Bacterial infections

Acremonium

Acremonium chrysogenum

Cephalosporins made from its cephalosporin C are approved antibiotics for treating and preventing bacterial infections. First-generation drugs act mainly on Gram-positive bacteria such as Staphylococcus and Streptococcus and are used for skin and soft-tissue infections and to prevent surgical infections; later generations reach more Gram-negative bacteria.

Fleming's penicillin mould

Penicillium rubens

Penicillins remain first-line prescription treatment for many bacterial infections, including chest, skin and throat infections, and are used to prevent infection in people with sickle cell disease or without a spleen. Benzylpenicillin and phenoxymethylpenicillin are WHO essential medicines.

Glarea lozoyensis

Glarea lozoyensis

Caspofungin, made semi-synthetically from the fungus's pneumocandin B0, is approved in Europe for invasive candidiasis in adults and children, for invasive aspergillosis that has not responded to or cannot be treated with amphotericin B or itraconazole, and as empirical therapy for suspected fungal infection in febrile, neutropenic patients. It is given only by intravenous infusion in hospital.

Baker's and brewer's yeast

Saccharomyces cerevisiae

A 2017 Cochrane review of probiotics (several species, including S. boulardii) found moderate-certainty evidence that they reduce C. difficile diarrhoea by about 60% in people taking antibiotics, mainly when baseline risk is above 5%. For S. boulardii alone, the reduction was significant in children but not adults.

African nutmeg

Pycnanthus angolensis

In agar tests, the crude sap inhibited Staphylococcus aureus, S. saprophyticus, E. coli, Salmonella typhi and Pseudomonas aeruginosa, but not Proteus mirabilis. Stem bark extract was weakly active against Mycobacterium ulcerans, the cause of Buruli ulcer (MIC 256 µg/ml). The Yoruba use it for skin infections.

African yellow wood

Annickia chlorantha

Traditionally used for typhoid, 'rickettsia fever' and infected wounds. A hydro-ethanolic bark extract inhibited multidrug-resistant E. coli, Klebsiella, Enterobacter and MRSA in the lab (MIC under 100 µg/ml). Its alkaloid columbamine was the most active and made norfloxacin, ciprofloxacin and doxycycline more effective.

Agarikon

Laricifomes officinalis

Used for millennia particularly against pulmonary diseases. Lab studies report activity against Mycobacterium tuberculosis, Yersinia and Staphylococcus aureus, from chlorinated coumarins in the mycelium and lanostane triterpenoids in the fruit body; in one comparison the minimum inhibitory concentrations were very high.

Agarwood

Aquilaria malaccensis

A 2024 scoping review found antimicrobial and anti-inflammatory activity in laboratory studies of agarwood and leaf extracts, but no clinical trials.

Australian sandalwood

Santalum spicatum

In the test tube the essential oil killed Gram-positive bacteria isolated from skin (MIC 15.6–62.5 µg/mL) and inhibited inflammatory enzymes (5-lipoxygenase, phospholipase A2 and cyclooxygenase), without cytotoxicity to skin cells below 500 µg/mL. No human studies were found.

Beard lichen

Usnea barbata

Used as an antiseptic in US and Spanish folk medicine. Extracts are strongly active in the lab against Gram-positive bacteria such as Staphylococcus aureus and Mycobacterium tuberculosis, less so against Gram-negative bacteria and yeasts.

Betel

Piper betle

Leaf extracts and essential oil inhibit bacteria and fungi in the laboratory, which underlies its use as an antiseptic mouthwash in parts of Asia. No clinical trials of infection treatment were found.

Bitter yam

Dioscorea dumetorum

Methanolic extracts of non-edible D. dumetorum showed antibacterial activity in the lab, strongest against Proteus mirabilis.

Black horehound

Ballota nigra

Verbascoside, forsythoside B and arenarioside from the herb had moderate antibacterial activity against Proteus mirabilis and Staphylococcus aureus, including MRSA, in the lab; an extract inhibited MRSA biofilm formation.

Black pepper

Piper nigrum

Extracts and piperine inhibit a range of bacteria in the laboratory, including biofilm formation and bacterial efflux pumps, but this has not been tested in people.

Bushman's grape

Rhoicissus tridentata

Used for sexually transmitted infections; root extracts inhibited Neisseria gonorrhoeae (MIC 0.40 mg/ml), Candida albicans and Gardnerella vaginalis in vitro, and other extracts were active against urinary-tract bacteria.

Cajuput

Melaleuca cajuputi

Leaf extracts inhibited Staphylococcus aureus, Streptococcus agalactiae, Klebsiella pneumoniae and E. coli in vitro.

Cashew

Anacardium occidentale

Anacardic acids, about 65% of cashew nut shell liquid, show antibacterial, antitumour and antioxidant activity in laboratory studies and are explored as lead compounds; there are no clinical trials.

Ceylon ironwood

Mesua ferrea

In Myanmar, flowers are used in traditional remedies; flower extract showed strong antibacterial activity against Proteus vulgaris and Staphylococcus aureus in the laboratory, and coumarins from the plant are being studied against drug-resistant bacteria.

Cheesewood

Pittosporum viridiflorum

Eastern Cape healers use an infusion for opportunistic fungal infections in people with HIV/AIDS, including cryptococcal meningitis. Bark extracts had strong antioxidant activity in vitro, and leaf extracts inhibited Bacillus anthracis (vaccine strain) at 0.08 mg/ml.

China root

Smilax china

Extensively used in Chinese medicine for pelvic inflammatory disease, often alongside antibiotics, as granules, syrups, pills and capsules; the supporting evidence cited is mechanistic (network pharmacology and animal studies).

Chinaroot

Smilax glabra

Syphilis: recorded in the Bencao Gangmu for syphilitic skin lesions and in the Dian Nan Ben Cao as the best medicine for syphilis; listed for syphilis in the Chinese Pharmacopoeia. In a randomised study of 42 patients with persistent positive syphilis serology after treatment, adding the herb to benzathine penicillin raised serological conversion from 24% to 62%. It does not replace antibiotic treatment.

Christmas bush

Alchornea cordifolia

Used in Cameroon for urogenital infections. A leaf water extract was weakly bacteriostatic against E. coli (MIC 1500 µg/ml) and cleared experimental E. coli infection in rats; human data are lacking.

Cuachalalate

Amphipterygium adstringens

Bark extracts and anacardic acids inhibit Helicobacter pylori (the main cause of peptic ulcer) and oral bacteria such as Streptococcus mutans in the lab; activity against H. pylori stayed stable across tree sex and season.

East African greenheart

Warburgia ugandensis

Reviews describe broad antimicrobial activity of extracts against bacteria and Candida in the laboratory, which is attributed to drimane sesquiterpenes. Traditional uses include pneumonia, skin infections and HIV-related opportunistic infections; none has been tested clinically.

Elecampane

Inula helenium

Hydro-ethanolic root extracts and their sesquiterpene lactones (alantolactone, isoalantolactone, igalan) inhibited Staphylococcus aureus in laboratory tests. No studies in people.

Emu bush

Eremophila longifolia

Smoke extracts made in the lab to mimic smoking ceremonies showed significant antimicrobial activity, and the main active compound, (−)-genifuranal, forms only when the leaves are heated. Partly pyrolysed oils were about three or more times as antimicrobial and 30–700 times more antioxidant than fresh oil.

Finger root

Uvaria chamae

Roots are used for infections in southern Benin. Ethanol root extracts inhibited multidrug-resistant Gram-positive bacteria, including MRSA and vancomycin-resistant enterococci, in agar diffusion tests; the activity was linked to ten chalcones and dihydrochalcones. Lab only.

Fish mint

Houttuynia cordata

Used in Chinese medicine for pneumonia and lung abscess, usually in formulas. Extracts are antibacterial against Staphylococcus aureus and other bacteria in the laboratory and reduced lung injury and inflammation in animal models; no controlled human trials of the herb alone were found.

Fish poison tree

Barringtonia asiatica

Methanol extracts of leaves, fruit, seeds, stem bark and root bark showed broad antibacterial and some antifungal activity in the lab. Lab data only.

Ghana quinine

Cryptolepis sanguinolenta

Used traditionally for upper respiratory and urinary infections, septicaemia and tuberculosis; extracts and cryptolepine kill many bacteria in the lab (e.g. E. coli, Salmonella Typhi, Klebsiella), but there are no clinical trials.

Haronga

Harungana madagascariensis

Used in Cameroonian folk medicine for typhoid fever. An aqueous leaf extract cleared Salmonella Typhimurium infection in rats within 10 days at non-toxic doses; leaf, bark and fruit extracts are antibacterial in vitro, including against multidrug-resistant Staphylococcus aureus.

Horsewood

Clausena anisata

Widely used in West Africa for bacterial and fungal skin infections such as boils, ringworm and eczema. An ethanol leaf extract inhibited Gram-positive and Gram-negative bacteria and Candida albicans in the lab at fairly high concentrations (MICs about 0.5–7 mg/ml). No human studies.

Indian spurge tree

Euphorbia neriifolia

Extracts and isolated compounds are active against bacteria, fungi and some viruses in the laboratory; a 2026 study found leaf juice inhibited Pseudomonas aeruginosa from otitis externa in vitro. No clinical studies.

Italian cypress

Cupressus sempervirens

The essential oil (mainly α-pinene and δ-3-carene) and a methanol extract inhibited bacteria such as Klebsiella pneumoniae and removed biofilm from infusion tubing in the laboratory. Laboratory data only.

Kakadu plum

Terminalia ferdinandiana

Fruit and leaf extracts inhibited many bacteria in the lab, including MRSA and β-lactam-resistant strains, and some boosted conventional antibiotics. No studies in people were found.

Kebericho

Echinops kebericho

Used for wound infections, tuberculosis, syphilis and typhoid; root (tuber) extracts showed antibacterial activity in the lab.

Lodh tree

Symplocos racemosa

Bark extracts, especially the flavonoid fraction, inhibited reference bacteria, drug-resistant clinical isolates and biofilms in the laboratory. Test-tube work only.

Mandravasarotra

Cinnamosma fragrans

Used for gastrointestinal infections; the essential oil contains 1,8-cineole and linalool, reported as antimicrobial agents. Laboratory data only.

Mānuka

Leptospermum scoparium

Mānuka honey and oil are antibacterial in the lab, including against antibiotic-resistant bacteria, but trials found the honey no better than standard care for catheter infections or clearing MRSA from the nose.

Masterwort

Peucedanum ostruthium

Root extract was among the most active of 158 extracts against Staphylococcus aureus; ostruthin was identified as the main antibacterial constituent and also inhibited Enterococcus. Laboratory data only.

Mexican oregano

Lippia graveolens

The essential oil is antibacterial in laboratory tests and enhanced the antibiotic imipenem against Pseudomonas aeruginosa and Acinetobacter baumannii in vitro; test-tube data only.

Mountain pepper

Tasmannia lanceolata

Fruit extracts strongly inhibited Proteus mirabilis in the test tube (MIC 11 µg/ml for the methanolic extract, stronger than the control antibiotics in that assay). No human studies.

Muña

Minthostachys mollis

The essential oil inhibited Gram-positive and Gram-negative bacteria in the test tube, and undiluted oil inhibited Candida albicans, though less than fluconazole. No human studies.

Nasturtium

Tropaeolum majus

In a 14-day double-blind crossover study, 3 g daily of nasturtium in 30 healthy women produced urinary benzyl isothiocyanate with a weak antibacterial effect against E. coli and raised urinary beta-defensin 1, without changing the overall gut microbiome.

Oregano

Origanum vulgare

The essential oil and its main constituents carvacrol and thymol are antibacterial, antiviral and anti-inflammatory in laboratory studies; early civilisations used the herb for infectious diseases.

Oriental sweetgum

Liquidambar orientalis

The essential oil showed antibacterial and antibiofilm activity against clinically relevant bacteria in laboratory tests.

Oyster mushroom

Pleurotus ostreatus

In a randomised, double-blind trial in 249 children with recurrent respiratory infections, a chewable pleuran supplement with vitamin D and zinc cut total infections by about 15% and colds by about 19% over 3 months, compared with vitamin D and zinc alone. Both pleuran trials come from the same research group.

Pale purple coneflower

Echinacea pallida

WHO lists Radix Echinaceae (E. angustifolia and E. pallida) for supportive therapy of colds and respiratory and urinary tract infections, attributing the effect to immune stimulation seen in laboratory and animal studies.

Pau d'arco

Handroanthus impetiginosus

Traditionally used for bacterial, fungal and viral infections; bark extracts and naphthoquinones are antibacterial and antifungal in laboratory studies, including against bacteria linked to diarrhoea, and against Giardia in human gut organoids. No clinical trials for infection.

Pennyroyal

Mentha pulegium

The essential oil showed antibacterial (including against Acinetobacter baumannii), anti-quorum-sensing and anti-inflammatory activity in laboratory tests only.

Pepper-bark tree

Warburgia salutaris

Used for respiratory tract infections, tuberculosis and sexually transmitted infections; extracts are antibacterial and antimycobacterial in the lab (e.g. MIC 12.5 µg/ml against Bacillus subtilis). No clinical trials.

Physic nut

Jatropha curcas

Latex 'has long been used to treat infections'; activity is shown only in laboratory tests.

Portia tree

Thespesia populnea

In French Polynesia it is used for boils, pus-filled skin infections and abscesses. A bark extract moderately inhibited Staphylococcus and Streptococcus agalactiae in the laboratory (MIC 0.15–0.30 mg/ml).

Prekese

Tetrapleura tetraptera

Leaf, stem-bark and fruit extracts inhibited various bacteria and fungi in laboratory tests. There are no clinical studies.

Prishnaparni

Uraria picta

Isoflavanones and other compounds isolated from the root inhibited Gram-positive and Gram-negative bacteria and fungi in the laboratory (MIC 12.5–200 µg/ml). Test-tube work only.

Reindeer lichen

Cladonia rangiferina

Compounds isolated from the lichen (abietane diterpenoids and others) showed mild activity against MRSA and vancomycin-resistant enterococci in the test tube; there are no studies in people.

Rhatany

Krameria lappacea

Root extracts inhibited growth and biofilm formation of methicillin-resistant Staphylococcus aureus strains and other Gram-positive bacteria in laboratory studies only.

River red gum

Eucalyptus camaldulensis

Essential oils and leaf and bark extracts inhibited many bacteria and fungi in the laboratory, including multidrug-resistant Acinetobacter baumannii wound isolates (oil MIC 0.5–2 µl/ml), and some combinations with antibiotics were synergistic. These are test-tube results only.

Sacred garlic pear

Crateva religiosa

Ethanol extracts inhibited Candida, Cryptococcus and Aspergillus species in disc-diffusion tests; water extracts did not inhibit Candida. Laboratory only.

Sargent gloryvine

Sargentodoxa cuneata

For pelvic inflammatory disease: a literature review lists several small Chinese randomised trials in which multi-herb decoctions or granules containing hong teng, added to antibiotics, gave higher reported response rates than antibiotics alone. The trials were small, often did not report blinding or drop-outs, and the effect of hong teng itself cannot be separated out.

Shiny bush

Peperomia pellucida

Antibacterial activity is among the most studied effects of the plant's extracts and essential oils, but only in laboratory tests; one isolated sesquiterpene was weakly active against Candida albicans (MIC 512 µg/ml).

Siam weed

Chromolaena odorata

Leaf extracts inhibited Gram-positive and Gram-negative bacteria in the laboratory, including clinical isolates. Test-tube data only.

Sichuan fritillary

Fritillaria cirrhosa

Bulb extract and individual alkaloids inhibited Staphylococcus aureus, Escherichia coli and Moraxella catarrhalis in laboratory tests.

Silver cluster-leaf

Terminalia sericea

Anolignan B, termilignan B and arjunic acid from the root were active against Gram-positive and Gram-negative bacteria (MICs about 2–31 µg/ml), and root extracts against Candida albicans. Test-tube evidence only.

Snake jasmine

Rhinacanthus nasutus

A standardised rhinacanthin-rich extract killed Streptococcus mutans (MIC 4 µg/ml) and inhibited Staphylococcus aureus, S. epidermidis and the acne bacterium in vitro.

Sour fig

Carpobrotus edulis

A crude methanol extract was strongly antibacterial, attributed to flavonoids including rutin, neohesperidin and hyperoside; the extract also inhibited a multidrug efflux pump in cell studies.

Spiked thyme

Thymbra spicata

The essential oil (about 54% carvacrol) inhibited Staphylococcus aureus and Candida parapsilosis and, below inhibitory doses, blocked biofilm formation and quorum sensing in vitro; a separate study reports synergy of extracts with antibiotics against multidrug-resistant S. aureus and Klebsiella.

Sweet chestnut

Castanea sativa

Leaf extracts, chosen because they are used for skin and soft-tissue infections in Italian folk medicine, blocked the quorum-sensing (agr) system that switches on Staphylococcus aureus toxins, in lab assays and a mouse abscess model, without killing the bacteria or provoking resistance. No human trials.

Sweet detar

Detarium microcarpum

Traditionally used for typhoid fever. In rats infected with Salmonella typhimurium, a hydroethanolic root-bark extract cleared the infection and limited damage to blood and organs, both when given at infection and as a curative treatment. Animal studies only.

Syrian rue

Peganum harmala

Extracts and alkaloids are antibacterial, antifungal, antiviral and antiparasitic in lab and animal studies; in hamsters with leishmaniasis, different formulations of harmine cut the parasite load in the spleen by about 40–80%. No clinical trials were found.

Tonka bean

Dipteryx odorata

In the laboratory, an ethanol seed extract with coumarin as its main constituent inhibited several human pathogenic bacteria. A second study found little antibacterial activity: seed extracts were inactive, and husk and endocarp extracts inhibited Pseudomonas aeruginosa only at 2000 µg/ml. Test-tube data only.

Tropical girdlepod

Mitracarpus hirtus

A methanol extract inhibited Staphylococcus aureus (MIC 31.25 µg/ml); isolated gallic acid and 3,4,5-trimethoxybenzoic acid were more potent. A diethyl ether extract inhibited staphylococci from skin infections. Test-tube work only.

Weeping forsythia

Forsythia suspensa

Lignans and phenylethanoid glycosides from the fruit (forsythiaside, phillyrin) are antibacterial, antiviral and anti-inflammatory in laboratory and animal studies; human data are lacking.

White wormwood

Artemisia herba-alba

Its thujone-rich essential oil inhibited a range of bacteria and fungi in laboratory tests. Test-tube work only.

Wild carrot

Daucus carota

Luteolin and its glucosides from the seeds, and components of the essential oil, killed bacteria in the test tube.

Wild thyme

Thymus serpyllum

The essential oil inhibits a broad range of bacteria and fungi in the laboratory (MIC 0.039–0.078%), largely through thymol and carvacrol. Test-tube work only.

Wild verbena

Pentanisia prunelloides

Root and leaf extracts inhibited Gram-positive and Gram-negative bacteria and influenza A virus replication in the laboratory; palmitic acid was isolated as an antibacterial compound.

Winter savory

Satureja montana

The essential oil inhibited pathogenic E. coli isolates at very low concentrations (MIC ≤0.0195–0.156%) and was among the five most active of 98 oils against dormant Candida albicans. Laboratory work only.

Ackee

Blighia sapida

Used for skin and bacterial infections in folk medicine; some extracts were antimicrobial in vitro.

Asiatic toad

Bufo gargarizans

The venom and dried toad skin are used for abscesses and childhood sores in Chinese medicine.

Barbed skullcap

Scutellaria barbata

Chinese medicine practitioners interviewed in Beijing and Nanjing reported using it for infection and inflammation as well as cancer; it is also used for hepatitis, appendicitis and lung abscess. No clinical trials were found for these uses.

Bitter bark

Alstonia constricta

Used by Aboriginal people in Queensland for skin infections.

Broad-leaved croton

Croton macrostachyus

In north-east Ethiopia a cupful of powdered bark with linseed in water is drunk for gonorrhoea.

Buffalo thorn

Ziziphus mucronata

Root preparations are a traditional remedy for gonorrhoea; also used for snakebite.

Chinese goldthread

Coptis chinensis

WHO records traditional use for gastroenteritis and boils; the rhizome and berberine inhibit staphylococci, streptococci and Vibrio cholerae in the laboratory but not E. coli or Salmonella typhi.

Chinese snake gourd

Trichosanthes kirilowii

Pharmacopoeias describe the root as clearing heat, reducing swelling and expelling pus, i.e. for boils and abscesses.

Chong lou

Paris polyphylla

Used in Chinese medicine and by Yunnan folk doctors for boils, carbuncles, abscesses and mumps ('clearing heat and detoxifying').

Common reed

Phragmites australis

The Seminole applied a poultice of the plant to dry up boils and carbuncles (Sturtevant 1954).

Dandelion

Taraxacum officinale

WHO records traditional use for boils, sores, sore throat, lung abscess and urinary infections, uses that correspond to the Chinese pugongying, which is chiefly the related T. mongolicum. Not clinically tested.

Florist's chrysanthemum

Chrysanthemum x morifolium

The Pharmacopoeia lists it for sores and abscess swelling. Its essential oil and extracts inhibit Staphylococcus aureus and acne bacteria in the lab at fairly high concentrations; there is no clinical evidence.

Golden lace

Patrinia scabiosifolia

Chinese tradition uses Bai jiang cao to 'eliminate carbuncle and expel pus' for intestinal abscess (appendicitis), lung abscess, boils and carbuncles; Chinese provincial standards list acute appendicitis and boils. Extracts inhibit bacteria, including methicillin-resistant Staphylococcus epidermidis, in the lab. No controlled trials were found.

Hog plum

Spondias mombin

Frequently used for fever and gonorrhoea in African and American folk medicine.

Japanese honeysuckle

Lonicera japonica

Traditionally used for sores, carbuncles, boils, breast abscess and wound infection; the extracts show antibacterial and antiviral activity in laboratory studies only.

Marula

Sclerocarya birrea

Setswana healers in North West Province, South Africa, use bark and roots for sexually transmitted and vaginal infections; untested.

Noni

Morinda citrifolia

Bark, leaves and green fruit were used for bacterial and fungal infections; the extracts are antimicrobial in laboratory tests only.

Red mangrove

Rhizophora mangle

Used in Caribbean folk medicine as an antiseptic and antifungal; the aqueous extract is antibacterial in lab tests.

Sarsaparilla

Smilax ornata

Syphilis: the Spanish surgeon Pedro Arias de Benavides (1567) recorded Indigenous healers in Guatemala and Mexico giving sarsaparilla water, sometimes with mercury, to induce sweating, followed by sarsaparilla in wine or water for two months. No modern trial has tested it.

Senegal prickly-ash

Zanthoxylum zanthoxyloides

In Uganda the root bark is described as used extensively for malaria and other infections.

Spreading hedyotis

Scleromitrion diffusum

A heat-clearing, detoxifying herb used for inflammatory infections such as appendicitis; anti-inflammatory and antibacterial effects are shown only in laboratory studies.

Voacanga

Voacanga africana

Bark is used for microbial infections. In Cameroon, fruit extracts are used for orchitis and leaf extracts for gonorrhoea.

Zhejiang fritillary

Fritillaria thunbergii

Classically used to 'remove toxicity and disperse abscesses': lung abscess, furuncles, carbuncles and acute mastitis.

Lignum vitae

Guaiacum officinale

Guaiacum wood decoctions were a leading early treatment for syphilis, used by Indigenous Caribbean peoples and adopted in Europe, but the cure proved ineffective and was soon abandoned. Hutten himself improved only temporarily, and modern analysis of his remains suggests he may have had yaws rather than syphilis.