Persistence of a carbapenem-resistant Acinetobacter baumannii (CRAB) International Clone II (ST2/IC2) sub-lineage involved with outbreaks in two Brazilian clinical settings

BACKGROUND

Acinetobacter baumannii international clone II (IC2) is a widespread pandemic clone, however, it is rarely described in South America. The present study reported an outbreak caused by XDR IC2 strains in a clinical setting in Rio de Janeiro in 2022.

METHODS

Molecular epidemiology analysis was conducted with MLST to determine the clonal relationship and to assign a sequence type. The antimicrobial resistance profile of A. baumannii strains was assessed by the disk-diffusion method and MIC determination, and the presence of antibiotic resistance genes was determined by PCR and Sanger sequencing. The whole genome of one representative strain (AB91) was sequenced to prospect its resistome and virulome.

RESULTS

The MLST revealed that all strains belonged to the ST2 (Pasteur scheme) that corresponded to the pandemic IC2 lineage. They presented the XDR phenotype, which was compatible with their resistome composed of several acquired resistance genes and altered housekeeping genes. Additionally, an expressive virulome was revealed in AB91 genome. Genomic comparison with the unique other available IC2 genome from Brazil revealed that outbreaks occurring during (São Paulo - 2020/2021) and after (Rio de Janeiro - 2022) COVID-19 pandemics were caused by the same IC2 lineage.

CONCLUSIONS

This study suggests that the presence of a huge arsenal of resistance and virulence genes may have contributed to the persistence and the successful establishment of IC2 in Brazilian clinical settings during and after the COVID-19 pandemics in response to a series of events, such as the antibiotic overused during that period.

Outbreak of high-risk XDR CRAB of international clone 2 (IC2) in Rio Janeiro, Brazil

OBJECTIVES

Among the high-risk clones of Acinetobacter baumannii, called international clones (ICs), IC2 represents the main lineage causing outbreaks worldwide. Despite the successful global spread of IC2, the occurrence of IC2 is rarely reported in Latin America. Here, we aimed to evaluate the susceptibility and genetic relatedness of isolates from a nosocomial outbreak in Rio de Janeiro/Brazil (2022) and perform genomic epidemiology analyses of the available genomes of A. baumannii.

METHODS

Sixteen strains of A. baumannii were subjected to antimicrobial susceptibility tests and genome sequencing. These genomes were compared phylogenetically with other IC2 genomes from the NCBI database, and virulence and antibiotic resistance genes were searched.

RESULTS

The 16 strains represented carbapenem-resistant A. baumannii (CRAB) with an extensively drug-resistant profile. In silico analysis established the relationship between the Brazilian CRAB genomes and IC2/ST2 genomes in the world. The Brazilian strains belonged to three sub-lineages, associated with genomes from countries in Europe, North America, and Asia. These sub-lineages presented three distinct capsules, KL7, KL9, and KL56. The Brazilian strains were characterised by the co-presence of blaOXA-23 and blaOXA-66, in addition to the genes APH(6), APH(3"), ANT(3"), AAC(6'), armA, and the efflux pumps adeABC and adeIJK. A large set of virulence genes was also identified: adeFGH/efflux pump; the siderophores barAB, basABCDFGHIJ, and bauBCDEF; lpxABCDLM/capsule; tssABCDEFGIKLM/T6SS; and pgaABCD/biofilm.

CONCLUSION

Widespread extensively drug-resistant CRAB IC2/ST2 is currently causing outbreaks in clinical settings in southeastern Brazil. This is due to at least three sub-lineages characterised by an enormous apparatus of virulence and resistance to antibiotics, both intrinsic and mobile.

Function of milk polymorphonuclear neutrophil leukocytes in bovine mammary glands infected with Corynebacterium bovis

Corynebacterium bovis is one of the most commonly isolated bacteria from aseptically collected bovine milk samples. The objective of the current study was to characterize the bovine innate immune response by evaluating milk polymorphonuclear neutrophilic leukocytes (PMNL) in mammary glands infected with C. bovis. Twenty quarters infected with C. bovis and 28 culture-negative quarters (with milk somatic cell count <1×10(5) cells/mL) were used. The percentages of milk PMNL and the PMNL expression of L-selectin (CD62L), β2-integrin (CD11b), and one of the endothelial-selectin ligands (CD44), as well as the levels of intracellular reactive oxygen species (ROS) and the phagocytosis of Staphylococcus aureus, were evaluated by flow cytometry. The apoptosis and necrosis rates of the PMNL were quantified using dual-color flow cytometry with fluorescein-labeled annexin and propidium iodide. The present study revealed a higher percentage of PMNL in the milk from C. bovis-infected quarters, although no significant differences were found in levels of CD44, CD62L, or CD11b expression among the PMNL. A lower percentage of apoptotic PMNL was observed in C. bovis-infected quarters, as well as higher percentages of viable PMNL and of PMNL that produced intracellular ROS. However, no alterations were observed in phagocytosis of Staph. aureus by the PMNL or in intensity of intracellular ROS production by PMNL. Thus, results from this investigation of the PMNL function support, at least in part, the fact that intramammary infections by C. bovis may offer protection against intramammary infections by other bacteria.

Short-term administration of ethanol in mice deviates antigen presentation activity towards B cells

Alcohol has a variety of short- and long-term effects on cell-mediated and humoral immune response. Herein, we have characterized the impact of high-dose EtOH administration on phenotypic and functional features of murine APC subsets, including dendritic cell (DC), macrophages and B cells. Impaired cytokine synthesis and Leishmania-phagocytosis was observed in peritoneal macrophages following EtOH administration. Moreover, EtOH exposure led to decreased levels of splenic myeloid DC and increased percentage of macrophages with no changes in splenic lymphoid DC and B cells. Adverse effects of short-term EtOH administration also resulted in impaired OVA-endocytosis by DC and macrophages. In contrast, EtOH consumption upregulates OVA-internalization by B cells. These changes on APC hierarchy may play a role shifting the fate of the immune response after EtOH ingestion. In addition to an overall downregulation of Toll-like receptor-TLR-4 expression by splenic APC, a downregulation of TLR-2 expression in macrophages was observed. Moreover, EtOH exposure altered the expression of co-signalling molecules on splenic APC, downregulating CD40 on macrophages and upregulating CD80 on B cells, with no impact on DC subsets. The net result of changes in TLR-mediated and co-stimulatory signals may determine the altered immunological status induced by acute consumption of alcohol. A direct impact of high-dose EtOH administration in the activation status of splenic CD4(+) T cells was observed. Together, our results demonstrated that short-term high-dose EtOH administration has differential impact on APC populations, downregulating splenic macrophages and DC activity but up-regulating B lymphocyte function as APC, and ultimately yielding a micro-environment that led to increased activation of CD4(+) T cells.

Role of mesenteric lymph nodes and aging in secretory IgA production in mice

Although it is known that Peyer's patches are the major inductive site for S-IgA production and B1 cells contribute to half of the IgA plasma cells detected in the gut lamina propria, the type of contribution of mesenteric lymph nodes to the process is still unclear. Cytokines such as TGF-beta, IL-10, IL-4, IL-5, and IL-6, are required to promote IgA class switching and IgA synthesis. Aging-related alterations in T and B cells and in cytokine production are already known. Some reports have also proposed that S-IgA production might be altered in aged animals. Herein, we investigated the role of MLN and aging in S-IgA production. Two- to 18-month-old BALB/c mice were used to evaluate aging-related alterations and MLN were removed to study its role in S-IgA production. We found that MLN are important, although not essential for S-IgA production. In addition, we showed that production of IgA-related cytokines are well preserved in MLN but not in PP of aged mice and that S-IgA levels are not affected by aging. Our results suggest that MLN may play a complementary role in S-IgA production mostly in aged animals.