenem |
|
| Gram-negative anaerobic rods (other than B. fragilis) |
Benzylpenicillin or metronidazole |
A cephalosporin or clindamycin |
| Campylobacter (diarrhoea) |
A macrolide or a quinolone |
A tetracycline or gentamicin |
| Spirochaetes |
| Treponema (syphilis, yaws) |
Benzylpenicillin |
A macrolide or ceftriaxone |
| Borrelia recurrentis (relapsing fever) |
A tetracycline |
Benzylpenicillin |
| Borrelia burgdorferi (Lyme disease) |
A tetracycline |
| Leptospira (Weil's disease) |
Benzylpenicillin |
A tetracycline |
Rickettsiae
(typhus, tick-bite fever, Q fever, etc.) |
A tetracycline |
A quinolone |
| Other Organisms |
| Mycoplasma pneumoniae |
A tetracycline or a macrolide |
Ciprofloxacin |
| Chlamydia (trachoma, psittacosis, urogenital infections) |
A tetracycline |
| Actinomyces (abscesses) |
Benzylpenicillin |
A tetracycline |
| Pneumocystis (pneumonia, especially in AIDS patients) |
Co-trimoxazole (high dose) |
Pentamidine or atovaquone or trimetrexate |
| Nocardia (lung disease, brain abscess) |
Co-trimoxazole |
