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

Abstract

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.

The plasmid diversity ofAcinetobacter bereziniaeHPC229 provides clues on the ability of the species to thrive on both clinical and environmental habitats

“…Also, those regions encoding heavy metal (cadmium, cobalt, nickel and zinc) detoxification systems (region Abe6, S1A Fig) were also identified in strains NIPH 3, WC-743 and CHI-40-1 (S4 Table). It is worth noting that similar systems bearing strong adaptive significance have been described in plasmids from both pathogenic species of the genus such as A. baumannii [73,74] as well as from different environmental microbial populations [18,75]. Taken together, the above data reinforce the notion that these adaptive traits are being disseminated by plasmids among different bacterial populations.…”

Tracking the Dairy Microbiota from Farm Bulk Tank to Skimmed Milk Powder

“…Although traditionally associated with opportunistic infections, drug resistance, and nosocomial infections, A. baumannii has been detected in animal products and was shown to have epidemiological characteristics that are different from those of strains that cause nosocomial infections (25). It has also been detected in bulk tank milks and dairy powders, leading the Food and Agriculture Organization of the United Nations (FAO) to classify it as one of the "category B organisms-causality plausible, but not yet demonstrated," with respect to causing infant illness from powdered infant formula (26). The low number of shotgun metagenomic reads did not allow accurate strain-level identification or the identification of specific virulence-associated genes to facilitate a more in-depth investigation.…”

Insight into the resistome and quorum sensing system of a divergent Acinetobacter pittii isolate from an untouched site of the Lechuguilla Cave

“…Cloning and regulated expression of these two bla genes will be instructive to verify their in-silico predicted role in hydrolyzing beta-lactam drugs [23]. The presence of bla ADC and bla OXA-213-like genes in cave isolate LC510 that has no prior history of anthropogenic exposure supports previous work claiming that these genes contribute to the intrinsic antibiotic resistance in A. pittii [5, 22]. Interestingly, despite harboring a variant ( bla oxa-421 ) of the bla OXA-213 -like gene, the carbapenem-resistant A. pittii CR12-42 is susceptible to ampicillin when supplemented with sulbactam [6, 24], indicating the susceptibility of bla OXA-213-like protein to a β -lactamase inhibitor [24].…”

“…Based on the initial 16S rRNA gene-based identification of LC strains [4], LC510 stood out due to its affiliation to the genus Acinetobacter . LC510 was isolated from a site deep within the Capitan Formation proximal to the region named “Deep Secrets” at a depth below the surface of approximately 400 m. Although most members of Acinetobacter are found in soils, waters and occasionally animal feeds, some Acinetobacter species are known to infect humans with broad-spectrum antibiotic resistance and such environmental isolates may serve as a reservoir for additional resistance determinants [5, 6]. In this study, we characterized LC510 using whole genome sequencing, biochemical assays, and bioinformatic tools, providing insights into its taxonomic affiliation, resistome and quorum sensing potential.…”