FORMULATION 19
Pluralibacter gergoviae: the bacterium that learns
Barbara Olioso - The Green Chemist
A premium salon shampoo. A mass-market body lotion. A pack of compostable makeup wipes. A bulk-dispensed hand soap. Different companies, different continents, different preservative systems — and the same organism. On 30 June 2026, Kao issued a voluntary recall
of Oribe Serene Scalp Densifying Shampoo across the United States and Canada covering units manufactured in a five-day window in February.1 Nine months earlier,1,312 cases of Neutrogena Makeup Remover Ultra-Soft Cleansing Towelettes were recalled across four US states.2 In early 2025, the UK’s Office for Product
Safety and Standards published a recall of Amika Mirrorball shampoo covering every size and lot code sold in 2023 and 2024.3
In March 2022, Kao
recalled Jergens Ultra Healing Moisturizer, a recall subsequently expanded.4 Four recalls. Three companies. One organism:
Pluralibacter gergoviae. None of these were marginal operations cutting corners. These are manufacturers with functioning quality systems and preservative systems that passed the tests the industry asks them to pass. That is the part worth paying attention to.
The problem: an organism that adapts and is under the radar Pluralibacter gergoviae — reclassified from Enterobacter gergoviae in 20135
— is a Gram-
negative, facultatively anaerobic rod of the Enterobacteriaceae. It lives in soil, water, plant material and in the gut flora of humans and animals. It is everywhere, and it is very comfortable in water. It is a facultative pathogen: in healthy people with intact skin, the risk is low, in immunocompromised consumers, people with chronic illness, surgical patients or anyone with a broken skin barrier, it is a different conversation. The German Federal Institute for Risk Assessment
(BfR - Bundesinstitut für Risikobewertung) is not aware of a single infection caused by the use of a contaminated cosmetic product — and it still concluded that externally applied cosmetics should be free of P. gergoviae.6 That is the most sensible approach because
P. gergoviae is a master of adapation. It exports preservatives. Davin-Regli and colleagues demonstrated in 2006 that P. gergoviae is equipped with efflux pumps that actively transport parabens out of the cell.7
This is not passive tolerance. It is an
export mechanism, and it confers resistance not only to parabens but to other preservatives.
www.personalcaremagazine.com It is resistant above the concentrations the
industry is allowed to use. Périamé, Pagès and Davin-Regli examined 65 isolates from cosmetic products and food sources and tested their susceptibility to preservatives in current cosmetic use.8
The strains isolated from cosmetic samples
suggest that P. gergoviae is an ubiquitous species and that sources of contamination are diverse. Minimum bactericidal concentrations for
several of these preservatives were higher than the maximum concentrations permitted under European legislation. That means some strains can survive preservatives at the maximum permitted level. Synergistic effects were observed when combining two preservatives.
Standard testing blind spot ISO 11930 preservative efficacy testing uses five compendial organisms: Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Candida albicans and Aspergillus brasiliensis. P. gergoviae is not among them. P. aeruginosa is a demanding Gram-negative proxy, but it does
not carry this organism’s specific adaptive profile9 — and a culture collection strain, however well characterised, has not spent two years adapting inside your water system. Release testing has the same blind spot from
a different direction. Total viable count will detect the organism if it is present above limit and the isolate is identified to species — but batch release is a snapshot. It tells you what was in that batch on that day, not whether the formulation can suppress an adapted strain across shelf life and consumer use. The uncomfortable conclusion is that a product
can pass ISO 11930 against all five organisms, pass release TVC, and still have P. gergoviae in it. Not only it is not in the ISO 11930 challenge
panel. It is not a specified organism under ISO 17516, which requires absence of S. aureus, P. aeruginosa, C. albicans and E. coli. It surfaces in routine work only when a total viable count is exceeded and somebody troubles to identify the isolate to species level. The recorded incidence of P. gergoviae contamination is therefore not a
September 2026 PERSONAL CARE MAGAZINE
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92
