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Locally prevalent pathogenic bacteria 189 Gram (-) and 135 Gram (+) strains, all isolated from pediatric patients severely infected, were tested in vitro against 11 essential oils from commercial origin. All the strains showed resistance to selected antibiotics. Cinnamomum verum, Origanum vulgare and Thymus vulgaris exhibited the highest and broadest antibacterial activity. Emphasis is made in the potential implications of these resources, uncommon at the clinical setting of the study, employed against non-commercial, locally pathogenic strains, being a step to submit in the ensuing period essential oils from plants used in Mexican traditional medicine.

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BACKGROUND: Pseudomonas aeruginosa is a common cause of nosocomial infections, particularly in intensive care units (ICUs). The aim of this study was to characterize P. aeruginosa clinical isolates by comparing antimicrobial susceptibility patterns with the presence of plasmids and to establish the clonal relatedness by pulsed-field gel electrophoresis (PFGE) typing. METHODS: The patients included those with isolation of P. aeruginosa hospitalized for more than 48 h in the ICU from April to May 1998. Environmental and staff cultures were obtained simultaneously. Minimal inhibitory concentrations, plasmid DNA profiles, and PFGE genomic patterns of enzyme restriction chromosomal DNA were compared. RESULTS: Sixty P. aeruginosa isolates were obtained from 197 clinical specimens, 178 environmental samples, and 47 hand cultures of personnel. Antimicrobial resistance was as follows: tobramycin 100%; ticarcillin, cefotaxime, ceftriaxone, ceftazidime, and gentamicin 80%; cefepime 60%; amikacin, ticarcillin/clavulanate, imipenem, and meropenem 40%; piperacillin and norfloxacin 20%; carbenicillin 12%, and ciprofloxacin 0%. Plasmids were detected in 11 isolates (18%). PFGE typing showed that 23 isolates belonged to a common clone (pattern A), identified from five patients, two nurses, and 10 environmental samples. Ten isolates were grouped in four clusters and 27 isolates had unrelated genomic patterns. There was no relationship among DNA genomic patterns, plasmid profiles, and susceptibility patterns. CONCLUSIONS: PFGE demonstrated the existence of a common clone in a critical care area. Reinforcement of infection control measures is needed to avoid horizontal transmission and severe infections.

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OBJECTIVE: To determine the prevalence of upper respiratory tract colonization by Moraxella catarrhalis in children under six years of age. MATERIAL AND METHODS: A survey was conducted between January and December 1998 in Mexico City, among children aged 2 months to 5 years, selected through cluster sampling. Pharyngeal samples were taken for M. catarrhalis identification. The minimal inhibitory concentration to different antibiotics was obtained and beta-lactamases were determined by the iodometric test. Statistical analysis consisted of frequency distributions, odds ratios, 95% confidence intervals, and Mantel-Haenszel chi 2. Statistical significance was set at p < 0.05. RESULTS: After excluding 37 children, the study population was 604 children from Mexico City; M. catarrhalis was present in 130 pharyngeal specimens (22.9%). Most of the strains were positive for beta-lactamase production (75.4%). Eighty percent of the strains was resistant to penicillin and 70% to ampicillin and amoxicillin. None were resistant to cefotaxime, imipenem, meropenem and erythromycin. CONCLUSIONS: Prevalence of M. catarrhalis upper respiratory tract colonization is similar to that of other respiratory pathogens. These findings warrant future research on the role of M. catarrhalis as an etiologic agent in acute and chronic respiratory infections in Mexico.

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UNLABELLED: Cryptosporidium parvum is associated with diarrheic disease and mainly affects children and immunocompromised hosts. In most of the cases, cryptosporidiosis infection is asymptomatic in immunocompetent subjects. The objectives of the study were to determine the frequency of asymptomatic infection caused by the parasite in children with and without malnutrition and to determine the risk factors associated to infection. METHODS: Children from one to fifteen years old without diarrhea were included, somatometry were performed. The socioeconomic and sanitary conditions were investigated for each family and community. The Faust method and Kinyoun stain were employed identify parasites and Cryptosporidium parvum in feces. Odds ratio (OR), 95% confidence intervals (75% CI), chi 2 Mantel-Haenszel, Fisher exact test and chi 2 trends were calculated. RESULTS: One hundred thirty two children were included. In 10/132 (7.5%) cysts of Cryptosporidium were found, 7/71 in children with malnutrition (9.8%) and 3/61 without malnutrition (4.9%) p = 0.23. 69.7% of the children had parasitosis. According to the presence of C. parvum in feces, the different factors calculated were: Diarrhea in family OR = 5.82 (95%IC 0.86-39.18), not hand washing OR = 5.08 (95%IC 0.62-110.49), age less than 5 years old OR = 4.90 (95%IC 0.60-106.9), drinking non-potable water OR = 3.34 (95%IC 0.40-73.01) and malnutrition 2.11 (95%IC 0.46-10.89). Association was found between the number of people in the same house and the risk of infection (p = 0.005). The presence of diarrhea in the family (OR = 4.15, 95%IC 0.47-36.91) and drinking non-potable water (OR = 4.19, 95%IC 0.48-36.32) were the significant factors in the regression logistic model. CONCLUSIONS: The frequency of Cryptosporidium infection were 7.5%. Diarrhea in the family, overcrowding and drinking non-potable water were associated with C. parvum infection, malnutrition was not a significant risk factor.

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Even though the incidence of pneumonia in developed and developing countries is similar, the mortality is five times higher in developing countries. This study aimed to determine the prevalence of bacteremia in children with acute lower respiratory tract infection (LRTI) and relative contribution of respiratory syncytial virus (RSV). One hundred and one children under five years of age who attended a primary care level clinic with diagnosis of acute LRTI, were enrolled. Diagnosis and management of pneumonia were done according to the WHO guidelines. Two blood cultures were drawn at the time of admission. A nasopharyngeal sample was taken for detection of RSV by indirect immunofluorescence. Blood cultures were positive for pathogenic bacteria (Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus) in three patients. The detection for RSV was positive in 24 patients (23.7%). The clinical and radiographic presentations were not significantly different between patients with and without RSV (p > 0.05). RSV is a common cause of LRTI in children younger than five years old. Blood cultures are not commonly positive in outpatients with acute LRTI. The practice of obtaining blood cultures in primary and secondary care clinics is not useful to guide the treatment of patients with community-acquired pneumonia.

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OBJECTIVE: To analyze an outbreak of Serratia marcescens in a neonatal intensive care unit and identify the risk factors associated to the development of infection. MATERIAL AND METHODS: It was a case-control study from March to July 1995. Factors included were age, sex, intravascular devices, nebulizers, mechanical ventilation, use of total parenteral nutrition (TPN), underlying diseases, surgical interventions, tubes, previous antimicrobial treatment and days of exposure. The associations were explored using the odds ratio. RESULTS: 24 cases and 30 controls were included. In the univariate analysis the significant risk factors (OR,IC) were use of central venous catheter (4.57, 1.01-23.5), days of use of TPN (4.38, 1.03-16.5), days of previous antimicrobial treatment (4.87, 1.60-22) and days of exposure (2.7, 2.65-27.6). In the multivariate analysis the significant risk factors were previous antimicrobial treatment (3.98, 2.36-18.2), days of previous antimicrobial treatment (6.76, 3.02-24.6) and days of use of TPN (4.87, 1.67-15.6). CONCLUSIONS: The significant risk factors in our study were previous antimicrobial treatment, days of antimicrobial and days of use of TPN.

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The aim of this study was to evaluate the utility of a volume-modified blood culture system to diagnose bacteremia in newborns and infants. A total of 793 paired blood cultures, obtained from 464 patients (173 newborns and 291 infants), were analyzed. Vacutainer tubes containing 18 ml supplemented peptone broth sodium-polyanethol-sulfonate were used as the gold standard, in comparison with a blood micro-culture system containing 1.8 ml of the broth. Prior to antibiotic treatment, 2.2 ml of blood was obtained from each patient; 0.2 ml was inoculated in a blood micro-culture tube and 2 ml in a routine tube. Sensitivity, specificity and predictive values were calculated. Microorganisms were isolated in 153 standard blood culture tubes and 151 blood micro-culture tubes. The sensitivity of the blood micro-culture system was 95%, specificity 99% and positive and negative predictive values 96% and 99% respectively. The sensitivity and specificity of blood micro-culture in neonates and infants is high. We recommend that this system be used for the diagnosis of bacteremia in newborns and infants in laboratories where manual systems are still in use.

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Due to the changes in the frequency of penicillin-resistant strains of S. pneumoniae, it is necessary to perform surveillance studies of bacterial resistance. Isolates from the upper respiratory tract of asymptomatic children have been useful. There is no information about the difference between isolates from children with and without upper respiratory tract infection (URTI). The objective of the authors in this paper is to establish the prevalence of carrier-state, serotype and antimicrobial resistance of S. pneumoniae isolates from children with and without acute upper respiratory tract infection (URTI) in a rural area in Mexico. A cross-sectional comparative study was performed in Tlaxcala, Mexico. Children from one month 5 years of age were included. Nasopharyngeal swabs were obtained. Identification was done by international microbiology standards. Serotyping was done by the capsular Quellung test. The susceptibility testing was performed by the agar dilution method. Four-hundred and fifty patients were included. S. pneumoniae was isolated in 134 children (29.7%). Frequency of carriers was greater in patients with URTI (107/323) than without URTI (27/127) (33.1% vs. 21.1% p = 0.012, OR 1.84, IC 95% 1.1-3.08). The six most frequent serotypes were: 6B (16.4%); 19F (11.9%); 19A (6.7%); 14, 23F, and 35 (5.2% each), with no difference among the groups. Only 3% of the strains had high level resistance to penicillin, and 12.6% had intermediate resistance, and for ampicillin 4%, amoxicillin 4%, amoxicillin-clavulanate 4%, ceftriaxone 3%, cefotaxime 1.5%, erythromycin 6%, miocamycin 3%, chloramphenicol 4%, and vancomycin 0%. Trimethoprim-sulfamethoxazole resistance was very high (42%). In conclusion, colonization is higher in children with URTI. Five of the most frequent serotypes identified in this study were the same as those identified in patients with S. pneumoniae invasive diseases in Mexico City. In Tlaxcala, Mexico, beta-lactams could be the drug of choice for the treatment of S. pneumoniae lower respiratory tract infections. It is necessary to perform clinical assays to evaluate the efficacy of trimethoprim-sulfamethoxazole due to the high resistance in vitro.

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