Microbiota associated with tramp ants in a Brazilian University Hospital

Microbiota associada às formigas urbanas em um Hospital Universitário Brasileiro

PUBLIC HEALTH

Microbiota associated with tramp ants in a Brazilian University Hospital

Microbiota associada às formigas urbanas em um Hospital Universitário Brasileiro

Maxelle M Teixeira^I,II; Afonso Pelli^II; Vitorino M dos Santos^III; Maria das G Reis^II

^ICurso de Pós-Graduação em Patologia Geral; [e-mail]

^IIDepto. de Ciências Biológicas, Univ. Federal do Triângulo Mineiro, Rua Frei Paulino, 30, Uberaba, MG, 38025-180; [e-mail]; [e-mail]

^IIIDepto. de Clínica Médica do Hospital das Forças Armadas e Univ. Católica de Brasília, PTC Q.S. 07, Lote 1, Águas Claras, Taguatinga, BRASILIA, DF, 71966-700; [e-mail]

ABSTRACT

Our aim was to study the fauna of ants in the Hospital Universitário of the Universidade Federal do Triângulo Mineiro, municipality of Uberaba, Minas Gerais State, Brazil, as well as to identify the microorganisms the ants carry and their patterns of resistance to antibiotics. Sterile tubes (traps) containing honey were used to attract the ants. Traps were exposed for 3h, and those which attracted ants were considered the test group, while the ones that did not attract the insects constituted the control group. Only the ant species Tapinoma melanocephalum (Fabricius) was sampled. Sixty microorganisms were isolated from the sampled ants, including seven Gram-positive bacilli, 14 Gram-negative bacilli, 22 Gram-positive cocci and 17 filamentous fungi. Pseudomonas, Staphylococcus and Group D Streptococcus were the microorganisms with the highest resistance to the tested antibiotics. The ants should be considered an important vector of infections as they carry several pathogenic microorganisms, spreading them on the surface of sterile materials, equipments and uncontaminated food. It is impossible to define the exact role of ants in nosocomial infections at this moment; however, this issue must be better studied and special attention must be given by the commissions of Nosocomial Infection Control.

Key words: Hospital infection, pathogenic microorganism, antimicrobial resistance, distribution

RESUMO

O objetivo deste estudo foi conhecer a fauna de formigas existente no Hospital Universitário da Universidade Federal do Triângulo Mineiro, Uberaba, MG, bem como as espécies de microrganismos transportadas por elas, além de identificar o padrão de resistência destes microrganismos a antimicrobianos. Para atrair as formigas, utilizaram-se tubos estéreis contendo mel. Após período de exposição de 3h, os mesmos foram tampados. Os tubos que atraíram formigas foram considerados o grupo teste e os que não atraíram o controle. Apenas Tapinoma melanocephalum (Fabricius) foi amostrada. O isolamento de microrganismos dos exemplares de T. melanocephalum apontou 60 espécies, entre as quais sete eram bacilos Gram positivo, 14 bacilos Gram negativo, 22 cocos Gram positivo e 17 fungos filamentosos. Pseudomonas, Staphylococcus e Streptococcus do grupo D foram os microrganismos que apresentaram maior resistência aos antibióticos. As formigas devem ser consideradas um importante vetor de infecções, pois são carreadoras de microrganismos, levando-os na superfície de seu corpo para materiais estéreis, equipamentos e alimentos não-contaminados. Não é possível definir o papel exato das formigas em infecções nosocomiais. No entanto, este deve ser melhor avaliado e atenção especial deve ser dada pelas comissões de Controle de Infecções Hospitalares.

Palavras-chave: Infecção hospitalar, microrganismo patogênico, resistência antimicrobiana, distribuição

Several reports have alerted to the specific role of insects in the transport of associated microorganisms in the hospital environment, which favors nosocomial infections (Beatson 1972, Eicheler 1990, Sramova et al 1992, Sawicka 1993).

Ants not always were considered noxious insects, although an eventual role in the transport of microorganisms has been investigated since the seventies. More often, ants cause problems if they appear in great numbers, and not because they can act as mechanical vectors of pathogenic microorganisms (Ipinza-Regla et al 1981).

In Brazil, this kind of study is relatively recent. In 1993, 14 ant species were described associated to hospitals in the State of São Paulo (Fowler et al 1993). The predominance of particular ant species varied among the different sampled institutions, but the risk of an eventual association between these insects and the hospital infections was already emphasized.

Factors that may favor the presence of ants in hospitals include the building architecture, proximity to residences, occurrence of packages of medicines containing nests of ants, circulation of people with clothes and/or objects carrying ants, in addition to food remains which constitute an extra attractive (Zarzuela et al 2002).

Our objective here was to study the existent fauna of ants in the Hospital Universitário of the Universidade Federal do Triângulo Mineiro, and to disclose the species of microorganisms they carry. We also aimed at identifying the patterns of antimicrobial resistance developed by these microorganisms.

Material and Methods

The study was accomplished at the Intensive Care Units (ICUs) and surgical center from the Hospital of UFTM, in Uberaba, MG. Samples were collected monthly, from May 2005 to May 2006.

Collection and identification. Ten sterilized test tubes containing honey were left in specific sites of the hospital by 3h in order to attract ants. Afterwards, the tubes were closed and sent to the microbiology laboratory of the Hospital. The tubes which attracted ants constituted the test group (TG), and those tubes without ants were considered the control group (please see Discussion) (CG).

In the laboratory, the ants were immersed in tubes with thioglycolate broth, agitated and incubated at 36 ± 1ºC for 48h. Aliquots of the thioglycolate broth were plated onto agar-blood for isolation, and again incubated at 36 ±1ºC for 24-48h. The Gram staining method was utilized for every plate showing bacterial growth. In case of fungi growth, they were simply classified as yeast-like or filamentous fungi.

Colonies of Gram-positive cocci were characterized according to their morphology, by the method of Gram, and the catalase and coagulase proofs (Koneman et al 2001). Disks with novobiocin were used to distinguish among the Staphylococcus cepa. To distinguish Streptococci, in addition to detection of hemolysis, tests with bile-esculin, 6.5% sodium chloride and optochin were utilized.

Antimicrobial susceptibility. Bacteria identified in the TG were submitted to the disk diffusion test for determination of the bacterial susceptibility to the tested antimicrobials, utilizing the Mueller Hinton broth, following the Clinical and Laboratory Standards Institute (CLSI) recommendations (CLSI 2005).

The antibiotics to test the Gram-negative bacilli included: G-penicillin, chloranfenicol, gentamicin, amikacin, aztreonam, cefalotin, levofloxacin and ciprofloxacin. The antibiotics to test the Gram-positive cocci were: oxacillin, G-penicillin, chloranfenicol, gentamicin, amikacin, vancomycin, cefalotin and ciprofloxacin. As a whole, the enrolled antibiotics from the Laborclin trademark were chosen because they are frequently used to treat patients in the Hospital of UFTM. The following strains were used for control purposes: ATCC Escherichia coli 25922, ATCC Enterococcus faecalis 29212, ATCC Staphylococcus aureus 25293 and ATCC Klebisiella pneumoniae 700603.

The profiles of resistance of the samples collected in ants were compared with the database of Commission of Nosocomial Infection Control - CNIC, of the Hospital in the UFTM from May to October of 2005.

The frequency of each microorganism occurrence, both in TG and CG were subjected to by ANOVA considering the parametric distribution, using the program MINITAB^® according to Draper & Smith (1981) at P < 0.05. The descriptive analysis of the sensitivity profile of bacteria isolated from ants was compared to those isolated from patients in the CNIC.

Results

Twelve collections from the intrahospital mirmecofauna were accomplished to identify the associated microbiota in four different sites from the Hospital of UFTM: ICU (adults), 5; ICU (pediatrics), 4; ICU (dressing room), 1; Surgical center (dining hall), 1. Only Tapinoma melanocephalum (Fabricius) was collected during the period of this study.

The isolation of microorganisms from the T. melanocephalum samples revealed 60 species, including seven Gram-positive bacilli, 14 Gram-negative bacilli, 22 Gram-positive cocci and 17 filamentous fungi. Only seven microorganisms were isolated from the control tubes, two Bacillus sp. and five coagulase-negative Staphylococci (Table 1).

Filamentous fungi were the microorganisms that presented the highest frequency (28.8%), followed by coagulase-negative Staphylococcus (23.7%), Gram-positive bacilli (11.8%) and Pseudomonas sp. (8.5%) (Table 1). Gram-positive bacilli (P = 0.030), Pseudomonas sp. (P = 0.009), Burkholderia cepacia (P = 0.045), Hafnia alvei (P = 0.045), Group D Streptococcus (P = 0.009), Staphylococcus sp. (P = 0.001) and filamentous fungi (P = 0.000) occurred at different frequencies between test and control groups (Table 1).

Burkholderia cepacia showed 100% resistance to cephalotin and 67% resistance to chloranfenicol, amikacin and aztreonam (Table 2). In the resistance profiles obtained by the CNIC in the Hospital of UFTM from May to October of 2005 (Table 3), there was no report of infections by B. cepacia. Pseudomonas sp. presented 40% resistance to chloranfenicol, aztreonam and imipenem (Table 2);when compared to the data from CNIC, the percentages of resistance were 47.3%, 50% and 31.6%, respectively (Table 3). Among the Gram-positive cocci, 60% of the coagulase-negative Staphylococcus were resistant to oxacilin; hence, they were also considered resistant to other beta-lactamic agents (penicillin and cefalotin) (CLSI, 2005). Similar profiles were observed among agents isolated by the CNIC in the Hospital of UFTM; 80% of the group D Streptococci were resistant to gentamicin, amikacin, cefalotin, oxacillin and penicillin. In relation to the group D Streptococci, the CNIC has found much lower rates of resistance to gentamicin, amikacin and penicillin: 51.7%, 62% and 34.5%, respectively.

Discussion

Similar to many other reports, the presence of ants was observed in the Hospital of UTFM, which is in accordance with the developing countries reality (Beatson 1972, Edwards & Backer 1981, Ipinza-Regla et al 1981, Sawicka 1993). The frequent use of these areas, in addition to cleaning and sanitation procedures often promote a gradual deterioration of the most fragile materials, especially in the covered openings and junctions of the walls, floors and ceilings. Even small crevices constitute ideal shelters for insects, in special for ants that usually live in urban structures (Schuler 1999).

Similar to the study of Moreira et al (2005), the control group of the present work was the ambient air. The purpose was to avoid eventual bias represented by microorganisms directly derived from the contaminated hospital air.

The ant species most commonly found in hospitals in the state of São Paulo were T. melanocephalum and Paratrechina longicornis (Latreille), but the first one was more prevalent (Fowler et al 1993). The identification of the microbiota from the collected ants was also done and Staphylococcus, Serratia, Klebsiella, Acinetobacter, Enterobacter, Candida and Enterococcus were isolated.

Although T. melanocephalum was the sole finding in the present study, other species may be found in our hospital, since the collections were limited to four specific areas. Moreover, in another study performed in our hospital from 2001 to 2005, samples of T. melanocephalum; Pheidole sp. and Paratrechina longicornis were captured (Costa et al 2006). The observed reduction in the number of ant species may be associated with the recent reforms that were made in the areas of the ICUs. Furthermore, while Costa et al (2006) collected ants in several environments; the present study was restricted to the ICUs and the surgical center. It is worthwhile to note that T. melanocephalum was the least frequent among seven ant species identified in two hospitals from the state of Santa Catarina (Lise et al 2006). Taponoma melanocephalum is commonly called ghost ant and is included in the group of tramp ants, which live in intimate association with humans (Campos-Farinha & Bueno 2003).

In this study, the ICUs and the surgical center were the chosen areas for collection because of the high number of patients under risk of hospital infection due to their low immunity. Moreover, a high index of ant infestation has been described in ICUs (Bueno & Campos-Farinha 1998).

In the state of Rio de Janeiro, four species of ants were described as carriers of hospital bacteria resistant to antimicrobials, being T. melanocephalum the most frequent (63.1%) (Moreira et al 2005). The enrolled bacteria included Bacillus spp., Enterobacter sp. and Staphylococcus sp., with a high frequency of coagulase-negative Staphylococcus resistant to oxacillin.

Coagulase-negative Staphylococci can play important role in immunosuppressed patients (Minto et al 1999). In the present study the bacteria were isolated in hospital environments with a high number of immunosuppressed patients; therefore, all the Staphylococcus that we found must be considered pathogenic. Coagulase-negative Staphylococci are among the main causes of hospital bacteremia, in special affecting patients from ICUs (Cunha et al 2002).

Strains of methicillin-resistant Staphylococcus are often described (Torres et al 2001); moreover, the ability of S. epidermidis to form biofilms may contribute to the origin of nosocomial infections involving hospital instruments (Dunne et al 1993).

Gram-negative bacilli, including Pseudomonas sp. and Enterobacter sp. represent a great risk in the hospital infections (ANVISA 2004). Pseudomonas sp. is an opportunistic pathogen, found in children submitted to mechanic ventilation in ICUs (Miranda et al 1999, Murray et al 2000). The wide range of their antibiotic resistance patterns indicate that strains of these pathogens are continuously selected (Banderó Filho et al 2006).

Hospital infections remain a common and serious unsolved challenge, which causes high morbidity and mortality rates. This condition increases the cost of treatment and the time of hospitalization, and constitutes a constant threat to the spread of multiresistant bacterial pathogens (Far et al 2001).

Although the role of ants in the hospital infections is not entirely cleared, there are sufficient data to support this possibility and the associated risks. Therefore, this matter should be better considered and settled by the commissions of Hospital Infection Control. Moreover, further studies must be performed to verify possible correlations between the microbial strains isolated from the ants and the strains isolated from patients with hospital infections acquired in the occasion of the ant's collections.

Received 10/II/08.

Accepted 14/VII/09.

Edited by Eunice Galati - FSP/USP

• Agência Nacional de Vigilância Sanitária - ANVISA (2004) Anvisa intensifica controle de infecção em serviços de saúde. Rev Saúde Pública 38:475-478.
• Banderó Filho V E, Reschk C R, Hörner R (2006) Perfil epidemiológico das infecções hospitalares na unidade de terapia intensiva infantil do Hospital de Caridade e Beneficência de Cachoeira do Sul, RS, Brasil. Rev Bras Anál Clin 38:267-270.
• Beatson S H (1972) Pharaoh's ants as pathogens vectors in hospitals. Lancet 19:425-427.
• Bueno O C, Campos-Farinha A E C (1998) Formigas urbanas: comportamento das espécies que invadem as cidades brasileiras. Rev Vetores Pragas 12:13-16.
• Campos-Farinha A E C, Bueno O C (2003) Formigas na área urbana. Biológico 65:93-94.
• Clinical and Laboratory Standards Institute - CLSI (2005) Performance standards for antimicrobial susceptibility testing. 14 ed., CLSI, Wayne, PA, USA.
• Costa S B, Pelli A, Carvalho G P, Oliveira A G, Silva P R, Teixeira M M, Martins E, Terra A P S, Resende E M, Oliveira C C H B, Morais C A (2006) Formigas como vetor mecânico de microrganismo no Hospital Escola da Universidade Federal do Triangulo Mineiro. Rev Soc Bras Med Trop 39:527-529.
• Cunha M L R S, Lopes C A M (2002) Estudo da produção de beta-lactamase e sensibilidade às drogas em linhagens de estafilococos coagulase-negativos isolados de recém-nascidos. J Bras Patol Med Laborat 38:281-290.
• Dunne W M., Mason Jr E O, Kaplan S L (1993) Diffusion of rifampin and vacomycin through a Staphylococcus epidermidis biofilm. Antimicrob Agents Chemother 37:2522-2526.
• Draper N R, Smith H (1981) Applied regression analysis. 2 ed., New York, John Wiley and Sons, 709p.
• Edwards J P, Backer L F (1981) Distribution and importance of Pharaoh's ant Monomorium pharaonis (L.) in National Health Service hospitals in England. J. Hosp Infect 2:249-254.
• Eicheler W (1990) Health aspects and control of Monomorium pharaoni, p.671-675. In Meer RKV, Jaffe K, Cedeno A (eds) Applied myrmecology: a world perspective. Boulder, Westview Press, 741p.
• Far F E, Marino G J, Medeiros E A S (2001) The organization of hospital infection control committees and their importance in Brazil. Braz J Infect Dis 5:290-293.
• Fowler H G, Bueno O C, Sadatsune T, Montelli A C (1993) Ants as potential vectors of pathogens in hospitals in the state of São Paulo, Brazil. Insect Sci Applic 14:367-370.
• Ipinza-Regla J, Figueroa G, Osorio J (1981) Iridomyrmex humilis 'hormiga argentina', como vector de infecciones intrahospitalarias: in estudio bacteriologico. Folia Entomol Mex 50:81-96.
• Koneman E W, Allen S D, Janda W M, Schreckenberger P C, Winn Jr W C (2001) Diagnóstico microbiológico: texto e atlas colorido. 5ºed., São Paulo, MEDSI, 1465p.
• Lise F, Garcia F R M, Lutinski J A (2006) Association of ants (Hymenoptera: Formicidae) with bacteria in hospitals in the State of Santa Catarina. Rev Soc Bras Med Trop 39:523-526.
• Minto E C M, Barrelli C, Martinez R, Darini A L C (1999). Identification and medical importance of coagulase-negative staphylococci species. São Paulo Med J 177:175-178.
• Miranda N G, Gadea A T, Leaños M B, Villasís K M A, Solórzano-Santos F (1999) Cultivos endobronquiales en niños con asistencia ventilatoria mecánica en una unidad de terapia intensiva. In Memorias VIII Reunión Nacional de Investigación Médica. México, D.F., IMSS.
• Moreira D D O, Moraes V, Motta O V, Campos-Farinha A E C, Tonhasca Jr A (2005) Ants as carriers of antibiotic-resistant bacteria in hospital. Neotrop Entomol 34:999-1006.
• Murray P R, Drew W L, Kobayashi G S, Thompson Jr J H (2000) Microbiologia Médica. 9 ed., Rio de Janeiro, Prentice-Hall, 604p.
• Sawicka B (1993) Insect vector diseases in hospitals. Przeg Epidemiol 47:451-7.
• Schuler L (1999) Controle de pragas no serviço de alimentação, 93-102. In Silva Jr E A (ed) Manual de controle higiênico-sanitário em alimentos. 3 ed., São Paulo, Livraria Varela, 347p.
• Sramova H, Daniel M, Absolonova V, Dedicova D, Jedlickova Z, Lhotova H, Petras P, Podzimkova M, Subertova V (1992) Bacterial contamination of arthropods in health institutions. Ceskoslovenskas-Epidemiol-Mikrobiol-Imunol 41:223-232.
• Torres B A, Kominsky S, Perrin G Q, Hobeika A C, Johnson H M (2001) Superantigens: the good, the bad, and the ugly. Exp Med Biol 226:164.
• Zarzuela M F M, Ribeiro M C C, Campos-Farinha A E C (2002) Distribuição de formigas urbanas em um hospital da Região Sudeste do Brasil. Arq Inst Biol 69:85-87.

Publication Dates

• Publication in this collection
  17 Sept 2009
• Date of issue
  Aug 2009

History

• Accepted
  14 July 2009
• Received
  10 Feb 2008