Table 2. Microorganisms found in the oral flora of noma patients by year.

Study	Study details	Organism	Limitations
Falkler, 1999 [38]	Study type: Cross-sectional study Location: Nigeria n: Eight cases Additional details: Cancrum oris lesions (present for six weeks to two years) were cultured for anaerobic microorganisms.	Fusobacterium necrophorum and Prevotella intermedia were isolated from seven and six of the eight lesions, respectively.	Long duration of infection before testing (up to two years), small sample size, no healthy matched comparison group.
Phillips, 2005 [7]	Study type: Case control study Location: Nigeria n: 68 acute noma cases, 63 village and 45 urban controls Additional details: Cases were found over four years through house visits. Controls were matched by age and were children attending out-patient clinics and primary health care centres for routine checks, and had no recent history of any disease, fever and diarrhoea. Oral bacteria were studied by polymerase chain reaction on six cases. Excluded those treated with antibiotics or traditional medicine in last 48hrs. Excluded measles, HIV and malaria comorbid patients.	Bacteria observed at the highest frequencies in noma lesions were Prevotella intermedia (83%), Tannerella for sythensis (83%), Porphyromonas gingivalis (50%), Campylobacter rectus (50%) and Treponema denticola (50%).	Control selection (children attending health care facility) could have biased results as these children were already accessing care. It is unknown how long each patient had noma for. The sample size for bacterial testing was small (n = 6).
Chidzonga, 2008 [96]	Study type: Retrospective chart review Location: Zimbabwe n: 48 acute noma cases, five cases had microbiologic investigations Additional details: All cases presented one to two weeks after onset of symptoms	Staphylococcus aureus, Klebsiella species, group D Streptococcus, and group B hemolytic Streptococcus.	Small sample size, retrospective chart review, no control group.
Baratti-Mayer, 2013 [111]	Study type: Prospective matched, case-control study Location: Niger n: 82 acute noma cases, 327 matched controls Additional details: Study took place over six years. Exact stage of noma cases not defined. Controls matched on age and home village. Extracted total genomic deoxyribonucleic acid. Cases who received antibiotics or whose specimens deteriorated were excluded (n = 20), 117 microbial samples were processed from noma cases and 235 from controls. Multivariable model showed organisms associated with noma.	A reduced proportion of Spirochaeta, Fusobacterium, Capnocytophaga, and Neisseria in the oral microbiota, but an increased proportion of Prevotella associated with noma. Controls had higher Fusobacterium genus levels raising doubts about previous findings.	Controls were significantly older than cases. 28% of observations in the analysis were excluded because of missing data for microbiological variables due to problems collecting data due to poor health.
Huyghe, 2013 [93]	Study type: Case control study Location: Niger n: 84 acute noma cases, 37 acute necrotizing gingivitis cases and 343 controls Additional details: Cases had no antibiotics, no dental cleaning and did not receive fortified food during the 3 previous months. Subjects with lesions older than 4 weeks were excluded.	Compared to the healthy controls, a lower bacterial diversity was found in noma samples. Less Porphyromonadaceae, Tannerella spp., Capnocytophaga spp., Fusobacteria and Cetobacterium spp. were found in noma samples. Raises doubts about Fusobacterium necrophorum.	Authors state need for time series data and the utilization of high-throughput sequencing capacity to elucidate the aetiology of noma.