Pertussis is a serious respiratory disease in infants that can also affect children and adults. Vaccination against pertussis was introduced in the 1950s and in the 1990s a resurgence of pertussis was observed worldwide. The aim of this work is to summarize the recent data concerning pertussis disease in different countries of Latin America. In this geographic region, pertussis is nationally notifiable and cases should be reported to the appropriate health department/Ministry. Though the surveillance systems are not the same among Latin America countries, over recent decades an increasing number of cases have been detected. Most of these cases correspond to patients younger than 6 months old who received fewer than three doses of vaccine. However, cases in adolescent and adults have also been detected. For this situation, which is not peculiar to Latin America countries, several explanations have been proposed.

The use of RT-PCR permits improved detection and diagnosis of pertussis and a better understanding of the epidemiology of sources of infection. The complications and mortality rate of pertussis continue to be high. Household contacts are confirmed as a frequent source of infection of B pertussis in young children.

The aim of this study was to identify the presence of group CTX-M-9 extended spectrum beta-lactamases (ESBL) in clinical Escherichia coli isolates from pediatric patients. A total of 404 non-repeated positive ESBL E. coli isolates were collected from documented clinical infections in pediatric patients over a 2-year period. The identification and susceptibility profiles were determined using an automated system. Isolates that suggested ESBL production based on their resistance profiles to third and fourth generation cephalosporin and monobactam were selected. ESBL production was phenotypically confirmed using a diffusion method with cefotaxime and ceftazidime discs alone and in combination with clavulanic acid. blaESBL gene identification was performed through PCR amplification and sequencing. Pulsed Field Gel Electrophoresis (PFGE) and Multilocus Sequence Typing (MLST) were performed to establish the clonal relationships of the E. coli isolates. CTX-M-9-type ESBLs were detected in 2.5% of the isolates. The subtypes corresponded to blaCTX-M-14 (n = 4) and blaCTX-M-27 (n = 6). Additionally, coexistence with other beta-lactamases was observed. A clonal relationship was established in three isolates; the rest were classified as non-related. We found seven different sequence type (ST) in CTX-M-9- producing E. coli isolates. ST38 was the most frequent. This study is the first report in Mexico to document the presence of group CTX-M-9 ESBLs in E. coli isolates from pediatric patients.

Purpose Staphylococcus aureus is one of the main causative agents of hospital-acquired (HA) infections. In Mexico, information about the characteristics of clinical S. aureus isolates is limited. Our aim was to characterize S. aureus strains obtained from blood cultures of paediatric patients treated in a tertiary care hospital. Materials and Methods We analysed 249 S. aureus isolates over the period from 2006 to 2019, and their resistance profiles were determined. The isolates were classified into methicillin-resistant S. aureus (MRSA) or methicillin-sensitive S. aureus (MSSA). Staphylococcal cassettes chromosome mec (SCC mec ) were detected. Virulence genes ( cna, clfA, clfB, eta, etb, fnbA, fnbB, hla, pvl, sec, and tsst ) were amplified, and their clonal relationships were established by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and clonal complex (CC) typing. We reviewed one hundred medical files to collect clinical information. Results Thirty-eight percent of the isolates were MRSA and showed an expanded profile of resistance to other non-beta-lactam antibiotics, while MSSA strains presented a reduced resistance profile. SCC mec- II was the most frequent element (86.3%). Eight virulence factors were detected in MSSA and six in MRSA. The pvl gene was detected in four MRSA-SCC mec- IV isolates ( P ≤0.0001). MRSA isolates were distributed among 14 clones and were classified into 15 sequence types (ST); the most frequent was ST1011 (17%). The most common CC in MRSA was CC5 (69%, P ≤0.0001), and in MSSA, it was CC30 (30%, P ≤0.0001). Eighty-seven percent of MRSA isolates were HA-MRSA, and 13% were community-acquired MRSA (CA-MRSA). Of 21 HA-MRSA isolates, 17 had SCC mec -II, while two CA-MRSA isolates had SCC mec -IV. Of MSSA isolates, 77% were derived from HA infections and 23% from CA infections. Conclusion MSSA isolates had more virulence factors. MRSA isolates were resistant to more non-beta-lactam antibiotics, and those with SCC mec -IV expressed a greater variety of virulence factors. Most S. aureus isolates belonged to CC5.

Pediatric oncology and hematology patients are at increased risk of developing healthcare associated infections (HAIs). We conducted a prospective surveillance study on children with cancer admitted to the pediatric hematology and oncology units at a public pediatric hospital in Mexico from January 2004 to December 2009. The incidence of HAIs and groups at greatest risk for HAIs were analyzed. The annual HAI incidence rate and incidence density were calculated. Risk factors such as site of infection, HAI types, and cancer diagnosis were studied. A total of 9420 patients participated, and 409 had HAIs (479 episodes). Annual HAI rates were 3.7 to 5.5 per 100 admissions and the incidence density was 5.75 to 6 HAIs per 1000 inpatient days annually. There were 272 (56.8%) bloodstream infections, 45 (9.4%) pneumonia cases, and 44 (9.2%) skin and soft tissue infections. Children with acute lymphoblastic leukemia had 37.2% and those with acute myeloid leukemia had 16.4% of the HAIs. A total of 11.5% of the HAIs were in children with osteosarcoma. The most common pathogens were Gram-negative bacteria. The HAI-associated mortality rate was 3.7%. Although the overall HAI rate is in line with published reports, the mortality rate was higher, suggesting the incorporation of more aggressive methods to treat infections at our hospital.

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Background S. aureus is the most common cause of osteomyelitis in children. Panton-Valentine leucocidin (PVL) is an exotoxin produced by certain S. aureus strains, which can be detected in both methicillin-sensitive and -resistant strains of staphylococci. Pediatric osteomyelitis by PVL producing S. aureus constitute a rare, but highly critical event. They are characterized by a rapid course of marked inflammation, worsening under conservative therapy, and a high rate of recurrence. No information is available on osteomyelitis and Panton-Valentine leukocidin producing S. aureus in Mexico. Objective The aim of this study was to determine the molecular characterization of S. aureus strains isolated in pediatric patients with osteomyelitis and their clinical features in a tertiary hospital in Mexico City. Methods We conducted a prospective study of children admitted for osteomyelitis, between December 2018 and November 2019, at Instituto Nacional de Pediatría. We obtained an informed consent in children under 12 years of age and an informed assent in children over 12. The confirmation of the S. aureus isolates was performed by amplification and analysis of 16S rRNA and nuc genes. The mecA and pvl genes were detected by PCR, the clinical features were obtained at the admission. Results Fifty patients were included and 26 cases of osteomyelitis were diagnosed, 13 were due to staphylococcus aureus genus and 6 due to S. aureus; all of them were methicillin susceptible and two were PVL producers. Both patients had a severe initial presentation, with extensive local abscesses, and one required three surgical procedures and developed septic pulmonary embolism. The two patients received double antimicrobial treatment and required a long therapy interval. Conclusions Osteomyelitis with Panton-Valentine Leukocidin producing S. aureus seems to be more severe. In patients with severe osteomyelitis, it is essential to detect the PVL toxin because they require early surgical intervention and prolonged intravenous therapy. Our findings suggest that the severity of the osteomyelitis is linked with PVL production more than with methicillin resistance due to that all our isolates were methicillin susceptible.