New sequence types of Acinetobacter baumannii in two emergency hospitals in the Central-West region of Brazil

Dear Editor:

Acinetobacter baumannii, a common causal agent of ventilator-associated pneumonia, is related with high hospital costs and mortality¹. The 2016 surveillance report of the European Centre for Disease Prevention and Control reported that 49% of A. baumannii isolates were carbapenem resistant². In Brazil, the percentage of this species with resistance to carbapenems is approximately 71%, with similar data for Chile and Argentina³. The genes bla _OXA-23, bla _OXA-24 (and its variants bla _OXA-40 and bla _OXA-72), bla _OXA-58, bla _OXA-143, and bla _OXA-235 of the Ambler class D β-lactamases are responsible for carbapenem resistance in A. baumannii⁴. Multilocus sequence typing (MLST) is used to determine the sequence type (ST) of isolates, with A. baumannii ST15, ST25, ST79, and ST1 being the most common in South America⁵. These clones are clustered in MLST clonal complexes (CC) CC15, CC25, CC79, and CC1, respectively⁵. In Brazil, A. baumannii ST15, ST79, and ST1 are also frequently found⁶.

A total of nine Acinetobacter spp. isolates were extracted from rectal swab and wound secretion samples from nine patients hospitalized in intensive care units at two public emergency hospitals in Cuiaba and Varzea Grande, Mato Grosso State, Central Brazil: the Municipal Hospital and Emergency Room of Cuiaba, and the Municipal Hospital and Emergency Room of Varzea Grande. Rectal swabs and wound secretion samples were collected from the patients for routine surveillance by the hospital infection control committees between June 2012 and August 2012. Microorganism identification was performed, and drug resistance profiles based on the minimum inhibitory concentration were obtained using the Bact/Alert 3D and Vitek2 systems (BioMérieux, Marcy l’Etoile, France) in the Microbiology Laboratory of the Júlio Muller University Hospital, Cuiaba, Mato Grosso, Brazil. Isolates identified as Acinetobacter spp. were tested for their sensitivity to antimicrobials according to the 2017 Clinical and Laboratory Standards Institute Guidelines⁷. The genomic DNA extraction, polymerase chain reaction (PCR) for the detection of A. baumannii genes, and application of the MLST technique for genotypic analysis of the isolates were performed in the Laboratory of Veterinary Microbiology and Molecular Biology, College of Veterinary Medicine, Federal University of Mato Grosso, Mato Grosso, Brazil^8-10.

The research protocol (#850.791) was approved by the Ethics Research Committee of the Julio Muller Hospital, and was registered in the National System of the Ethical Evaluation of Human Research Projects (CAAE 28637414.0.0000.5541). The A. baumannii isolates were confirmed by the PCR-based amplification of the bla _OXA-51 gene. The patient demographics and the isolates’ in vitro resistance to antimicrobials are detailed in Table 1.

TABLE 1:
Clinical characteristics of the nine hospitalized patients, and in vitro susceptibility to imipenem, resistance genes, sequence types, and clonal complexes of Acinetobacter baumannii isolates, from two emergency hospitals in the Center-West region of Brazil.

Patient	Age	Sample	Imipenem	Time to	Hospital	Prior	Outcom	blaOXA-23/	bla OXA-24	bla OXA-143	Sequence	Clonal
	(year),Sexa	b	c	isolation (day)	d	treatmente	e	ISAba1			type (ST)	complexf (CC)
1	67, F	RS	R	20	A	IMP	Recovery	+	-	+	984	Singletong
2	35, M	RS	R	19	A	PIPE/TAZ, IMP, VAN	Recovery	+	-	-	108	108
3	78, F	RS	R	05	A	CEFA	Death	+	+	-	1	1
4	41, F	RS	R	20	A	PIPE/TAZ, VAN	Recovery	+	+	-	108	108
5	45, M	RS	R	50	B	PIPE/TAZ, VAN	Recovery	+	+	-	162	162
6	23, M	WS	S	33	B	CEFE	Recovery	+	-	-	985	79
7	21, M	RS	R	14	B	CEFE, VAN	Recovery	+	+	-	409	1
8	23, M	RS	R	18	B	CEFI, CEFE, VAN	Recovery	+	+	+	987	987
9	42, F	RS	R	27	B	PIPE/TAZ	Recovery	+	+	+	NPh	NP

• ^aF: female; M: male; ^b RS: rectal swab; WS: wound secretion; ^c R: resistant; S: sensitive; ^d A: Municipal Hospital and Emergency Room of Varzea Grande; B: Municipal Hospital and Emergency Room of Cuiaba; ^e IMP: imipenem; PIPE/TAZ: piperacillin/tazobactam; CEFE: cefepime; CEFA: cephalothin; CEFI: ceftriaxone; VAN: vancomycin; ^f Clonal complex according to the eBurst classification; ^g ST984: identified for the first time in this study and classified as a singleton by eBurst; ^h NP: not performed.

The A. baumannii isolates analyzed in this study showed resistance to imipenem and other drugs, as well as sensitivity to polymyxin B, similar to the trends reported in other regions of Brazil and in other countries^2,3,9. The bla _OXA-23 gene was most frequently found. These data are similar to those of other international and Brazilian studies^5,6,9. Other genes associated with carbapenem resistance were bla _OXA-24 and bla _OXA-143 . The bla _OXA-24 gene is more prevalent in some countries, such as Ecuador and Mexico, and is uncommon in Brazil^5,6,11. However, it was the second most prevalent carbapenem resistance gene found in another study conducted in the Center-West region of Brazil⁹. The bla _OXA-143 gene, which has been detected in southeastern, southern, and central Brazil, was again found in the Center-West region of the country^9,10. The bla _OXA-58, bla _KPC, and bla _NDM genes were not found. Phylogenetic classification by MLST revealed the presence of ST108, ST162, and ST1, which are commonly found in South American countries, including Brazil^5,6,9. Interestingly, one of the isolates corresponded to ST409, a sequence type first described in Egypt, and was never described in Brazil until now¹². Three new STs (ST984, ST985, and ST987) were found.

The isolates reported here were recovered form surveillance cultures, and only one patient evolved to death. However, the finding of isolates of different multidrug-resistant A. baumannii STs deserves the attention and concern of local health authorities owing to the extended antimicrobial resistance profile of this microorganism. More research is warranted to assess the impact of this multidrug-resistant bacterium on the generation of threatening infections in the study region.

Accession numbers of new sequences reported in the article (https://pubmlst.org/abaumannii/): ST984, ST985, and ST987.

REFERENCES

• ¹
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  de Azevedo FKSF, Dutra V, Nakazato L, Mello CM, Pepato MA, de Sousa ATHI, et al. Molecular Epidemiology of Multidrug-Resistant Acinetobacterbaumannii Infection in Two hospitals in Central Brazil: The Role of ST730 and ST162 in Clinical Outcomes. J Med Microbiol . 2019;68(1):31-40.
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  Alcántar-Curiel MD, García-Torres LF, González-Chávez MI, Morfín-Otero R, Gayosso-Vázquez C, Jarillo-Quijada MD, et al. Molecular Mechanisms Associated With Nosocomial Carbapenem-Resistant Acinetobacter baumannii in Mexico. Arch Med Res. 2014;45(7):553-60.
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• Financial Support: This research had financial support from the BrazilianNational Council for Scientific and Technological Development (CNPq), a federal agency for research support, through a research incentive grant for Francisco José Dutra Souto.

Publication Dates

• Publication in this collection
  18 July 2019
• Date of issue
  2019