Evaluación de la resistencia a los antibióticos de cepas de Escherichia coli aisladas en carne de cerdo comercializada en los mercados municipales de la ciudad de Guatemala / Evaluation of antibiotics resistance of Escherichia coli strains isolated in pork sold in municipal markets of Guatemala City

La resistencia a los antimicrobianos es un problema de salud pública a nivel mundial que va en aumento y se ve reflejada en la falta de eficacia de los tratamientos de infecciones bacterianas con antibióticos en humanos y en animales. El presente estudio tuvo como objetivo evaluar la resistencia a los antibióticos de cepas de Escherichia coli aisladas en carne de cerdo expendida en los mercados municipales de la ciudad de Guatemala. Se identificaron los antibióticos que presentaron mayor resistencia y mayor sensibilidad in vitro frente a las cepas de E. coli aisladas a partir de 76 muestras de carne de cerdo. Se realizó un muestreo aleatorio simple con afijación proporcional por mercado. Para la identificación de las cepas de E. coli se utilizó la prueba de IMViC y para evaluar la resistencia a los antimicrobianos se utilizó la prueba de Kirby Bauer empleando 9 antibióticos. Se aisló E. coli en el 55% (42/76) de las muestras. La resistencia en las 42 cepas aisladas fue: tetraciclina (83%) neomicina (50%) y sulfametoxasole + trimetoprim (50%). 83% de las cepas (35/42) fueron resistentes a 2 antibióticos y 50% (21/42) a 3 antibióticos o más. Se obtuvo mayor sensibilidad con ceftriaxona (91%), amikacina (83%), gentamicina (65%) y ácido nalidíxico (65%). Se concluye que existe resistencia a los antibióticos evaluados, lo que constituye un riesgo para la salud pública ya que se encuentra en cepas aisladas en un alimento para consumo humano.

Antimicrobial resistance is a global public health threat that is increasing and is reflected in the lack of efficacy of bacterial infection treatments with antibiotics in humans and animals. The objective of this study was to evaluate the resistance to antibiotics of Escherichia coli strains isolated from pork in the municipal markets of Guatemala City. Antibiotics with the highest resistance and those with the highest sensitivity in vitro against the strains of E. coli were evaluated. A simple random sampling was carried out with proportional allocation by market, and 76 samples were collected. IMViC test was used to identify the E. coli strains, and antibiotics resistance was evaluated using the Kirby Bauer with nine different antibiotics. E. coli was isolated in 55% (42/76) of the samples. Resistance was evaluated in the 42 isolates. Antibiotic resistance was detected to tetracycline (83%), neomycin (50%), and sulfamethoxazole + trimethoprim (50%). All isolates presented resistance to at least one antibiotic; it was determined that 83% (35/42) showed resistance to two antibiotics and 50% (21/42) showed resistance to three antibiotics or more. The sensitivity obtained was higher for ceftriaxone (91%), amikacin (83%), gentamicin (65%), and nalidixic acid (65%). In conclusion, antibiotic resistance was detected, which constitutes a risk to public health since it is found in isolated strains in food for human consumption.

Trimetroprim-sulfametoxazol: Un caso de Necrólisis Epidérmica Tóxica / Trimethoprim-sulfamethoxazole: A Case of Toxic Epidermal Necrolysis

Necrólisis Epidérmica Tóxica (NET) es una rara pero grave emergencia caracterizada por difusa exfoliación de la piel y las membranas mucosas debido a pérdida de la epidermis, mediada por respuesta inmune que puede llevar a sepsis y fallo ventilatorio. El Trimetropin-Sulfametoxazol es un antibiótico ampliamente utilizado que es causa de dicha entidad. El diagnóstico prematuro y el tratamiento agresivo es esencial para la reducción de los elevados niveles de morbilidad y mortalidad asociadas con esta enfermedad. Presentamos un caso que fue precipitado debido al uso de Trimetropin-Sulfametoxazol en un hombre de 22 años de edad...(AU)

Toxic Epidermal Necrolysis (TEN) is a rare but serious emergency characterized by diffuse exfoliation of the skin and mucous membranes due to loss of the epidermis, mediated by immune response that can lead to sepsis and ventilatory failure. Trimetropin-Sulfamethoxazole is a widely used antibiotic that causes this entity. Premature diagnosis and aggressive treatment is essential for reducing the high levels of morbidity and mortality associated with this disease. We present a case that was precipitated due to the use of Trimetropin-Sulfamethoxazole in a man of 22 years of age ... (AU)

Perfil de sensibilidade aos antimicrobianos e eficácia de sanitizantes frente aos isolados de Salmonella spp: oriundos de carcaças suínas no Rio Grande do Sul / Antimicrobial sensitivity and efficacy of sanitizers against the Salmonella spp: isolated from swine slaughterhouse in southern Brazil

Os objetivos do trabalho foram avaliar o perfil de sensibilidade a antimicrobianos e a eficácia de três sanitizantes frente a isolados de Salmonella spp. oriundos de carcaças na tecnologia de abate de suínos. Avaliaram-se 120 amostras, das quais 39 foram positivas para Salmonella spp. Os princípios ativos testados foram penicilina G 10 U, amoxicilina + ácido clavulânico 30mcg, ampicilina 10mcg, cloranfenicol 30mcg, tetraciclina 30mcg, estreptomicina 10mcg, neomicina 30mcg, gentamicina 10mcg, enrofloxacina 5mcg, sulfazotrim 25mcg, sulfonamida 300mcg e trimetropima 5mcg. Nos testes com sanitizantes utilizaram-se clorexidina, amônia quaternária e ácido peracético com tempos de contato de um, cinco, 10 e 15 minutos. Os índices de resistência aos antimicrobianos foram de 100 por cento para penicilina, 94,9 por cento para tetraciclina, 89,7 por cento para trimetropima e 87,2 por cento para ampicilina. Nenhum dos princípios ativos foi 100 por cento eficaz frente aos isolados testados, observando-se melhor ação para amoxicilina+ácido clavulânico (86,7 por cento), neomicina (86,7 por cento) e cloranfenicol (64,1 por cento). Nos testes de eficácia dos sanitizantes, o ácido peracético a 0.5 por cento foi efetivo a partir de 10 minutos (94,6 por cento) e 15 minutos (97,3 por cento) de contato; amônia quaternária a 1 por cento por 10 minutos (89,2 por cento) e 15 minutos (97,3 por cento) e clorexidina a 0.5 por cento por 10 minutos (70,3 por cento) e 15 minutos de contato (72,8 por cento). Todas as amostras testadas apresentaram multirresistência e seis [...] O sanitizante mais efetivo frente aos isolados testados foi o ácido peracético a 0.5 por cento por 15 minutos, reforçando a necessidade de monitorar também a efetividade de produtos sanitizantes frente aos isolados de Salmonella spp.

The aim of this study was to evaluate the antimicrobial sensitivity and efficacy of three sanitizers against Salmonella spp. isolated from carcasses in swine slaughterhouse. Thirty nine of 120 samples were positive for Salmonella spp. The antimicrobials tested included: penicillin G 10 U, amoxicillin + clavulanic acid 30mcg, ampicillin 10mcg, chloramphenicol 30mcg, tetracycline 30mcg, streptomycin 10mcg, gentamicin 10mcg, neomycin 30mcg, enrofloxacin 5mcg, sulfazotrim 25mcg, sulfonamide 300mcg and trimetropim 5mcg. In the tests with sanitizers were used chlorhexidine, quaternary ammonia and peracetic acid, which were put in contact intervals of 1, 5, 10 and 15 minutes. Antimicrobial resistance was observed using penicillin (100 percent), tetracycline (94.9 percent), trimetropim (89.7 percent), and ampicillin (87.2 percent). None of the antimicrobials was 100 percent effective against the samples tested. Amoxicillin + clavulanic acid (86.7 percent), neomycin (86.7 percent) and chloramphenicol (64.1 percent) showed better antimicrobial action. In tests of efficacy of sanitizers, 0.5 percent peracetic acid was effective at 10 minutes (94.6 percent) and 15 minutes (97.3 percent) of contact; 1 percent quaternary ammonia at 10 minutes (89.2 percent) and 15 minutes (97.3 percent) and 0.5 percent chlorhexidine at 10 minutes (70.3 percent) and 15 minutes (72.8 percent). All samples tested were multidrug resistance and six (15.3 percent) showed resistance to ampicillin, chloramphenicol, streptomycin, sulfonamide and tetracycline (ACSSuT group) indicating the need to monitor the spread of antimicrobial resistance of Salmonella spp. isolated from swine. The most effective sanitizing against the bacteria tested was 0.5 percent peracetic acid per 15 minutes, reinforcing the need to monitor the effectiveness of products sanitizers against Salmonella spp.

Caracterização de mecanismos de resistência as quinolonas e sulfametoxazol/trimetoprima de isolados clínicos de Stenotrophomonas maltophilia / Characterization of mechanisms of resistance to quinolones and sulfamethoxazole/trimethoprim in clinical isolates of Stenotrophomonas maltophilia

Stenotrophomonas maltophilia é um bacilo Gram-negativo, não fermentador, considerado um microorganismo pouco virulento, relacionado principalmente a infecções associadas à assistência a saúde. A S. maltophilia apresenta um padrão de resistência intrínseca à maioria das classes de antibióticos. A droga de escolha para o tratamento das infecções por S. maltophilia é a sulfametoxazol/ trimetoprima (SMX/TMP). Entretanto, estudos atuais relatam o aumento da resistência a esse antibiótico, o que limita assim as opções para terapia efetiva. Outras opções de tratamento são o levofloxacino e a tigeciclina, porém, faltam estudos clínicos e in vitro dessas drogas. A proposta deste estudo foi avaliar os possíveis mecanismos de resistência a SMX/TMP e as quinolonas em isolados clínicos de pacientes internados no Instituto Central do Hospital das Clínicas e do Hospital A.C. Camargo. Foram avaliadas 106 amostras de S. maltophilia isoladas de pacientes adultos com infecção relacionada à assistência a saúde, internados no Instituto Central do Hospital das Clínicas da FMUSP e no Hospital de Câncer A.C Camargo durante o período de dezembro de 2008 a dezembro de 2010. A sensibilidade à SMX/TMP foi de 78,3%, para levofloxacino de 82% e 14,2% para cirpofloxacino, para minociclina de 100% e tigeciclina 91,6%. Foi realizado PCR para detecção dos genes sul1, sul2 e dfrA1 para avaliar a resistência à SMX/TMP, os genes int1 e iscr2 para avaliação da presença de elementos genéticos móveis e os genes gyrA, qnr, smeD, smeT e aac(6)-Ib-cr para avaliação da resistência as quinolonas. Quatorze amostras (13,2%) foram positivas para o gene sul1. Desses isolados, nove amostras apresentavam resistência ao SMX/TMP com CIM50 de 8 g/mL e CIM90 de 128 g/mL. Cinco amostras positivas para o gene sul1 foram sensíveis a SMX/TMP com CIM50 de 1 g/mL e CIM90 de 1 g/mL. A sequencia do integron1 da amostra com CIM >125 g/mL mostrou um tamanho aproximado de 4000 pb contendo os genes cassetes aac4 e aadA1 e...

Stenotrophomonas maltophilia is a gram-negative, non-fermenter, considered a low virulent organism, mainly related to healthcare associated infections. S. maltophilia shows a pattern of intrinsic resistance to many classes of antibiotics. The drug of choice for the treatment of infections caused by S. maltophilia is SMX/TMP, however, current studies have reported increased resistance to this antibiotic, thus limiting the options for effective therapy. Among the treatment options appear tigecycline and levofloxacin, but clinical trials and studies in vitro to such drugs are lacking. The purpose of this study was to evaluate the possible mechanisms of resistance to SMX/TMP and quinolones in clinical isolates from patients admitted to the Institute's Central Clinical Hospital and the Hospital A.C Camargo. We evaluated 106 strains of S. maltophilia isolated from adult patients with healthcare associated infections, at the Instituto Central do Hospital das Clínicas and the Cancer Hospital AC Camargo in the period of December 2008 to December 2010. The sensitivity to SMX/TMP was 78.3%, 82% for levofloxacin, 14,2% for ciprofloxacin, minocycline 100% and for tigecycline 91.6%. PCR was performed for detection of gene sul1, sul2 and dfrA1 to evaluate the resistance to SMX/TMP, genes iscr2 int1 was performed to evaluate the presence of mobile genetic elements and genes gyrA, qnr, smeD , smeT and aac (6 ')-Ib-cr for evaluation of resistance to quinolones. Fourteen samples (13.2%) were positive for the gene sul1. In these isolates, nine samples showed resistance to SMX/TMP with MIC50 of 8 g/ml and MIC90 of 128 g/mL. Five strains were positive for sul1 gene and were susceptible to SMX/TMP with MIC50 of 1 g/ml and MIC90 of 1 g/mL. The sequence of the integron class 1 strain with an MIC> 125 g/mL showed an approximate size of 4000 bp containing the gene cassettes aadA1, aac4 and qac/sul1. A strain resistant to SMX/TMP was positive for the gene sul2 located on ISCR2 a...

Antibacterial susceptibility of uropathogens in 3 hospitals, Sari, Islamic Republic of Iran, 2002-2003

To determine the frequency and pattern of antibiotic susceptibility of uropathogens in urinary tract infection [UTI] from 3 university hospitals we carried out a retrospective review of urine culture and antibiotic sensitivity testing from symptomatic outpatients and inpatients during 2002-2003. Of 5600 samples, 703 [12.6%] were culture positive, 38.7% of which were from hospitalized patients. Escherichia coli was the leading cause of UTI in both groups of patients. The rates and roles of other pathogens, including Pseudomonas spp. [5.3%-10.4%], Enterobacter spp. [0%-5.7%], Staphylococcus spp.] 5.4%-26.4%], differed in each hospital. Differences in antibacterial susceptibility patterns were observed. Ampicillin [82%-100%] and co-trimoxazole [50%-90%] resistance were the most frequent. Methicillin resistance in Staphylococcus spp. ranged from 17% to 60%

Increased isolation of Vibrio cholerae O1 serotype Inaba over serotype Ogawa in Pakistan

Although the predominant Vibrio cholerae serotype in Pakistan is Ogawa and serotype Inaba is rare, there has been a significant increase in the isolation of Inaba in our referral laboratory in Karachi. This paper reports this observation and further analysis of previous cholera data from 1993 to 2005 to assess the trend of occurrence and resistance pattern of V. cholerae strains. From January to September 2005, 245/3292 [7.4%] specimens yielded growth of V. cholerae. Of these, 243 were serotype Inaba, outnumbering serotype Ogawa. This recent Inaba strain is 100% resistant to cotrimoxazole, 3% resistant to chloramphenicol and not resistant to ampicillin, tetracycline and ofloxacin. This sensitivity pattern is almost similar to that of the previous predominant serotype Ogawa

Antibiotic sensitivity pattern of staphylococcus aureus in Abakaliki, Nigeria

To investigate the sensitivity pattern of Staphylococcus aureus isolates obtained from clinical specimens including urine, wound, high vaginal swab and semen to commonly used antibiotics. The susceptibility patterns of these isolates were determined using the disc diffusion and agar well diffusion methods. Out of 174 samples, 51 [29.2%] yielded S. aureus with the highest isolation from semen [66.7%] and the least from urine [15.6%]. Following the disc diffusion, the highest sensitivity was recorded for Ofloxacin [65%] while the least was for Co-trimoxazole [6%]. Amoxicillin, Ampicillin, Tetracycline and Cloxacillin recorded 37%, 19%, 8% and 11% respectively. Also, following the agar well diffusion method, the highest sensitivity was recorded for Ofloxacin [65%] and the least for Co-trimoxazole [8%]. The other drugs recorded the following readings; Amoxycillin [37%], Ampicillin [21%], Tetracycline [23%] and Cloxacillin [13%]. The study recommends the use of Ofloxacin in the treatment of S. aureus infections in the study area. It also underscores the need for sensitivity testing before the administration of antibiotics for the treatment of Staphylococcal infections

Antimicrobial resistance trends in shigella species among patients with acute diarrhea

Infections due to Shigella spp. cause substantial morbidity worldwide. The possibility that shigella strains develop resistance to antimicrobial drugs necessitates a continuous program to determine the sensitivity. The study was carried out to determine the pattern of antimicrobial resistance of shigella species among patients with acute diarrhea. Antimicrobial resistance patterns of shigella strains isolated from children with acute diarrhea were studied during 2002-2004 in Children Hospital of Tabriz. Iran. A total of 43 isolalted shigella strains, Shigella flexneri [39 cases] was the most prevalent species, followed by shigella sonnei [4 cases]. The Shigella flexneri isolates were highly resistant to ampicilin [89.6%] and trimetoprim - sulfamethoxzol [89.1%]. Multidrug resistance were in 67.8% cases. Almost all Shigella sonnie exhibited resistance to ampicilin and 75% to trimetoprim-sulfamethoxazol. All isolates were suseptible to third generation cephalosporins and nalidixic acid. Suseptibility to gentamicin, amikacin and chloramphenicole was observed in 89.8%, 82.5% and 69% respectively. These results suggest the shigella flexneri is the important species in this region with high resistance to commonly used antibiotics [Ampicilin, Cotrimoxazol]. Therefore its better to prevent unnecessary usage of antibiotic in children diarrhea to avoid more bacterial resistance

Diarreas asociadas a Shigella con un patrón de resistencia antimicrobiana alto en el cantón de Coto Brus, Costa Rica / Associated diarrhea to Shigella with high pattern of antimicrobial resistance in the Cantón de Coto Brus, Costa Rica

Se analizaron 420 muestras diarreicas de pacientes admitidos en el Hospital San Vito, Puntarenas; Costa Rica durante enero del 2001 a enero del 2002 y se determinó el porcentaje de resistencia de Shigella sp a 8 antibióticos de primera línea. El 65.1 por ciento de las cepas se aislaron durante los meses de octubre a diciembre del 2001. Se aislaron 142 cepas de Shigella flexneri y 6 de Shigella sonnei. El 70 por ciento mostraron resistencia Trimetoprin-Sulfametoxazole, tetraciclina y ampicilina, siendo todas las cepas sensibles a la gentamicina, cefotaxima y ciprofloxacina. El estudio mostró que la mayoría de las cepas aisladas presentaron una alta resistencia a los antibióticos comúnmente utilizados en el tratamiento de las enfermedades diarreicas. Por lo tanto, se recomienda un monitoreo continuo de los patrones de resistencia para un subsecuente tratamiento.

Molecular Genetic Characteristics of Trimethoprim Resistance in Clinical and Normal Fecal Isolates of Escherichia coli

One hundred and thirty trimethoprim-resistant R plasmids derived from of Escherichia coli isolated from clinical specimens and feces of healthy collegians were examined for incompatibility, EcoRI endonuclease restriction fragment pattern, and Southern hybridization with DHFR I, II, III, V, and VII probe. 1. Most trimethoprim-resistant R plasmids were resistant to ampicillin, tetracycline, chloramphenicol, gentamicin, and kanamycin, and showed multiple drug resistance and various antimicrobial resistance patterns. 2. Trimethoprim-resistant R plasmids ranged from 90 to 50 kilobase and 42.3% of R plasmids tested were classified to incompatibilty group Inc FI, Inc FII or Inc FIV, 3. Among 48 random selected R plasmids from various origin, 14 R plasmids (including 9 of 14 Inc FII plasmids and 3 of 14 Inc FI plasmids) hybridized with DHFR VII oligonucleotide probe but others did not respond to any of DHFR probes used. 4. Most R plasmids showed various EcoRI endonuclease fragments and different reaction sites by Southern hybridization. Six plasmids showed identical or nearly identical molecular weight, EcoRI endonuclease fragment patterns and different sites of Southern hybridization. But 2 Inc FII plasmids derived from urine and feces showed identical pattern. These findings, if confirmed by further studies, suggest that normal flora E. coli can act as reservoir of resistant genes and, consequently, as a factor in the dissemination of these genes among enteric pathogens and need to be examined further.

Epidemiology of Serratia marcescens Isolates by Transferable Resistance Gene Analysis

Conjugative R plasmids derived from 74 clinical isolates of Serratia marcescens were epidemiologically analyzed for antimicrobial resistance, EcoRI restriction endonuclease analysis and Southern hybridization with DHFR, TEM and SHV probe. 1. Resistance frequency of isolates against various B-lactam antibiotics was changed by year. 2. Twenty (27%) resistant strains transferred 32 R plasmids to E. coli or Klebsiella by mixed culture. Most strains isolated from 1994 to 1996 transferred only trimethoprim resistance but most strains isolated from 1997 did resistances against gentamicin (Gm) and B-lactams including ampicillin (Ap), carbenicillin (Cb), cefazolin (Cz), cefaloridine (Cl), cefamandole (Cn). 3. Ten plasmids of GmApCbCzC1Cn or GmApCbCzC1 pattern and 3 plasmids of TcSuGmTbApCbCzC1 pattern respectively showed identical EcoRI restriction endonuclease digestion patterns and hybridized fragment patterns with TEM-1 probe by Southern hybridization. These results indicate that the epidemic plasmids carrying blamM gene were present in this hospital in 1997 and molecular genetic analysis of R plasmids can be used to discriminate S. marcescens isolates for epidemiologic studies.

Transferable Trimethoprim Resistance in Urine Isolates of Escherichia coli

One hundred and twenty-two strains of E. coli isolated from urinary tract infection were examined for antibiogram, transferability of trimethoprim (Tp) resistance, incompatibility with F group plasmid and southem hybridization with DHFR I, II, and III probe of Tp-resistant R plasmids. 1. Among 172 Gram negative bacilli isolated from urinary tract infection, 122 (70.9%) were E. coli and 75 strains of them were resistant to trimethoprim (Tp). Most of Tp-resistant isolates were also resistant to penicillins (ampicillin, carbenicillin, and ticarcillin), aminoglycosides (kanamycin and gentamicin), and sulfisoxazole but almost all strains were susceptible to cephalosporins. 2. Most of Tp-resistant strains and E. coli transconjugant derived from them showed multiple drug resistance and various antimicrobial resistance patterns. 3. Thirty-three Tp-resistant strains (45.2%) transferred 35 Tp-resistant plasmids to E. coli recipients but among them 6 transconjugants did not show retransfer of resistance and plasmid DNA were not detected in 2 transconjugants after resistance transfer. 4. Tp-resistant R plasmids ranged from 157 to 67 kb and 8 R plasmids were classified to incompatibilty group IncFI or IncFII ranging from 120 to 83 kb. Three and two R plasmids belonged to IncFII showed similar molecular weight, resistance pattern, and reaction site by southern hybridization with DHFR I probe. Twenty-five plasmids specifically responded on various EcoRI endonuclease fragments to DHFR I probe but not to DHFR II or DHFR III probe. These findings suggest that most of Tp- resistant R plasmids from urine isolates of E. coli were derived from various sources but some plasmids including IncFII R plasmids were probably originated from same or similar sources.

Sensibilidad actual a los antibióticos de las bacterias aisladas en el Hospital Escuela / Actual Sensibility of Bacterial Resistence at the Hospital Escuela. Tegucigalpa

Objetivo: Conocer la evolución de la resistenciabacteriana a los antibióticos del Hospital-Escuela. Diseño: descriptivo, restrospectivo. Método: Análisis deel cultivo-antibiograma de orina, exudados y sangre en el Laboratorio de Bacteriología. Comparamos estos resultados con los obtenidos en 1988. Resultados: Se estudiaron 4.535 muestras;58.2% eran orina, 35.3% exudados, 6.4% sangre. Se aislaron 6.544 bacterias Gram negativo, la más común Escherichia coli. Observamos disminución de sensibilidad de bacilos Gram negativo a amikacinade un 13.7%. La resistencia de estos microorganismos a ampicilina es de 74%

Multidrug resistant typhoid fever: therapeutic considerations.

Forty six blood culture positive cases were studied during the current outbreak of multidrug resistant typhoid fever (MRTF). The present outbreak was caused by E1 phage type and organisms were resistant to all commonly used drugs for the treatment of typhoid fever, viz., chloramphenicol (78%), co-trimoxazole (76%) and ampicillin (68%). Treatment failures with chloramphenicol (45.5%) corroborated well with in vitro resistance. No treatment failure was seen with chloramphenicol and ceftriaxone, when these drugs were used in cases infected with sensitive strains. Among the alternative drugs used in cases with in vitro sensitivity, successful clinical response was seen with ceftriaxone (4/4) and cefotaxime (8/9) as compared to cephalexin (3/5) or a combination of cephalexin and furazolidone (9/12).

Multi drug resistant Salmonella typhi infection: clinical profile and therapy.

Multiple drug resistant Salmonella typhi infection was observed in thirty five recent cases among forty eight children with bacteriologically proven enteric fever. Incidence of complications such as shock, myocarditis, encephalopathy and paralytic ileus was higher among these. A combination of cephalexin and gentamicin was successfully used in the management of these children.

Epidemiological study of sulfonamide and trimethoprim resistance genes in Enterobacteriaceae.

Sulfonamide (Su) and trimethoprim (Tp) resistance are known to caused by the production of drug resistant dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR), respectively. Sulfonamide and trimethoprim are often used in combination under the name cotrimoxazole. Cotrimoxazole resistance in various enteric bacteria isolated at Ramathibodi Hospital was studied. The rate of resistance from 1984-1989 of many genera was rather constant at 40%-60% except in Shigella spp in which the rate increased rapidly in 1987 till 1989. Seventy-five percent of Su-Tp resistant (Sur-Tpr) bacteria were also found to be resistant to other drugs such as ampicillin, aminoglycosides, tetracycline and chloramphenicol in addition to cotrimoxazole. Two hundred and forty Su-Tp resistant strains were analysed for the presence of type I and II dihydropteroate synthase as well as type I and V dihydrofolate reductase genes by hybridization with the corresponding gene probes. Type I DHPS gene predominated in Su-Tp resistant bacteria at 60.8% whereas type II DHPS was found in only 25%. Some strains (11.7%) had both genotypes but 2.5% did not have any. In the trimethoprim resistance study, the DHFR type I gene was also found more frequently (30%) whereas type V DHFR was only 19%. The remaining of Tp resistance (51%) was unclassified. The coexistence of Su and Tp resistance genes of each type was investigated among 118 Su and Tp resistant strains. It was found that type I DHPS gene was found together with either type I or V DHFR gene and type II DHPS was found with type I DHFR gene at about the same rate (28.9%, 27.1% and 26.3%, respectively). However, the presence of type II DHPS together with type V DHFR was rather low, only 5.9% of isolates were found to have both types of genes.