Desiccation survival of Acinetobacter spp. in infant formula

Characterization of a Ligilactobacillus salivarius Strain Isolated from a Cheese Seal Which Was Last Used in 1936

Cheesemaking played a pivotal role in the life of the Pyrenean villages where cheese was a most prized commodity and the subject of much local competition. In one of them (Sasa de Sobrepuerto), Mrs. Sebastiana Palacio decided in 1877 to label all the cheeses made in her household with a seal to differentiate them from those made by other local producers. The cheese seal was last used in 1936 and, since then, it has been kept under excellent storage conditions. Since well-preserved cheese seals are rare, and bacterial cells may survive desiccation for long periods, the objective of this work was to isolate and characterize any lactic acid bacteria that survived in the seal. Analysis of the milky crust material revealed the presence of sheep caseins. Culture-based analysis led to the isolation of a strain of Bacillus licheniformis and a strain of Ligilactobacillus salivarius (L. salivarius SP36). The latter was characterized in vitro for safety and dairy-related functional properties. Its genome encodes several genes involved in protein, peptide, and amino acid catabolism, and flavor. Overall, the phenotypic and genetic features of this strain support a high potential for being used as adjunct culture in cheesemaking.

The risk of infectious pathogens in breast-feeding, donated human milk and breast milk substitutes

OBJECTIVE

This review collates the published reports that focus on microbial and viral illnesses that can be transmitted by breast milk, donor milk and powdered infant formula (PIF). In this context, we attempt to define a risk framework encompassing those hazards, exposure scenarios, vulnerability and protective factors.

DESIGN

A literature search was performed for reported cases of morbidity and mortality associated with different infant feeding modes.

SETTING

Exclusive breast-feeding is the recommended for infant feeding under 6 months, or failing that, provision of donated human milk. However, the use of PIF remains high despite its intrinsic and extrinsic risk of microbial contamination, as well as the potential for adverse physiological effects, including infant gut dysbiosis.

RESULTS

Viable pathogen transmission via breast-feeding or donor milk (pasteurised and unpasteurised) is rare. However, transmission of HIV and human T-cell lymphotropic virus-1 is a concern for breast-feeding mothers, particularly for mothers undertaking a mixed feeding mode (PIF and breast-feeding). In PIF, intrinsic and extrinsic microbial contamination, such as Cronobacter and Salmonella, remain significant identifiable causes of infant morbidity and mortality.

CONCLUSIONS

Disease transmission through breast-feeding or donor human milk is rare, most likely owing to its complex intrinsically protective composition of human milk and protection of the infant gut lining. Contamination of PIF and the morbidity associated with this is likely underappreciated in terms of community risk. A better system of safe donor milk sharing that also establishes security of supply for non-hospitalised healthy infants in need of breast milk would reduce the reliance on PIF.

Acinetobacter spp. in food and drinking water - A review

Acinetobacter spp. has emerged as a pathogen of major public health concern due to their increased resistance to antibiotics and their association with a wide range of nosocomial infections, community-acquired infections and war and natural disaster-related infections. It is recognized as a ubiquitous organism however, information about the prevalence of different pathogenic species of this genus in food sources and drinking water is scarce. Since the implementation of molecular techniques, the role of foods as a source of several species, including the Acinetobacter baumannii group, has been elucidated. Multidrug resistance was also detected among Acinetobacter spp. isolated from food products. This highlights the importance of foods as potential sources of dissemination of Acinetobacter spp. between the community and clinical environments and reinforces the need for further investigations on the potential health risks of Acinetobacter spp. as foodborne pathogens. The aim of this review was to summarize the published data on the occurrence of Acinetobacter spp. in different food sources and drinking water. This information should be taken into consideration by those responsible for infection control in hospitals and other healthcare facilities.

Coping with low water activities and osmotic stress in Acinetobacter baumannii: significance, current status and perspectives

Multidrug resistant (MDR) pathogens are one of the most pressing challenges of contemporary health care. Acinetobacter baumannii takes a predominant position, emphasized in 2017 by the World Health Organization. The increasing emergence of MDR strains strengthens the demand for new antimicrobials. Possible targets for such compounds might be proteins involved in resistance against low water activity environments, since A. baumannii is known for its pronounced resistance against desiccation stress. Despite the importance of desiccation resistance for persistence of this pathogen in hospitals, comparable studies and precise data on this topic are rare and the mechanisms involved are largely unknown. This review aims to give an overview of the studies performed so far and the current knowledge on genes and proteins important for desiccation survival. 'Osmotic stress' is not identical to 'desiccation stress', but the two share the response of bacteria to low water activities. Osmotic stress resistance is in general studied much better, and in recent years it turned out that accumulation of compatible solutes in A. baumannii comprises some special features such as the bifunctional enzyme MtlD synthesizing the unusual solute mannitol. Furthermore, the regulatory pathways, as understood today, will be discussed.

The role of compatible solutes in desiccation resistance of Acinetobacter baumannii

Acinetobacter baumannii is a nosocomial pathogen which can persist in the hospital environment not only due to the acquirement of multiple antibiotic resistances, but also because of its exceptional resistance against disinfectants and desiccation. A suitable desiccation assay was established in which A. baumannii ATCC 19606^T survived for ca. 1 month. The growth medium slightly influenced survival after subsequent desiccation. A significant effect could be attributed to the growth phase in which bacteria were dried: In exponential phase, cells were much more desiccation sensitive. The main focus of the present study was the elucidation of the role of compatible solutes, which are known to protect many bacteria under low water activity conditions, in desiccation survival of A. baumannii. Exogenous trehalose was shown to efficiently protect A. baumannii on dry surfaces, in contrast to other compatible solutes tested such as mannitol or glycine betaine. To analyze the importance of intracellularly accumulated solutes, a double mutant lacking biosynthesis pathways for mannitol and trehalose was generated. This mutant accumulated glutamate as sole solute in the presence of high NaCl concentrations and showed severe growth defects under osmotic stress conditions. However, no effect on desiccation tolerance could be seen, neither when cells were dried in water nor in the presence of NaCl.

Cronobacter sakazakii and Microbiological Parameters in Dairy Formulas Associated With a Food Alert in Chile

The objective of this study was to evaluate the presence of Cronobacter sakazakii and microbiological parameters in dairy products associated with a food alert. Ninety dairy product samples were analyzed, including seven commercial brands and two product types (liquid and powdered) from four countries. Aerobic plate count (APC) and Enterobacteriaceae count were performed according to Chilean standards. Cronobacter spp. and C. sakazakii were identified by polymerase chain reaction real time amplification of rpoB and cgcA genes and the genotype by multilocus sequence typing. Eighty-eight percent of dairy products showed APC higher than the detection limit. Fifty percent of liquid commercial brand samples contained APC: 2.6, 2.3, 1.1, and 2.9 CFU/mL in brands A, C, E, and G, respectively. Results for powdered commercial brands were 3.0, 3.6, and 5.7 CFU/g in brands B, D, and F, respectively. Maximum count (5.7 CFU/g) occurred in brand F dairy product manufactured in Chile. Enterobacteriaceae were found in 55% of the samples, 64% in liquid and 51% in powdered commercial brands. In 50% of brands B, D, and E, samples contained 2.9, 2.8, and 2.7 log CFU/g, respectively. Only liquid commercial brands from the United States had Enterobacteriaceae values between 0.1 and 4.5 CFU/mL. Seventeen suspicious strains were isolated and nine were identified as Enterobacter spp. Only eight suspicious strains from four powdered commercial brands (Chile and Singapore) were confirmed as C. sakazakii by rpoB and cgcA gene amplification and fusA sequencing. C. sakazakii prevalence in the analyzed samples was 8.8%. There were 11% of powdered milk brands that contained APC between 4.0 and 4.7 log CFU/g and 55% of the samples contained Enterobacteriaceae. C. sakazakii was found in dairy products manufactured in Chile and Singapore. On the basis of this information, the Chilean Ministry of Health (RSA) decreed a national and international food alert and recalled all the product batches that resulted positive in the present study from supermarkets and pharmacies.

Microbial community structure and distribution in the air of a powdered infant formula factory based on cultivation and high-throughput sequence methods

The air in a powdered infant formula (PIF) factory is a potential transfer medium for microorganisms. In this study, air samples from 6 main processing areas, almost covering the whole PIF processing line and 1 outdoor location, were collected from a PIF manufacturing plant during the winter and summer periods. A cultivation-based and an Illumina (San Diego, CA) high-throughput 16S rRNA sequencing method was used to investigate the community structures and distributions of bacteria in the air. High microbial diversity (25 genera, 56 species), with a dominant community including Staphylococcus, Bacillus, Acinetobacter, and Kocuria, was found by the cultivation-based method. Moreover, 104 genera were obtained from all samples by high-throughput sequencing methods. Lactococcus (32.3%), Bacillus (29.6%), and Staphylococcus (14.0%) were the preponderant genera. The indices from high-throughput sequencing results indicated that the bacterial community of the air samples was highly diverse. Significant differences in the diversity and distribution at 6 sampling locations were revealed using the 2 methods. In particular, the packaging process contained the highest proportion (39.4%) of isolated strains. The highest diversity in bacterial community structure was found in the outdoor location. More bacterial isolates and higher community diversity were observed in the summer samples compared with the winter samples. In addition, some pathogens, such as Acinetobacter baumannii, Bacillus cereus, and Staphylococcus cohnii, were mainly found in the large bag filling process, can filling, and packaging process areas. The present study provides greater insight into the microbial community and identifies potential sources of air contamination in PIF production environments and can serve as a guide to reduce the risk of microbial contamination in the production of PIF.

Diversity and Antibiotic Susceptibility of Acinetobacter Strains From Milk Powder Produced in Germany

Forty-seven Acinetobacter spp. isolates from milk powder obtained from a powdered milk producer in Germany were investigated for their antibiotic resistance susceptibilities, in order to assess whether strains from food harbor multiple antibiotic resistances and whether the food route is important for dissemination of resistance genes. The strains were identified by 16S rRNA and rpoB gene sequencing, as well as by whole genome sequencing of selected isolates and their in silico DNA-DNA hybridization (DDH). Furthermore, they were genotyped by rep-PCR together with reference strains of pan-European groups I, II, and III strains of Acinetobacter baumannii. Of the 47 strains, 42 were identified as A. baumannii, 4 as Acinetobacter Pittii, and 1 as Acinetobacter calcoaceticus based on 16S rRNA gene sequencing. In silico DDH with the genome sequence data of selected strains and rpoB gene sequencing data suggested that the five non-A. baumannii strains all belonged to A. pittii, suggesting that the rpoB gene is more reliable than the 16S rRNA gene for species level identification in this genus. Rep-PCR genotyping of the A. baumannii strains showed that these could be grouped into four groups, and that some strains clustered together with reference strains of pan-European clinical group II and III strains. All strains in this study were intrinsically resistant toward chloramphenicol and oxacillin, but susceptible toward tetracycline, tobramycin, erythromycin, and ciprofloxacin. For cefotaxime, 43 strains (91.5%) were intermediate and 3 strains (6.4%) resistant, while 3 (6.4%) and 21 (44.7%) strains exhibited resistance to cefepime and streptomycin, respectively. Forty-six (97.9%) strains were susceptible to amikacin and ampicillin-sulbactam. Therefore, the strains in this study were generally not resistant to the clinically relevant antibiotics, especially tobramycin, ciprofloxacin, cefepime, and meropenem, suggesting that the food route probably poses only a low risk for multidrug resistant Acinetobacter strains or resistance genes.